Preparation Of Gold Nanoparticles By Using APTES As Ligand

Gold nanoparticles are expected to be potential useful in the fields of surface-enhanced Raman scattering（SERS）,catalysis,photothermal conversion,biolabeling,etc.due to their unique physicochemical properties.Many different approaches,including aqueous-phase and oil-phase pathways,have been developed for preparation of gold nanoparticles.In all the approaches,choice of ligands is vital important in preparation of the gold nanoparticles.In this thesis,3-aminopropyltriethoxysilane（APTES）was employed as the ligand to prepare gold nanoparticles.A series of gold nanoparticles with different size and morphology were prepared successfully by changing the molar ratio of APTES/HAu Cl₄,the solvent and the prehydrolysis of APTES.In addition,the interactions between APTES and HAu Cl₄ were explored and the SERS,catalysis,and photothermal performances of the resulting gold nanoparticles were evaluated.The main results include:1.In ethanol solution,APTES existed primarily in monomer form.On one hand,the interactions between APTES and HAu Cl₄ resulted in the formation of gold precursor with lowered activity.On the other hand,adsorption of the APTES monomers on high energy planes of face-centered cubic（fcc）gold directed the preferential growth of gold nanoparticles along（111）plane,contributing to the formation of gold nanoparticles with rough surface.Due to the formation of APTES protection layer on the particle surface,the resulting gold nanoparticles presented good stability and peroxidase-like activity,making them qualified as dual colorimetric and SERS probe for detection of cysteine molecules.2.When being dispersed in aqueous solution,APTES underwent self-catalyzed hydrolysis/condensation,resulting in the formation of APTES oligomers.Compared to the monomers,APTES oligomers were more effective to direct the preferential growth of gold nanoparticles along the（111）plane of fcc gold due to its strong affinity to the high energy facets,contributing to the formation of gold nanoparticles flower-like in shape.These gold nanoflowers presented good SERS and catalytic activity,allowing them as probe to monitor the dimerization reaction of p-aminothiophenol in-situ.3.In aqueous medium,APTES could not be well dispersed when its concentration was high.Interactions between Au³⁺ions and APTES on surface of the oil droplets were profitable to stabilize the oil droplets and promote the formation of oil/water emulsion vesicles.Due to high p H value of the solution,APTES on the oil droplet surface underwent self-catalyzed hydrolysis/condensation,resulting in the formation of Au³⁺cross-linked hollow organosilica particles.In presence of glutathione,the hollow particles may degrade slowly,allowing controlled release of the loaded drug.After heating,reduction of Au³⁺ions allowed the formation of gold nanoparticles.Attributed to the supporting effect of the hollow organosilica framework,the gold nanoparticles were qualified as heterogeneous circulated catalyst to catalyze the reduction reaction of p-nitroaniline.4.In aqueous solution,when the concentration of APTES was low,interactions between Au³⁺ions and APTES were also effective to stabilize the oil/water vesicles of APTES.No hollow organosilica particles were observable due to low p H of the solution and low hydrolysis/condensation efficiency of the APTES on the oil droplet surface.However,the addition of reductant resulted in the formation of hollow gold nanoflowers with good SERS,catalysis and photothermal performances.