Surface enhanced Raman scattering (SERS) experiments and quantum chemical calculations (using density functional theory) on the interactions of chlorpyrifos (CPF), which is an intensively used pesticide, with a roughed silver nanoparticle surface were thoroughly investigated to study the inherent molecular mechanism. Ligand–cluster interaction geometries show that the CPF molecule is mainly adsorbed on the silver surface via both S atom and pyridine ring involving a covalent Ag···S coordination as well as van der Waals physisorption. Raman vibrational modes of CPF are centered at 474, 632, 678, 1277, and 1551 cm–1 characterizing the P–O–C bending, P═S stretching, Cl-ring mode, and pyridine ring stretching, respectively, which are all enhanced when CPF is adsorbed on a silver surface. The concentration-dependent effect of CPF on silver substrates has been reproduced for the first time by coordinating 2 and 3 CPF molecules on an Ag20 silver cluster model simulated by DFT computations. The intensities of the characteristic peaks of CPF as shown in the calculated SERS spectra are increased by 2 and 3 times with respect to those of the CPF–Ag20 complex, which indicate a positive influence of high analyst concentration on the SERS signal. This observation can be explained by the electron-donating effect of CPF upon adsorption. The latter donates an electron from its lone pair on S and Cl atoms and a π electron on the S═P bond to silver atoms on the surface, and then the positive charge of silver surface is displaced to the CPF moiety via Ag···S and Ag···Cl contacts. The information obtained from the adsorption of CPF on silver by SERS is helpful to understand the molecular mechanism of adsorption process involving chlorpyrifos ligand coordinated on silver nanoparticle surfaces. It also contributes to design field detection methods for rapid screening and monitoring of pesticides in environment or agricultural products by using portable detection systems such as paper-based or fiber-based SERS sensors.

Lone pair

Silver nanoparticle

Physisorption

10.1021/acs.jpcc.0c06078

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Citations (47)

Roles of H₂O in comparison with H₂S in the complexes of thioaldehydes and hydrogen chalcogenides

Vietnam Journal of Chemistry (2021)

Ngo Vuong Hoang Ngo Thi Hong Nhung Nguyen Ngoc Tri Nguyen Truong An Thuc‐Huy Duong

Abstract Twenty stable geometrical structures of the interactions between RCHS and nH 2 Z (R = H, F, Cl, Br, CH 3 ; n = 1‐2; Z = O, S) were investigated. Addition of H 2 O or H 2 S molecule into the RCHS∙∙∙1H 2 Z system induces an enhancement of the stability and cooperative capacity of the complexes investigated, in which it is ca. 2 times more stable for adding H 2 O compared to H 2 S. The substitution of one H atom in HCHS by both halogen (F, Cl, Br) and CH 3 group causes an increase in the larger stability of RCHS∙∙∙H 2 Z in comparison with HCHS∙∙∙H 2 Z. The stability of complexes follows the order of H < F ~ Cl ~ Br < CH 3 substituted‐derivatives. Strength of hydrogen bonds decreases in the sequence of O–H∙∙∙O > O–H∙∙∙S > S–H∙∙∙S > C sp2 –H∙∙∙O > C sp2 –H∙∙∙S. Besides, the O/S–H∙∙∙S and O–H∙∙∙O red‐shifting hydrogen bonds are mainly governed by an increase in the population of the σ*(C sp2 −H) and σ*(O/S−H) orbitals. Meanwhile, the C sp2 –H blue shift in C sp2 –H∙∙∙O/S hydrogen bonds are determined by both the decrease in the electron density of the σ*(C sp2 −H) orbitals and the lowering in s‐character percentage of C sp2 in C sp2 ‐H bonds.

10.1002/vjch.202100059

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Citations (1)

Improved NO2 gas sensing performance of 2D MoS2/Ti3C2Tx MXene nanocomposite

Applied Surface Science (2022)

Qui Thanh Hoai Ta Nguyen Ngoc Tri Jin‐Seo Noh

10.1016/j.apsusc.2022.154624

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Citations (30)

One-step synthesis of oxygen doped g-C3N4 for enhanced visible-light photodegradation of Rhodamine B

Journal of Physics and Chemistry of Solids (2020)

Doan An Tran Chi Thanh Nguyen Pham Nguyen Ngoc Tri Hung Nguyen Phi Qui Thanh Hoai Ta