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CAPITANI, CHIARA. « Synthesis of semiconductor colloidal nanocrystals with large Stokes-shift for luminescent solar concentrators ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2022. http://hdl.handle.net/10281/366195.
Texte intégralRésumé :
I concentratori solari luminescenti (LSCs) sono delle guide d’onda composti da una matrice polimerica drogata o ricoperta con fluorofori. La luce solare diretta e/o diffusa che penetra nella matrice è assorbita dai fluorofori e poi riemessa dagli stessi con energia minore. La luce emessa, grazie alla riflessione totale interna, propaga fino a raggiungere i bordi della guida d’onda dove è convertita in elettricità da celle fotovoltaiche poste sul perimetro della matrice.
L’efficienza del dispositivo è ridotta da numerosi processi di perdita, sia dovuti alla riflessione della matrice e al cono di fuga, sia quelli che dipendono dalle caratteristiche dei fluorofori, come il coefficiente di assorbimento, il quantum yield (QY) di fotoluminescenza (PL) e il riassorbimento.
Per minimizzare tali perdite, una buona alternativa ai tradizionali fluorofori sono i quantum dots (QDs) colloidali che presentano solitamente un elevato QY, un alto coefficiente di assorbimento e una lunghezza d’onda di emissione controllabile cambiando le dimensioni dei nanocristalli tramite modifiche dei parametri di sintesi. Inoltre, ingegnerizzando opportunamente i QDs, è possibile realizzare particelle con elevato Stokes-shift tra gli spettri di assorbimento ed emissione, in modo da ridurre quanto più possibile il riassorbimento.
Il progetto si è quindi focalizzato sullo sviluppo della sintesi di QDs, al fine di ottimizzare il QY di fotoluminescenza, la compatibilizzazione con la matrice polimerica e la fotostabilità, limitando comunque il riassorbimento.
Inoltre. la procedura di sintesi deve essere facilmente trasportabile su volumi industriali, per soddisfare il fabbisogno di produzioni di elevati metri quadrati di LSCs.
Durante i tre anni di progetto di dottorato in Alto Apprendistato ho potuto sviluppare una procedura di sintesi che consiste in quattro step:
• crescita di nanocristalli di CuInS2 core;
• formazione del quaternario tramite aggiunta di zinco (ZnCuInS2); passaggio cruciale per aumentare il QY e controllare la lunghezza d’onda di emissione;
• crescita di una shell di solfuro di zinco (ZnCuINS2/ZnS) per passivare la superficie dei nanocristalli, aumentare il QY e la fotostabilità;
• trattamento post sintesi di scambio di leganti parziale per migliorare la solubilità nella matrice polimerica.
I nanocristalli così prodotti mostrano un QY del 60% ed un’ottima solubilità nella matrice polimerica. Infatti, è stato prodotto un LSC di grande dimensione (30 cm x 30 cm x 0.7 cm) la cui optical power efficiency, OPE = 6.8%.
Inizialmente ho sviluppato la procedura di sintesi in un pallone di vetro da 25 mL, producendo 250 mg a sintesi. Grazie all’attrezzatura fornita da Glass to Power S.p.A ho potuto studiare lo scale-up della sintesi. Dapprima ho effettuato studi preliminare, per approfondire alcune possibili problematiche dovute all’aumento dei volumi, su palloni di maggiori dimensioni, 500 mL e 2 L. Analizzate e risolte le tematiche di riscaldamento e stop della sintesi ho effettuato sintesi in un reattore preindustriale producendo 300 g di nanocristalli di ZnCuINS2/ZnS.
Oltre ad incrementare la produzione di sintesi da 250 mg a 300 g mi sono occupata dell’ottimizzazione della procedura di sintesi. Ho testato diverse strategie per incrementare il QY senza danneggiare la solubilità nel polimero. Grazie ad una variazione di reagente nel secondo step e ad un incremento dei layer della shell ho ottenuto nanocristalli con 80% di QY.
Il prossimo step sarà effettuare lo scale-up di questa nuova procedura e produrre LSC di grandi dimensioni.
Grazie alle collaborazioni con altri studenti di dottorato ho sintetizzato nanocristalli di calcogenuro drogati oro e opportunamente decorati con molecole coniugate per sistemi di up-conversion. Grazie all’introduzione dell’oro in questi sistemi si è ottenuta un’efficienza di up-conversion del 12%.Luminescent solar concentrators (LSCs) are waveguides composed of a polymeric matrix doped or coated with fluorophores. The direct and/or diffuse sunlight that penetrates the matrix is absorbed by the fluorophores and then re-emitted by them with less energy. The light emitted, thanks to the total internal reflection, propagates until it reaches the edges of the wave guide where it is converted into electricity by photovoltaic cells placed on the perimeter of the matrix. The efficiency of the device is reduced by numerous loss processes, due to the reflection of the matrix and the escape cone, and/or due to the characteristics of the fluorophores, such as the absorption coefficient, the quantum yield (QY) of photoluminescence (PL) and the reabsorption. To minimize losses due to fluorophores, a good alternative are colloidal quantum dots (QDs) that usually have a high QY, a high absorption coefficient and a controllable emission wavelength by changing the size of the nanocrystals. Furthermore, by properly engineering the QDs, it is possible to realize particles with high Stokes-shift between the absorption and emission spectra, in order to reduce the reabsorption as much as possible. The project is focused on the development of the synthesis of QDs, in order to optimize the QY of photoluminescence, compatibility with the polymer matrix and photostability, while limiting the reabsorption. Besides. the synthesis procedure must be easily transferable on industrial volumes, to meet the production needs of high square meters of LSCs. During the three years of the doctoral project in High Apprenticeship I was able to develop a synthesis procedure consisting of four steps: • growth of CuInS2 core nanocrystals; • quaternary formation with zinc addition (ZnCuInS2); crucial step to increase the QY and control the emission wavelength; • growth of a zinc sulphide shell (ZnCuInS2/ZnS) to passivate the surface of nanocrystals, increase QY and photostability; • post-synthesis treatment of the partial exchange of ligands to improve solubility in the polymer matrix. The nanocrystals thus produced show 60% QY and excellent solubility in the polymer matrix. In fact, a large size LSC (30 cm x 30 cm x 0.7 cm) was produced, whose optical power efficiency, OPE = 6.8%. Initially, I developed the synthesis procedure in a 25 ml glass flask, producing 250 mg for batch. Thanks to the equipment provided by Glass to Power s.p.A I was able to study the increase in the scale of the synthesis. Firstly, in order to investigate some possible problems due to the increase in volumes, I have carried out preliminary studies on larger balloons, 500 mL and 2 L. After analysis of heating and quenching of synthesis, I have performed the synthesis in a preindustrial reactor producing 300 g of nanocrystals of ZnCuInS2/ZnS. In addition I also optimized the synthesis procedure. I tested several strategies to increase QY without damaging solubility in the polymer. Thanks to a variation of the reagent in the second step and an increase of the shell layers, I obtained nanocrystals with 80% of QY. The next step will be to scale up this new procedure and produce large LSCs. I collaborated with other PhD students, in particular, I synthesized with a heat-up method CdSe nanocrystals doped with Au7 clusters and decorated with conjugated dyes as efficient triplet sensitizers or up-conversion applications (gold doping improves up-conversion efficiency). The beneficial effects of the doping strategy result in a maximum UC efficiency of 12%, which is an unprecedented result for up-conversion based on decorated NCs as triplet sensitizers.
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TRIPALDI, LAURA. « Self-Assembly of Nanoparticles in Rubber Nanocomposites ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2022. http://hdl.handle.net/10281/381184.
Texte intégralRésumé :
Le nanoparticelle (NP) di SiO2 sono note per migliorare le proprietà meccaniche e funzionali dei materiali nanocompositi (NC) e sono ampiamente utilizzate come filler di rinforzo negli pneumatici. Le proprietà dei NC dipendono dalla distribuzione delle NP di filler, che a sua volta dipende dalla morfologia e dalla chimica superficiale delle NP. La dispersione di SiO2 NPs idrofiliche in matrici polimeriche è tipicamente ottenuta tramite funzionalizzazione con silani a catena corta. Mentre le NP anisotropiche sono note per auto-organizzarsi in strutture ordinate, producendo migliori proprietà meccaniche nei NC elastomerici, è stato dimostrato che anche le NP sferiche di SiO2 ricoperte con catene di oligomeri, ovvero le SiO2 Hairy NP (SiO2 HNP), possono migliorare la compatibilizzazione filler/matrice mentre si auto-organizzano in superstrutture anisotropiche. Tuttavia, la sintesi di SiO2 HNP con gusci elastomerici è ancora largamente inesplorata, e la relazione tra l'auto-organizzazione delle HNP e le proprietà meccaniche dei NC deve ancora essere del tutto compresa. In questo contesto, lo scopo di questa tesi è stato quello di i) sviluppare una sintesi efficiente di SiO2 HNPs con dimensioni, morfologia e chimica di superficie controllate; ii) preparare NC elastomerici basati su SiO2 HNP con rinforzo migliorato e isteresi ridotta; iii) valutare gli effetti dell'auto-organizzazione sulle prestazioni meccaniche dei materiali e iv) studiare le interazioni tra SiO2 HNPs per determinare quali parametri controllano i processi di auto-organizzazione.
Durante il primo anno di attività di dottorato è stata ottimizzata la sintesi di SiO2 HNP funzionalizzate con polibutadiene (PB) con un approccio colloidale. La sintesi ha garantito un eccellente controllo della morfologia e della chimica di superficie delle HNPs. Le particelle non funzionalizzate e funzionalizzate sono state completamente caratterizzate con una pletora di metodi morfologici e fisico-chimici mostrando evidenza di auto-organizzazione. Durante il secondo anno, le SiO2 HNP sono state utilizzate per preparare NC elastomerici in una formulazione industriale. Le proprietà meccaniche dei NC vulcanizzati e non vulcanizzati sono state caratterizzate da analisi dinamico-meccaniche e prove di trazione, mostrando che le HNP migliorano fortemente il rinforzo riducendo la dissipazione di energia, evidenziando migliori interazioni filler/matrice rispetto alle NP SiO2 non funzionalizzate e funzionalizzate con silano. La caratterizzazione morfologica delle NC ha confermato il miglioramento della dispersione e della distribuzione del filler con l'aumento della funzionalizzazione con PB e ha mostrato l'auto-organizzazione delle HNP in sovrastrutture anisotropiche simili a stringhe.
Durante il terzo anno, il modello delle HNP è stato adattato a una formulazione riproducibile su scala industriale usando un silano macromolecolare a base di PB (MacroSil) e silice commerciale. Le proprietà meccaniche degli NC elastomerici sono state caratterizzate in modo approfondito con analisi meccaniche dinamiche, prove di trazione e analisi Large Amplitude Oscillatory Shear (LAOS), dimostrando che l'aggiunta di MacroSil migliora significativamente le prestazioni meccaniche degli NC rispetto a un silano a catena corta.
