Dissertations / Theses on the topic 'Photocatalytic nanocomposites'

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.

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.

This thesis consists of two research problems in the water decontamination area. In the first work, the main focus is to understand the structure and photocatalytic activity of titanium dioxide with graphene (G-TiO2) which is synthesized by using sol-gel method. The photocatalytic activity of TiO2 is limited by the short electron hole pair recombination time. Graphene, with high specific surface area and unique electronic properties, can be used as a good support for TiO2 to enhance the photocatalytic activity. The obtained G-TiO2 photocatalysts has been characterized by X-Ray Diffraction (XRD), Raman Spectroscopy, Transmission Electron Microscopy (TEM), FTIR Spectroscopy and Ultraviolet visible (UV-vis) Spectroscopy. This prepared G-TiO2 nanocomposite exhibited excellent photocatalysis degradation on methyl orange (MO) under irradiation of simulated sunlight. Such enthralling photocatalyst may find substantial applications in various fields. The primary objective of the second work is to understand the nanocomposite structure of SiO2 coated over graphene (G) nanoplatelets. An attempt has been made to synthesize G-SiO2 nanocomposite using sol-gel technique. The G-SiO2 nanocomposite is characterized using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Raman spectroscopy, FTIR spectroscopy, and Electrochemical and Electrical measurement technique, respectively. In this work, G-SiO2 nanoparticles with the water containing salts of zinc is added, and allowed to settle in water. The ZnCl2 ix concentration displays a whitish color solution which has turned to colorless within one or two hours of treatment with G-SiO2 nanocomposites. The presence of heavy metal is tested using electrochemical cyclic voltammetry (CV) technique. The CV measurement on the water treated with G-SiO2 has been tested for several days to understand the presence of heavy metals in water. Interestingly, the near complete separation has been observed by treating the heavy metal contaminated water sample for one to two days in presence of G-SiO2 nanoparticles. The redox potential observed for the heavy metal has been found to diminish as a function of treatment with respect to time, and no redox peak is observed after the treatment for four to five days. Further test using EDS measurement indicates that the heavy metal ions are observed within the G-SiO2 nanocomposite. The recovery of G-SiO2 nanocomposite is obtained by washing using deionized water. Our experimental finding indicates that the G-SiO2 nanocomposite could be exploited for potential heavy metals cleaning from waste or drinking water.

Environmental pollution on a global scale is expected to be the greatest problem that chemical scientists will face in the 21st century, and an increasing number of these scientists are looking to new photocatalytic systems for the solution. Existing photocatalytic systems are effective for the decomposition of many unwanted organics through the use of efficient semiconductor photocatalysts activated by ultra-violet (UV) irradiation. The demand for visible light activated photocatalytic systems is increasing rapidly. Currently, however, the efficiency and availability of photocatalysts which can be activated effectively by the solar spectrum and especially indoor lighting is severely limited. The purpose of this project is to investigate the potential of a TiO2-ZnFe2O4 alloyed nanocomposite for use as a visible light activated photocatalyst. An overview of the principles of photocatalysis is first provided. Relevant properties of pure and modified TiO2 are next discussed, and results of studies on structural and photocatalytic properties are presented. Alloyed TiO2-ZnFe2O4 nanocomposites are discussed in detail and their crystal structure, particle size, particle interaction, optical characteristics, and photoactivity are discussed in detail. Measurements characterizing the alloys are carried out using XRD, SEM, EDS, UV-Vis spectroscopy, and photodegradation procedures. The photoactivity of the alloys is carefully studied through phenol degradation experiments, and recommendations are provided to improve the photocatalysts under investigation.

Hydrogen fuel is one of the most important areas of research in the field of renewable energy development and production. Hydrogen gas can be generated by fuel cells, water electrolyzers, and heterogeneous nanoscale catalysts. It can be burned to directly release chemical energy or condensed for storage and transport, providing fuel for combustion devices or storing excess energy generated by renewable sources such as wind turbines and concentrated solar power assemblies. While platinum is the most active catalyst for hydrogen reduction, its high cost significantly deters its utilization in advanced photocatalytic materials. One approach to mitigating this expense is optimizing the morphology and placement of nanostructured platinum catalysts. Highly crystalline, morphologically-controlled platinum nanoparticles (Pt NPs) have been effectively utilized to increase hydrogen generation efficiency in a variety of nanocomposite materials. However, synthesis routes to high-quality Pt NPs can be dangerous and difficult to replicate. Furthermore, utilization of the Pt NPs in nanocomposite materials is hindered by lack of control over catalyst placement. Nanopeapods are versatile nanocomposites that offer a high degree of control over catalyst placement as well as the potential for interesting new properties arising from the interaction between the catalyst and a semiconductor. Platinum@hexaniobate nanopeapods (Pt@HNB NPPs) consist of linear arrays of Pt NPs encapsulated within the scrolled semiconductor hexaniobate. Pt@HNB NPPs offer significant advantages over similar composites by utilizing the isolated reduction environment of the encapsulated Pt NP arrays to decrease kinetic competition and surface crowding. This work describes the design, fabrication, and implementation of the new nanocomposite platinum@hexaniobate nanopeapods for sensitized hydrogen production under visible light irradiation. The following chapters present facile microwave heating syntheses of highly crystalline Pt nanocubes and Pt@HNB NPPs with consistent morphology and high catalyst loading. A detailed study is also presented of the optical properties of the Pt nanocubes, which produced a UV-range absorbance band that indicates the formation of a localized surface plasmon resonance. Most significantly, preliminary results from visible light photolysis indicate that sensitized Pt@HNB NPPs produce hydrogen in quantities comparable to published systems, and that alteration of experimental parameters may result in even greater yields.

Magister Scientiae - MSc (Chemistry)<br>Drinking water with high concentrations of inorganic and organic contaminants can cause adverse health defects. Specifically methyl orange dye is an organic water contaminant that has been known (along with others like methyl blue etc.) to have an increase in our water systems over the past few years due to increasing demand in industrial processes. It is therefore of utmost importance to remediate organic contaminants and ultimately enable prevention. The contaminants can be removed by photocatalysis. Anatase TiO2 is known for its photocatalytic degradation of environmental pollutants and photoelectro-chemical conversion of solar energy. However its application is limited since it is a wide band gap semiconductor, (Eg = 3.2 eV). The following study deals with the enhancement of the photocatalytic properties of TiO2 for remediation of organic water contaminants. The study was carried out to produce the two nanocomposites AgFe-TiO2 and AgFe-TiO2-rGO photocatalyst which purpose is to be cheap and easy to apply, with improved (fast and effective) photocatalytic degradation of methyl orange. The main objective was to decrease the band gap and to introduce intra-band gap states to absorb visible light. Modification of the TiO2 with small bandgap semiconductor, graphene and Ag- Fe nanoalloy reduced the bandgap energy for visible light absorption and photocatalytic degradation of methyl orange dye. The two composites were synthesised using sonication and chemical synthesis methods. A photocatalytic study (degradation of methyl orange dye) was carried out using a system incorporating an UV lamp source to determine the degradation of methyl orange catalysed by the synthesised photocatalysts AgFe-TiO2-rGO and AgFe-TiO2 along with UV-vis Spectroscopy. Morphological studies were carried out using HRSEM and HRTEM which determined the spherical agglomerated nature of AgFe-TiO2 and the sheet-like nature of AgFe-TiO2-rGO containing spherical agglomerants but that also contained pockets formed by the sheets of the rGO. XRD served as confirmation of the phase of TiO2 in both composites to be anatase. Analysis confirmed the formation and elemental determination of both composites. It was observed that the Band gap of TiO2 degussa decreased from 2.94 eV to 2.77 eV in the composite AgFe-TiO2. The photocatalytic reactivity of AgFe- TiO2 was an improvement from TiO2 and AgFe-TiO2-rGO based on the photocatalytic study. Therefore concluding that AgFe-TiO2 was the best catalyst to convert the dye (Orange II) into free radicals and ultimately remove the contaminant from the water compared to AgFe-TiO2-rGO.

