Design And Mechanism Of Novel Photocatalytic Antibacterial System

There are many disease-treating bacteria in the environment.They can be transmitted to our hands,oral cavity and other internal bodies through contact,airborne,food,etc.,causing diseases such as tetanus,typhoid,pneumonia,syphilis,cholera and tuberculosis.Therefore,it is of great significance to develop efficient sterilization methods.Photocatalytic technology is favored by scientists because it uses sunlight,does not consume other energy sources,has low energy consumption,simple operation,no secondary pollution,and mild reaction conditions.Currently,Ti O2 is the most widely used semiconductor material.However,Ti O2 can only be excited by ultraviolet light due to its wide band gap.Ultraviolet light only accounts for a small part of the sunlight(less than 5%)and causes human body damage.At the same time,the high photogenic carrier recombination efficiency of Ti O2 also makes its quantum efficiency very low.How to obtain a visible light driven catalyst that can fully utilize sunlight and has a high carrier mobility has become an important research area.Therefore,this paper intends to solve the above problems from the following three aspects:(1)exploring the new photocatalysts and modifying them for high sterilization performance,to improve the utilization of light energy and the efficiency of carrier separation;(2)designing a new synergistic system to improve sterilization efficiency,exploreing the feasibility of photocatalytic-photothermal synergistic antibacterial system,and the mechanism of mutually reinforcing effect;(3)designing a micromotor to increase the microscopic contact between the catalyst and the bacteria,increasing the production and transportation of active species,thereby improving sterilization efficiency.In view of the above assumptions,this paper has carried out the following work:(1)Research of carbon nitrogen oligomers for photocatalytic antibacterial property of Escherichia ColiLow quantum efficiency is the main factor restricting the development of C3N4.Compared with traditional doping,composite and other more complicated methods,this work is only to reduce the calcination temperature of melamine and add water to obtain Cx Ny oligomers.Cx Ny that we obtained by this simple method contains four elements,carbon,nitrogen,oxygen and hydrogen.We explored the effects of these four elements and involved functional groups on the polymerization path,light absorption,and carrier separation efficiency.Through function fitting,we believe that the degree of polymerization is mainly affected by C-OH,the absorbance,the separation efficiency and active species are affected by RC-O/C-N,the oxidation capacity was improved after doping C-O-C bond,so the photocatalytic bactericidal activity was significantly increased.In addition,the C-O-C bond induces nanorod formation,and forms heterojunctions.The nanorod can effectively capture light energy,and the heterojunctions can improve carrier separation efficiency.As a result,Cx Ny will provide a new way to improve the photocatalytic activity.(2)Synergistic photocatalytic-photothermal contribution of Bi OI-GO nanocomposites to antibacterial activityA stably combined Bi OI-graphene oxide(GO)composite was prepared through a facile solvothermal method.Bi OI crystals were uniformly distributed on the GO nanosheets by the formation of Bi-C bond.Based on the various characterizations,the high specific surface area,the enhanced light absorption with the extension into NIR region and the efficient transfer of photo-induced electrons by the conductivity of GO was demonstrated,which was beneficial for the photocatalytic activity.More importantly,the photothermal effect of GO improved the two main factors affecting photocatalytic activity.On the one hand,PTE raise the solution temperature of Bi OI-GO composite with higher photothermal conversion efficiency and induced the photo-generated electrons from Bi OI crystals to obtain more energy and higher carrier mobility.On the other hand,the temperature elevation of Bi OI-GO composite improved its capability of light absorption.As a result,Bi OI-GO composite presented the synergistic photocatalytic-photothermal effect to the improvement of antibacterial property for Acinetobacter baumannii bacteria with the TOC removal and leakage of K+ ions,in comparison to the individual photocatalytic process.The synergistic photocatalytic-photothermal contribution of Bi OI-GO composite provided a significance for the potential application of environmental disinfection in the future.(3)Synergistic photocatalytic-micromotor contribution of C-Bi OCl nanosheet to antibacterial activityAlthough photocatalysis and photocatalytic-photothermal synergistic systems can effectively improve sterilization efficiency,the microscopic contact between bacteria and the catalyst in these systems can only rely on the added macro-stirring,and cannot effectively contact the bacteria with the catalyst,thoerefore,we mainly designed micromotors to promote the collision efficiency of bacteria and catalysts and improve bactericidal activity.Compared with the traditional driving force by the bubble,electric field drive is favored by scientists,because it does not require additional energy.We chose Bi OCl as a micromotor because it has an internal electric field,but its visible light response and the electric field is weak.Therefore,we added carbon to the Bi OCl lattice to enhance visible light absorption and increase the non-uniform distribution of the electric field to strength the electric field,thereby effectively promoting the movement of the catalyst.Therefore,the strong internal electric field of C-Bi OCl allows to generate faster speeds without consuming energy,increasing the collision probability and contact between bacteria and the catalyst,and improving the sterilization ability of the Bi OCl photocatalyst itself.The attractive performance of this miniature engine,which relies on its own electric field as the driving force of motion,plays a more economical and sustainable role in the fields of defense,environment and biomedicine.