Dissertations / Theses on the topic 'Nanostructured hybrid material'

Mesoporous nanostructured materials are useful for a widespread field of applications, such as gas storage; selective molecular adsorption; confined chemical reactions and catalysis. In this work, periodic mesoporous silica and organosilica materials, thanks to their high surface area, narrow pore size distribution and high regular structure, have been exploited to obtain nanostructured porous materials with different chemical nature, such as polymer or carbon. Periodic mesoporous silica objects with defined micrometric shape have been obtained by template synthesis in aqueous medium. A change in synthesis condition of temperature, time and acidity leads to the generation of different shapes such as gyroids, spheres and hollow tubes. Mesoporous silica particles have been exploited for confined polymerization of different monomers (styrene, methylmethacrylate and acrylonitrile) to obtain morphological polymeric nanocomposites. The nanocomposite with polyacrylonitrile has been then heated at high temperature in non-oxidative atmosphere to induce polymer carbonization until the formation of a graphitic-like carbon structure. The silica matrix has been then removed by chemical etching to obtain nanostructured porous materials in polymer and graphitic-like carbon with high surface area and the same micrometric morphology of starting silica matrix (shape replica effect). Afterwards, a periodic mesoporous organosilica system, with phenylene groups directly linked in the wall structure and organized on the molecular scale, has been synthesised, exploited as selective gas adsorption system and heated in non-oxidative atmosphere to obtain a new mesoporous carbon material with high surface area, very regular mesoporous structure and graphitic-like pore walls. Characterization of these materials has been conduced with X-ray diffraction, calorimetric techniques (DSC and TGA), adsorption of gases and vapours and advanced mono- and bi-dimensional NMR experiments to investigate the interaction between the organic and the inorganic moieties. Thermal evolutions of polyacrylonitrile and phenylene-organosilica have been studied with spectroscopic techniques of ATR and Raman, while the shape replica effect and the high regular pore structure have been directly seen with SEM and TEM microscopies.

The acid and base catalyzed simultaneous twin polymerization (STP) of various 2,2′-disubstituted 4H-1,3,2-benzodioxasiline derivatives 2a–d with 2,2′-spirobi[4H-1,3,2-benzodioxasiline] (1) are presented in this paper. The products are nanostructured ternary organic–inorganic hybrid materials consisting of a cross-linked organic polymer, silica and a disubstituted polysiloxane. It can be demonstrated whether and in which extent the copolymerization of the two inorganic fragments of 1 and 2 takes place among the STP and how the molar ratio of the two components determines the structure formation of the resulting hybrid material. Steric and electronic effects of the substituents at the silicon center of 2 on the molecular structure formation and the morphology of the resulting hybrid material were investigated by means of solid state CP MAS 29Si and 13C NMR spectroscopy as well as high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The mechanical properties (hardness and Young's modulus) of the hybrid materials were analyzed by means of nanoindentation measurements
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Amino-functionalized organic–inorganic hybrid materials with a narrow distributed nanostructure of 2–4 nm in size were obtained by means of a template-free and non-aqueous procedure. Simultaneous twin polymerization of novel amino group containing twin monomers with 2,2′-spirobi[4H-1,3,2-benzodioxasiline] has been applied for this purpose. The amino groups of the organic–inorganic hybrid material are useful for post derivatization
Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich

Des matériaux hybrides de classe II ont été préparés à partir de précurseurs bis(tripropynylstannylés). Deux familles de précurseurs sol-gel incluant des espaceurs hydrocarbonés et thiophénique ont été obtenues et conduisent à des matériaux hybrides auto-organisés où les plans d’oxyde sont séparés par les espaceurs organiques. Ainsi l’espaceur rigide a donné lieu à une structure pseudo-lamellaire montrant une bande d’émission monomère avec un assez faible décalage vers le rouge par rapport à l'émission des précurseurs en solution. En revanche, alors que les xérogels thiényle plus désordonnés conduisent à une large émission caractéristique de la formation d’excimères ou de dimères. Par ailleurs, des films minces contenant les espaceurs alkylène et arylalkylène ont été préparés et ont montré une morphologie "pseudoparticulaire" poreuse et un ordre à courte distance contenant des réseaux SnOx. De façon inattendue, ces films minces hybrides détectent le dihydrogène dès une température de 50 °C dans la gamme 200-10000 ppm. A partir de ces films hybrides minces, le dioxyde d'étain cristallin (SnO2) a été préparé par un post-traitement thermique. Comme prévu, ces films SnO2 cassitérite détectent le dihydrogène et, dans une moindre mesure le monoxyde de carbone avec une température optimale de fonctionnement comprise entre 300 et 350 °C
Class II hybrid materials were prepared from ditin hexaalkynides. Two families of precursors, including either hydrocarbon or oligothiophene-based spacers, were obtained and led by the sol-gel process to self-assembled organotin-based hybrid materials made of planes of oxide separated by organic bridges. Thus, the rigid thienyl spacer gave rise to a “pseudo-lamellar” structure that showed a monomer emission band with a rather small red-shift compared with to the emission of the precursor in solution. However more disordered thienyl xerogels led to broad emission features assigned to excimer or dimer formation. Moreover, thin films containing alkylene- and arylalkylene bridged have been prepared and showed a “pseudoparticulate” porous morphology and a short-range hierarchical order in the organic-inorganic SnOx pseudoparticles. Unexpectedly these hybrid thin films detect hydrogen gas at a temperature as low as 50 °C at the 200-10000 ppm level. From these hybrid thin films, crystalline tin dioxide (SnO2) were prepared by a thermal post-treatment. As expected, cassiterite SnO2 films detected H2 and to a less extent CO with a best operating temperature comprised between 300 and 350 °C

The overall focus of this thesis is on the development and understanding of nanoporous layered silicates and membranes, particularly for potential applications in gas separations. Nanoporous layered materials are a rapidly growing area of interest, and include materials such as layered zeolites, porous layered oxides, layered aluminophosphates, and porous graphenes. They possess unique transport properties that may be advantageous for membrane and thin film applications. These materials also have very different chemistry from 3-D porous materials due to the existence of a large, chemically active, external surface area. This feature also necessitates the development of innovative strategies to process these materials into membranes and thin films with high performance.

The work presented in this dissertation suggests novel design of chemical plasmonic sensors which have been developed based on Localized Surface Plasmon Resonance (LSPR), and Surface-enhanced Raman scattering (SERS) phenomena. The goal of the study is to understand the SERS phenomena for 3D hybrid (organic/inorganic) templates and to design of the templates for trace-level detection of selected chemical analytes relevant to liquid explosives and hazardous chemicals. The key design criteria for the development of the SERS templates are utilizing selective polymeric nanocoatings within cylindrical nanopores for promoting selective adsorption of chemical analyte molecules, maximizing specific surface area, and optimizing concentration of hot spots with efficient light interaction inside nanochannels. The organic/inorganic hybrid templates are optimized through a comprehensive understanding of the LSPR properties of the gold nanoparticles, gold nanorods, interaction of light with highly porous alumina template, and the choice of physical and chemical attributes of the selective coating. Furthermore, novel method to assemble silver nanoparticles in 3D as the active SERS-active substrate has been demonstrated by uniform, in situ growth of silver nanoparticles from electroless deposited silver seeds excluding any adhesive polymer layer on template. This approach can be the optimal for SERS sensing applications because it is not necessary to separate the Raman bands of the polyelectrolyte binding layer from those of the desired analyte. The fabrication method is an efficient, simple and fast way to assemble nanoparticles into 3D nanostructures. Addressable Raman markers from silver nanowire crossbars with silver nanoparticles are also introduced and studied. Assembly of silver nanowire crossbar structure is achieved by simple, double-step capillary transfer lithography. The on/off SERS properties can be observed on silver nanowire crossbars with silver nanoparticles depending on the exact location and orientation of decorated silver nanoparticles nearby silver nanowire crossbars. As an alternative approach for the template-assisted nanostructure design, porous alumina membrane (PAM) can be utilized as a sacrificial template for the fabrication of the nanotube structure. The study seeks to investigate the design aspects of polymeric/inorganic hybrid nanotube structures with plasmonic properties, which can be dynamically tuned by external stimuli such as pH. This research suggests several different organic/inorganic nanostructure assemblies by various template-assisted techniques. The polymeric/inorganic hybrid nanostructures including SERS property, pH responsive characteristics, and large surface area will enable us to understand and design the novel chemical plasmonic sensors.

The size/shape dependent and unique physical and chemical properties presented by nanostructured materials have attracted great attention in several fields such as energy harvesting, optoelectronics and biomedicine, among others. Even though binary semiconductors have been some of the most studied systems until now, ternary and quaternary semiconductors have started to stand out due to the wide variety of compositions and, as a result, of properties they offer. The importance of hybrid nanomaterials is growing as well: the association of more than one material in the same nanostructure usually allows the preservation or even, the enhancement, of the different properties of the preliminary materials and combines them with the new ones originated from the interaction between the two domains. This thesis is focused on the design of novel compositionally controlled hybrid and ternary nanostructures based on low toxic materials. Firstly, a simple procedure at room temperature is reported for the synthesis of hybrid and ternary nanostructures of Ag-Au-Se and Ag-Au-S. The method consists in the reaction between pre-synthesised Ag2Se/Ag2S nanoparticles (NPs) and a Au(III) precursor. The reaction time, the concentration of gold solution, the surfactant nature and the Ag:Au ratio are the four key parameters that allow the control of the final product. Regarding the Ag-Au-Se system, Au-Ag2Se hybrid nanoparticles (HNPs), Au-Ag3AuSe2 HNPs and Ag3AuSe2 NPs were successfully synthesised. In addition, Au-Ag3AuSe2 HNPs were tested as thermoelectric material, obtaining an improved response in comparison with the binary material (Ag2Se). The potential of Ag3AuSe2 NPs as Computed Tomography contrast agents was also tested, obtaining promising results in this field. Concerning to the analogous system with sulphur, the higher miscibility of Au and S offers a more complex ternary diagram, with two ternary materials with different stoichiometries: Ag3AuS2 and AgAuS. A gradual transformation of Ag2S to Au2S was achievable by the proposed method, with the possibility of isolating Au-Ag2S HNPs, Au-Ag3AuS2 HNPs, Au-AgAuS HNPs, Au-Au2S HNPs and hollow Au2S NPs. Secondly, another ternary system was studied: Ag-Cu-S. Even though this system also presents two different ternary materials (Ag3CuS2 and AgCuS), the direct hot injection method proposed here only allows the formation of the AgCuS stoichiometry. Two different mechanisms are reported, depending on the precursor of copper used in the synthesis. The material was thermoelectrically characterized as well, but without showing a proper performance. Thirdly, four novel nanostructures based on Cu-Pt-Se are described. They were synthesised by a reaction at high temperature between pre-synthesised Cu2-xSe NPs and a Pt(II) precursor. The nanomaterials were thoroughly structurally and morphologically characterized to study the impact of the Pt:Cu ratio in the final product. The larger the amount of platinum in the structure, the more efficient diffusion of the element occurs through the Cu-Se lattice, with the consequent and slow spell of selenium until its totality. Finally, hybrophilic hybrid inorganic-organic nanocomposites formed by inorganic NPs (Au, Ag, Ag3AuSe2 i Au@Fe3O4) and a highly fluorescent low molecular weight Au(I) metallogelator are presented. Their coupling is mainly based on aurophilic/metallophilic interactions between atoms in the surface of the NPs and Au(I) atoms from the complex. Additionally, the Ag and Au nanocomposites were characterized by Raman Spectroscopy. It is well known that when a molecule is strongly coupled to a plasmonic nanoparticle, the intensity of the Raman peaks of the molecule are intensified. This phenomenon is known as Surface-Enhanced Raman Spectroscopy (SERS) and could be observed in both materials. In summary, in this thesis five hybrid and ternary nanostructured systems, based on low toxic materials, have been synthesised, characterized and studied, following the aim of investigate alternative materials, which, in a future, could be applied in energy conversion and biomedicine fields.
En els últims anys, els materials ternaris i híbrids han començat a sorgir gràcies al gran ventall de composicions i, per tant, de propietats que ofereixen i que els donen la possibilitat d’aplicar-se en diversos camps, com ara l’emmagatzematge d’energia, l’optoelectrònica o la biomedicina. Aquesta tesis està centrada en el disseny de noves nanoestructures ternàries i híbrides basades en materials amb una toxicitat baixa. En primer lloc, s’ha descrit un procediment simple a temperatura ambient per la síntesi de nanoestructures ternàries i híbrides d’Ag-Au-Se i d’Ag-Au-S que consisteix en la reacció entre nanopartícules d’Ag2Se i Ag2S sintetitzades prèviament i un precursor d’Au(III). El temps de reacció, la concentració del precursor d’or, la naturalesa del tensioactiu i la relació Ag:Au són els quatre paràmetres clau que permeten el control del producte final. Addicionalment, dos compostos del sistema Ag-Au-Se van ser caracteritzats termoelèctricament i com a agents de contrast en tomografia computada. En segon lloc, s’ha estudiat un altre sistema ternari, format per Ag-Cu-S. El mètode d’injecció en calent proposat en aquesta tesi permet la formació del material amb estequiometria AgCuS. El material va ser caracteritzat termoelèctricament, tot i que no mostra resultats satisfactoris degut a la seva baixa conductivitat elèctrica. En tercer lloc, es presenten quatre nanoestructures noves basades en Cu, Pt i Se, sintetitzades mitjançant una reacció a alta temperatura entre NPs de Cu2-xSe sintetitzades prèviament i un precursor de Pt(II). L’impacte de la relació Pt:Cu utilitzada en la síntesi en el producte final va ser estudiada. A mesura que la quantitat de platí augmenta en l’estructura, aquest es va introduint més eficientment en la xarxa cristal·lina del semiconductor de coure i seleni, expulsant gradual i lentament el seleni fins a la totalitat, augmentant així el caràcter metàl·lic de les nanoestructures finals. Finalment, es descriuen uns compostos híbrids hidrofílics, formats a partir de NPs inorgàniques (Au, Ag, Ag3AuSe2 i Au@Fe3O4) i un complex d’Au(I) de baix pes molecular i altament fluorescent. El seu acoblament està basat, essencialment, en interaccions aurofíliques/metal·lofíques entre els àtoms de la superfície de la nanopartícula i els àtoms d’Au(I) del complex.

