Thèses sur le sujet « TiO2 nanocomposite »

Thermophysiological comfort is one of the most important factors for people to choose desirable gar-ments, which can be evaluated via measuring permeability of body heat and sweat. In this paper the water vapor permeability of nanocomposite nylon 6 fabrics produced from melt spun nanocomposite yarns with different TiO2 nanoparticle concentrations have been investigated. Results from measuring water vapor permeability at different environment temperatures for 4 h. indicated that sample with 0.4 wt% of TiO2 nanoparticle can provide fabric with maximum comfort properties. At low temperature 27.5% decline of permeability as compared to pure fabric causes this sample to protect body from cool weather through pre-venting loss of body heat. By increasing temperature from 12 to 35 oC water vapor permeability enhance-ment of nanocomposite improved about 99% as compared to pure one. Consequently nanocomposite with suitable nanoparticle content can provide more comfortable fabrics in different temperatures and applica-tions. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35603

Mestrado em Ciência e Engenharia de Materiais
Os efeitos resultantes da hidrofilicidade de compósitos TiO2-SiO2 com diferente reatividade e composição química em processos sol-gel têm sido descritos na literatura. Esses resultados mostram que formulações sol-gel menos reativas originam super-hidrofilicidade, isto é, um ângulo de contacto inferior a 10° após envelhecimento superior a 8 semanas (envelhecimento em condições ambiente). Tendo em conta a morfologia de derivados de filmes compósitos e diferentes modelos termodinâmicos de superficie, sugere-se que um filme compósito com uma textura mais porosa poderá levar a um efeito de super-hidrofilicidade superior. Para verificar esta hipótese, neste projeto optou-se por estudar em detalhe compósitos TiO2-SiO2 mais reativos com diferentes composições (0, 20, 60 e 100 mol% de SiO2), em que a uma maior reatividade sol-gel é esperada uma redução da super-hidrofilicidade dos filmes compósitos. Com o objetivo de criar artificialmente uma morfologia rugosa/porosa, utilizaram-se neste caso camadas de esferas de poliestireno (PS) com um diâmetro médio de 0.6 μm. Com o objetivo de definir as melhores condições para obter camadas compactas 2D de esferas de PS foram estudados diferentes parâmetros no método de revestimento spin-coating. Realizaram-se experiências com diferentes velocidades de rotação (1000rpm e 500rpm). Outros parâmetros de deposição por spin-coating ajustados foram a rotação a 5000rpm/s, tempo de rotação de 1s, concentração de esferas de PS a 1wt% em EtOH, e um volume de 100μL para a solução de PS. As camadas 2D de PS foram posteriormente impregnadas em sóis de TiO2-SiO2. A utilização de esferas de PS permitiu obter filmes compósitos de TiO2-SiO2 com rugosidade aproximadamente cem vezes superior aos filmes compósitos obtidos na ausência das esferas de PS. Estas características morfológicas foram confirmadas por microscopia ótica, microcopia eletrónica (SEM) e microscopia de força atómica (AFM). Por sua vez, medições do ângulo de contacto mostraram que a hidrofilicidade aumenta após as modificações morfológicas efetuadas e, nos melhores casos (amostras com 20-60 mol% de SiO2), os ângulos de contacto de água obtidos foram inferiores a 5o, após 6 semanas de envelhecimento (sob condições ambiente). Este estudo mostrou igualmente que nestes casos existe uma relação entre: 1) o revestimento da superfície das esferas de PS, 2) a rugosidade/porosidade da superfície dos filmes S1-X+PS, e 3) a persistência da super-hidrofilicidade.
Enhanced hydrophilicity effects arising from TiO2-SiO2 granular interfaces in composite films deposited via sol-gel routes have been studied before. Results obtained so far have shown that sol-gel formulations yielding less reactive sols lead to enhanced super-hydrophilicity persistence of composite films, i.e. a water contact angle less than 10o after aging for more than 8 weeks (aging under ambient conditions without UV radiation). Taking into account the morphology of derived composite films and different surface thermodynamics models, we have suggested that a more rough/porous structure of the composite film might even increase this enhanced hydrophilicity effect. To verify this hypothesis, we have chosen to study more reactive TiO2-SiO2 composite sols with different compositions (0, 20, 60 and 100mol% of SiO2). This greater sol-gel reactivity is expected to reduce the natural super-hydrophilicity of composite films in order to better assess eventual effects of the morphology. Then, in order to artificially create rough/porous morphologies, we have used polystyrene (PS) beads with average diameter of 0.6μm. Different parameters of spin-coating deposition method were tested to define the best conditions to obtain 2D layers of closely packed PS beads. Further, two experiments with different rotation speeds (1000rpm and 500rpm) were performed. Other spin-coating conditions were fixed as follows: acceleration of 5000rpm/s, rotation time of 1s, concentration of PS beads 1wt% in EtOH, volume of PS solution 100μL. Such 2D PS layers were then impregnated with TiO2-SiO2 composite sols. Using PS beads, we have obtained TiO2-SiO2 composite films with a roughness that is almost 100 times higher than composite films without PS beads. These morphology features are confirmed by optical microscopy, AFM and FEG-SEM measurements. Water contact angle measurements show in turn that the hydrophilicity effects are increased by morphologic modifications, and in the best cases (samples with 20-60mol% of SiO2) water contact angles are close to 5o after 6 weeks of aging under ambient conditions without UV radiation. This study also shows that, in these cases, there is some relation between: 1) the surface coverage of PS beads, 2) the surface roughness/porosity of S1-X+PS films, and 3) their super-hydrophilicity persistence.

Water, together with energy and food, has been addressed as one of the main urgent problem of humanity. The reduction of fresh clean water sources will definitely lead to huge issues in the next future, especially in developing countries. The conventional wastewater treatments suffer some limitations related to the effectiveness in decontamination (mechanical filtration), in the heavy use of chemicals (chlorination), or in elevate operational costs and energy requirements (desalination and reverse osmosis). In this sense, new materials such as nanocomposites may overcome these issues taking advantage of the peculiar properties of materials at nanoscale. Research on novel nanotechnologies must bring advances in order to contrast and prevent water scarcity and pollution. In order to be effective, these nanotechnologies should run at low operational cost, even in places unequipped by strong infrastructures and in concert with conventional cheap methodologies. Among the alternative water purification methods, TiO2-based photocatalysis has attracted great attention due to material stability, abundance, non-toxicity and high decontamination efficiency. In this material, electron-hole pairs, generated by light absorption, separate from each other and migrate to catalytically active sites at the surface of the photocatalyst. Photogenerated carriers are able to induce the water splitting reaction and, consequently, to decompose organic pollutants. The main deficiency of this material, related to its large band gap, is that only the UV fraction of the solar spectrum is effective to this purpose. Several approaches have been proposed to overpass this issue and, among them, the use of metal-TiO2 nanocomposites with proper nanostructurarion seems very promising for water purification strategies. Aim of this work is to investigate the possibility to develop efficient solar-driven TiO2 photocatalyst taking advantage of metallic nanostructures to efficiently couple the incident light to the photoactive semiconductor. Two approaches have been followed: TiO2 nanoparticles obtained via pulsed laser ablation in liquid and optical engineering of multilayered metal-TiO2 thin films. The first approach maximizes the exposed surface, thus enhancing the photocatalytic efficiency. However, in this case nanomaterials is dispersed in the surrounding environment, and in order to avoid this drawback we have investigated, as second approach, the use of metal-TiO2 thin films.

Thesis (MScEng)--Stellenbosch University, 2013.
ENGLISH ABSTRACT: The purpose of this study was to develop modi ed tract-etched membranes using nanocomposite TiO2 for advanced water treatment processes. Photocatalytic oxidation and reduction reactions take place on TiO2 surfaces under UV light irradiation, therefore sunlight and even normal indoor lighting could be utilised to achieve this effect. In membrane ltration, caking is a major problem, by enhancing the anti-fouling properties of photocatalysts to mineralise organic compounds the membrane life and e ciency can be improved upon. In this study the rst approach in nanocomposite membrane development was to directly modify the surface of polyethylenetherephthalate (PET) track-etched membranes (TMs) with titanium dioxide (TiO2) using inverted cylindrical magnetron sputtering (ICMS) for TiO2 thin lm deposition. The second approach was rst to thermally evaporate silver (Ag) over the entire TM surface, followed by sputtering TiO2 over the silver-coated TM. As a result a noble metal-titania nanocomposite thin lm layer is produced on top of the TM surface with both self-cleaning and superhydrophilic properties. Reactive inverted cylindrical magnetron sputtering is a physical vapour deposition method, where material is separated from a target using high energy ions and then re-assimilated on a substrate to grow thin lms. Argon gas is introduced simultaneously into the deposition chamber along with O2 (the reactive gas) to form TiO2. The photocatalytic activity and other lm properties, such as crystallinity can be in uenced by changing the sputtering power, chamber pressure, target-to-substrate distance, substrate temperature, sputtering gas composition and ow rate. These characteristics make sputtering the perfect tool for the preparation of di erent kinds of TiO2 lms and nanostructures for photocatalysis. In this work, the utilisation of ICMS to prepare photocatalytic TiO2 thin lms deposited on track-etched membranes was studied in detail with emphasis on bandgap reduction and TM surface regeneration. Nanostructured TiO2 photocatalysts were prepared through template directed deposition on track-etched membrane substrates by exploiting the good qualities of ICMS. The TiO2-TM as well as Ag-TiO2-TM thin lms were thoroughly characterised. ICMS prepared TiO2 lms were shown to exhibit good photocatalytic activities. However, the nanocomposite Ag-TiO2 thin lms were identi ed to be a much better choice than TiO2 thin lms on their own. Finally a clear enhancement in the photocatalytic activity was achieved by forming the Ag-TiO2 nanocomposite TMs. This was evident from the band-gap improvement from 3.05 eV of the TiO2 thin lms to the 2.76 eV of the Ag-TiO2 thin lms as well as the superior surface regenerative properties of the Ag-TiO2-TMs.
AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om verbeterde baan-ge etste membrane (BMe) met behulp van nano-saamgestelde titaandioksied (TiO2) vir gevorderde water behandeling prosesse te ontwikkel. Fotokatalitiese oksidasie- en reduksie reaksies vind plaas op die TiO2 oppervlaktes onder UV-lig bestraling, en dus kan sonlig en selfs gewone binnenshuise beligting gebruik word om die gewenste uitwerking te verkry. In membraan ltrasie is die aanpaksel van onsuiwerhede 'n groot probleem, maar die verbetering van die self-reinigende eienskappe van fotokatalisators deur organiese verbindings te mineraliseer, kan die membraan se leeftyd en doeltre endheid verbeter word. In hierdie studie was die eerste benadering om nano-saamgestelde membraan ontwikkeling direk te verander deur die oppervlak van polyethylenetherephthalate (PET) BMe met 'n dun lagie TiO2 te bedek, met behulp van reaktiewe omgekeerde silindriese magnetron verstuiwing (OSMV).Die tweede benadering was eers om silwer (Ag) termies te verdamp oor die hele BM oppervlak, gevolg deur TiO2 verstuiwing bo-oor die silwer bedekte BM. As gevolg hiervan is 'n edelmetaal-titanium nano-saamgestelde dun lm laag gevorm bo-op die oppervlak van die BM, met beide self-reinigende en verhoogde hidro liese eienskappe. OSMV is 'n siese damp neerslag metode, waar materiaal van 'n teiken, met behulp van ho e-energie-ione, geskei word, en dan weer opgeneem word op 'n substraat om dun lms te vorm. Argon gas word gelyktydig in die neerslag kamer, saam met O2 (die reaktiewe gas), vrygestel om TiO2 te vorm. Die fotokatalitiese aktiwiteit en ander lm eienskappe, soos kristalliniteit, kan be nvloed word deur die verandering van byvoorbeeld die verstuiwingskrag, die druk in die reaksiekamer, teiken-tot-substraat afstand, substraattemperatuur, verstuiwing gassamestelling en vloeitempo. Hierdie eienskappe maak verstuiwing die ideale hulpmiddel vir die voorbereiding van die verskillende soorte TiO2 lms en nanostrukture vir fotokatalisasie. In hierdie tesis word OSMV gebruik ter voorbereiding van fotokatalitiese TiO2 dun lms, wat gedeponeer is op BMe. Hierdie lms word dan in diepte bestudeer, met die klem op bandgaping vermindering en BM oppervlak hergenerasie. Nanogestruktureerde TiO2 fotokataliste is voorberei deur middel van sjabloongerigte neerslag op BM substrate deur die ontginning van die goeie eienskappe van OSMV. Die TiO2-BM dun lms, sowel as Ag-TiO2-BM dun lms, is deeglik gekarakteriseer. OSMV voorbereide TiO2 dun lms toon goeie fotokatalitiese aktiwiteite. Nano-saamgestelde Ag-TiO2 dun lms is egter ge denti seer as 'n veel beter keuse as TiO2 dun lms. Ten slotte is 'n duidelike verbetering in die fotokatalitiese aktiwiteit bereik deur die vorming van die Ag-TiO2 nano-saamgestelde BMe. Dit was duidelik uit die bandgapingverbetering van 3,05 eV van TiO2 dun lms in vergelyking met die 2,76 eV van Ag-TiO2 dun lms. 'n Duidelike verbetering is behaal in die fotokatalitiese aktiwiteit deur die vorming van die Ag-TiO2 nano-saamgestelde TMs.