Infine, esperimenti di Small-Angle X-Ray Scattering (SAXS) sulle dispersioni di SiO2 HNPs in collaborazione con il Prof. Simone Mascotto dell'Università di Amburgo hanno fornito parametri strutturali fondamentali che sono stati utilizzati per formulare un modello teorico delle interazioni tra HNP, in collaborazione con il Prof. Arturo Moncho dell'Università di Granada e il Prof. Gerardo Odriozola della UAM-Azcapotzalco. Il modello teorico ha predetto la formazione delle sovrastrutture anisotropiche di SiO2 HNP osservate sia nelle particelle prive di matrice sia nei NC elastomerici.SiO2 nanoparticles (NPs) are known to improve the mechanical and functional properties of nanocomposite (NC) materials and are widely used as reinforcing fillers in tyres. The properties of NCs depend on the distribution of filler NPs, which in turn depends on the morphology and surface chemistry of filler NPs. The dispersion of hydrophilic SiO2 NPs in polymer matrices is typically achieved by functionalization with short-chain silanes. While anisotropic NPs are known to self-organize in ordered structures, producing improved mechanical properties in rubber NCs, evidence has shown that also spherical SiO2 NPs grafted with oligomer chains, i.e. SiO2 Hairy NPs (SiO2 HNPs), can improve filler/matrix compatibilization while self-organizing in anisotropic superstructures. However, the synthesis of SiO2 HNPs with rubbery shells is still largely unexplored, and the relationship between HNPs self-assembly and the mechanical properties of NCs is yet to be understood. In this context, the aim of this thesis was i) to develp an efficient synthesis of SiO2 HNPs with tunable size, controlled morphology and tailored surface chemistry; ii) to prepare rubber NCs based on SiO2 HNPs with improved reinforcement and reduced hysteresis; iii) to assess the self-assembly effects on the mechanical performance of the materials and iv) to study the interactions between SiO2 HNPs in order to determine which parameters control the self-assembly processes. During the first year of PhD activity the synthesis of polybutadiene (PB)-grafted SiO2 HNPs by a colloidal approach was optimized. The synthesis granted excellent control of HNPs morphology and surface chemistry. The bare and functionalized particles were fully characterized by a plethora of morphological and physico-chemical methods showing evidence of self-assembly. During the second year, SiO2 HNPs were used to prepare rubber NCs in an industrial formulation. The mechanical properties of the cured and uncured NCs were characterized by dynamic-mechanical analysis and tensile tests, showing that HNPs strongly improve reinforcement while reducing energy dissipation, highlighting improved filler/matrix interactions compared to both bare and silane-functionalized SiO2 NPs. Morphological characterization of the NCs confirmed the improvement of filler dispersion and distribution with increased PB functionalization and showed the self-organization of HNPs in anisotropic string-like superstructures. During the third year, the HNPs model was adapted to a scalable industrial rubber formulation using a PB macromolecular silane (MacroSil) and commercial precipitated silica. The mechanical properties of the rubber NCs were thoroughly characterized with dynamic mechanical analysis, tensile tests and Large Amplitude Oscillatory Shear (LAOS) analysis, showing that the addition of MacroSil significantly improves the mechanical performance of NCs compared to a short-chain silane. Finally, Small-Angle X-Ray Scattering of SiO2 HNPs dispersions in collaboration with Prof. Simone Mascotto at Hamburg University provided crucial structural parameters which were used to formulate a theoretical model of HNPs interactions, in collaboration with Prof. Arturo Moncho of the University of Granada and Prof. Gerardo Odriozola of UAM-Azcapotzalco. The theoretical model predicted the formation of the SiO2 HNPs anisotropic superstructures observed both in matrix free conditions and rubber NCs.
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PIRAS, ROBERTO. « Synthesis and Characterization of Bi2S3 Colloidal Nanoparticles for Photovoltaic Applications ». Doctoral thesis, Università degli Studi di Cagliari, 2016. http://hdl.handle.net/11584/266676.
Texte intégralRésumé :
Global energy consumption is expected to increase significantly together with the greenhouse gas emissions and the problem of fossil fuels exhaustion. Solar energy, as an alternative and renewable form of energy, has gained pop- ularity as possible solution for all these problems. Lots of materials have been studied to implement the energy conversion efficiency of the so-called third generation solar cells. These devices could be a cheaper alternatives to the silicon-based ones. Unfortunately, they are often characterized by short life- time or health hazardous materials. Bismuth sulfide(Bi2S3) is a promising n-type semiconductor for solar energy conversion.In this work,the properties of the compound will be discussed,as well as its potential for applications in solar energy technology.Wehave explored the colloidal synthesis of Bi2S3 nanocrystals,with the aim of employing them in the fabrication of solution- processable solar cells and to replace toxic heavy metals chalcogenides likePbS or CdS,that are currently employed in such devices. We compare different methods to obtain Bi2S3 colloidal quantum dots, including the useof environmentally benign reactants, through horganometallic synthesis. Surfactant-assisted colloidal synthesis(SACS) methods were used to synthesize Bi2S3 nanoparticles with different size and shape.These methods have been employed changing systematically several parameters such as temperature and timeofsynthesis, concentration ofchemical reagents and sulfur precursors. Morphological characteristics and optical properties of all the synthesized nanoparticles have been characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), UV-Vis and photoluminescence (PL) spectroscopy. After the characterization of electrical properties of bismuth sulfide sam- ples together with the preliminary attempts to find the most advantageous methods for the production of homogeneous film on conductive supports, asample was chosen like standard and it was employed in building of various prototype of third generation solution processed solar cells. Dip and spin coat- ing techniques were employed to produce homogeneous film of nanoparticleson conductive support, also in combination with organic polymer such P3HT, Pedot:PSS and Spiro-OMeTAD. The resulting solar cells were tested for power conversion efficiency (PCE). Synthesis and characterizations have been carried out in Dipartimento di Scienze Chimiche e Geologiche, Università degli Studi di Cagliari, under the supervision of Prof. Anna Musinu and Prof. Carla Cannas. Optoelectronic characterizations and solar cells manufacturing have been carried out in Di- partimento di Fisica, Università degli Studi di Cagliari, under the supervision of Prof. Michele Saba, Prof. Andrea Mura and Prof. Giovanni Bongiovanni.
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Khan, Saif A. « Microfluidic synthesis of colloidal nanomaterials ». Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/37223.
Texte intégralRésumé :
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2006.Includes bibliographical references.
This thesis focuses on microfluidics based approaches for synthesis and surface-engineering of colloidal particles. Bottom-up assembly through colloidal nucleation and growth is a popular route to the controlled synthesis of nanomaterials. Standard bench-scale synthetic chemistry techniques often involve non-uniform spatial and temporal distributions of concentration and temperature, and are not readily scalable. Photolithography-based microfabrication enables the application of classical techniques of chemical reaction engineering to design chemical reactors that cannot be realized easily at the macroscale, and that closely approach theoretical 'idealized' reactor configurations. In addition, the microfluidic format allows precisely controlled reaction conditions such as rapid mixing, and concentration and temperature uniformity. The goal of this thesis was to design microfluidic reactors for synthesis of core-shell colloidal particles with tunable sizes. Microscale segmented gas-liquid flows overcome the large axial dispersion effects associated with single-phase laminar flows. Microchannel devices that yielded uniform, stable gas-liquid segmented flows over three orders of magnitude in flow velocity were first developed.
(cont.) Extensive experimental studies of the transport, dynamics and stability of such flows were then conducted with pulsed-laser fluorescent microscopy, optical stereomicroscopy and micro particle image velocimetry (-PIV). Flow segmentation not only reduces axial dispersion, but also allows rapid micromixing of miscible liquids through internal recirculations in the liquid phase. This added functionality is especially useful in syntheses involving colloidal particles that, due to inherently low diffusivity, cannot be rapidly mixed by laminar diffusive techniques. Continuous segmented flow reactors were then developed for the synthesis of colloidal silica and titania particles by sol-gel chemistry. Particle sizes could be tuned by varying the rates of flow of reactants, or by varying the chip temperature. Particle size distributions comparable to or narrower than the corresponding stirred-flask synthesis, with little agglomeration or shape distortion were obtained. Coating of colloidal particles with one or more layers of different materials is used to modify their optical, chemical or surface properties. Core-shell particles are often prepared by controlled precipitation of inorganic precursors onto core particles.
(cont.) Synthesis of such structures requires precise control over process parameters to prevent precipitation of secondary particles of shell material and agglomeration of primary particles. Particles coated with titania are exceptionally difficult to synthesize due to the high reactivity of the titania precursors, which makes controlled precipitation difficult. A novel continuous flow microfluidic reactor with sequential multi-point precursor addition was developed for colloidal overcoating processes. Silica particles were coated with uniform titania layers of tunable thickness by the controlled hydrolysis of titanium ethoxide, with no secondary particle formation or agglomeration. An integrated reactor for continuous silica synthesis and in-situ series overcoating with titania was then developed using a two-level stacked reactor fabrication process. Finally, multi-step nanomaterials synthesis and surface coating with incompatible chemistries requires the development of microfluidic 'unit operations' equivalent to particle filtration. In this context, rapid, continuous microfluidic particle separation was demonstrated using transverse free-flow electrophoresis.
by Saif A. Khan.
Ph.D.
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Corradi, Roberto. « Conducting polymer-silica colloidal composites ». Thesis, University of Sussex, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263866.
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Nur, Hani. « Colloidal microgels : synthesis, characterisation and applications ». Thesis, University of Greenwich, 2009. http://gala.gre.ac.uk/8163/.
Texte intégralRésumé :
Four sets of NIPAM and non-NIPAM based colloidal microgels have been synthesized by a surfactant-free emulsion polymerisation (SFEP) technique, which are: (i) poly (NIPAM) based homo-polymer, (ii) poly (NIPAM) based co-polymer, (iii) hydrophobically modified homo-polymer and (iv) hydrophobically modified co-polymer microgels. Poly (NIPAM) based homo-polymer microgels have been studied with respect to their heteroaggregation/heteroflocculation behaviour with oppositely charged polystyrene latex (PS) particles. It has been shown that the particle size, concentration and temperature play an important role in the ionic interaction between oppositely charged microgel and PS latex particles. Some particulate dispersions have shown temperature-dependent reversible flocculation behaviour, which could be applicable in the water industry for the removal of colloidal impurity from water. A strong irreversible aggregation was also observed for some microgel-latex mixtures, which may find useful application in the field of crude oil recovery. Hydrophobically modified homo-polymer and co-polymer microgels have been prepared from a range of novel monomers. The monomers have been chosen with varying hydrophobic chain length in order to manipulate the swelling properties of the resultant particles in different solvents. The dispersibility behaviour of the novel and NIPAM-based microgels has also been studied in different solvents to find their utility in removing water from oil. Colloidal microgel particles have shown successful application in reducing the water content of biodiesel to an acceptable level. Karl Fischer titration results have shown that water level in biodiesel can be reduced below 500 ppm from 1800 ppm by using microgel as water absorbent. According to the EN14214 specification by European Committee 500 ppm is the maximum water level allowed in biodiesel to be useful in combustion engine.
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IMRAN, MUHAMMAD. « Synthesis and Post-synthesis Transformations of Colloidal Semiconductor Nanocrystals ». Doctoral thesis, Università degli studi di Genova, 2018. http://hdl.handle.net/11567/945513.