Recently, technological advancement and the promise of next-generation devices have created an overwhelming push for the continued miniaturization of active systems to the micro- and nanometer scale. In this regime, traditional mechanical systems are largely inaccessible and as a result new active or stimuli-responsive materials are required. The work presented in this dissertation provides an understanding of the responsive nature of polymer and biopolymer interfaces especially in contact with metal nanoparticles. This understanding was utilized in conjunction with top-down template-based and self-assembly fabrication strategies to create hybrid protein based films and active polymer-metal hybrids that exhibit large and well-defined modulation of mechanical and optical properties. These materials processing developments represent advancement in the current state of the art specifically in three major areas: 1. template-based top-down control of protein chain conformation, 2. high-throughput synthesis and assembly of strongly coupled plasmonic nanoparticles with modulated optical properties (both near- and far-field), 3. field-assisted assembly of highly mobile and non-close packed magnetic nanorods with capabilities for rapid actuation.

All the carbon based nanomaterials (CNMs) are highly hydrophobic, which make them unsuitable for most of the applications in water and organic solvents. Aggregation phenomena significantly reduce the high performances displayed by the single nanostructure. Two main strategies allow to overcome this bottleneck: the chemical functionalization with hydrophilic functional groups or the non-covalent interaction between CNMs and amphiphilic molecules. The aim of this thesis has been to produce different carbon-based hybrid nanostructures to preserve the peculiar properties of CNMs and use them for advanced application in nanomedical and technological fields. In the first project, the potential application of fullerene (C60) as sensitizer for photodynamic therapy was explored. Monodispersity of fullerenes is the key feature for its potential application in this field. Noncovalent approach was used to disperse C60 in water, taking advantage from the surfactant-like properties of the proteins. C60@lyszoyme hybrid was used as model system to study the stability of fullerene in physiological conditions and to assess its ability to produce reactive oxygen species upon irradiations. The second subject of my research concerned the study of interactions between fluorescent nanodiamonds (FNDs) and plasma proteins. FNDs show potential applications as probe for bioimaging but their tendency to aggregate in physiological environments is the main limit for their application. In this study, a procedure to keep monodispersed FNDs in relevant biological fluids was optimized and the composition of FNDs protein corona was extensively characterized. The third project was addressed to the manufacturing of graphene based calcite nanocomposite. Both covalent (graphene oxide) and non-covalent (graphene/biomolecules adducts) approaches were used to disperse graphene in water. Following a biological inspired synthetic procedure, it was possible to incorporate the 2D materials within a 3D crystal lattice, producing a nanocomposite possessing several new properties.

This thesis deals with the engineering of novel nanomaterials, particularly nanocomposites and nanostructured surfaces with enhanced functionalities. The study includes two parts; in the first part, an in situ sol-gel polymerization approach is used for the synthesis of polymer-inorganic hybrid material and its exceptional transparent UV-shielding effect has been investigated. In the second part, electrodeposition process has been adapted to engineer surfaces and the boiling performance of the fabricated nanostructured surfaces is evaluated.

In the first part of the work, polymer-inorganic hybrid materials composed of poly(methylmethacrylate) (PMMA) and zinc compounds were prepared by in situ sol-gel transition polymerization of zinc complex in PMMA matrix. The immiscibility of heterophase of solid organic and inorganic constituents was significantly resolved by an in situ sol-gel transition polymerization of ZnO nanofillers within PMMA in the presence of dual functional agent, monoethanolamine, which provided strong secondary interfacial interactions for both complexing and crosslinking of constituents.

In the second part of the work, nanoengineering on the surface of copper plates has been performed in order to enhance the boiling heat transfer coefficient. Micro-porous surfaces with dendritic network of copper nanoparticles have been obtained by electrodeposition with dynamic templates. To further alter the grain size of the dendritic branches, the nanostructured surfaces underwent a high temperature annealing treatment.

Comprehensive characterization methods of the polymer-inorganic hybrid materials and nanoengineered surfaces have been undertaken. XRD, 1H NMR, FT-IR, TGA, DSC, UV-Vis, ED, SEM, TEM and HRTEM have been used for basic physical properties. Pool boiling tests were performed to evaluate the boiling performance of the electrodeposited nanostructured micro-porous structures.

The homogeneous PZHM exhibited enhanced UV-shielding effects in the entire UV range even at very low ZnO content of 0.02 wt%. Moreover, the relationship between band gap and particle size of incorporated ZnO by sol-gel process was in good agreement with the results calculated from the effective mass model between bandgap and particle size. The fabricated enhanced surface has shown an excellent performance in nucleate boiling. At heat flux of 1 W/cm2, the heat transfer coefficient is enhanced over 15 times compared to a plain reference surface. A model has been presented to explain the enhancement based on the structure characteristics.

Cette thèse vise à développer de nouveaux matériaux hybrides pour les applications en électrochimiluminescence. Les propriétés électrochimiluminescentes de nouveaux complexes de Pt(II) et d’Ir(III) ont été explorés comme alternative aux marqueurs existants. En plus, la combinaison de complexes et de carbon nanodots portant des groupes primaires ou tertiaires à la surface comme espèces coréactives a abouti à une stratégie intéressante pour éliminer la TPrA. Les carbon nanodots dans un systéme lié par liaison covantent avec complexes métalliques sont non seulement un support innocent pour les espèces actives d’ECL, mais agissent également comme coréactif, se révélant être une plateforme auto-améliorante en ECL. Enfin, un véritable immunoessai pour la détection des marqueurs cardiaques a été mis au point avec une sensibilité et une stabilité accrues pour les applications de détection biologique et biomédicale. La même technologie peut alors être appliquée à une variété d’autres analytes, ouvrant ainsi le site à d’autres dosages
This doctoral dissertation aim to develop new hybrid materials for ECL applications. In the field of metal complexes, the electrochemiluminescent properties of new Pt(II) and Ir(III) complexes were investigated as alternative of existing complexes. Passing to nanomaterials, the combination of labels and NCNDs bearing primary or tertiary groups on the surface as alternative co-reactant species resulted an interesting strategy to eliminate the toxic TPrA. In particular, NCNDs in covalently linked system with metal complexes is not only an innocent carrier for ECL active species, but act also as co-reactant in the ECL process, revealing itself an ECL self-enhancing platform. Finally, a real immunoassay for cardiac marker detection has been built with enhanced sensitivity and stability, which is of fundamental importance for biological and bio-medical detection applications. The same technology can be applied to a variety of other analytes opening the venue to other assays

This Ph.D. thesis describes the versatility of amine triphenolate complexes to be used either as self-assembling molecular scaffolds with applications in material sciences and molecular recognition, like titanium (IV) µ-oxo TPA complexes, or as active catalysts in homogeneous and heterogeneous catalysis, mainly vanadium (V) TPA complexes. In Chapter 1, the principles of self-assembly are listed, i.e. control on the electronic properties and size discrimination for the realization of supramolecular structures, error-checking, and efficiency, in the way of building up ordered and highly-structured entities under mild conditions. Different examples are proposed, but the analysis is mainly focused on the possibility of applying self-assembly in metal coordination chemistry in order to design highly ordered and functional systems, that may find applications in catalysis or material sciences. In this view, the coordination chemistry and the behaviour in solution of Ti(IV) TPA complexes are presented and in particular the possibility to switch between mononuclear and dinuclear µ-oxo species, depending on the steric nature of peripheral substituents, as well as the feasibility to build up highly functional Ti(IV) molecular scaffolds. A brief introduction on V(V) TPA complexes is reported as well, especially on their Lewis acid nature and structural characteristics that make them be considered as functional models of natural vanadium-dependent haloperoxidases and be used as active catalysts in oxygen transfer reactions. As the realization of new efficient and functional supramolecular systems supposes the design of the right building blocks, in Chapter 2, the modification of amine triphenolate skeleton is proposed. The functionalization strategy that has been adopted is based on a click-type oxime bond formation upon reaction of an aldehyde group, which can be effectively and selectively inserted on TPA ligands through the so-called Duff reaction, and a wide variety of alkoxyamines. In this way, the ligand skeleton has been efficiently decorated with polar and positively charged moieties, such as TEG arms and imidazolinium residues, and with pyrene groups. The functionalization has interested diverse positions of the ligand and even a double functionalization of two different positions on the same tri-phenolamine can be achieved. Chapter 3 deals with titanium (IV) amine triphenolate complexes and with the thermodynamic stability in solution of a Ti(IV) complex obtained by complexation with tris-(2-hydroxy-3-phenylbenzyl)amine. In more details, the reaction gives rise to a mononuclear complex, which upon reaction with water stereoselectively self-assembles into a highly stable, inert, dinuclear, heterochiral S6-symmetric µ-oxo TPA complex. Highly decorated Ti(IV) µ-oxo TPA complexes can be efficiently obtained by effecting the complexation reaction on functionalized ligands reported in Chapter 2, or by directly functionalizing Ti(IV) µ-oxo TPA complexes, which bear six aldehyde groups in para and/or meta positions, with the appropriate alkoxyamine. The functionalization strategy enables to construct stable and spatially ordered materials. In particular, two different Ti(IV) µ-oxo TPA complexes, bearing pyrene groups in para and meta positions, respectively, have been used as molecular receptors for fullerene. Fluorescence spectroscopies and DOSY-NMR analyses clearly indicate that pyrene groups on titanium complexes interact with fullerene through π-π interactions. Additionally, interactions between pyrene groups in para position on Ti(IV) µ-oxo TPA complex and SWCNTs (single walled carbon nanotubes) has been studied as well. Even in this case, fluorescence studies have been carried out and AFM images clearly show that CNTs are covered from Ti(IV) µ-oxo TPA complexes, highlighting the possibility to use such these systems for the design of ordered and functional supramolecular structures. Finally, in Chapter 4, the catalytic activity of V(V) TPA complexes is studied, both in sulfoxidation and aerobic oxidative C-C cleavage reactions. Firstly, the activity of an electron-poor V(V) TPA complex, bearing six chloro groups in ortho and para positions, is investigated in sulfoxidation reactions in presence of hydrogen peroxide as terminal oxidant. The reactions are performed with high yields and selectivities (catalyst loading down to 0.001% and TONs up to 89000). Both reaction rates and selectivities confirm the higher activity of the new catalyst with respect to the ones reported in literature. Moreover, modification of V(V) complexes through oxime bond formation has also led to the realization of organogelator-derived complexes, which have been found to form organogels in dioxane. Lastly, functionalization of V(V) complexes with positively charged moieties makes it possible to obtain water-soluble micelles, upon solubilisation with SDS (sodium dodecyl sulphate). The micellar like system has been tested in aerobic oxidative C-C cleavage of vicinal diols, with high selectivity and quite short reaction times. The compartmentalization of the catalytic system allowed its recycling and reuse for three times by extraction of products with organic solvents.
Questa tesi di dottorato descrive la sintesi e la funzionalizzazione di complessi amminotrifenolati di titanio (IV) e vanadio (V) per applicazioni in reazioni di riconoscimento molecolare e in catalisi. Nel Capitolo 1, sono illustrati i principi che regolano il self-assembly, quali controllo, correzione degli errori ed efficienza. E’ mostrato come questi possano essere applicati per la realizzazione di entità ordinate e strutturate in chimica di coordinazione, per la costruzione di sistemi metallo-supramolecolari, con applicazione in catalisi o scienze dei materiali. In quest’ottica, sono studiati la chimica di coordinazione e il comportamento in soluzione di complessi TPA di titanio (IV) e in particolare la capacità di fornire specie mono- o dinucleari a seconda dell’ingombro sterico dei sostituenti periferici e la possibilità di costruire scaffolds molecolari di titanio (IV) altamente funzionalizzati. Inoltre, è riportata una breve introduzione sui complessi TPA di vanadio (V), in particolar modo sulla loro proprietà di acidi di Lewis e sulle loro caratteristiche strutturali, che fanno sì che vengano considerati dei modelli funzionali delle aloperossidasi naturali vanadio-dipendenti e quindi vengano utilizzati come catalizzatori in reazioni di trasferimento di ossigeno. Nel Capitolo 2, viene proposta una strategia sintetica per modificare lo scheletro trifenolamminico. La funzionalizzazione prevede la formazione di un legame ossimico, mediante una reazione click-simile tra un’aldeide, che può essere selettivamente introdotta sul legante mediante reazione di Duff, e una varietà di alcossiammine. In questo modo, lo scheletro del legante può essere efficientemente decorato con residui polari e carichi positivamente, come residui TEG o imidazolinio, e con gruppi pirene. La funzionalizzazione può coinvolgere diverse posizioni del legante, così come una doppia derivatizzazione di posizioni differenti sulla stessa trifenolammina. Nel Capitolo 3, è presentata la possibilità di ottenere dei complessi dinucleari µ-oxo amminotrifenolati di titanio (IV) per reazione di complessazione della tri-(2-idrossi-3-fenilbenzil)ammina con Ti(Oi-Pr)4. Più in dettaglio, il complesso mononucleare, che si forma dalla reazione, in presenze di tracce d’acqua è in grado di auto-assemblarsi in maniera stereoselettiva, dando origine a un complesso dinucleare, altamente stabile, inerte, eterochirale, con simmetria S6. La funzionalizzazione del complesso può essere ottenuta efficacemente mediante una duplice via: effettuando la reazione di complessazione sui leganti funzionalizzati riportati in Capitolo 2, oppure funzionalizzando direttamente complessi TPA µ-oxo di titanio (IV), che portano sei gruppi aldeidici in para e/o meta, con un’appropriata alcossiammina. La strategia di funzionalizzazione permette di costruire dei materiali stabili e spazialmente ordinati. In particolare, due complessi µ-oxo di titanio che portano gruppi pirene rispettivamente in para e meta sono stati utilizzati come recettori molecolari per il fullerene. Spettroscopie di fluorescenza ed esperimenti DOSY-NMR indicano chiaramente che i gruppi pirene sui complessi di titanio interagiscono con il fullerene mediante interazioni π-π. Come ulteriore applicazione, sono state studiate le interazioni tra gruppi pirene dei complessi TPA µ-oxo di titanio e nanotubi di carbonio (SWCNTs). Anche in questo caso, sono stati condotti studi di fluorescenza e analisi AFM mostrano chiaramente che i nanotubi sono rivestiti dai complessi di titanio, evidenziando la possibilità di usare questi sistemi per generare strutture supramolecolari ordinate e funzionali. Infine, nel Capitolo 4, è studiata l’attività catalitica di complessi TPA d vanadio (V), sia in reazioni di solfossidazione che in reazioni di cleavage aerobico ossidativo di legami C-C. Prima di tutto, viene analizzata l’attività catalitica di un complesso di vanadio (V) elettron-povero, portante sei atomi di cloro in posizioni orto e para, in reazioni di solfossidazione in presenza di perossido d’idrogeno come ossidante terminale. Le reazioni sono condotte con alte rese e selettività, anche in presenza dello 0.001% di catalizzatore, con TON fino a 89000. Le velocità di reazione e le selettività confermano una attività maggiore del catalizzatore rispetto ai catalizzatori riportati in letteratura. In più, la modificazione di complessi TPA di vanadio (V) mediante formazione di un’ossima ha portato anche alla realizzazione di complessi funzionalizzati con catene organogelator e alla formazione di organogel in diossano. In conclusione, la funzionalizzazione di complessi TPA di vanadio (V) con residui carichi positivamente permette di ottenere micelle solubili in acqua, in seguito a solubilizzazione con SDS (sodio dodecil solfato). Il sistema micellare è stato poi testato in reazioni di cleavage aerobico ossidativo di legami C-C di dioli vicinali, con elevate selettività e tempi di reazione relativamente bassi. Il sistema catalitico può essere inoltre riciclato e riutilizzato fino a tre volte in seguito a estrazione dei prodotti con solventi organici

