Study On Preparation And Antibacterial Properties Of Metal Doped Nano-sized TiO₂ Antibacterial Micro-powder

The major approach so far to prevent plant diseases caused by pathogenic microbes is to make use of chemical fungicides,which have a good bactericidal effect.However,the fungicide residues not only pollute the crops themselves,but also cause pollution on the surroundings such as water sources,soil and atmosphere,etc..On the other hand,photocatalyst now has become one kind of the most promising fungicides due to its notable features such as high activity,non-toxic,low cost and non-pollution,etc.,which will effectively overcome the drawbacks produced by chemical fungicides.The proposed study directions involved the preparation of TiO₂,photocatalytic degradation and photocatalytic antibacterial has now been becoming upsurge.In this paper,hydrothermal synthesis method is adopted with the doping modifications of metal ions of Cu2+,Fe3+,Zn2+,in order to investigate the photocatalytic activity,antibacterial activity,long-term characteristic and stability of nano-TiO₂ with a component of different modified doping metal ions.?1?Two drying technologies,freezing-drying treatment and hightemperature calcination treatment,are separately adopted for the preparation of pure TiO₂,as well as the molar percentages of Cu2+,Fe3+,Zn2+ doped TiO₂,and metal ions of the micro-powder are 0.1%?0.2%?0.4%?0.8%?1.6%,respectively.?2?Part of the TiO₂ nano-powders are characterized by TEM and XRD.XRD data shows that both the freezing-drying treatment and the high-temperature calcination treatment have not totally changed the crystal structure of the nano-TiO₂.The metal doped TiO₂ micro-powder is one type of anatase whose metal ions always attach to the surface of TiO₂ nanoparticles.?3?The experimental results on photocatalytic activity show that the photocatalytic activity of TiO₂ micro-powder under visible light irradiation is higher than that of the TiO₂ micro-powder under ultraviolet irradiation.With the increase of the addition amount of metal ions,the photocatalytic activity of the metal doped TiO₂ micro-powder will increase first and decrease later.The micro-powder sample whose doping amount of metal ion is 0.4%,has a maximal photocatalytic activity under visible light irradiation or ultraviolet irradiation condition.The photocatalytic activity relations among different doping metal ions are: Zn-doped>Cu-doped>Fe-doped.Among them,Zn-doped micro-powder sample with a proportion of 0.4%,has a degradation rate on methylene blue which can reach 97.15% under the illumination condition for 20 min.?4?Studies on the antibacterial properties show that the metal ion toxicity of the sample powder plays a major role in antimicrobial activities,whose specific case can be characterized as: Cu-doped>Zn-doped>Fe-doped.The antibacterial properties of different metal doped TiO₂ micro-powders have been significantly improved under ultraviolet irradiation or visible light irradiation condition.The experimental results show that the photocatalytic reaction plays a major role in antimicrobial activities.Doping contents of the samples with a good photocatalytic antibacterial effect are 0.2% Cu-doped,0.4% Zn-doped and 0.8% Fe-doped nano-TiO₂ micro-powders with a freezing-drying treatment,respectively.?5?Quantitative bacteriostasis tests indicate that the antimicrobial effects of the nano-TiO₂ samples with freezing-drying treatment can be characterized as follows: 0.4% Zn-doped > 0.8% Fe-doped > 0.2% Cu-doped.The bacteriostatic rate of the nano-TiO₂ micro-powder on epidermis Staphylococcus is higher than that of Staphylococcus aureus.The 0.4% Zn-doped nano-TiO₂ micro-powder,whose reaction concentration is 8 mg with a period of 60 min exposure to ultraviolet rays,can achieve a 96.37% bacteriostatic rate on epidermis Staphylococcus and a 92.84% bacteriostatic rate on Staphylococcus aureus,as well as a 100% bacteriostatic rate on epidermis Staphylococcus with 80 min exposure to ultraviolet rays.?6?The experimental results of long effectiveness show that the bacteriostatic properties of the metal doped TiO₂ micro-powders have decreased to some extent after immersing for 24 h,as well as the stability test results show that the bacteriostatic properties of these three powder samples on both epidermis Staphylococcus and Staphylococcus aureus have decreased with little range,which prove that the long effectiveness and the stability of these three different kinds of metal doped nano-TiO₂ micro-powders are not as good as desired.