Texte intégralRésumé :
The present PhD thesis focuses on two main classes of semiconductor colloidal nanocrystals, i.e. lead halide perovskite and copper chalcogenides. The former class of semiconductor NCs are promising materials for many high performance optoelectronics applications, as they exhibit a tunable band gap in the range of 1.4 to 2.9 eV and an efficient photoluminescence characterized by narrow emission linewidths and have been explored the most in the last years. Following the standard hot injection based synthesis and selecting a combination of short chain acid (octanoic acid or hexanoic acid) together with alkyl amines (octylamine and oleylamine) we prepared strongly fluorescent CsPbBr3 perovskite nanowires with tuneable width, in the range from 20 nm (exhibiting no quantum confinement, hence emitting in the green) to 3 nm (in the strong quantum-confinement regime, emitting in the blue) for the first time. However the main limitation of the colloidal synthesis protocols that was followed in aforementioned case including the ligand assisted reprecipitation routes which is the second most frequently used method for preparation of LHPs, is that they employ PbX2 (X= Cl, Br, or I) salts as both lead and halide precursors which consequently limit the precise tunability of the amount of reaction species such as metals or halides precursors and are not applicable to entire family of APbX3 (A=FA, MA and Cs; X=Cl, Br, I). To overcome this issue we developed benzoyl halide based colloidal synthesis route i.e broadly applicable to the entire family of LHP NCs and not only ensures the independent tunability of reaction precursors but also maintain the overall integrity of the NCs such as phase purity and high PLQY. Despite the significant advances in synthesis procedures, the control over size monodispersity, shape and phase purity remains another long standing challenge. This is in fact due to the tendency of primary alkyl amine in the form of alkylammonium ions that could compete with Cs+ ions and leads to the anisotropic growth such as NPLs or their use in excess permotes the Pb-depleted Cs4PbX6 phases. We develop here a strategy to achieve size, shape and phase pure CsPbBr3 nanocubes by substituting primary alkyl amines with secondary alkyl amines. We attributed this excellent control over the shape and phase purity to the inability of secondary amines to find the right steric conditions at the surface of the nanocrystals which consequently limits the formation of low dimensional structures. The shape purity and narrow size distribution leads to their ease of self-assembly in superlattices reaching up to 50 microns in lateral dimensions, which are the largest dimensions reported to date for superlattices of LHP NCs. The second class of materials studied here, i.e. copper chalcogenides, are mainly attractive due to their tunable composition via post synthesis chemical transformations, plasmonic properties, low toxicity and environmental friendliness. Taking the advantage of colloidal synthesis and using Cu2S as a template we develop a strategy to obtain novel AuCuS-Cu2S heterostructure through cation exchange, which cannot be realized through conventional synthesis approaches. We further investigated the stability of Cu2S NCs with different dimensionalities and their thermal evolution subsequent to the metal decoration. Interestingly the presence of additional metallic NCs, such as Au and Pt not only improves their thermal stability but also leads to the formation of bi-metallic alloys semiconductor heterostructure.
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Many, Véronique. « Synthèse et design de nanorésonateurs optiques actifs dans le visible ». Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0325.
Texte intégralRésumé :
L’étude et la réalisation de métamatériaux auto-assemblés possédant une réponse magnétique aux fréquences optiques font l’objet d’un champ de recherche très actif depuis plusieurs années. De nombreux calculs théoriques ont prédit qu’un arrangement dense de briques élémentaires plasmoniques, « les méta-atomes », conduirait à des matériaux à indice négatif actifs dans le domaine du visible. Il a été démontré qu’un nano-objet ayant un coeur de silice décoré de 12 nanoparticules d’or sphériques permettrait d’optimiser le phénomène de magnétisme optique. Ma thèse repose sur l’élaboration de ces objets à partir de particules colloïdales, parfaitement symétriques, constituées d’un coeur de silice et 12 nodules de polystyrène. Ces nodules de PS pouvant être éliminés ultérieurement par dissolution. Ces objets ont permis de fabriquer des particules de silices décorées d’un nombre précis de « patchs » ou de « fossettes ». Ces objets ont été formés en grande quantité. Nous sommes parvenus à rendre les cavités de surface des particules à fossettes collantes pour des germes d’or de 2-3 nm de diamètre et initier leur croissance. Les mesures de propriétés optiques de ces dodécapodes dorés ont reflété le couplage intense existant entre les nanoparticules plasmoniques autour du coeur diélectrique. La possibilité de faire croitre de l’argent à la surface des germes d’or permet de générer des nanorésonateurs avec des modes magnétiques optiques encore plus intenses que ceux observés pour les systèmes à base d’orOver the last decade, the field of self-assembled metamaterials exhibiting unusual properties such as a magnetic response in the visible range represents a challenging and attracting area. Many simulations reported that a dense arrangement of specific plasmonic sub-units called “meta-atoms”, may lead to a material with a negative refractive index. It was reported by computational modelling that a dodecapod clusters made of a central dielectric core and surrounded by a controlled number of satellites (12 satellites, here) with a specific size can exhibited some interesting properties. Here, the purpose was to fabricate such clusters from colloidal particles, which are perfectly symmetrical, made of a silica core and 12 polystyrene nodules. Subsequently, those polystyrene nodules can be dissolved to get silica particles with a specific number of “patches” or “dimples”. Those objects were synthesized in a large quantity. We were able to make those dimples sticky to tiny gold seed of 2-3 nm size and to grow then for a specific size. Optical measurements reported the strong magnetic coupling in-between the plasmonic nanoparticles around the dielectric core. We also reported that growing silver on tiny gold seeds generates stronger magnetic responses than those observed from gold clusters
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Briggs, Nigel P. « The synthesis and colloidal behaviour of copolymers ». Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328309.
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Young, Robert A. « Synthesis and application of novel colloidal material ». Thesis, University of Warwick, 2016. http://wrap.warwick.ac.uk/108359/.
Texte intégralRésumé :
Within this thesis we explore the synthesis of novel colloidal particles for the use as both a thermochromic indicator and opacifiers. Initially in Chapter 1 we describe the synthesis of polystyrene copolymers and the effect the co-monomers have upon the phase transitional temperature within dioctyl phthalate. Co-polymers containing varying mol% of copolymers led to a decrease in the transitional temperatures for the systems. Following the determination of the phase transitions, we touched upon the potential to encapsulate the oils and use them within both a soft fibre and a waterborne latex binder as a thermochromic pigment. In Chapter 2 we looked into the synthesis of hollow non-spherical silica particles and their potential use within both ultrasound imaging and films as an opacifying agent. In Chapter 3 we expand upon the use of the silica shells by dispersing them within a PMMA nanocomposite to determine the effect on the mechanical properties. In Chapter 4 we explored further into the UCST systems shown in Chapter 1 with the addition of specialised dye tagging of the polystyrene chains to obtain a fluorescent changes upon phase transition.
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Доброжан, Олександр Анатолійович, Александр Анатольевич Доброжан, Oleksandr Anatoliiovych Dobrozhan, Анатолій Сергійович Опанасюк, Анатолий Сергеевич Опанасюк, Anatolii Serhiiovych Opanasiuk, Світлана Іванівна Кшнякіна, Светлана Ивановна Кшнякина et Svitlana Ivanivna Kshniakina. « Synthesis of Cu2ZnSnSe4 nanoparticles by colloidal method ». Thesis, Видавництво Львівського національного університуту імені Івана Франка, 2014. http://essuir.sumdu.edu.ua/handle/123456789/38345.
Texte intégralRésumé :
Recently the thin films of semiconductor compound Cu2ZnSnSe4 (CZTSe) have attracted the attention of scientific community as alternative layers of CuInSe2 (CIS), CuIn1-xGaxSe2 (CIGS) and CdTe for designing cheap thin film solar cells (SCs). This material has the optimum for conversation solar energy into electricity band gap (Еg = 1 eV), high absorption coefficient (α > 105 cm-1), p-type conductivity and it’s characterized long lifetime as well as high mobility of charge carriers. The colloidal synthesis is promising among nonvacuum chemical methods for obtaining CZTSe nanoparticles which allows synthesizing nanoparticles of a wide range of materials with the possibility of forming films using spin-coating, spray pyrolysis techniques. Also, it is important that the properties of the synthesized nanoparticles strongly depend on the shape and size. The above mentioned purpose main aim of this work which is to study the morphological characteristics and chemical composition of nanoparticles CZTSe with different sizes and shapes of the synthesized by colloidal method.
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Phan, The Anh. « Synthèse de polyaniline en systèmes micellaires : application à la protection des métaux ». Thesis, Toulon, 2014. http://www.theses.fr/2014TOUL0021/document.
Texte intégralRésumé :
Dans cette étude nous avons étudié la polymérisation de l’aniline en milieu aqueux micellaire eau-acide décylphosphonique (DcPA) ainsi qu’en milieu micellaire inverse acide décylphosphonique/eau/n-heptane : chloroforme (2 :1 v/v). Contrairement au système aqueux micellaire, la vitesse de polymérisation dans le système micellaire inverse augmente lorsque la concentration en DcPA dans le milieu réactionnel diminue. Ce résultat a été attribué à des différences de compacité de la couronne hydrophobe des micelles inverse, qui impactent la diffusion de l’aniline au cœur des gouttelettes d’eau, le lieu préférentiel de la polymérisation.La conductivité électrique maximale obtenue est de 3.6 S.cm-1. Cette valeur de conductivité est plus élevée de 4 ordres de grandeur comparée à la conductivité électrique de PANI dopée DcPA préparée par post-traitement de la PANI EB avec une solution de DcPA (2.3x10-4 S cm-1). Les analyses de diffraction des rayons X (DRX) ont révélé une structure lamellaire de la polyaniline préparée en milieu micellaire eau-DcPA dans laquelle les chaînes de polyaniline sont séparées par les longues chaînes alkyle du DcPA. Cette organisation diminue les interactions interchaînes de la polyaniline et contribue à l’augmentation de la solubilité en milieu organique de la polyaniline.La polyaniline dopée DcPA a été incorporée comme pigment dans un liant polymère polyvinyl butyral (PVB), puis appliqué sur un acier à faible teneur en carbone. Dans le cas de la polyaniline préparée dans le milieu aqueux micellaire de DcPA, la dispersion de polyanilinea été également appliquée après dialyse sur acier en couche mince, puis revêtue d’une couche de finition PVB. Les films PVB-PANI ont été exposés à des environnements neutres chlorurés (brouillard salin et milieu NaCl 3.5%). A partir de mesures de spectrométrie d’impédance électrochimique, nous avons montré que l’efficacité de la protection anticorrosion de la polyaniline dopée DcPA augmentait avec le taux de dopant DcPA du polymère. Ces résultats suggèrent un rôle actif du DcPA dans le mécanisme de protection. Ce rôle actif du DcPA a été confirmé par analyse de la surface métallique après exposition qui a révélé la présence de sels de phosphonates de fer insoluble. La protection anticorrosion apportée par polyaniline dopée DcPA apparaît supérieure à la polyaniline non dopée ainsi qu’à la polyaniline dopée HClIn this thesis, the polymerization of aniline in micellar solutions of decylphosphonic acid (DPA) as well as reversed micellar solutions of decylphosphonic acid / water / n-heptane : chroloform (2 : 1 vol/vol) was investigated. Unlike micellar solution, the polymerizations rate in the reversed micellar solution increases as the DPA concentration in the reaction medium decreases. This result was attributed to the packing density of DPA molecules in the surfactant shell of inverse micelles, which affects the diffusion of aniline into the inner of the water droplets in which the polymerization is preferred. The maximum electrical conductivity obtained is 3.6 S.cm-1. This value is four orders in magnitude greater than the value of DPA doped PANI prepared by postsynthesis treatment of the PANI-base with the solution of DPA (2.3 x 10-4 S.cm-1). The results of the X-ray diffraction analysis suggested the formation of layered structure of PANI backbone separated by long alkyl side chains of DPA. This organization reduces interchain interactions of the polyaniline and contributes to the increase in solubility of PANI in an organic solvent.The DPA doped PANI was incorporated as a pigment in the polymer binder polyvinyl butyral (PVB), and then applied to a steel material with a low content of carbon. In the case of the polyaniline prepared in the micellar solution of DPA, the dispersion of PANI was also applied to steel with thin layer after dialysis, and then coated with a top coat PVB. The PVB-PANI coatings applied on steel substrates are exposed in neutral saline corrosive media such as salt-spray or 3.5% NaCl solution. Based on the electrochemical impedance spectroscopy measurements, it is found that the corrosion protection efficiency of the DPA doped PANI increases with the amount of dopant of DPA. These results show an active role of DPA in the mechanism of protection. The active role of DPA was also confirmed by the analysis of the exposed metallic surface with the presence of insoluble phosphonate of iron. The corrosion protection provided by the DPA doped PANI appears better than the undoped polyaniline and the one doped with HCl
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Meldrum, Fiona C. « Nanoscale synthesis in organised organic assemblies ». Thesis, University of Bath, 1992. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305061.
