The search for alternative materials with high dye adsorption capacity, such as methylene blue (MB), remains the focus of current studies. This computational study focuses on oxides ZnTiO3 and TiO2 (anatase phase) and on their adsorptive properties. Computational calculations based on DFT methods were performed using the Viena Ab initio Simulation Package (VASP) code to study the electronic properties of these oxides. The bandgap energy values calculated by the Hubbard U (GGA + U) method for ZnTiO3 and TiO2 were 3.17 and 3.21 eV, respectively, which are consistent with the experimental data. The most favorable orientation of the MB adsorbed on the surface (101) of both oxides is semi-perpendicular. Stronger adsorption was observed on the ZnTiO3 surface (−282.05 kJ/mol) than on TiO2 (–10.95 kJ/mol). Anchoring of the MB molecule on both surfaces was carried out by means of two protons in a bidentate chelating (BC) adsorption model. The high adsorption energy of the MB dye on the ZnTiO3 surface shows the potential value of using this mixed oxide as a dye adsorbent for several technological and environmental applications.

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A microfabricated colloidal array scheme has been proposed to design and develop a colloid engine based on any colloidal substance or even ionic liquids. The design proposes to build the engine in halves, in order to obviate the maximum width-to-length ratio that a duct can have by using microfabrication techniques; the design also contemplates the existence of both extractor and accelerator electrodes in order to reach the required Isp and focus the droplet jet.The proposed design procedure was used to build a colloid engine that uses as colloid propellant formamide doped with Nal; the engine is composed of one hundred and twenty one needles distributed among eleven manifolds. A set of eight masks was tailored to process the halves of the engine as a trade off between robustness and engine performance.The experimental results consist of the microfabrication processes related with the first three masks, corresponding to the aligning marks, duct formation and electrode ring bed formation. The remaining microfabrication steps are expected to be completed during the summer of 2001.All the experiments for the first prototype are also expected to be finished by the end of the summer of 2001, and then we will move towards a more advanced engine concept.It has been proposed to change the substrate material from silicon to quartz in order to increase the engine breakdown voltage. A new colloid engine generation has also been proposed using three wafers, carving the ducts along the bottom wafer, forming the emitter tips and the extractor electrodes on the middle wafer and generating the accelerator electrodes on the top wafer. In order to increase substantially the specific impulses a change from formamide to ionic liquids has been suggested: this decision would also eliminate other problems such as clogging but might eventually introduce others, like the need to heat up the propellant up to temperatures where the ionic liquid has high electrical conductivity.Thesis Supervisor:

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The ability of fungus Periconia hispidula (42/07), isolated at the semi-arid of BAHIA in Brazil, to biotransform acetophenone and its derivatives has been studied. The influence of reaction parameters (mean, time, amount of substrate) on the conversion and enantioselectivity of acetophenone reduction was initially investigated. By comparison between culture media (optimized YM / BD / BD supplemented with Fe 2+) BD medium supplemented with Fe 2+ (0.02 g/L) was selected. From the growth curve, the incubation time prior to addition of substrate (4 and 7 days) was determined. The best conversion results for obtaining the (S)-1-phenylethanol, with enantiomeric excess of 98% were reached after four days of previous incubation of the microorganism. The influence of the amount of acetophenone (20 μL to 200 μL) was also analyzed with the objective of evaluating the toxicity of the substrate. Substrate amounts greater than 100 (0.1%) were found to have resulted in conversion and enantioselectivity dropping. The biocatalyst was also tested against 20 prochiral ketones: 2-, 3-and 4-nitroacetophenone; 2-, 3-and 4methylacetophenone; 2-, 3-and 4-methoxyacetophenone; 2-, 3-and 4-bromoacetophenone; 2-, 3-and 4fluoracetophenone; 2,4-dimethylacetophenone; 2,5-dimethylacetophenone and 4-ethylacetophenone. Conversions of chiral alcohols ranged from 56% to 99% with enantiomeric excesses of 54 to over 99%, demonstrating that the fungus Periconia hispidula is a promising stereoselective biocatalyst for application in reduction processes of carbonyl compounds.