Synthesis And Photocatalytic Properties Of Oil-Soluble Nano-Titania

Nano-titanium dioxide can degrade polluting organics to CO2and H2O. Besides, free radicals from photocatalysis will damage the bacterial cell membrane, promote the loss of cytoplasm and the oxidation of the nucleus, and then kill the bacteria. Therefore, nano-sized titania has attracted extensive attention because of its potential application in the fields of cosmetic, pigment, catalyst, food, solar cell, etc. Because of a large number of hydroxyl existing on its surface, titanium dioxide is quite hydrophilic, and the methods of preparation by current reports are also carried in the water environment, including gas method, sol-gel method, hydrothermal method, micro emulsion method, and etc. However, the methods carried in the oil environment have been rarely reported. There are some application fields that require nano-titanium oleophilic, for example, as a new self-cleaning materials used in textile spinning of some organic materials, as additives to the oil-soluble UV cosmetics, as a photocatalyst for some organic pollutants, as white pigments blended with some organic solvents that were mixed with paint, rubber, plastics so that to improve their performance. Considering oil-water interface method and solvothermal method, we have developed a novel method to synthesize oleophilic titanium dioxide nano-particles. In the process of exploration, we evolved two associative methods, two-step method and one-step method. And the photocatalytic effects of the prepared materials on degradation of the dyes have been tested. The materials prepared by the developed two-step method have some superiorities over the one-step method, such as good dispersibility, good homogeneity, and good photocatalytic activity. On the other hand, one-step method has its own superiorities, including simple processing, short time consuming, and convenient operation. To a large extent, the oleophilic nano-titanium dioxide prepared by these two methods will meet its application requirement in oil environment.Some creative and significant results were obtained:(1) Uniform TiO2nanoparticles of high purity with an average diameter of15-25nm were prepared through one-step method, which were well dispersed in oil. There are a lot of merits for the one-step method, including simple processing, short time consuming, and convenient operation. Uniform TiO2nanoparticles of high purity from two-step method with an average diameter equal to particles from one-step method, which were well dispersed in oil, the materials prepared by two-step method have some superiorities, good dispersibility, good homogeneity, good photocatalytic activity and so on.(2) The influences of some factors on the products were discussed. In terms of the basic reaction conditions, the two methods obeyed the similar rules. The ideal aging temperature of both methods is the same140℃for obtaining the oil-soluble nano-titania. For the one-step method, the products are dispersed in water phase, only when the aging temperature is lower than140℃. For the two-step method, the products are dispersed in oil phase when the aging temperature is controlled in a wide range around140℃, the morphology of the products is not ideal with lower temperature and there will be a serious agglomeration phenomenon with higher temperature. The ideal pH value of the two methods is11, with the pi I lowering to neutral, particle morphology become increasingly vague and vague, but when the pH value changes to12, the condition becoming, the products from the one-step system deposit to the bottom of the water, and the products from the two-step deposit to the bottom of the oil. The ideal aging time is72h, with the reaction evolution, the crystalline state gradually turns excellent, but aging over72h causes particle agglomeration. The ideal surfactant is laurylaminc elected from several surfactants, and with more laurylamine, the uniformity and dispersion of particles become better and better. The ideal organic solvent is cyclohexane selected from several organic solvent.(3) On the basis of the results of the experiments, reaction mechanism was discussed. We have obtained the following conclusions. When the temperature is higher than100℃the Ti resource will polymerize to be nano-titanium; when the temperature is higher than140℃, the nano-titanium will be adsorbed strongly by laurylamine.(4) In order to test the photocatalytic properties of these materials, degradation experiments on CBB and MO are taken to show that the as-prepared materials are provided with excellent photocatalytic properties, and better than market materials.