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Torres, Mendieta Rafael Omar. « Synthesis of colloidal nanomaterials through femtosecond laser ablation ». Doctoral thesis, Universitat Jaume I, 2016. http://hdl.handle.net/10803/387325.
Texte intégralRésumé :
La investigación de esta tesis se centra en la producción de nanoestructuras metálicas dentro de aceites orgánicos y nano-ensambles por ablación láser en líquidos para resolver los mayores problemas en su producción por métodos convencionales: poca estabilidad, producción de residuos químicos y reacciones químicas sin control debido a problemas de pureza. En particular, las mayores contribuciones son, la síntesis de nanofluidos basados en nanopartículas de oro que pueden ser utilizados como absorbentes volumétricos de luz e intercambiadores de calor. La fabricación de un nanofluido con una mejora de conductividad térmica de 4,06% sobre un fluido de transferencia de calor comercial, una mezcla eutéctica de óxido de bifenilo y difenilo, y la mejor estabilidad coloidal reportada en la literatura usando estos materiales. Y, por último, la demostración de la reducción parcial de láminas de óxido de grafeno y su decoración con nanopartículas de oro con ligandos libres, en un solo paso.The research conducted during this thesis work is focused on producing metal nanostructures inside organic oils and nano-essambles by Pulsed Laser Ablation in Liquids (PLAL) to solve the biggest issues on their production by conventional approaches: Poor stability, production of chemical waste and uncontrolled chemical reactions due to purity problems. In particular, the biggest contributions achieved on the present work, lies on the experimental demonstration of the synthesis of gold nanoparticles-based aqueous nanofluids that can be used as both volumetric light absorbers and heat exchangers. The fabrication of a nanofluid with a thermal conductivity enhancement of 4.06% over a commercial heat transfer fluid, an eutectic mixture of biphenyl and diphenyl oxide, and the best colloidal stability reported in the literature using these materials. And finally, demonstration of partial reduction of graphene-oxide sheets and its decoration with ligand-free gold nanoparticles, in a single reaction stage avoiding the production of chemical waste.
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Khan-Lodi, A. N. « Microparticle synthesis and colloidal catalysis in microemulsion media ». Thesis, University of Kent, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234057.
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Clinton, Jamie C. « Colloidal Cerium Oxide Nanoparticle : Synthesis and Characterization Techniques ». Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/31065.
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Fluorescence spectra and UV-Vis absorption spectra are collected on cerium oxide nanocrystalline particles. While CeO2 is the stable form of bulk cerium oxide, ceria nanoparticles exhibit a nonstoichiometric composition, CeO2-γ, due to the presence of oxygen vacancies and the formation of Ce2O3 at the grain boundaries. The Ce(III) ions, which are more reactive and therefore more desirable for various applications, are created by oxygen vacancies, which act as defects in the CeO2-γ crystal lattice. These defects form trap states in the band gap of CeO2, which can be seen in the absorption spectra. Ce(III) is required for fluorescence of the ceria nanoparticles while Ce(IV) is involved in only nonradiative transitions. The optical spectroscopy results show that the ceria samples have different ratios of Ce(III) ions to Ce(IV) ions, which is verified by x-ray photoemission spectroscopy (XPS).Master of Science
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Premathilaka, Shashini M. « Synthesis and Optical Properties of Colloidal PbS Nanosheets ». Bowling Green State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1561463157379607.
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Fielding, Lee A. « Synthesis, characterisation and applications of colloidal nanocomposite particles ». Thesis, University of Sheffield, 2012. http://etheses.whiterose.ac.uk/2859/.
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Lee, Hyeokjin. « Synthesis and characterization of colloidal II-VI semiconductor nanorods ». [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0012984.
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Söderlind, Fredrik. « Colloidal synthesis of metal oxide nanocrystals and thin films ». Doctoral thesis, Linköpings universitet, Institutionen för fysik, kemi och biologi, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-11831.
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A main driving force behind the recent years’ immense interest in nanoscience and nanotechnology is the possibility of achieving new material properties and functionalities within, e.g., material physics, biomedicine, sensor technology, chemical catalysis, energy storing systems, and so on. New (theoretical) possibilities represent, in turn, a challenging task for chemists and physicists. An important feature of the present nanoscience surge is its strongly interdisciplinary character, which is reflected in the present work. In this thesis, nanocrystals and thin films of magnetic and ferroelectric metal oxides, e.g. RE2O3 (RE = Y, Gd, Dy), GdFeO3, Gd3Fe5O12, Na0.5K0.5NbO3, have been prepared by colloidal and sol-gel methods. The sizes of the nanocrystals were in the range 3-15 nm and different carboxylic acids, e.g. oleic or citric acid, were chemisorbed onto the surface of the nanoparticles. From FT-IR measurements it is concluded that the bonding to the surface takes place via the carboxylate group in a bidentate or bridging fashion, with some preference for the latter coordination mode. The magnetic properties of nanocrystalline Gd2O3 and GdFeO3 were measured, both with respect to magnetic resonance relaxivity and magnetic susceptibility. Both types of materials exhibit promising relaxivity properties, and may have the potential for use as positive contrast enhancing agents in magnetic resonance imaging (MRI). The nanocrystalline samples were also characterised by transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS), and quantum chemical calculations. Thin films of Na0.5K0.5NbO3, GdFeO3 and Gd3Fe5O12 were prepared by sol-gel methods and characterized by x-ray powder diffraction (XRPD) and scanning electron microscopy (SEM). Under appropriate synthesis conditions, rather pure phase materials could be obtained with grain sizes ranging from 50 to 300 nm. Magnetic measurements in the temperature range 2-350 K indicated that the magnetization of the perovskite phase GdFeO3 can be described as the sum of two contributing terms. One term (mainly) due to the spontaneous magnetic ordering of the iron containing sublattice, and the other a susceptibility term, attributable to the paramagnetic gadolinium sublattice. The two terms yield the relationship M(T)=M0(T)+χ(T)*H for the magnetization. The garnet phase Gd3Fe5O12 is ferrimagnetic and showed a compensation temperature Tcomp ≈ 295 K.
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Coropceanu, Igor. « Colloidal CdSe/CdS nanostructures : synthesis, optical characterization and applications ». Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/107563.
Texte intégralRésumé :
Thesis: Ph. D. in Physical Chemistry, Massachusetts Institute of Technology, Department of Chemistry, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references.
The focus of this thesis is the study of CdSe/CdS nanostructures, from their fundamental properties to their integration in practical devices. This material system has proven to be remarkably robust both as a platform for studying physics in confined semiconductors, as well as for enabling various optical and optoelectronic applications. In this thesis, we will discuss our recent efforts to improve the synthesis of CdSe/CdS structures, to better understand their optical properties and to use them to create highly performing luminescent solar concentrators. In the first part of the thesis we will discuss our efforts to improve the synthesis of CdSe/CdS nanostructures of different dimensionalities. In particular, we discuss the synthesis of CdSe/CdS quantum dots and seeded CdSe/CdS nanorods that have a near unity photoluminescence quantum yield and complete energy transfer from the shell to the core. Next, we discuss the fabrication of luminescent solar concentrators using these materials and the optical characterization of these devices. Finally, in the last section, we use a combination of synthesis, spectroscopy, and modeling to gain better insight into the photoluminescence lineshape of CdSe/CdS quantum dots.
by Igor Coropceanu.
Ph. D. in Physical Chemistry
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Zhang, Guangya. « Synthesis and characterization of metal substituted colloidal silicate-1 ». Licentiate thesis, Luleå tekniska universitet, 1996. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-25696.
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Bhandari, Ghadendra B. « Synthesis and AB-Initio Simulations of Colloidal PBS Nanosheets ». Bowling Green State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1403519605.
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Sayevich, Uladzimir. « Synthesis, Surface Design and Assembling of Colloidal Semiconductor Nanocrystals ». Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-209074.
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The work presented in the thesis is focused on the synthesis of diverse colloidal semiconductor NCs in organic media, their surface design with tiny inorganic and hybrid capping species in solution phase, and subsequent assembling of these NC building units into two-dimensional close-packed thin-films and three-dimensional non-ordered porous superstructures.
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Hull, Peter J. « Synthesis and characterisation of quantum dots ». Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318760.
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Ward, Andrew David. « A study of the single-shot dispersion polymerisation of ethyl methacrylate in non-aqueous media ». Thesis, University of Bristol, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240730.
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McGrath, Jonathan G. « Synthesis and Characterization of Core/Shell Hydrogel Nanoparticles and Their Application to Colloidal Crystal Optical Materials ». Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14537.
