Sensitive detection of cyanide using bovine serum albumin-stabilized cerium/gold nanoclusters

A simple, sensitive, and selective fluorescence assay for the detection of CN^- has been demonstrated using bovine serum albumin-stabilized cerium/gold nanoclusters (BSA-Ce/Au NCs). When excited at 325 nm, BSA-Ce/Au NCs have two fluorescence bands centered at 410 and 658 nm, which are assigned to BSA-Ce/Au complexes and Au NCs, respectively. Each BSA-Ce/Au NC contains 22 Au atoms and 8 Ce ions. Through etching of the Au core in BSA-Ce/Au NCs by CN^-, the fluorescence at 658 nm is quenched, while that at 410 nm enhances during the formation of complexes among BSA, Ce⁴⁺, and [Au(CN)₂]^-. The circular dichroism spectra reveal that relative to BSA-Au NCs, BSA-Ce/Au NCs have looser structures of the BSA templates. As a result, it is easier for CN^- to access the Au cores in BSA-Ce/Au NCs, allowing faster (within 15 min) etching of the Au cores by CN^-. At pH 12.0, this assay allows the detection of CN^- down to 50 nM, with linearity over 0.1-15 μM. This assay has been applied to the determination of the concentrations of CN^- in spiked drinking water and pond water samples.