Synthesis of double gold nanoclusters/graphene oxide and its application as a new fluorescence probe for Hg2+ detection with greatly enhanced sensitivity and rapidity

Gold nanoclusters possess outstanding physical and chemical attributes that make them excellent scaffolds for construction of chemical and biological sensors. The paper reported synthesis of double gold nanoclusters/graphene oxide (D-GNCs/GO) and its application as a new fluorescence probe for Hg2+ detection. In the study, the amine group was introduced into GO sheets through the EDC/NHS mediated reaction to form positively charged GO sheets (GO-NH3+). After GNC@Lys was mixed with GNC@BSA to form negatively charged D-GNCs, the D-GNCs was assembled on the surface of GO-NH3+ with electrostatic interaction. The study demonstrated that the interaction between GNC@Lys and GNC@BSA increases fluorescence intensity of the GNC@BSA and leads to more sensitive fluorescence response towards Hg2+, for which the sensitivity is more than 3-fold that of single GNC@BSA. The interaction between GO and GNCs accelerates the reaction of D-GNCs/GO with Hg2+, for which the reaction rate is more than 3-fold that of single D-GNCs. Owing to prominent synergistic effects between GNC@Lys, GNC@BSA and GO, the nanosensor based on the D-GNCs/GO displays a surprisingly enhanced sensitivity and rapidity for Hg2+ detection. The fluorescence peak intensity linearly decreases with increasing Hg2+ concentration in the range of 1.0 x 10(-5) to 5.0 x 10(-13) M with a detection limit of 1.8 x 10(-13) M (S/N = 3). The analytical method presents an obvious advantage of sensitivity, rapidity and repeatability when compared with present Hg2+ optical sensors. It has been successfully applied to detection of Hg2+ in water samples. The study also opens a new avenue for fabrication of fluorescent hybrids, which holds great potential applications in sensing, spectral encoding, bioimaging and catalysis.