One-pot approach to modify nanostructured gold surfaces through in situ dithiocarbamate linkages

This work describes a simple methodology to bio-functionalize flat Au(1 1 1) electrodes through the one-step reaction between gold nanoparticles (AuNPs), carbon disulfide and a secondary amine (epinephrine) and an aminoacid (tryptophan). The process relies on the in situ dithiocarbamate formation between carbon disulphide and amine groups and also on the strong linkage between sulfur and gold. The redox behavior of modified gold with epinephrine or tryptophan, prepared from both ethanolic and aqueous solutions confirms their covalent immobilization and reveals a significant increase of their amount on the electrode due to the presence of AuNPs. Electrochemical reductive desorption in basic solution provided qualitative information on the amount of sulfur linked the gold surface and complements the redox studies. The co-immobilization of an enzyme (glucose oxidase, GOx) and gold nanoparticles, using carbon disulfide has been also tested. The presence of GOx on modified Au(1 1 1) electrodes has been confirmed by electrochemical detection of the catalytic oxidation of glucose in the presence of a redox mediator and through the evaluation of H2O2 reduction, formed during the catalytic reaction. XPS analysis, topographic and phase imaging by atomic force microscopy (AFM) further confirmed surface modification by AuNPs and also their functionalization. The successful one-step amine adsorption, in the presence of AuNPs, from aqueous solutions reveals the potential of this method in the construction of nanostructured biosensing interfaces.