Preparation And Visible-light Photocatalytic Properties Of Polyphenol-titanium Dioxide Hybrid Nanoparticles

TiO₂ has attracted a lot of attention due to its stable chemical properties,good biocompatibility,mature preparation process,cheap price and excellent optical properties.It has been found that TiO₂ is a wide bandgap semiconductor,which can only absorb ultraviolet light,which limits the application of TiO₂ in reality to a certain extent.In order to broaden the absorption range of TiO₂ in the visible light region,TiO₂ is often compounded with other materials to form composite nanomaterials.TiO₂ can not only catalytically degrade organic dyes,but also be used for sterilization and anticancer,which has a good application prospect in the field of biomedicine.However,its sterilization and anticancer properties are limited to ultraviolet irradiation.So the clinical application of TiO₂ is limited due to the poor penetration capacity of ultraviolet light.In order to solve this problem,TiO₂ is often combined with metal nanoparticles to broaden the absorption range of TiO₂ in the near-infrared region,so that the goal of controlled drug release in vivo could be achieved.In this paper,Phenol polymer?PP?and TiO₂ were compounded by hydrothermal method and sol-gel method to prepare two PP-TiO₂ composite nanoparticles with different morphologies,which broadened the absorption range of TiO₂ in the visible light region and the various morphologies of PP-TiO₂ for the influence of photocatalytic performance were explored.On the other hand,silver nanoparticles were compounded with TiO₂ to expand the absorption of TiO₂ in the near-infrared region,and the effect of Ag amount on the photocatalytic activity of PP-TiO₂ hybrid nanoparticles was studied.1.PP was polymerized by Using Enzyme-catalyzed polymerization with phenol as the raw material and polyethylene glycol?PEG?as the guiding template,enzyme and H₂O₂ as the catalysts.And its structure is characterized by FI-RT and ¹H NMR.It was found that the particle sizes of PP prepared by PEG templates with different molecular weights were different,and the PP emulsion with particle size of 160-300 nm can be prepared by adjusting the molecular weight of PEG.Then,PP and TiO₂ precursor were reacted by hydrothermal method to prepare PP-TiO₂ composite nanomaterial.XRD showed that the sample was anatase TiO₂.UV-vis spectra showed that PP-TiO₂ had strong absorption in visible light region.The results showed that the photocatalytic activity of PP-TiO₂ increased with the increase of PEG molecular weight.Within 3 h,the degradation rate of Rhodamine B by PEG2000 PP-TiO₂ reached 99%,the degradation rates of PEG1500 PP-TiO₂,PEG1000 PP-TiO₂,PEG800 PP-TiO₂,and PEG400 PP-TiO₂ were 97%,84%,83%,and 78%,respectively,and pure TiO₂ only 64%.It is clear that the addition of PP can significantly improve the photocatalytic activity of TiO₂.Within a certain range,the higher the molecular weight of PEG,the higher its regioselectivity of phenol,When PP and TiO₂ were combined,the photoinduced electrons generated by TiO₂ were transferred to the interface between PP and TiO₂ through C-O-Ti bond by light.PP plays the role of electron storage,which can promote effective charge separation.Moreover,PP has strong absorption in visible light area.After PP is combined with TiO₂,the band gap width of TiO₂ decreases significantly.2.PP was used as a template to prepare PP@TiO₂ nanoparticles with core-shell structure by sol-gel method.The influence of catalyst dosage,temperature and TBOT concentration on the morphology of PP@TiO₂ was discussed.The results showed that the prepared PP@TiO₂ nanoparticles have regular morphology and uniform size in the absence of catalyst.With the increase of catalytic dose,the particle size distribution of PP@TiO₂ was gradually ununiform.The temperature had little influence on the morphology of PP@TiO₂.When the content of TBOT gradually increased,the shell thickness of PP@TiO₂ increased accordingly.The photocatalytic properties of PP@TiO₂ with different TBOT contents also varied greatly.The results showed that the catalytic effect of PP@TiO₂ was much higher than that of commercial TiO₂-P25,and its photodegradation rate decreased with the increase of TBOT content.The content of TBOT in PP@TiO₂-25 was the lowest,but the photodegradation efficiency reached 95% within 4 h,showing the best photocatalytic activity.This indicates that the shell of PP@ TiO₂-25 has no obvious hindrance to visible light absorption of PP.However,with the increase of TiO₂ content,the visible light absorption range of PP@TiO₂ nanoparticles gradually decreased,and the light absorption range of PP@TiO₂-100 decreased to 400 nm,and the band gap width rebounded to 3.1 e V.The results show that when the thickness of the shell exceeds a certain threshold,the TiO₂ shell prevents the absorption of visible light by nanoparticles.3.PP@TiO₂-Ag hybrid nanoparticles were prepared by photochemical reduction method.PP@TiO₂ and AgNO₃ solution were mixed and stirred evenly in the dark.Under the ultraviolet irradiation,Ag nanoparticles were reduced and complexed on the surface of PP@TiO₂ to form PP@TiO₂-Ag.The effects of AgNO₃ of different concentrations on the photocatalytic activity of PP@TiO₂ were investigated.The results showed that with the increase of Ag content,the visible light absorption intensity of PP@TiO₂-Ag hybrid nanoparticles had been increased,and the photocatalytic degradation effect were also significantly improved.Among them,the photodegradation rate of PP@TiO₂-Ag increased gradually when the content of Ag increased from 0 to 1%.When the content of Ag increased to 2%,the photodegradation rate of PP@TiO₂-Ag decreased slightly.Ag has strong absorption in the visible/TiO₂ composite can be improved after the TiO₂ visible light catalytic activity,but only the right amount of Ag can effectively improve the photocatalytic activity of TiO₂,when more than the best content,Ag nanoparticles size increase,and even have a reunion phenomenon,is not conducive to Ag dispersed in the surface of TiO₂,which affects to TiO₂ light of Ag nanoparticles to electronic transmission rate,results in the decrease of the photocatalytic activity of TiO₂.After removing PP nucleus,TiO₂-Ag hollow sphere was prepared and compared with PP@TiO₂-Ag photocatalytic degradation effect.The results showed that the photocatalytic degradation rate was doubled after removing PP.PP the importance in the catalytic systems,therefore,PP not only reduce the width of band gap of TiO₂,also have the effect of electronic storage,while increased the strength of TiO₂ visible light absorption,also promoted the effective separation of electronichole,join Ag after improving the electron transfer rate,thus greatly improve the rate of photocatalytic reaction system.