Advances in Surface-Enhanced Raman Scattering Sensors of Pollutants in Water Treatment

Abstract

Water scarcity is a world issue, and a solution to address it is the use of treated wastewater. Indeed, in these wastewaters, pollutants such as pharmaceuticals, pesticides, herbicides, and heavy ions can be present at high concentrations. Thus, several analytical techniques were initiated throughout recent years for the detection and quantification of pollutants in different types of water. Among them, the surface-enhanced Raman scattering (SERS) technique was examined due to its high sensitivity and its ability to provide details on the molecular structure. Herein, we summarize the most recent advances (2021-2023) on SERS sensors of pollutants in water treatment. In this context, we present the results obtained with the SERS sensors in terms of detection limits serving as assessment of SERS performances of these sensors for the detection of various pollutants.

Keywords: SERS; heavy ions; pesticides; pharmaceuticals; sensors; water treatment.

Figure 1

(a) TEM picture of the AgNP-PS-b-PAA film. (b) AFM picture of the AgNP-PS-b-PAA film. (c) SERS spectra of the rhodamine B molecules in water, recorded on the AgNP-PS-b-PAA film. The Raman spectrum called blank is recorded on PS-b-PAA film (without AgNPs) with a rhodamine B concentration of 1 mM. All the figures are reprinted (adapted) with permission from [60], Copyright 2021 American Chemical Society.

Figure 2

SERS spectra of (a) the river water and (b) the fishpond water, containing the following OCP: tetradifon (blue dashed line: peak at 198 cm${}^{-1}$), 4,4’-DDT (red dashed line: peak at 390 cm${}^{-1}$), chlordane (green dashed line: peak at 630 cm${}^{-1}$), and $\alpha$-endosulfan (black dashed line: peak at 160 cm${}^{-1}$). For (a,b): a,b,c correspond to following OCP concentrations: tetradifon (150 nM, 50 nM, and 5 nM, respectively), 4,4’-DDT (150 nM, 50 nM, and 5 nM, respectively), chlordane (150 nM, 50 nM, and 5 nM, respectively), and $\alpha$-endosulfan (50 nM, 30 nM, and 6 nM, respectively), and d corresponds to water without OCP. (c) TEM picture of a gold superparticle. (d) Electric field mapping of a gold superparticle at a wavelength of 785 nm corresponding to the excitation wavelength used for Raman measurements. All the figures are reprinted (adapted) with permission from [61], Copyright 2021 American Chemical Society.

Figure 3

(a) Scheme of the Au nanoparticles with the molecules of 4-CBA (in red color). (b) SERS spectra of an AuNPs solution with 10 mM of PDS and 57 $\mathsf{\mu }$M of 4-CBA for several durations under sunlight illumination (oxydation time of the citrate layer). For the caption, “o(+)”, “o(−)”, “a(+)”, and “a(−)” correspond to the presence (+) and absence (−) of PDS (o) and 4-CBA (a), respectively. All the figures are reprinted (adapted) with permission from [68], Copyright 2022 American Chemical Society.

Figure 4

(a) SEM picture of the r-Ag/Au fiber morphology. (b) Setup photo of the technique combining the three functionalities (working electrode, SPME, and SERS). The WE, RE, and CE electrodes correspond to the working, reference, and counter electrode, respectively. SERS spectra of benzidine recorded on the r-Ag/Au fiber at (c) several concentrations, and (d) at LOD of 5 $\mathsf{\mu }$g/L. On (c,d), the red dashed line and the one with the red five-pointed star correspond to the vibration mode of benzidine located at 1186 cm${}^{-1}$. All the figures are reprinted (adapted) with permission from [70], Copyright 2022 American Chemical Society.

Figure 5

(a) SERS spectra of MEA and its isotopologue MEA-d${}_4$: in black, 50 ppm of MEA-d${}_4$ without MEA, in green with 25 ppm of MEA, and in blue with 75 ppm of MEA. The MEA-d${}_4$ peak at 870 cm${}^{-1}$ corresponds to the reference peak. (b) Measurements of MEA concentration during a period of 4.5 years collected with 25 distinct Raman spectrometers for an initial concentration of MEA of 25 ppm. All the figures are reprinted (adapted) with permission from [73], Copyright 2023 American Chemical Society.

Figure 6

(a) Illustration of the NPP-NS fabrication. (b) SERS spectra obtained with NPP-NS in drinking water mixed with a CV solution containing Cd${}^{2+}$ ions at concentrations ranging from ${10}^{-12}$ M to ${10}^{-4}$ M, and a control without Cd${}^{2+}$ ions (only with CV). (c) SERS intensity at 1175 cm${}^{-1}$ versus Cd${}^{2+}$ concentration (M), where (Con) corresponds to the control solution of CV without Cd${}^{2+}$ ions. All the figures are reprinted (adapted) with permission from [83], Copyright 2022 American Chemical Society.