Recent developments on nanomaterials-based optical sensors for Hg2+ detection

Mercuric ion (Hg2+), released from both natural and industrial sources, has severe adverse effects on human health and the environment even at very low concentrations. It is very important to develop a rapid and economical method for the detection of Hg2+ with high sensitivity and selectivity. Nanomaterials with unique size and shape-dependent optical properties are attractive sensing materials. The application of nanomaterials to design optical sensors for Hg2+ provides a powerful method for the trace detection of Hg2+ in the environment, because these optical sensors are simple, rapidly responsive, cost-effective and highly sensitive. This review summarizes the recent advances on the development of optical assays for Hg2+ in aqueous solution by using functionalized nanomaterials (including noble metal nanoparticles, fluorescent metal nanoclusters, semiconductor quantum dots and carbon nanodots). Detection strategies based on the Hg2+-induced changes in spectral absorbance, fluorescence intensity and surface-enhanced Raman scattering signals were described. And the design principles for each optical assay were presented. In addition, the future challenge and the prospect of the development of nanomaterial optical sensors for Hg2+ detection were also discussed.