Enhancement of Raman intensity for the detection of fentanyl

Importance of the topic

Fentanyl is a potent synthetic opioid with a high risk of overdose and widespread illicit distribution. Rapid and sensitive detection methods are essential for forensic screening and public health monitoring.

Study objectives and overview

This application note describes the development of an electrochemical surface-enhanced Raman spectroscopy (EC-SERS) protocol using screen-printed electrodes (SPEs) for the detection and quantification of fentanyl in aqueous solutions. The aim is to integrate nanoparticle generation and SERS measurement in a single experiment.

Instrumentation

• SPELEC RAMAN instrument equipped with a 785 nm laser and matching Raman probe
• Raman spectroelectrochemical cell designed for SPEs
• Gold (220BT) and silver (C013) screen-printed electrodes
• DropView SPELEC software for synchronized electrochemical and optical data acquisition

Methodology

• Electrochemical activation of Au or Ag SPEs by controlled potential cycling to generate SERS-active nanoparticles in situ
• Anodic and cathodic scans: Au SPE (220BT) cycled between +0.70 V and +1.40 V back to –0.20 V; Ag SPE (C013) between 0.00 V and +0.40 V back to –0.40 V at 0.05 V/s
• SERS spectra collected during the final potential iteration to detect adsorbed fentanyl molecules

Main results and discussion

• Distinct Raman bands of fentanyl were recorded on both Au and Ag substrates, with the most intense band at 1000 cm⁻¹ assigned to ring breathing and CC stretching modes
• Variations in band positions and intensities reflect different interactions of fentanyl with Au versus Ag nanostructures
• A linear calibration curve on the Au SPE (220BT) from 1×10⁻⁶ to 1×10⁻⁵ mol/L (0.33–3.37 µg/mL) yielded R² = 0.997, demonstrating excellent quantitative performance

Benefits and practical applications

• Fast, one-step spectroelectrochemical protocol combining nanoparticle formation and SERS detection
• High sensitivity suitable for trace forensic analysis of fentanyl
• Compact instrumentation compatible with portable and field-deployable setups

Future trends and potential applications

• Extension of EC-SERS screening to multiple opioid analogs and other controlled substances
• Integration with handheld Raman devices and point-of-care platforms
• Coupling with microfluidic sample handling for automated workflows
• Application of machine-learning algorithms for rapid spectral classification and quantification

Conclusion

The described EC-SERS method using gold and silver SPEs offers a rapid, sensitive, and straightforward approach for fentanyl detection. Its linear quantitative range and compatibility with compact instrumentation make it a promising tool for forensic, clinical, and field analysis.

References

1. Ott C. E. et al. Forensic Identification of Fentanyl and Its Analogs by EC-SERS. Frontiers in Analytical Science 2022, 2.
2. Wang L., Deriu C., Wu W. et al. Surface Enhanced Raman Spectroscopy, Raman, and DFT Analyses of Fentanyl and Six Analogs. Journal of Raman Spectroscopy 2019, 50(10), 1405–1415.
3. Leonard J., Haddad A., Green O. et al. SERS, Raman, and DFT Analyses of Fentanyl and Carfentanil: Toward Detection of Trace Samples. Journal of Raman Spectroscopy 2017, 48(10), 1323–1329.