Fluorescent Porous Silica Microspheres for Highly and Selectively Detecting Hg(2+) and Pb(2+) Ions and Imaging in Living Cells

[Image: see text] 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.