Controllable Preparation Of Nano-Silica And Its Applications In Structural Color And Dye Degradation

In recent years,the efficient control of various pollutants has been the focus of scientific research,especially the degradation of organic dyes.Organic dyes are difficult to degrade,and due to their complex composition and great harm,which seriously damages the balance of the ecological environment and poses a great threat to our physical and mental health.In order to solve this problem,this paper puts forward solutions from two perspectives.On the one hand,we aim to construct a structural color material instead of the traditional color material to prevent the generation of dye pollution from the root.On the other hand,we aim to use photocatalytic technology to control the dye pollutants produced.In order to provide high-quality nano-SiO2 microspheres for subsequent experiments,we improved the traditional Stober method and prepared pure amorphous nano-SiO2 in a short time with TEOS as the precursor,ammonia water(NH3·H2O)as the catalyst and ethanol as the dispersant.The quality of SiO2 is improved by two-step dripping with the precursor and differential centrifugation.SiO2 is characterized by uniform particle size,narrow size distribution,good dispersion,high sphericity and smooth surface.Through the control variable method,it is found that,within a certain range,with the increase of the amount of precursor,the decrease of the reaction temperature or the increase of the concentration of catalyst,the SiO2 microsphere particle size will increase,and vice versa.When the water/ethanol volume ratio of dispersant increases from 0:1 to 4:1,the particle size of nano-SiO2 decreases and the dispersion becomes worse.Therefore,SiO2 microspheres with different particle size ranges can be prepared by adjusting the above reaction conditions.Next,the photonic crystals were synthesized using self-made SiO2 microspheres as the basic element,and photonic crystals of different structural colors could be obtained by adjusting the particle size of SiO2 microspheres.It is found that when the particle size increases gradually,the position of the photonic band gap in the film also moves towards the long band.The interior of photonic crystal shows ordered hexagonal arrangement,but some defects cause the band gap position of photonic crystal to shift.Under the condition of low cost and the simplest technology,the quality of photonic crystal prepared by vertical self-assembly method is obviously better than that by spin coating method.By comparing the two kinds of photonic crystals with different sandwich structures,the arrangement of large-small-large structures is smoother and more orderly than that of small-large-small structures.Two-size photonic crystals have many internal defects and poor structural color quality.It is proved that the premise of bright structural color is the component element with uniform particle size.High temperature heat treatment can improve the quality of structural color and enhance the adhesion strength of the film on the slide.Finally,SiO2@Ag,SiO2@Ag@SiO2,SiO2@Ag@SiO2@TiO2 and SiO2@Ag@SiO2@TiO2 core-shell structural materials were synthesized successively.When AgNO3 dosage was 6 mL,the nanosilver(Ag)particle was best coated on the surface of SiO2 microsphere.When the TEOS ethanol solution was 500 μL,NH3·H2O dosage was 3 mL,the thickness of the intermediate SiO2 shell was 20 nm.When the dosage of butyl titanate(TBOT)was 120 μ L,TiO2 coating was optimal.The synthesized nano Ag is of face-centered cubic structure,TiO2 is anatase type,and the core-shell structure is mesoporous material.Its specific surface area increases with the increase of the shell layer.The existence of mesoporous and high specific surface area are conducive to improving the photo catalytic performance of the material.SiO2@Ag@SiO2@TiO2 shows the best photocatalytic activity,which could degrade about 90%methylene blue(MB)and had good cycling stability.