Insight into SERS Chemical Enhancement Mechanism of Fungicide Thiram Adsorbed on Silver Nanoparticles

Abstract

Surface-enhanced Raman spectroscopy (SERS) is an efficient analytical method to detect the chemical compound at ultralow concentration. In this work, chemical enhancement phenomenon during the interaction of fungicide thiram (THR) on silver nanoparticles (AgNPs) is studied by combining experimental and density functional theory approaches. Limit of detection value for THR being 1 lM is achieved. Structural and electronic properties of THR and its complexes with pyramidal Ag 20 clusters as a surface model are investigated at the PBE/cc-pVDZ-PP//cc-pVDZ level of theory. The calculated normal Raman and SERS spectra are in good agreement with the experimental ones. Analysis of the most stable complex indicates that THR interacts with the silver cluster via two S(sp 2 ) atoms at the top of the cluster. By increasing the adsorbed THR molecules from 1 to 3, the SERS peak intensities increase from 4 to 10 times, respectively. The spectral fingerprints of THR are also analyzed via the adsorption of thiram-chlorpyrifos mixture. Consequently, the peaks at 1496, 1350 and 956 cm -1 are recommended as the three most characteristic SERS peaks for quantifying THR in a real mixture. Finally, natural population analysis (NPA) charges, NBO analysis, charge density difference (CDD) maps allow providing more insight into charge transfer process THR and AgNPs.

Surface-enhanced Raman scattering detection of thiram and ciprofloxacin using chitosan–silver coated paper substrates

“…The Ag–S vibrational mode was detected in the SERS spectra of thiram, which can promote charge transfer between the metal and the analyte with a consequent increase of the Raman signal (chemical mechanism). 50 In the case of ciprofloxacin, an electrostatic interaction with metal NPs can be considered. Ciprofloxacin solutions prepared in this work present a pH value of about 5.…”

Sensitive determination of thiram in apple samples using a ZIF-67 modified Si/Au@Ag composite as a SERS substrate

“…It is clear that the LOD in our project is comparable to the values in other literature reports. [41][42][43][44][45][46]…”

Applications of surface‐enhanced Raman spectroscopy in environmental detection

“…While THR is able to protect fruits and vegetables from fungal diseases that may destroy the plants, it also causes skin and mucosal disease in humans 140,180,181 . Numerous recent studies focus on the detection of THR using SERS methods 39,53,61,70,79,127–161 . While we cannot cover each of these references in detail, a few are expanded upon below.…”

“…While the toxicity of most fungicides is generally low, prolonged exposure to these compounds may lead to adverse health effects such as neurological disruptions 126 . Several recent studies have utilized SERS to detect various fungicides, including tetramethylthiuram disulfide (THR), 39,53,61,70,79,127–161 carbendazim, 162–165 chlorothalonil, 166,167 MG, 168–173 TBZ (a fungicide and parasiticide) 20,79,153,155,173–178 and ferbam 20,178,179 . Among them, THR is the most studied due to its wide agricultural applications and strong binding with SERS nanosubstrates through the thiol group.…”