Characterization of single-walled carbon nanotubes by Raman spectroelectrochemistry

Significance of the topic

Raman spectroelectrochemistry merges spectroscopic and electrochemical techniques to deliver a comprehensive view of carbon nanotube behavior under applied potentials. By combining vibrational analysis with redox monitoring in a single experiment, this approach provides real-time insight into the structural, electronic, and defect evolution of single-walled carbon nanotube (SWCNT) films.

Objectives and Article Overview

This application note demonstrates how the SPELECRAMAN instrument is used to characterize SWCNT films through controlled electrochemical doping in aqueous solution. Key goals include determining nanotube diameter distributions via radial breathing modes, monitoring G-band intensity and position during anodic charging, and quantifying defect density as a function of applied potential.

Materials and Methods

SWCNTs were deposited on a screen-printed carbon electrode (110SWCNT) and immersed in 0.1 M KCl. The SPELECRAMAN, integrating a 785 nm laser, bipotentiostat, and spectrometer (785–1010 nm range, 0–2850 cm⁻¹ shift), recorded Raman spectra with 1 s integration while scanning the potential from 0.00 V to various positive limits (up to +1.80 V) at 0.05 V/s.

Instruments Used

• SPELECRAMAN spectroelectrochemical Raman system (785 nm laser, potentiostat, spectrometer)
• 110SWCNT screen-printed carbon electrode modified with single-walled carbon nanotubes

Results and Discussion

The Raman spectrum showed four characteristic bands: RBM (120–300 cm⁻¹), D, G (1592 cm⁻¹), and G′. Four RBM peaks yielded SWCNT diameters of 1.55, 1.19, 1.07, and 0.92 nm. During anodic scans to +1.00 V, the G-band intensity decreased reversibly, reflecting depletion of Van Hove singularities. At higher potentials (+1.80 V), partial recovery of intensity and an upshift of the G-band occurred, indicating phonon renormalization and changes in C–C bond force constants. The defect-related ID/IG ratio rose from 0.51 at +1.00 V to 1.26 at +1.80 V, confirming electrochemical generation of defects.

Benefits and Practical Applications

Time-resolved Raman spectroelectrochemistry offers:

• Dynamic monitoring of redox processes in CNT films
• Accurate determination of nanotube diameter distributions
• Quantification of defect formation under controlled potentials

Future Trends and Potential Applications

Advances may include multi-wavelength excitation to resolve chiralities, integration with microfluidic cells for on-chip sensing, real-time in situ monitoring of composite materials, and extension to other nanocarbons or two-dimensional materials for energy storage and sensor development.

Conclusion

The combination of Raman spectroscopy with electrochemistry via the SPELECRAMAN system enables a dual-perspective analysis of SWCNT films, providing quantitative data on nanotube structure, doping behavior, and defect dynamics. This methodology enhances material characterization and supports the development of CNT-based sensors and devices.

Reference

1. Dresselhaus M.S., Dresselhaus G., Saito R., Jorio A. Raman spectroscopy of carbon nanotubes. Phys. Rep. 409 (2005) 47–99.
2. Kavan L., Dunsch L. Spectroelectrochemistry of carbon nanostructures. ChemPhysChem 8 (2007) 974–998.
3. Kalbac M., Kavan L., Dunsch L. Bundling effects on Raman G-mode during electrochemical charging of semiconducting SWCNTs. J. Phys. Chem. C 113 (2009) 1340–1345.