The development of future electronics depends on the availability of suitable functional materials. Printed electronics, for example, relies on access to highly conductive, inexpensive and printable materials, while strong light absorption and low carrier recombination rates are demanded in photocatalysis industry. Despite all efforts to develop new materials, it still remains a challenge to have all the desirable aspects in a single material. One possible route towards novel functional materials, with improved and unprecedented physical properties, is to form composites of different selected materials. In this work, we report on hydrothermal growth and characterization of graphene/zinc oxide (GR/ZnO) nanocomposites, suited for electronics and photocatalysis application. For conductive purposes, highly Al-doped ZnO nanorods grown on graphene nanoplates (GNPs) prevent the GNPs from agglomerating and promote conductive paths between the GNPs. The effect of the ZnO nanorod morphology and GR dispersity on the nanocomposite conductivity and GR/ZnO nanorod bonding strength were investigated by conductivity measurements and optical spectroscopy. The inspected samples show that growth in high pH solutions promotes a better graphene dispersity, higher doping and enhanced bonding between the GNPs and the ZnO nanorods. Growth in low pH solutions yield samples characterized by a higher conductivity and a reduced number of surface defects. In addition, different GR/ZnO nanocomposites, decorated with plasmonic silver iodide (AgI) nanoparticles, were synthesized and analyzed for solar-driven photocatalysis. The addition of Ag/AgI generates a strong surface plasmon resonance effect involving metallic Ag0, which redshifts the optical absorption maximum into the visible light region enhancing the photocatalytic performance under solar irradiation. A wide range of characterization techniques including, electron microscopy, photoelectron spectroscopy and x-ray diffraction confirm a successful formation of photocatalysts. Our findings show that the novel proposed GR-based nanocomposites can lead to further development of efficient photocatalyst materials with applications in removal of organic pollutants, or for fabrication of large volumes of inexpensive porous conjugated GR-semiconductor composites.

Magister Scientiae - MSc (Chemistry)<br>Drinking water with high concentrations of inorganic and organic contaminants can cause adverse health defects. Specifically methyl orange dye is an organic water contaminant that has been known (along with others like methyl blue etc.) to have an increase in our water systems over the past few years due to increasing demand in industrial processes. It is therefore of utmost importance to remediate organic contaminants and ultimately enable prevention. The contaminants can be removed by photocatalysis. Anatase TiO2 is known for its photocatalytic degradation of environmental pollutants and photoelectro-chemical conversion of solar energy. However its application is limited since it is a wide band gap semiconductor, (Eg = 3.2 eV). The following study deals with the enhancement of the photocatalytic properties of TiO2 for remediation of organic water contaminants.<br>2021-12-31

>Magister Scientiae - MSc<br>The global lack of clean water for human sanitation and other purposes has become an emerging dilemma for human beings. The presence of organic pollutants in wastewater produced by textile industries, leather manufacturing and chemical industries is an alarming matter for a safe environment and human health. For the last decades, conventional methods have been applied for the purification of water but due to industrialization these methods fall short. Advanced oxidation processes and their reliable application in degradation of many contaminants have been reported as a potential method to reduce and/or alleviate this problem. Lately, it has been assumed that incorporation of some metal nanoparticles such as magnetite nanoparticles as photocatalyst for Fenton reaction could improve the degradation efficiency of contaminants. Core/shell nanoparticles, are extensively studied because of their wide applications in the biomedical, drug delivery, electronics fields and water treatment. The current study is centred on the synthesis of silver-doped Fe₃O₄/SiO₂/TiO₂ photocatalyst. Magnetically separable Fe₃O₄/SiO₂/TiO₂ composite with core–shell structure were synthesized by the deposition of uniform anatase TiO₂ NPs on Fe₃O₄/SiO₂ by using titanium butoxide (TBOT) as titanium source. Then, the silver is doped on TiO₂ layer by hydrothermal method. Integration of magnetic nanoparticles was suggested to avoid the post separation difficulties associated with the powder form of the TiO₂ catalyst, increase of the surface area and adsorption properties. Lastly and most importantly magnetic nanoparticles upsurge the production of hydroxyl groups or reduced charge recombination. The a synthesized catalysts were characterized using Transmission Electron Microscopy, X-ray Diffraction; Infra-red Spectroscopy, Scanning Electron Microscope and Energy Dispersive Spectroscopy. Other characterization techniques includeVibrating Sample Magnetometry, Brunauer Emmett Teller analysis and Thermogravimetric analysis. The average size of the particles size is 72 nm. Furthermore the photocatalytic performances of the magnetic catalysts were assessed in comparison with that commercial titanium dioxide for the degradation of methylene blue using photochemical reactor under ultra violet light. The results showed that the photocatalytic activity was enhanced using Fe₃O₄/SiO₂/TiO₂ and Ag-Fe₃O₄/SiO₂/TiO₂ compared with that for Fe₃O₄, commercial titanium dioxide powder.

Thesis (MScEng)--Stellenbosch University, 2013.<br>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.<br>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.

La recherche actuelle est entreprise dans l'optique de la révision complète du design chimique et des principes d'élaboration des photocatalyseurs composites supportés (PCCS) afin d'améliorer considérablement leurs capacités réactionnelles, la durabilité de leur action en temps et de résoudre le problème de pollution secondaire des milieux à traiter. Les travaux effectués ont permis la mise en œuvre d'un nouveau modèle de PCCS interactifs dont les composants photosensibles sont en fortes interactions chimiques avec leurs supports appartenant au groupe d'acides de Lewis. Cette particularité assure une grande sélectivité d'action des produits développés, leur fonctionnement durable en régime stationnaire, évite la pollution secondaire des effluents à traiter et garanti une performance photocatalytique comparable à celle du produit de référence Degussa P25.Les travaux réalisés ont permis d'acquérir de nouvelles connaissances scientifiques concernant le rôle de l'acidité de surface dans l'action photocatalytique et du taux de dissociation de l'eau adsorbée sur le produit actif. De plus, un ensemble de huit paramètres principaux assurant les meilleures conditions d'exploitation des PCCS a été établi.Les PCCS développés peuvent être appliqués, tout d'abord, dans le domaine de l'incinération photocatalytique des COV. Un prototype de filtre dynamique capable de traiter 50 m3/h de l'air avec une consommation d'énergie modérée, est conçu. Un nouveau type de matériaux composites à vocation germicide à base de polymères synthétiques fait également l'objet de la partie applicative de ces travaux de thèse.

Ce mémoire porte sur la synthèse de matériaux composites nanostructurés à base de polyoxométallates pour la conversion de l’énergie et des applications à des problèmes environnementaux. Pour atteindre ces objectifs, de nombreux composés nouveaux de cette famille d’oxydes moléculaires ont été synthétisés puis ont été associés à différentes matrices éco-compatibles dans le respect des principaux critères de la Chimie Verte. Les principales techniques d’étude sont l’électrochimie, la photochimie et la spectroscopie UV-visible. Dans le domaine de l’énergie, les catalyseurs obtenus se sont révélés très efficaces dans des réactions très importantes mais difficiles à réaliser, comme la production de l’hydrogène, la réduction de l’oxygène et l’oxydation de l’eau. De même, parmi les applications aux problèmes de dépollution, ces nanomatériaux ont montré une forte activité électrocatalytique et photocatalytique pour la réduction des oxydes d’azote, des bromates et la photodégradation d’un colorant textile toxique, l’Acide Orange 7. Les performances de ces nouveaux catalyseurs sont comparables à celles des meilleurs systèmes connus<br>This thesis focuses on the synthesis of nanostructured composite materials based on polyoxometalates for energy conversion and applications to environmental problems. To achieve these goals, many new compounds of this family of molecular oxides were synthesized and were associated with different nature friendly matrices, in agreement with the main criteria of Green Chemistry. In the field of energy, the new catalysts have proved very effective in important but difficult to achieve reactions, such as producing hydrogen, oxygen reduction or water oxidation. Similarly, among applications to pollution problems, these nanomaterials have shown a strong electrocatalytic and photocatalytic activity for the reduction of nitrogen oxides, bromate and for the photodegradation of a toxic textile dye, Acid Orange 7. The performances of these new catalysts are comparable to those of the best known systems

The potentially most important challenges today are related to energy and the environment. New materials and methods are needed in order to, in a sustainable way, convert and store energy, reduce pollution, and clean the air and water from contaminations. In this, nanomaterials and nanocomposites play a key role, and hence knowledge about the relation between synthesis, structure, and properties of nanosystems is paramount. This thesis demonstrates that solution-chemical synthesis, using amine-modified acetates and nitrates, can be used to prepare widely different nanostructured films. By adjusting the synthesis parameters, metals, oxides, and metal–oxide or oxide–oxide nanocomposites were prepared for two systems based on Co and Zn:Fe, respectively, and the films were characterised using diffraction, spectroscopy, and microscopy techniques, and SQUID magnetometry. A variety of crystalline cobalt films—Co metal, CoO, Co3O4, and composites with different metal:oxide ratios—were synthesised. Heat-treatment parameters and control of the film thickness enabled tuning of the phase ratios. Random and layered Co–CoO composites were prepared by utilising different heating rates and gas flow rates together with a morphology effect associated with the furnace tube. The Co–CoO films exhibited exchange bias due to the ferromagnetic–antiferromagnetic interaction between the Co and CoO, whereas variations in e.g. coercivity and exchange bias field were attributed to differences in the structure and phase distribution. Ordered structures of wurtzite ZnO surrounded by amorphous ZnxFeyO were prepared through controlled phase segregation during the heating, which after multiple coating and heating cycles yielded ZnO–ZnxFeyO superlattices. The amorphous ZnxFeyO was a prerequisite for superlattice formation, and it profoundly affected the ZnO phase, inhibiting grain growth and texture, already from 1% Fe. In addition, ZnO–ZnxFeyO exhibited a photocatalytic activity for the oxidation of water that was higher than results reported for pure ZnO, and comparable to recent results reported for graphene-modified ZnO.

