The Synthesis And Characterization Of Mesoporous Silica And Mesoporous Silica Coated Gold Nanorods

Gold nanorods (AuNRs) for their unique longitudinal surface plasmon resonance(LSPR) and fluorescence characteristic, have wide application prospect in thebiomedical. However, a relatively low specific surface area and clustering within cellsalso restrict their widespread application. In addition, the seed-mediated method limitstheir biomedicinal application, for the surfactant cetyltrimethylammonium bromide(CTAB) is biologically hazardous with a poor bio-compatibility profle. It is crucial tosearch an easy and effective method to overcome their deficiencies and exploit thepotentiality application.Mesoporous silica (MS) for their unique pore structure, high surface area,favorable stability and biocompatibility have shown great perspective as catalysts,adsorbents, nanoreactors or drug carriers. Chiral mesoporous silica (CMS) as a specialform of MS have some novel characteristics, such as chiral pores and their shapeselectivity and enantioselectivity. CMS coating on the surface of AuNRs can protectAuNRs from clustering and enhance the biocompatibility and biosecurity of AuNRs,but also introduce some chirality properties of CMS, which will broaden itsapplication fields.In this thesis, we fabricated various morphological mesoporous silica includingchiral spiral mesoporous silica, and first used helically chiral mesoporous silicacoating on AuNRs surface for the synthesis of a series core-shell nanoparticles. Thespecific studies are as follows:We explored the stirring rate on the morphology of mesoporous silica and firstfabricated mesoporous silica with rod-shaped morphology by a template method. Atthe same time, it studied by transmission electron microscopy (TEM) and X-raydiffraction (XRD). The result show that the larger-sized rod-shaped (or helically chiral rod) mesoporous silica were obtained at the stirring rate of200rpm and the smallerspherical mesoporous silica were fabricated at the stirring rate of1000rpm. Inaddition, the products were featured of regular shape, high purity and gooddispersibility.Varying the molar ratio of acid to surfactant or the proportion of ethanol,mesoporous silica with tunable shape, pore architecture and crystallinity weresuccessfully coated on gold nanorods by a template method based on theself-assembly of anionic surfactants with inorganic precursors. At the same time,Scanning electron microscopy (SEM), transmission electron microscopy (TEM),X-ray diffraction (XRD) and N2adsorption-desorption isotherms were employed tocharacterize the synthesized AuNR@MS composites at different conditions. Theresults show that varying the molar ratio of acid to surfactant resulted in products withdifferent shapes, ranging from hollow tube to helical mesoporous tube, and eventuallyto polyhedron structure for the matching charge density changed in the interface ofsurfactant C14-L-AlaS and co-structure directing agent. A phase transformation of themesoporous silica shell from2D hexagonal to3D cubic occurred due to an increase ofacid/surfactant ratio. Meanwhile, the hydrolysis rate and micelle morphology arerelated to the content of alcohol. Mesoporous silica with various morphology coatedAuNRs were obtanined while increasing the proportion of ethanol. As the volumeratios of ethanol/water increased, the2D hexagonal MS structural graduallydisappeared, in which process the morphology from helical tube to sphere withregular arrangement of mesoporous decreased. And as the ethanol exceeds a certainamount, the AuNRs clustering and aggregating, for the weaken dielectric shield (thedielectric shield effect of ethanol is smaller than water), resulting that the aggregatingAuNRs were coated by one mesoporous silica.