Preparation And Application Of Noble Metal Nanoparticles Covered By Mesoporous Silica

Noble Metal Nanomaterials,for example,gold and silver nanomaterials have unique catalytic activity and optical properties.In this paper,Au,Ag,Au@Ag core-shell nanoparticles and silica-coated noble metal nanoparticles and other materials were prepared using chiral cysteine?Cys?biomolecules as chiral modifier by liquid phase chemical reduction method and St?ber method.Using the prepared Ag@mSiO₂ and Au@Ag@mSiO₂with yolk-shell structure as probes,the configuration of cysteine was identified by circular dichroism chromatography.The established detection method can be further expanded,and the detection of divalent copper ions can be realized.Using the prepared Au@s Si O₂ with yolk-shell structure as catalysts,the catalytic reduction of rhodamine B was achieved,and the new catalyst showed relatively high catalytic activities and stability.Ag nanoparticles?Ag NPs?were prepared by liquid phase chemical reduction using silver nitrate as precursor and sodium borohydride as reducing agent.In order to maintain the stability of the silver nanoparticles,a layer of mesoporous silica was coated on the surface of the silver nanoparticles by the sol-gel method.Yolk-shell structured Ag@mSiO₂was prepared by oxidative etching reaction.Using Ag@mSiO₂ as probes,the configurations of cysteine and the concentrations of cysteine were detected by circular dichroism spectra.The L-cysteine and D-cysteine-modified probes show mirror symmetrical chiral signals in the region of 220-350 nm.The study found that the concentrations of L-cysteine and D-cysteine are linearly related to the intensities of CD signal within a certain concentration range,so that the concentrations of L-cysteine and D-cysteine can be detected.Using AgNO₃ and HAuCl₄ as precursors,and sodium citrate as reducing agent and stabilizer,Au@Ag nanoparticles with core-shell structure were prepared by liquid phase chemical reduction method.Yolk-shell structured YS-Au@Ag@mSiO₂composite particles were synthesized by coating a layer of mesoporous silica on the surface of Au@Ag and after partial removal of Ag shell.The synthesized YS-Au@Ag@mSiO₂ was used as probes to detect L/D-Cys enantiomers and Cu²⁺.There is a good linear relationship between the concentration of L/D-Cys and the CD signal generated.The detection principle for divalent copper ions is based on the ability of Cu²⁺to catalyze the oxidation of L-Cys to cystine.Due to the change in the concentration of L-Cys,the CD signal is changed.The detection of copper ion can be achieved by monitoring the change of CD signal.Core-shell structured mSiO₂@Au@s Si O₂ particles were synthesized after loading gold seeds and coating solid silica loaded on mesoporous cubic silica.Yolk-shell structured YS-Au@s Si O₂ was prepared by etching the cubic silica core.YS-Au@s Si O₂ was used as catalyst to reduce rhodamine B in the presence of sodium borohydride.Due to the protective effect of the silica shell,the gold nanoparticles can be stably dispersed in the aqueous solution,guaranteeing the stability and reliability of the catalytic reduction experiment.The results showed that the prepared YS-Au@s Si O₂ had high catalytic activities.Kinetic studies found that the catalytic reduction reaction conforms to first-order kinetic characteristics,and the rate constant of the reaction k is 8.89×10^-3 s^-1.