New strategies for obtaining the SERS effect in organic solvents

Significance of the Topic

The combination of electrochemical activation and surface enhanced Raman scattering extends sensitive in situ spectroscopic analysis to organic solvents where conventional SERS is challenging. This approach enables real time generation of nanostructured metal substrates and enhances Raman signals of dyes, pesticides and other analytes in nonaqueous media.

Aims and Overview of the Study

This study explores new strategies for achieving the EC-SERS effect in organic solvents by electrochemically activating gold and silver electrodes. The objectives are to demonstrate substrate formation and Raman intensity enhancement for the detection of crystal violet and the fungicide mancozeb under nonaqueous conditions.

Methodology and Instrumentation

Electrochemical activation involved an oxidation step followed by a reduction scan to generate metallic nanostructures on the electrode surface. SERS measurements were carried out concurrently during potential cycling in various organic media. Key components included:

• SPELEC RAMAN instrument integrating a 785 nm Class 3B laser, bipotentiostat/galvanostat and spectrometer covering 785–1010 nm and 0–2850 cm-1 Raman shift
• Raman probe matched to the excitation wavelength
• Spectroelectrochemical cell for conventional electrodes
• Gold and silver working electrodes with steel counter and Ag/AgCl reference electrodes
• DropView SPELEC software for synchronized acquisition of optical and electrochemical data

Main Results and Discussion

Gold electrode activation in acetonitrile with 0.1 M tetrabutylammonium hexafluorophosphate enabled detection of crystal violet down to 1 μmol/L. A cyclic voltammogram revealed oxidation at +1.80 V and reduction at +1.03 V and Raman intensity peaked at +0.20 V during the cathodic scan. For silver electrodes in DMSO with the same supporting electrolyte, an initial pretreatment cycle preceded stable SERS activation by the second cycle. Characteristic Raman bands of mancozeb were observed at 240, 422, 463, 516, 560, 660, 912, 990, 1187, 1272, 1522 and 1615 cm-1.

Benefits and Practical Applications of the Method

This EC-SERS approach offers high sensitivity, rapid substrate formation, and direct analysis in organic matrices without complex nanoparticle synthesis. It is particularly valuable for compounds insoluble in water and can be integrated into quality control workflows for dyes, pesticides and other organic analytes.

Future Trends and Potential Applications

Further developments may include optimization of activation protocols for other metal substrates and solvents, coupling with microfluidic or flow cell systems for on-line monitoring, and application of advanced data analysis to enhance multiplex detection in pharmaceutical, environmental and agri-food sectors.

Conclusion

Electrochemical activation of gold and silver electrodes in organic solvents provides a versatile route to generate SERS-active substrates in situ and achieve micromolar detection of model analytes. This methodology broadens the applicability of spectroelectrochemical Raman analysis in nonaqueous environments.

Reference

1. González-Hernández J, Ott CE, Arcos-Martínez MJ et al. Rapid Determination of the ‘Legal Highs’ 4-MMC and 4-MEC by Spectroelectrochemistry: Simultaneous Cyclic Voltammetry and In Situ Surface-Enhanced Raman Spectroscopy. Sensors 2022;22(1):295.
2. Ibáñez D, González-García MB, Hernández-Santos D, Fanjul-Bolado P. Detection of Dithiocarbamate, Chloronicotinyl and Organophosphate Pesticides by Electrochemical Activation of SERS Features of Screen-Printed Electrodes. Spectrochim Acta Part A Mol Biomol Spectrosc 2021;248:119174.