Doutoramento em Física
O presente trabalho propõe-se caracterizar a estrutura e as propriedades de fotoluminescência de materiais híbridos orgânicos/inorgânicos. A origem química e fotofísica subjacente à emissão de luz branca dos diureiasils, híbridos compostos por uma rede siliciosa ligada covalentemente por pontes ureia a cadeias poliméricas, foi estudada fazendo uso de dois compostos modelo que reproduzem, selectivamente, as componentes orgânica e inorgânica daquela rede híbrida. A emissão nos di-ureiasils resulta da convolução de uma componente originada nos grupos ureia com uma outra proveniente dos domínios siliciosos. A comparação entre os tempos de vida das emissões dos compostos modelo com as do híbrido, a dependência do tempo de vida destas emissões com a temperatura e a variação da curva de decaimento associada à emissão dos grupos ureia com o tempo de atraso entre o final da excitação e o início da medida, suportam a ocorrência de transferência de energia entre a componente originada nos domínios siliciosos e a proveniente dos grupos ureia. A taxa de transferência de energia foi quantitativamente estimada considerando os mecanismos de troca (3.7×108 s- 1 ) e dipolo-dipolo (1.3×109 s-1). Esta taxa foi, também, calculada para um diureiasil incorporando um complexo de Eu3+ tendo-se verificado que o canal mais eficiente para a luminescência é: (S0) Híbrido → (T) Híbrido → (T) Ligando → (5D1, 5D0) → 7 F0-4. Um precursor híbrido com cadeias alquílicas e grupos ureia (P12), preparado por catálise àcida ou nucleofílica, deu origem, respectivamente, a uma estrutura lamelar cristalina (L12) e a um material amorfo (A12). Iões Eu3+ foram incorporados nos dois sistemas. Para os híbridos obtidos por catálise nucleofílica, demonstrou-se que a sua morfologia é fortemente determinada pela presença e modos de coordenação dos iões Eu3+. Todos os híbridos são emissores de luz branca. A incorporação de iões Eu3+ diminui o rendimento quântico da rede híbrida, o que indica a existência de transferência de energia rede-iões Eu3+ . Um precursor incorporando bipiridina e grupos ureia foi preparado pelo método sol-gel através de catálise nucleofílica, dando origem a híbridos amorfos. Estes híbridos são caracterizados por uma emissão de banda larga atribuída à sobreposição de três componentes: i) estado tripleto da bipridina, recombinações electrão-lacuna originadas ii) nos grupos ureia e iii) nos domínios siliciosos. Valores de 0.18-0.22 foram obtidos para o rendimento quântico, para excitação no UV/azul. Foi demonstrado que os híbridos podem ser excitados com um LED de INGaN comercial, tornando-os materiais promissores para aplicações em fontes de luz de estado sólido. Os híbridos foram também preparados incorporando iões Eu3+, Gd3+, Tb3+ e Eu3+/Tb3+. Os materiais resultantes são emissores de luz branca onde a emissão intra 4-f dos iões lantanídeo se sobrepõe à emissão da rede híbrida.
The present work focuses on the characterization of the structural and photoluminescence (PL) properties of a series of organic/inorganic hybrids. The photophysical and chemical origin behind the white-light photoluminescent features of amide-functionalized hybrids lacking metal activators (di-ureasils) was studied making use of two model compounds that selectively reproduced the organic and inorganic counterpart parts. The comparison between the lifetimes of the two emissions of the inorganic and organic model compounds with those of the hybrids, the Arrhenius dependence with temperature of the siliceous-related lifetime in the hybrids, and the nonexponential behavior of the decay curve of the siliceous-related emission under lower excitation wavelengths are experimental evidence supporting the occurrence of energy transfer in the hybrids. This energy transfer rate is quantitatively estimated for a di-ureasil, generalizing the ideas proposed by Malta, considering the exchange (3.7×10 8 s-1) and dipole–dipole mechanisms (1.3×10 9 s-1). The energy transfer rates were also calculated for a di-ureasil incorporating a Eu3+ complex and it was found that the most efficient luminescence channel is (S 0)Hybrid → (T)Hybrid → (T)Ligand → ( 5 D 1, 5 D 0) → 7 F0-4. A di-urea cross-linked alkylsilane precursor prepared using HCl induced the formation of a crystalline lamellar structure (L12); when prepared with NH 4F an amorphous material (A12) was obtained. Eu3+ ions were incorporated in the two systems and the unique role played by the Eu3+ ions in the modulation of the morphology of Eu@A12 hybrids was for the first time demonstrated via inhibition of the growth of the siloxane network formed through sol-gel reactions and urea-mediated supramolecular self-assembly. All the hybrids are room temperature multi-wavelength emitters and the incorporation of Eu3+ into the L12 and A12 hybrids induces a decrease in the absolute emission quantum yield values, supporting the existence of hybrid-to-Eu3+ energy transfer. A di-urea cross-linked bipyridine (bpy) precursor prepared by sol-gel synthesis under nucleophilic catalysis, by TBAF and NH 4F, gave rise to amorphous hybrids (termed as H and M). They are characterized by emission spectra that consist of a broad band unequivocally ascribed to a superposition of three distinct components: i) bpy triplet state, ii) electron-hole recombinations originated in the NH/C=O groups of the urea cross-linkages and iii) siliceous nanoclusters. Quantum yield values of 0.22-0.18 were measured under excitation in the long-wavelength UV and blue spectral regions. It was demonstrated that H can be efficiently excited using a commercial LED, placing bpy-hybrids as promising materials for photonics and solid state lighting. M was also prepared in the presence of Eu3+, Gd3+, Tb3+, and Eu3+/Tb3+ and formed hybrids that are room temperature multi-wavelength emitters. This is due to the convolution of the emission arising from the hybrid's emitting centres and the Ln3+ intra-4f transitions. The emission colour is tuned across the CIE diagram depending on the Ln3+ ions and the excitation wavelength.

During the last three decades, great scientific efforts led to the discovery and development of new carbon nanomaterials (e.g. carbon nanotubes or CNTs, carbon nanohorns or CNHs, and graphene or G). In the first chapter of this thesis, a general introduction on carbon nanostructures (CNS) and relevant characterisation techniques is provided (Chapter 1). Despite their superior electrical, thermal, and mechanical properties, CNS inherent tendency to aggregate initially limited their applications. This issue can be addressed by various chemical functionalisation routes to improve their dispersibility in water and in polar solvents, thus allowing their handling in liquid phase, and their combination with other chemical entities. Assembly of such multicomponent nanomaterials considerably expands CNS use in fields ranging from biology to energy. In this work, CNS were functionalised to be combined with components of different nature into hybrids or composites for diverse applications. In particular, Chapter 2 discusses the modification of CNTs and G via acid-mediated oxidation or diazo coupling routes to add hydrophilic appendages that favour in situ growth of metal oxide nanostructures (e.g. TiO2). The resulting nanohybrids were tested for photocatalytic hydrogen production. Oxidation of CNT fibres (CNF) was also achieved, first through wet methods, and then by treatment with UV-generated ozone, with only the latter allowing preservation of their macroscopic integrity. The resulting hydrophilic CNF displayed enhanced performance for supercapacitors. Chapter 3 focusses on in situ polymerisation of dopamine on the surface of CNTs and CNHs. The synthetic protocol was optimised to achieve homogeneous coatings that, after graphitisation through high temperature treatment under argon, became conductive. This two-step sequence resulted in the isolation of N-doped CNHs that catalysed the electrochemical reduction of O2 into H2O2 with superior performance relative to current state-of-the-art catalysts. Finally, hydrogel composites were prepared from either CNTs, CNHs, or G and a self-assembling tripeptide (Chapter 4). After an oxidative pre-treatment, each CNS was combined with the peptide and formed supramolecular hydrogels of improved rheological properties (i.e. increased stiffness and resistance to applied stress). Interestingly, hydrogels containing CNTs showed self-healing capacity, thus opening a new window of application for these materials

The thesis work aimed to find appropriate syntheses procedures for the preparation of Nano Building Blocks (NBB) and Nano Particles (NP), starting from organo silanes as molecular precursors, using the Sol-Gel method. NBB were obtained by either non-hydrolytic or in situ water production (ISWP) route, depending on the reactive function’s loading. The obtained NBB were characterised by means of FT-IR, ATR/FT-IR, RAMAN, multinuclear NMR spectroscopies, SEM, N2 physisorption, Thermal analyses (TG/DTA), DSC. NBBs were used to prepare methacrylate-based matrices, which were subsequently exploited in order to produce patternable films by the two photon polymerisation technique (TPP). Epoxy-based matrices were also prepared and the films obtained were patterned by the UV photolithography technique. Both techniques gave high surface resolution patterning. NP were obtained with a modified Stöber method and organosilica NP were obtained. The NP were characterised by FT-IR and NMR spectroscopies. Morphology was observed and sizes calculated using SEM; N2- physisorption and thermal analyses (TG/DTA) were also carried out in order to complete the characterization. DSC measurements were performed on methacryloxypropyl-functionalised NP in order to control the ability to polymerise of the particles. Films of the different organic-modified NP were obtained by spin coating and contact angle measurements were performed. FE-SEM was used in order to observe an eventual change in morphology after thermal treatment under reduced atmosphere. The ability to retain the shape depends on the functional group on the NP. Finally a preliminary study on dye doping was accomplished. The NP were efficiently doped with a fluorescent dye: Rhodamine 6G (R6G). Absorption and emission spectra were recorded with a spectrofluorometer. It is observable that the emission spectra is influenced by the NP’s matrix.

The thesis work aimed to find appropriate syntheses procedures for the preparation of Nano Building Blocks (NBB) and Nano Particles (NP), starting from organo silanes as molecular precursors, using the Sol-Gel method. NBB were obtained by either non-hydrolytic or in situ water production (ISWP) route, depending on the reactive function’s loading. The obtained NBB were characterised by means of FT-IR, ATR/FT-IR, RAMAN, multinuclear NMR spectroscopies, SEM, N2 physisorption, Thermal analyses (TG/DTA), DSC. NBBs were used to prepare methacrylate-based matrices, which were subsequently exploited in order to produce patternable films by the two photon polymerisation technique (TPP). Epoxy-based matrices were also prepared and the films obtained were patterned by the UV photolithography technique. Both techniques gave high surface resolution patterning. NP were obtained with a modified Stöber method and organosilica NP were obtained. The NP were characterised by FT-IR and NMR spectroscopies. Morphology was observed and sizes calculated using SEM; N2- physisorption and thermal analyses (TG/DTA) were also carried out in order to complete the characterization. DSC measurements were performed on methacryloxypropyl-functionalised NP in order to control the ability to polymerise of the particles. Films of the different organic-modified NP were obtained by spin coating and contact angle measurements were performed. FE-SEM was used in order to observe an eventual change in morphology after thermal treatment under reduced atmosphere. The ability to retain the shape depends on the functional group on the NP. Finally a preliminary study on dye doping was accomplished. The NP were efficiently doped with a fluorescent dye: Rhodamine 6G (R6G). Absorption and emission spectra were recorded with a spectrofluorometer. It is observable that the emission spectra is influenced by the NP’s matrix.

