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

Significance of the Topic

Surface-enhanced Raman spectroscopy (SERS) is essential for trace-level detection of chemical species due to plasmonic amplification by noble metal surfaces. Conventional SERS substrates rely on intricate nanostructures, which involve high manufacturing costs and limited stability. Developing cost-effective, disposable substrates that maintain high sensitivity addresses critical needs in analytical chemistry and broadens practical applications.

Objectives and Study Overview

This application note investigates the use of commercially available screen-printed metal electrodes as in situ electrochemical SERS (EC-SERS) substrates. The primary goals are to demonstrate rapid preparation, cost reduction, and sensitive detection of various analytes using a disposable platform produced by mass‐printing techniques.

Methods and Instrumentation

• Electrochemical Activation: Screen-printed electrodes composed of silver, gold, copper, and silver/copper were activated by cyclic voltammetry within defined potential windows to generate plasmonic surfaces.
• In Situ Detection: A 60 µL droplet of 0.1 M KCl solution containing target analytes was applied directly for simultaneous activation and Raman measurement.
• Analytes and Concentrations: [Ru(bpy)₃]²⁺ (250 nM), 4-mercaptopyridine (2 µM), Rhodamine 6G (20 µM), Malachite green (15 nM), Crystal violet (2.5 µM), Nicotinamide (80 µM).

Instrumentation Used

• SPELEC-RAMAN: Integrated Raman spectroelectrochemical system combining a 785 nm laser (Class 3B), a Raman spectrometer (785–1010 nm detection range, 0–2850 cm⁻¹ shift), and a bipotentiostat/galvanostat in a single compact unit.
• RAMANPROBE: Reflection probe suited for 785 nm excitation (up to 500 mW) designed for screen-printed electrode cells.
• RAMANCELL: Black Teflon cell tailored for housing screen-printed electrodes during Raman measurements, ensuring optimal focus and minimal background.

Main Results and Discussion

• SERS Enhancement: All activated screen-printed electrodes provided clear Raman signals for the tested analytes, confirming effective plasmonic activation.
• Analytical Sensitivity: Detection limits reached nanomolar to micromolar concentrations, demonstrating suitability for trace analysis.
• Material Comparison: Silver-based electrodes delivered the highest enhancement, while gold and copper variants offered complementary stability and spectral features.

Benefits and Practical Applications

• Cost Efficiency: Screen-printing enables low-cost, disposable SERS substrates, reducing material and fabrication expenses significantly.
• Versatility: Electrode composition can be tailored to optimize plasmonic response for specific analytes.
• Speed and Simplicity: In situ electrochemical activation negates extensive sample preparation and supports real-time monitoring.

Future Trends and Potential Applications

• Integration with microfluidic platforms for automated, high-throughput SERS analysis.
• Deployment in environmental monitoring and point-of-care diagnostics due to portability and disposability.
• Advancement of mixed-metal or nanocomposite inks to further boost sensitivity and shelf life.
• Combination with machine learning and chemometric tools to interpret complex sample matrices.

Conclusion

This work demonstrates that readily available screen-printed metal electrodes, when activated electrochemically, serve as effective, low-cost, disposable SERS substrates. The approach enables fast and sensitive in situ detection of diverse analytes, opening avenues for widespread adoption in analytical laboratories and field applications.