In this study, two different strategies were carried out to modify the polyvinylidene fluoride (PVDF) distillation membrane for desalination. The first strategy was the addition of TiO2 nanoparticles into the target membranes and a synergistic effect of hydrophilic and hydrophobic nanoparticles was found for the first time in this work. And the other strategy was the introduction of another polymer material, polytetrafluoroethylene (PTFE), to the PVDF membranes to fabricate a flat sheet PVDF-PTFE composite membrane and this is the first attempt that such a membrane to be made. Two types of membranes were characterized by scanning electron microscopy (SEM) detection, porosity measurement, energy dispersive X-ray spectroscopy (EDX), Attenuated total reflectance (ATR)-Fourier transformed infrared spectroscopy (FTIR), contact angle (CA) measurement, atomic force spectroscopy (AFM) detection and liquid entry pressure of water (LEPw) measurement. Their performance was evaluated by vacuum membrane distillation (VMD) experiments. And the best VMD pure water permeate flux of the membranes fabricated under these two modify strategies could achieve 4.26 kg/m2h (M-L5-B2) and 5.61 kg/m2h (M-40), respectively, when that of pure PVDF membrane is only 0.71 kg/m2h. The salt rejection of the prepared composite membranes are all stably higher than 99.5% which demonstrate their capacity for desalination.

La présence de bactéries et biofilms est une préoccupation permanente dans de nombreux domaines. Ils sont à l’origine de nombreux faits d’actualité qui ont un coût important pour le système de santé. L’objectif de notre travail visait à élaborer des films nanocomposite transparents contenant des particules métalliques nanométriques d'élément antibactérien (Ag ou Cu) immergées dans une matrice d’oxyde (TiO₂). La méthode de dépôt DLI-MOCVD (Direct Liquid Injection-Metal Organic Chemical Vapor Deposition) a été employée pour élaborer les films composites. Ce procédé permet le contrôle de la fraction molaire des précurseurs injectés dans le réacteur CVD et de revêtir des supports 3D (poreux). La croissance et la structure du dioxyde de titane (TiO₂) sont influencées par la présence du précurseur contenant l’élément antibactérien. La fraction molaire du précurseur (Ag ou Cu) modifie les caractéristiques physico chimiques et structurales des dépôts. L'activité antibactérienne est mesurée selon la norme JIS Z 2801:2000 avec S. aureus et E. coli en l’absence de lumière. Des essais antibactériens spécifiques ont été optimisés afin d'évaluer leur activité proche de condition réelle. La composition des dépôts influence fortement l’activité antibactérienne d’inactif à bactéricide. Des corrélations entre la microstructure et la composition des films et leurs propriétés antibactériennes sont discutées
The presence of bacteria and biofilms is permanent concern in many fields. Their presences are at the origin of many events which have high costs for the health system. In this objective, this work aimed to elaborate transparent nanocomposite thin films which are composed of nanometric metallic particles of antibacterial element (Ag or Cu) embedded in an oxide matrix (TiO₂). The DLI-MOCVD process (Direct Liquid Injection-Metal Organic Chemical Vapour Deposition) was used to elaborate these thin films. This process allows the quantity of precursors injected into the CVD reactor to be controlled and porous body to be coated. The growth mechanisms and the structure of the Titanium dioxide (TiO₂) are influenced by the presence of the organic precursor which contains the antibacterial element. The mole fraction of precursor (Ag or Cu) modifies the physico-chemical and structural properties of films. The antibacterial activity was tested according to the standard JIS Z 2801: 2000 with S. aureus and E. coli without light Specific tests were optimised in order to evaluate their activity in environments more representative. The composition of coatings impacts strongly the antibacterial activities from inactive to bactericidal properties. Correlations between the microstructure and composition of films and their antibacterial properties are discussed

The recent momentum in energy research has simplified converting solar to electrical energy through photoelectrochemical (PEC) cells. There are numerous benefits to these PEC cells, such as the inexpensive fabrication of thin film, reduction in absorption loss (due to transparent electrolyte), and a substantial increase in the energy conversion efficiency. Alpha-hematite ([U+F061]-Fe2O3) has received considerable attention as a photoanode for water-splitting applications in photoelectrochemical (PEC) devices. The alpha-hematite ([U+F061]-Fe2O3) nanomaterial is attractive due to its bandgap of 2.1eV allowing it to absorb visible light. Other benefits of [U+F061]-Fe2O3 include low cost, chemical stability and availability in nature, and excellent photoelectrochemical (PEC) properties to split water into hydrogen and oxygen. However, [U+F061]-Fe2O3 suffers from low conductivity, slow surface kinetics, and low carrier diffusion that causes degradation of PEC device performance. The low carrier diffusion of [U+F061]-hematite is related to higher resistivity, slow surface kinetics, low electron mobility, and higher electro-hole combinations. All the drawbacks of [U+F061]-Fe2O3, such as low carrier mobility and electronic diffusion properties, can be enhanced by doping, which forms the nanocomposite and nanostructure films. In this study, all nanomaterials were synthesized utilizing the sol-gel technique and investigated using Scanning Electron Microscopy (SEM), X-ray Diffractometer (XRD), UV-Visible Spectrophotometer (UV-Vis), Fourier Transform Infrared Spectroscopy (FTIR), Raman techniques, Particle Analyzer, Cyclic Voltammetry (CV), and Chronoamperometry, respectively. The surface morphology is studied by SEM. X-Ray diffractometer (XRD) is used to identify the crystalline phase and to estimate the crystalline size. FTIR is used to identify the chemical bonds as well as functional groups in the compound. A UV-Vis absorption spectral study may assist in understanding electronic structure of the optical band gap of the material. Cyclic voltammetry and chronoamperometry were used to estimate the diffusion coefficient and study electrochemical activities at the electrode/electrolyte interface. In this investigation, the [U+F061]-Fe2O3 was doped with various materials such as metal oxide (aluminum, Al), dichalcogenide (molybdenum disulfide, MoS2), and co-catalyst (titanium dioxide, TiO2). By doping or composite formation with different percentage ratios (0.5, 10, 20, 30) of aluminum (Al) containing [U+F061]-Fe2O3, the mobility and carrier diffusion properties of [U+F061]-hematite ([U+F061]-Fe2O3) can be enhanced. The new composite, Al-[U+F061]-Fe2O3, improved charge transport properties through strain introduction in the lattice structure, thus increasing light absorption. The increase of Al contents in [U+F061]-Fe2O3 shows clustering due to the denser formation of the Al-[U+F061]-Fe2O3 particle. The presence of aluminum causes the change in structural and optical and morphological properties of Al-[U+F061]-Fe2O3 more than the properties of the [U+F061]-Fe2O3 photocatalyst. There is a marked variation in the bandgap from 2.1 to 2.4 eV. The structure of the composite formation Al-[U+F061]-Fe2O3, due to a high percentage of Al, shows a rhombohedra structure. The photocurrent (35 A/cm2) clearly distinguishes the enhanced hydrogen production of the Al-[U+F061]-Fe2O3 based photocatalyst. This work has been conducted with several percentages (0.1, 0.2, 0.5, 1, 2, 5) of molybdenum disulfide (MoS2) that has shown enhanced photocatalytic activity due to its bonding, chemical composition, and nanoparticle growth on the graphene films. The MoS2 material has a bandgap of 1.8 eV that works in visible light, responding as a photocatalyst. The photocurrent and electrode/electrolyte interface of MoS2-[U+F061]-Fe2O3 nanocomposite films were investigated using electrochemical techniques. The MoS2 material could help to play a central role in charge transfer with its slow recombination of electron-hole pairs created due to photo-energy with the charge transfer rate between surface and electrons. The bandgap of the MoS2 doped [U+F061]-Fe2O3 nanocomposite has been estimated to be vary from 1.94 to 2.17 eV. The nanocomposite MoS2-[U+F061]-Fe2O3 films confirmed to be rhombohedral structure with a lower band gap than Al-[U+F061]-Fe2O3 nanomaterial. The nanocomposite MoS2-[U+F061]-Fe2O3 films revealed a more enhanced photocurrent (180 μA/cm2) than pristine [U+F061]-Fe2O3 and other transition metal doped Al-[U+F061]-Fe2O3 nanostructured films. The p-n configuration has been used because MoS2 can remove the holes from the n-type semiconductor by making a p-n configuration. The photoelectrochemical properties of the p-n configuration of MoS2-α-Fe2O3 as the n-type and ND-RRPHTh as the p-type deposited on both n-type silicon and FTO-coated glass plates. The p-n photoelectrochemical cell is stable and allows for eliminating the photo-corrosion process. Nanomaterial-based electrodes [U+F061]-Fe2O3-MoS2 and ND-RRPHTh have shown an improved hydrogen release compared to [U+F061]-Fe2O3, Al-[U+F061]-Fe2O3 and MoS2-[U+F061]-Fe2O3 nanostructured films in PEC cells. By using p-n configuration, the chronoamperometry results showed that 1% MoS2 in MoS2-[U+F061]-Fe2O3 nanocomposite can be a suitable structure to obtain a higher photocurrent density. The photoelectrochemical properties of the p-n configuration of MoS2-α-Fe2O3 as n-type and ND-RRPHTh as p-type showed 3-4 times higher (450 A/cm2) in current density and energy conversion efficiencies than parent electrode materials in an electrolyte of 1M of NaOH in PEC cells. Titanium dioxide (TiO2) is known as one of the most explored electrode materials due to its physical and chemical stability in aqueous materials and its non-toxicity. TiO2 has been investigated because of the low cost for the fabrication of photoelectrochemical stability and inexpensive material. Incorporation of various percentages (2.5, 5, 16, 25, 50) of TiO2 in Fe2O3 could achieve better efficiencies as the photoanode by enhancing the electron concentration and low combination rate, and both materials can have a wide range of wavelength which could absorb light in both UV and visible spectrum ranges. TiO2 doped with [U+F061]-Fe2O3 film was shown as increasing contacting area with the electrolyte, reducing e-h recombination and shift light absorption along with visible region. The [U+F061]-Fe2O3-TiO2 nanomaterial has shown a more enhanced photocurrent (800 μA/cm2) than metal doped [U+F061]-Fe2O3 photoelectrochemical devices.

Main aim of this work was the fabrication and characterization of polymeric TiO2 hybrid nanocomposites. When dispersed at the nanoscale level, TiO2 can tune the optical properties of the polymeric matrix, such as the UV absorption and the increase of refractive index, preserving the transparency in the visible and the flexibility of the polymer. TiO2 nanopaticles were modified on the surface with different molecules; they were then dispersed in MMA and polymerized in bulk, in order to obtain optically transparent TiO2/Poly-methylmethacrylate (PMMA) sheets. The application of these objects was in the solid-state lighting field, where the nanoparticles play the role of light diffusers according to Rayleigh Scattering. Films based on poly 2-ethyl-2-oxazoline (PEOX) and TiO2 nanoparticles with concentrations up to 44 % in weight were also prepared by casting from water solutions. Nanocomposites films remained highly transparent in the visible, and absorbed UV radiation up to the proximity of the visible range. The refractive indices of the films raised from about 1.52 to 1.65 with increasing of TiO2 concentration. The good optical properties and the solubility in water of these materials could allow their application in the paint and coating industry, and in the field of conservation of cultural heritage as consolidants or varnishes of paintings.

