Dendritic Fibrous Nanosilica-Based Inorganic–Organic Composite Fluorescent Probes for the Detection and Removal of Pb²⁺ and Hg⁺ Ions

Dendritic fibrous nanomaterials play an important role in the adsorption of heavy metals. The introduction of fluorescent groups on the dendritic fibrous nanosilica (DFNS) will endow it with the ability to recognize and adsorb heavy metals. In this work, DFNS was first prepared as starting materials. Then, it was chemically modified with vinyltriethoxysilane (VTES) to make its surface rich in C═C double bonds. At the same time, the RAFT reagent (Br-CTA-CH═CH2) containing -Br and C═C double bond was synthesized. In addition, fluorescent monomers Naph-CH═CH2 and BT-CH═CH2 were synthesized by introducing C═C double bonds on naphthalimide and benzothiazole, respectively. Then, Naph-CH═CH2, BT-CH═CH2, and Br-CTA-CH═CH2 were subjected to RAFT polymerization to obtain fluorescent hyperbranched polymers (FL-HBPs) containing Br groups. Finally, FL-HBPs were loaded onto the surface of CH2═CH-DFNS by Heck reaction to obtain organic–inorganic composite microspheres (FL-HBP-DFNS). The microspheres can sensitively identify and efficiently separate Pb2+/Hg+. The probe exhibits fluorescence enhancement of the Pb2+/Hg+ ions. The limit of detection (LOD) reaches 1.04 nM and 2.46 nM, respectively. Moreover, the adsorption efficiency of Pb2+ reaches 99.7%, and the adsorption capacity is 157.5 mg/g. Therefore, FL-HBP-DFNS can play effective roles in the identification and removal of heavy metals.