Both physical and chemical procedures were applied to immobilize yeast alcohol dehydrogenase (yADH) on titania nanoparticles. It was found that chemical immobilization is an authentic method due to providing a strong bond between the enzyme and the support. The immobilization was confirmed by Fourier transform infrared spectroscopy and transmission electron microscopy. The immobilization parameters such as enzyme concentration, time of immobilization, and glutaraldehyde concentration were optimized based on the maximum immobilization yield and the best enzyme catalytic performance. Activity and kinetics of yADH before and after immobilization were studied, and the stability of enzyme at different pHs and temperatures was investigated. The optimum pH for the incubation and activity of yADH was obtained at 7.0, and the activity of immobilized yADH reached more than 80% of its initial activity after 30 days of storage at 4 °C. The reusability of yADH was improved by immobilization as revealed by retaining 84% of its initial activity following 10 cycles. Finally, we suggested that the immobilization of yADH is a promising method for the removal of substrate inhibition in the reaction of formaldehyde to methanol.

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Titanium dioxide (TiO2) nanotube arrays were prepared at room temperature by electrochemical anodization of a pure titanium foil in electrolyte solutions containing ethylene glycol as a solvent and de-ionized water and ammonium fluoride as additives. Since the morphology and size of TiO2 nanotubes play critical roles in determining their performance, the control of geometrical parameters of the nanotube arrays including length and inner diameter are of great importance. The present research demonstrates the significant effects of fluoride concentration and water content in anodizing electrolyte on formation of nanotubes and their dimensions. Scanning electron microscope investigation shows that nanotube arrays are no longer formed in very low or very high concentration of ammonium fluoride. Also, increase in fluoride concentration causes increase in lengths and inner diameters of the nanotubes. Moreover, it is evident that the maximum nanotube growth rate was achieved in medium amount of water. In addition, it is found that the nanotube inner diameter increases by adding more water to the solution.

Titania thin films were prepared by electrophoretic deposition at various deposition times (1, 5 and 10 min) in constant applied potential (5 V). For this purpose, modified titania sol was prepared as a colloidal suspension. The influence of deposition time on the thickness and optical properties of titania films was investigated. Scanning electron microscope images illustrate compact and homogeneous titania films deposited on FTO substrates. The results show that the film thickness increases with increasing the deposition time. It could be inferred from UV-Vis spectroscopy that increasing the thickness of deposited film causes higher absorbance at UV region. Also, increasing the deposition time from 1 to 5 min leads to increase in optical band gap of the deposited films.

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The experiments focused on the influence of strontium and calcium as additional alloying elements on the grain size and phase distribution of AZ91 magnesium alloys. For this purpose, different concentrations of Sr (0.01, 0.1, 0.4, and 0.8) and Ca (0.01, 0.1, 0.4, 0.6 and 0.78) were added. The microsturctural examination of specimens was made by an optical microscope and scanning electron microscope. From obtained results it was found that using 0.4 wt% strontium can provide a fine and uniform structure.

In this study nanocrystalline anatase TiO2 thin films were prepared by electrophoretic deposition of titania sol at various applied voltages. The well-known sol-gel method was used to prepare the titania sol. The influence of applied voltage on the structure, morphology and optical properties of thin films has been characterized by X-ray diffraction, field emission scanning electron microscopy and UV-Vis spectroscopy. The results show that the thickness of the films formed on the substrate increases with increasing the applied voltage. However, with increasing the thickness of the films, the cracks increased and the transparency reduced in the visible region.

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