Fluorescent probe encapsulated hydrogel microsphere for selective and reversible detection of Hg²⁺

We developed a simple and sensitive hydrogel sensor in the form of microspheres by using fluorescence probe encapsulated within a hydrogel matrix for the detection of Hg²⁺. The traditional fluorescence probes suspended in solution are not transportable and recoverable. To overcome these disadvantages, we devised poly(ethylene glycol) diacrylate-based hydrogel microspheres in which fluorescence probe (R19S) was embedded at high density. The functionalized hydrogel microspheres were prepared by combining a microfluidic device with UV light. The hydrogel microspheres-based sensor exhibited good selectivity to Hg²⁺ among various metal ions and high sensitivity with a detection limit of 90 nM. Furthermore, after binding with Hg²⁺, the R19S encapsulated hydrogel microspheres can be separated from testing samples easily and treated with the solution containing KI to remove Hg²⁺ and realize reusable detection. The current work may offer a new method for Hg²⁺ recognition with a more efficient manner.