Insights into the Effect of Cation Distribution at Tetrahedral Sites in ZnCo2O4 Spinel Nanostructures on the Charge Transfer Ability and Electrocatalytic Activity toward Ultrasensitive Detection of Carbaryl Pesticide in Fruit and Vegetable Samples

Therecent advancement in designing novel spinel nanostructureshas opened virtually infinite possibilities for the development ofhigh-performance electrochemical sensors to detect target species.The electrocatalytic activity of spinel structures can be enhancedby tuning the cation distribution; however, the role of cation distributionat tetrahedral ions on the electrochemical sensing responses has rarelybeen considered. Herein, the effect of cation distribution at tetrahedralsites (T-d) in the spinel nanostructure ZnCo2O4 on the electrochemical sensing performance toward carbaryl(CBR) was first investigated. The ZnCo2O4 nanoflakesamples with different cation ratios of Zn/Co at tetrahedral siteswere designed by using a facile solvothermal method. We found thata higher Zn ion content at tetrahedral sites significantly enhancedthe electron transfer ability through the electrolyte/electrode interface.More interestingly, a higher Co ion ratio between octahedral sitesand tetrahedral (Co-Oh/Co-Td) promoted the electrochemicaloxidation process of CBR with a higher catalytic rate constant (k (cat)). Under optimized conditions, the ZnCo2O4-NF-based electrochemical nanosensor showed alinear response from 0.15 to 100 & mu;M with a limit of detectionof 0.05 & mu;M and a high electrochemical sensitivity of 2.04 & mu;A & mu;M(-1)cm(-2). The designed nanosensoralso exhibited good repeatability, long-time stability, high anti-interferenceability, and excellent recovery with fruit and vegetable samples.Furthermore, this study offers insights into the cation distribution-dependentelectrocatalytic activities of spinel nanostructures, which is helpfulto the design of advanced spinel nanostructure-based electrocatalystsfor improving the electrochemical sensing performance.