Cette étude a pour but d’explorer l’influence du nanoconfinement sur le comportement de substrats organiques incorporés dans des silices mésoporeuses. Ces travaux s’articulent en deux volets. Le premier est une étude sur l’efficacité de la réaction de fragmentation par voie photochimique ou thermique d’alcoxyamines confinées. Par comparaison avec une étude réalisée en solution, des mesures effectuées par spectroscopie RPE quantitative ont permis de montrer que l’efficacité de cette rupture n’est pas altérée par l’incorporation des précurseurs organiques dans une matrice de silice. Dans un second temps des matériaux hybrides organiques-inorganiques fonctionnalisés par des précurseurs diazèniques ont été synthétisés. Ces derniers sont capables, sous irradiation à 360 nm, de former des radicaux hétéroatomiques qui sont transitoires en solution mais persistants dans la silice. Différentes structures ont été synthétisées, notamment des matériaux fonctionnalisés par une paire de radicaux de nature différente, i.e. un radical aryloxyle disposé face à un radical arylsulfanyle. Des études RPE en onde continue et pulsée ont permis de mettre en évidence la grande durée de vie de ces espèces paramagnétiques confinées et de mesurer leurs temps de relaxation
The aim of this work was to investigate the influence of the nanocofinement on the behaviour of organic substrates embedded in mesoporous silicas. This research hinged on two parts. The first study focused on the efficiency of the fragmentation reaction of confined alkoxyamines, under thermal or photochemical activation. Thanks to the comparison with the very same reactions in solution, the quantitative EPR measurements showed that the confinement of organic precursors had no effect on the efficiency of these reactions. Secondly, organic-inorganic hybrid materials were synthesized. These mesoporous silicas were functionalized with diazene radical precursors. Upon 360 nm irradiation, they generated heteroatomic radicals. Different materials were prepared, including one which enabled to form a face-to-face pair of different radicals, i.e. an aryloxyl radical in front of an arylsulfanyl radical. Studies carried out by continuous and pulsed wave EPR enabled to highlight the high stability of these confined paramagnetic species and to measure their relaxation times

In this thesis, by means of different case studies, we explore the design from the micro to the atomic scale of different nanostructured heterogeneous catalysts that can be applied in the field of energy conversion and chemicals synthesis. We highlight the importance of the rational design of the materials to improve significantly the efficiency and performances of novel heterogeneous catalysts. The chemical nature and the morphology of the catalysts are correlated with their catalytic activities in order to tailor their physicochemical properties for each specific application. To do this, we have employed a large set of tools offered by Materials Science, exploring advanced synthetic methods and operando and in situ characterization techniques.
In questa tesi, attraverso diversi casi di studio, abbiamo studiato il design dalla scala micrometrica a quella atomica di diversi catalizzatori eterogenei nanostrutturati che possono essere applicati nel campo della conversione energetica e della sintesi chimica. In questo lavoro, abbiamo sottolineato l'importanza della progettazione razionale dei materiali per migliorare significativamente l'efficienza e le prestazioni di nuovi catalizzatori eterogenei. La natura chimica e la morfologia dei catalizzatori sono state correlate con le loro attività catalitiche al fine di adattare le loro proprietà fisico-chimiche per ogni specifica applicazione. Per fare questo, abbiamo impiegato un ampio set di strumenti offerti dalla Scienza dei Materiali, esplorando metodi sintetici avanzati e tecniche di caratterizzazione operando e in situ.

Carbon materials constitute a large family of diverse structures and textures that underlie an increasing range of applications suggested by the impressive number of papers published on this topic. Several hundreds of thousands of publications have appeared since 1900, out of which, thousands were published during the last decade (Web of Science™, Thomson Reuters, Scopus, SciFinder using as searching topics “carbon materials,” “carbon chemistry,” “carbon nanomaterials,” “carbon nanotubes,” and “graphene”). The popularity of carbon materials is due to a unique combination of physical and chemical properties such as high electrical conductivity, high surface area, good resistance to corrosion, high thermal stability, and high chemical stability in non-oxidizing environments and particular mechanical properties. Carbon materials are easy to process, provide a wide variety of structures and textures, have diverse surface chemical properties and are compatible with other materials, thus are ideal for composites as well. This unique combination of properties is a consequence of the different hybridization of orbitals in C atoms and the possibility of combining with other heteroatoms. Carbon materials form the basis of numerous applications in a wide variety of research and engineering areas. This causes publications on carbon-based materials to appear traditionally in various journals from both scientific and engineering domains. Certainly, new uses will appear considering the versatility of carbon materials. In this thesis, the use of carbon materials for applications in energy storage, gas sensing and additive manufacturing is taken into account. In addition, particular attention is given to different approaches of nanomaterials syntheses either chemical or electrochemical route. Integration of carbon materials (especially nanocarbons) into other components to design functional or structural materials is a critical issue. Functional materials constituted by a carbon material and another component such as metal oxides, polymers and conductive polymers, are very much studied for energy storage. In this case, synthetic methods to achieve an adequate distribution of both components and improve synergies are considered. In summary, research on carbon-based materials is a very dynamic and growing area of study with nearly unlimited possibilities. We still have plentiful theoretical and applied issues to be understood regarding the structure, texture, and properties of carbon materials.

In the last years, the massive evolution of modern technologies has gradually created an alarming gap between the production and the consumption of energy. Traditional energy resources are no longer sufficient to satisfy the demand of energy without spoiling earth environment. Solar photovoltaics represents a highly promising technology to tackle this global energy issue. The thorough scientific discussion on this fundamental topic gave rise to interesting results and the organic solar cells (OSCs) are one of these achievements. One major reason of the development and the increasing interest in this new technology is its eco-friendliness and the potentially low-cost production of solar modules on flexible (plastic) substrates. Furthermore, new applications are expected by flexible or semitransparent organic solar cells. Nevertheless, two main problems must be overcome before this promising technology replaces the long-established silicon solar cells: the low power conversion efficiency and the scarce stability. In order to tackle these fundamental issues the research efforts must be focused towards both the development of new materials and their detailed photophysical and morphological characterization. Recently the application of nanostructured architectures within the active layers of OSCs has demonstrated to be an efficient alternative to boost solar cell efficiency. Indeed, the nanometric miniaturization of materials opened a huge amount of possibilities to tune and bolster their optical and electrical properties. In this thesis work, the potentialities of the nanostructured architectures are explored. In particular, the attention of this work is addressed towards the development and the photophysical characterization of new hybrid nanostructured photoactive materials. Three different families of nanostructures, colloidal Quantum Dots, Carbon Dots, and hybrid organic/inorganic perovskite nanoparticles, are blended with organic photovoltaic materials. The thorough investigation of the photo-physical and morphological interactions between the nanostructures and the organic materials aims to investigate these nanocomposite as new photoactive materials for next-generation solar cells. The first step of the work focuses on the investigation of a prototypical active layer consisting in binary blends of the fullerene derivative PCBM and CdSe/CdS core-shell Quantum Dots (QDs) capped with different ligands (namely, oleylamine, octadecanethiol, and propanethiol). The double purpose is both to demonstrate that QDs do not influence only the morphology of the active layers, as it is often reported in literature, but also its photophysics and to unravel the pivotal role of QDs ligands on the electron transfer process, which is fundamental for organic solar cells. Through the combined use of steady-state, time resolved and pulsed electron paramagnetic resonance (EPR) techniques the photophysical role of QDs in OSCs is clarified and the possibility to tailor the electron transfer process through the proper choice of QDs ligands is demonstrated. The second part of the work aims at promoting the application of carbon dots (CDs) as electron donor materials for OSCs. CDs seem to be a good alternative to colloidal QDs, thanks to their low toxicity, good biocompatibility and peculiar photo-physical properties, however their poor solubility in organic solvents and mediocre electron-donor properties hampered their photovoltaic application. To tackle these critical issues, the synthesis and photo-physical characterization of N-doped CDs functionalized with two different thiophene-containing groups is carried out in this work. The functionalization intends to enhance the electron donating properties of the CDs and improve their solubility in organic solvents. The increased solubility allows to investigate the photoinduced interactions of functionalized CDs with the PCBM in solution and in solid blends. Through the combined cyclic voltammetry, optical and EPR analysis the enhanced electron donor capabilities of the functionalized CDs are demonstrated and the electron transfer process is characterized in detail. Finally, the last part of the work concentrates on the hybrid organic inorganic perovskite nanostructures. These recent nanostructures are definitely the best candidate to compete with silicon solar cells since their bulk counterpart has already provided record photovoltaic efficiencies in less than five years. However, the application of perovskite nanoparticles (PNPs) in organic solar cells has been scarcely investigated so far. Therefore, in this thesis work the synthesis of PNPs and the investigation of their interaction with both the PCBM and the semiconducting polymer P3HT is carried out. After the confirmation of the obtained synthesis through optical spectroscopy, X-ray diffraction and XPS analysis, the electron transfer from PNPs to PCBM is investigated. In particular, the effect of the ligand length on the electron transfer is examined, probing the process with two different PNPs ligands: octylamine and oleylamine. Successively, the role of the PNPs in blend with P3HT is studied. A triple effect of PNPs on the polymer properties is observed: (1) an increment of the dimension of P3HT crystalline domains, (2) a p-doping of the P3HT, and (3) an enhanced interchain order. The results of this work underpin the relevance of applying nanostructured architectures in organic photovoltaic materials, highlighting their beneficial role not only in morphology, but also in the main photo-physical processes that take place in solar cells. Additionally, the relevant role of the tailored surface engineering of nanostructures in the process of solar energy conversion is evidenced. All these observations aim at providing guidelines for the design and the fabrication of highly efficient solar cells.
Negli ultimi anni, a causa della frenetica evoluzione delle moderne tecnologie, si è andata a creare una divergenza sempre più allarmante tra la produzione e il consumo di energia. Le risorse tradizionali di energia, infatti, non sono più sufficienti a soddisfare la sempre crescente domanda energetica senza il drastico effetto di rovinare l’ambiente che ci circonda. Il fotovoltaico rappresenta una tecnologia promettente per affrontare il problema energetico mondiale. La ricerca scientifica focalizzata su questo argomento fondamentale ha dato luogo a risultati molto interessanti e le celle solari organiche ne sono una dimostrazione. Uno dei principali motivi dello sviluppo e del crescente interesse in questa nuova tecnologia è legato alla sua ecosostenibilità e al basso costo di produzione dei moduli solari che solitamente avviene su substrati (polimerici) flessibili. Inoltre, dal momento che questa tecnologia si basa sulla produzione di celle solari trasparenti e flessibili numerose applicazioni innovative sono già previste. Nonostante ciò, prima che il forovoltaico organico prevalga sulle celle solari al silicio che già da anni si sono affermate nella scena mondiale, due problemi principali devono essere affrontati: la bassa efficienza e la scarsa stabilità dei moduli fotovoltaici organici. Per far fronte a questi problemi la migliore alternativa è focalizzare gli sforzi della ricerca sia sullo sviluppo di nuovi materiali sia sulla loro caratterizzazione fotofisica e morfologica. Recentemente, l’applicazione di nanostrutture all’interno degli strati attivi delle celle solari organiche ha dimostrato di essere un’idea efficace per promuovere l’efficienza delle celle solari. Infatti è risaputo che la miniaturizzazione a livello nanometrico dei materiali apre la strada a numerose possibilità per controllare e incrementare le loro proprietà ottiche ed elettriche. In questo lavoro di tesi, le potenzialità delle nanostrutture vengono prese in considerazione. In particolare, l’attenzione di questa tesi è indirizzata allo sviluppo e alla caratterizzazione fotofisica di nuovi materiali nanostrutturati fotoattivi ibridi. Tre differenti famiglie di nanostrutture, i Quantum Dots colloidali, i Carbon Dots e le nanoparticelle di perovskite ibrida organica/inorganica, sono state incorporate all’interno di materiali fotovoltaici organici. Lo studio dettagliato delle interazioni fotofisiche e morfologiche tra le nanostrutture e i materiali organici ha permesso di considerare questi materiali nanocompositi come materiali promettenti per il fotovoltaico di nuova generazione. La prima parte del lavoro si focalizza sullo studio di uno strato fotoattivo costituito dal derivato fullerenico PCBM e dai Quantum Dots (QDs) core-shell di CdSe/CdS funzionalizzati con tre leganti differenti (l’oleilammina, l’ottadecantiolo e il propantiolo). Il primo obiettivo è stato dimostrare che la presenza dei QDs non solo influenza la morfologia degli strati fotoattivi delle celle solari, come spesso è riportato in letteratura, ma anche la loro fotofisica. Il secondo obiettivo è stato chiarire il ruolo fondamentale dei leganti dei QDs nel processo di trasferimento elettronico, processo essenziale nelle celle solari organiche. Attraverso l’uso combinato di tecniche di risonanza magnetica elettronica di stato stazionario, risolte nel tempo e impulsate, il ruolo fotofisico dei QDs nelle celle solari organiche è stato chiarito in grande dettaglio. Inoltre, è stata dimostrata la possibilità di controllare opportunamente il processo di trasferimento elettronico attraverso la scelta accurata dei leganti dei QDs. La seconda parte del lavoro mira a promuovere l’applicazione dei Carbon Dots (CDs) come materiale elettron-donatore nelle celle solari organiche. I CDs hanno dimostrato di essere una buona alternativa ai QDs colloidali grazie alla loro bassa tossicità e biocompatibilità e alle loro peculiari proprietà fotofisiche. Nonostante ciò, la loro scarsa solubilità in solventi organici e le loro deboli proprietà elettron-donatrici hanno ostacolato sinora la loro applicazione nel campo fotovoltaico. Per far fronte a queste criticità, è stata portata a termine la sintesi e la caratterizzazione fotofisica di CDs contenenti atomi di azoto e funzionalizzati con due diversi gruppi tiofenici. Lo scopo della funzionalizzazione è stato incrementare le proprietà elettron-donatrici dei CDs e migliorare la loro solubilità in solventi organici. L’aumento di solubilità ha permesso di studiare la loro interazione fotofisica con il PCBM sia in soluzione che in film. Tramite l’utilizzo della voltammetria ciclica, della spettroscopia ottica e della spettroscopia EPR, sono state dimostrate le buone proprietà di trasferimento elettronico fotoindotto in questi materiali e il processo di trasferimento elettronico è stato studiato in dettaglio. Infine, l’ultima parte di questo lavoro di tesi si concentra sulle nanoparticelle di perovskite ibrida organica/inorganica. Le perovskiti ibride sono a tutti gli effetti il miglior candidato nella corsa per sostituire le convenzionali celle solari al silicio. Negli ultimi cinque anni le perovskiti ibride massive hanno stabilito record straordinari di efficienza fotovoltaica. Nonostante ciò, l’utilizzo delle nanoparticelle di perovskite nelle celle solari organiche non è stato ancora studiato a fondo. Per ovviare a ciò, nell’ultima parte di questo lavoro è stata portata a termine la sintesi delle nanoparticelle di perovskite ed è stata studiata la loro interazione sia con il PCBM che con il polimero semiconduttore P3HT. Dopo aver confermato l’avvenuta sintesi mediante spettroscopia ottica, diffrazione a raggi X e spettroscopia di fotoemissione a raggi X, è stato analizzato il processo di trasferimento elettronico fotoindotto tra le nanoparticelle di perovskite e il PCBM. In particolare, grazie all’utilizzo di nanoparticelle funzionalizzate con due diversi leganti (ottilammina ed oleilammina), il ruolo fondamentale della lunghezza dei leganti nel processo di trasferimento elettronico è stato evidenziato. Successivamente, l’attenzione è stata rivolta al nanocomposito di nanoparticelle di perovskite e P3HT. In questo caso, è stato osservato che la presenza delle nanoparticelle di perovskite svolge un triplice effetto sulle proprietà del polimero: (1) un incremento nella dimensione dei domini cristallini, (2) un drogaggio di tipo p, e (3) un aumento dell’ordine intercatena nella fase polimerica. I risultati di questo lavoro di tesi evidenziano la rilevanza delle nanostrutture nei materiali fotovoltaici organici sottolineando il loro effetto positivo non solo sulla morfologia, ma anche su tutti i principali processi fotofisici che hanno luogo nelle celle solari. Inoltre, viene dimostrata l’importante funzione dell’ingegnerizzazione superficiale di queste nanostrutture al fine di favorire il processo di conversione dell’energia solare. Tutti questi risultati hanno lo scopo di promuovere la progettazione, lo sviluppo e l’efficienza delle celle solari di nuova generazione.

