Aggregation-induced emission enhancement of adenosine monophosphate-capped bimetallic nanoclusters by aluminum(III) ions, and its application to the fluorometric determination of cysteine.

Abstract

The fluorescence of adenosine monophosphate-capped bimetallic gold and silver nanoclusters (type AuAgNC@AMP) is strongly enhanced and blue shifted in the presence of Al(III). As confirmed by transmission electron microscopy, the AuAgNC nanodots are converted to larger assembled spheres of type AuAgNC-Al(III). The fluorescence enhancement is attributed to aggregation-induced emission enhancement (AIEE). The fluorescence of the AuAgNC-Al(III) assembly(with excitation and emission maxima at 340 and 540nm) is quenched by cysteine (Cys). The effect was applied to the fluorometric determination of Cys. The assay works in the 1.0 to 16.0μM Cys concentration range and has a 50nM limit of detection. The method was successfully applied to analyze Cys-spiked mineral waters and serum. The quenching mechanism is explored in depth. It is attributed to the partial replacement of AMP by Cys at the surface of the AuAgNC and alteration of the assembly structure from large spherical particles to a strip shape. Graphical abstractSchematic representation of the fluorescence enhancement of bimetallic nanoclusters capped withadenosine monophosphate by using Al(III), and its application in selective and sensitive determination of cysteine via ligand replacement and reassembly.