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

Abstract

In this work, we present an ultrastable gold–copper nanocluster on nitrogen-doped graphene quantum dot (AuCuNC@N-GQD), with a stability of ≥1 year, achieved through a galvanic exchange process, which displayed intense solid- and solution-state near-infrared emission. Furthermore, the NC exhibited selective and dual sensing of glycine (GLY) through (nonenzymatic) electrochemical (EC) and fluorescence methods, which is assigned to the unique combination of the strong emission 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 fluorescence sensing were 10 nM and 1 μM, respectively and are the lowest LOD values reported hitherto in the respective categories. Compared to the controls, AuCuNC@N-GQDs exhibited a ∼20-fold enhancement with a sensitivity of 0.377 μA μM–1 cm–2. The preferential Au–GLY interaction is considered to be the reason for the selective sensing of GLY by AuCuNC@N-GQD and the improvement in the electronic and conductivity characteristics due to N-GQD to the enhanced sensitivity. The sensing performance was successfully extended to real blood and urine samples spiked with GLY without interference.