Over the past decade, the intensive development of nanotechnology was made to increase significantly the number of methods to form the structures of a size between 1 and 100 nm. It should be emphasized that nanostructured materials are interesting both because of perspectives in practical applications and new physical phenomena. In this work the electrochemical technique for the control of morphology of porous silicon matrix developed. Hybrid por-Si structures with metals were made. The method for infiltration of biomolecules into the porous silicon structures was developed and the interaction between silicon and bio-molecules was investigated. GaP nanostructures were formed by electrochemical etching and the possibilities of their application for gas sensors were estimated. Nanoporous and Fe-doped silica films on Si were made and the developed structures were characterized by their structural, optical or magnetic properties.
Pastarąjį dešimtmetį, intensyviai vystantis nanotechnologijoms, ženkliai išaugo technologinių metodų, įgalinančių suformuoti darinius, kuriuose elementų dydžiai būtų tarp 1 ir 100 nm, paieška. Šiai specifinei nanostruktūrinių medžiagų grupei skiriamas ypatingas dėmesys dėl naujų fizikinių reiškinių ir ypač - praktinių taikymų, kuriuos atveria šie dariniai. Šiame darbe aptariamos elektrocheminės technologijos, skirtos kontroliuojamos morfologijos porėtojo silicio formavimui. Suformuoti hibridiniai por-Si dariniai su metalais. Sukurta biomolekulių įterpimo į porėtuosius silicio darinius technologija bei tirta biomolekulių sąveika su kietakūniais padėklais. Nagrinėjami GaP nanodarinių formavimo elektrocheminio ėsdinimo būdu dėsningumai bei jų taikymo galimybės dujų sensoriuose. Įsisavinta nanoporėtųjų dielektrinių terpių ir hibridinių nanodarinių formavimo technologija bei tirtos jų savybės.

The main goals in electroanalytical sensing are towards improved sensitivity and selectivity, or specificity, of an analyte. There are several approaches to achieving these goals with the main approach being modification of an electrode surface with synthetic or natural catalysts (enzymes), polymers and also utilisation of nanostructured materials. At present, there is a strong movement towards hybrid sensing which couple different properties of two or more surface modification approaches. In this thesis, a range of these surface modifications were explored for analysis and detection of two main analytes: the amino acid, tryptophan (Trp); and, the neurotransmitter, dopamine (DA). Specifically, this thesis aimed to utilise these methods to enhance the sensitivity and selectivity for Trp over an interferent, the indoleamine, melatonin (Mel); and, DA over the vitamin, ascorbic acid (AA). For Trp detection, immobilisation of an enzyme, Tryptophanase (Trpase) resulted in poor selectivity for the analyte. However, enhanced sensitivity and selectivity was achieved through pH manipulation of the electrolyte medium at a Nafion®-modified electrode surface for both Trp and Mel. At pH 3.0, the Mel and Trp anodic peak potentials were sufficiently resolved allowing for an LOD of 1.60 and 1.62 nM,respectively, and permitting the accurate analysis of Trp in a dietary supplement containing Mel. Multi-walled carbon nanotubes (MWCNTs) suspended in Nafion® exhibited further increases in the signal responses of these analytes at pH 3.0 and 7.4 with minimal change in the resolution of the anodic peaks. A lower sensitivity was, therefore, observed at the Nafion® and MWCNT modified electrode compared to the Nafion®-modified electrode at pH 3.0 with LODs of 0.59 and 0.80 nM exhibited for Trp and Mel, respectively. Enhanced selectivity for Trp in the presence of Mel can be achieved with MWCNTs in the presence of metallotetrasulphonated phthalocyanines (MTSPcs) particularly at pH 3.0, owing to cation exchange effects. However, the lack of sensitivity towards Trp, and even Mel, at this CoTSPc and MWCNT modified electrode remains a drawback. For DA, detection at the MWCNT and Nafion® surface resulted in improved sensitivity over that of both the bare electrode (613.0 nM) and the Nafion® modified electrode (1045.1 nM) with a calculated LOD of 133.9 nM at this layer. Furthermore, improvements in the selectivity of DA were achieved at the Nafion® and MWCNT modified electrode as exclusion of AA (150 μM) was achieved. At the MWCNT and CoTSPc surface, AA was excluded up to 130 μM with sensitivity for DA extending as low as 14.3 nM, far greater than observed for Trp and Mel. These concentrations are well within physiological concentration ranges and represent the most significant solution yet in terms of AA exclusion and enhanced sensitivity for DA. An examination of the surface layering by impedance spectroscopy and atomic force microscopy indicates that the success of the hybrid sensor utilising CoTSPc and MWCNTs lay in improved dispersion of MWCNTs and improved electron transfer kinetics, facilitated by the net charge of the materials present. This thesis, thus, showed the utility of a judicious selection of synthetic and biological catalysts, polymers and carbon nanomaterials towards a hybrid approach to the electrochemical sensing of Trp, Mel, DA and AA with focus on sensitivity and selectivity of these analytes.

Traditional sources of electrical energy are finite and can produce significant pollution. Solar cells produce clean energy from incident sunlight, and will be an important part of our energy future. A new nanostructured extremely thin absorber solar cell with 0.98% power conversion efficiency and maximum external quantum efficiency of 61% at 650 nm has been fabricated and characterized. This solar cell is composed of a fluorine-doped tin oxide base layer, n-type aluminum doped zinc oxide nanowires, a cadmium selenide absorber layer, poly(3-hexylthiophene) as a p-type layer, and thermally evaporated gold as a back contact. Zinc oxide nanowire electrodeposition has been investigated for different electrical environments, and the role of a zinc oxide thin film layer has been established. Cadmium selenide nanoparticles have been produced and optimized in-house and compared to commercially produced nanoparticles. Argon plasma cleaning has been investigated as a method to improve electronic behavior at cadmium selenide interfaces. The thermal anneal process for cadmium selenide nanoparticles has been studied, and a laser anneal process has been investigated. It has been found that the most efficient solar cells in this study are produced with a zinc oxide thin film, zinc oxide nanowires grown under constant -1V bias between the substrate material and the anode, cadmium selenide nanoparticles purchased commercially and annealed for 24 hours in the presence of cadmium chloride, and high molecular weight poly(3-hexylthiophene) spin-coated in a nitrogen environment.

The thesis is mainly focused on the better understanding of carbon dots (C-dots) formation in bottom-up syntheses, by identifying the key chemical processes and correlating them to the observed fluorescence. Therefore, several types of C-dots were studied, by systematically varying the used (molecular) precursor ratios and reaction times. Selected samples were surface functionalized by organosilanes to reveal the role of the C-dots surface functional groups in the overall photoluminescence. As better understanding of the ongoing processes finally achieved, the synthesized C-dots were applied in photocatalysis experiments by combining them with titania and an appropriate C-dot was tested as a nitrite ion sensor.

Durante il dottorato ho investigato il processo fotofisico di "upconversion" assistito da annichilazione tripletto-tripletto (TTA-UC) tramite studi di spettroscopia in sistemi profondamente differenti gli uni dagli altri. In TTA-UC radiazione ad alta energia è emessa dalla ricombinazione radiativa dello stato di singoletto eccitato di una molecola emettitore, popolato precedentemente dall'annichilazione dei tripletti di due emettitori. Un sensibilizzatore immagazzina la luce incidente a bassa energia e trasferisce l'eccitazione agli emettitori tramite trasferimento di energia alla Dexter. Poiché il suo funzionamento si basa su tripletti mestastabili, TTA-UC può essere altamente efficiente anche in condizioni di luce non coerente e a bassa energia. Come tale, è particolarmente adatto per dispositivi che sfruttano l'energia solare poiché è in grado di aumentarne l'efficienza di conversione limitando le perdite per trasmissione. Mi sono concentrata su due problemi importanti che tuttora limitano l'impiego di materiali che attuano TTA-UC (upconverters), ossia la limitata capacità di immagazzinare energia dei comuni sensibilizzatori organici e le scarse prestazioni di TTA-UC in upconverters a stato solido, i quali sono più adatti per applicazioni tecnologiche rispetto a sistemi liquidi. Per risolvere il primo problema ho investigato sensibilizzatori ibridi, composti da nanostrutture a semiconduttore decorate con molecole organiche, con ampio assorbimento. Nanocristalli di CdSe drogati con cationi d'oro e decorati con acido antracenico carbossilico si sono dimostrati essere sensibilizzatori ibridi efficienti ed innovativi. Il drogante introduce nel gap energetico dei nanocristalli livelli localizzati su cui le lacune si localizzano sulla scala dei picosecondi, più velocemente dell'estrazione di lacune sul livello HOMO dei leganti. Con tale strategia ho raggiunto l'efficienza di UC del 12%, record per sistemi ibridi. Ho poi mostrato come le proprietà superficiali e fotofisiche di nanoplatelets di CdSe le rendano ottimali candidati in sensibilizzatori ibridi. Ho mostrato che il ricoprimento delle superfici non è omogeneo, ma procede ad isole e l'interazione di "π- π stacking" porta alla formazione di aggregati sulle superfici delle nanoplatelets, con il risultato di ridurre l'energia dei tripletti dei leganti con profonde ripercussioni sulle prestazioni di TTA-UC e sulla scelta della specie emettitrice. Riguardo al secondo problema, ho studiato due upconverters a stato solido, polimeri vetrosi nanostrutturati che mostrano proprietà macroscopiche simili ma realizzati con tecniche differenti. Essi presentano domini liquidi di dimensione inferiore a 50 nm dove le specie che attuano TTA-UC si accumulano, racchiuse in una matrice rigida polimerica che fornisce protezione da ossigeno e qualità ottica eccellenti e stabilità a lungo termine. Il confinamento molecolare permette di aumentare la densità locale di eccitoni aumentando l'efficienza di UC a basse potenze grazie alle ridotte distanze intermolecolari e all'attivazione del regime di TTA-UC confinato.Ho inoltre studiato un nuovo emettitore derivato da perilene, realizzato con lo scopo di aumentarne l'efficienza di fluorescenza. Grazie a questo emettitore ho raggiunto l'efficienza record di UC di 42%, dovuta proprio alla struttura molecolare dell'emettitore che permette di limitare la formazione di aggregati, garantendo un'eccellente efficienza di generazione di singoletti tramite TTA. Infine, ho presentato una prospettiva riguardo alle prestazioni che possono essere raggiunte combinando le due tematiche trattate, ossia inserendo sensibilizzatori ad ampio assorbimento in polimeri nanostrutturati. Trovando il giusto compromesso tra taglia dei domini liquidi e distribuzione dell'energia di eccitazione si raggiungerebbe la massima efficienza di UC a potenze minori dell'irradianza solare, promuovendo lo sviluppo di upconverters a stato solido per tecnologie a energia solare
In my PhD project, I investigated the photophysical process of photon upconversion assisted by triplet-triplet annihilation (sTTA-UC) through spectroscopy studies in a variety of systems, profoundly different on many levels. In sTTA-UC high energy radiation is emitted from the fluorescent recombination of the excited singlet of an emitter molecule, previously populated via annihilation of the metastable triplet states of two emitters. This is a sensitized process since a sensitizer is necessary to harvest the low energy incident light and to transfer the stored energy to the emitters via Dexter energy transfer. Because its functioning relies on long-lived metastable triplets, this process can be highly efficient also under low power, noncoherent light. As such, sTTA-UC is particularly suited for solar applications as it can increase the conversion efficiency by reducing transmission losses. During my studies, I focused on addressing two crucial issues that still limit the application of upconverters in solar technologies, i.e. the limited storage ability of common organic sensitizers and the poor sTTA-UC performance in solid-state upconverters, which are intrinsically better suited than liquid solutions for technological applications. To solve the first problem, I investigated hybrid sensitizers, composed of semiconductor nanostructures decorated with conjugated organic ligands characterized by broadband absorption. CdSe nanocrystals (NCs) doped with gold cations and decorated with 9-anthracene carboxylic acid demonstrated to be efficient innovative broadband hybrid sensitizers. The doping strategy inserts into the NCs energy gap localized hole-accepting states where the holes localize on the picosecond timescale, outpacing hole transfer to the ligand HOMO. With this strategy, I achieved the UC efficiency of 12%, the record performance obtained so far for hybrid upconverters. I then discussed how the CdSe nanoplatelets surface and photophysical properties make them potential optimal light harvesters. My studies on the nanoplatelets-to-ligands energy transfer dependency on the surface ligand density revealed that the surface coverage is not homogeneous but proceeds in an island-like way promoted by π- π stacking and results in the formation of ligands aggregates on the nanoplatelets surfaces, which causes a redshift of the ligand triplet energy with critical repercussions on the sTTA-UC performance and on the emitter selection. To address the second issue, I investigated two solid-state upconverters, i.e. nanostructured glassy polymers that show similar macroscopic properties but fabricated via different approaches. They both feature liquid droplets of mean size less than 50 nm where the upconverting dyes accumulate, embedded in a rigid polymer matrix that grants excellent oxygen protection and optical quality and long-term stability. The dyes confinement allows to increase the effective local excitons density resulting in an enhanced UC efficiency at low excitation intensities, thanks to the reduced intermolecular distances and the activation of the confined sTTA-UC regime. I also introduced a new perylene derivative as emitter, specifically designed to prevent molecular aggregation to maximize its fluorescence efficiency. By employing this emitter, I achieved the record UC efficiency of 42%, which directly stems from the emitter molecular structure, as it limits the formation of aggregates, while guaranteeing excellent singlet generation efficiency upon TTA. I finally presented a perspective of the performances that can be achieved by combining the two topics considered, i.e. loading broadband sensitizers in nanostructured polymers. I highlighted that if the best trade-off between nanostructure size and energy distribution is met the maximum UC efficiency can be achieved at excitation powers orders of magnitude lower that the solar irradiance, therefore promoting the development of real-world solid-state upconverters.

