Design Of Metal-Doped Silica Nanostructures And Their Adsorption And Catalysis Applications

In recent years,with the in-depth application research of mesoporous silica materials,various functionalized mesoporous silica composite materials have shown broad application prospects.Particularly,benefitting from introduction of metals in the silica framework,metal-doped silica composite materials have expanded the performance and applications,which have received extensive attention from researchers.Metal-supported silica-based composites have the problem of easy agglomeration and loss of metal components,which seriously affects their performance.It is necessary to explore hybrid silica composite structures with highly dispersed metal components and their stable binding.How to design metal-functionalized silica materials with this structural property is still a challenging task.This dissertation focuses on the above-mentioned problems,under the mode of metal doping in the framework of silica synthesized by the dissolution-regrowth process of silicon dioxide,designed different types of metal-doped mesoporous silica with controllable metal doping,distribution state,valence state ratio and multiple components,and studied the relationship between the different structure of the metal doped mesoporous silica with their adsorption and catalysis performance.Our work will promote the application of silica-based composite materials in adsorption and catalysis in the future.The main work is summarized as follows:1.A newly magnesium-doped silica hollow spheres（Mg-SHSs）with highly homogeneous distribution of the Mg component in the silica framework was firstly developed by using a dissolution-regeneration process of silicon oxide.The shell densities and porous features of Mg-SHSs were shown to be varied obviously by different Mg amounts.The high specific surface area,suitable pore size and surface charge of Mg-SHSs provide the possibility for their high adsorption performance.For the removal of dyes,the Mg-SHSs showed the maximum adsorption capacity to MB is 367 mg·g^-1.Furthermore,the structure of Mg-SHSs is also stable and effective for repeated removal of dyes after the recovery and regeneration.2.A newly iron-doped silica hollow composite materials（Fe-SHSs）with the characteristics of controllable loading,high dispersion,stable fixation,and easy contact was studied.The study showed that the existence form of metals in Fe-SHSs composite material is closely related to its metal content.When used the Fe-SHSs as the catalyst for the Fenton reaction（degradation of Acid orange 7）,they exhibit excellent catalytic performance due to the sufficiently exposed active sites and open structure for easy access.3.A series of mixed-valence Fedoped silica hollow sphere nanozymes（FeOx-SHSs）were developed through controlled reduction at different temperatures under H₂/Ar.Making use of the homogeneous distribution and stable fixation of Fecomponents within the silica framework of the Fe-SHSs,the Fe²⁺/Fe³⁺ratio of FeOx-SHSs was successfully regulated within a wide range by increasing temperatures.Simultaneously,the oxidation of chromogenic peroxidase substrate TMB activities for FeOx-SHSs with different Fe²⁺/Fe³⁺ratios were compared,FeOx-SHSs-500 exhibits the highest catalytic activity due to its high Fe²⁺/Fe³⁺ratio,high specific surface area,and its hollow structure that is easily accessible to the substrate and fully exposes the active components.Considering the enhanced peroxidase-like activity of FeOx-SHSs,we utilized it further applied to construct a facile colorimetric biosensing system with GOx enzyme,which exhibited extreme sensitive determination on glucose.4.In order to further improve the activity of the single catalyst,newly bimetallic Fe-Co functionalized silica hollow spheres nanocomposites（Fe-Co-SHSs）by one-pot synthesis were prepared.Compared with their monometallic counterparts,the as-prepared Fe-Co-SHSs possess remarkably enhanced peroxidase-like activity by catalytically oxidize the TMB substrate to produce a typical color reaction for the synergistic effects between the Fespecies and Co species.Taking advantage of the distinguished peroxidase-like activity of Fe-Co-SHSs nanocomposites,a simple colorimetric approach for the determination of H₂O₂ from 10μM to 250μM with the detection limit was 4.30μM was obtained.5.In order to solve the problems of reducing the catalytic activity of the gold-based composite material and limiting the display of its catalytic activities due to the coverage of surfactants,the gold nanoparticles supported on iron doped silica hollow spheres（Au/Fe-SHSs）were designed.Benefitting from the uniform distribution of gold nanoparticles and the high exposure on the surface without wrapped by surfactants,the catalytic activity of the Au/Fe-SHSs composite material can exhibit peroxidase-like activity and glucose oxidase-like activity.Due to the multifunctional catalytic activity of Au/Fe-SHSs nanomaterials,the cascade reaction can be used to detect glucose quickly and conveniently without changing the reaction conditions.