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

A novel and efficient approach has been established for the synthesis of silver nanoclusters capped silica nanoparticles (SiO@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 S 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 S), while that of luminescent silica nanoparticles was hardly affected. The PL emission intensity ratio of AgNCs and the luminescent silica nanoparticles was defined as I/I. A good linear relationship between the I/I value and the concentration of I (or S) was observed, and the limit of detection (LOD) was estimated to be 57 nM for I and 62 nM for S. In addition, the fluorescence images of the SiO@AgNCs nanosensor changed from white to orange upon exposure to different concentrations of I (or S) (0-250 μM), which could be clearly distinguished by the naked eye. The SiO@AgNCs nanosensor exhibited good selectivity against other analytes, and I or S ions could be separately detected via the introduction of proper masking agents. Furthermore, the detection of I and S in real water samples was also demonstrated.