Study On SiO₂ And Polystyrene Colloidal Dynamic Assembly Directed By Ion Diffusion

Due to some great characteristics such as optical frequency bandwidth,low energy consumption,powerful anti-interference ability,and faster transmission speed than semiconductor,colloidal crystals are widely used in bio-sensing materials,photon transport,lightweight structural materials and other fields.There are several methods to prepare colloidal crystals such as gravity sedimentation,vertical sedimentation,electrophoretic deposition and so on,however,these methods requires severe conditions and are difficult to get a single layer of colloidal crystals as well.In this paper,a new method is put forward.The colloidal microspheres with Brownian motion are pushed by the concentration gradient from the diffusion of metal irons,and make dynamically assembling.Single layer structure of colloidal crystals can be easily prepared with the method.In the present research on colloidal crystals,there is no related reports concerning dynamically assemble colloidal microspheres using this method.First,SiO₂ colloidal microspheres were prepared by St?ber method in this article.Silica nanoparticles were carried out using an alcohol-water mixed system,with TEOS as silicon source and ammonia as catalyst prepared by St?ber process.The effects of ammonia concentration,TEOS concentration,temperature and ethanol concentration on the silica particles were investigated..The prepared SiO₂ colloidal microspheres were characterized by TEM,and uniform particle size of SiO₂?size 500 nm?microspheres were obtained at 30 ?,while the molar ratio of ammonia,TEOS,water and ethanol was 2: 0.51: 15: 11.However,the particle size of the prepared microspheres is lower than micrometer,and the colloidal microspheres required in the following experiments need to be very uniform and cannot be agglomerated or aggregated,and moreover,the particle size was required to be above micrometer scale.Therefore,the prepared SiO₂ particles have not been used for the following experiments.Next,the electrode pattern?triangle and square?was designed.Colloidal microspheres need to be driven for dynamic assembly,so using the electrode for uniform ionization of metal ions during the experiment is a necessity,andthis causes colloidal microspheres to be assembled neatly.According to the experimental needs,therefore,different kinds of metal were tried,and finally,iron was proved to be the most appropriate metal;and then with the processes like image development,vapor deposition,glue removal and required reagents,the satisfactory iron electrode was prepare,which could uniformly ionizeferrous irons with impressed current.Finally,the SiO₂ microspheres solution and polystyrene?PS?colloidal microspheres solution were prepared in different proportions of ethylene glycol?EG?-aqueous solution,and a neat crystal was obtained,which was assembled through triangular and square electrodes.Then,Si O 2 colloidal microspheres was modified by 3-aminopropyltriethoxysilane?APTES?in anhydrous toluene.It is indicated that the SiO₂ colloidal microspheres,which were modified and characterized by the Zeta potentiometer,contain positive charge on the surfaces,and then neat crystal was obtained in the same way.Different particle size of SiO₂ colloidal microspheres were injected to a certain conc entration of glycol in aqueous solution,the smaller ones after bigger ones.Crystalline with surrounding structure,bigger microspheres in the middle and smaller ones in the round,was prepared under the concentration gradient control of metal ions.That is,the dynamic binary colloidal crystal was successfully assembled.