Preparation And Sterilization Properties Of Photocatalytical Nano-TiO₂ Composite Film On Glass

The worldwide continually strengthened consciousness of environmental protection and more and more scarcity of traditional materials provide the social background and the ecology significance for researches on antibacterial materials. Research on the composition of nano titanium dioxide materials is one of the hotspots of current this kinds of materials researches. Not only it can solves TiO₂ dispersion and immobilized, but also improves the efficiency of the photocatalytic reaction.This dissertation be divided into three parts: (1) Preparation, characterizations and performances study of glass substrate titanium dioxide (Fe-TiO₂ or Ce-TiO₂) film. (2) Study on application and its mechanism of photocatalyitc degradation of AZO-dye wastewater by TiO₂/Fe-TiO₂ or Ce-TiO₂ film. (3) Study on application and its mechanism of photocatalyitc degradation of bactericidal activity. In this paper, some fundamental issues about the preparation of TiO₂/Fe-TiO₂ or Ce-TiO₂ were systematically studied. Conditions in the process of preparation of glass substrate titania film were explored and optimized. The main factors that affect TiO₂ crystal were emphatically studied. Microcosmic mechanism about doping and interface and surface reaction mechanism were analyzed. An analysis of the molecular structure of bacteria and photocatalytic degradation of the reaction course were studied. Study on application of photocatalyitc degradation of AZO-dye wastewater by TiO₂ film , Study on application and its mechanism of sterilization of Gram-negative bacterium,Gram-positive bacterium and Halophilic archaeon by TiO₂ film. TEM analyses were firstly conducted for observation of Halophilic archaeon cell ultrastructure. Conclusions from this study are as follows:1.Preparation, characterizations and performances study of glass substrate titanium dioxide film1.Many factors that affect nano-TiO₂/glass photocatalytic active were inspected comprehensively and systematically. Factors that affect crystal phase and structure and photocatalytic activity of TiO₂ such as: component ratio of precursor, mineral slurry concentration, hydrolysis temperature and time, drying temperature, calcination temperature and time and coating times, etc were emphatically studied.2.Through experiment, TiO₂ thin films were prepared on soda-lime glass by sol-gel method. Those have solved the uses of conventional powder catalysts results in disadvantages in recycle and separation.3.The optimized process conditions of preparation are as follows: volume ratio of precursor: Ti(OC₄H₉)₄: C₂H₅OH: HNO₃:H₂O=1:15: 0.35: 2; hydrolyzed at 40℃; calcined at 450℃for 2h.Among these factors, component ratio of precursor and calcination temperature are considered to be two most remarkables. Preparation confirmed through experiments impact glass nano-TiO₂ order of the primary and secondary factors: Precursor ratio> calcination temperature> calcination time> Sol reaction temperature. The anatase TiO₂ on the surface of glass is moststable when calcined at450℃.2.Preparation, characterizations and performances study of metal ions doped glass substrate titanium dioxide film1. Giving the verification of photocatalytic materials to expand the use of the spectrum , UV excitation extend the possibilities and visible results were be studied.2. XRD, UV-Vis, HRTEM etc techniques were firstly adopted to characteriztions and analyze characteristics of TiO₂/glass doped with metal ion such as: crystal structure, molecular structure, chemical elements and chemical states on the surface, distribution of TiO₂ crystal and thickness of TiO₂ crystal film.3. Study on application and its mechanism of photocatalyitc degradation of AZO-dye wastewater by TiO₂/Fe-TiO₂ or Ce-TiO₂ film.1. A photocatalytic degradation technique has been studied which can speeds-up the reaction and enhances decoloring rate.2. The course of TiO₂ photocatalytic degradation of AZO-dye is the one that C-O-C, C-C bond and then N=N rupture.4. Effects of metal ions-doping TiO₂ film on sterilization(various bacterial and Halophilic archaeon) efficiency1) Experiments were conducted for exploring the efficiency of photocatalytic sterilization of modified TiO₂ films on Escherichia coli, a typical Gram-negative bacterium, and Staphyloccocus aureus Rosenbach, a typical Gram-positive bacterium, and Bacillus subtitles. After TiO₂ treatment, structure changes of cells were directly observed by TEM, and sterilization efficiency were detected with plate counting method. Compared with pure TiO₂ films, modified TiO₂ films show a higher bactericidal rate. Doping of Fe³⁺ improves the bactericidal rate of TiO₂ films on Escherichia coli from 87.4% to 95.8%, and on Staphyloccocus aureus Rosenbach from 79.4% to 88.3%, and on Bacillus subtitles from 80.4% to 86.3%, respectively. Similarly doping of Ce⁴⁺ also increases the bactericidal rate of pure TiO₂ film. Results suggest that bactericidal rate of pure TiO₂ film can be increased by doping of metal ions with acceptable concentration range. 2) It is the first report about a study on sterilization of TiO₂ on Halophilic archaeon. At first, sterilization efficiency of UV irradiation was detected on archaean. UV (365nm or 310nm) irradiation for 40 min were proved to be able to kill most of tested archaean. More than that, treatment by pure TiO₂ film under UV irradiation displays better sterilization efficiency. It seems that TiO₂ can been utilized effectively to sterilize archaean. Meanwhile, effects of metal ions doping also were detected on archaean. Compared with pure TiO₂ film, modified film shows higher sterilization efficiency. Such as, Fe³⁺ doping improve the sterilization efficiency from 88.6% to 94.5% under 365nm UV irradiation, and from 90.7% to 93.5 % under 310nm UV irradiation. Result of Ce⁴⁺ doping displays the same positive effects.3) The sterilization mechanism of TiO₂ film on Halophilic archaeon was firstly discussed in this paper. Under UV irradiation, TiO₂ is photo-excited and generates reactive oxygen species (ROS), such as free radicals OH" and H₂O₂. Different from general bacteria, J7 Halophilic archaeon owns particular Na⁺-K⁺ balance system. Depend on this system, they maintain the normal range of intracellular Na⁺ concentration by excluding excessive Na⁺ ions rapidly, and survive the special environment with higher salt concentration. Upon treatment with TiO₂ photocatalyst, Na⁺ excluded by archaea might interfere with function of Ti bond, which will decrease the destruction potential of ROS on cell wall of J7 Halophilic archaeon. Meanwhile, with higher penetrability, H₂O₂ can enter archaea cells, degenerate proteins and fragmentize DNA molecules. It is obvious that, TiO₂ lead to death of J7 Halophilic archaeon mainly by destroying intracellular structures and increasing the leak of K⁺ ions.4) Up to now, reports about TiO₂ sterilization were confined to bacterium and eukaryotic domains. In this paper, except for detecting the sterilization efficiency of TiO₂ on archaeon, we further observe the ultrastructure change of archaeon treated by TiO₂ with TEM (Transmission Electron Microscope), which definitely will supply a gap about utilization of TiO₂ in archaeon domain. At the same time, ultrastructural studies provide direct evidences for further exploring the bactericidal mechanism of TiO₂ photocatalyst. As a result, the evolutional relationships between archaeon and other life domains will be demonstrated comprehensively based on the new way of thinking provided by exploring death mechanism of archaeon.