Selective chemiluminescent sensor for detection of mercury(II) ions using non-aggregated luminol-capped gold nanoparticles

A selective chemiluminescent sensor was developed for the detection of mercury(II) ions (Hg2+) in environmental water and soil supernatant samples using non-aggregated luminol-capped gold nanoparticles (AuNPs). Luminol-capped AuNPs can react with silver nitrate (AgNO3) under alkaline environment, generating a strong chemiluminescence (CL) emission because AuNPs had excellent catalytic activity for luminol-AgNO3 CL system. However, when Hg2+ was added to the solution of luminol-capped AuNPs, it would be adsorbed on the surface of luminol-capped AuNPs according to the inherent affinity of AuNPs for Hg2+. The presence of Hg2+ significantly inhibited the catalytic activity of AuNPs, leading to CL quenching. With the increasing of Hg2+ concentration, the CL intensity gradually decreased. Under the optimal detection conditions, the developed CL sensor showed a good linear relationship in range of 10-600 nM with a limit of detection of 1 nM at a signal-to-noise ratio of three which was below the maximum allowable concentration for Hg2+ in drinking water (10 nM) defined by United States Environmental Protection Agency. Also, the developed CL sensor exhibited high selectivity toward Hg2+ over other environmentally relevant metal ions at high concentrations (500 μM).