Ce travail concerne le domaine des cellules solaires sensibilisé à colorant à l’état solide et plus particulièrement le développement de nouvelles électrodes poreuses de TiO2 à base de nanocristaux synthétisés par pyrolyse laser. Deux types de poudres à base de TiO2 ont été synthétisés : TiO2 dopé à l’azote avec une teneur en azote contrôlée et des nanocomposites TiO2/MWNTC (Multi Wall Carbon Nanotubes). Dans le premier cas, le rendement des cellules élaborées varie en fonction de la teneur en N dans la poudre, cet effet étant relié à la localisation des atomes d’azote au sein du TiO2. Le dopage conduit à une augmentation du taux de recombinaison des charges. Cet effet limitant pour les performances, est partiellement compensé par une augmentation de la conductivité électrique avec le taux d’azote. Pour des taux de dopage modérés, les rendements des cellules sont ainsi sensiblement améliorés par rapport aux cellules à base de TiO2 non dopé. Concernant les nanocomposites TiO2/MWNTC, la synthèse par pyrolyse en une étape à partir d’une suspension contenant des MWCNT conduit à une dispersion très homogène des nanotubes au sein de la poudre de TiO2. La méthode favorise de plus l’enrobage des nanotubes par les particules d’oxyde, conduisant à des interactions électroniques efficaces. Les cellules solaires élaborées à partir de ce composite présentent des rendements améliorés de près de 20% par rapport aux cellules de référence. Cette amélioration est principalement attribuée à un drainage des charges photo-générées vers les électrodes favorisé en présence des nanotubes qui s’accompagne d’une réduction sensible des phénomènes de recombinaison
This work is related to the development of new TiO2 porous photo-electrodes based on nanopowders synthesized by laser pyrolysis for application in solid-state dye-sensitized solar cells. Two different types of TiO2 powders were synthesized: TiO2 nanoparticles doped with different levels of nitrogen, and TiO2/MWNTC (Multi Wall Carbon Nanotubes) nanocomposites. In the first case, the efficiency of the solar cells is dependent on the nitrogen amount in the powder, in relation with the localization of the dopants in the TiO2 structure. High nitrogen contents are associated with high defect densities at the TiO2 nanoparticle surface, leading to intense charge recombination. Although this effect limits the performance of the cells, it can be counterbalanced by an increased electrical conductivity due to the presence of N atoms. Finally, for moderate doping levels, the incorporation of nitrogen can improve the efficiency of the cells, compared to reference devices. Regarding the use of TiO2/MWNTC nanocomposites, the one step synthesis by laser pyrolysis from a precursor mixture including MWNTC leads to nanopowders where nanotubes appear very homogeneous dispersed of. The nanotubes are also highly coated with TiO2 particles, improving their electrical interactions with the TiO2 particles. The efficiencies of the solar cells made from such composites are found to be 20% larger than that of reference cells. This improvement is mainly attributed to faster charge collection and reduced charge recombination rates

Poly (o-anisidine) (POA) and also poly (o-anisidine)-TiO2 (POA-TiO2) nanocomposite coatings on aluminum alloy 3004 (AA3004) have been investigated by using the galvanostatic method. The electrosynthesized coatings were characterized by FT-IR, SEM- EDX, SEM and AFM. The corrosion protection performances of POA and also POA-TiO2 nanocomposite coatings were investigated in 3.5% NaCl solution by using the potentiodynamic polarization technique and electrochemical impedance spectroscopy (EIS). The corrosion rate of nanocomposite coatings was found ∼900 times lower than bare AA3004. The results of this study clearly ascertain that the POA-TiO2 nanocomposite has outstanding potential to protect the AA3004 against corrosion. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/34811

Nanotechnology has arisen as one of the most important fields in recent research, for the implications in both basic and applied science and technological applications. The manipulation of matter at the nanoscale is accompanied by the appearance of novel properties and large surface to volume ratio which can be exploited in a number of applications ranging from optics, catalysis and sensing, to name a few. In this work, we mainly focused on the synthesis and the use of nanomaterials for the preparation of nanocomposites and structures to be employed in the optical field. The main advantage of introducing nanosized inclusions in a host material is that specific functionalities or desired optical change can be imparted while transparency in the visible range can be retained. The whole activity can be divided in the synthesis and processing of nanoparticles and in their usage for some specific application. Cadmium selenide (CdSe), Titanium dioxide and layered titanates have been mainly addressed due to PL emission properties and high refractive index. In addition, zinc sulfide (ZnS) nanoparticles have been synthesized. CdSe nanoparticles (Quantum Dots) have been obtained by colloidal chemistry and part of the work has been spent in the synthesis of core-shell nanoparticles with a CdSe core and a shell of semiconductor materials with wider band gap in order to increase the stability of the emission properties of such materials. These nanoparticles were introduced in sol-gel derived ZrO2 waveguides to obtain materials showing optical gain which was characterized by ASE (Amplified Spontaneous Emission) experiments. High refractive index materials are useful in many optical applications. High refractive index depositions were obtained introducing Titania nanoparticles in proper matrices. A sol-gel synthesis for titanium dioxide nanoparticles has been developed yielding to anatase particles in the 3-5 nm range. These were embedded in an epoxy-based hybrid material obtaining transparent depositions with refractive index in the 1.51-1.89 range. Layered titanates were further addressed since they allowed extending the processing and engineering of titanium oxide materials. A synthetic colloidal procedure was developed, in which titanate nano-sheets are produced by reaction of a titanium alkoxide and an organic base. These materials allowed to obtained composites with multifumctional properties since materials embedding both titanate sheets and quantum dots could be obtained and applied in PL active waveguide and functional coating for LED devices to improve light extraction and produce white light through down-conversion. Coatings for LED were also developed using conventional sol-gel derived hybrid materials. The obtained layered titanates could also be modified and treated by UV curing, leading to material’s densification and enhancement of the refractive index at relatively low temperatures (200 °C). This processing behavior has been exploited in Bragg mirror fabrication and vertical optical microcavity incorporating quantum dots. The procedure employed for microcavity fabrication was found to be effective in keeping the optical properties of quantum dots, allowing for optical characterization of this structure. The properties of titanium dioxide have been exploited for optical gas sensing applications embedding gold nanoparticles in a crystalline TiO2 matrix. Anatase TiO2 particles have been successfully used as matrix material for this application. The employed preparation of such nanocomposites allowed tailoring of porosity and gold-titania interface which could be studied by optical measurements. Optical sensing was evidenced by variation in thin film absorbance at wavelengths near the plasmon resonance of gold nanoparticles caused by the presence of the gas analytes. Gold nanorods were introduced in the synthesized titanates. Gold nanorods are known to spheroidise upon thermal treatment, losing their peculiar optical properties. We found that the processing treatments developed for titanates resulted in improved thermal stability of such nanostructures as shown by optical measurements. This result is very interesting since it would allow extending gold nanorods’s exploitation in optical applications. Finally, composites with enhanced refractive index were realized by introducing ZnS nanoparticles in hybrid sol-gel material. A synthesis of ZnS nanoparticles has been developed, which allows nanoparticles functionalization and introduction in a hybrid organic-inorganic sol-gel matrix.
Il campo delle nanotecnologie è diventato tra i più importanti nella recente ricerca scientifica. È’ un settore multidisciplinare nelle conoscenze che ne costituiscono le basi e trova applicazione in svariati ambiti della tecnologia. La manipolazione della materia su nanometrica è accompagnata dalla comparsa di nuove proprietà ed un elevato valore di superficie per unità di volume. Queste proprietà possono essere sfruttate in applicazioni nei campi dell’ottica, della catalisi e della sensoristica, per non citarne che alcuni. In questo lavoro, l’attività è stata principalmente focalizzata sulla sintesi e l’uso di materiali nanostrutturati per la preparazione di nanocompositi e strutture di interesse nel campo dell’ottica. Il vantaggio principale nell’ introdurre particelle nanometriche in un materiale risiede nella possibilità di introdurre specifiche funzionalità o variazioni nelle proprietà ottiche mantenendo nello stesso tempo la trasparenza nel visibile. L’intera attività può essere divisa nella sintesi e successiva manipolazione di nanoparticelle e nel loro uso in specifiche applicazioni. Seleniuro di Cadmio (CdSe), Biossido di Titanio (TiO2) e Titanati a strati sono stati principalmente presi in considerazione per sfruttare specifiche proprietà di fotoluminescenza e di elevato indice di rifrazione. Sono inoltre state sintetizzate nanoparticelle di Solfuro di Zinco (ZnS). Nanoparticelle di CdSe, anche chiamate Quantum Dots (QDs), sono state ottenute attraverso sintesi di tipo colloidale. Parte del lavoro è stata dedicata al ricoprimento di queste nanoparticelle con semiconduttori a più elevato band gap con lo scopo di aumentare la stabilità delle proprietà di emissione di questi materiali. Queste nanoparticelle sono state introdotte in guide d’onda costituite da Biossido di Zirconio (ZrO2) ottenuto per via sol-gel per ottenere materiali con proprietà di guadagno ottico testate in esperimenti di emissione spontanea amplificata (ASE). Materiali ad alto indice di rifrazione trovano utilizzo in molte applicazioni ottiche. Deposizioni a elevato indice di rifrazione sono state ottenute introducendo particelle di biossido di titanio in opportune matrici. E’ stata sviluppata una sintesi di tipo sol-gel in grado di produrre soluzioni colloidali stabili di particelle cristalline con la struttura cristallografica dell’anatase con diametro intorno a 3-5 nm. Queste nanoparticelle sono state introdotte in una matrice ibrida sol-gel ottenendo deposizioni trasparenti con indice di rifrazione variabile tra 1.51 e 1.89. Sono stati successivamente presi in considerazione i titanati a strati perché permettono di estendere le possibilità di manipolazione ed ingegnerizzazione di materiali a base di ossido di titanio. È stata sviluppata una sintesi colloidale in cui “foglietti“ nanometrici di titanati sono prodotti per reazione di un alcossido di titanio e una base organica. Questi materiali hanno permesso di ottenere compositi con proprietà multifunzionali. Infatti, materiali contenenti titanati lamellari e QDs sono stati ottenuti e applicati in guide d’onda con proprietà di fotoluminescenza e ricoprimenti funzionali su dispositivi LED per migliorare la frazione di luce estratta e produrre luce bianca per conversione di parte della luce emessa in luce a lunghezza d’onda maggiore. Ricoprimenti per LED sono inoltre stati sviluppati con materiali ibridi sol-gel più convenzionali. I titanati stratificati sono stati trattati utilizzando radiazione UV. Questo genere di trattamento porta a una densificazione del materiale con conseguente aumento dell’indice di rifrazione impiegando durante il processo temperature relativamente basse (200 °C). Questo trattamento è stato impiegato nella fabbricazione di specchi multistrato dielettrici e cavità ottiche verticali dove sono stati inseriti QDs come emettitori luminescenti. Il metodo utilizzato è stato verificato essere compatibile con la conservazione delle proprietà di emissione dei Quantum Dots, permettendo la caratterizzazione ottica delle strutture sviluppate. Sono state inoltre considerate applicazioni sensoristiche per il rilevamento di gas tramite misure ottiche di materiali a base di TiO2 contenenti nanoparticelle d’oro. Le nanoparticelle di anatase in precedenza menzionate sono state adoperate come matrice, consentendo sia di agire sulla porosità, sia di caratterizzare l’interfaccia oro/titania tramite misure ottiche. La funzionalità sensoristica è stata determinata studiando la variazione nell’assorbanza ottica a lunghezze d’onda vicine alla risonanza plasmonica delle particelle d’oro, causata dalla presenza di uno specifico gas nell’atmosfera. Nanorods di oro sono stati inseriti in matrici di titanati lamellari. Queste nanostrutture d’oro tendono ad assumere la forma sferica in seguito a trattamento termico perdendo così le loro specifiche proprietà. Il trattamento di densificazione sviluppato per i titanati è stato applicato per questi compositi, fornendo una migliore stabilità termica dei nanorods, come dimostrato da misure ottiche. Questo risultato è interessante poiché potrebbe permettere di estendere l’utilizzo di queste nanostrutture in applicazioni ottiche. Infine, sono stati realizzati compositi con aumentato indice di rifrazione utilizzando particelle di solfuro di zinco per le quali è stata sviluppata una sintesi colloidale e una procedura di funzionalizzazione per il loro inserimento in matrici ibride sol-gel.

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In recent decades have seen a sharp growth in the study area of nanoscience and nanotechnology and is included in this area, the study of nanocomposites with self-cleaning properties. Since titanium dioxide (TiO2) has high photocatalytic activity and also antimicrobial, self-cleaning surfaces in your application has been explored. In this study a comparison was made between two synthesis routes to obtain TiO2 nanoparticles by hydrothermal method assisted by microwave. And after analysis of XRD and SEM was considered the best material for use in nanocomposites. It was deposited nanocomposite film of poly (dimethyl siloxane) (PDMS) with 0.5, 1, 1.5 and 2% by weight of nanoparticles of titanium dioxide (TiO2) by the spraying method. The nanocomposite was diluted with hexane and the suspension was deposited onto glass substrate, followed by curing in an oven with forced air circulation. The photocatalytic activity of the nanocomposite impregnated with methylene blue was evaluated by UV- vis spectroscopy from the intensity variation of absorption main peak at 660nm with time of exposure to the UV chamber. Changes in the contact angle and microhardness were analyzed before and after UV aging test. The effect of ultraviolet radiation on the chemical structure of the PDMS matrix was evaluated by spectrophotometry Fourier transform infrared (FTIR).The results indicated that the addition of TiO2 nanoparticles in the coating PDMS gave high photocatalytic activity in the decomposition of methylene blue, an important characteristic for the development of self-cleaning coatings
Nas ?ltimas d?cadas tem-se observado um crescimento acentuado no estudo da ?rea de nanoci?ncia e nanotecnologia em que inclui-se nessa ?rea, o estudo de nanocomp?sitos com propriedades autolimpantes. Desde que o di?xido de tit?nio (TiO2) apresenta alta atividade fotocatal?tica e tamb?m, atividade antimicrobiana, sua aplica??o em superf?cies autolimpantes tem sido amplamente explorada. Neste trabalho foi feito uma compara??o entre duas rotas de s?ntese para obten??o de nanopart?culas de TiO2 pelo m?todo hidrot?rmico assistido por micro-ondas. Ap?s an?lise de DRX e MEV foi analisado o melhor material para aplica??o em nanocomp?sitos. Foram depositados filmes de nanocomp?sito de poli(dimetil siloxano) (PDMS) com 0,5, 1, 1,5 e 2% em massa de nanopart?culas de di?xido de tit?nio (TiO2) pelo m?todo de aspers?o. O nanocomp?sito foi dilu?do em hexano e a suspens?o foi depositada sobre l?minas de vidro, seguida de cura em estufa com circula??o for?ada de ar. A atividade fotocatal?tica do nanocomp?sito impregnado com azul de metileno foi avaliada pela t?cnica de espectroscopia de UV-V?sivel, a partir da varia??o da intensidade de absor??o do pico principal a 660 nm com o tempo de exposi??o em c?mara UV. Altera??es no ?ngulo de contato e na microdureza foram analisadas antes e ap?s o ensaio de envelhecimento UV. O efeito da radia??o ultravioleta na estrutura qu?mica da matriz de PDMS foi avaliado por espectrofotometria no infravermelho por transformada de Fourier (FTIR). Os resultados indicaram que a adi??o das nanopart?culas de TiO2 em PDMS conferiram ao revestimento boa atividade fotocatal?tica na decomposi??o do azul de metileno, caracter?stica importante para o desenvolvimento de revestimentos autolimpantes

