Voltammetric Analysis of Thiram with Bimetallic Nanosensor and Investigation of Adsorption Mechanism by DFT-D3 Method

In this study, to detect thiram electrochemically, a simple nanosensor based on a glassy carbon electrode (GCE) modified with green-synthesized Ag and Au nanoparticles was designed. AuNPs@AgNPs/GCE nanosensor gave considerably greater signal for 5 ppm thiram in pH 3.0 phosphate buffer solution using adsorptive stripping differential pulse voltammetry compared to bare GCE. Under ideal conditions, the nanosensor produced a linear concentration calibration curve extending from 0.2 to 1.4 ppm for thiram, with limits of detection and quantification of 0.033 ppm and 0.100 ppm, respectively. The developed electrochemical bimetallic nanosensor demonstrated high sensitivity and stability, showing that it is a novel and promising platform for thiram determination. Furthermore, the nanosensor was used to assess thiram in human serum and recovery was obtained as 103.6%. DFT-D3 results showed that covalent modification of GCE with AuNPs/AgNPs occurs with the electron transfer between the electrode surface and thiram by bonding sulfur atoms of thiram to AgNPs and AuNPs. Both experimental and theoretical analyses showed that the modification with Ag and Au, GCE appeared to be a key property to improve the electronic activity at the surface and increase the charge transfer that facilitates the adsorption of the selected guest.