Research On Preparation And Application Of Supramolecular Functionalized Au/TiO₂ Composite Materials

Nanomaterials have attracted extensive research interest due to their wide application for the fields of biosensors,energy storage,catalysis,drug delivery and other fields.The semiconductor TiO₂ has attracted special attention because of its good chemical stability,environmental friendliness,and low cost.However,a single TiO₂ severely restricts its application in daily life due to its wide band gap（3.2 e V）,the recombination of photogenerated electrons and hole pairs,and the low utilization efficiency of sunlight.Therefore,it is necessary to modify TiO₂.The semiconductor TiO₂ composite nanomaterial modified by Au can effectively reduce the band gap between TiO₂,and accelerate the electron transfer and improve the absorption and utilization of visible light.As the research basis of supramolecular chemistry,supramolecular macrocyclic compounds play an indelible role in the valve of drug transport or in the specific identification of pollutants due to their unique cavity structure and host and guest specific recognition function.It is functionalized into Au/TiO₂ nanomaterials can combine the host-guest specific recognition of supramolecular macrocyclic compounds with the light and thermal effects of Au and the catalytic and drug-carrying properties of semiconductor TiO₂,which expands the composite nano Research and application of materials in many fields.In this paper,supramolecular macrocycles CB[6]andβ-CD were selected to combine with precious metal Au-modified TiO₂ semiconductors to prepare supramolecular functional Au/TiO₂nanocomposite nanomaterials,and their applications in drug delivery and photocatalytic degradation of pollutants were explored.The specific work is as follows:（1）Instead of directly modifying the supramolecular macrocyclic compounds onto the surface of gold nanoparticles,the prepared gold nanorods（AuNRs）were coated with mesoporous TiO₂（mTiO₂）,which was used as the skeleton structure to modify the supramolecular macrocyclic compounds onto the surface of AuNRs indirectly.Based on this,we prepared AuNR@mTiO₂ by hydrothermal method.Due to the mesoporous structure of mTiO₂,AuNR@mTiO₂ was used as a drug delivery carrier,and then N-（6-aminoethylhexyl）aminomethyl Triethoxysilane（AATS）was used as rod and CB[6]as supramolecular nanovalve modified to the surface of AATS functionalized AuNR@mTiO₂,and the CB[6]encapsulated and AATS modified AuNR@mTiO₂ supramolecular nano-drug carrier system was successfully prepared.Because light is non-invasive,remote and intermittent controlled drug release can be achieved by using light as stimulation condition.Compared with ultraviolet light,near-infrared light（NIR）has better tissue penetration and friendliness.Under the NIR stimulation of,the host-guest interaction between CB[6]and AATS on AuNR@mTiO₂ surface was weakened due to the plasma thermal effect of AuNRs,which causes the supramolecular nanovalve to open and release the drug.In addition,mTiO₂ not only ensures the efficient loading of drugs,but more importantly,under light,TiO₂ itself also generates a variety of free radicals,which can cooperate with drugs to kill cancer cells.The research shows that the AuNR@mTiO₂ drug controlled release system based on the CB[6]supramolecular nanovalve modified by us can achieve good drug loading and near-infrared light controlled release effects of drugs.（2）Photocatalytic technology has attracted much attention due to its advantages of environmental protection,mild reaction conditions,and low cost.Therefore,photocatalytic technology has also been widely applied in various fields.We preparedβ-CD-gold nanostar@TiO₂（β-CD-Au NS@TiO₂）composite photocatalyst by hydrothermal method.We evaluated the photocatalytic activity of theβ-CD-Au NS@TiO₂ composite photocatalyst and discussed the reaction mechanism of the composite photocatalyst.Finally,the photocatalytic degradation of organic pollutant bisphenol A was achieved under visible light irradiation.The structure of composite photocatalytic was analyzed and characterized by UV-Vis,FT-IR,SEM,and TEM.The effects of the surfacemodification of TiO₂,the initial concentration of bisphenol A and the p H of reaction system on the photocatalytic degradation efficiency of bisphenol A have been studied.The experimental results showed that the photocatalytic degradation of the preparedβ-CD-Au NS@TiO₂ for bisphenol A was efficient with a p H of 4.The photocatalytic degradation efficiency of bisphenol A was reached 92.3%.Secondly,the kinetic experiment indicated that the reaction rate constant ofβ-CD-Au NS@TiO₂ was 0.0148 min^-1,which was about 3.3 times that of pure TiO₂.This was because combine TiO₂ with plasmonic metals was one of the efficient approaches to extend the light absorption range to visible and NIR region.In addition,Au NS reduced the band gap width of TiO₂ and slowed down the recombination of photogenerated electron-hole pairs,therefore effectively improved the degradation efficiency of the prepared photocatalyst for bisphenol A.The capture experimented showed that h⁺was the main active specie of theβ-CD-Au NS@TiO₂ composite photocatalytic material.The prepared composite photocatalyst had good stability.Replication experiments showed the efficiency of photocatalytic degradation of bisphenol A could still be maintained above 80%after the composite catalyst were reused for 4 times.The outcome of this paper will provide a new way for the treatment of organic pollutants in the future and promote the development of advanced photocatalytic materials.