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This dissertation describes the use of spherical micro- and nanoparticles as building blocks for the fabrication of colloidal crystals. The polymer component used in all of the projects that are described herein is poly-N-isopropylacrylamide (pNIPAm). The polymeric identity of particles composed of this soft, hydrogel material, which is also thermoresponsive, contributes to particle self-assembly to form ordered structures. Specifically, particles that possess a core/shell topology were investigated to allow for the localization of distinct polymeric properties. Chapter 2 examines a characterization technique using fluorescence resonance energy transfer (FRET) that was explored to investigate the structure of pNIPAm particles that possess this core/shell topology. Chapters 4-6 investigate strategies to impart both stability and flexibility to the particles so that these properties could assist in particle self-assembly as well as provide a stable construct for the production of robust crystalline materials. Styrene was used as the main monomer component in a copolymer synthesis with NIPAm to achieve poly(styrene-co-N-isopropylacrylamide particles (pS-co-NIPAm) that exhibited both hard and soft properties. Simple drying procedures were used to form crystal assemblies with these particles and the application of these pS-co-NIPAm particle suspensions as processable, photonic inks is also investigated. Chapter 7 examines the ability to physically cross-link colloidal crystals composed of pS-co-NIPAm particles by simple heating methods to produce robust films. The optical properties of these crystal films could be tuned by simple rehydration of the film due to the hydrogel character of the crystal building blocks. Chapters 3 and 5 examine the synthesis and self-assembly strategies of core/shell particles using the properties of pNIPAm shell layers that have been added to different types of core particles (silver or pS-co-NIPAm) for the purposes of fabricating colloidal crystals with enhanced properties using thermal annealing procedures. Chapter 8 explores the use of silver particles as tracers for the characterization of colloidal crystals composed of thermally annealed colloidal crystals composed of pNIPAm hydrogel particles.
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Pedetti, Silvia. « Synthesis and optical properties of II-VI colloidal two-dimensional nanocrystals : homo- and hetero-structures ». Electronic Thesis or Diss., Paris 6, 2015. http://www.theses.fr/2015PA066755.
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Ces travaux de thèse ont porté sur une nouvelle classe de semi-conducteurs colloïdaux sous forme de nanoplaquettes composées de chalcogénures de cadmium. Ces nanocristaux, comparables à des puits quantiques, présentent un confinement excitonique dans une seule direction, l’épaisseur, qui est contrôlée au niveau atomique. Les nanoplaquettes sont caractérisées par une excellente résolution spectrale et de bons rendements quantiques. Par conséquence, elles représentent de potentiels candidats pour développer des dispositifs optoélectroniques comme des diodes électroluminescentes ou bien des photo-détecteurs. Toutefois, dans ce but, il est nécessaire d’élargir la gamme de longueurs d’ondes d’absorption et d’émission et d’augmenter leur rendement quantique. Pour cela, nous avons étudié la synthèse colloïdale de nanoplaquettes à base d’homo- et d’hétèro-nanoplaquetts des groupes II-VI. Les nanocristaux fabriqués ont été caractérisé par spectroscopie UV-visible et de fluorescence, par diffraction à rayons X et par microscopie électronique. Dans un premier temps, nous avons optimisé la préparation de nanoplaquettes de CdTe en utilisant des procédés de synthèse colloïdale par injection de précurseurs à hautes températures. Ensuite, des structures plus complexes ont été investiguées. Par exemple, nous avons synthétisé nanoplaquettes cœur/couronne de CdSe/CdTe qui possèdent une structure électronique de type-II. Nous avons également étudié la croissance de couches d’un deuxième semi-conducteur dans la direction de l’épaisseur de plaquettes cœur pour la fabrication de structures type cœur/coque. Grâce au contrôle de la composition chimique du cœur et de la coque, l’alignement de bande a été modulé pour obtenir structures électroniques de type-I, quasi type-II et type-IIThis thesis project is based on the development of a novel class of colloidal two-dimensional nanocrystals, i.e. nanoplatelets (NPLs), composed of cadmium chalcogenides. These nanocrystals, in analogy to quantum wells, are characterized by an exciton confinement along one direction, i.e. the thickness, which can be controlled at atomic level. Nanoplatelets possess unique optical features as an excellent spectral resolution and good quantum yields. As consequence these nanocrystals are potential candidates for the fabrication of optoelectronic devices such as electroluminescent diodes or photo-detectors. However, for this aim it is necessary to enlarge the range of the absorption and emission wavelengths and to increase their quantum yield. For this reason, we investigated the colloidal synthesis of II-VI homo- and hetero-nanoplatelets which have been characterized by UV-Vis and photoluminescence spectroscopy, by X-ray diffraction and by electronic microscopy. First, we optimized the synthesis of CdTe NPLs using colloidal synthesis based on precursors injection at high temperatures. Then, we focused on more complexes hetero-structures. For example, through lateral extension reactions we obtained CdSe/CdTe core/crown NPLs which possess a type-II electronic structure. Successively, we studied the synthesis of core/shell NPLs by the growth of a second semiconductor layer along the thickness of NPLs cores. Depending on the core and shell chemical composition we could engineer the band gap of the nanoplatelets between type-I, quasi type-II and type-II electronic structures
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GIUSTRA, MARCO DAVIDE. « Synthesis of multi-branched polymers for the stabilization of metallic nanoparticles ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2022. http://hdl.handle.net/10281/366171.
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È fondamentale progettare e monitorare tutte le fasi preparative di un sistema di drug delivery in modo tale da raggiungere un determinato sito bersaglio. Ogni parte di un nanocarrier influenza sé stesso e l'ambiente circostante. Inoltre, per ottenere campioni monodispersi, il rivestimento e le eventuali funzionalizzazioni sono fondamentali per determinare la stabilità colloidale, prevedere il comportamento in un sistema biologico e raggiungere il target di interesse. In particolar modo, la razionalizzazione dei meccanismi di internalizzazione e la quantificazione dei carrier nei siti intracellulari è ancora oggi un tema di grande interesse in ambito nanomedico.
In questo lavoro, è stata presentata una classe di polimeri multidentati di facile sintesi mostrando un'ampia applicabilità in combinazione con nanoparticelle (NPs) metalliche. I polimeri multidentati sono stati coinvolti in tre diversi progetti. Il primo progetto mirava a presentare un polimero multidentato come modello generale da applicare nel rivestimento di superfici metalliche. Per dimostrarlo sono stati effettuati diversi test prendendo in considerazione la composizione e la dimensione delle NPs. Questo polimero è stato confrontato con altri due tipi di rivestimenti comuni in letteratura. I dati ottenuti mostrano come il nuovo rivestimento fornisca una maggiore stabilità colloidale. In secondo luogo, sono stati ottenuti miglioramenti dal punto di vista della tossicità e della bio-funzionalizzazione.
Nel secondo progetto, la catena polimerica è stata modificata con un altro ligando per ampliare il campo di applicazione di questi polimeri. La scelta della molecola è basata sull'affinità per alcune superfici metalliche. In questo caso la molecola scelta è il 4-amminotiofenolo, spesso utilizzata per applicazioni SERS. Inizialmente, il polimero è stato studiato rivestendo diversi tipi di NPs metalliche (oro e argento) e sono state eseguite analisi SERS. Le dimensioni e la forma hanno giocato un ruolo chiave, in particolare con le nanoparticelle cubiche concave risultando promettenti agenti diagnostici. Nella seconda parte del progetto, le nanoparticelle cubiche d'argento sono state utilizzate come modello per la valutazione del traffico cellulare e della maturazione endosomiale. Dei test preliminari sono stati effettuati a diversi pH (per emulare le variazioni di pH nelle fasi evolutive dell'endosoma) e studi in vitro sono stati eseguiti per verificare l'uptake delle NPs nelle cellule HeLa.
Il terzo progetto mirava a utilizzare il polimero sintetizzato come precursore nella sintesi di nanoparticelle anisotropiche. La forma ottenuta inizialmente è stata quella di un petalo, ma aumentando la temperatura, i petali si sono assemblati a nanofiori con un diametro al di sopra di 100 nm. La presenza del polimero SERS-attivo rende queste nanoparticelle ottimi candidati per questa tipologia di applicazione.Designing and monitoring all the preparation steps of a drug delivery system is essential to achieve a specific target. Each part of a nanocarrier affects the batch itself and the surrounding environment. In addition, to obtain monodispersed samples, the coating and any functionalization are crucial to determine the colloidal stability, to predict the behavior with a biological system, and the reaching of the target site. In particular, the achievement of intracellular sites by rationalizing the internalization mechanisms and quantifying the carriers in the target is still today a hot topic in the nanomedical field. Here, a class of multidentate polymers was presented: a simple way to synthesize them and show their broad applicability in combination with metal NPs. Multi-branched polymers were involved in three projects. The first project aimed to present a multidentate polymer as a general model to be applied in the coating of metal surfaces. To prove this, several tests were carried out by modulating the composition and size of the NPs. This easily synthesized polymer has been compared with two types of coatings common in literature. The obtained data show how the new surfactant provides high colloidal stable nanoparticles. Secondly, this leads to improvements from the point of view of toxicity and bio-functionalization. In the second project, the ligands polymer chain was modified to increase the range of application. Moreover, the choice of the ligand was based on the affinity for certain metal surfaces. In this case, the molecule is 4-aminotiophenol which is often used for SERS applications. Initially, the versatility of the polymer was investigated by coating different types of metallic NPs (gold and silver) and then SERS analyses were performed. Size and shape played a key role, especially with cubic concave nanoparticles that are promising for diagnostics application. In the second part of the project, cubic silver nanoparticles were used as a model for the evaluation of cell trafficking and endosomal maturation. Preliminary tests of NPs have been carried out at different pH (to emulate the pH variations in the endosomal evolution stages) and in vitro studies to check the nanoparticles uptake in HeLa cells were performed. The third project aimed to use the designed polymer as precursor in the synthesis of anisotropic nanoparticles. The shape obtained is a petal form. Subsequently, with the increase of the temperature, the petals assembled to nanoflowers above 100 nm. The presence of the active SERS polymer makes these nanoparticles, excellent candidates for this application.
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Pan, Guiquan. « Colloidal gallium nitride quantum dots (GaN QDs) : synthesis and characterization / ». View abstract, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3248456.
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Khlebtsov, B. N., et E. V. Panfilova. « Synthesis and Study of PNIPAM Nanogels Incorporated with Colloidal Silver ». Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35090.
Texte intégralRésumé :
Composite nanoparticles consisting of polymer gels with incorporated silver nanoparticles have been synthesized. The synthesis comprises two main stages. Initially, monodisperse hydrogel particles with a controlled diameter of approximately 500 nm are obtained by N-isopropylacrylamide polymerization. Then, silver ions are reduced on the surface of the polymer network. Variations in the concentration ratio between reductants and silver nitrate make it possible to produce silver nanoparticles with sizes in a range of 10-30 nm and different packing densities on the gel particle surface. The resultant nanocomposites have been studied by transmission electron microscopy, spectrophotometry, and dynamic light scattering. Depending on the size and packing density of the silver nanoparticles on the polymer particle surface, the plasmon resonance of the nanocomposites varies in a range of 420-750 nm, which determines variations in the color of the colloid from yellow, orange, and red to blue and blue-green. After the inclusion of silver nanoparticles, nanogels of poly(N-isopropylacrylamide) retain their capability for thermosensitive phase transition with a lower critical mixing temperature of 31 °C.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35090
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Weeraddana, Tharaka Missaka De Silva. « Synthesis, Characterization, and Exciton Physics of Colloidal Lead Sulfide Nanosheets ». Bowling Green State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1591381301083136.
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Kong, Eunsoo [Verfasser]. « Controlling Hypersonic Particle Resonances through Tailored Colloidal Synthesis / Eunsoo Kong ». Mainz : Universitätsbibliothek Mainz, 2020. http://d-nb.info/1211964981/34.
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Odziomek, Mateusz Janusz. « Colloidal Synthesis and Controlled 2D/3D Assemblies of Oxide Nanoparticles ». Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEN092/document.
