Highly effective and specific way for the trace analysis of carbaryl insecticides based on Au₄₂Rh₅₈ alloy nanocrystals

The exploitation of Au_xRh_1−x alloy nanocrystals for specifically and directly identifying carbamate pesticides is reported for the first time and could be easily further developed to meet the specific needs of emergency intoxication cases. In this study, Au_xRh_1−x alloy nanocrystals with a tunable composition were synthesized and then employed for the electrocatalytic oxidation of carbamate pesticides. Compared with other Au_xRh_1−x samples and monometallic analogues, the Au₄₂Rh₅₈ sample with an optimized composition showed advances in terms of its electrocatalytic activity. According to electrochemical assessments, we discovered that the Au₄₂Rh₅₈ sample had specific responses to carbaryl. Typical common existing substances including glucide, amino acids, metal ions, and OP pesticides showed no interference in carbaryl determination. Moreover, Au₄₂Rh₅₈ nanocrystals displayed a considerable response towards 1 nM carbaryl without the assistance of acetylcholinesterase (AChE), cholinesterase (ChE) or other biochemical recognition elements. The observed high-efficiency detection was driven by electrocatalyzing the hydrolysis product of carbaryl in a strong alkaline solution. Au₄₂Rh₅₈ alloy nanocrystals with high catalytic activity and good selectivity are promising sensing materials for the detection of trace levels of carbaryl. Furthermore, Au₄₂Rh₅₈ alloy nanocrystals with uniform shape and narrow size distribution could be used in micro/nanoelectrode fabrication technology such as in screen-printing or ink-jetting or in the further design and implementation of real-time identification systems.