Preparation Of Titania Nanotube Composites Modified By Aqueous Quantum Dots And Study On Photocatalytic Properties

Visible light,as a new type of energy,has attracted widespread attention from chemists due to its advantages such as affordability,environmental friendliness,and ease of use.Titanium dioxide（Ti O₂）has become a widely studied semiconductor photocatalytic material due to its stable chemical properties,non-toxicity,strong corrosion resistance,and low price.However,the band gap of nanometer titanium dioxide is wide,so it can only be excited by ultraviolet light with a wavelength less than 380 nm,and cannot effectively use sunlight.In addition,the electron hole pairs generated by pure titanium dioxide under light excitation are easy to recombine,which limits its application in the field of photocatalysis.In order to improve the solar energy utilization rate of titanium dioxide nanomaterials,different modification methods are used,such as precious metal deposition,semiconductor composite,metal ion synergy,and so on.This article reports an effective and simple method for synthesizing CdSe/CdS core-shell QDs in atmospheric water medium.The quantum dots were successfully loaded on the surface of titanium dioxide nanotubes（TNTs）,forming a QDs/TNTs composite photocatalyst material.This composite photocatalyst material has been successfully applied to the cyclization reaction between aromatic amines and a series of aldehydes,resulting in corresponding nitrogen heterocyclic compounds.The results indicate that the QDs/TNTs composite photocatalyst material developed in this article has advantages such as good catalytic activity,low cost,easy recovery,and multiple uses.The main research content is as follows:（1）Preparation method of QDs/TNTs composite photocatalyst materials.Firstly,titanium dioxide nanotubes（TNTs）were prepared by hydrothermal method.This tubular structure has a large specific surface area and can provide good adhesion points.Next,a direct aqueous phase synthesis method was used to prepare aqueous quantum dots Cd Se/Cd S core-shell QDs.QDs/TNTs composite photocatalysts were prepared by impregnation method.The results showed that aqueous Cd Se/Cd S core shell QDs were successfully dispersed on the surface of titanium dioxide nanotubes（TNTs）,providing highly dispersed active site,and maximizing the interface contact between the two semiconductors through characterization analysis such as electron microscopy and ultraviolet visible absorption spectrum.The UV visible spectrum shows that the composite photocatalyst material has a wide response range in the region,improving the efficiency of solar light utilization.（2）QDs/TNTs photocatalytic induction of cyclization dehydrogenation reactions of aromatic amines and aromatic aldehydes.We use QDs/TNTs composite photocatalyst materials for dehydrogenation cyclization of aromatic amines and aromatic aldehydes,and optimize the catalyst,solvent,and substrate concentration to obtain the optimal yield.Under optimal conditions,we expanded the substrate range of aromatic aldehydes and successfully synthesized nitrogen-containing heterocyclic compounds such as quinazoline derivatives and benzothiazole derivatives,with moderate to high yields.We tested the morphology and UV visible spectrum of the composite photocatalyst material and found that the catalyst still maintains a good tubular morphology after repeated use,with uniform distribution of quantum dots and good absorbance in the visible light region.This indicates that the composite catalyst material has good stability and has good application prospects in photocatalytic organic synthesis.