Texte intégralRésumé :
La nanotechnologie est devenue un domaine clé de la technologie du XXIe siècle. L’important développement des approches pour la synthèse des nanoparticules (NPs) avec une composition, une taille et une forme désirées rend compte du potentiel de leur utilisation comme « blocs de construction » pour des structures de plus grande échelle. Cela permet d’envisager à la fois la fabrication de matériaux fonctionnels et de dispositifs directement à partir de colloïdes par approche ascendante et la conception de matériaux sur plusieurs échelles de grandeur. Le procédé utilise l'assemblage ou l'auto-assemblage de NPs et conduit à des matériaux avec des architectures différentes notamment 1D (bâtonnets), 2D (films) ou 3D (super-réseaux ou gels). Cependant, la plupart des assemblages 3D sont limités à l'échelle micrométrique et sont difficiles à contrôler. Pratiquement, la seule voie permettant la préparation de structures 3D macroscopiques à partir de NPs est la gélification et la préparation d'aérogels. Une voie alternative consiste à disperser les NPs dans une matrice, conduisant ainsi à un matériau composite massif, avec des NPs non agrégées distribuées de manière homogène.Le présent travail est consacré au développement de matériaux à partir de NPs d'oxydes métalliques (principalement Y3Al5O12: Ce et Li4Ti5O12) de différentes dimensions et pour diverses applications. La première partie de ce travail décrit la synthèse de NPs de YAG: Ce et de LTO par approche glycothermale. Dans le cas du YAG: Ce, les conditions de réaction ont été ajustées de façon appropriée pour obtenir des nanocristaux (NCs) non agrégés de quelques nanomètres. Des solutions colloïdales de différentes concentrations contenant de tels NCs ont été utilisées, pour la fabrication par la technique de « spin-coating », de films minces avec une épaisseur contrôlable. A l’inverse, la synthèse de LTO conduit à des NPs agrégées dans une structure hiérarchique très bénéfique pour les batteries au lithium. La grande surface spécifique et la porosité du matériau obtenu assurent en effet un échange efficace des ions lithium entre l'électrolyte et le matériau d'anode.Par ailleurs, les NCs de YAG: Ce ont été utilisés pour la préparation de matériaux monolithiques de grande taille avec une porosité et une transparence élevées. Pour cela, la solution colloïdale de NCs a été gélifiée par le changement brusque de la constante diélectrique du solvant de dispersion des NCs. Les gels ainsi obtenus ont été par la suite séchés de manière supercritique, donnant ainsi des aérogels à base de NPs de YAG:Ce, avec une porosité et une transparence élevées. La même approche s'est avérée appropriée pour d'autres systèmes à base de NPs de GdF3 ou de mélanges de NPS de YAG: Ce et de GdF3.Alternativement, les NPs de YAG: Ce ont été incorporées dans des aérogels de silice formant ainsi des aérogels macroscopiques robustes et hautement transparents présentant les propriétés des NPs incorporées. Ces aérogels composites ont été utilisés en tant que nouveaux types de capteurs pour les rayonnements ionisants de basse énergie dans les liquides ou les gaz. Leur porosité élevée permet un contact optimal entre l'émetteur radioactif et le scintillateur assurant ainsi une bonne récupération de l'énergie radioactiveNanotechnology has become a key domain of technology in XXI century. The great development of the synthetic approaches toward nanoparticles (NPs) with desired composition, size and shape expose the potential of their use as building blocks for larger scale structures. It allows fabrication of functional materials and devices directly from colloids by bottom-up approach, thus involving possibility of material design over several length scales. The process is referred to NPs assembly or self-assembly and leads to materials with varying architectures as for instance 1D (rods), 2D (films) or 3D (superlattices or gels). However most of 3D assemblies are limited to the micrometric scale and are difficult to control. Practically the only route allowing preparation of macroscopic 3D structures from NPs is their gelation and preparation of aerogels. As an alternative, NPs can be embedded in some matrix creating bulk composite material, with homogenously distributed non-aggregated NPs.Therefore, this work is devoted to development of materials with different dimensionalities for various applications from metal oxides NPs (mainly Y3Al5O12:Ce and Li4Ti5O12). The first part describes the syntheses of YAG:Ce and LTO NPs by glycothermal approach. In the case of YAG:Ce, the reactions conditions were appropriately adjusted in order to obtain non-aggregated nanocrystals (NCs) of few nanometers. The colloidal solution containing such NCs with different concentration was used for fabrication of thin films with controllable thickness by spin-coating method. Contrary, the synthesis of LTO led to aggregated NPs with hierarchical structuration which was highly beneficial for Li-ion batteries. The large surface area and porosity ensured efficient exchange of Li ions between electrolyte and anode material. Furthermore, the YAG:Ce NCs were used for preparation of macroscopic monoliths with high porosity and transparency. For that reason, colloidal solution of NCs was gelled by the abrupt change of solvent dielectric constant. The gels were further supercritically dried yielding YAG:Ce NPs-based aerogels with high porosity and transparency. The same approach turned o be appropriate for other systems like GdF3 or hybrid aerogels of YAG:Ce and GdF3.Alternatively, YAG:Ce NPs were incorporated into silica aerogels forming robust macroscopic and highly transparent aerogels exhibiting properties of incorporated NPs. They served for novel type of sensors for low-energy ionizing radiation in liquids and gases. Their high porosity assured well-developed contact between radioactive emitter and the scintillator ensuring good harvesting of radioactive energy
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SHAMSI, JAVAD. « Colloidal Synthesis of Lead Halide Perovskite Nanocrystals for Optoelectronic Application ». Doctoral thesis, Università degli studi di Genova, 2018. http://hdl.handle.net/11567/929994.
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Justynska, Justyna. « Towards a library of functional block copolymers synthesis and colloidal properties / ». Phd thesis, [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=977274519.
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Arnal, Pablo Maximiliano. « The synthesis of monodisperse colloidal core @shell spheres and hollow particles ». [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=981080596.
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Hunt, Zachary. « Surface functionalized colloidal particles and polymer synthesis for LED based applications ». Connect to this title online, 2008. http://etd.lib.clemson.edu/documents/1211389059/.
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Panthani, Matthew George. « Colloidal Nanocrystals with Near-infrared Optical Properties| Synthesis, Characterization, and Applications ». Thesis, The University of Texas at Austin, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3572875.
Texte intégralRésumé :
Colloidal nanocrystals with optical properties in the near-infrared (NIR) are of interest for many applications such as photovoltaic (PV) energy conversion, bioimaging, and therapeutics. For PVs and other electronic devices, challenges in using colloidal nanomaterials often deal with the surfaces. Because of the high surface-to-volume ratio of small nanocrystals, surfaces and interfaces play an enhanced role in the properties of nanocrystal films and devices.
Organic ligand-capped CuInSe2 (CIS) and Cu(InXGa 1-X)Se2 (CIGS) nanocrystals were synthesized and used as the absorber layer in prototype solar cells. By fabricating devices from spray-coated CuInSe nanocrystals under ambient conditions, solar-to-electric power conversion efficiencies as high as 3.1% were achieved. Many treatments of the nanocrystal films were explored. Although some treatments increased the conductivity of the nanocrystal films, the best devices were from untreated CIS films. By modifying the reaction chemistry, quantum-confined CuInSe XS2-X (CISS) nanocrystals were produced. The potential of the CISS nanocrystals for targeted bioimaging was demonstrated via oral delivery to mice and imaging of nanocrystal fluorescence.
The size-dependent photoluminescence of Si nanocrystals was measured. Si nanocrystals supported on graphene were characterized by conventional transmission electron microscopy and spherical aberration (Cs)-corrected scanning transmission electron microscopy (STEM). Enhanced imaging contrast and resolution was achieved by using Cs-corrected STEM with a graphene support. In addition, clear imaging of defects and the organic-inorganic interface was enabled by utilizing this technique.
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Fisher, Aidan Antony Edward. « Colloidal synthesis, structural characterisation and single molecule spectroscopy of semiconducting nanocrystals ». Thesis, University of Sussex, 2018. http://sro.sussex.ac.uk/id/eprint/73443/.
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Mohsen, Momee Reham M. « Synthesis, physico-chemical properties and potential applications of colloidal gel particles ». Thesis, University of Greenwich, 2015. http://gala.gre.ac.uk/18140/.
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Four new N-isopropylacrylamide (NIPAM) based particles have been synthesized and characterized. The first experimental chapter reports that fluorescent poly(Nisopropylacrylamide-co-5% vinyl cinnamate) microgels were deposited on different solid surfaces to produce new environmental responsive surfaces. The mass of microgel particles deposited on glass pre-treated with acid, glass pre-treated with base, quartz, stainless steel, gold and Teflon at 25°C and 60°C was determined using fluorescence spectroscopy. The factors affecting the adsorption/desorption of the microgel particles were also investigated. The study shows that the solid surface charge is the most significant factor, followed by that of surface roughness and temperature; meanwhile, the hydrophobicity/hydrophilicity of the surface was the least significant. Fluorescent temperature/pH responsive p(NIPAM-co-5% acrylic acid)-rhodamine B particles were studied. The results confirm the attachment of rhodamine B to the microgel particles. The long chains attached to the particles caused the particles to be poly-dispersed which suggests non-uniformity of particle size and behavior. Fluorescent temperature/pH responsive poly(N-isopropylacrylamide-co-5% lucifer yellow) (p(NIPAM-co-5% LY)) microgel particles were tested for toxicity. The particles were negatively charged, mono-dispersed and were approximately 250 nm in diameter at 15°C. The toxicity of different concentrations of p(NIPAM-co-5% LY), p(NIPAM) and NIPAM monomer was tested on two cell lines (HeLa and Vero). The results show that the two particles maintain cell viability over 80% (for both cell lines HeLa and Vero) up to a concentration of 3 mg/mL while NIPAM monomer showed a cell viability of over 80% at a concentration equal to or less than 0.3 mg/mL. The fourth experimental chapter explores the opportunity of using microgel particles as an emulsifier. p(NIPAM-co-5% acrylic acid)-hexenol particles with both hydrophilic and hydrophobic groups in their molecular structure were used to stabilize two emulsions (tricaprylin-in-water and hexadecane-in-water). The stability of the emulsions increased with increasing the concentration of the microgel. For the tricaprylin-in-water emulsion, a concentration of 0.3% w/v of the novel microgel particles managed to stabilize the emulsion for a week. In case of the hexadecane emulsion in water, 0.45% w/v microgel particles could show an increase in the emulsion stability and a decrease in the creaming.
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Ghifari, Najla. « Microfluidic-based colloidal ZnO microcapsules : synthesis, structure,organization and first applications ». Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPAST066.
