Diazinon is a highly efficient, highly toxic, low residual organophosphorus pesticide used widely in rice, vegetables, and corn crops. Conventional methods for diazinon detection are limited by expensive instruments and tedious sample pretreatment methods, so a new method for rapid, simple, and reliable trace pesticide residues is needed to ensure the safety of crop products. In this paper, silver nanoparticles were synthesized as active substrates using a reduction technique for SERS signal enhancement. The SERS spectra of diazinon were collected over a wide range of concentrations. The characteristic peaks at 1642 cm-1 and 1351 cm-1 were selected for quantitative analysis, and their coefficient of determination (R2) were 0.9929 and 0.9951, respectively. In addition, the molecular structure of diazinon was simulated for the first time, and the vibrational modes corresponding to the characteristic spectra of diazinon were calculated with good agreement using the density flooding theory B3LY P/6-31+G (d, p). These results indicate that the application of SERS to diazinon detection is feasible and has broad application prospects.
Although the concentration of plant hormone abscisic acid (ABA) in crops is very low, it can effectively regulate the growth of crops. Traditional ABA detection methods are limited by expensive instruments and cumbersome sample processing. Therefore, a new method for detecting ABA in ultra-low concentrations is urgently needed. In this paper, a new method for fast and accurate determination of ABA content based on Surface Enhanced Raman Spectroscopy (SERS) was proposed. In this method, a solution of silver-coated gold nanoparticles (Au@Ag) was self-assembled into dense monolayer under the action of capillary gradient force at the air/water interface, which could be transferred to PDMS wafers and filter paper as SERS active substrates. R6G was used as a probe molecule to characterize the Sensitivity and accuracy of PDMS SERS active substrates. When the PDMS active substrate was selected to detect ABA, the detection limit 1×10−11 M was obtained, indicating that PDMS supported core-shell precious metal monolayer substrate can be used as a effective active substrate for detecting ABA. This method is also expected to be applied to the detection of other plant hormones such as corn and soybean.
Plasmonic core-shell nanoparticles (CSNPs) have been extensively used as SERS active-substrates because their localized surface plasmonic resonance (LSPR) properties and thus the surface enhanced Raman scattering (SERS) activities can be regulated by changing the shell thickness. In this work, we selected Ag@MoS2 CSNP with 40 nm radius of Ag as core and varied thickness of MoS2 as shell to investigate the shell-dependent plasmonic behaviors including LSPR and SERS by using finite difference time domain (FDTD) simulations. The LSPR peak of Ag@MoS2 CSNPs shows a broad red-shifting with an increasing shell thickness from 0 nm to 40 nm, giving rise to that the LSPR peak tunes from visible region (385 nm) to near infrared (NIR) region (1100 nm). The SERS activity of Ag@MoS2 CSNP, represented by the enhancement of local electrical field (EM), can also be modulated by changing the shell thickness, and the optimal enhancement factor (EF) under 633 nm laser excitation is determined to be 3.54×106 when the shell thickness is 4 nm. The wide-range LSPR tunability of Ag@MoS2 CSNP provides enormous potential for NIR SERS application and enhanced photocatalytic activity
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