A turn-on fluorescent probe for Hg2+ detection by using gold nanoparticle-based hybrid microgels

Hybrid microgels with Au nanoparticles (AuNPs) immobilized in poly(N-isopropylacrylamideco-2-(dimethylamino)ethylmethacrylate) (P(NIPAM-co-DMA)) microgels have been prepared. The as-synthesized hybrid microgels showed excellent thermo- and pH-responsive properties and high stabilities. 1-pyrenebutyric acid (PBA) molecules were then adsorbed on the AuNP surfaces via electrostatic interactions to form PBA-AuNPs/P(NIPAM-co-DMA) composites that were used as probes for the detection of Hg2+. The fluorescence of PBA was effectively quenched through fluorescence resonance energy transfer between AuNPs and PBA molecules. However, the addition of Hg2+ ions caused the fluorescence turn-on dramatically and 16 times fluorescence enhancement was obtained, which is attributed the fact that Hg2+ ions replace the adsorbed PBA molecules.