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Ce travail se concentre sur le développement d’une approche microfluidique originale à base degouttelettes pour générer des sphères de ZnO de taille micrométrique très monodispersées avec une taille et une morphologie bien contrôlées. Cette approche est simple et prometteuse non seulement pour la fabrication de microcapsules de ZnO de taille uniforme, avec une taille ajustable et un contrôle précis à l’échelle micrométrique, mais aussi pour acquérir de nouvelles connaissances sur la compréhension des processus de croissance colloïdale et l’auto-organisation des nanoparticules de ZnO par la voie microfluidique. En outre, ces microparticules peuvent trouver des applications intéressantes dans de nombreux domaines tels que la photonique, le photovoltaïque ou la biomédecine. Ce travail porte sur l’effet des paramètres de fabrication sur la formation de gouttelettes, la taille et la stabilité des microsphères résultantes, ainsi que sur l’étude de leurs propriétés optiques et électriques, encouplant les travaux expérimentaux et théoriques. Nous avons montré la synthèse, dans une gamme micrométrique allant de 10 µm à 30 µm, de microcapsules de ZnO mésoporeuses à enveloppe fine et flexible. Nous étudions la caractéristique polaire des nanoparticules de ZnO et leur auto-organisation interfaciale. En outre, nous révélons que les charges électriques portées par lesunités primaires de ZnO jouent un rôle crucial dans la stabilité des gouttelettes en présence et en absence de molécules chargées. Elle joue également un rôle clé tout au long du processus d’assemblage, de la création des nanoparticules colloïdales de ZnO aux microgouttelettes, et enfin aux microsphères. Nous rapportons, pour la première fois, l’auto-organisation de microgouttelettes de ZnO liquide dopé en réseaux carrés. Nous démontrons qu’un tel résultat révèle l’aspect polaire des microgouttelettes de ZnO et corrobore un changement d’équilibre entre les forces motrices contrôlant l’organisation des nanoparticules de ZnO à l’échelle nanométrique. Nous avons développé différents modèles, en très bon accord avec le champdipolaire et les mécanismes de forces interfaciales, pour étayer les résultatsexpérimentaux mis en avant, et pour expliquer l’organisation interfaciale des nanoparticules de ZnO/RhB sur la base des propriétés d’organisation des gouttelettes de ZnO. À partir de nos résultats et de la dépendance constatée de la taille des microcapsules, de l’épaisseur de la coquille et de la densité de surface des nanoparticules par rapport à la taille des gouttelettes, nous fournissons un modèle original de la contribution des facteurs impliqués dans le mécanisme de formation de la coquilleThis work focuses on the development of an original droplet-based microfluidics approach to generate highly monodisperse micrometer-sized ZnO spheres with well-controlled size and morphology. This approach is straightforward, and promising not only for the fabrication of uniform-sized ZnO microcapsules, with adjustable size and precise control at the microscale, but also for gaining new insights into the understanding of colloidal growth processes and self-organization of ZnO nanoparticles by the microfluidic route. In addition, such microparticles may find interesting applications in many areas such as photonics, photovoltaics, or biomedecine. This work deals with the effect of handling parameters on droplet formation, size, and stability of the resulting microspheres, as well as the study of their optical and electrical properties coupling experimental and theoretical works. We have shown the synthesis, in a micrometric range from 10 mm to 30 mm, of mesoporous ZnO microcapsules with a thin and flexible shell. We investigate the polar feature of ZnO nanoparticles and their interfacial self-organization. Besides, we reveal that the electric charges carried by ZnO primary units play a crucial role in the stability of the droplets in the presence and in the absence of charged molecules. It also plays a key role throughout the assembly process from the creation of the colloidal ZnO nanoparticles to the microdroplets, and finally the microspheres. We report, for the first time, the selforganization of doped-ZnO liquid microdroplets in square arrays. We demonstrate that such a result discloses the polar aspect of ZnO microdroplets and corroborate a shift in the balance between the driving forces controlling the ZnO nanoparticles organization at the nanoscale. We have developed different models, in very good agreement with the dipole-field and interfacial forces mechanisms, to support the experimental results put forward, and to explain the ZnO/RhB nanoparticles interfacial organization based on ZnO droplets organization properties. Based on our findings, and on the stated dependence of the microcapsules size, shell thickness, and nanoparticles surface density versus the droplets size, we provide an original model for the contribution of the involved factors in the shell formation mechanism
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Li, Wenhui. « Connecting Thermodynamics and Kinetics of Ligand Controlled Colloidal Pd Nanoparticle Synthesis ». Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/100595.
Texte intégralRésumé :
Colloidal nanoparticles are widely used for industrial and scientific purposes in many fields, including catalysis, biosensing, drug delivery, and electrochemistry. It has been reported that most of the functional properties and performance of the nanoparticles are highly dependent on the particle size and morphology. Therefore, controlled synthesis of nanomaterials with desired size and structure is greatly beneficial to the application.
This dissertation presents a systematic study on the effect of ligands on the colloidal Pd nanoparticle synthesis mechanism, kinetics, and final particle size. Specifically, the research is focused on investigating how the ligand bindings to different metal species, i.e., metal precursor and nanoparticle surface, affect the nucleation and growth pathways and rates and connecting the binding thermodynamics to the kinetics quantitatively. The first part of the work (Chapters 4 and 5) is establishing isothermal titration calorimetry (ITC) methodology for obtaining the thermodynamic values (Gibbs free energy, equilibrium constant, enthalpy and entropy) of the ligand-metal precursor binding reactions, and the simultaneous metal precursor trimer dissociation. In brief, the binding products and reactions were characterized by nuclear magnetic resonance (NMR), and an ITC model was developed to fit the unique ITC heat curve and extract the thermodynamic properties of the reactions above. Furthermore, in Chapter 6, the thermodynamic properties, especially the entropy trend changing with the ligand chain length was investigated on different metal precursors based on the established ITC methodology, showing that the entropic penalty plays a significant role in the binding equilibrium.
The second part of the dissertation (Chapter 7 and 8) presents the kinetic and mechanistic study on size-tuning of the colloidal Pd nanoparticles only by changing different coordinating solvents as ligands together with the trioctylphosphine ligand. In-situ small angle X-ray scattering was applied to characterize the time evolutions of size, size distribution, and particle concentration using synthesis reactor connected to a capillary flow cell. From the real-time kinetic measurements, the nucleation and growth rates were calculated and correlated with the thermodynamics, i.e., Gibbs free energies of solvent-ligand-metal precursor reactivity and ligand-nanoparticle surface binding which were modified by the coordination of different solvents. Higher reactivity leads to faster nucleation and high nanoparticle concentration, and stronger solvent/ligand-particle coordination energy results in higher ligand capping density and slower growth. The interplay of both effects reduces the final particle size. Furthermore, because of the significance of the ligand-metal interactions, the synthesis temperature and ligand to metal precursor ratio were systematically to modify the relative binding between the ligand and precursor, and the ligand and nanoparticle, and determine the effect on the nucleation and growth rates. The results show that the relative rates of nucleation and growth is critical to the final size. A methodology for using the in-situ measurements to predict the final size by developing a kinetic model based is discussed.Doctor of Philosophy
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Ho, Minh Q. « Colloidal Synthesis and Optical Characterizations of Semiconductor Nanocrystals from Nontoxic Elements ». VCU Scholars Compass, 2015. http://scholarscompass.vcu.edu/etd/3915.
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To date, the search efforts have shifted from the toxic II-VI, III-V and IV-VI semiconductors to more environmentally friendly materials. Among Group II-V semiconductors, Zn3P2 has shown to be a more benign option, similar to Group IV (Ge, Si) materials, for future applications in photovoltaics and optoelectronics. This work is dedicated to the development of wet-chemical synthetic routes of (1) Zn3P2 and (2) Group IV (Ge, Si, Si1-xGex) nanocrystals with precise control over composition, crystal structure, size and dispersity by adjusting different reaction parameters such as temperature, time and solvent composition. Different characterizations will also be employed to probe the size- and composition-dependent physical and optical properties of resulting products.
The first part of this work illustrates the synthesis of luminescent Zn3P2 nanocrystals, an earth-abundant and a direct-gap semiconductor possessing high absorption coefficient and long carrier diffusion length, which uphold promising potential in many optoelectronic applications. A hot injection method by using highly reactive P and Zn precursors (P[Si(CH3)3]3 and diethyl zinc) in hexadecylamine and octadecene was developed to prepare a series of alkyl-amine-passivated tetragonal Zn3P2 crystallites with varying size sizes. Substantial blue shifts in the absorption onsets (2.11−2.73 eV) in comparison to the bulk counterpart (1.4−1.5 eV) and a clear red shift with increasing particle size indicates the quantum confinement effects. This is also consistent with the photoluminescent studies with the size-tunable maxima in the visible region (469−545 nm) as a function of growth temperature and time. The phase purity and alkyl-amine passivation of the nanocrystals were determined by structural and surface analysis, confirming the presence of N–Zn and N–P bonds on the tetragonal Zn3P2 crystallites.
The second part of this works focuses on the development of a colloidal synthetic strategy of alkyl-amine capped Si1-xGex nanocrystals with control over size- and composition-dependent optical properties. Despite their high miscibility at all compositions, developing a wet-chemical synthesis of Si1-xGex alloys in the nanoscale remains a challenging task, owing to the difference of their crystallization temperatures and the high surface oxidation of Si. Thus an adapted colloidal method is utilized to fabricate single-element Ge and Si nanocrystals. Powder X-ray diffraction indicates successful production of cubic crystalline Ge and amorphous Si nanoparticles individually in oleylamine/octadecene (surfactant/solvent) mixture at 300°C. Absorption onset values of 1.28 eV and 3.11 eV are obtained for resulting Ge and Si colloids, respectively. By alloying these two materials in their nano-regime, tunable optical properties can be achieved throughout the visible to the near IR region by simply varying their elemental compositions. The success of this bandgap engineering process offers more options for new material design by taking advantage of unique properties from each component material.
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Keng, Pei Yuin. « Synthesis, Assembly and Colloidal Polymerization of Polymer-Coated Ferromagnetic Cobalt Nanoparticles ». Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/193639.
Texte intégralRésumé :
This dissertation describes a novel methodology to prepare, functionalize, and assemble polymer-coated ferromagnetic cobalt nanoparticles (PS-CoNPs) and cobalt oxide nanowires. This research demonstrated the ability to use dipolar nanoparticles as `colloidal monomers' to form electroactive 1-D mesostructures via self- and field-induced assembly. The central focus of this dissertation is in developing a novel methodology termed as `Colloidal Polymerization', in the synthesis of well-defined cobalt oxide nanowires as nanostructured electrode materials for potential applications in energy storage and conversion.Ferromagnetic nanoparticles are versatile building blocks due to their inherent spin dipole, which drive 1-D self-assembly of colloids. However, the preparation and utilization of ferromagnetic nanoparticles have not been extensively examined due to the synthetic challenges in preparing well-defined materials that can be easily handled. This dissertation has overcome these challenges through the hybridization of polymeric surfactants with an inorganic colloid to impart functionality, colloidal stability and improved processing characteristics. This modular synthetic approach was further simplified to prepare ferromagnetic nanoparticles in gram scale, which enabled further investigations to develop new chemistry and materials science with these materials. These polymer-coated magnetic nanoparticles self-assembled into extended linear chains due to strong dipolar attractions between colloids. Additionally, novel dipolar assemblies, such as, flux-closure nanorings and lamellae type mesostructures were demonstrated by controlling the interparticle of attractive forces (dipolar versus van der Waals).The research presented herein focused on utilizing polymer-coated ferromagnetic cobalt nanoparticles as `colloidal molecules' to form interconnected 1-D mesostructures via `Colloidal Polymerization'. This process exploited the magnetic organization of dipolar colloids into 1-D mesostructures followed by a facile oxidation reaction to form interconnected electroactive cobalt oxide nanowires. This facile and template free approach enabled the large scale synthesis of semiconductor cobalt oxide nanowires, in which the electronic and electrochemical properties were confirmed for potential applications for energy storage and conversion. This work served as a platform in fabricating a wide range of semiconductor heterostructures, which allowed for structure-property investigation of new nanostructured electrodes.
