In situ, fast and sensitive: Electrochemical SERS with screen-printed electrodes

Importance of the Topic

Surface-enhanced Raman spectroscopy (SERS) is a powerful analytical technique for trace-level detection of chemical species. Traditional SERS substrates rely on noble metal nanostructures, which are costly and can degrade over time, limiting their shelf life. Developing cost-effective, disposable substrates that maintain high sensitivity is essential for routine and in situ applications in environmental monitoring, pharmaceutical analysis, and food safety.

Objectives and Overview of the Study

This study evaluates the feasibility of using commercially available screen-printed metal electrodes as SERS substrates for in situ electrochemical SERS (EC-SERS). The goal is to demonstrate fast, sensitive detection of various analytes by combining electrochemical activation with Raman enhancement on disposable printed electrodes.

Methodology

Electrochemical activation protocols by cyclic voltammetry were applied to four types of screen-printed electrodes:

• Silver electrode (C013): scanning from +0.3 V to –0.4 V
• Gold electrode (220BT): scanning from +0.6 V to +1.2 V then to –0.2 V
• Copper electrode (CU10): scanning from +0.15 V to –0.6 V
• Silver/Copper electrode (SPCU10): scanning from +0.10 V to –0.4 V

Concurrent activation and SERS detection were performed in a 60 µL drop of 0.1 M KCl containing target analytes. Tested concentrations included:

• 250 nM tris(2,2'-bipyridine)ruthenium(II)
• 2 µM 4-mercaptopyridine
• 20 µM rhodamine 6G
• 15 nM malachite green
• 2.5 µM crystal violet
• 80 µM nicotinamide

Used Instrumentation

The compact SPELEC-RAMAN instrument integrates:

• 785 nm laser source (Class 3B, up to 500 mW)
• Bipotentiostat/galvanostat for electrochemical control
• Spectrometer covering 785–1010 nm (0–2850 cm⁻¹ Raman shift)

Measurements were conducted in a black Teflon Raman cell (RAMANCELL) using a 785 nm reflection probe (RAMANPROBE) positioned at the optimal focal distance.

Main Results and Discussion

All tested screen-printed electrodes showed clear SERS signals upon electrochemical activation, with characteristic Raman peaks for each analyte. Silver-based electrodes provided the highest enhancement for low-concentration species (e.g., malachite green at 15 nM), while gold substrates offered stable reproducibility. Mixed silver/copper electrodes exhibited intermediate performance. The combined electrochemical and spectroscopic approach enabled rapid signal development within minutes.

Benefits and Practical Applications

• Cost-effective and disposable substrates reduce cross-contamination and maintenance.
• In situ electrochemical activation enhances reproducibility and sensitivity.
• Small sample volumes (60 µL) enable analysis of scarce or precious samples.
• Suitable for field-deployable or point-of-care testing in environmental, biomedical, and industrial settings.

Future Trends and Potential Uses

Future developments may include:

• Integration of microfluidic channels for automated sampling and multiplexed detection.
• Exploration of alternative printable metals and composites for tailored plasmonic properties.
• Software advances for real-time data processing and quantitative analysis.
• Extension to biomolecular detection, such as proteins or DNA, via functionalized electrode surfaces.

Conclusion

Screen-printed metal electrodes, combined with in situ electrochemical activation and SPELEC-RAMAN instrumentation, offer a versatile and sensitive platform for rapid SERS analysis. This approach addresses cost and shelf-life challenges of traditional substrates, paving the way for practical, disposable SERS devices in various analytical applications.