Portable Raman Instrumentation for SERS Applications

Importance of the Topic

Surface enhanced Raman spectroscopy (SERS) addresses the need for ultra‐sensitive molecular detection in fields such as environmental monitoring, food safety and security. By overcoming the inherently weak Raman scattering signal through metallic nanostructure enhancements, SERS enables trace‐level identification of explosives, contaminants and biomarkers in real‐world settings.

Aims and Overview

This application note presents the configuration and performance of a portable Raman system optimized for SERS analyses. It demonstrates how the B&W Tek i-Raman Plus 785S, coupled with specialized accessories, delivers laboratory‐grade sensitivity, resolution and laser safety in a field‐deployable format.

Methodology and Instrumentation

The core instrumentation comprises:

• i-Raman Plus 785S Portable Raman Spectrometer: TE‐cooled back-thinned CCD detector (–2 °C), wide spectral range (65–3 350 cm⁻¹), resolution 4.5 cm⁻¹, integration up to 30 min.
• BAC151 Video Microscope Sampling Accessory: Enables precise laser focusing on small (≈5×5 mm²) SERS substrates with objective lenses (10× to 100×) yielding beam spot sizes from 210 µm down to 21 µm.
• BAC152 Laser Class 1 Enclosure: Shields reflected laser light and ambient interference while ensuring operator safety across 532, 785 and 1 064 nm wavelengths.
• BCR100A Raman Cuvette Holder: Holds standard 1 cm path length cuvettes, aligning the probe via a mirror‐based, three‐point locking mechanism to boost signal by up to three times and minimize fluorescence background.

Main Results and Discussion

The back‐thinned CCD achieves up to 90 % quantum efficiency, minimizing detector noise and enabling low‐light SERS detection down to trace levels. The 785 nm excitation reduces fluorescence background. A spectral resolution of 4.5 cm⁻¹ successfully separates closely spaced peaks, demonstrated by distinguishing a blank SERS substrate peak at 641 cm⁻¹ from an analyte peak at 625 cm⁻¹. The adjustable beam spot control ensures consistent laser targeting on micro‐scale substrates.

Benefits and Practical Applications

• Portable, low‐power system suitable for on‐site environmental or security screening.
• High signal‐to‐noise ratio and long integration capability enhance detection limits.
• Precise focusing and small beam size support analysis of microfabricated SERS chips.
• Enclosure ensures compliance with laser safety standards and blocks ambient light.

Future Trends and Opportunities

Advances in nanofabrication will drive more uniform and reproducible SERS substrates, further lowering detection limits. Integration with multivariate software and artificial intelligence can automate spectral identification. Miniaturized, battery‐powered Raman modules may expand applications into wearable sensors and real‐time diagnostic devices.

Conclusion

The combination of the i-Raman Plus 785S spectrometer, BAC151 focusing accessory and BAC152 enclosure offers a robust, portable solution for SERS. It balances laboratory‐grade sensitivity, spectral resolution and safety, enabling trace‐level chemical analysis in field or industrial environments.

References

1. Sharma B., Frontiera R.R., Henry A.I., Ringe E., Van Duyne R.P., Materials Today, 2012, 15(1-2), 16-25.
2. Botti S., Almaviva S., Cantarini L., Palucci A., Puiu A., Rufoloni A., J. Raman Spectroscopy, 2013, 44, 463–468.