Copper(II) Complex of Graphene Oxide for Highly Selective and Sensitive Fluorescence Sensing of Histidine in Water and Milk

In this work, a good water‐dispersible GO‐Cu 2+ ‐1, 8‐diaminonaphthalene complex (GCU) was synthesized from graphene oxide (GO), CuCl 2 , and 1, 8‐diaminonaphthalene in mild condition. The GCU achieved histidine detection with high selectivity and high sensitivity. Upon addition of histidine, the fluorescence intensity of GCU at 410 nm increased significantly due to the blocked photoinduced electron transfer (PET) process. The linear concentrations range of histidine detection was from 0.1 to 4.0 µM, with a limit of detection (LOD) of 0.027 µM. Common amino acids and proteins do not affect the detection of histidine by GCU in water. Furthermore, the GCU has been successfully applied not only to detect histidine in water but also to measure histidine in milk. The fluorescence sensor‐based assay using GCU represents a promising method for nutritional monitoring.