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Quantum Yields and N <sub/>2</sub> O Formation from Photolysis of Solid Films of Neonicotinoids
摘要： Neonicotinoids (NN), first introduced in 1991, are found on environmental surfaces where they undergo photolytic degradation. Photolysis studies of thin films of NN were performed using two approaches: (1) transmission FTIR, in which solid films of NN and the gas-phase products were analyzed simultaneously, and (2) attenuated-total-reflectance FTIR combined with transmission FTIR, in which solid films of NN and the gas-phase products were probed in the same experiment but not at the same time. Photolysis quantum yields using broadband irradiation centered at 313 nm were (2.2 ± 0.9) × 10?3 for clothianidin (CLD), (3.9 ± 0.3) × 10?3 for thiamethoxam (TMX), and (3.3 ± 0.5) × 10?3 for dinotefuran (DNF), with all errors being ±1s. At 254 nm, which was used to gain insight into the wavelength dependence, quantum yields were in the range of (0.8?20) × 10?3 for all NNs, including acetamiprid (ACM) and thiacloprid (TCD). Nitrous oxide (N2O), a potent greenhouse gas, was the only gas-phase product detected for the photolysis of nitroguanidines, with yields of ΔN2O/ΔNN > 0.5 in air at both 313 and 254 nm. The atmospheric lifetimes with respect to photolysis for CLD, TMX, and DNF, which absorb light in the actinic region, are estimated to be 15, 10, and 11 h, respectively, at a solar zenith angle of 35° and 12, 8, and 10 h at a solar zenith angle of 15°.
关键词： acetamiprid,dinotefuran,thiamethoxam,thiacloprid,clothianidin,neonicotinoids
更新于2025-09-19 17:15:36
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Fabrication of Silver-coated Gold Nanoparticles to Simultaneously Detect Multi-class Insecticide Residues in Peach with SERS Technique
摘要： Fast sampling and multicomponent detections are important in the analysis of pesticide residues detection. In this work, surface-enhanced Raman scattering (SERS) method based on silver-coated gold nanoparticles (Au@Ag NPs) was used to simultaneously detect multi-class pesticide residues such as thiacloprid (carbamate), profenofos (organophosphate) and oxamyl (neonicotinoid) in standard solution and peach fruit. The Au@Ag NPs with 26 nm Au core size and 6 nm Ag shell thickness exhibited significant Raman enhancement, especially by the creation of hot spots through NPs aggregation induced by the connection between Au@Ag NPs and target molecules. The findings demonstrated that the characteristic wavenumber of the pesticides (thiacloprid, profenofos, and oxamyl) could be precisely identified using the SERS method. Compared with earlier studies, the current approach was rapid, inexpensive and without lengthy sample pretreatment. Moreover, the results revealed that the limit of detection (LOD) was 0.1 mg/kg for thiacloprid obtained in the peach extract with determination coefficient (R2) of 0.986. Additionally, LOD for both profenofos and oxamyl was 0.01 mg/kg with a determination coefficient (R2) of 0.985 and 0.988, respectively. Good recovery percentage (78.6 to 162.0 %) showed the high SERS activity with better accuracy for the detection of the thiacloprid, profenofos, and oxamyl in peach. The results of this study could offer a promising SERS platform for simultaneous detection of other contaminants such as thiacloprid, profenofos and oxamyl in multifaceted food matrices.
关键词： oxamyl,substrate,fruit,SERS,thiacloprid,simultaneous detection,profenofos,core-shell nanoparticles
更新于2025-09-04 15:30:14