Les Chalcogénures métalliques ont émergé comme une classe importante de matériaux en raison de leur grand potentiel dans de nombreuses applications technologiques. Dans cette thèse, des approches faciles et peu onéreuses ont été adoptées pour développer des nanomatériaux de chalcogénures métalliques et des films minces à partir de leurs précurseurs, les complexes organo-métalliques. L’utilisation des nanomatériaux synthétisés et des couches minces dans les cellules solaires et dans la purification photocatalytique de l’eau a été discutée. La première approche adoptée implique la synthèse de nanomatériaux de sulfure métallique à partir du complexe metal-thiourée (M-TU) comme précurseur. Des nanocristaux (NCs) de sulfure de plomb (PbS) ainsi que des nanostructures ont été synthétisés à partir des complexes méthanoliques plomb-thiourée (Pb-TU) via diverses techniques de précipitation basées sur la décomposition du complexe méthanolique Pb-TU. Nous avons aussi synthétisé des nanostructures de sulfure de cadmium (CdS) par décomposition hydrothermale et solvothermale du précurseur du complexe cadmium-thiourée mélangé à l’ACA. Les nanostructures de CdS telles que synthétisées ont montré des activités photocatalytiques très efficaces pour la dégradation du méthylorange et de la rhodamine B (RhB) en milieu aqueux. On a aussi développé des voies simples de synthèse pour préparer des nanomatériaux d’halogénure métallique à partir des complexes (M-O). La sulfurisation des précurseurs du complexe M-O à une température relativement basse produit des nanocristaux de sulfure métallique très stable vu que l'acide oléique (OA) est chimisorbé en tant que carboxylate à la surface des NCs. Le précurseur du complexe oléate de cadmium Cd-O a aussi été utilisé pour préparer des NCs de CdSe. Le traitement de surface des NCs de CdSe ainsi synthétisés avec de la pyridine et du tert-butylamine a été très efficace pour remplacer les ligands AO à longues chaines. Les cellules solaires à hétérojonction volumique fabriquées à partir des NCs de CdSe à surface traitée montrent une meilleure amélioration dans les performances photovoltaiques par rapport aux NCs de CdSe non traités. La décomposition solvothérmale du précurseur du complexe Cd-O mélangé à la thio-urée produit aussi des nanocristaux composés de microsphères de CdS en forme de chou-fleur ayant de bonnes propriétés physicochimiques et une capacité photocatalytique à dégrader le RhB en milieu aqueux. La technique de déposition de revêtement par centrifugation ‘spin coating’ a été utilisée pour fabriquer les films minces de CdS et de PbS à partir de leurs précurseurs, les complexes méthanoliques M-TU. Les films obtenus avaient une surface lisse et affichaient des bandes interdites à taille quantifiée. Les raisons possibles de la faible efficacité des dispositifs de cellules solaires à films minces de CdS/PbS ont été discutées.<br>Metal chalcogenides have emerged as an important class of materials due to their potential significance in many technological applications. In this work, easy and low cost approaches have been developed to prepare metal chalcogenide nanomaterials and thin films from their metal-organic complex precursors. The use of synthesized nanomaterials and thin films in solar cells and photocatalytic water purification has been discussed. The first approach adopted involves the synthesis of metal sulphide nanomaterials using metal-thiourea (M-TU) complex precursors. Lead sulphide (PbS) nanocrystals (NCs) and nanostructures were synthesized from methanolic lead-thiourea (Pb-TU) complex via various precipitation techniques based on the decomposition of methanolic Pb-TU complex. We have also synthesized cadmium sulphide (CdS) nanostructures through hydrothermal and solvothermal treatment of aminocaproic acid (ACA)-mixed cadmium-thiourea complex precursor. The as-synthesized CdS nanostructures were found to exhibit highly efficient photocatalytic activities for the degradation of methyl orange and rhodamine B (RhB) in aqueous medium. We have also developed simple synthetic routes to prepare metal chalcogenide nanomaterials from metal-oleate (M-O) complexes. Sulphurizations of M-O complex precursors at relatively low temperatures produced highly stable metal sulphide NCs because oleic acid (OA) is chemisorbed as a carboxylate onto the surface of NCs. The cadmium-oleate (Cd-O) complex precursor was also used to prepare CdSe NCs. Surface treatments of the as-synthesized CdSe NCs with pyridine and tert-butylamine were very effective to replace long chain OA ligands. Bulk-heterojunction solar cells made from surface treated cadmium selenide (CdSe) NCs showed greater improvement in photovoltaic performances compared to those made from untreated CdSe NCs. Solvothermal decomposition of thiourea-mixed Cd-O complex precursor also produced nanocrystals composed of cauliflower-like CdS microspheres with good physicochemical properties and photocatalytic ability to degrade RhB in aqueous medium. The spin-coating deposition technique was used to develop PbS and CdS thin films from their methanolic M-TU complex precursors. The obtained films had smooth surface and showed size quantized band gaps. The possible reasons behind the low efficiency of CdS/PbS thin film solar cell device were also discussed.

Made available in DSpace on 2014-12-17T14:07:15Z (GMT). No. of bitstreams: 1 MaraTST_DISSERT.pdf: 2071273 bytes, checksum: 9636b6602dd1a469f78b17d077ba757f (MD5) Previous issue date: 2013-03-04<br>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<br>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

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<br>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

Orientador: Leinig Antônio Perazolli<br>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)<br>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)<br>Doutor

Orientador: Dayse Iara dos Santos<br>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)<br>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)<br>Doutor

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.<br>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.

Ce travail de thèse a pour objectif la création d’indice optique local et contrôlé dans une matrice vitreuse à travers la mise au point et le développement de procédés de synthèse de nanoparticules (NPs) de sulfure de zinc (ZnS) dans un verre d’oxydes. Nous avons commencé par l’élaboration par voie de fusion d’un verre d’oxydes de composition initiale très simple. Nous avons ensuite examiné la problématique de la synthèse et du contrôle de croissance des NPs de ZnS dans nos échantillons dans trois matrices différentes et par trois traitements : recuit thermique, insolation UV ou par un traitement simultané (recuit thermique + insolation UV). Les propriétés optiques des verres dopés NPs ZnS fabriqués ont été caractérisées par diverses techniques (absorption UV visible, photoluminescence, FTIR, Raman, XPS, mesure d’indice). Il ressort de ces caractérisations que nous arrivons à fabriquer des NPs dans les trois matrices dont la taille peut aller de 1.8 à 7 nm. La dispersion sur les distributions de taille dépend de la matrice, du traitement post-fusion et de sa durée ainsi que de la concentration initiale en dopant. Nous avons également été amené à synthétiser et à étudier des nanopoudres de ZnS. Le procédé de sélection de taille révèle qu’il est possible d’obtenir au moins trois distributions étroites de tailles bien distinctes. Des filtres optiques UV à bande étroite peuvent ainsi être réalisés pour une longueur choisie en contrôlant la taille des NPs ZnS. Des applications prospectives des NPs ZnS pour le nano marquage et la photo dégradation de polluants modèles présents dans l’eau ont été illustrées<br>Our efforts have been devoted to the development of simple approach to synthesize ZnS nanoparticules (NPs) by melting process in a glassy matrix with the aim to create a controlled optical index variation. In this thesis, we present the formation of ZnS NPs in the glassy matrix and study of their optical properties. The nanocomposite incorporating ZnS in the host medium was prepared using the melting process from a mixture of the raw materials. We have prepared various glass samples with ZnS NPs size ranging from 1.8 à 7 nm. These samples were treated (heat treatment ± UV insulation with 244 nm laser) and characterized by UV-Vis absorption, FTIR, photoluminescence spectroscopy, Raman measurements and XPS. The refractive index measurements of these nanostructured composite glasses have been carried out and show an important increase with ZnS concentrations and treatments. We also present the elaboration of small and monodisperse ZnS nanopowder with size ranging from 3 to 100 nm by a simple, low-cost and mass production chemical method. The NPs were characterised by X-ray powder diffraction (XRD), UV-vis absorption and photoluminescence spectroscopy. The photocatalytic activity of ZnS nanopowders was investigated by using different colorant water dispersed. ZnS NPs appear to be a good candidate for potential environmental applications such as water purification. We also present application of fluorescent ZnS nanoparticles as cellular biomarkers. Fluorescent microscopy images of osteoblastic MC3T3-E1 cells revealed that the ZnS nanoparticles were biocompatible and were penetrated cells and nucleus regardless of their size. Hence, the ZnS NPs can be good candidates for drug delivery and bio-imaging applications