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Pang, Yingping. « 2D Colloidal Atomic-Thick Metal Chalcogenides : Synthesis, Growth Mechanisms and Applications ». Thesis, Curtin University, 2019. http://hdl.handle.net/20.500.11937/80107.
Texte intégralRésumé :
In this thesis, we investigated a wide scope of atomically thin two-dimensional (2D) metal chalcogenide nanoparticles in terms of their synthetic methods, optical properties, and applications. A series of 2D metal chalcogenides, including ZnS, ZnSe, MoS2, WS2, and ReS2, were synthesized and their growth mechanisms (ZnS, ZnSe and MoS2) were elucidated underpinned by the theoretical simulations. The potential applications of such 2D nanoparticles in photodetection (ZnSe) and hydrogen evolution reaction (MoS2) were also systematically investigated, demonstrating their great potential in optoelectronic devices and solar-driven clean fuel production.
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GONCALVES, GUILHERME. « Colloidal synthesis and characterization of two- and three-dimensional semiconductor nanocrystals ». Doctoral thesis, Università degli studi di Genova, 2018. http://hdl.handle.net/11567/930563.
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Huba, Zachary. « Synthesis and characterization of cobalt carbide based nanomaterials ». VCU Scholars Compass, 2014. http://scholarscompass.vcu.edu/etd/3320.
Texte intégralRésumé :
Permanent magnets are used heavily for multiple applications in industry and current electronic technologies. However, the current permanent landscape is muddled by high cost of materials and insufficient magnetic or thermal properties. The primary focus of this dissertation work is the synthesis and optimization of a new permanent magnetic material, in the form of cobalt carbide nanomaterials. The optimization revolved around controlling the crystal phase and particle shape of synthesized cobalt carbide particles; these parameters have significant impact on the observed magnetic properties of magnetic nanoparticles. Co3C was identified to be the preferred crystal phase, leading to better magnetic properties. Cobalt Fumarate was found to be the ideal precursor to synthesize anisotropic Co3C particles and enhance magnetic properties of the synthesized cobalt carbide particles. Lastly, an ethanol based reduction system was employed to develop the greener synthesis of Co and Ni magnetic particles.
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Berestok, Taisiia. « Assembly of colloidal nanocrystals into porous nanomaterials ». Doctoral thesis, Universitat de Barcelona, 2018. http://hdl.handle.net/10803/663275.
Texte intégralRésumé :
This thesis focuses on different aspects of NCs colloidal synthesis, the exploration of the relevant surface chemistries that afford NC assembly and the NC implementation into porous nanomaterials.
The work is divided into two blocks. The first block is devoted to developing and optimizing the synthesis of NCs followed by the examination of their suitability for potential applications in catalysis and photocatalysis. The second block is dedicated to establish procedures to fabricate single-component or multicomponent porous nanomaterials from NC building blocks. To embrace the use of the developed strategies in different application fields, several kind of materials were under research. Namely, metals (e.g. Au), metal oxides (e.g. CeO2, TiO2, Fe2O3), metal chalcogenides (e.g. In2S3, ZnS, PbS, CuGaS2 and Cu2ZnSnSe4), and their composites.
CeO2 NCs synthesis was deeply investigated with the aim to achieve a proper control on the NCs morphology, facets exposed, crystal phase, composition, etc., required for application. Overall, CeO2 NCs with spherical, octapod-like branched, cubic hyperbranched, and kite-like morphology with sizes in the range 7 to 45 nm were produced by adjusting experimental conditions of the synthetic protocol. Branched and hyperbranched NCs showed higher surface areas, porosities and oxygen capacity storage values compared to quasi-spherical NCs.
The NCs morphology-controlled synthesis has been extended to quaternary Cu2ZnSnSe4 (CZTSe). CZTSe NCs with narrow size distribution and controlled composition were produced. It was shown how off-stoichiometric CZTSe compositions were characterized by higher charge carrier concentrations and thus electrical conductivities.
The strategy to functionalize the metal oxide NC surface composition by applying different ligands is proposed. This enables to develop a novel approach to assemble metal oxide NCs into porous gel and aerogel structures. Propylene oxide has been found to trigger the gelation process of glutamine functionalized NCs. The detailed investigation of the gelation mechanism is demonstrated for the case of ceria. The method is applied for NCs with different morphologies. Eventually, the versatility of the concept is proved by using of the proposed approach for the TiO2 and Fe2O3 nanocrystals.
The assembly method has been extended to metal chalcogenides - In2S3 NCs - starting from the NCs synthesis, with further surface chemistry manipulation and eventually follows by the NC assembly into gels and aerogels. The optimization of NC surface chemistry was achieved by testing different ligand exchange approaches via applying short-chain organic and inorganic ligands. The assembly method based on ligand desorption from the NC surface and chalcogenide-chalcogenide bond formation has been established for In2S3. The comparison of the different ligands impact on the NC performance in colloidal form, when assembled into gels and when supported onto substrate is investigated towards photoelectrocatalysis.
The oxidative ligand desorption assembly approach has been extended for multicomponent NCs for the case of CuGaS2 and CuGaS2-ZnS. Optimization of spin-coating process of the formed NCs inks followed by applying of sol-gel chemistry led to formation of highly porous layers from TGA-CuGaS2 and TGA-ZnS. Applied results of CuGaS2/ZnS nanocrystal-based bilayers and CuGaS2–ZnS nanocrystal-based composite layers have been shown by testing their photoelectrochemical energy conversion capabilities.
The approach to adjust NC surface chemistry has been proposed and tested for performing multicomponent NC assemblies. Applying of different ligands for NC surface functionalization endows their surface with different charges which usually provides colloidal NCs stabilization. It has been found that mixing of oppositely
charged NCs with certain concentration enabled their assembly/gelation via electrostatic interaction. The proposed approach has been applied and optimized to produce multicomponent NC gels and aerogels. The detailed investigation of the gelation mechanism is shown for combination of metal-metal oxide and metal oxide-metal chalcogenide NCs (Au-CeO2, CeO2-PbS). Applied results of the Au-CeO2 aerogels were demonstrated for CO-oxidation.Esta tesis se centra en la síntesis coloidal de nanocristales (NCs), en la exploración de su química de superficie y en su ensabanado en nanomateriales porosos funcionales. Para demostrar la versatilidad de aplicación de dichas estructuras, en este estudio se han considerado NCs de distintos tipos de materiales: metales (Au), óxidos metálicos (CeO2, TiO2, Fe2O3), calcogenuros metálicos (In2S3, ZnS, PbS, CuGaS2,Cu2ZnSnSe4) y sus materiales compuestos. El trabajo se dividió en dos bloques. En el primero se desarrolló y optimizó la síntesis de NCs de óxidos y calcogenuros metálicos y se evaluó su potencial para aplicaciones de catálisis y fotocatálisis. Se investigó en profundidad la síntesis de NCs de CeO2, poniendo énfasis en controlar su morfología. Se consiguió producir NCs de CeO2 de forma controlada (esférica, octapodo ramificado, cúbico ramificado y romboidal) y con tamaño controlado (7-45 nm). Asimismo, se obtuvieron NCs de Cu2ZnSnSe4 con una fina distribución de tamaños y composición controlada. En el segundo bloque se establecieron y estudiaron procedimientos para fabricar nanomateriales porosos mono- o multicomponentes a partir del ensamblado de NCs. Se desarrolló una estrategia basada en el ajuste de la química de superficie de NCs de óxidos metálicos (CeO2, Fe2O3,TiO2) y de calcogenuros metálicos (In2S3, CuGaS2-ZnS) que permitió su ensamblaje controlado en estructuras porosas de tipo gel y aerogel. En el caso de los óxidos metálicos, se determinó que el ensamblado se inicia con la adición de un epóxido a NCs funcionalizados con glutamina, causando la gelación. La desorción oxidativa de ligandos basada en la formación de enlaces calcogenuro-calcogenuro se propuso como mecanismo de gelación en calcogenuros mono- (In2S3) y multicomponente (CuGaS2-ZnS). Se investigó el impacto del empleo de distintos ligandos en la eficiencia foto-electrocatalítica de NCs en forma coloidal, ensamblados en geles y soportados en sustratos. Se desarrolló y estudió el ajuste de la química de superficie de NCs para la obtención de ensamblajes multicomponente mediante interacción electrostática de coloides en suspensión. El mecanismo de gelación fue investigado al detalle para materiales compuestos de NCs de oxido metálico (CeO2) con NCs de óxido de calcogenuro (PbS-CeO2) y metálicos (Au-CeO2). Los aerogeles de Au-CeO2 demostraron potencial para la oxidación de CO.
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Xu, Lianbin. « Fabrication of Three-Dimensionally Ordered Nanostructured Materials Through Colloidal Crystal Templating ». ScholarWorks@UNO, 2005. http://scholarworks.uno.edu/td/156.
Texte intégralRésumé :
The void spaces in colloidal crystals (opals, three-dimensional (3D) close-packed arrays of silica nanospheres) and their replicas are used as templates in the fabrication of new nanostructured materials. 3D ordered nanomeshes and nanosphere arrays are readily obtained by chemical and/or electrochemical methods. Using silica opal templates, metals or polymers are infiltrated into the interstices between the silica nanospheres. Subsequent dissolution of the opals with HF solution produces open 3D mesh structures. Metal (such as Ni, Co, Fe, Pd, Au, Ag, and Cu) and conductive polymer (such as polyaniline) meshes are obtained by electrochemical deposition approach, while the nonconductive polymer (such as poly(methyl methacrylate) (PMMA)) meshes are synthesized by chemical polymerization method. Some new types of meshes are fabricated by the conversion of metal meshes and polymer meshes. NiO meshes are formed by oxidizing Ni meshes in the air. The NiO meshes exhibit higher volume occupation fraction than Ni meshes and the nanocrystalline sizes of NiO particles can be adjusted by the oxidation temperature. Due to the mechanical flexibility of polymer meshes, the compression of PMMA meshes produces deformed PMMA meshes which contain oblate pores. These meshes can be again served as templates to prepare new types of colloidal crystals (nanosphere arrays) and specific nanocomposites. By the use of poorly conductive NiO mesh or PMMA mesh arrays as templates, 3D periodic metal nanosphere arrays, such as those of Ni, Co, Au and Pd, are readily fabricated by the electrodeposition method. Metal/NiO or Metal/PMMA composites can also be obtained if the templates are left intact. The magnetic behavior of metal (such as Ni and Co) meshes and sphere arrays has been investigated. These nanoscale arrays show significantly enhanced coercivities compared with bulk metals, due to the size effect of the nanometer dimensions of the components in meshes and sphere arrays. Angle-dependent magnetic properties of Ni and Co sphere array membranes exhibit out-of-plane anisotropy.