title: Synthesis, characterization of dihydrolipoic acid capped gold nanoparticles, and functionalization by the electroluminescent luminol.
abstract: The use of gold nanoparticles as biological probes requires the improvement of colloidal stability. Dihydrolipoic acid (DHLA), a dithiol obtained by the reduction of thioctic acid, appears therefore very attractive for the stabilization and the further functionalization of gold nanoparticles because DHLA is characterized by a carboxylic acid group and two thiol functions. The ionizable carboxylic acid groups ensure, for pH > or = 8, the water solubility of DHLA-capped gold (Au@DHLA) nanoparticles, prepared by the Brust protocol, and the stability of the resulting colloid by electrostatic repulsions. Moreover almost all DHLA, adsorbed onto gold, adopts a conformation allowing their immobilization by both sulfur ends. It is proved by sulfur K-edge X-ray absorption near edge structure spectroscopy, which appears as an appropriate tool for determining the chemical form of sulfur atoms present in the organic monolayer. Such a grafting renders the DHLA monolayers more resistant to displacement by dithiothreitol than mercaptoundecanoic acid monolayers. The presence of DHLA on gold particles allows their functionalization by the electroluminescent luminol through amine coupling reactions assisted by 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide. As a luminol-functionalized particle is nine times as bright as a single luminol molecule, the use of the particles as a biological probe with a lower threshold of detection is envisaged.
authors.affiliation: Laboratoire de Physico-Chimie des Matériaux Luminescents, UMR CNRS 5620, Université Claude Bernard Lyon 1, Domaine Scientifique de la Doua, 69622 Villeurbanne Cedex, France. roux@pcml.univ-lyon1.fr
authors.forename: Stéphane
authors.initials: S
authors.lastname: Roux
authors.forename: Bruno
authors.initials: B
authors.lastname: Garcia
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Bridot
authors.forename: Murielle
authors.initials: M
authors.lastname: Salomé
authors.forename: Christophe
authors.initials: C
authors.lastname: Marquette
authors.forename: Laurence
authors.initials: L
authors.lastname: Lemelle
authors.forename: Phillipe
authors.initials: P
authors.lastname: Gillet
authors.forename: Loïc
authors.initials: L
authors.lastname: Blum
authors.forename: Pascal
authors.initials: P
authors.lastname: Perriat
authors.forename: Olivier
authors.initials: O
authors.lastname: Tillement