Am Beispiel von ferroelektrischen Systemen auf Bismut-Basis (Bismutmolybdat, Bismutwolframat und Bismuttitanat) und von Strontiumbariumniobat werden neue Möglichkeiten zur Synthese solcher Nanopartikel aufgezeigt. Die Integration der Nanopartikel in transparente Nanokompositmaterialien und die Entwicklung neuer Precursoren für die Herstellung von Dünnschichtproben gehen den Untersuchungen zur Anwendung als elektrooptische aktive Materialien voraus. Durch weitere Anwendungsmöglichkeiten in der Photokatalyse, dem Test dampfadsorptiver Eigenschaften mit Hilfe eines neuartigen Adsorptionstesters (Infrasorb) und auch mit Hilfe der Ergebnisse der ferroelektrischen Charakterisierung von gesinterten Probenkörpern aus einem Spark-Plasma-Prozess wird ein gesamtheitlicher Überblick über die vielfältigen Aspekte in der Arbeit mit nanoskaligen, ferroelektrischen Materialien gegeben.

碩士<br>逢甲大學<br>材料科學與工程學系<br>106<br>There are two subjects in this thesis, which are the synthesis and applications of molybdenum disulfide / zinc oxide nano-heterostructures and molybdenum disulfide / tin dioxide nano-heterostructures, respectively. First, this present study has been used a facile hydrothermal method to grow MoS2 nanostructures. The different morphologies of MoS2/ZnO nano-heterostructures were synthesized by a wet chemical growth method under the different weight of MoS2 nanostructures. The photocatalytic activities of MoS2/ZnO nano-heterostructures were evaluated in the photocatalytic degradation of methylene blue under visible light irradiation. The MoS2/ZnO nano-heterostructures revealed much higher photodegradation efficiency than commercial ZnO and TiO2 nanopowders. In addition, appropriate reaction condition of MoS2/ZnO nano-heterostructures were also exhibited the better hydrogen production rate under visible light irradiation. The novel MoS2/ZnO nano-heterostructures will offer promising applications, such as solar energy conversion and energy storage. Second, MoS2/SnO2 nano-heterostructures have been synthesized by two-step hydrothermal processes. The different weights of citric acid play an important role to control the morphology of MoS2/SnO2 nano-heterostructures. The photocatalytic activities of MoS2/SnO2 nano-heterostructures were evaluated in the photocatalytic degradation of rhodamine B under visible light irradiation. The MoS2/SnO2 nano-heterostructures revealed much higher photodegradation efficiency than commercial ZnO and TiO2 nanopowders. In addition, appropriate reaction condition of MoS2/SnO2 nano-heterostructures were also exhibited the better hydrogen production rate under visible light irradiation. The novel MoS2/SnO2 nano-heterostructures provide a facile, low cost, high recyclability, and high enhancement in visible light photocatalytic properties, which may be advantageous for the practical applications in environmental remediation and energy conversion.

Thesis (Ph. D.)--University of Notre Dame, 2004.<br>Thesis directed by Eduardo E. Wolf and Prashant V. Kamat for the Department of Chemical Engineering. "April 2004." Includes bibliographical references (leaves 196-216).

Tese de Doutoramento em Ciências (Especialidade em Física)<br>Photocatalysis has obtained considerable attention, and a variety of materials have been applied in different areas, in particular in the environmental field. Photocatalysis consists of the use of radiation (UV or sunlight) to generate highly oxidizing species, which will destroy environmental contaminants into innocuous compounds. Catalysts are required to this process, and due to its significant oxidizing properties under UV irradiation, superhydrophilicity, chemical stability in a broad pH range, low-cost, and extended durability, titanium dioxide (TiO2) are one of the most used photocatalysts with increasing interest for environmental applications. Despite the advantages of TiO2 as a photocatalyst, there are still two main issues concerning the use of TiO2 nanoparticles for practical applications. First, the reusability of TiO2 nanoparticles is time-consuming and requires expensive separation/filtering processes. Second, the reduced spectral activation of TiO2 that has a wide band gap (3.2 eV, for anatase), being only activated by UV radiation (< 387 nm). The proposed work will address those relevant issues. In this way, TiO2 nanoparticles were immobilized into a poly(vinylidenefluoridetrifluoroethylene) (P(VDF-TrFE)) membrane, and the comparative study of their photocatalytic performance with dispersed TiO2 nanoparticles was performed. The membrane shows a highly porous structure (≈75 %) with controlled wettability, achieved by the inclusion of zeolites (NaY). These properties are critical to achieving a methylene blue degradation efficiency of 96 % in 40 min under ultraviolet (UV) irradiation, corresponding to an efficiency loss of just 3 % regarding the corresponding suspended TiO2 nanoparticles assay. The same nanocomposite was also tested in the degradation of tartrazine in a solar photoreactor, and the results show that the TiO2/PVDF-TrFE nanocomposite exhibits a remarkable sunlight photocatalytic activity, with 78% of tartrazine being degraded. The same polymer matrix was used to immobilize TiO2 nanoparticles doped with erbium (Er) and codoped with erbium and praseodymium (Pr), produced by a microwave-assisted technique. The results reveal that the low band gap (2.63 eV) and high surface area of these TiO2 modified nanoparticles, coupled with the highly porous structure of the membrane, synergistically envisages the best photocatalytic performance by degrading 98 % of methylene blue after 100 min exposed to UV radiation. To enhance the photocatalytic activity of TiO2 both under UV and visible radiation, an Au/TiO2 nanocomposite was produced, characterized and applied to the degradation of ciprofloxacin (CIP). A homogeneous distribution of Au nanoparticles over the TiO2 nanoparticles surface has been achieved, with an effective band gap of 2.84 eV for the nanocomposite. These results allowed to foresee the enhanced degradation of CIP, 13 and 145 % under UV and simulated visible light radiation, respectively. The gold nanoislands play a critical role, working as electron receptor and endowing the nanocomposite with the ability to absorb the visible radiation. Additionally, the separation of the electron-hole pair, and the surface plasmon of resonance can promote the photocatalytic efficiency of the nanocomposite In the same scope, a TiO2/G and TiO2/GO nanocomposites were produced to reduce the electron-hole pair recombination and enhance the photocatalytic activity under visible radiation. Computational models indicate potentially improved photocatalytic activity due to lower band gaps and charge carrier segregation at the interfaces. Regarding methylene blue degradation, show that TiO2/G and TiO2/GO nanocomposites were more efficient than pure TiO2 under UV light. In contrast, the same nanocomposites were less efficient than pristine TiO2 in ciprofloxacin degradation. These nanocomposites were also immobilized in electrospun fiber mats, and the results show that even 3% wt. % of TiO2/GO in the fibers yields excellent photocatalytic performance by degrading ≈100% of MB after 90 min of visible light exposure. A new hybrid photocatalytic material was produced to address polluted water in sites deprived of light (e.g., deep water and turbid water). TiO2 nanoparticles immobilized in a poly(vinylidene difluoride) matrix were coated onto polymeric optical fibers. The photocatalytic efficiency tests revealed that the 50 w/w % of TiO2 P25 in the coating lead to a degradation of 95 % of ciprofloxacin after 72 hours under artificial sunlight and that reusability of 3 times led to a loss of activity lower than 11 %. Thus, the present work shows a set of different approaches that tackle the main issues related to photocatalysis. Different photocatalytic materials were produced, characterized and applied. Similarly, to improve reusability of the photocatalyst, different support materials (PVDF and PVDF-TrFE) were used as well as different morphologies (membrane, fiber membrane, and coating). All the produced photocatalysts show enhanced activity when compared to pristine TiO2 and all the immobilized systems have also displayed an efficient functional performance and suitable reusability.<br>A fotocatálise tem atraído muitas atenções, e nesse sentido, muitos materiais têm sido aplicados em diversas áreas, em particular no ambiente. A fotocatálise consiste na utilização da radiação (ultravioleta ou solar) para produzir espécies oxidativas, que serão responsáveis pela destruição dos contaminantes aquáticos, originando compostos inofensivos. Os catalisadores são necessários para este processo e devido as suas propriedades oxidativas sob irradiação UV, superhidrofilicidade, estabilidade química a diferentes gamas de pH, baixo custo e elevada durabilidade, o dióxido de titânio (TiO2) é um dos fotocatalisadores mais utilizados em aplicações ambientais. Apesar das vantagens do TiO2 como fotocatalisador, existem alguns problemas associados à sua utilização prática. A reutilização destas nanopartículas é morosa e que requer processos de separação/filtração dispendiosos. Além disso, outra limitação é a reduzida ativação espectral do TiO2, que possui um elevado band gap e por isso é ativado apenas por radiação UV (<387 nm). O trabalho aqui apresentado foca-se no desenvolvimento de materiais alternativos capazes de superar estes problemas. Neste sentido, as nanopartículas de TiO2 foram imobilizadas numa membrana de poli(fluoreto de vinilideno) trifluoretileno (PVDF-TrFE), e testada a sua performance fotocatalíticas, comparando-a com as nanopartículas em suspensão. Estas membranas possuem uma estrutura porosa (≈75 %) e a molhabilidade foi controlada pela incorporação de zeólitos (NaY). Estas propriedades foram fundamentais para obter uma degradação de 96% de azul de metilenos sob radiação UV durante 40 min. Correspondendo a uma perda de apenas 3% de eficiência relativamente ao ensaio com TiO2 em suspensão. O mesmo nanocompósito foi também testado na degradação de tartrazina, num fotoreactor solar, e os resultados mostraram que após 5 horas de irradiação, ≈ 78% da tartrazina foi degradada. A mesma matriz polimérica foi utilizada para imobilizar nanopartículas de TiO2 dopadas com erbium (Er) e co-dopadas com Er e prasiodímio (Pr) produzidas pelo método de micro-ondas. Os resultados mostram que o band gap (2.63eV) mais baixo e a elevada área de superfície das nanopartículas de TiO2, juntamente com a elevada porosidade da membrana, contribuíram para a melhor eficiência fotocatalítica, degradando 98 % de azul de metileno após 100 min de exposição a radiação UV. Para melhorar a atividade fotocatalítica do TiO2, foi produzido, caracterizado e aplicado o nanocompósito de Au/TiO2 na degradação de ciprofloxacina (CIP). A caracterização revelou uma distribuição homogénea de nanopartículas de Au na superfície das nanopartículas de TiO2, bem como um band gap efetivo de 2.84 eV. O nanocompósito revelou um aumento na degradação da CIP, cerca de 13 e 145 % em UV e radiação visível, respetivamente. As nanoilhas de ouro funcionam como recetores de eletrões, dotando o nanocompósito da capacidade de absorver radiação visível. Além disso, a separação do par eletrão-lacuna, bem como a ressonância de plasmão de superfície podem promover maior eficiência fotocatalítica do nanocompósito. Adicionalmente, nanocompósitos de grafeno (TiO2/G) e óxido de grafeno (TiO2/GO) foram produzidos para também reduzir a recombinação do par eletrão-lacuna e aumentar a atividade fotocatalítica usando radiação visível. Os modelos computacionais indicaram um potencial aumento da atividade fotocatlítica com base no menor band gap e na presença de transportadores de carga nas interfaces. Os resultados experimentais mostram que os nanocompósitos de TiO2/G e TiO2/GO foram mais eficientes que TiO2 puro na deagradação de azul ed metileno sob radiação UV. Os mesmos nanocompósitos foram menos eficientes na degradação da CIP do que o TiO2 puro. Os nanocompósitos TiO2/GO foram ainda imobilizados em membrana de fibras de PVDF-TrFE produzidas por electrospinning, e os resultados mostram que com apenas 3 wt. % TiO2/GO, este compósito degradou ≈100% do AM após 90 min de exposição a radiação visível. Um novo material hibrido foi também produzido, de forma a possibilitar o tratamento de aguas contaminadas em locais desprovidos de radiação (e.g., aguas profundas e aguas turvas). Nanopartículas de TiO2 foram imobilizadas numa matriz de poli(fluoreto de vinilideno) (PVDF) para revestimento de fibras óticas poliméricas. Os testes fotocatalícos mostraram que foi possível degradar 95% da CIP após 72 horas de radiação visível, e que após 3 reutilizações a perda de eficiência foi de apenas 11%. Em resumo, o presente trabalho apresenta uma série de abordagens focadas na resolução das principais limitações da fotocatálise – aumento da atividade no visível e reutilização. Similarmente, para aumentar a reutilização do fotocatalisador, diferentes substratos foram usados (PVDF e PVDF-TrFE) bem como diferentes morfologias (membranas, membranas de fibras, e revestimento). Todos os fotocatalisadores produzidos possuem maior atividade fotocatalítica do que o TiO2 puro. Por outro lado, os sistemas de imobilização também demonstraram uma eficaz performance e possibilidade de serem reutilizados.<br>Foundation for Science and Technology (FCT) (grant: SFRH/BD/98616/2013) for the financial support of this project.

