Orientador: Oswaldo Luiz Alves / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-19T10:57:30Z (GMT). No. of bitstreams: 1 Rodrigues_CarolinaMartins_D.pdf: 3785624 bytes, checksum: 900b631cfaf12d5446ec0fee86c6118b (MD5) Previous issue date: 2011 / Resumo: Esta Tese visa avaliar a importância da morfologia e da composição química das nanoestruturas de titanato usando a modificação com moléculas orgânicas e desenvolvimento de nanocompósitos poliméricos. As nanoestruturas de titanato de sódio foram obtidas via tratamento hidrotérmico em solução de hidróxido de sódio 10 mol L em 150 e 180°C. De acordo com as caracterizações físico-químicas foi observada a formação de nanotubos de titanato de sódio quando o tratamento hidrotérmico foi realizado a 150°C. No caso do tratamento feito a 180°C foi verificada a formação de nanofitas de titanato de sódio. Os nanotubos de titanato protonados foram obtidos via processo de troca iônica dos nanotubos de titanato de sódio em solução de ácido clorídrico 0,1 mol L. Uma vez obtidas às nanoestruturas de titanato, estas foram submetidas à etapa de modificação com moléculas orgânicas. Essa etapa de modificação consistiu na dispersão destas nanoestruturas em soluções de ácido oléico (OAC) e de brometo de cetiltrimetilamônio (CTAB). Nesta etapa foi verificado que os nanotubos apresentaram maior adsorção/ligação das moléculas orgânicas, o que pode ser relacionado à sua maior área superficial. Em relação à composição química foi observado que os nanotubos de titanato de sódio adsorveram/ligaram maior quantidade de CTAB, o que pode ser indicativo da maior quantidade de grupos OH presentes na superfície dos nanotubos de titanato de sódio, o que poderia resultar em um potencial zeta mais negativo, gerando uma maior interação eletrostática entre os nanotubos e o CTAB. Por último, as nanoestruturas de titanato foram incorporadas em filmes de poli (metacrilato de metila) (PMMA) e borracha natural pelo método de evaporação de solvente. Para o caso do PMMA, as nanofitas resultaram em maior estabilidade termo-oxidativa, e os nanotubos protonados resultaram em melhores propriedades mecânicas. Em ambos os casos, as nanoestruturas foram observadas na forma de aglomerados na matriz. O uso de nanoestruturas modificadas nos filmes de PMMA resultou em melhor dispersão e também na melhoria das propriedades mecânicas. Para os nanocompósitos de borracha, os nanotubos de titanato de sódio foram os que apresentaram melhor dispersão e aumento discreto nas propriedades mecânicas / Abstract: The aim of this thesis was to evaluate the importance of the morphology and chemical composition of titanate nanostructures using the modification with organic molecules and the development of polymeric nanocomposite. The sodium titanate nanostructures were obtained via hydrothermal treatment in a solution of 10 mol L sodium hydroxide at 150 and 180°C. According to the physical-chemical characterizations, it was observed the formation of sodium titanate nanotubes when the hydrothermal treatment was performed at 150°C. In the case of treatment given to 180°C, the formation of sodium titanate nanoribbons was observed. Protonated titanate nanotubes were obtained by ion exchange process of sodium titanate nanotubes in 0.1 mol L hydrochloric acid solution. Once obtained the titanate nanostructures, they were subjected to phase modification with organic molecules. This step of modification was performed dispersing the nanostructures in solutions of oleic acid (OAC) and cetyltrimethylammonium bromide (CTAB). At this stage it was found that the nanotubes had a higher adsorption/bonding of organic molecules, which may be related to their larger surface area. Regarding the chemical composition, it was observed that the sodium titanate nanotubes adsorbed/bonding contain the highest amount of CTAB, which can be related to the greater amount of OH groups adsorbed on the surface of sodium titanate nanotubes, which could result in a more negative zeta potential, producing a greater electrostatic interaction between the nanotubes and CTAB. Finally, the titanate nanostructures were embedded in films of poly (methyl methacrylate) (PMMA) and also films of natural rubber by the casting method. For the case of PMMA, the nanoribbons resulted in a greater thermo-oxidative stability, and protonated nanotubes resulted in better mechanical properties. In both cases, the nanostructures were observed in the form of clusters in the matrix. The modified nanostructures embedded in the film of PMMA dispersed better and the mechanical properties were improved. For the rubber nanocomposites, the sodium titanate nanotubes showed greater dispersion and resulted in a slight increase in mechanical properties / Doutorado / Quimica Inorganica / Doutor em Ciências

