Preparation Of Thiolated Silica Particles Via St?ber Method And Their Properties

Silica particles have shown important value in the field of material chemistry and physics due to its characteristics of adjustable size,morphology,microstructure and easy surface functionalization,especially thiol-functionalized silica particles,which are widely used in the fields of heavy metal ions adsorption,catalyst loading,and biomedicine,etc.However,due to the complexity of hydrolysis/condensation of mercaptosilane and the study of the correlation between the kinetic process of hydrolysis/condensation of mercaptosilane and size/morphology/composition of thiolated silica particle are always at the empirical level.Therefore,in this thesis,based on Stober method,3-mercaptopropyltrimethoxysilane(MPTMS)was employed as precursor,a series of thiolated silica particles with various sizes,thiol contents,sulfur compositions,and microstructures were designed and prepared by quantitative study on hydrolysis/condensation of MPTMS and growth mechanism.On this basis,its performance and application are further evaluated.The main research contents are as follows:1.First,silica particles with diameter of 200 nm were used as seed particles and MPTMS was used as precursors,the hydrolysis/condensation of MPTMS and chemically modified silica particles with thiol group were studied by changing the pH,alcohol/water volume ratio and the concentration of MPTMS in the reaction medium.Meanwhile,Ellman’s assay and Raman spectroscopy were used to quantitatively characterize the evolution of thiol group modifications on the surface of silica particles.Then,silica particles with different amount of thiol groups were used as the adsorption matrixs for Au3+.After reduction by NaBH4,silica composite nanoparticles supported by gold nanoparticles(SHSiO2/Au)were obtained,which showed good catalytic degradation activity.2.Based on the above results,the relationship between the hydrolysis/condensation of MPTMS and the size/morphology of thiolated silica particles by Stober method was further studied.The hydrolysis/condensation of MPTMS was quantitatively analyzed in the reaction medium with different alcohol/water ratios.It was found that under the condition with 50%water content,the hydrolyzed products of MPTMS are mainly sulfydryl monomers with higher activity,leading to a more rapid nucleation and growth rate,eventually thiol-containing silica particles with larger size were obtained.However,under the condition with 90%water content,the MPTMS molecules are difficult to disperse in the solvent,but easy to form water-in-oil emulsion vesicles.The hydrolyzed products of MPTMS are mainly disulfide bonded dimers with low activity and slow nucleation/growth rate,resulting in the formation of disulfide bond-containing silica particles with smaller size.3.Thirdly,we further prepared thiolated mesoporous silica particles by change molar ratio of MPTMS to TEOS,and the concentration of cetltrimethyl ammonium bromide(CTAB)in sol-gel method.The content of thiol groups in mesoporous silica particles can reach 115 μmol/g,and the pore size can be accurately adjusted between from 6 to 2.5 nm.This work not only efficiently adjusted the ultramicroporous and mesoporous structure of thiolated mesoporous silica particles,but also established the correlation between the thiol group content in mesoporous silica particles and the adsorption efficiency of Au3+.This lays the foundation for catalysts loading and controllable catalysis in future research.4.Finally,in order to expand the optical application of thiolated silica particles,we introduced chloroauric acid into the MPTMS reaction system.Here,Au3+is not only reduced to Au+by MPTMS but also interacts to form Au(I)-S complexes.Using the Au(I)-S complex as a building unit,the stable fluorescent silica particles can be formed by ammonia catalyzed hydrolysis/condensation.The prepared particles have a large Stokes shift and good fluorescence stability,which can be used in biofluorescence imaging and many other fields.After calcination,the prepared particles,the silica particles loaded with Au nanoparticles were obtained,which showed good activity and sensitivity in SERS detection.