碩士<br>逢甲大學<br>材料科學與工程學系<br>107<br>Abstract This present study has been used a facile hydrothermal method to grow zinc indium sulfide nanosheets. The zinc indium sulfide and zinc oxide nanocomposites with the different weight of zinc indium sulfide nanosheets were not only controlled the surface-to-volume ratio, but also influenced their optical property. The photocatalytic activities of zinc indium sulfide and zinc oxide nanocomposites were evaluated in the photocatalytic degradation of 4-Aminobenzoic acid under the blue and white light LED irradiation. The zinc indium sulfide and zinc oxide nanocomposites revealed much higher photodegradation efficiency than zinc indium sulfide nanosheets. In addition, zinc indium sulfide and zinc oxide nanocomposites exhibited the better hydrogen production rate under the blue and white light LED irradiation. The novel zinc indium sulfide and zinc oxide nanocomposites will offer promising applications, such as solar energy conversion and energy storage.

碩士<br>國立臺灣師範大學<br>化學系<br>101<br>In this work, we demonstrated a new photocatalyst consisting of FeS2 NCs and TiO2 (Degussa P25) nanomaterials for water splitting reaction. For fabricating the photocatalyst of FeS2-TiO2 nanocomposites, first, FeS2 NCs was successfully prepared by solution process and then mixed with TiO2 under sonication reaction. To enhance interface connection between FeS2 and TiO2, a sulfurization process is obtained. For testing hydrogen generation reaction, a 400W mercury arc lamp was used as a light source to trigger the photocatalytic reaction. We found that the catalysts of FeS2-TiO2 (1:1) in the MeOH/H2O (1:1) solution at pH 7, has highest hydrogen production rate of 373 mole h-1 g-1, which is 20 folds of pristine P25 photocatalyst. In this study, we demonstrated that a FeS2-TiO2 nanocomposites catalysts, which is abundant on earth, environment friendly, and economy, achieved an effectively hydrogen production for water splitting because of extending absorbing visible light in comparison with pure TiO2.

碩士<br>國立中興大學<br>環境工程學系所<br>98<br>Carbon nanotube/titanium dioxide(CNT/TiO2) nanocomposites were prepared by the sol-gel method and CNTs were oxidized by NaOCl solution before prepared the nanocomposites. TiO2 nanoparticles were chemically absorbed at CNTs defect sites via an ester-type linkage (esterification) between carboxylic acid groups of the oxidized CNTs surfaces and the hydroxyl groups at the surface of the TiO2 nanoparticles. CNT/TiO2 can enhance the photocatalytic activity of benzene, toluene, ethylbenzene and xylene (BTEX) photodegradation in an aqueous solution since CNTs will increase the specific surface area(reactive sites) and reduce the rate of electron/hole pairs recombination. The conversion and rate constant of BTEX photodegradation for CNT/TiO2 had optimal conditions at 1.0 g/L, 10%CNT contents, and 400oC calcinations temperature, respectively, which were much higher than TiO2 and Degussa P25. The reaction obeys pseudo-first-order kinetics. The removal efficiency for BTEX were less than 19.6% from the background experiment, which including photolysis and dark reaction. This means that major mechanism in the whole photoreaction process was photocatalytic degradation. At the influence of aqueous parameters on the rate constant of BTEX photodegradation increased with solution pH and the H2O2 dosage at low concentration, but appeared no remarkable change with solution ionic strength. A comparative study of the effect of initial BTEX concentration on the reaction rate showed that the rate constant decreased with increased the initial concentration of BTEX under the same conditions. This suggests that CNTs exhibit a synergistic effect and can increase the efficiency of electron transfer from TiO2 to CNTs in enhancing the photocatalytic activity. Thus, this study showed the potential use of CNT/TiO2 nanocomposite in degradation of BTEX from wastewater.