Metal coordinated polymer nanocomposites have gained great attention due to their superior characteristics. Polymethylmethacyrlate (PMMA) is the most commonly used polymer since it is easily processed. In this study, modified TiO2 nanoparticles prepared by insitu and exsitu methods were embedded into PMMA in order to improve its thermal stability and the effects of TiO2 nanoparticles on thermal characteristics of PMMA were investigated by direct pyrolysis mass spectrometry. The insitu method which is a sol gel method, TiO2/SiO2 nanoparticles were synthesized by mixing titanium(IV) tetraisopropoxide, TTIP, with silane coupling agent, 3-(3-methoxysilyl)methylmetacrylate, MSMA in absolute ethanol. In exsitu method, TiO2 powder was directly mixed with silane coupling reagent. TiO2/SiO2 nanoparticles were embedded into the PMMA by direct mixing resulting in exsitu and insitu TiO2/SiO2/PMMA nanocomposites. The synthesized TiO2/SiO2/PMMA nanocomposites were characterized by TEM, ATR-FT-IR and analyzed for the investigation of their reaction mechanism and thermal characteristics by pyrolysis mass spectroscopy. iv TEM images confirmed the formation of TiO2/SiO2 nanoparticles and TiO2/SiO2/PMMA nanocomposites and indicated that the average particle size of TiO2/SiO2 nanoparticles was around 6 nm whereas average particle size of SiO2/TiO2/PMMA nanocomposites were around 25 nm. The increase in the size of nanoparticles is associated with incorporation of TiO2/SiO2 nanoparticles into PMMA matrix. ATR-FTIR spectrum of 5% TiO2/SiO2/PMMA nanocomposites showed the formation of TiO2/SiO2 nanopartciles clearly. Pyrolysis mass spectrometry analysis revealed that incorporation of TiO2/SiO2 nano- particles into PMMA resulted in higher thermal stability only for low weight percentage insitu TiO2/SiO2/PMMA. At high weight percentages a decrease in thermal stability was detected. On the other hand, in case of exsitu TiO2/SiO2/PMMA, contrary to our expectations a decrease in thermal stability was detected. The decrease in thermal stability was attributed to evolution of methacrylic acid during thermal degradation of silane groups.

Le développement de procédé évoluant à la pression atmosphérique représente un enjeu majeur dans le dépôt de couches minces nanocomposites. Parmi ces procédés, les Décharges à Barrières Diélectriques présentent l'avantage d'être un procédé vert sans effluent gazeux, pouvant facilement être intégrées dans une chaine de production industrielle. L'approche choisie pour la réalisation de couches minces nanocomposites repose sur l'injection sous forme d'aérosol d'une suspension colloïdale dans la DBD. Les nanoparticules semi-conductrices de TiO2 sont choisies et mise en suspension dans un alcool polymérisable tel que l'isopropanol. L’objectif de ce travail est de contrôler le transport des nanoparticules et la croissance de la matrice dans la DBD en vue de réaliser une couche mince nanocomposite.Différentes méthodes de formation de l'aérosol et de filtration sont évaluées, ainsi que différents gaz vecteur (Ar, N2). Dans tous les cas considérés, la décharge est filamentaire.L'estimation des valeurs des différentes forces s'exerçant sur une nanoparticule dans une DBD confortée par un modèle numérique à permis d'orienter les expérimentations. Il est ainsi possible, à partir des paramètres permettant de générer le plasma, d'influencer le dépôt des nanoparticules et la croissance de la matrice. Les dépôts obtenus sont analysés ex situ par microscopie électronique à balayage, spectroscopie infrarouge, Raman et à rayon X et in situ avec la diffusion laser.Dans le régime filamentaire considéré, nous montrons que le flux de gaz et la fréquence de la tension joue des rôles prépondérants sur le dépôt des couches minces nanocomposites. Cette étude a permis de mettre en évidence qu’une simple fréquence n’est pas suffisante pour déposer la couche mince nanocomposite. Cependant l’utilisation d’une double fréquence semble être la meilleure approche pour séparer le transport des nanoparticules de celui de la croissance de la matrice
Development of an atmospheric pressure process presents a major concern in the deposition of nanocomposites thin films. Among these processes, Dielectrics Barrier Discharges takes advantages to be green processes without gas effluent, which can be easily integrate in an industrial line production. The chosen approach for the nanocomposite thin film deposition is based on the injection of an aerosol of a colloidal suspension in the DBD. Semi-conductive TiO2 nanoparticles are chosen and put in suspension in a polymerizable alcohol as isopropanol. The objective of the present work is to control the transport of the nanoparticles as well as the matrix growth in the DBD in order to realize the nanocomposites thin film Different methods of the aerosol formation and filtration are evaluated, as well as the carrier gas (Ar, N2). In each case considered, the discharge works in filamentary. Estimating values of the different forces acting on the nanoparticles in a DBD comforted by a numerical model allowed to guide the experimentations. Thanks to the parameter which generated the plasma, it is possible to influence the nanoparticles deposition and the matrix growth. Depositions are ex situ analyzed by scanning electron microscopy, Infra-red, Raman, and X-ray spectroscopy and in situ by laser scattering. In the filamentary regime considered, we show that the gas flow rate and the frequency of the voltage play a dominant role on the deposition of nanocomposites thin films. This study allowed to highlight that a simple frequency is not enough to deposit the nanocomposite thin film. However, the use of a double frequencies seems to be the best way to separate the nanoparticles transport to the surface from that of the matrix growth

Este trabalho teve como objetivo obter nanocompósitos de nanotubos de carbono de paredes múltiplas (NTCPMs) com TiO2, e caracterizá-los quanto a sua estrutura, características ópticas e atividade fotocatalítica. Os nanocompósitos foram obtidos a partir de NTCPMs comerciais (Baytubes®), e dois diferentes TiO2: um comercial (P25) e um obtido na síntese de TiO2 tendo tetra propóxido de titânio (TTP) como precursor. Foram utilizados dois diferentes sistemas líquidos para a obtenção dos nanocompósitos NTCPM-TiO2: um, em pH ácido e outro, em pH alcalino. Os nanocompósitos obtidos a partir do TTP foram posteriormente tratados termicamente a 400 °C, 500 °C, 600 °C e 700 °C para formação de fases cristalinas de TiO2. Os nanocompósitos foram investigados quanto a sua atividade fotocatalítica, empregando-os como catalisadores na degradação do corante orgânico alaranjado de metila, em solução aquosa, sob radiação ultravioleta. Os resultados foram associados a características da estrutura dos nanocompósitos, utilizando técnicas como difração de raios X, microscopia eletrônica de varredura, microscopia eletrônica de transmissão, espectroscopia Raman e espectroscopia por infravermelho e área superficial específica. A caracterização óptica foi obtida por espectroscopia fotoluminescente e espectroscopia por refletância difusa. A análise térmica foi empregada para quantificar a presença de NTCPMs no nanocompósito empregado como catalisador. O desempenho fotocatalítico dos nanocompósitos foi correlacionado com o efeito do pH dos sistemas líquidos empregados na sua obtenção, natureza da interação (química e/ou física) entre nanotubo de carbono e TiO2, fases presentes no TiO2, energia do gap óptico e presença de defeitos estruturais no TiO2. A maior eficiência na fotocatálise foi observada nos nanocompósitos NTCPMs-TiO2 obtidos a partir do TiO2 comercial, e nos obtidos a partir do precursor TTP tratado termicamente a 500 °C, ambos em meio ácido. Estes resultados puderam ser associados às menores energias de transição e nível de defeitos no TiO2 nesses nanocompósitos, quando comparados aos demais.
This study aimed to obtain nanocomposites from multi-walled carbon nanotubes (MWCNTs) with TiO2, and characterize them according to their structure, optical properties and photocatalytic activity. The nanocomposites were obtained from commercial MWCNTs (Baytubes®) and two different types of TiO2: a commercial one (P25) and one obtained by synthesizing TiO2 with titanium tetra propoxide (TTP) as a precursor. Two different fluid systems were used for obtaining the MWCNT-TiO2 nanocomposites: one with acid pH and the other with alkaline pH. The nanocomposites obtained from TTP were subsequently heat treated at 400 °C, 500 °C, 600 °C and 700 °C to form crystalline phases of TiO2. The nanocomposites were investigated for their photocatalytic activity, employing them as catalysts in the degradation of organic methyl orange dye in an aqueous solution under ultraviolet radiation. The results were associated with the characteristics of the nanocomposites’ structure, using techniques such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, infrared spectroscopy, and specific surface area. Optical characterization was obtained by photoluminescence spectroscopy and diffuse reflectance spectroscopy. Thermal analysis was used to quantify the presence of MWCNTs in the nanocomposite employed as catalyst. The photocatalytic performance of the nanocomposites were correlated with the effect of the pH of the liquid systems employed for obtaining them, the nature of the interaction (chemical and/or physical) between the carbon nanotube and TiO2, the phases present in the TiO2, the optical energy gap and the presence of structural defects in TiO2. The highest photocatalytic efficiency was observed in the MWCNT-TiO2 nanocomposites obtained from commercial TiO2, and in those obtained from the TTP precursor heat treated at 500 °C, both in an acid medium. These results could be associated with the lower transition energy and level of defects in the TiO2 of these nanocomposites when compared to the other samples.

Mestrado em Engenharia de Materiais
O objectivo principal desta tese foi a preparação, caracterização e estudo de possíveis aplicações de novos nanocompósitos de TiO2/celulose. Numa primeira fase, os nanocompósitos de TiO2/celulose foram preparados a partir da síntese in situ do TiO2 na presença de fibras celulósicas. Para esta síntese estudaram-se os parâmetros experimentais que permitem controlar a hidrólise do tetracloreto de titânio (TiCl4) e ureia, na presença de fibras celulósicas. Através desta abordagem in situ verificou-se que a concentração de ureia permite controlar a quantidade de TiO2 e a fase cristalina nos nanocompósitos. Existem evidências que as fibras celulósicas promovem a nucleação e o crescimento das partículas de TiO2 na sua superfície, conferindo um perfeito revestimento das fibras com nanopartículas de TiO2, com percentagem de TiO2 entre 5,6 e 23% (m/m) dependendo das condições de síntese. Contudo uma contrariedade foi identificada após esta síntese, verificou-se que após exposição solar os nanocompósitos preparados adquiriram uma cor amarelada, o que pode ser indicativo da destruição das fibras da celulose devido às propriedades semicondutoras do TiO2. Para proteger o substrato da fotodegradação promovida pelo TiO2, estudaramse novas abordagens para a preparação deste tipo de materiais, nomeadamente ligação de nanopartículas de TiO2 (previamente sintetizadas) à fibra por método de deposição por camadas de polielectrólitos (em inglês Layer-by-Layer (LbL)). Esta abordagem foi aplicada não só a fibras não revestidas mas também a fibras previamente protegidas com diferentes silanos. Dependendo do tipo de silanos usados para proteger a fibra, novas propriedades dos nanocompósitos finais foram obtidas, em particular hidrofobicidade e estabilidade térmica. Os nanocompósitos e nanoparticulas foram caracterizados por, TEM, SEM, FTIR, TGA e DRX. Devido às propriedades intrínsecas do dióxido de titânio, estudou-se a possível aplicação destes materiais em fotocatálise e como agentes antibacterianos. Ambos os estudos revelaram que estes novos nanocompósitos possuem propriedades fotocatílticas e antibacterianas interessantes. Os nanocompositos de TiO2/celulose podem resultar em interessantes aplicações, como materiais de embalagem ou materiais funcionais, explorando assim as propriedades específicas do TiO2 tais como o elevado índice de refracção e as características semicondutoras. ABSTRACT: The aim of the present thesis was the preparation and characterization of TiO2/cellulose nanocomposites. TiO2/cellulose nanocomposites were first prepared using an in situ methodology based on the controlled hydrolysis of titanium tetrachloride (TiCl4) and urea, in the presence of wood cellulosic fibres. There is evidence from this study that the urea concentration allows to control both the content of TiO2 and the crystalline phase in nanocomposites. Depending on the experimental conditions used, the cellulose fibres promoted the nucleation and growth of TiO2 particles on their surfaces, yielding homogeneously coated fibres with TiO2 content between 5.6 and 23.0% (w/w). However, one drawback was identified in these new nanocomposites, after light exposure the nanocomposites turned yellowish possibly due to degradation of cellulose fibres due to the photoactivity of TiO2 nanoparticles. To protect the substrate from the TiO2 photodegradation, two different chemical modifications of cellulose surface were performed: Layer-by-Layer (LbL) assembly with polyelectrolyte agents and silanization with functional silane agents. Depending on the type of silane used, new properties of nanocomposite materials were achieved like hydrophobicity and fire retardance. After this cellulose surface treatment, TiO2 nanoparticles were deposited on top of the protective layer. All the materials were characterized by TEM, SEM, FTIR, TGA and DRX. Due to the semiconductor properties of titanium dioxide, these new nanocomposites may find interesting applications namely in photocatalysis and antibacterial applications. Both applications were studied and showed that TiO2/cellulose nanocomposites may have good performances in those fields. TiO2/cellulose nanocomposites materials may have interesting applications, namely as fibres in composites for packing applications or as functional materials, exploring specific properties of TiO2 such as its high refraction index or its semiconductor nature.

