Synthesis and characterization of GA-AgNPs for highly sensitive and selective dual colorimetric detection of thiourea and thiophenol with DFT approach.

[Display omitted] • Green synthesis of Silver nanoparticles (AgNPs) from Terminelia chebula extract. • Dual selective colorimetric detection of soil pollutants, thiourea and thiophenol. • The LoD found was remarkably low with 5.79 nM for thiourea and 0.13 µM for thiophenol. • This methodology was practically applied to real soil samples for sensing of thiourea and thiophenol. • A DFT study validated the mechanism of formation of nanoparticles and detection of the pollutants. This work reported a very simple, low cost and easy green method of synthesis of silver nanoparticles (GA-AgNPs) using gallic acid (GA) extracted from Terminalia chebula to detect the soil pollutants thiourea (TU) and thiophenol (TP). The GA-AgNPs were properly characterized by different techniques involving XRD, UV–Visible spectra, XPS, FE-SEM, and Raman spectroscopy. This synthesized GA-AgNPs was used as an effective colorimetric sensor and was even employed in real soil samples. Colorimetric detection was observed in a UV–visible spectrometer by analyzing the change in surface plasmon resonance of NPs when subjected to TU and TP. The result obtained was quick and visibly detectable by the naked eye. The colorimetric study resulted in a good linear relationship and the limit of detection (LoD) was calculated to be 5.79 nM for TU and 0.13 µM for TP. A color detector smartphone application was also used to detect the intensity of color change with variations in different concentrations of TU and TP. This system approach was also applied to real soil samples. Additionally, HPLC was used to validate the presence of TU and TP in the soil and to evaluate their recovery percentage. Density functional theory (DFT) analysis was done to support the plausible mechanism of the interaction between NPs and the sensing molecules. Moreover, the synthesized NPs showed excellent selectivity towards TU and TP in the presence of a wide range of interferences. [ABSTRACT FROM AUTHOR]