Heterojunctions were generated between tungsten trioxide and tetraphenyl porphyrin with reduced graphene oxide or exfoliated graphite support for mineralisation of acid blue 25 dye under visible light radiation. Moreover, degradation of pharmaceuticals was conducted using p-n heterojunctions between WO3 and Co3O4 and a direct Z-scheme heterojunction between BiOI and Co3O4 prepared using in-situ method and solvothermal self-assembly method respectively. The synthesized materials were characterised using Raman, FTIR, SEM/EDS, TEM, XRD, TGA, BET, UV-Vis and PL techniques. UV-Vis, TOC and HPLC-QTOF-MS were used to study the degradation efficiency and pathway. Scavenger trapping experiments were conducted to propose the charge transfer mechanisms. The highest degradation efficiency (99 %) was achieved for the dye and the pharmaceuticals using visible light. The mineralisation ability of the fabricated nanomaterials was pH dependent with acidic conditions favouring the removal of the dye (pH 5) while alkaline conditions favoured the mineralisation of pharmaceuticals (pH 10 – 11).<br>Civil and Chemical Engineering

碩士<br>國立中興大學<br>環境工程學系所<br>98<br>CNT/TiO2 nanocomposites were prepared by atmospheric pressure plasma enhanced chemical vapor deposition (APPENS) to study photo-degradation of Acetone vapor. With different plasma voltages of 12, 13 and 15 kV, the rate constants of Acetone degradation are 0.86, 0.60 and 0.42 (min-1 g-1), respectively. It’s shown that a decrease in the voltage results in an increase of the rate constant. The X-ray analysis shows that the TiO2 on CNTs surface is anatase, and in further comparison with the scanning electron micrographs reveals nanoparticle size ranging from 18 to 25 nm. Use of 12kV plasma voltage can obtain smaller particles, so the rate constant is better. Preparing different CNTs content, 0, 10, 20, 30%-CNT/TiO2, the 10%-CNT/TiO2 rate constant reached 1.20min-1 g-1. Compare to the P25 and the sol-gel method composite, the rate constant is higher than in both cases by 2 and 1.5 times. This indicates that CNTs can promote the removal efficiency significantly. For the temperature effect results, the photo-degradation rate constant increases with temperature. And for the continuously experiment, which have same trend with the bath experiment via temperature and relative humidity.

碩士<br>國立雲林科技大學<br>材料科技研究所<br>102<br>In this study, we synthesized ZnSe/graphene composites by a hydrothermal process. First we used zinc sulfate (ZnSO4• 7H2O) and sodium selenite (Na2SeO3) as precursors, diethylenetriamine (DETA) and hydrazine (N2H4) as reducing agents to prepare ZnSe (DETA)-N2H4. In addition, graphene oxide (GO) and ZnSe (DETA)-N2H4 mixed together as precursors, ZnSe/graphene composites were prepared at 180℃ for 12 hours by a hydrothermal process. To explore different amount of hydrazine (4~8ml) and different graphene oxide with zinc selenide proportion (0.25 to 2：1) of ZnSe/graphene composites for photocatalytic degradation dye methylene blue (MB) performance. The results showed that the ZnSe/graphene composites with high photocatalytic activity than ZnSe, which is mainly due to the graphene with excellent electron transport properties and good absorption characteristics. ZnSe under visible irradiation for 6 hours, due to the hydrazine will result in poor degradation, the degradation efficiency was only 35.4%. The ZnSe/graphene which synthesized by graphene oxide and ZnSe(DETA)-N2H4 in a weight ratio 1: 1 can obtain the optimum degradation efficiency was 99.6%.

碩士<br>國立交通大學<br>應用化學研究所<br>98<br>Titanium oxides are common photocatalytic materials due to its chemical stability, low cost, and non toxicity. However, the photocatalytic efficiency is still improvable due to fast charge recombination and inability to utilize visible light. Noble metals have been reported to be very effective for enhancement of TiO2 photocatalysis. Thus in this study, we prepared the TiO2/Ag and TiO2/Au nanocomposites to study the photocatalytic properties. We have synthesized sodium titanate nanotubes from commercial RDH TiO2 powders in a sodium hydroxide solution, followed by proton exchange of sodium titanate nanotubes in dilute acid to form titanic acid nanotubes. After annealing, the titanic acid nanotubes have been converted into photoactive anatase TiO2 nanowires. Therefore, during the fabrication of anatase TiO2, we can obtain the intermediate compounds of sodium titanate nanotubes and titanic acid nanotubes. We have prepared TiO2/Ag nanocomposites by depositing Ag nanoparticles on the support materials such as sodium titanate nanotubes, titanic acid nanotubes and anatase TiO2 nanowires. The surface charge and the surface area of the support materials would affect the Ag nanoparticle sizes and Ag loading. TiO2/Au nanocomposites were prepared by using anatase TiO2 nanowires as the support material. The Au loading and the particle size of Au increased with HAuCl4 concentration. In addition, photocatalytic properties of TiO2/Ag and TiO2/Au nanocomposites were examined by the photodegradation of methylene blue and photoelectrochemical water splitting. The size and loading of the metal particles would affect the photocatalytic properties of the nanocomposites.

碩士<br>國立臺南大學<br>材料科學系碩士班<br>107<br>In recent years, due to the excessive consumption of petroleum, coal and other fossil fuels, carbon dioxide concentration in the global has increased year by year. Therefore, effectively reducing the concentration of carbon dioxide in the atmosphere has become an energy issue. The photocatalytic reduction method uses the endless source of the sun as the energy source, to reduce carbon dioxide (CO2). This study mainly uses CsPbBr3 as the main material of lead-halide perovskite. CsPbBr3 is a semiconductor material with an energy gap of 2.35 ev. It has low manufacturing cost, adjustable energy gap and long carrier life time, but its carrier is easy to recombination. In order to make efficient use of these carriers, they are combined with graphene oxide (GO) and few layers of graphene(FLG) by ligand-assisted reprecipitation (LARP) method. GO and FLG act as carriers for capturing pairs of electron and holes when CsPbBr3 is illuminated. X-ray diffraction (XRD) was used to identify the crystal structure of the material, and the morphology of the material was observed by transmission electron microscopy (TEM). Through Time-resolved PL spectra (TRPL) to explore the carrier dynamics of the interface, carrier separation property. The effect and the energy band structure of ultraviolet photoelectron spectroscopy (UPS) were discussed. Finally, the photocatalytic reduction of CO2 was applied to investigate the correlation between the interface carriers and the band structure for photocatalysis. Comparing samples CsPbBr3: 4.17 umol/hr, CsPbBr3-GO-1.5: 5.57 umol/hr, CsPbBr3-GO-1.5 showed the photocatalytic effect by 1.33 times, and the addition of GO effectively separated the CsPbBr3 carrier. The CsPbBr3-GO and CsPbBr3-FLG nanocomposite structures are used for photocatalysis, which provides a useful research direction in the field of photoelectric conversion.

碩士<br>國立成功大學<br>化學系碩博士班<br>93<br>In this study, Mo-TiO2 and La-TiO2 nanocomposites were prepared by pulsed laser ablation with different laser power. The nanoparticles were investigated by UV-VIS absorption spectroscopy、X-ray diffreation and photoluminescence spectroscopy. At the same time, methylene blue was utilized as a model compound for the decomposition under the visible light. The experiments demonstrated that the methylene blue in aqueous solution can be raised photodegraded more efficieienty under both of La-TiO2 and Mo-TiO2.

碩士<br>國立成功大學<br>材料科學及工程學系<br>104<br>The application of renewable energy has become a global issue in recent years. Semiconductor photocatalyst can effectively decompose organic pollutants and split water to harvest hydrogen fuels by solar light. However, researchers keep exploring the novel materials to overcome nature limitations of materials. In order to efficiently obtain an optimal photocatalyst, a combinatorial composition spread sample was fabricated to facilitate the exploration of appropriate parameters. In this study, density gradient rutile TiO2 was grown on silicon substrate by spin coating and hydrothermal method. Moreover, coupling with density gradient of reduced graphene oxide (rGO) to become a combinatorial density gradient of TiO2-rGO nanorod composites. This novel concept is different from the literature of hydrothermal method which only can produce single parameter on one sample and repeat multiple procedures to explore the best condition. On the contrary, our combinatorial density gradient of TiO2-rGO nanorod composites sample contains a wide range of compositions in a single sample, enabling efficient screening of materials for applications. Various techniques of XRD, SEM, FTIR, Raman, and PL were employed to determine the various characteristics, including phases, morphologies, microstructures, optical properties, compositions, and chemical bondings. Photodegradation activities were determined by decomposing methylene blue (MB) under UV light. The result shows that coupling with suitable amount of rGO can effectively assist TiO2 to enhance the photocatalytic properties. In photoelectrochemical (PEC) reaction, the cell was measured with a constant 1 V bias under UV light. The measured current of TiO2-rGO nanorod composites was approximately 25 μA/cm2 more than double the value obtained from the pure TiO2 nanorods (approximately 10 μA/cm2).

