Portable Raman Instrumentation for SERS Applications

Importance of the topic

Surface-enhanced Raman spectroscopy (SERS) has become an essential tool for ultrasensitive detection in fields such as environmental safety, food analysis, homeland security and biomedical diagnostics. Driven by the need to overcome the detection limits of conventional Raman methods, SERS enables trace-level identification of explosives, chemical residues and biomarkers at the point of need.

Objectives and overview of the study/article

This application note presents a portable Raman system optimized for SERS applications. It outlines the instrument configuration, performance characteristics and sampling accessories that together deliver laboratory-grade sensitivity and resolution in a compact, field-deployable format.

Methodology and instrumentation used

A B&W Tek i-Raman Plus 785S dispersive spectrometer is the heart of the setup, featuring a TE-cooled back-thinned CCD detector (–2 °C, up to 90 % quantum efficiency) and a spectral range of 65–3 350 cm⁻¹ with 4.5 cm⁻¹ resolution. Sampling accessories include:

• BAC151 video microscope probe for accurate laser focusing on 5×5 mm SERS substrates (spot sizes from 21 µm to 210 µm with 10×–100× objectives)
• BAC152 Class 1 laser enclosure for user safety and ambient light rejection
• BCR100A cuvette holder for solution-based SERS using standard 12.5 mm × 12.5 mm cuvettes, providing three-point locking, internal mirror and light trap for enhanced reproducibility

Main results and discussion

The cooled CCD enables low-noise operation and extended integration times up to 30 minutes, achieving high signal-to-noise ratios for weak SERS signals. A 785 nm excitation source minimizes fluorescence background. The 4.5 cm⁻¹ resolution successfully separates closely spaced peaks, as demonstrated by distinguishing an intrinsic substrate peak at 641 cm⁻¹ from an analyte signal at 625 cm⁻¹. The adjustable laser spot and video microscope ensure precise targeting of micrometer-sized SERS spots, while the Class 1 enclosure shields stray reflections and ambient light.

Benefits and practical applications

• Portable and cost-effective solution for on-site analyses
• Trace-level detection limits for environmental, food and security sampling
• High spectral resolution suitable for complex mixtures
• Flexible measurement of both solid-state SERS chips and solution-based samples
• Enhanced reproducibility through precision optics and sampling controls

Future trends and potential applications

• Advanced nanostructured substrates for further sensitivity enhancement
• Multiplexed detection of multiple analytes in complex matrices
• Automated sampling and onboard data analysis using multivariate algorithms
• Miniaturized handheld devices for real-time diagnostics
• Field deployment in environmental monitoring, food safety screening and point-of-care testing

Conclusion

The portable i-Raman Plus system combined with video microscope and safety enclosure provides an ideal SERS platform, offering high sensitivity, spectral resolution, precise focusing and safe operation. This versatile solution bridges the gap between benchtop performance and field usability.

Reference

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