Advancing the field of nanotechnology to incorporate the unique properties observed at the nanoscale into functional devices has become a major scientific thrust of the 21st century. New fabrication tools and assembly techniques are required to design and manufacture devices based on one-dimensional nanostructures. Three techniques for manipulating nanomaterials post-synthesis have been developed. Two of them involve direct contact manipulation through the utilization of a physical probe. The third uses optically generated surface acoustic waves to reproducibly control and assemble one-dimensional nanostructures into desired locations. The nature of the third technique is non-contact and limits contamination and defects from being introduced into a device by manipulation. While the effective manipulation of individual nanostructures into device components is important for building functional nanosystems, commercialization is limited by this one-device-at-a-time process. A new approach to nanostructure synthesis was also developed to site-specifically nucleate and grow nanowires between two electrodes. Integrating synthesis directly with prefabricated device architectures leads to the possible mass production of NEMS, MEMS and CMOS systems based upon one-dimensional nanomaterials. The above processes have been pursued to utilize piezoelectric ZnO nanobelts for applications in high frequency electronic filtering as well as biological and chemical sensing. The high quality, single crystal, faceted nature of these materials make them ideal candidates for studying their properties through the designs of a bulk acoustic resonator. The first ever piezoelectric bulk acoustic resonator based on bottom-up synthesized belts will be demonstrated. Initial results are promising and new designs are implemented to scale the device to sub-micron dimensions. Multiple models will be developed to assist with design and testing. Some of models presented will help verify experimental results while others will demonstrate some of the problems plaguing further investigations.

Water pollution has become an environmental catastrophe due to the rapid urbanization. The treatment of dumping of waste chemicals in water bodies has contributed to the increase in pollution. In addition to the pollution caused by waste chemicals, faecal bacteria such as Escherichia, Staphylococcus, Pseudomonas etc., can cause serious health issues. Techniques such as filtration and chlorination provide clean water but are associated with disadvantages such as toxic by-products. Although clean water can be still obtained by these techniques, the development of resistance by microorganisms with such conventional treatments of antibiotics is inevitable and poses a new threat. Various researches have taken place in the past few decades to provide clean drinking water. Photocatalysis is considered to be a promising viable alternative for the existing methods to solve the menace of water pollution. It is an advanced oxidation process where the reactive oxygen species are generated by using nanomaterials that can cause degradation of chemicals and pathogens. Particularly, photocatalysis using semiconductors and their composites have been tested for their use in the destruction of contaminants. Several methods have been used in the synthesis of nanomaterials and the variations in their morphologies have resulted in different applications such as photocatalysis and electrocatalysis. Among all semiconductors, TiO2 has been widely used in this application owing to their non-toxicity and abundance in availability. However, TiO2 can be activated only in the presence of UV light. Therefore, the formation of heterojunctions, doping of metals/no- metals in TiO2 has enabled the activation of TiO2 in the visible region. The former approach has also been studied with ceria and silver salts combination. Besides conventional metal oxides, other transitional metal oxides such as copper oxide and bismuth oxide have also been studied owing to its conducting property and facile growth on substrates respectively for enhanced photocatalysis. All the above tweaking has enabled efficient charge separation, band gap reduction, and prevention of recombination. In this thesis, all the nanomaterials and their composites have been synthesized using simple methods such as solution combustion, hydrothermal, solution co-precipitation, and chemical deposition. The primary aim of this thesis is to synthesize various effective nanomaterials with different morphologies, bandgap engineered nanocomposites, metal or non-metal doped metal oxides for efficient waste water treatment of dyes, antibiotics, phenols, and bacteria. Besides, relying on photocatalytic ability, the photoconductivity and intrinsic conducting properties of nanomaterials were exploited to perform photoelectrocatalysis that enhances the rate of decontamination to several orders than photocatalysis. In addition to focusing on increasing the rate of degradation, the main drawback of photocatalysis which is catalyst retrieval has been overcome using conducting substrates and nanomaterial coated substrates for efficient photocatalytic and photoelectrocatalytic decontamination of waste water. All the structural, morphological, chemical and optical properties were thoroughly studied using various characterization techniques such as XRD, SEM, TEM, XPS, UV-DRS, PL respectively. The rate kinetics of dye, antibiotic and phenol degradation was examined. Experimental data was tested with the proposed model in the case of photoelectrocatalytic degradation. The photocatalysts were