Polymer nanocomposites are already a part of many important of worldwide businesses: automotive (molded part in cars), electronics and electrical engineering, household products, packaging industry, aircraft interiors, appliance components, security equipments. Among many nanocomposite precursors, TiO₂ nanopowder is increasingly being investigated due to its special properties.

The objective of this work is to synthesize and characterize polymer-TiO₂ hybrid nanocomposites. When dispersed at the nanoscale level TiO₂ could act as visually transparent UV filters and high-thermomechanical-performance materials. The synthesis strategy involved two steps. Firstly, aggregated TiO₂, as received, was modified by 3-trimethoxysilyl propylmethacrylate aimed at altering its surface characteristics. The effect of modifier concentration on changing the physicochemical properties of TiO₂ surface was evaluated. Size distribution of unmodified and modified TiO₂ nanopowders was measured using a particle size analyzer. The qualitative and quantitative grafting of vinyl groups on TiO₂ surface was investigated with Fourier transform-infrared (FTIR) and proton nuclear magnetic resonance (¹H-NMR) spectroscopy. Secondly, styrene monomer was then added to carry out copolymerization with vinyl groups on the modified TiO₂ by free radical initiator 2,2-azobis isobutyronitrile (AIBN) in bulk medium. FTIR spectra confirmed the formation of nanocomposites with polystyrene chains chemically linked to the surface of TiO₂ nanopowders. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) indicated that the resulting nanocomposites displayed higher thermal stability and maintained similar glass transition temperatures (T_g) compared with pure PS. Ultraviolet ?visible spectroscopy (UV-Vis) investigated that these nanocomposites have improved optical properties potentially acting as visually transparent UV filters. Such incremented properties were attributed to the nancoscale dispersion (20-50nm size) of TiO₂ into polystyrene matrix, which morphology was observed by scanning electron microscopy (SEM).

Orientador: Dayse Iara dos Santos
Resumo: O desenvolvimento de materiais cerâmicos é um campo de pesquisa cujos resultados são extremamente promissores para aplicações tecnológicas. Particularmente, no caso dos materiais nanoestruturados baseados no óxido titânio, observa-se grande potencial de aplicação em dispositivos optoeletrônicos, bem como, para processos de fotocatálise, visto que apresenta um bandgap direto de 3,2 eV. Além disso, o aperfeiçoamento das propriedades ópticas, por meio da interação entre óxidos de diferentes bandas eletrônicas, têm sido estudado por muitos autores. Por esta razão, compósitos nanoestruturados formados de dois ou mais óxidos, cujas propriedades são distintas quando isolados, têm sido sintetizados juntos e caracterizados a fim de avaliar possíveis interações sinérgicas. Neste trabalho, foram preparados e caracterizados os compósitos TiO2/CuO, TiO2/ZnO e TiO2/ZrO2. As sínteses foram realizadas pelo método Sol-gel original e pelo método Poliol modificado, e ambos os processos se mostraram propícios para a obtenção de nanocompósitos e óxidos nanoparticulados. O método Poliol produziu compósitos formados de partículas micrométricas de dióxido de titânio revestidas do segundo óxido, enquanto o processo Sol-gel resultou em material constituído de agregados de nanocristais com alta mesoporosidade. Por meio da difração de raios X dos pós tratados gradualmente até 1000 °C observou-se que a formação e cristalização dos óxidos ocorrem em temperatura mais alta quando o material é resultante do ... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The development of ceramic materials is a field of research whose results are extremely promising for technological applications. Particularly, in the case of nanostructured materials based on titanium oxide, there is a great potential for application in optoelectronic devices, as well as for photocatalysis processes, since it has a direct bandgap of 3.2 eV. In addition, the improvement of the optical properties through the interaction between oxides of different electronic bands has been studied by many authors. For this reason, nanostructured composites formed of two or more oxides, whose properties are distinct when isolated, have been synthesized together and characterized in order to evaluate possible synergistic interactions. In this work the TiO2 / CuO, TiO2 / ZnO and TiO2 / ZrO2 composites were prepared and characterized. The syntheses were carried out using the original Sol-gel method and the modified Polyol method, and both processes proved to be suitable for nanocomposites and nanoparticulate oxides. The polyol method produced composites formed of micrometric titanium dioxide particles coated with the second oxide, while the sol-gel process resulted in material composed of nanocrystalline aggregates with high mesoporosity. By X-ray diffraction of the powders gradually treated to 1000 °C it was observed that the formation and crystallization of the oxides occur at a higher temperature when the material is produced by the Sol-gel process. With the observation of the ... (Complete abstract click electronic access below)
Doutor

Two novel synthetic routes to formation of gold-magnetite nanoparticles have been designed. Treatment of preformed magnetite nanoparticles with ultrasound in aqueous media with dissolved tetrachloroauric acid resulted in the formation of gold-magnetite nanocomposite materials. The other route involved irradiation of preformed magnetite nanoparticles by UV light in aqueous media with dissolved tetrachloroauric acid. This method resulted in the formation of gold-magnetite nanocomposite materials. These materials maintained the morphology of the original magnetite particles. The morphology of the gold particles could be controlled by adjusting experimental parameters, like addition of small amounts of solvent modifiers such as methanol, diethylene glycol, and oleic acid as well as variation of the concentration of the tetrachloroauric acid solution and time of the reaction. The nanocomposite materials were magnetic and exhibited optical properties similar to gold nanoparticles. Since we were not able to directly synthesize core shell gold magnetite nanoparticles, TiO2 was used as a bridging material. TiO2 nanoparticles with embedded magnetite were suspended in aqueous HAuCl4 and irradiated with ultraviolet light to photodeposit gold. The degree of gold coating and the wavelength of absorbance could be controlled by adjusting concentration of HAuCl4. Absorbance maxima were between 540-590 nm. Particles exhibited superparamagnetic properties (blocking temperature ~170 K) whether or not coated with gold. These particles have potential applications as drug delivery agents, magnetic imaging contrast agents, and magnetically separatable photocatalysts with unique surface properties. Another goal was to synthesize and characterize indium doped magnetite nanoparticles for application as radiotracers for in vivo fate studies. The labeled particles will be useful for determination of pharmacological behavior in biological systems. Indium doped magnetite particles with varying size and surface chemistry were synthesized with wet chemical techniques. The synthesized nanoparticles were characterized in terms of the size and shape with the help of TEM, the elemental composition by ICP and EDS, the crystal structure by XRD and magnetic properties by SQUID measurements. It was found that the indium loading could be controlled even though the magnetic properties were similar to undoped magnetite.

Radiosensitization is a novel targeted therapy strategy where chemical compounds are being explored to enhance the sensitivity of the tissue to the effects of ionizing radiation. Among the different radiosensitizers alternatives, nanomaterials have shown promising results by enhancing tumor injury through the production of free radicals and reactive oxygen species (ROS). In this work, Gold-supported titania (Au@TiO2) nanocomposites were synthesized through an innovative strategy using X-ray irradiation, and their potential as radiosensitizers was investigated. Radiosensitization of Au@TiO2 nanocomposites was assessed by monitoring the decomposition of Methylene Blue (MB) under X-ray irradiation in the presence of the nanomaterial. Radiosensitization of Au@TiO2 was thoroughly investigated as a function of parameters such as Au loading, TiO2 particle size, nanomaterial concentration, different irradiation voltages, and dose rates. Results showed that the presence of Au@TiO2 increases significantly the absorbed dose, thus enhancing MB decomposition. The mechanism behind Au@TiO2 radiosensitization relies on their interaction with X-rays. TiO2 produces reactive ROS whereas Au leads to the generation of photoelectrons and Auger electrons upon exposure to X-rays. These species lead to an enhanced degradation rate of the dye, a feature that could translate to cancerous cells damage with minimal side effects. The radiosensitization effect of Au@TiO2 nanocomposites was also tested in biological settings using Microcystis Aeruginosa cells. The results showed an increase in cell damage when irradiated in the presence of Au@TiO2 nanocomposites. Au@TiO2 nanocomposites were fabricated using X-ray radiolytic synthesis, a method that diverges from conventional fabrication processes and leads to negligible by-product formation, an important feature for medical and catalytic applications. In this work, Au nanoparticles are supported on TiO2 with a mean particle size of either 6.5 nm or 21.6 nm, using different ligands such as NaOH or urea, and under different absorbed doses to determine the effects of these parameters on the nanomaterials’ characteristics. Overall, Au@TiO2 synthesized by X-rays showed remarkable promise as radiosensitizers, a concept relevant to a number of medical, biological and environmental applications.

Lack of potable water is one of the major challenges that the world faces currently and the effects of this are mainly experienced by people in developing countries. This has therefore propelled research in advanced oxidation technologies AOTs to improve the current water treatment methods using cost effective, non toxic and efficient treatment methods. Hence, in this study the sol-gel synthesis method was used to prepare TiO2 nanoparticles that were photocatalytically active under UV and visible solar light as well as possessing antibacterial properties. Silver and nitrogen doping was carried out to extend the optical absorption of TiO2. For easy removal and reuse of the photocatalyst the nanoparticles were immobilized on chitosan and poly (vinyl-alcohol-co-ethylene) using the electrospining technique. The synthesized nanomaterials were characterized by FTIR, XRD, SEM/EDS, TEM, DRS, and TGA. FTIR and EDS analysis confirmed the formation and composition of TiO2 nanopowders for the doped and undoped nanoparticles. XRD analysis showed that the anatase phase was the dominant crystalline phase of the synthesized nanopowders. SEM and TEM respectively illustrated the distribution and size of the electrospun nanofibers and the nanoparticles of TiO2. DRS results showed that there was a significant shift in the absorption band edge and wavelength of Ag-TiO2 to 397 nm, followed by N-TiO2 at 396 nm compared to the commercial titania which was at 359 nm. The photocatalytic activities and antibacterial properties of these materials were tested on methylene blue dye and E.coli microorganism respectively. Ag-TiO2 immobilized on nanofibers of chitosan and PVAE had the highest photocatalytic activity compared to N-TiO2. Similar results were observed when the biocide properties of these materials were tested on E. coli.

Des revêtements sol-gel nanocomposites TiO2-SiO2 ont été réalisés à partir de mélanges d'une suspension nanocristalline de TiO2 anatase et de sols polymériques de silice. Ces revêtements présentent une superhydrophilie naturelle, persistante et photo-régénérable. La présence de charges localisées aux interfaces granulaires TiO2-SiO2 est une des hypothèses permettant d'expliquer cette superhydrophilie naturelle. Toutefois des effets de morphologie (rugosité, porosité de surface) sont également connus pour influencer le mouillage. Des études ont été menées pour mettre directement en évidence l'effet intrinsèque des interfaces granulaires. Les études se sont recentrées sur l'effet extrinsèque de paramètres morphologiques susceptibles d'influencer la mouillabilité des revêtements nanocomposites selon des modèles thermodynamiques des surfaces connus. De nouveaux protocoles de synthèse par voie sol-gel ont été mis au point afin d'analyser i/ en quoi la superhydrophilie naturelle et photo-induite des revêtements TiO2-SiO2 pouvait être influencée par des effets de morphologie et de composition, et ii/ en quoi une exacerbation de ces effets via des structurations artificielles pouvaient encore accroître la superhydrophile de surface. Une extrapolation de ces protocoles a également permis d'étudier des revêtements superhydrophobes.

