Surface adsorption of hydroxyanthraquinones on CTAB-modified gold nanosurfaces

Gold nanosurfaces are widely applied to the surface-enhanced Raman spectroscopy (SERS) detection of the biological systems. The surface modification of gold nanoparticles (AuNPs) is often required when the analytes do not efficiently adsorb on the surface. In this paper, an aggregation of AuNPs with cetyltrimethylammonium bromide (CTAB) was introduced for the efficient surface adsorption and strong SERS enhancement for a number of hydroxyanthraquinones (HAQs). The SERS of HAQs including 1,2-dihydroxyanthraquinone (alizarin) were strongly enhanced with CTAB-modified AuNPs and deprotonation of alizarin was clearly observed upon the pH change. The CTAB-modified AuNPs are regarded as efficient SERS substrates for many biological molecules with weak surface adsorption.