Fluorescent Porous Silica Microspheres for Highly and Selectively Detecting Hg2+ and Pb2+ Ions and Imaging in Living Cells

In this work, SiO 2 microspheres were first prepared by a conventional Stöber method and then etched by NaOH solution to obtain porous ones. By tuning the degree of etching, specific surface area of SiO 2 microspheres could be controlled. Then, small fluorescent molecules are synthesized and incorporated onto the surface and/or pores of the SiO 2 via layer-by-layer reaction to obtain fluorescent microspheres, namely, SiO 2 -NH 2 -BODIPY (SiNBB), SiO 2 -NH 2 -BODIPY-indole-benzothiazole (SiNBIT), and SiO 2 -NH 2 -BODIPY-indole-benzoxazole (SiNBIO). The as-prepared microspheres SiNBB exhibit highly sensitive and selective recognition ability for Hg 2+ and Pb 2+ . When SiNBB encounters Hg 2+ and Pb 2+ , the fluorescence intensity of SiNBB is increased up to fivefold. SiNBIT and SiNBIO are solely sensitive to Hg 2+ , and both have a single high sensitivity to recognize Hg 2+ . The adsorption efficiency of Hg 2+ by the three fluorescent microspheres SiNBB, SiNBIT, and SiNBIO reached 2.91, 0.99, and 0.98 g/g of microspheres, respectively. Experimental results of A549 cells and zebrafish indicate that the fluorescent microspheres are permeable to cell membranes and organisms. The distribution of Hg 2+ in the brain of zebrafish was obtained by the fluorescence confocal imaging technique, and Hg 2+ was successfully detected in A549 cells and zebrafish.