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
A rápida evolução tecnológica vem acompanhada da necessidade de se obter cada vez mais materiais com melhores desempenhos. Os materiais poliméricos, muito utilizados em nosso cotidiano devido as suas características de boa resistência, boa estabilidade química, fácil processabilidade e baixo custo, ainda são restritos para algumas aplicações devido as suas baixas propriedades mecânicas e térmicas, quando comparados ao aço. A fim de atender a essas características, os materiais compósitos à base de polímeros vêm ganhando um importante espaço. Muito já foi relatado sobre a eficiência da inclusão de cargas em escala nanométrica em uma matriz polimérica, para se obter melhoras nas propriedades térmicas e mecânicas. A poliamida 11, muito utilizada em aplicações offshore como revestimento de risers, é um exemplo de polímero que pode possuir melhores propriedades com a aplicação de reforços. Os nanotubos de titanato apresentam boas características mecânicas com módulo de Young em torno de 230 GPa e se apresentam como uma boa carga para nanocompósitos. Sendo assim, no presente trabalho foram fabricados compósitos à base de poliamida 11 com cargas de nanotubos de titanano (TTNT) e nanopartículas de TiO2. Os nanotubos utilizados possuem estrutura de trititanatos e as nanopartículas são do tipo comercial P-25 e foram utilizadas no intuito de comparar os resultados obtidos com os nanotubos, uma vez que estas possuem uma área superficial bem menor. Os nanocompósitos fabricados (A1, A2, A3 e A4) e a poliamida 11 pura (A0 e Ap) foram submetidos a ensaios de tração, termogravimetria (TGA) e microscopia eletrônica de varredura (MEV). Foi observada uma melhora significativa nas propriedades mecânicas para as amostras A1 e A3 e nas propriedades térmicas para as amostras A1, A3 e A4, quando comparadas com a poliamida pura.
The fast technological developments comes with the need to obtain more materials combined with better performance. Polimeric materials, commonly used in our daily because of its characteristics of good strength, good chemical stability, easy processability and low cost, are still restricted for some applications owing to their low mechanical and thermal properties compared to steel. In order to improve these characteristics, composite materials based on polymers are gaining an important space. Much has been reported on the effectiveness of inclusion of fillers at nanoscale in a polymer matrix, to obtain improvements in mechanical and thermal properties. The polyamide 11, widely used in offshore applications as coatings of risers, is one example of polymer which can has better properties with the use of reinforcement. The titanate nanotubes exhibit good mechanical properties with Young’s modulus around 230 GPa and appear as good nanocomposite reinforcement. In this study, polyamide 11 composites reinforced with titanate nanotubes (TTNT) and TiO2 nanoparticles were manufactured. The nanotubes used have trititanate structure and the nanoparticles are the commercial type P-25 and were used in order to compare the results with the nanotubes, as the nanoparticles have a smaller surface area. The nanocomposites produced (A1, A2, A3 and A4) and pure polyamide 11 (A0 and Ap) were submitted to tensile tests, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). A significant improvement on mechanical properties for samples A1 and A3 and for thermal properties in samples A1, A3 and A4 were observed when compared to pure polyamide.

Thesis submitted in fulfilment of the requirements for the degree Magister of Technology: Dental Technology In the Faculty of Health and Wellness Sciences At the Cape Peninsula University of Technology, 2012
A study of the modification of dental nanocomposites with nanosized fillers is presented. The incorporation of TiO2 (titania) nanoparticles, via a silane chemical bond, to a standard dental acrylic resin matrix was explored to determine whether there was an increase in the wear resistance, flexural strength and surface hardness properties of the dental nanocomposites. The principal aim of this study was to synthesize dental nanocomposites with different sizes, treated, nano-TiO2 fillers in urethane dimethacrylate (UDMA) for potential application in posterior restoration and to evaluate their mechanical properties. Treatment of the nano-TiO2 particles was carried out with a silane coupling agent, 3-(methacryloyloxy)propyltrimethoxysilane (MPTMS), to improve bonding between the nano-TiO2 particles and acrylic matrix (UDMA), and reduce agglomeration of the nano-TiO2. Characterisation of products was carried out using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and fourier transform infrared spectroscopy (FTIR). TEM results were used to compare the particle size distributions of untreated TiO2 and treated TiO2 under various experimental conditions in an ethanol solvent, while SEM images showed the adhesion between the matrix (UDMA) and the nano-TiO2. FTIR was used to show the qualitative composition of untreated TiO2 and treated TiO2. Eighteen groups of experimental dental nanocomposites were evaluated. Each group contained different average particle sizes of nano-TiO2 (filler): 5 nm, 21 nm and 80 nm. Each particle size category was treated with three different concentrations of the silane, (MPTMS): 2.5, 10 and 30 wt %. Samples were prepared by mixing the monomer resin matrix of UDMA and nano-TiO2 particles. For comparison, a commercially available dental resin was reinforced with untreated and treated nano-TiO2 particle sizes 5, 21 and 80 nm. Wear resistance, flexural strength and surface hardness of TiO2 nanocomposites treated with 2.5 wt % MPTMS were significantly higher compared to those treated with 10 and 30 wt% MPTMS. The nanocomposites with 5 nm TiO2 had higher wear loss, lower flexural strength and lower surface hardness values compared to those with 21 nm and 80 nm TiO2. Statistical analysis showed that the effect of the concentrations of MPTMS on wear resistance and surface hardness of specimens was significant (p<0.001), which is less than 0.05, while the effect of the concentration of MPTMS on flexural strength was statistically not significant, (p=0.02). Control composites reinforced with treated 80 nm TiO2 particles had much better mechanical properties than any of the other specimens. It was concluded that the most available commercial product for dental restorations could be improved by the addition of nano-TiO2 with relatively large particle size.

Orientador: Leinig Antônio Perazolli
Resumo: O presente trabalho buscou desenvolver fotocatalisadores cerâmicos por meio da produção de heterojunções inovadoras à base de SrTiO3, TiO2 e CaO, que tiveram suas fotoatividades avaliadas pela descoloração do corante Rodamina B (RhB) e pela obtenção de biodiesel, utilizando luz ultravioleta. As amostras TiO2, CaO e SrTiO3 foram obtidas pelo método de precursores poliméricos, método Pechini, e as heterojunções TiO2/SrTiO3, CaO/SrTiO3 e CaO/CaTiO3 foram preparados por rota sol-gel. Após síntese e tratamento térmico, as amostras foram caracterizadas por difração de Raios-X (DRX) para verificar as fases cristalinas formadas, por espectroscopia de infravermelho com transformada de fourier (FT-IR) e termogravimetria/análise térmica diferencial (TG/DTA) para verificar e quantificar a formação de CaCO3 e Ca(OH)2, por espectroscopia de refletância difusa (UV/Vis/NIR DRS) para determinar a energia de band gap, por Brunauer, Emmett e Teller (B.E.T.) para determinar a área específica, por microscopia eletrônica de varredura acoplada a espectroscopia de energia dispersiva de Raios-X (FE-SEMEDS) para estimar o tamanho das partículas, sua morfologia e composição elementar, por espectroscopia de fotoelétrons excitados por Raios-X (XPS) para conhecer a composição elementar presente na superfície da amostra e seus estados de oxidação, por espectroscopia de fotoluminescência (PL) para verificar a formação de defeitos estruturais, por microscopia eletrônica de transmissão de alta resolução (HRTE... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The present work aimed to develop ceramic photocatalysts through the production of innovative SrTiO3, TiO2 and CaO based heterojunctions, which had their photoactivities evaluated by the discoloration of Rhodamine B (RhB) dye and by obtaining biodiesel using UV light. TiO2, CaO and SrTiO3 samples were obtained by polymeric precursor method, Pechini method, and TiO2/SrTiO3, CaO/SrTiO3 and CaO/CaTiO3 heterojunctions were prepared by sol-gel route. After synthesis and heat treatment, the samples were characterized by X-ray diffraction (XRD) to verify the crystalline phases formed, fourier transform infrared spectroscopy (FT-IR) and thermogravimetry/differential thermal analysis (TG/DTA) to verify and quantify the formation of CaCO3 and Ca(OH)2, diffuse reflectance spectroscopy (UV/Vis/NIR DRS) to determine band gap energy, Brunauer, Emmett e Teller (B.E.T.) to determine specific area, field emission scanning electron microscopy coupled X-ray dispersive energy spectroscopy (FE-SEM-EDS) to estimate particle size, morphology and elemental composition, X-ray photoelectron spectroscopy (XPS) to know the elemental composition present on the sample surface and oxidation states, photoluminescence spectroscopy (PL) to verify the formation structural defects, high resolution transmission electron microscopy (HRTEM) to confirm the formation of heterojunction. Rhodamine B discoloration was measured by UV/Vis molecular absorption spectroscopy and the conversion of oil to biodiesel was analyz... (Complete abstract click electronic access below)
Doutor

The current energy crisis has driven the scientific research in a direction to find alternative options for fossil fuels. Solar energy is the most abundant and suitable for being the mainstream of the future renewable energy amongst other options. Therefore the research on photo-responsive material has been a major part of the solar energy related research. CNT/Ti02 nanocomposite as a promising candidate has attracted significant attention. In this thesis photoelectrochemical study was conducted in order to reveal the properties of the composites. A photoelectrochemical reactor was purposely designed and constructed for the current project after reviewing the design criteria and similar reactors in the literature. The composite synthesis procedure was improved in precision and consistency to ensure the product was more reproducible. The TEM, XRD and TGA data showed that the Ti02 precursors affected the thickness of the · Ti02 layer, the calcination characteristics and hence the CNT content of the final composite. The Ti02 layer was 5 - 10 nm thick and the crystallites were 8 - 10 nm in diameter depends on the type of precursor. A thinner Ti02 coating was found to be beneficial to the suspended photocatalyst whilst the conductivity of the composite was more important to the immobilised composite. It suggested that the CNT content was proportional to the photocurrent level generated and the acid-treated CNTs performed better than raw CNTs. The photocurrent increased significantly with positively increasing the applied potential for all the composites and substrates tested. The electrochemical aspects of the threeelectrode cell were discussed based on the suggested semi-quantitative model for charge transfer across the working electrode. It had shown that the synergetic effect between CNTs and Ti02 were important and strong. These results are valuable for tailoring the CNT/Ti02 or similar nanocomposites to meet specific technological applications in the environmental and renewable energy sectors. I

Investigation of consolidation process by electric discharge sintering (EDS) at the temperatures 1400 – 1550 °C for nanostructured high melting point powders and composition are described in the paper. In the present work we apply EDS technology to consolidate nanocomposites in the system TiN – TiB2, TiN – Si3N4. Influence of green body form and conductivity of the nanopowders on the densification process and mechanical properties of sintered bodies are studied. Sintering experiments were carried out in CO atmosphere When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35079

Dans le contexte actuel d’une demande énergétique croissante associée à un appauvrissement des ressources fossiles, il devient urgent de trouver des sources d’énergies alternatives, écologiquement et économiquement viables. La photocatalyse est une voie prometteuse et innovante pour produire de l’hydrogène (H2) à partir d’énergies renouvelables. Le but est de développer des matériaux stables et efficaces pour amener le procédé à un niveau de maturité suffisant pour de possibles développements à moyen terme.Cette thèse est axée sur l’élaboration et l’optimisation de nouveaux systèmes composites nanostructurés, Au / gC3N4 / TiO2, pour la production d’hydrogène par procédé photocatalytique à partir de l’eau et de l’énergie solaire. L’aspect innovant étant d’optimiser chaque composant de manière à tirer profit des avantages de chacun, puis à surmonter leurs limitations individuelles en les associant de manière intime dans des structure hiérarchisées afin d’obtenir des taux de production d’H2 compétitifs à température ambiante sous illumination solaire et visible. Une étude comparative a également été entreprise sur le photocatalyseur commercial TiO2 P25 « Evonik ® » et met en avant l’efficacité de ces nouveaux matériaux. Pour finir, les activités photocatalytiques de ces composites ont ensuite été corrélées avec leurs propriétés physico-chimiques
Nowadays, energy demand is constantly increasing while fossil ressources are dwindling and has become imperative to find new alternative energy sources. Photocatalysis is a promising and innovative way to produce hydrogen (H2) from renewable energies. The ai mis to develop stable and efficient materials in order to bring the process towards sufficient efficiency for possible mid-term developments. This thesis focuses on the development and optimization of new nanostructured composite systems, Au / gC3N4 / TiO2, for hydrogen produciton by water-splitting. The innovative aspect is to optimize every components in order to take advantages of each and then to intimately associate them in hierarchical structure for obtaining competitive rates of hydrogen production at room temperature under solar and visible illumination. A comparative study was also undertaken on commercial photocatalyst TiO2 P25 « Evonik ® » to highlight the efficiency of these new materials. Finally, photocatalytic activities of these composites were correlated with their physico-chemical properties

碩士
國立中正大學
化學所
94
This study investigated the phase transfer of aqueous Au nanoparticles and Ag nanoparticles into the organic solution by adding different surfactant and ionic liquid and thereafter the preparation of Au@TiO2 and Ag@TiO2 nanocomposite materials.To prepare Au@TiO2 and Ag@TiO2 nanoparticles, metal nanoparticles have to be firstly prepared. Metal nanoparticles are usually produced in aqueous solution, due to the water-soluble nature of metal salt. In addition, synthesis of different sized and shaped nanoparticles in aqueous solutions is easier than that of in organic solutions. However, some applications of metal nanoparticles have to be performed in organic phase. For example, TiO2 coating of metal nanoparticle by hydrolysis-condensation of titanium dioxide，s precursor in water is very fast. Hence, the size and thickness of the Core-Shell composition are very difficult to control in water-based solution, as in contrast with that of in organic solution. This research examined the effect of organic solvent, modifier, precursor and concentration of ionic liquid on the formation of core-shell material. The results indicate that : (1) Ionic liquid can be employed to transfer the nanoparticles from aqueous phase into organic phase and the efficiency of phase transfer is proportion to the concentration of ionic liquid. The data implies that the ionic liquid behaves as an ion-pair reagent in the process of phase transfer. (2) Organic solvent and modifier are definitely required to form a stable core-shell structure. (3) The size of Au@TiO2 and Ag@TiO2 nanocomposite is proportion to the concentration of ionic liquid in organic solution.

