A novel ratiometric fluorescence probe based on BSA assembled silver nanoclusters for mercuric ion selective sensing

A novel ratiometric fluorescence probe based on protein–silver nanoclusters (NCs) for mercuric ion (Hg2+) has been synthesized and characterized. A facile and simple one-step method for the synthesis of fluorescent Ag NCs, using bovine serum albumin (BSA) without preprocessing as a scaffold was developed. BSA assembled Ag NC (BSA-Ag NCs) were first found to exhibit ratiometric fluorescence with blue emission at 480 nm and red emission at 634 nm. Upon the addition of Hg2+, the emission of BSA-Ag NCs at 480 nm gradually increased and at 634 nm steadily decreased. The presence of Hg2+ induced a color change from light yellow to colorless and a bright red fluorescence to blue fluorescence. The determination of Hg2+ based on ratiometric fluorescence was developed. The linear dynamic range was from 5.0 × 10−8 M to 2.5 × 10−5 M with a detection limit of 4.87 × 10−8 M. The relative standard deviation (RSD) at 0.30 μM for Hg2+ of six replicates determination was 2.8%. The BSA-Ag NCs were conveniently and easily synthesized, so could serve as a “naked-eye” fluorescent probe for Hg2+. The probe may be a good candidate for the application of sensing Hg2+ in environmental analysis and fluorescence imaging.