| As the thickness of the ozone layer has decreased during recent decades, people are likely to be exposed to an increasing dose of ultraviolet radiation. This has been correlated with a higher risk of damage to the human body such as premature aging of skin, skin cancer and cataract. Excessive exposure to ultraviolet rays in sunlight can also induce coloring and deterioration in paper, paint, synthetic resins, and so on. The Ultraviolet Protection Conference held in London at 1995 showed that great attention has been paid to shielding from UV irradiation.Nano-oxides, such as titanium dioxide and zinc oxide, have characteristics making them ideal for use as broad-spectrum physical sunscreens in personal-care products. They are relatively transparent to visible light, but almost opaque to ultraviolet radiation. Compared to chemical sunscreens, nano-oxides have many advantages, such as none-toxcity, insipidity, chemical and thermally stability. As a good alternative to chemical sunscreens, nano-oxides have been widely used in many fields.However, there is no uniform detection method and standard to assess UV-shielding capabilities of nano-oxides now. The goal of our work in this paper was to set up an assessing method and to develop a relative instrument for the evaluation of UV-shielding capacities of nano-oxides.Chapter one: Critical reviewsA critical review of present development in related fields was presented in this part: the summary of nano-materials, structure and characteristics of nano-oxides, mechanism of UV-shielding, and process in the study of UV-shielding characteristicsof nano-oxides.Chapter two: Studies on the assessing method of UV-shielding capacity of nano-oxidesSPF and ultraviolet spectrophotometry are two widely used methods in monitoring the UV-shielding capacity of chemical sunscreens, but they cannot be directly used to evaluate the characteristics of nano-oxides, for the dispersity of nano-oxides is different from that of organic sunscreens. In this part, a simple assessing method was introduced which was based on ultraviolet spectrophotometry, and the experiment conditions were optimized. It showed good results when used to evaluate the UV-shielding capacity of real samples.Chapter three: Development of the assessing instrument for UV-shielding capacity of nano-oxidesFor the moment, most assessing instruments for UV-shielding are made by foreign factories, which are very expensive. But in our country there are no succedaneous products. Based on the work in Chapter Two, we succeeded in developing an instrument specialized at assessing the UV-shielding capacity of nano-oxides. This instrument possesses many advantages, such as short analysis time, simplicity, good reproducity and high precision, which supplies a gap in this field and has great market potential.Chapter four: Preparation of nano titanium dioxide film electrode and its application in UV-shielding Capacity assessment of nano-oxidesA nano titanium dioxide film electrode was prepared by sol-gel method and applied for assessing the UV-shielding capacity of nano-oxides. The results characterized by AFM and XRD showed that the titanium dioxide electrode was anatase, which could generate photocurrent when illuminated by ultraviolet radiation of 200-3 80nm. The photocurrent decreased differently as different nano-oxides were added in the system. For this reason, we used photocurrents to evaluate UV-shieldingcapacity of nano-oxides, and got the same results with ultraviolet spectrophotometry. Therefore, it is a new and feasible method for the UV-shielding capacity evaluation of nano-oxides though further researches should be done.Chapter five: Application of nano titanium dioxide film electrode in COD detectionIn this work, the nano titanium dioxide film electrode was used for chemical oxygen demand (COD) determination based on the charge transfer on the interface of TiOa film electrode and the passing solution. The photoelectric behavior of the TiO2 film electrode was studied, and the results showed t... |
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