Preparation of Functional Silane-Stabilized Gold Colloids in the (Sub)nanometer Size Range

Abstract

A synthesis method is introduced for very small uniform gold particles (diameter less than 5 nm), based on the reduction of hydrogen tetrachloroaurate(III) in ethanol in the presence of (γ-mercaptopropyl)trimethoxysilane (MPS). The surface layer of MPS molecules gives the gold particles a high colloidal stability and allows in principle further reaction with any silane coupling agent. Decrease of the HAuCl4:MPS ratio allows a controlled reduction of gold particle size, resulting in remarkably uniform gold clusters of (sub)nanometer size, observed with high-angle-annular-dark-field scanning transmission electron microscopy. After attachment of (γ-aminopropyl)triethoxysilane (APS) to the MPS surface layer, other molecules may be covalently bound to the gold colloid via the amine group of APS. As an illustrative example we prepared in this manner gold particles labeled with a fluorescent dye. The chemical structure of the surface silanes was studied with Fourier transform infrared spectroscopy.

Continuous flow synthesis of ultrasmall gold nanoparticles in a microreactor using trisodium citrate and their SERS performance

“…A colourless product which did not exhibit a Localized Surface Plasmon Resonance (LSPR) band was obtained, indicating gold nanoparticles with diameter below 3 nm (Buining et al, 1997). The TEM image shown in Fig.…”

Surface modification, functionalization and bioconjugation of colloidal inorganic nanoparticles

“…Then, using this first layer, a polymeric, crosslinked inorganic silica shell is deposited on the particles, which can be further derivatized. Nanoparticles of different materials (Mulvaney et al 2000;Graf et al 2003;Jana et al 2007), in particular noble metals (Au, Liz-Marzán et al 1996;Buining et al 1997;Ag, Hardikar & Matijevic 2000;Han et al 2008), fluorescent quantum dots (CdSe/ZnS, Gerion et al 2001;Nann & Mulvaney 2004;Darbandi et al 2005), phosphorescent (Ehlert et al 2008) and magnetic nanoparticles (e.g. Fe, Ohmori & Matijevic 1993;Co, Kobayashi et al 2003; CoFe 2 O 4 , Wagner et al 2002) and particles of different shapes have been coated with silica shells.…”

“…by ligand exchange. Silica coating, however, seems to yield very robust nanoparticles functionalized with primary amines (Buining et al 1997;Li et al 2007). …”

New Frontiers in Gold Labeling

“…In addition to phosphine-stabilized gold particles, ligands bound to the gold core via a sulfur donor are also stable and may prove useful (Brust et al 1994;Buining et al 1997;Chen and Kimura 1999). An Ni-NTA cluster that binds 6x-His tags was prepared this way using a thiol-containing dipeptide (Hainfeld et al 1999c).…”