The effect of solvent environment toward optimization of SERS sensors for pesticides detection from chemical enhancement aspects

In this paper, the flower-shaped silver nanoparticle was used as substrate to investigate the SERS effect of pesticide molecules under different treatment conditions. Due to the variation of molecular structure and molecular interactions with pH value and solvent type, the combination mode of molecules and metal surface and electron transfer also changes, resulting in different SERS effects with a certain regularity. It was demonstrated that the optimum pH values for test conditions are in the range of 6.66-11.11 due to the auxiliary of H+ ions and undestroyed complete functional groups of ethion. Meanwhile, the ethion in the acetone was the best in the three solvents (ultrapure water, absolute ethanol and acetone). Under optimal conditions, ethion can be detected with a minimum detectable concentration of 10(-10) M. The regression model obtained through principal component analysis (PCA) can be used for rapid and precise detection of the concentration of ethion, suggesting the importance of condition optimization for SERS test. Therefore, the solvent environment can be effectively improved to promote non-resonance enhancement of chemical bonding between adsorbate and metal substrate and resonance enhancement of light-induced charge transfer in molecular-metal system by excitation light. The solvent environment has significant effect on the SERS sensor from chemical enhancement. (C) 2017 Elsevier B.V. All rights reserved.