With the ever-advancing technology, there is an incessant need for reliable electrochemical energy storage (EES) components that can provide desired energy and power. At the forefront of EES systems are electrochemical capacitors (ECs), also known as supercapacitors that typically have higher power and superior cycle longevity but lower energy densities than their battery counterparts. One of the routes to achieve higher energy density for ECs is using the hybrid EC configuration, which typically utilizes a redox electrode coupled with a counter double-layer type electrode. In this dissertation, both scale-up (coin-cell type) as well as scale-down (on-chip miniaturized) hybrid ECs were designed, constructed and evaluated. The first part of the dissertation comprised material identification, syntheses, and electrochemical analyses. Lithium titanate-anatase titanium oxide (Li4Ti5O12-TiO2) composites were synthesized via electrostatic spray deposition (ESD) and characterized in both half-cell and full-cell assembly against lithium and nanostructured carbon based counter electrodes, respectively. The second redox type material studied for hybrid electrochemical capacitors was ESD derived manganese oxide (MnOx). The MnOx electrodes exhibited a high gravimetric capacitance of 225F g-1 in aqueous media. Further improvement in the rate handling of the MnOx electrodes was achieved by using CNT additives. The MnOx-CNT composites were tested in full-cell assembly against activated carbon counter electrodes and tested for different anode and cathode mass ratios in order to achieve the best energy-power tradeoff, which was the second major goal of the dissertation. The optimized hybrid capacitor was able to deliver a high specific energy density of 30.3 Wh kg-1 and a maximal power density of 4kW kg-1. The last part of the dissertation focused on a scale-down miniaturized hybrid microsupercapacitor; an interdigitated electrode design was adopted in order to shorten the ion-transport pathway, and MnOx and reduced graphene oxide (rGO) were chosen as the redox and double layer components, respectively. The hybrid microsupercapacitor was able to deliver a high stack energy density of 1.02 mWh cm-3 and a maximal stack power density of 3.44 W cm-3, both of which are comparable with thin-film batteries and commercial supercapacitor in terms of volumetric energy and power densities.

Im Fokus dieser Arbeit standen zwei Ziele. Zum einem war es Forschungsgegenstand, dass Konzept der Zwillingspolymerisation auf germaniumhaltige, molekulare Vorstufen wie zum Beispiel Germylene, spirozyklische Germaniumverbindungen und molekulare Germanate zu erweitern und somit organisch-anorganische Komposite beziehungsweise Hybridmaterialien darzustellen. Dazu wurden neuartige Germaniumalkoxide auf der Basis von Benzylalkoholaten, Salicylalkoholaten sowie Benzylthiolaten synthetisiert, charakterisiert und auf ihre Fähigkeit Komposite beziehungsweise Hybridmaterialien über den Prozess der Zwillingspolymerisation zu erhalten studiert. Ein zweites Ziel dieser Arbeit war es, Beziehungen zwischen der Struktur und der Reaktivität dieser molekularen Vorstufen sowie deren Einfluss auf die Eigenschaften der erhaltenen Polymerisationsprodukte zu identifizieren und systematisch zu untersuchen. Hierfür wurden zum einen verschiedene Substituenten, welche unterschiedliche elektronische sowie sterische Eigenschaften aufweisen, an den aromatischen Einheiten der molekularen Vorstufen eingeführt. Die Effekte der Substituenten auf den Prozess der Zwillingspolymerisation und auf die Eigenschaften der Komposite beziehungsweise Hybridmaterialien wurden für die Verbindungsklasse der Germanium(II)salicylalkoholate, der molekularen Germanate sowie der spiro-zyklischen Siliziumsalicylalkoholate untersucht. Spirozyklische Siliziumsalicylalkoholate, wie zum Beispiel 4H,4’H-2,2‘-Spirobi[benzo[d][1,3,2]dioxasilin], wurden im Rahmen dieser Arbeit mit einbezogen, da sie aufgrund ihres nahezu idealen Zwillingspolymerisationsprozesses geeignete Modelverbindungen für Reaktivitätsstudien darstellen. Zudem wurde der Einfluss der Substituenten auf die Charakteristika der aus den Kompositen beziehungsweise Hybridmaterialien erhaltenen Folgeprodukte (poröse Kohlenstoffmaterialien und oxydische Materialien) studiert. Des Weiteren wurde eine Serie von spirozyklischen Germaniumthiolaten, welche isostrukturell zu 4H,4’H-2,2‘-Spirobi[benzo[d][1,3,2]dioxasilin] sind, synthetisiert, um systematisch den Einfluss der Chalkogenide, Sauerstoff und Schwefel, in benzylständiger sowie phenylständiger Position auf deren Reaktionsvermögen im Polymerisationsprozess zu untersuchen. Die experimentellen Ergebnisse zu den Struktur-Reaktivitätsbeziehungsstudien wurden, soweit es jeweils durchführbar war, mittels quantenchemische Rechnungen validiert und die daraus gezogenen Schlüsse in die Diskussion zur Interpretation der experimentellen Ergebnisse mit einbezogen.

This thesis considers a nanotechnology approach based on the production of metals pre-treatments and organic coatings (a complete protection system at all) designed from the nanoscale. The final aim is to develop protection systems with improved corrosion protection properties and a low environmental impact. In particular, multifunctional silane hybrid molecules were used to design sol-gel pre-treatments for metals and to modify the inner structure of UV curable waterborne organic coatings. In the first part of this thesis thin (hundreds of nanometers) sol-gel films consisting of an experimental mixture of hybrid silicon alkoxides molecules were applied onto aluminium and hot dip galvanized (HDG) steel for the development of effective and environmentally friendly corrosion protection systems A chemical and electrochemical characterization of the sol-gel films highlighted their good corrosion protection properties both for aluminium and HDG steel. To test the effectiveness of the sol-gel coatings as coupling agent between metallic substrates and organic coatings (paints) both a powder coating paint and a cataphoretic coating paint were applied on the silane pre-treated substrates. The electrochemical measurements and the accelerated tests carried out on these protection systems proved the capability of these sol-gel conversion coatings to improve the corrosion protection properties of the traditional protective cycles. The performance of the silane pre-treatments was also compared to commonly used surface conversion coatings for metals. The result of this comparison evidenced that the corrosion protection properties ensured by the sol-gel conversion treatment is comparable or higher than most of the commonly used pretreatments. A study about the incorporation of inorganic nanoparticles into these sol-gel films gave evidences of an improved corrosion resistance due to the addition of certain amount of montmorillonite nanoparticles in the sol-gel matrix. The same hybrid silicon alkoxide molecules used to perform the pre-treatments were used modify the inner structure of UV curable waterborne coatings in order to improve the corrosion protection properties maintaining the environmental compatibility of the protecting system. The design, application and characterisation of urethane, acrylic and epoxy waterborne UV curing coatings modified with the hybrid silicon molecules in order to obtain nanostructured waterborne films with improved corrosion resistance and thermomechanical properties were studied. The characterization proved the great potential of the silicon alkoxide molecules as a tool to modify the properties of the organic matrix of the paint: silicon alkoxides can promote the self assembly of inorganic nanoparticles into the matrix or can act as an effective coupling agent between inorganic nanoparticles and the polymeric matrix. Silicon alkoxide molecules were proved to be an efficient tool to design a protection system from the nanoscale leading to the prospective of an accurate control of the overall properties of the macroscopic systems.

This dissertation presents the design of organic/inorganic hybrid 2D and 3D nanostructured arrays via controlled assembly of nanoscale building blocks. Two representative nanoscale building blocks such as carbon nanotubes (one-dimension) and metal nanoparticles (zero-dimension) are the core materials for the study of solution-based assembly of nanostructured arrays. The electrical, mechanical, and optical properties of the assembled nanostructure arrays have been investigated for future device applications. We successfully demonstrated the prospective use of assembled nanostructure arrays for electronic and sensing applications by designing flexible carbon nanotube nanomembranes as mechanical sensors, highly-oriented carbon nanotubes arrays for thin-film transistors, and gold nanoparticle arrays for SERS chemical sensors. In first section, we fabricated highly ordered carbon nanotube (CNT) arrays by tilted drop-casting or dip-coating of CNT solution on silicon substrates functionalized with micropatterned self-assembled monolayers. We further exploited the electronic performance of thin-film transistors based on highly-oriented, densely packed CNT micropatterns and showed that the carrier mobility is largely improved compared to randomly oriented CNTs. The prospective use of Raman-active CNTs for potential mechanical sensors has been investigated by studying the mechano-optical properties of flexible carbon nanotube nanomembranes, which contain freely-suspended carbon nanotube array encapsulated into ultrathin (<50 nm) layer-by-layer (LbL) polymer multilayers. In second section, we fabricated 3D nano-canal arrays of porous alumina membranes decorated with gold nanoparticles for prospective SERS sensors. We showed extraordinary SERS enhancement and suggested that the high performance is associated with the combined effects of Raman-active hot spots of nanoparticle aggregates and the optical waveguide properties of nano-canals. We demonstrated the ability of this SERS substrate for trace level sensing of nitroaromatic explosives by detecting down to 100 zeptogram (~330 molecules) of DNT.

This thesis considers a nanotechnology approach based on the production of metals pre-treatments and organic coatings (a complete protection system at all) designed from the nanoscale. The final aim is to develop protection systems with improved corrosion protection properties and a low environmental impact. In particular, multifunctional silane hybrid molecules were used to design sol-gel pre-treatments for metals and to modify the inner structure of UV curable waterborne organic coatings. In the first part of this thesis thin (hundreds of nanometers) sol-gel films consisting of an experimental mixture of hybrid silicon alkoxides molecules were applied onto aluminium and hot dip galvanized (HDG) steel for the development of effective and environmentally friendly corrosion protection systems A chemical and electrochemical characterization of the sol-gel films highlighted their good corrosion protection properties both for aluminium and HDG steel. To test the effectiveness of the sol-gel coatings as coupling agent between metallic substrates and organic coatings (paints) both a powder coating paint and a cataphoretic coating paint were applied on the silane pre-treated substrates. The electrochemical measurements and the accelerated tests carried out on these protection systems proved the capability of these sol-gel conversion coatings to improve the corrosion protection properties of the traditional protective cycles. The performance of the silane pre-treatments was also compared to commonly used surface conversion coatings for metals. The result of this comparison evidenced that the corrosion protection properties ensured by the sol-gel conversion treatment is comparable or higher than most of the commonly used pretreatments. A study about the incorporation of inorganic nanoparticles into these sol-gel films gave evidences of an improved corrosion resistance due to the addition of certain amount of montmorillonite nanoparticles in the sol-gel matrix. The same hybrid silicon alkoxide molecules used to perform the pre-treatments were used modify the inner structure of UV curable waterborne coatings in order to improve the corrosion protection properties maintaining the environmental compatibility of the protecting system. The design, application and characterisation of urethane, acrylic and epoxy waterborne UV curing coatings modified with the hybrid silicon molecules in order to obtain nanostructured waterborne films with improved corrosion resistance and thermomechanical properties were studied. The characterization proved the great potential of the silicon alkoxide molecules as a tool to modify the properties of the organic matrix of the paint: silicon alkoxides can promote the self assembly of inorganic nanoparticles into the matrix or can act as an effective coupling agent between inorganic nanoparticles and the polymeric matrix. Silicon alkoxide molecules were proved to be an efficient tool to design a protection system from the nanoscale leading to the prospective of an accurate control of the overall properties of the macroscopic systems.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2014.
Vita. Cataloged from PDF version of thesis.
Includes bibliographical references.
The development of technology and population growth will demand 56 percent increase of the energy consumption in 30 years. An efficient energy storage system will be necessary to meet these increased needs to deliver and store the energy. After the first release of commercial Li ion batteries in 1991, they were widely adapted to various applications from small portable devices to electric vehicles. However, the current Li ion battery can only store -250 Wh/kgcell of gravimetric energy, a far limited energy storage capability especially to replace gasoline in powering vehicles. This limitation originated either from the incomplete utilization of active materials or their low theoretical energy density. Therefore, a rational design of electrodes as well as the new battery chemistry needs to be investigated to further develop the current energy storage system. In this thesis, high theoretical energy density batteries are investigated. First, the power performance of conversion reaction cathode materials, bismuth oxyfluorides, was improved. By rationally designing genetic sequences of the M13 virus, graphene sheets were homogeneously distributed throughout bismuth oxyfluorides cathodes as conducting paths. Second, large surface area cathodes were developed with virus-templated manganese oxide nanowires. These electrodes were applied to Li-0₂ battery systems to achieve large capacities and a long cycle life. Furthermore, the chemical composition of virus-templated inorganic nanowires was easily tuned to study the catalytic behavior of transition metal oxides in Li-0₂ batteries. These bio-directed methods to develop high performance battery electrodes, in conclusion, suggest an eco-friendly and cost effective way to manufacture energy storage devices. The design strategy established in this thesis could be applied not only to batteries but also to electronic devices requiring sophisticated nanoscale controls.
by Dahyun Oh.
Ph. D.

Polymer-nanoplatelet hybrid membranes show promise as the next generation of membranes, but in order to make these realizable, methods to produce these materials on a large scale are necessary. Some authors have successfully produced these types of gas separation membranes. Typically these reports have utilized melt blending and in situ polymerization. Few, however, have utilized solution blending for creating membranes via phase inversion (asymmetric membranes). And to date, there have not been any reports regarding the fabrication of asymmetric membranes containing nanoplatelet filler materials. In this work we have developed a solution-based procedure for the formation of hybrid polymer-nanoplatelet dopes for dense film and asymmetric hollow fiber membrane formation. Dense film membrane studies were used to prove the effectiveness of our exfoliation and dispersion process developed for this work. Permeation measurements showed the hybrid membranes have desirable transport properties that are on par with mathematical model predictions. Additionally, TEM characterization provided strong evidence supporting the efficacy of our preparation procedures to produce an exfoliated system of nanoplatelets. We also showed that these procedures are applicable to different polymer systems (cellulose acetate and Torlon) of commercial relevance. Demonstrating the successful production of dense films set the stage for asymmetric hollow fiber membrane formation. We report the first production of asymmetric hollow fiber membranes containing nanoplatelet fillers; indicating that the process can be applied in a realistic membrane formation platform. These accomplishments serve as the groundwork for future nanocomposite formation.