碩士
國立臺北科技大學
機電整合研究所
100
Nanomaterials and nanotechnologies have widespread applications in biomedical fields. In this research, we intend to acquire the core-shell nanoparticles with the optical and magnetic properties for those needs. Synthesis of FePt/TiO2 nanocomposite was processed through three stages. First, Chemical reduction method was used to prepared hydrophilic FePt nanoparticles. Then using Sol-gel method to obtain the rutile form of TiO2 nanoparticles at low temperature. Finally, a core-shell nanoparticles of hydrophilic and lipophilic FePt coated with TiO2 crystalline coated was successfully acquired by combining both the chemical reduction method and sol-gel method. Characterizations were determined by using X-ray Diffractometer (XRD)，Transmission Electron Microscopy (TEM)，Fourier transform infrared spectrometer (FTIR)，UV/Vis spectrophotometer (UV/vis)，Vibrating Sample Magnetometer (VSM)，and The high-frequency heater (MFH). The FePt nanoparticles prepared in solvent of tetraethylene glycol, which have -OH，-COO-M and -CO-M signal functional groups, are soluble in organic solvents and aqueous solutions. And the saturation magnetization is 30.69 emu/g. The rutile TiO2 nanoparticles prepared at low temperatures will not have phase transformation at the annealing temperature increased to 800 ℃. Finally, single FePt@TiO2 core-shell nanoparticles were observed under different ratio of TiCl4 precursor which exhibit magnetic properties and reaction to UV wave absorption. This core-shell nanoparticles can be applied to biomedical in the future.

碩士
國立成功大學
物理學系碩博士班
96
In this work, we synthesize nanocomposite under ultra-high vacuum which has high density defects. We observe little change to magnetoresistance（MR）when samples were annealing under ultra high vacuum environment（10-9 torr）. However, apparent change of MR is observed under high vacuum annealing （10-6 torr）. Structure of Co/TiO2 nanocomposite has characterized by XRD and XAS. The change of blocking temperature doesn’t have the corresponding result with MR which indicates that Co particles may not be main reason. Analysis of impedance spectra and temperature-dependent resistivity show that oxide layer have the great influence to the change of MR. In summary, we think that observed magnetoresistance change in different vacuum annealing was attributed to defects.

碩士
國立暨南國際大學
應用材料及光電工程學系
104
Abstract In this study, photocatalytic reduction and ion exchange methods were employed to fabricate the ternary nanocomposite photocatalysts of Ag-TiO2-graphene (ATG) and Ag3PO4-TiO2-graphene oxide (APTGO), respectively. The contents of graphene and Ag in ATG were adjusted, and the molar ratio of Ag3PO4 to TiO2 in APTGO was tuned. The properties and photocatalytic activity of the nanocomposites were examined, and their photodegradation mechanisms were explored. When an ATG had more graphene, light absorption and charge transport were enhanced, leading to higher efficiencies of photodegradation and hydrogen production from water splitting. It was proved that the optimum ratio between TiO2 and graphene was 5:1. More Ag contributed to light absorption and reduced impedance. The surface enhanced Raman scattering (SERS) effect induced by Ag nanoparticles was favorable to photocatalytic activity. However, excess Ag decreased the specific surfacearea of an ATG photocatalyst, and lower light absorption and increased recombination probability were thereby caused. Accordingly, an appropriate content of Ag was required so as to obtain more effective photocatalysis. Moreover, it was found that the optimum Ag content was different for a different mixing ratio between TiO2 and graphene. The best photocatalytic efficiency of ATG (max. hydrogen production 4233 mole g-1 and QE = 26.2 %) was achieved when graphene and Ag both existed optimal contens. More TiO2 in APTGO improved light absorption but caused a larger impedance and inferior charge transport. Excess TiO2 distributed over the surfaces of Ag3PO4 and graphene oxide decreased the specific surface area and thus lower light absorbance of an APTGO photocatalyst. It has been evidenced that an appropriate TiO2 content was beneficial to enhance photocatalytic performance. Larger and wider light absorption and thereby highest photocatalytic efficiency of APTGO (max. hydrogen production 1312 mole g-1 and QE = 8.13 %) were achieved when the molar ratio of Ag3PO4 to TiO2 was 0.6.

碩士
國立雲林科技大學
材料科技研究所
103
Pt/TiO2-graphene nanocomposites used as photocatalyst were prepared by a hydrothermal process using graphene oxide, titanium tetrachloride, and sodium borohydride as precursors of the TiO2/graphene. Then a given amount of hexachloroplatinic acid were added in TiO2/graphene solution and stirred for 20 h. After this, the samples calcined at 500 oC for 1 hr to obtain Pt-doped TiO2-graphene nanocomposites. Compared to undoped TiO2, the absorption edge of Pt/TiO2-graphene composites shifted to 435 nm in visible range with Pt doping TiO2, PtO, PtO2 and graphene incorporation. The prepared Pt/TiO2-graphene nanocomposite catalysts showed enhanced photocatalytic activity than pure TiO2 under visible-light irradiation for AO7 degradation. The higher photocatalytic activity of the nanocomposite catalysts could be attributed to extended light absorption, efficient charge separation, enhanced adsorptivity, and the photoformed electrons can easily produce more OH radicals and superoxide radical anion. Pt/TiO2-graphene nanocomposites exhibits the highest efficiency at the mass ratio of H2PtCl6 :TiCl4 :GO = 10:100:1. 99.11% of AO7 is decomposed under 6 hr visible light irradiation.

碩士
東海大學
物理學系
99
Abstract 　　The goal of this research is that the zinc oxide nanowires will be applied to form the ZnO / TiO2 composites in dye-sensitized solar cells. The main idea is to keep a large surface area of TiO2 nanoparticles for absorption of dye, and reduce the occurrence of the reverse reaction behavior by adding the ZnO nanowires. 　　In experiments, ZnO nanowires are grown by using chemical vapor deposition (CVD). Also, a compact layer of TiO2 is prepared by the sol-gel method between the ZnO nanowires and P-25 TiO2 particles. ZnO nanowires form a protective effect against P-25 slurry acid erosion. In such P25/Sol-gel TiO2/ZnO composite cell, photoelectric conversion efficiency is improved by adjusting the parameters of cell structures. The efficiency measured by AM1.5 solar simulator is 2.86%. 　　To prove the application of ZnO nanowires in dye-sensitized solar cells, P25/Sol-gel TiO2/ZnO and P25/Sol-gel TiO2 are compared in dye-sensitized solar cell behavior. From the open circuit voltage decay (OCVD) measurement, P25/Sol-gel TiO2/ZnO composite battery cell has a better lifetime than single material P25/Sol-gel TiO2. 　　In this experiment, although the efficiency of composite materials P25/Sol-gel TiO2/ZnO cells is not as good as the P25/Sol-gel TiO2 single material cells, composite materials exhibit the inhibition of the reverse reaction, It shows composite structures are in the possible way. The photoelectric conversion efficiency can be enhanced as the dyes suitable for ZnO nano materials are used, or successfully controlled the growth of zinc oxide crystal phase should be improved.

碩士
國立中央大學
化學工程與材料工程研究所
97
The purpose of this research is the preparation of transparent thick film or monolith with high refractive index. Titanium oxide, with a reported refractive index of 2.5 for anatase, can be a suitable inorganic additive in improving the refractive index of organic-inorganic hybrid materials. Epoxy resin, which is in common use of LED’s encapsulation. If titanium oxide and epoxy could be composited into a transparent material, the resulting product would have wide applications. To achieve such hybrid material with high refractive index and good transparency, the particle size of titanium dioxide must be below 10 nm, for otherwise light scattering effect would dominate. 　　For the synthesis of nano-sized titanium dioxide, tetrachloride (TiCl4) was used as a precursor, followed by hydrolysis and condensation reactions. After washed the white titanium hydroxide gel by water, peptization and crystallization took place in acidic condition. Since peptize size is strongly dependent on the solution concentration, pH and peptizing temperature, the first part of this research was finding the optimum experimental parameters to produce the smallest nano particles dispersible in water. 　　To disperse titanium dioxide in organic solvent and resin, surface modification of the particles is pivotal. Two aliphatic amines, for instance, n-hexlamine and dodecylamine were modifying agents used in this study. After surface modification with these agents, titanium dioxide can be dispersed in chloroform. 　　Concurrently, surface modification was done with functional silane, 3-(Trimethoxysilyl) propyl methacrylate (MPS) and 3-Glycidoxypropyl trimethoxysilane(GPS), allowing titanium dioxide to be dispersible in ethylacetate. Having successfully dissolved titanium dioxide, epoxy resin 4221 and EP828 were added. 　　The as-synthesized TiO2/epoxy thick film is formed from MPS&GPS modified TiO2 and then dispersed in ethylacetate/epoxy 4221 mixture. From thermal gravimetric analysis (TGA), the 8 micron thick film contains up to 50 wt% inorganic material (approximately 45 wt% TiO2 estimated). In addition, the refractive index is measured to be up to 1.70, and it has over 96% transmittance at 600nm wavelength. Nonetheless, such tranparent thick film has a very low glass transition temperature (~70oC), resulting in limited applications.

碩士
國立臺灣海洋大學
材料工程研究所
106
TiO2-ZnS core-shell composite nanorods were synthesized by using ZnO as a sacrificial shell layer in a hydrothermal reaction. ZnO thin films of different thicknesses were sputter-deposited onto the surfaces of TiO2nanorods as templates for hydrothermally synthesizing TiO2-ZnS core-shell nanorods. Structural analysis revealed that crystalline TiO2-ZnS composite nanorods were formed without any residual ZnO phase after hydrothermal sulfidation in the composite nanorods. The thickness of the ZnO sacrificial shell layer affected the surface morphology and sulfur-related surface defect density in hydrothermally grown ZnS crystallites of TiO2-ZnS composite nanorods. Due to the distinctively core-shell heterostructure and the heterojunction action between the TiO2 core and the ZnS shell, TiO2-ZnS core-shell nanorods exhibited ethanol gas-sensing performance superior to that of pristine TiO2nanorods. An optimal ZnO sacrificial shell layer thickness of approximately 60 nm was found to enable the synthesis of TiO2-ZnS composite nanorods with satisfactory gas-sensing performance through sulfidation. The results demonstrated that hydrothermally derived TiO2-ZnS core-shell composite nanorods with a sputter-deposited ZnO sacrificial shell layer are promising for applications in gas sensors.

碩士
國立雲林科技大學
材料科技研究所
103
Pt-TiO2/MoS2/graphene nanocomposites used as photocatalyst were prepared by two hydrothermal process using graphene oxide, Na2MoO4 • 2H2O, thiourea, titanium tetrachloride, and sodium borohydride as precursors of the TiO2/MoS2/graphene. Then a given amount of hexachloroplatinic acid were added in TiO2/ MoS2/graphene solution and stirred for 20 h. After this, the samples calcined at 500 oC for 1 hr to obtain Pt-doped TiO2-MoS2-graphene nanocomposites. Compared to undoped TiO2, Synthesis MoS2 can increase effective transfer and separation of photogenerated electrons in graphene incorporation. The prepared Pt-TiO2/MoS2/graphene nanocomposite catalysts showed enhanced photocatalytic activity than pure TiO2 under visible-light irradiation for AO7 degradation. The higher photocatalytic activity of the nanocomposite catalysts could be attributed to extended light absorption, efficient charge separation, enhanced adsorptivity, and the photoformed electrons can easily produce more OH radicals and superoxide radical anion.

