Effect of the iron doping on the thermal decomposition of the polymeric precursor for the titanium dioxide powder synthesis

The Polymeric Precursor Method has proved suitable for synthesizing reactive powders using low temperatures of calcination, especially when compared with conventional methods. However, during the thermal decomposition of the polymeric precursor the combustion event can be releases an additional heat that raises the temperature of the sample in several tens of degrees Celsius above the set temperature of the oven. This event may be detrimental to some material types, such as the titanium dioxide semiconductor. This ceramic material has a phase transition at around 600 ° C, which involves the irreversible structural rearrangement, characterized by the phase transition from anatase to rutile TiO2 phase. The control of the calcination step then becomes very important because the efficiency of the photocatalyst is dependent on the amount of anatase phase in the material. Furthermore, use of dopant in the material aims to improve various properties, such as increasing the absorption of radiation and in the time of the excited state, shifting of the absorption edge to the visible region, and increasing of the thermal stability of anatase. In this work, samples of titanium dioxide were synthesized by the Polymeric Precursor Method in order to investigate the effect of Fe (III) doping on the calcination stages. Thermal analysis has demonstrated that the Fe (III) insertion at 1 mol% anticipates the organic decomposition, reducing the combustion event in the final calcination. Furthermore, FTIR-PAS, XRD and SEM results showed that organic matter amount was reduced in the Fe (III)-doped TiO2 sample, which reduced the rutile phase amount and increased the reactivity and crystallinity of the powder samples.

Photocatalytic decomposition of rhodamine-B using scandium and silver-modified TiO2 Powders

Semiconductor-mediated photocatalytic oxidation is an interesting method for water decontamination and a specially modified TiO2 is said to be a promising material. This study verified that the synthesis of 1wt%Ag modified-Sc0.01Ti0.99O1.995 powder samples prepared by Polymeric Precursor Method is capable of forming a mixture of anatase-rutile phase with high photocatalytic performance. This kind of material is found to have a lower bandgap compared to the TiO2-anatase commercial powders, which can be associated to an innovative hybrid modification. The simultaneous insertion of scandium in order to generate a p-type semiconductor and a metallic silver nanophase acting as an electron trapper demonstrated being capable of enhancing the degradation of rhodamine B compared to the commercial TiO2. In spite of the different thermal treatments or phase amounts, the hybrid modified powder samples showed higher photocatalytic activity than the commercial ones.

Diodo planar orgânico Schottky: construção e caracterização

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Um estudo teórico e experimental de nanoestruturas de 'ZnS': propriedades físicas e químicas

Pós-graduação em Química - IQ

Deposição de filmes finos de SnO2 e GaAs, visando confecção de dispositivos baseados na heterojunção SnO2/GaAs

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Photocatalytic and photoelectrochemical inactivation of Escherichia coli and Staphylococcus aureus

Water disinfection usually requires expensive chemicals or equipment. Chlorination is a common disinfection method, although it is not able to inactivate all pathogens. High concentrations of residual chlorine also cause an unpleasant taste and smell in drinking water. As an alternative, photocatalysis and photoelectrochemical treatment has a high disinfection potential in drinking water by using solid catalysts, such as titanium dioxide. Highly reactive hydroxyl radical generated during the process serves as the main oxidant, capable of inactivating a wide range of microorganisms. In this study, we proposed a novel comparison between Gram-positive and gram-negative microorganisms. An immobilized TiO2 film promoted higher efficiency in water disinfection processes. The treatment effectively inactivated Escherichia coli and Staphylococcus aureus bacterial microorganisms in a shorter period than other alternative methods.

The role of oxygen vacancies and their location in the magnetic properties of Ce1-xCuxO2-delta nanorods

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

A combined experimental and theoretical study on the formation of ag filaments on beta-Ag2MoO4 induced by electron irradiation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effects of time exposure and low power sonochemical treatment on ZnO mesostructures

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Finite-difference calculation of donor energy levels in a spherical quantum dot subject to a magnetic field

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Photoelectrochemical reduction of CO2 on Cu/Cu2O films: Product distribution and pH effects

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Electrical transport mechanisms and structure of hydrogenated and non-hydrogenated nanocrystalline Ga1-xMnxAs films

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Thermal inkjet printing of copper tetrasulfonated phthalocyanine (CuTsPc) as a semiconducting layer on flexible MIS capacitors

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Nanostructured TiO2-based composites for light absorption

Metal oxidenanocomposites were prepared by two different routes: polyol and sol-gel. Characterization by X ray diffraction showed that the first processproducesdirectly a two-phase material, while the sol-gelpowder never showed second phase below 600 degrees C. Light spectroscopy of the treated powders indicated similarities for the processed materials. Although the overall material compositions are about the same, different structural characteristics are found for each processing. With the exception of Ti-Zn materials, all the double metal oxide powders showed higher absorbance than either TiO2 powder.

Investigation of photoinduced electrical properties in the heterojunction TiO2/SnO2

TiO2/SnO2 thin films heterostructures were grown by the sol-gel dip-coating technique. It was found that the crystalline structure of TiO2 depends on the annealing temperature and the substrate type. TiO2 films deposited on glass substrate, submitted to thermal annealing until 550 degrees C, present anatase structure, whereas films deposited on quartz substrate transform to rutile structure when thermally annealed at 1100 degrees C. When structured as rutile, this oxide semiconductor has very close lattice parameters to those of SnO2, making easier the heterostructure assembling. The electrical properties of TiO2/SnO2 heterostructure were evaluated as function of temperature and excitation with different light sources. The temperature dependence of conductivity is dominated by a deep level with energy coincident with the second ionization level of oxygen vacancies in SnO2, suggesting the dominant role of the most external layer material (SnO2) to the electrical transport properties. The fourth harmonic of a Nd:YAG laser line (4.65 eV) seems to excite the most external layer whereas a InGaN LED (2.75 eV) seems to excite electrons from the ground state of a quantized interfacial channel as well as intrabandgap states of the TiO2 layer.