Dual-Emission Fluorescent Microspheres for the Detection of Biothiols and Hg(2+)

Dual-emission nanosensor for Hg(2+) detection was prepared by coupling CA-AEAPMS on the surface of RBS-doped modified silica microspheres. The CA-AEAPMS was synthesized by using N-(β-aminoethyl)-γ-aminopropyl methyldimethoxysilane (AEAPMS) and citric acid as the main raw material. The obtained nanosensor showed characteristic fluorescence emissions of Rhodamine B (red) and CA-AEAPMS (blue) under a single excitation wavelength (360 nm). Upon binding to Hg(2+), only the fluorescence of CA-AEAPMS was quenched, resulting in the ratiometric fluorescence response of the dual-emission silica microspheres. This ratiometric nanosensor exhibited good selectivity to Hg(2+) over other metal ions, because of the amide groups on the surface of CA-AEAPMS serving as the Hg(2+) recognition sites. The ratio of F(450)/F(580) linearly decreased with the increasing of Hg(2+) concentration in the range of 0 to 3 × 10(−6) M, and a detection limit was as low as 97 nM was achieved. Then, the addition of three thiol-containing amino acids (Cys, Hcy, GSH) to the quenched fluorescence solution with Hg(2+) can restore the fluorescence, and the detection limits of the three biothiols (Cys, Hcy, GSH) are 0.133 μM, 0.086 μM, and 0.123 μM, respectively.