Silica-based optical chemosensors for detection and removal of metal ions

Because some metal ions are highly toxic even at trace level, a constant demand of developing methods for monitoring and removing these metal ions is extremely urgent. Silica-based optical chemosensors are supposed as good alternatives to classical instrumental methods for detecting and adsorbing metal ions, due to their effect and lower price. Silica nanoparticles, silica gel and mesoporous silica are used as supporting platforms to fabricate optical chemosensors. They have certain properties containing high porosity and expectant adsorption capacity. Chromogenic-type and fluorogenic-type optical probes, such as azobenzene, naphthalimide and rhodamine, are grafted to the surface of silica-based materials by sol-gel reaction, the limit of detection, response time and selective properties of optical sensors are improved sequentially. In this paper, the articles of silica-based optical chemosensors are retrospected since 2008, describing silica-based optical sensors used for sensing metal ions. The sensing mechanism, optical phenomenon, detection limit, adsorption capacity and application are also reviewed.