Thesis (PhD)--Stellenbosch University, 2012.
ENGLISH ABSTRACT: The use of co-sonication (ad-miniemulsion) polymerisation for the preparation of highly filled polymer/clay hybrid latexes is described. Laponite (Lap) content levels in the range of 10–50 wt% were effectively encapsulated in both polystyrene (PS) and polystyrene-co-butyl acrylate nanoparticles (PSBA). The latex and film morphological features of these highly filled hybrid materials were evaluated using both transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). PS/Lap latexes exhibited mixed particle morphologies from armoured particles at low clay content (10 wt%) to encapsulated particles at high clay content (50 wt%). However, PSBA/Lap hybrid latexes exhibited predominantly crumpled particle morphologies through the clay content studied. The resultant polymer/clay nanocomposites (PCNs) of PS/Lap and PSBA/Lap exhibited either partially or fully exfoliated structures. It was found that generally these PCNs exhibited superior properties than the neat polymers except for thermal stability properties. As much as 5000% storage modulus improvement was observed for both PS/Lap and PSBA/Lap relative to the neat polymers. The Tg of PSBA/Lap showed a 14 ºC shift towards higher temperature. Rheology tests showed that the resultant PCNs exhibited solid-like viscoelastic behaviour. The encapsulation of montmorilonite clay (MMT) using the ad-miniemulsion procedure was found to be ineffective. The MMT platelets remained adhered onto the polymer particles surfaces. Ineffective encapsulation of MMT platelets was attributed to their dimensions which were either large or equal to those of the polymer particles. Despite the ineffective encapsulation, the MMT platelets were completely exfoliated within the final PCNs as shown by both SAXS and TEM. Overall, the ad-miniemulsion was found to be an effective method for the preparation of highly filled water based polymer/clay hybrid latexes. However, the clay encapsulation in polymer particles and the extent of clay exfoliation were found to be dependent on clay dimensions relative to the polymer particles, monomer/clay compatibility and clay modifier reactivity. It was found that clay dimensions and use of clay modifier that improve monomer/clay compatibility enhances encapsulation. On the other hand, the modifier reactivity influenced the extent of clay exfoliation in the final PCN, irrespective of clay encapsulation in the polymer particles. These findings were based on comparative studies conducted on the use of Lap versus MMT and non-reactive modifier versus reactive modifier during ad-miniemulsion polymerisation.
AFRIKAANSE OPSOMMING: Die gebruik van mede-sonikasie (ad-miniemulsie) polimerisasie vir die voorbereiding van die hoogsgevulde polimeer/klei hibriedlatekse word beskryf. Laponiet (Lap) vlakke in hoeveelhede van 10-50 gew% is effektief ge-inkapsuleer in beide polistireen (PS) en polistireen-ko-butielakrilaat nanopartikels (PSBA). Die morfologiese eienskappe van die latekse en films van hierdie hoogsgevulde hibried materiale is geëvalueer deur beide transmissie-elektronmikroskopie (TEM) en klein-hoek X-straal-verstrooiing (SAXS). PS/Lap latekse het gemengde partikel morfologieë getoon, bv. vanaf gepantserde partikels by lae kleihoeveelhede (10 gew%) tot ge-inkapsuleerde partikels by hoë kleihoeveelhede (50 gew%). Daarteenoor het PSBA/Lap hibriedlatekse „n oorwegend verkreukelde partikelmorfologie getoon vir die reeks kleihoeveelhede wat bestudeer is. Die gevolglike polimeer/klei nanokomposiete (PKNs) van PS/Lap en PSBA/Lap het, óf gedeeltelike, óof ten volle geëksfolieerde strukture getoon. Oor die algemeen is bevind dat hierdie PKNs beter eienskappe as die suiwer polimere getoon het, behalwe vir die termiese stabiliteit eienskappe. Verbeteringe van soveel as 5000% in die stoormodulus is waargeneem vir beide PS/Lap en PSBA/Lap met betrekking tot die suiwer polimere. Die Tg van PSBA/Lap het „n 14°C verskuiwing na „n hoër temperatuur getoon. Reologiese toetse het getoon dat die gevolglike PKNs vastestofagtige visko-elastiese gedrag getoon het. Die inkapsulering van montmorilonietklei (MMT), deur middel van die ad-miniemulsieproses, was ondoeltreffend. Die MMT plaatjies het agtergebly op die oppervlaktes van die polimeerpartikel. Oneffektiewe inkapsulering van MMT plaatjies is toegeskryf aan hul grootte, wat óf groter, óf gelyk was aan dié van die polimeerpartikels. Ten spyte van die oneffektiewe inkapsulering was al die MMT plaatjies in die finale PKNs geëksfolieer soos deur beide SAXS en TEM aangedui. Oor die algemeen is bevind dat ad-miniemulsie „n effektiewe metode is vir die voorbereiding van hoogsgevulde waterbasis polimeer/klei hibriedlatekse. Daar is egter bevind dat klei inkapsulering in polimeerpartikels asook die omvang van klei eksfoliëring, afhanklik is van die klei afmetings in verhouding tot die polimeerpartikels, monomeer/klei verenigbaarheid en die reaktiwiteit van die kleiwysiger. Daar is bevind dat die klei afmetings en die gebruik van „n kleiwysiger wat die monomeer/klei verenigbaarheid verbeter, inkapsulering bevorder. Aan die ander kant het die reaktiwiteit van die kleiwysiger die omvang van klei eksfoliëring in die finale PKNs beïnvloed, ongeag van klei inkapsulering in die polimeerpartikels. Hierdie bevindings is gebaseer op vergelykende studies van die gebruik van Lap teenoor MMT en nie-reaktiewe wysiger teenoor reaktiewe wysiger gedurende ad-miniemulsiepolimerisasie.

La plasmonique hybride est un sujet d’actualité qui exploite des interactions physiques entre nano-objets métalliques et d’autres nanomatériaux. En bénéficiant des propriétés de chacun de leurs constituants, les nanostructures hybrides sont utilisées dans de nombreuses applications comme la détection d’espèces bio-chimiques. Dans cette thèse, nous présentons une nouvelle nanostructure hybride polymère/metal qui est non seulement utilisée comme nano-émetteur anisotrope qui s’avère aussi être un outil puissant de caractérisation du champ proche optique.La fabrication de cette nouvelle nanostructure est basée sur une approche de par photopolymérisation à l’échelle nanométrique. Cette technique, en comparaison aux méthodes traditionnelles de caractérisation, ne fournit pas seulement l’image de la distribution du champ, mais permet aussi des mesures quantitatives des plasmons de surface avec une résolution sub -5nm, incluant une description fine de la décroissance exponentielle des ondes évanescentes impliquées.A l’aide du mode plasmon dipolaire, une distribution anisotrope de matériau organique est intégrée dans le voisinage de la nanoparticule métallique. Avec une haute concentration de molécules de colorant dans le polymère, l’intensité des signaux de fluorescence et Raman du nano-émetteur hybride dépend de la polarisation incidente. À notre connaissance, il s’agit de la première réalisation d’un nano-émetteur dont le milieu à gain présente une distribution spatiale complexe le rendant sensible à la polarisation
Hybrid plasmonics has given rise to increasing interest in the context of the interaction between metal nano-objects and other materials. By benefiting from each of its constituents, hybrid nanostructures are commonly adopted in studies and optimization of biological and chemical sensors, nanoparticle with high plasmon resonance tunability, and nano-emitters. This PhD thesis presents a hybrid nanostructure of photopolymer/metal nanoparticle that is used as a near-field characterizing tool and as an anisotropic nano-emitter.The fabrication of this hybrid nanostructure is a near-field imprinting process based on nanoscale photopolymerization. This technique, compared with traditional near-field characterization methods, provides not only the image of the field distribution, but also enables quantification of the surface plasmon properties with sub-5nm resolution and reproduction of the exponential decay of the near-field.Under dipolar mode plasmon, the photopolymer was created anisotropically in the vicinity of the metal nanoparticle. With high concentration of dye molecules trapped in the polymer, the hybrid nano-emitter displays surface enhanced fluorescence and Raman signal that is dependent on the incident polarization. To our knowledge, this is the first achievement of the anisotropic nano-emitter based on the inhomogeneous distribution of the active molecule

Los materiales compuestos nanoestructurados son considerados una opción prometedora para la concepción de materiales multifuncionales. Sin embargo, la falta habitual de interacción entre los componentes orgánicos e inorgánicos en los materiales híbridos nanoestructurados comporta unas propiedades macroscópicas anisotrópicas que limitan su uso. Por ello, se hace necesario el diseño de la interfase formada entre los componentes mencionados a fin de mejorar sus prestaciones. En esta Tesis Doctoral se ha optado por el uso de dióxido de carbono supercrítico (scCO2) para la modificación superficial de nanopartículas inorgánicas y para la preparación de materiales híbridos nanoestructurados. Estos procesos supercríticos, diseñados como sostenibles, se proponen como sustitutos de técnicas convencionales que empleen disolventes orgánicos. El tratamiento superficial de nanopartículas de dióxido de titanio (TiO2) con octiltrietoxisilano se ha empleado como sistema de estudio para evaluar el uso de recubrimientos de alcoxisilanos bifuncionales como promotores de adhesión de partículas inorgánicas nanométricas. El scCO2 se emplea como disolvente del alcoxisilano para la silanización del TiO2. También se han llevado a cabo estudios fundamentales de solubilidad de octiltrietoxisilano en CO2 y de la cinética del proceso de silanización del TiO2. La modulación de las propiedades fisicoquímicas del scCO2 con la presión y la temperatura permite el control de las características del recubrimiento con silano. El proceso de silanización supercrítico se ha extendido a diferentes sistemas alcoxisilano-nanopartículas inorgánicas. Asimismo, se ha evaluado la tecnología de scCO2 para la preparación de materiales híbridos nanoestructurados que contengan nanopartículas inorgánicas silanizadas. El tratamiento superficial de las nanopartículas favorece la distribución homogénea de éstas en el material híbrido y mejora la interacción relleno-matriz orgánica. Se han procesado matrices biopoliméricas de interés en ingeniería tisular, compuestas de ácido poliláctico o la mezcla iv polimetilmetacrilato/policaprolactona, con adiciones de nanopartículas de TiO2 o hidroxiapatita, respectivamente. Para su procesado, se ha empleado scCO2 como no-disolvente utilizando la técnica Particles from a Compressed Anti-Solvent (PCA). Además, se han preparado partículas híbridas formadas por una mezcla lipídica de aceite de ricino hidrogenado y glicerilmonoestearato con adiciones de TiO2 y cafeína, con posibles aplicaciones en cremas para uso tópico. Estas partículas sólidas lipídicas se han obtenido usando la técnica Particles from Gas Saturated Solutions (PGSS) que emplea scCO2 como soluto. Por último, el proceso de silanización supercrítico se ha ensayado para materiales híbridos complejos multiescalados. Se han procesado materiales de base cemento empleando un proceso supercrítico de carbonatación-silanización en dos etapas. Primero, el cemento se carbonata de manera acelerada usando scCO2 como agente de carbonatación. Este cemento, ya carbonatado, se somete, finalmente, a un tratamiento hidrofóbico mediante silanización supercrítica, para su posible aplicación en confinamiento de residuos peligrosos en ambientes húmedos o como material de construcción duradero.
Nowadays, society is asking for a global changing in the way of manufacturing goods in a more sustainable manner. Indeed, the weight of the classical factors (cost, quality, appearance) influencing the acceptance of a certain good in the market have currently changed. Manufacturing requirements and regulations concerning environment protection (e.g., resource consumption, sustainability, toxicity, CO2 footprint, recycling potential) and quality features (e.g., product guarantees, durability against aggressive environments, corporate vision) are aspects of increasing concern. The competitive position of a company is influenced by seizing the opportunities and challenges and by managing the risks that the changeable market has. As a consequence, the industry is continuously looking for smart and innovative solutions for the design and manufacturing of materials with novel properties and increased added value, and for the production of materials already existing in the market in a more efficient manner. Nanostructured hybrid composites have emerged as a promising class of innovative materials for many industrial sectors (e.g., energy, optoelectronics, biomedicine, cosmetics). The multicomponent composition of these materials provides them with unique properties arising from the synergistic combination of the characteristics of their individual components structured at the nanolevel. Nevertheless, in numerous hybrid materials, the lack of coupling or bonding between the components often leads to anisotropic macroscopic properties, limiting their use. Hence, the interaction at the interphase between hybrid components must be properly engineered to enhance materials properties. In this PhD Thesis, the quest for sustainable and environmentally friendly processes led to the use of supercritical carbon dioxide (scCO2) for both the surface modification of nanometric inorganic particles and the preparation of nanostructured hybrid materials. These processes are designed for the replacement of conventional methods using organic solvents. vi Bifunctional alkoxysilane molecules, acting as adhesion promoters, are, herein, investigated for the surface modification of nanometric inorganic particles. The surface treatment of titanium dioxide (TiO2) nanoparticles with octyltriethoxysilane is taken as the model system for study. In terms of processing, scCO2 is used as the solvent of choice for alkoxysilanes for the surface modification of TiO2. Fundamental studies on the solubility of the used silane in CO2 in the pressure range 8-18 MPa at two different temperatures (318 and 348 K) and on the kinetics of the TiO2 silanization process are performed. For the scCO2-aided silanization process, studies are conducted to ascertain the effects and interactions of the operating variables on the properties of the final material. Results show that the tunable physicochemical properties of scCO2 with pressure and temperature (e.g., density, solvation power) allows the engineering control of the characteristics of the silane coating. Examples of the extension of the application of the supercritical silanization process to other sets of alkoxysilanes and inorganic nanoparticles are also presented. The preparation of hybrid materials including silanized inorganic nanoparticles and organic matrices is further tested using scCO2 technology. Surface treated nanoparticles are used to facilitate the homogeneous distribution of the nanoparticles within the matix and to improve the inorganic filler-organic matrix interaction. Biopolymeric matrices of either poly(L-lactic acid) (L-PLA) or the blend poly(methylmethacrylate)/poly(ε-caprolactone) (PMMA/PCL) loaded with nanometric titanium dioxide or hydroxyapatite, respectively, are prepared. To obtain these hybrid materials, scCO2 is employed as an anti-solvent, using the Particles from a Compressed Anti-Solvent (PCA) technique. Studies are performed to pursue the effect of the processing conditions on the morphology of the precipitated hybrid materials. The resulting material, obtained in the form of fibers, has suitable properties for its potential application in tissue engineering. In a different system, hybrid particles composed of a lipidic matrix (hydrogenated castor oil/glyceryl monostearate) loaded with silanized titanium dioxide and caffeine are prepared. The Particles from Gas Saturated Solutions (PGSS) technique, assisted by the use of scCO2 as a solute, is employed for the production of these solid lipid particles. The obtained hybrid material is evaluated concerning the drug carrier and release ability and the UV-shielding capacity. The UV-light protection and photoaging prevention capacity of the lipid-based hybrid material provide excellent properties for the use of these particles in the formulation of sunscreens and pharmaceutical dermal products. vii Finally, the possibility of extending the supercritical silane treatment to multiscale complex hybrid materials is assessed. The technology based on the use of scCO2 is presented for the two-step carbonation-silanization process of cement-based materials. In the first step, the carbonation of cement is accelerated using scCO2 as the carbonation agent. The effects of the cement formulation and process operation conditions on the microstructure and physicochemical properties of carbonated samples are evaluated. The carbonation process is followed by the hydrophobic treatment of the carbonated samples using a supercritical silanization method. The surface modification of carbonated cement with octyltriethoxysilane confers water repellence to the material. The carbonation-silanization process is scheduled and integrated to mitigate the consumption of raw materials and the use of facilities.

