Ameliorating SERS Sensitivity for Pesticide Malathion Detection with Synergistic Boosting Effect by Hydrogen Cations and Chloride Anions

Abstract

Although SERS has been widely recognized as one of the highly sensitive analytical methods that can be deployed in the field with high sensitivity and short analysis time, reports regarding the fast determination of malathion at low concentrations are still scarce. Here, in this work, the solution pH and various halogen co-adsorbates were explored to promote the SERS signal of malathion using the citratereduced Ag NPs. It was found that chloride anions were the most efficient signal booster among the three halogen ions screened. Further examination of the SERS profile of the malathion in the presence of different halogen species found that the stretching mode of the P−S bond shifted to a lower frequency with Cl − , which may imply closer (and stronger) binding of malathion to the Ag NPs. This concurs with literature reports that halogen ions could facilitate the adsorption of a certain analyte onto the SERS substrate. In addition, hydrogen ions showed a synergistic effect on SERS signal enhancement when combined with chloride anions. At optimum conditions, the malathion could be detected with a limit of detection (LOD) of 3 ppb. Malathion-spiked cherry tomatoes and oranges were analyzed, and the recovery rates were found to be within 85−100%.

Iodine-Modified Ag NPs for Highly Sensitive SERS Detection of Deltamethrin Residues on Surfaces

“…It was suggested that halide ions can enhance the SERS signal by forming a coating layer over the Ag NPs upon ligand exchanges. As shown in Figure S2 , the largest red shift of UV spectra was caused by iodide ion, which further confirmed that the optimum halide ion species is generally target specific [ 24 , 27 ].…”

“…Among them, certain inorganic salts showed considerable signal enhancing efficiency. Halide ions were considered effective co-adsorbates to enhance the SERS sensitivity, and many groups, including us [ 24 , 25 ], had been working in this field intensively. For example, polycyclic aromatic hydrocarbons [ 26 ], antibiotics [ 27 ], drugs [ 28 ] have been shown to enhanced SERS signals in the presence of certain halogen ions.…”

Fingerprinting and Differentiation of Landfill Leachate and Domestic Sewage in Surface Water with Machine Learning Based Surface Enhanced Raman Spectroscopy

“…As demonstrated by Kim et al, tuning the surface adsorption on SERS substrates could bring higher dimensionality, thus, better differentiation. Since halogen ions have been widely shown the potential for coadsorption of certain chemicals, , three halogen ions (Br – , I – , and Cl – ) were screened. As shown in Figure S2, after mixing with 10 mM of the halogenate potassium salt (KBr, KI, KCl), all the normalized absorption spectra of Ag-NPs showed red shift, which was consistent with previous reports and proved the successful modification of Ag-NPs by halogens.…”

“…Since halogen ions have been widely shown the potential for coadsorption of certain chemicals, , three halogen ions (Br – , I – , and Cl – ) were screened. As shown in Figure S2, after mixing with 10 mM of the halogenate potassium salt (KBr, KI, KCl), all the normalized absorption spectra of Ag-NPs showed red shift, which was consistent with previous reports and proved the successful modification of Ag-NPs by halogens. As shown in Figure S4a,b, the introduction of Br – ion not only greatly enhanced the SERS signal of LL but also brought much more SERS features, notably at 620, 934, 1034, 1108, 1270, and 1379 cm –1 .…”

“…Subsequently, 1 mL of Ag-NPs was centrifuged at 10 000 rpm for 10 min, and 970 μL of supernatant was removed. Then, 15 μL KBr (10 mM) was added to concentrated Ag-NPs, followed by vortexing for 1 min to obtain bromine-modified Ag-NPs (Ag-BrNPs). , The same procedure was used to prepare the iodine-modified Ag-NPs (Ag-INPs) chlorine-modified Ag-NPs (Ag-ClNPs).…”