▎ 摘　　要

An electrostatically controlled fluorometric assay is described that is based on the use of silver/copper bimetallic nanoclusters. The nanoclusters were coated with polyethyleneimine (PEI-Ag/CuNCs). At pH7.4, these particles are positively charged. Their blue fluorescence (with excitation/emission peaks at 341/464nm) depends on local pH values and temperature. If graphene oxide (which is negatively charged at pH7.4) is introduced, the fluorescence of the PEI-Ag/CuNCs is quenched. Based on various electrostatic interactions, three kinds of biomacromolecules were detected by fluorometry. These include (negatively charged) heparin, (positively charged) protamine, and (virtually uncharged) trypsin. Heparin is detected by using GO/PEI-Ag/CuNCs, protamine by using GO/heparin/PEI-Ag/CuNCs, and trypsin by using GO/protamine/heparin/PEI-Ag/CuNC. The detection limits and linear ranges are 4.8nM and 10-450nM for heparin, 0.09gmL(-1) and 0.25-5gmL(-1) for protamine, and 0.03gmL(-1) and 0.05-1gmL(-1) for trypsin. Zeta potentials of the various substances in the system were determined to elucidate the detection mechanism. Comceivably, the method provides a widely applicable approach for electrostatically controlled biomolecular assays.