Various synthetic methods have been developed to produce metal nanostructures including copper and iron nanostructures. Modification of nanoparticle surface to enhance their characteristic properties through surface functionalization with organic ligands ranging from small molecules to polymeric materials including organic semiconducting polymers is a key interest in nanoscience. However, most of the synthetic methods developed in the past depend widely on non-aqueous solvents, toxic reducing agents, and high temperature and high-pressure conditions. Therefore, to produce metal nanostructures and their nanocomposites with a simpler and greener method is indeed necessary and desirable for their nano-scale applications. Hence the objective of this thesis work is to develop an environmentally friendly synthesis method to make welldefined copper and iron nanostructures on a large-scale. The size and shape-dependent optical properties, solid-state crystal packing, and morphologies of nanostructures have been evaluated with respect to various experimental parameters. Nanostructures of copper and iron were prepared by developing an aqueous phase chemical reduction method from copper(II) chloride and Fe(III) chloride hexahydrate upon reduction using a mild reducing agent, sodium borohydride, under an inert atmosphere at room temperature. Well-defined copper nanocubes with an average edge length of 100±35 nm and iron nanochains with an average chain length up to 1.70 μm were prepared. The effect of the molar ratios of each precursor to the reducing agent, reaction time, and addition rate of the reducing agent were also evaluated in order to develop an optimized synthesis method for synthesis of these nanostructures. UV-visible spectral traces and X-ray powder diffraction traces were obtained to confirm the successful preparation of both nanostructrues. The synthesis method developed here was further modified to make poly(3-hexylthiophene) coated iron nanocomposites by surface functionalization with poly(3-hexylthiophene) carboxylate anion. Since these nanostructrues and nanocomposites have the ability to disperse in both aqueous-based solvents and organic solvents, the synthesis method provides opportunities to apply these metal nanostructures on a variety of surfaces using solution based fabrication techniques such as spin coating and spray coating methods.

In this thesis it is discussed the effect of the low dimensionality on several physical properties of hybrid nanostructures for new generation photovoltaics. We investigated several hybrid and organic model systems, consisting of an organic polymer playing the role of electron donor and a low-dimension nanostructure (1D or 0D) which acts as electron acceptor and transporter. Model potential molecular dynamics has been used to characterize the polymer morphology onto the nanostructured substrates. In particular, the wrapping phenomena on one-dimensional structures (ZnO nanoneedles and carbon nanotubes) have been analyzed as a function of several physical variables such as temperature, substrate crystallography, polymer chain length and density. It has been thus possible to observe that wrapped configurations are only metastable on carbon nanotubes at room temperature and in absence of solvents. Nevertheless, wrapped configurations induced by the solvent can be frozen due to the interactions among neighboring polymer chains. According to this study, it is possible to enhance the polymer-nanotube alignment (and thus improving the polymer transport properties) through a suitable tuning of the synthesis parameters. Conversely, wrapped geometries are stable on ZnO nanoneedles, due to the small polymer mobility on the ZnO surface. The results obtained on the morphology of polymer-ZnO hybrids have then been used as a starting point to evaluate the electronic structure and the optical absorption properties. Hybrid models consisting in a 120-atoms ZnO nanoparticle and a set of oligothiophenes have been studied through the density functional theory, and the energy-level alignment has been obtained by using the Δ-self-consistent-field method. 120-atoms ZnO nanoparticles have been synthesized and found to be particularly stable. They therefore not only represent a useful model for computational studies, but are also of potential technological interest. An important result thus obtained is to demonstrate that the interaction between the two organic/inorganic moieties shifts the energy levels, giving rise to a nonstaggered junction. This phenomenon is not present in planar ZnO substrates, but it is rather induced by the nanostructuration of the hybrid polymer/metal oxide system. From the methodological standpoint, a simplified model to predict the energy-level alignment at the interface has been developed, allowing to spare computational resources. Finally, since the atomic configuration of the 120-atoms ZnO nanoparticles is unknown, we calculated the optical absorption spectra in the near ultra-violet of a set of (ZnO)60 isomers: this information can be compared to experimental spectroscopic data and can thus be used to elucidate the most abundant structure of this cluster. The results of the present work suggest that the use of nanostructures, although opening interesting technological possibilities such as increasing the donor/acceptor interface, also requires a critical readdressing of our understanding of morphologies and electronic level alignment in low-dimension systems.

Thesis (Ph. D.)--University of Alabama at Birmingham, 2007.
Title from PDF t.p. (viewed Feb. 3, 2010). Additional advisors: Derrick R. Dean, Sergey B. Mirov, Sergey Vyazovkin, Mary Ellen Zvanut. Includes bibliographical references (p. 122-145).

De nos jours, le domaine de la thermoplasmonique subit un développement très rapide. Ce domaine est basé sur l’amplification de la lumière absorbée par la nanoparticule métallique qui la transforme en une nanosource thermique optiquement activée. Un des défis qu’il faudra relever en thermoplasmonique est la manipulation et la valorisation de l’énergie thermique à petite échelle. De nouvelles techniques optiques permettent d’étudier les phénomènes thermiques liés aux nanoparticules plasmoniques. Ces techniques permettent de caractériser la distribution de température autour de nanoparticules métalliques avec néanmoins une résolution spatiale limitée par la diffraction. Dans cette thèse, nous présentons une nouvelle approche d’imagerie moléculaire, basée sur la nanopolymérisation amorcée thermiquement, pour caractériser le profil de chaleur au voisinage d’une nanoparticule métallique unique photo-excitée. Cette approche repose sur une formulation thermo-polymérisable caractérisée par une température seuil Ts qui est la température à partir de laquelle aura lieu la réaction de polymérisation. Nous développons ainsi des formulations présentant des Ts différentes. Après l’irradiation de la nanoparticule couverte par la solution thermo-polymérisable, la coquille de polymère créée est l’empreinte des zones où la photoconversion a induit une température supérieure à Ts. Nous démontrons la capacité de cette méthode à cartographier le champ thermique induit autour de la nanoparticule avec une résolution de l’ordre de dizaine de nanomètres (mieux que 35 nm)
Nowadays, the thermoplasmonic field undergoes a very interesting applications development thanks to the amplification of the light absorbed by the metal nanoparticle, which makes it an ideal nanosource of heat controlled by light. Because of this applications development, one of the challenges is to control and manipulate the thermal energy on a small scale.New optical techniques are dedicated to studying the thermal phenomenon induced by plasmonic nanoparticles. These techniques show different capacities to quantify and characterize the heat generated and the temperature distribution around nanoparticles. But the spatial resolution achieved is still limited by diffraction.In this thesis, we present a new molecular imaging approach, which is based on the nanopolymerization reaction thermally induced to characterize the heat profile in the vicinity of a single photoexcited nanoparticle. This approach is based on a thermo-polymerizable formulation with specific temperature threshold Tth (the temperature required to induce polymerization reaction). We develop formulations with different Tth. After irradiation of the nanoparticle covered by the thermo-polymerizable solution, the polymer shell created is the impression of areas where the photoconversion induced a temperature higher than Tth. We demonstrate the ability of this method to map the thermal field induced around the nanoparticle with a resolution better than 35 nm

Dans ce manuscrit, la synthèse et la caractérisation complète de différents matériaux hybrides dédiés à des applications dans le domaine optique ou thérapeutique sont décrites. Dans un premier temps, des systèmes macroscopiquement ordonnés sont obtenus par intercalation de colorants tels que le Styryl 722 ou la pyronine-Y dans plusieurs films à base d’argile de type smectite. Les films d’argile sont élaborés par spin-coating et les colorants intercalés par immersion des films dans les solutions de ces colorants. Les effets de l’argile sur les propriétés des colorants sont analysés en détail et leur orientation préférentielle dans l’espace inter-couches est étudié grâce à la réponse anisotropique des films en lumière linéairement polarisée. Dans la deuxième partie, la synthèse par chimie sol-gel de monolithes de silice de grande dimension contenant des colorants laser présentant une forte absorption et une émission de fluorescence dans le visible est abordée. Des colorants laser à l’état solide (SSDL) avec de bonnes stabilités photochimique, thermique et chimique sont ainsi proposés. Dans le troisième chapitre, la synthèse par voie sol-gel de nanoparticules de silice (NP) d’environ 50 nm de diamètre fonctionnalisées sur leur surface externe est ensuite décrite. Grâce à l’encapsulation de molécules de colorants fluorescents dans leur cœur et le greffage de photosensibilisateurs sur leur écorce, des nanoparticules biocompatibles adaptées à la bio-imagerie et la thérapie photodynamique (PDT) ont été préparées. Pour optimiser leurs performances, les propriétés photophysiques et plus particulièrement la production d’oxygène singulet d’une nouvelle série de photosensibilisateurs basés sur les chromophores de type PODIPY ont d’abord été étudiées en détail. A partir de ces résultats, des BODIPY particulièrement efficaces ont été greffés sur les nanoparticules de silice afin de les utiliser pour la PDT. Les propriétés photophysiques de ces matériaux ont été analysées par spectroscopie d’absorption et de fluorescence (stationnaire ou résolue en temps) et les rendements quantiques de production d’oxygène singulet déterminés par des méthodes directe (émission de luminescence de l’oxygène singulet à 1270 nm) ou indirecte (utilisation de sondes chimiques spécifiques à l’oxygène singulet). Par ailleurs les matériaux hybrides ont été complètement caractérisés par plusieurs techniques (SEM, TEM, XRD, XPS, IR, DLS, BET)
Along this manuscript different hybrid materials are synthesized and extensively characterized for several uses: from optical to therapeutic applications. First, by the intercalation of different dyes, styryl 722 and pyronine-Y into several smectite clay films, macroscopically ordered system are obtained. Clay films are elaborated by spin-coating technique and the dyes are intercalated by the immersion of clay thin films into dye solutions. The effect of clay on the dye properties is deeply analyzed and its preferential orientation in the interlayer space of the clay is studied by the anisotropic response of the films to the linear polarized light. Second, large silica monoliths with embedded laser dyes with strong absorption and fluorescence bands in different region of the Visible spectrum are attained by sol-gel chemistry to obtain solid-state dye laser (SSDL) with good photo, thermal and chemical stabilities. Third, silica nanoparticles (NP) with suitable size (50 nm) and functionalized external surface are also synthesised by sol-gel chemistry. Through the encapsulation of fluorescent dye molecules in their core and by the grafting of photosensitizers on their shell, biocompatible nanoparticles for bio-imaging and Photodynamic Therapy (PDT) applications are prepared. In order to optimize their properties, a careful investigation of the photophysical properties and mainly the singlet oxygen generation of a large range of new photosensitizers based on chromophores known as BODIPYs, is previously carried out. Based on these results, some efficient BODIPYs are selected for grafting on silica nanoparticles in order to use them for PDT. The photophysical properties of all these hybrid materials are analyzed by absorption and fluorescence (steady-state and time correlated) spectroscopies, and the singlet oxygen measurements are monitored by direct method (recording the singlet oxygen luminescence at 1270 nm) and by indirect method (using selective chemical probe). Moreover, the hybrid materials are fully characterized by several techniques such as, SEM, TEM, XRD, XPS, IR, DLS, BET

Organic photovoltaics (OPVs) have received a great deal of focus in recent years as a possible alternative to expensive silicon based solar technology. Current challenges for organic photovoltaics are centered around improving their lifetimes and increasing their power conversion efficiencies. One approach to improving the lifetime of such devices has been the inclusion of inorganic metal oxide layers, but interaction between the metal oxides and common conjugated polymers is not favorable. Here we present two methods by which the interactions between polythiophenes and nanostructured ZnO can be made to be more favorable. Using the first method, direct side on attachment of polythiophene to ZnO nanowires via chemical grafting, we demonstrate chemical linkage between the polymer and ZnO phases. The attachment was confirmed to affect the morphological properties of the polymer layer as well, inducing highly ordered regions of the polymer at the ZnO surface via chemical attachment and physical adsorption. Using the second method to improve polythiophene ZnO interactions, we have functionalized ZnO nanowires with organic molecules that favorably interact with conjugated polymer and organic solvents. Photovoltaic devices were made using a blended active layer of functionalized ZnO nanowires and P3HT. Electrical analysis of the resultant devices concluded that the devices were functional photovoltaic cells and isolated the dominant loss mechanisms for further device improvement.