碩士<br>國立臺灣師範大學<br>化學系<br>101<br>One of the major needs for the 21st century is the development of alternative energy sources to fossil fuels that do not contribute to greenhouse gas emissions. Hydrogen has considerable potential as an alternative fuel because it is carbon-free, facilitates use of more efficient power generation systems. Using a single precious metal electrode and an ECPB to generate hydrogen and oxygen from water would allow much more economically-viable large-scale generation of hydrogen than is currently possible. The primary steps of natural photo-synthesis involve the absorption of sunlight and its conversion into spatially separated electron-hole pairs. The photocatalyst uses a photon to excite an electron from the valence band to the conduction band: resulting in an excited state, and the energy difference between the valence band and conduction band is known as the “band gap”. This must correspond to the wavelength of light for it to be effectively absorbed by the photocatalyst. After photoexcitation , the excited electrons and holes separate and migrate to the surface of photocatalyst .The two protons, which are needed to generate hydrogen gas. The hole in the valence band can be filled with an electron produced by the oxygen generation, in the photocatalytic water-splitting reaction, they act as reducing agent and oxidizing agent to produce H2 and O2 respectively. Efficient charge separation are fundamentally important for photocatalytic hydrogen generation through water splitting. So we can via avoiding charge recombination by adding sacrificial agent to improve hydrogen generate efficiency. Cu2S has been widely used in solar cell devices and identified as p-type semiconducting materials because of the copper vacancies within the lattice. Cu2S is both an indirect and direct band gap materials, with Egbulk≈ 1.2eV and 1.8eV, respectively. In order to absorb light, it is necessary to narrow the band gap. The conduction band is fairly close to the reference potential for H2 formation, there are few reports on the photocatalytic H2 production. Nickel hydroxide (Ni(OH)2) has received increasing attention since it is a very important cathode material in a number of alkaline rechargeable batteries . Because of the stability in strong alkaline electrolyte and excellent reversibility when charged to NiOOH, it’s also reported the enhanced photocatalytic H2-production efficiency. The enhanced mechanism is because thepotential of Ni2+/Ni (Ni2+ + 2e- → Ni, Eo = -0.23 V) is slightly lower than conduction band (CB) (-0.25 V) of Cu2S, meanwhile higher than the reduction potential of H+/H2 (2H+ + 2e- →H2, Eo = -0.00 V), which favors the electron transfer from CB of Cu2S to Ni(OH)2 and the reduction of partial Ni2+ to Ni. The function of Ni is to help the charge separation and to act as cocatalyst for water reduction, thus enhancing the photocatalytic H2-production activity. Its higher efficiency and lower cost than noble metal can be applications of co-catalyst with another semiconductor material.

碩士<br>元智大學<br>化學工程與材料科學學系<br>96<br>The main objectives of the present study were to prepare surface-modified zero-valent iron nanoparticles for the remediation of nitrate and nitrite in wastewater. The experimental part contains the synthesis of the material, identification and application to treat with nitrate and nitrite wastewater. Prepare surface-modified zero-valent iron nanoparticles by coating polyethyleneimine (PEI) and titania nanofilms. Coating titania part, Titanium isopropoxide (TTIP) and Tetrabutyl orthotitanate (TBOT) were used as the precursors to synthesize titania/zero-valent iron nanocomposites. Characterization of PEI/Fe(0) and TiO2/Fe(0) reacted with nitrate and nitrite wastewater were also investigated by precision instrument. In addition, this study was also carried out to provide information concerning the removal efficiencies and mechanism in the chemical reductive treatment processes for nitrate and nitrite wastewaters. By FE-SEM and TEM analyses, spherical zero-valent iron nanoparticles have a diameter around 80~100 nm. In addition, zero-valent iron nanoparticles coated with PEI in the form of spherical particles with diameter around 20-30 nm were also measured by FE-SEM and TEM microphotos. PEI/Fe(0) has a characteristic peak of Fe(0) at 2θ = 44.59o and 64.62o identified by XRD patterns and surface area of 53.4 m2/g measured by BET isotherms was also investigated. From ESCA spectra, the main species on PEI/Fe(0) surface were Fe3O4 and α-FeOOH. Using TTIP as the precursor to synthesize TiO2/Fe(0) nanocomposites, after calcined at 500oC for 2 h, the single phase of TiO2/Fe(0) nanocomposites became armophous to anatase. By TEM and FE-SEM analyses, TiO2 coating was enwrapped on the zero-valent iron nanoparticles, forming core-shell structure of TiO2/Fe(0) nanocomposites, after calcined at 500oC for 2 h, the TiO2 shell becomes relatively loose and possesses aperture structure with diameter around 20-30 nm. TiO2/Fe(0) nanocomposites has a characteristic peak of anatase TiO2 at 2θ = 25.7o identified by XRD patterns and surface area of 84.8 m2/g was measured by BET isotherms. By using X-ray absorption near edge structure (XANES), the valence and framework of TiO2/Fe(0) are similar with Ti(IV) structures. The EXAFS data revealed that TiO2/Fe(0) had a first shell of Ti-O bonding with bond distances of 1.94 Å and coordination numbers was 3.40. Using TBOT as the precursor to synthesize anatase TiO2/Fe(0) nanocomposites and without heat treatment. By TEM and SEM analyses, the core Fe(0) with diameter around 50 nm and the anatase TiO2 shell relatively loose and possesses aperture structure. TiO2/Fe(0) nanocomposites has characteristic peak of anatase TiO2 and Fe(0) at 2θ = 25.24o、37.82°、48.04° and 2θ = 25.42°、37.82°、48.04° identified by XRD patterns, respectively. Surface-modified zero-valent iron nanoparticles reaction with nitrate and nitrite solution of 60 mg/L as N. The concentrations of the nitrate and nitrite solution were decreased obviously. After 30 min, the nitrate and nitrite removal efficiency were 50 and 70%, respectively. After 3 h, the nitrate and nitrite removal efficiency reached 100%. TiO2/Fe(0) nanocomposites reaction with nitrate and nitrite solution of 60 mg/L as N. After 3 h, the nitrate and nitrite removal efficiency were only 40 and 23%, respectively. According to the mass balance of nitrogenous species during the reactions for the surface-modified zero-valent iron nanoparticles, around 70% nitrate and nitrite were converted to ammonia. It appeared that some of the nitrate and nitrite was converted to nitrogen gas.

碩士<br>元智大學<br>化學工程學系<br>93<br>ABSTRACT A core-shell structured composite, nanophase titania coated Ni-, or Zn-ferrites nanoparticles, not only reserve the characteristics and advantages of TiO2 but also have the strong ferromagnetism of the ferrites. Therefore, the main purpose of the research was to synthesize nickel or zinc ferrites with spinel structure. In addition, it focused on the magnetic characteristics of the surface-modified Zn or Ni-ferrite nanoparticles, which was expected to prepare a magnetically separable TiO2 photocatalyst. Experimentally, firstly nickel or zinc ferrite core nanoparticles were synthesized under hydrothermal conditions (pH = 8.5, T = 453 K, and mixing rate of 1250 rpm) by precipitating from metal nitrates with aqueous ammonia. Synthesized nanopowders were characterized by field-emission scanning microscopy (FE-SEM), X-ray powder diffractometer (XRPD), and transmission electron microscopy (TEM). The results showed that the pore sizes of nickel or zinc ferrite catalysts were about 50 nm with spinel structure. The decomposition of nitrate or nitrite solutions analyzed by gas chromatograph (GC) was investigated with oxygen-deficient nickel or zinc ferrite catalysts formed by hydrogen reduction at 573 K and 1 atm. The removal efficiencies of 2000, 1000, and 500 mg/L for nitrate and nitrite were about 9, 10, and 20% per gram ferrite nanopowder, respectively. TiO2 coated on the surface of the nickel or zinc ferrites were then prepared by hydrolysis of titanium chloride in the presence of ferrite nanoparticles. The optimal synthesis conditions included pH values of 8~9 and sintering at 773 K. The obtained samples were characterized by XRD, FE-SEM, and TEM techniques. The results indicated that the nanoshell of TiO2 with anatase structure was about 20 nm. This research also performed the photocatalytic degradation of phenol solution using UV light by TiO2 coated ferrites nanoparticles and measured by ion chromatograph (IC). It represented that the removal efficiencies of phenol were about 36% under 500 mg/L and 83.6% under 50 mg/L, respectively. The TiO2/ferrite nanocomposites were separated by a strong magnet. The percentages of TiO2 coated nickel ferrite recovery was about 98%. X-ray absorption near edge structure (XANES) or extended X-ray absorption fine structure (EXAFS) was performed to identify the fine structures and oxidation state of Ni- or Zn-ferrites and anatase-typed TiO2 coated ferrites nanoparticles. By using XANES spectra, Ni- or Zn-ferrites may exhibit an absorbance feature for the 1s to 3d transition can reveal the occupation of tetrahedral sites within the lattice, it showed that Ni ferrite had the same reverse spinel structure with Fe3O4 and the valence of hydrogenated ferrites were between 2 and 3. In addition, by using resonant inelastic X-ray scattering (RIXS) technique, the fine valent of Zn or Ni-ferrites approaching 2.9 may be further investigated. When the sintered temperature arrive 723 K, the nanosell of TiO2 would transform from amorphous to anatase, and the nanoshell of TiO2 photocatalysts were all Ti (IV). The EXAFS data revealed that the nanoshell TiO2 photocatalyst had first, second shell of Ti-O, and third shell of Ti-Ti with bond distances of 1.96 ± 0.01, 2.01 ± 0.01, and 3.05 ± 0.01 Å, respectively.