碩士
國立中興大學
材料工程學研究所
92
PEN(polyethylene naphthalate) containing naphthalate structure exhibits superior tensile strength, thermal stability and low permeability. Thus they have been widely used as air-bag and recording tapes. However, PEN still has some undesirable properties that limit their application be a flexible substrate of display. In this report, we have used MMT as the dispersed phase to prepare PEN/MMT nanocomposites by melt-direct interaction of PEN into modified layered hosts. TGA, DMA, DSC, XRD, permeability and UV-visible spectrum have been used to analyze the properties of nanocomposite. From TGA and DMA results, they revealed that the heat stability in 1wt% content of PEN/MMT nanocomposite had been clearly increased, but it’s not apparent for 3wt% content of PEN/MMT nanocomposite due to the worse dispersion. These results showed that the physical properties of nanocomposite would be directly revealed to crystalline feature and behavior of PEN. Both X-ray and DSC data reveal polymorphic behavior of PEN, depending on their thermal history. The parameter of crystallization kinetics determined by Avrami and Hoffman-Lauritzen theories were also discussed. Analyses from these theories indicated that PEN’s phase transformed temperature shifted from 240℃ to lower temperature and increased crystallizatin rates while MMT was added. It was inferred that mobility of PEN’s molecular chain which had been hindered by MMT to generates β-form crystals easily, and the increasing crystallizatin rates of PEN/MMT nanocomposite was also influence by MMT. From the measurement of permeability and UV-visible spectrum, PEN/MMT substrates have lower permeability than PEN. The addition of 3wt% MMT content of PEN/MMT was decreased the transparency from 88% to 73%. This result indicates that the dispersion of modified MMT affects the permeability and transparency of nanocomposites directly. Then PEN/MMT nanocomposite had been processed by nitrogen /oxygen plasma to increase the surface roughness of substrates which could be increased the adhesion between the substrate and barrier. Finally, nano-size of TiO2 particles were prepared by sol-gel method followed by thermal treatment and had been investigated by TEM and FESEM. From the TEM observation, and the particle sizes of TiO2 could be determined. The coated TiO2 on the surface of nanocomposite could be observed by FESEM and the addition of TiO2 layers on the surface of PEN/MMT nanocomposite could be further revealed the permeability from 8.35 to 3.91gm/m2‧day.

碩士
國立雲林科技大學
電子工程系
106
In this study, gold nanoparticles is successfully prepared by using photochemical method. AuNPs is modified on ITO and TiO2 film using the self-assembly method with APTES for the self-assembly time of 4 hours, 8 hours, and 12 hours, where APTES is used as a linker molecules. The particles diameter was measured by using transmission electron microscope(TEM). The morphology was measured by using field-emission scanning electron microscope (FE-SEM) and atomic force microscope (AFM). The optical properties and glucose solution are measured by using UV-Visible spectroscopy. The sensing characteristics of the biosensor have been analyzed for the sensitivity, linearity and electrochemical properties by using Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS) measurement systems. The result shows AuNPs/TiO2 nanocomposite film had a good optical properties. When AuNPs is modified on TiO2 films, the photcatalytic activity of TiO2 can enhance optical properties. In optical properties measurement, LSPR sensor based on AuNPs/TiO2 nanocomposite film with a self-assembly time of 12 hours have good sensitivity and linearity for detecting the environment of different refractive indices are 58.4 nm and 0.995, respectively. After detecting glucose solution, the results show a good sensitivity of 0.44 nm/mM and a limit of detection of 3.47 mg/dl (0.197 mM). In electrical properties measurement, the nafion is applied as an immobilization material due to the high chemical stability and biocompatibility. The enzyme composite solution was dropped on the AuNPs /ITO electrodes and AuNPs/TiO2/ITO electrodes to form glucose biosensor. The glucose biosensor of Nafion/GOx-AuNPs/ITO electrode has a good sensitivity is 8.674 μA/mM．cm2, a good linearity of 0.946, and a limit of detection of 7.3 mg/dl (0.394mM) , which are better than the previous results in our group. The sensitivity, linearity, and limit of detection for the glucose biosensor of Nafion/GOx-AuNPs/TiO2/ITO electrode are 3.438 μA/mM．cm2 , 0.945, and 17.7 mg/dl(0.956mM), respectively. In the interference measurement, the different interferences are detected by using Nafion/GOx-AuNPs-APTES/ITO electrode. The interference effects for 0.1 mM ascorbic acid, 0.4mM uric acid, and 0.2 mM acetaminophen are 2.6 %, 4.9 %, 0.3 % , respectively.

碩士
高雄師範大學
化學系
97
Abstract This research is to develop a novel organic/inorganic nanocomposite material as a heat resistant, transparent, and anti-static thin film with sol-gel method. Firstly, the coupling agent 3-(acryloxypropyl)trimethoxysilane, APTMS, is taken to hydrolysis using diluted acid to perform the silanol intermediate. The silanol intermediate can successfully modify the surface of colloid titanium dioxide or powder titanium dioxide for linking to organic matrixes. Next, using the remained active Si-OH functional groups, which are on the APTMS/colloid TiO2 or APTMS/powder TiO2 complexes, to dehydrolysis condensation with the SR-399 acrylate monomer. So the SR-399/APTMS/TiO2 nanocomposites will be successfully prepared. Finally, in order to improve the mechanical and thermal resistant properties, APTMS, SR-399 and DVB monomers will be chain copolymerized by UV-curing to form a perfectly cross-linking structure of orgaic/inorganic nanocomposites. The experimental results show that the best formula weight contents of SR-399/DVB/APTMS/colloid TiO2 and SR-399/DVB/APTMS/powder TiO2 are 1.00/0.50/0.60/0.20~0.30 and 1.00/0.50/ 0.60/0.33 ~0.52. The surface resistanes of SR-399/DVB/APTMS/colloid TiO2 (19.23% colloid TiO2) and SR-399/DVB/APTMS/powder TiO2 (8.70% powder TiO2) hybrid thin films are decreased from 1.13×1013Ω/ cm2 to 2.09×1010 Ω/ cm2 and 6.45×1010Ω/ cm2 respectively. When we add inorganic filler, TiO¬2, and coupling agent, APTMS, the thermal stability of these nanocomposites will be improved. According to the best formula weight contents, the Td values of SR-399/DVB/APTMS/colloid TiO2 and SR-399/DVB/APTMS/powder TiO2 nanocomposites are 481.67~485.16℃and 478.18 ~480.39℃ respectively, higher than that of SR-399/DVB copolymer about 26.74℃ and 19.94℃. The glass transition temperature is not detected below 200℃ by DSC. The excellent optical transparency upon 90% is achieved in the visible region. By using XRD to determine the bondings between SR-399/DVB organic matrixes and APTMS/TiO2 inorganic complexes are chemical cross-linking bondings, and not existing inorganic crystalline structure. According to the morphology structure which is estimated by SEM, the optic thin films are evenly distributed with inorganic colloid TiO2 or powder TiO2, the average particle size of these composites is 53~58 nm.

碩士
臺灣大學
化學研究所
98
Protein phosphorylation is an important post-translational control of protein activity in cells. However, low abundances, low stoichiometry, and poor ionization of phosphopeptides make the isolation and concentration steps indispensable prior to MS analysis. In this study, we utilized a new probe of high affinity for phosphopeptide enrichment with titanium dioxide-coated nanodiamonds (TiO2-coated NDs). Nanodiamond (ND) holds several unique properties such as small particle size, large specific surface area, wide optical transparency range, and facile surface functionalizability, making it a promising solid-phase substrate for affinity purification mass spectrometry. The enrichment conditions were optimized using tryptic digests of β-casein, and the high specificity of the TiO2-coateed NDs was demonstrated by selectively enriching phosphopeptides from the tryptic digests of protein mixture of β-casein and bovine serum albumin (BSA) with a molar ratio of 1: 5000, followed by MALDI-TOF MS characterization. The new protocol was also coupled with nano-LC-MS/MS system without difficulty. Analysis of tryptic digests from cytoplasmic fraction of HeLa cells yielded numbers of phosphopeptide identifications comparable to that obtained using commercial phosphopeptide isolation tool (Phos-trapTM 96 Enrichment Kit) and almost 59.3% recovery of phosphopeptides, presumable due to the presence of a large numbers of sites available on TiO2-coated NDs for binding or incomplete removal of nonspecific bound peptides. In 120 μg of equivalent of HeLa cell lysates, we identified 696 unique phosphopeptides and 925 phosphorylation sites, indicating the excellent performance of the TiO2-coated NDs.

碩士
國立臺灣大學
材料科學與工程學研究所
102
In this thesis, we reported the preparation, the microstructures and the optical properties of poly(3-hexylthiophene)/TiO2 nanocomposites based on aldehyde end-functionalized P3HT (P3HT-CHO) and amphiphilic P3HT block copolymer, poly(3-hexylthiophene-block-hydroxylated isoprene) (P3HT-b-PIOH). Pristine unmodified P3HT were also used for reference studies. Two methods were employed to prepare the Nanocomposites: (1) solution blending of polymers and commercial available TiO2 nanoparticles, Degussa P25 (~21 nm); (2) in-situ sol gel process of TiO2 precursors in polymer solution. The attractive interaction between aldehyde of P3HT-CHO and hydroxyl group of TiO2 allowed smaller aggregations of TiO2 (~ 50 - 200 nm) blending.The in-situ sol gel processes using chlorotitanium triisopropoxide (ClTIP) would further enhance the homogeneity in TiO2 dispersion despite of enlarged particle sizes (~ 50 -200 nm) as the aldehyde group of P3HT-CHO would react with ClTIP to form covalent bonds to anchor P3HT in the surface of TiO2. Thus preventing the aggregation of TiO2. Since the in-situ sol gel process avoid the use of dispersants and ligands of TiO2 nanoparticles, the photoluminescence quenching of P3HT-CHO/ClTIP composites could be further improved comparing to P3HT-CHO/P25. The use of amphiphilic P3HT-b-PIOH block copolymer remarkably afforded the resulting P3HT-b-PIOH/ClTIP composites having uniformed TiO2 nanoparticles (~ 30 nm) homogenously dispersed in the polymer matrix, which could be attributed the increasing number of covalent linkages between the hydroxyl groups of PIOH and ClTIP. The optical properties were derived from the UV-vis spectroscopy. Even the loading of TiO2 was up to 30 wt%, the maximum absorption peak was not blue-shifted and the π-π stacking of P3HT retain for P3HT-CHO/ClTIP and P3HT-b-PIOH/ClTIP composites

博士
國立雲林科技大學
工程科技研究所
106
In typical dye-sensitized solar cells (DSSCs), a porous nanocrystalline TiO2 photoanode plays the important role for mass dye-loading and electrons transport. However, the power conversion efficiency of DSSCs is limited by that the charge recombination during the electron transport in the porous nanocrystalline TiO2 photoanode and partial light harvesting from incident light. Therefore, we propose the ZnO nanorods arrays/TiO2 nanoparticles (ZnO NRs/TiO2 NPs) and deformed TiO2 aggregates/Au nanoparticles (DTA/AuNPs) composite films as the photoanode, according to the good electron affinity of ZnO NRs, the high specific surface area, light scattering of DTA and the Schottky barrier effect of plasmonic AuNPs. In this study, the features of ZnO NRs/TiO2 NPs and DTA/AuNPs composite films have been demonstrated by using scanning electron microscope (SEM), transmission electron microscope (TEM), x-ray diffractometer (XRD), UV-Visible spectrophotometer, and specific surface area/pore size distribution analyzer. The photovoltaic performances and electrochemical impedances of DSSCs with ZnO NRs/TiO2 NPs and DTA/AuNPs photoanodes are also investigated by using the solar cell measurement system with a solar simulator and the electrochemical impedances spectroscopy. The photovoltaic performances of DSSCs with ZnO NRs/TiO2 NPs photoanode annealed at 550˚C has the best fill-factor of 44 and power conversion efficiency of 0.19%. The DSSCs with DTA/AuNPs based photoanode exhibit a high Jsc of 7.58 mA/cm2, a Voc of 0.78V, a fill-factor of 59.31 and a power conversion efficiency of 3.06%, which suggests that the enhancement of short-circuit current density and power conversion efficiency would be contributed by sufficient specific surface area for dye loading and the long electron lifetime in the photoanode film.

碩士
國立臺灣大學
高分子科學與工程學研究所
96
Along with the evolution of technology, the fabrication of the organic-inorganic nano composite was developed by blending the nano-sized particles and the polymers. Nanocomposites had many advantages such as high refractive index, low thermal expansion coefficient, good thermal stability, and excellent mechanical properties. The high refractive index materials can be widely used as encapsulants , optical waveguides and optical lenses, etc. In this research, crystalline TiO2 nanoparticles with an average size smaller than 30nm were successfully synthesized via sol-gel process. After surface modification, the TiO2 nanoparticles were stabilized and well dispersed in organic solvents to form transparent TiO2 nanoparticle colloidal solutions. Through the UV-vis spectra, we studied how the surfactants influenced the optical properties of surface modified TiO2 in solution state. Then, the surface modified TiO2 nanoparticle solutions were mixed with epoxy resin to fabricate organic-inorganic hybrid materials with high refractive index and high transparency. Differential scanning calorimetry(DSC) was used to investigate the cure kinetics of the composite. We found that the activation energy (Ea) determined in accordance to Kissinger’s method, the peak temperature of exotherm (Tp), and the heat of curing(∆H) decreased with increasing concentration of surface modified TiO2. The refractive index of cured nanocomposite films was in the range of 1.54–1.73 at 633nm, which linearly increased with the content of TiO2 nanoparticles from 0 to 40 wt %. The transmittance of the cured nanocomposite was higher than 90% because the well dispersion of surface modied TiO2 in the polymer matrix, which avoid the effect of light scattering caused by particle aggregation. Differential scanning calorimetry (DSC), thermomechanical analysis (TMA), thermogravimetric analysis (TGA) and microhardness tests were applied to characterize the cured nanocomposite materials.