Experimental and DFT studies on the vibrational and electronic spectra of 4,5-dihydro-6-methyl-4-[(E)-(3-pyridinylmethylene)amino]-1,2,4-triazin-3(2H)-one

Investigation of the adsorption of pymetrozine on the Au@AgNPs surface and its application in the rapid detection of pymetrozine residues in apple

“…The calculated frequencies of the HL form were observed at 1035.09, 1060.74, 1113.15, 1133.36, 1191.67, 1212.39, 1254.86, 1302.27, 1412.57, 1447.96, 1575.64, and 1599.55 cm −1 . These calculated frequencies were consistent with the results reported by ( Zhang et al, 2011 ). The peak at 1035.09 and 1060.74 cm −1 was related to the torsion and bending vibration of ring I (pyridyl ring), respectively, and the peaks at 1113.15 and 1133.36 cm −1 were consistent with stretching vibrations of N6N7.…”

“…The pKa values of pymetrozine molecules and the distribution of pymetrozine molecules at various pH were calculated by ACD/Labs PhysChem suite (V6, Advanced Chemistry Development Inc. Toronto, Canada). Gaussian 16 package (Gaussian, Inc. USA) was applied for density functional theory (DFT) calculations ( Zhang, Zhou, Jiang, & Li, 2011 ). The optimal geometries and vibrational frequencies of pymetrozine were calculated by using the B3LYP/6–31++G (d, p) method.…”

Self-Cleaning-Mediated SERS Chip Coupled Chemometric Algorithms for Detection and Photocatalytic Degradation of Pesticides in Food

“…There were no prominent peaks in the spectrum of the blank pretreated sample, suggesting that most of the constituents were eliminated during the pretreatment process. Based on DFT calculations [B3LYP-based DFT method with 6-311++G (d,p)] according to related refs, , the possible assignments of the primary vibrational modes for pymetrozine and thiram are shown in Table . − For pymetrozine, the peak at 1027 cm –1 is linked to δ­(CCNCCCH), υ­(CN) ring , and υ­(CC) ring . The peak at 1117 cm –1 is associated with υ­(NN) ring and ρ­(CH), and the peak at 1232 cm –1 is connected to δ­(CCH) and Γ­(NCCH).…”

“…For the GA-PLS built model for pymetrozine prediction, 26 spectral variables were selected out of a total 716 spectral variables and yielded RMSEP = 0.391, RMSECV = 0.374, R p = 0.9789, R c = 0.9793 (Figure C), and PC = 5 (Figure S8C). The selected variables are shown in Figure A,B, and variables such as 284 (1027 cm –1 ), 336 (1131 cm –1 ), 394 (1243 cm –1 ), and 608 (1625 cm –1 ) have been identified to have correlations with pymetrozine in tea . Similarly, for thiram, out of a total 634 spectral variables, 77 spectral variables were selected by the GA-PLS built model and yielded RMSEP = 0.341, RMSECV = 0.386, R p = 0.9826, R c = 0.9776 (Figure F), and PC = 2 (Figure S8D).…”

“…The selected variables are shown in Figure 3A,B, and variables such as 284 (1027 cm −1 ), 336 (1131 cm −1 ), 394 (1243 cm −1 ), and 608 (1625 cm −1 ) have been identified to have correlations with pymetrozine in tea. 38 Similarly, for thiram, out of a total 634 spectral variables, 77 spectral variables were selected by the GA-PLS built model and yielded RMSEP = 0.341, RMSECV = 0.386, R p = 0.9826, R c = 0.9776 (Figure 3F), and PC = 2 (Figure S8D). The selected variables are shown in Figure 3D,E, and variables such as 111 (564 cm −1 ), 275 (924 cm −1 ), 365 (1107 cm −1 ), 513 (1388 cm −1 ), and 581 (1509 cm −1 ) have been recognized for thiram.…”