Silver nanoclusters capped silica nanoparticles as a ratiometric photoluminescence nanosensor for the selective detection of I- and S2.

A novel and efficient approach has been established for the synthesis of silver nanoclusters capped silica nanoparticles (SiO2@AgNCs). These nanoclusters (AgNCs) capped silica nanoparticles were utilized as a novel ratiometric photoluminescence (PL) nanosensor for extremely sensitive and selective detection of I- and S2- ions. The AgNCs were prepared in situ on the silica nanoparticles through polyethyleneimine (PEI) template approach. While dual PL emissions of AgNCs (at 500 nm) and luminescent silica nanoparticles (at 602 nm) formed the basis for the ratiometric sensing. The PL emission of AgNCs was strongly quenched by I- (or S2-), while that of luminescent silica nanoparticles was hardly affected. The PL emission intensity ratio of AgNCs and the luminescent silica nanoparticles was defined as I500/I602. A good linear relationship between the I500/I602 value and the concentration of I- (or S2-) was observed, and the limit of detection (LOD) was estimated to be 57 nM for I- and 62 nM for S2-. In addition, the fluorescence images of the SiO2@AgNCs nanosensor changed from white to orange upon exposure to different concentrations of I- (or S2-) (0-250 μM), which could be clearly distinguished by the naked eye. The SiO2@AgNCs nanosensor exhibited good selectivity against other analytes, and I- or S2- ions could be separately detected via the introduction of proper masking agents. Furthermore, the detection of I- and S2- in real water samples was also demonstrated.