Improved sensitivity of rhodamine 6G luminiscence chemodosimeter for Hg2+ quantification in aqueous matrices based on Au nanoparticles

A. MUÑOZ DE LA PEÑA; M.C. ONAINDIA; R. BRASCA; H. GOICOECHEA; M.J. CULZONI

Rodas

Simposio; VI International Symposium on Luminiscence Spectrometry; 2014

Monitoring mercury levels in the aquatic ecosystem is important because it is a potential source of contamination even at low concentrations. On the basis of the maximum Hg2+ level (2 ng mL-1) permitted in drinking water by the United States Environmental Protection Agency (EPA), an ideal probe should display a very low detection limit and a high selectivity towards Hg2+. Considerable attention has been focused on the design of luminescence chemodosimeters for Hg2+ due to the highly sensitivity, quickness, and nondestructive advantages of luminescence methods. The chemodosimeter strategy is based on the use of a selective reaction that is induced by the target species and lead to an observable luminescence signal (preferably off-on). Rhodamine and BODIPY derivatives are two families of small molecular probes reported for selective Hg2+ detection. The purpose of this work is to enhance the sensitivity of the reaction of a Rhodamine 6G derivative (FC1) towards Hg2+ by incorporating the probe into Au nanoparticles (AuNps). FC1 and AuNps were synthesized according to [4] and [5], respectively. Fluorescence measurements were carried out exciting at 515 nm and measuring the emission at 555 nm. In the presence of AuNps, the emission intensity of FC1 is highly decreased due to an intense resonance energy transfer (RET) effect. This fact helps improve the sensitivity of the reaction towards Hg2+, and allows quantitating Hg2+ concentrations below 2 ng mL?1. The chemodosimeter has been fully characterized and applied to the determination of traces of Hg2+ in different aqueous samples. The proposed method allows the accurate determination of Hg2+ in aqueous samples in the interval between 0.5 and 4 ng mL?1, being 4 times more sensitive than the original method in absence of AuNps.