碩士<br>國立臺灣海洋大學<br>生命科學暨生物科技學系<br>105<br>We report a one-pot morphology-controlled synthesis of TiOx decorated gold nanocomposite (TiOx–Au NCs) using HAuCl4 and titanium trichloride (TiCl3) as precursors, and catechin as reducing agent. Gold nanoparticles (Au NPs) synthesized by the reduction of Au3+ ions by catechin polymer in the absence of TiCl3 had distorted spherical shape with a thick layer of catechin polymer coating on the nanoparticle. However, Au NPs synthesized in presence of TiCl3 in the reaction mixture obtained a range of morphologies from spherical to urchin-like shape as the concentration of TiCl3 increased in the reaction mixture. Interestingly, only very thin layers of TiO2 and poly(catechin) were coated on Au NPs to form TiOx–Au NCs. The obtained TiOx–Au NCs were characterized by transmission electron microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy, and X-ray diffraction. The photocatalytic activity of TiOx–Au NCs was examined for the photocatalytic degradation of different dyes, such as methylene blue (MB), rhodamine B (Rh B), and malachite green (MG) under white light from xenon lamp. The degradation of the dyes by TiOx–Au NCs as photocatalyst for an irradiation time of 60 min was >99%. The TiOx–Au NCs exhibited excellent antibacterial activity against Escherichia coli (E. coli) and MRSA. It showed almost complete death of bacterial cells after 80 min. or light exposure from a Xenon arc lamp. The urchin-shaped TiOx–Au NCs exhibited such high photocatalytic efficiency due to the its large number of gold spikes, which enabled high surface area, light absorption in a wide wavelength range, plasmon-induced sensitization of TiO2, and fast electron transfer. Considering the excellent photoconversion efficiency of TiOx–Au NCs, it could be applied for catalyzing a variety of other chemical reactions and for developing sensors. Keywords: one-pot synthesis, TiOx-Au nanoparticles, TiCl3, catechin, photocatalytic degradation, dyes, photocatalytic bacterial inactivation

博士<br>國立中山大學<br>材料與光電科學學系研究所<br>107<br>This dissertation describes the synthesis of low-dimensional nanostructures via a series of facile aqueous solution methods at low temperature (<2000C). We started with the fabrication of vertically aligned ZnO nanorods (NRs) on aluminum-doped zinc oxide (AZO) substrates by a single-step aqueous solution method. In order to strengthen photoluminescence (PL) property, ZnO nanorod arrays were annealed at various temperature. We found that the annealing temperature strongly affects both the near-band-edge (NBE) and visible (defect-related) emissions, this eventually leads to the understanding of the optimum annealing condition to achieve enhanced optical properties. Some important findings were found from the PL study, for example, the enhancement of NBE is due to the activation of radiative recombinations associated to hydrogen donors (Ho), and the reduction of visible emission is mainly because of the annihilation of OH groups from the ZnO surface. This interesting finding motivated us to synthesis ZnO hybrids so that we can exploit its promising optical properties in the photocatalysis application under UV or visible light illumination. Next, the plasmonic Au nanoparticles were deposited on the ZnO nanorod arrays to fabricate a noble metal/semiconductor hybrid structures. Interestingly, this Au/ZnO platform exhibits amazing UV-Vis photocatalytic activity alongside the strong luminescent properties. The visible-light active photocatalysis is assisted by localized surface plasmon resonance (LSPR) excitations while the strong absorption and charge separation under UV irradiation is responsible for enhanced catalytic performance. Besides, the enhancement in optical properties is mainly due to local field enhancement effect and the coupling between exciton and LSPR. For the first time, we showed that the plasmonic enhancement of photocatalytic performance is not necessarily a trade-off for enhanced near-band-edge emission in Au/ZnO. The excellent emission property and photocatalytic activity results motivated us to combine low-dimensional ZnO nanostructures with some earth-abundant two-dimensional (2D) materials as a replacement of expensive noble metals. Thus, we prepared heterodimensional nanostructures of 2D ultrathin MoS2 nanosheets interspersed with ZnO nanoparticles by using a facile two-step method. Foremost sonication-aided liquid phase exfoliation technique (LPE) was used to exfoliate ultrathin MoS2 nanosheets in ethanol/water solvent, subsequently a wet chemical process was employed to realize interspersion of ZnO nanoparticles onto the MoS2 surface. In this case, ultra-thin MoS2 nanosheets acted as the support for the nucleation of various concentrated small ZnO dots. The photocatalytic activity of the ZnO/MoS2 nanocomposites was performed with organic dye pollutants and tetracycline, a common antibiotic, as a model compound under visible-light irradiation. We found extremely high catalytic efficiency with these composites under visible light, where the reaction rate of pollutant degradation is about eight times higher than those of commercial P25-TiO2 photocatalysts. This outstanding photocatalytic activity of the heterodimensional hybrids results from the synergetic effects of ZnO and MoS2. Most importantly, the heterojunction formation between ZnO and MoS2 facilitates the separation of photogenerated active charge carriers, leading to the enhancement of photocatalytic performance. Moreover, a tentative mechanism for photocatalytic degradation was proposed in this report, which can provide valuable insights for the exploration of cost-effective nanoscale hybrids constructed from atomically thin layered materials. Finally, we have synthesized mesoporous C-ZnO nanostructured via a facile one-step hydrothermal process, and then liquid-exfoliated 2D MoS2 nanosheets were integrated with the C-ZnO through simple thermal treatment to obtain C-ZnO@MoS2 composites. The photocatalytic activity was evaluated under visible light irradiation and we found the significant enhancement in photodegradation of organic dye molecules by the introduction of MoS2 nanosheet on C-ZnO. Such a significant photoactivity could be attributed to the MoS2 nanosheets that strengthen the visible-light absorption to create the electrons and holes in the system and their favourable separation occur by the electron transaction between ZnO, and MoS2. The synergistic effect between carbon, MoS2 and ZnO makes C-ZnO@MoS2 composites a suitable visible-light driven photocatalyst.

碩士<br>逢甲大學<br>材料科學與工程學系<br>105<br>There are three subjects in this thesis, which are the synthesis and application of ZnO nanostructures, Cu-doped ZnO nanowires, and graphene/ZnO nanocomposites, respectively. First, ZnO nanoporous films have been grown on the stainless steel mesh substrates with ZnO seed layer by an aqueous chemical growth method at the low reaction temperature. The concentration of folic acid plays a crucial role for controlling the morphology of ZnO nanostructures. The ZnO nanoporous films can provide a higher surface-to-volume ratio to enhance the higher photocatalytic activity under 10W UV light irradiation. Second, Cu-doped ZnO nanowires have been fabricated on glass, stainless steel mesh, and carbon cloth substrates with ZnO seed film by a facile aqueous chemical growth method at the low reaction temperature. The concentration of copper(II) chloride was exploited to control the Cu doping concentration. The Cu-doped ZnO nanowires exhibit strong green emission attributed to oxygen vacancies and a very weak UV emission from band gap. Cu-doped ZnO nanowires grown on the carbon cloth substrate can provide a higher surface-to-volume ratio and separation efficiency of photogenerated electron-hole pairs, which exhibit excellent photocatalytic activity for the photodegradation of methylene blue under a 10 W UV light irradiation. Third, graphene/ZnO nanocomposites have been synthesized by a sonochemical method and aqueous chemical growth method. The photocatalytic activities of the different weight of graphene were evaluated in the photocatalytic degradation of methylene blue under 10 W UV and visible light irradiation. The graphene/ZnO nanocomposites revealed much higher photodegradation efficiency than commercial ZnO or TiO2 nanopowders. The novel graphene/ZnO nanocomposites will offer promising applications, such as solar energy conversion, water splitting, and energy storage.