title: Biphasic synthesis of Au@SiO2 core-shell particles with stepwise ligand exchange.
abstract: We report the synthesis of well-dispersed core-shell Au@SiO(2) nanoparticles with minimal extraneous silica particle growth. Agglomeration was suppressed through consecutive exchange of the stabilizing ligands on the gold cores from citrate to L-arginine and finally (3-mercaptopropyl)triethoxysilane. The result was a vitreophilic, stable gold suspension that could be coated with silica in a biphasic mixture through controlled hydrolysis of tetraethoxysilane under L-arginine catalysis. Unwanted condensation of silica particles without gold cores was limited by slowing the transfer across the liquid-liquid interface and reducing the concentration of the L-arginine catalyst. In-situ dynamic light scattering and optical transmission spectroscopy revealed the growth and dispersion states during synthesis. The resulting core-shell particles were characterized via dynamic light scattering, optical spectroscopy, and electron microscopy. Their cores were typically 19 nm in diameter, with a narrow size distribution, and could be coated with a silica shell in multiple steps to yield core-shell particles with diameters up to 40 nm. The approach was sufficiently controllable to allow us to target a shell thickness by choosing appropriate precursor concentrations.
authors.affiliation: Leibniz Institute for New Materials, Structure Formation group and Nano Cell Interaction group, Campus D2 2, 66123 Saarbruecken, Germany.
authors.forename: Mathias
authors.initials: M
authors.lastname: Schulzendorf
authors.forename: Christian
authors.initials: C
authors.lastname: Cavelius
authors.forename: Philip
authors.initials: P
authors.lastname: Born
authors.forename: Eoin
authors.initials: E
authors.lastname: Murray
authors.forename: Tobias
authors.initials: T
authors.lastname: Kraus
mesh_terms: D006046:Gold / Q000737:chemistry*; D008024:Ligands; D053758:Nanoparticles / Q000737:chemistry; D010316:Particle Size; D012822:Silicon Dioxide / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D008024:Ligands; D006046:Gold; D012822:Silicon Dioxide