One-pot synthesis of bovine serum albumin protected gold/silver bimetallic nanoclusters for ratiometric and visual detection of mercury

A novel, rapid and ultrasensitive ratiometric and colorimetric fluorescence method was developed using bovine serum albumin protected gold/silver bimetallic nanoclusters (BSA-Au/Ag NCs) as fluorescent sensor for mercury (Hg) detection. The fluorescence sensor which was synthesized by one-pot approach shows dual-emissions at 470 nm (Ag NCs) and 630 nm (Au NCs) under a single excitation at 390 nm. In the presence of Hg2+, the red fluorescence of Au NCs was quenched while the fluorescence of Ag NCs almost unchanged, which exhibited a ratiometric fluorescence response and an obvious fluorescence color change toward Hg2+. The selective quenching mechanism may be due to the formation of gold amalgam bonds between Hg2+ (4f145d10) and Au+ (4f145d10). A limit of detection (LOD) of 2.2 μg L−1 and a relative standard deviation (RSD, n = 7) of 0.7% at a concentration of 50 μg L−1 of Hg2+ were obtained when using a commercial fluorescence spectrophotometer as the detector. In visual detection, as low as 10 μg L−1 of Hg2+ can be easily discriminated from the blank with the naked eye. The proposed method retains several unique advantages, including simplicity, rapidity, ease of usage and high-sensitively.