Ultrastable Gold-Copper Nanoclusters on Nitrogen-Doped Graphene Quantum Dots for Selective Electrochemical and Fluorescence Sensing of Glycine

In this work, we present an ultrastable gold-coppernanoclusteron nitrogen-doped graphene quantum dot (AuCuNC@N-GQD), with a stabilityof >= 1 year, achieved through a galvanic exchange process, whichdisplayed intense solid- and solution-state near-infrared emission.Furthermore, the NC exhibited selective and dual sensing of glycine(GLY) through (nonenzymatic) electrochemical (EC) and fluorescencemethods, which is assigned to the unique combination of the strongemission and conducting properties of Au-CuNC and N-GQD, respectively,in the same material and is a first-time report of all the above-mentioned.The limits of detection (LODs) obtained for GLY by EC and fluorescencesensing were 10 nM and 1 mu M, respectively and are the lowestLOD values reported hitherto in the respective categories. Comparedto the controls, AuCuNC@N-GQDs exhibited a similar to 20-fold enhancementwith a sensitivity of 0.377 mu A mu M-1 cm(-2). The preferential Au-GLY interaction is consideredto be the reason for the selective sensing of GLY by AuCuNC@N-GQDand the improvement in the electronic and conductivity characteristicsdue to N-GQD to the enhanced sensitivity. The sensing performancewas successfully extended to real blood and urine samples spiked withGLY without interference.