also studied for its reusability for many cycles. All the proposed works have analyzed the reason for the enhanced activity by performing scavenger reactions to determine the responsible reactive oxygen species. Thus, this thesis exhibits a thorough understanding of how to design and engineer nanomaterials for photocatalytic and photoelectrocatalytic water remediation. The following are the chapters discussed in this thesis. Chapter 1 discusses the drawbacks associated with the current waste water treatment methods and the possibilities of photocatalysis to replace the existing treatments. The advantages of certain transition metals, conventional methods of synthesis and various other properties of the nanomaterials have been discussed. Chapter 2 explains the synthesis of TiO2 nanobelts using combustion synthesized TiO2 under UV and solar irradiation. The catalyst has been characterized for its structural, morphological, chemical and optical properties. The degradation of anionic and cationic dyes and their activity against E.coli bacteria have been evaluated. The efficiency of this catalyst has been compared with commercial Degussa P25. This study shows the morphological influence of nanomaterials on photocatalytic activity. Chapter 3 describes the synthesis of Ag3PO4 impregnated combustion synthesized TiO2 nanobelts using co-precipitation technique. The activity of this material has been studied under solar light. The catalyst has been characterized for its structural, morphological, chemical and optical properties. Similar to the previous chapter, the degradation of dyes and the antibacterial activity of this catalyst has been compared with commercial Degussa P25. This study explains the importance of morphology and charge carrier facilitation in the case of heterojunction formation. Chapter 4 explains the synthesis of ceria nanoflakes by solution combustion method using ascorbic acid as fuel and PEG assisted sonochemical method. The catalyst has been characterized for its structural, morphological, chemical and optical properties. The effect of silver salts such as AgBr on ceria/Ag3PO4 under visible region for degradation of dyes and antibacterial activity has been evaluated. This work elucidates the effect of band engineering in the charge carrier dynamics between interfaces of components within the catalysts. Chapter 5 elucidates the synthesis of vanadium, nitrogen co doped TiO2 catalysts for the simultaneous degradation of microbes and antibiotics. The primary aim of this work is to understand whether interstitial or substituted doped nitrogen will be effective in the presence of vanadium. The photoactivity of this novel catalyst was studied for its synergistic degradation of antibiotics and bacteria simultaneously towards the prevention of microbial resistance towards antibiotics. Chloramphenicol and E.coli were subjected to photodegradation under visible light. Chapter 6 explains the synthesis of copper oxide based nanomaterial for antibiotic and bacterial degradation by photoelectrocatalysis. In order to enhance the rate of photodegradation, photocatalysis has been upgraded with the application of a potential to photocatalytic systems that possess better charge conducting capability. Highly network like copper oxide has been synthesized using conventional combustion synthesis method and compared with copper oxide nanorods synthesized by hydrothermal method. The rate kinetics of photocatalytic and photoelectrocatalytic degradation of antibiotics has been examined thoroughly and validated based on a cyclic network model. This work demonstrates the synergistic rate enhancing capacity upon combining photocatalysis and electrocatalysis. Chapter 7 discusses the fabrication of Cu/CuO/FTO (fluorine doped tin oxide) based substrates for bacterial degradation. Considering the difficulties in photocatalyst retrieval processes and realizing the importance of electrocatalysis, conducting substrates such as Cu strip, FTO were subjected to antibacterial treatment. Formation of copper oxide onto copper strip during the course of reaction forced us to develop CuO/Cu and CuO/FTO interfaces to examine the photocatalytic and photoelectrocatalytic killing of E.coli. Chapter 8 investigates the fabrication of Bi2O3/Ag based material for photocatalytic and photoelectrocatalytic degradation for phenols and substituted phenols. This work starts with fabrication of Bi2O3 working electrodes by chemical deposition. Photodegradation experiments were conducted under UV irradiation and enhancement of the rate of degradation was observed when the working electrode was deposited with silver nanoparticles via chemical reduction method. Formation of the intermediate Bi(OH)x on Bi2O3 or Bi2O3/Ag has resulted in better hydroxyl radical generation upon excitation. Similarly, surface plasmon resonance due to silver nanoparticles was found to be responsible for augmentation in degradation efficiency of phenol. Chapter 9 briefly summarizes the work and provides future directions. The research work thus attempts to design and engineer photocatalytic nanomaterials that are better than the existing materials and emphasizes the importance towards water remediation.