Carbon Analysis with High Signal Throughput Portable Raman Spectroscopy

Importance of the Topic

Carbon nanomaterials like graphene, graphite, and carbon nanotubes exhibit unique mechanical, electrical, and thermal properties that underpin their growing use in industries ranging from energy storage to advanced composites. As their industrial adoption increases, there is a critical need for fast, nondestructive, and reliable methods to characterize structural quality and detect defects in production environments.

Objectives and Study Overview

This study demonstrates the application of a portable, high signal-throughput Raman spectroscopy system for rapid carbon material analysis. The goals are to illustrate how key spectral features can be used for quality control and to validate a simple intensity ratio metric (ID/IG) as a pass/fail criterion for manufacturing settings.

Methodology and Instrumentation

A 532 nm i-Raman® Prime 532H system with an embedded tablet computer was employed. Measurements used a fiber-optic Raman probe mounted in a motorized holder and conducted within a laser-safe enclosure, converting the system to laser class 1 for floor use. Typical parameters were ~34 mW laser power and 30–90 s acquisition time. Data processing, including baseline correction and peak intensity extraction, was performed in BWSpec® software.

• Raman system: i-Raman Prime 532H (532 nm laser)
• Probe holder: BWT-840000395 for coarse/fine XYZ alignment
• Safety enclosure: BWT-840000609 for Class 1 operation
• Software: BWSpec® with baseline removal and ID/IG calculation

Key Results and Discussion

Carbon Raman spectra are dominated by three bands: G (~1580 cm⁻¹), D (~1350 cm⁻¹), and 2D (~2700 cm⁻¹).

• High-quality graphene shows a sharp G-band and strong 2D-band, with no detectable D-band.
• Graphite displays a broadened, asymmetrical 2D-band and lower I2D/IG ratio than graphene.
• Single-walled carbon nanotubes split the G-band into G⁺ and G⁻ modes due to curvature effects.
• Carbon black exhibits a pronounced D-band and high ID/IG, reflecting its disordered structure.

The ID/IG ratio, calculated after baseline correction following ASTM E3220-20 guidelines, increases with structural disorder. Spectra from carbon nanofibers and black powders confirmed that higher ID/IG values correlate with increased defect density and lower crystallinity.

Benefits and Practical Applications

• Rapid, nondestructive quality control of carbon materials in research or manufacturing.
• Simple ID/IG metric provides a clear pass/fail threshold for defect monitoring.
• Portable, safe Raman setup allows at-line or inline analysis on the production floor.
• Automated data processing and reporting streamline routine screening tasks.

Future Trends and Opportunities

Advancements may include integration of multiple laser wavelengths to exploit band dispersion for more detailed structural insights, coupling portable Raman with machine-learning algorithms for automated defect classification, and expanding the technique to monitor composite interfaces or other 2D materials in real time. Additionally, miniaturized probes and fiber-optic arrays could enable remote or in situ process control in harsh environments.

Conclusion

Portable high-signal Raman spectroscopy presents a robust solution for characterizing carbon nanomaterials, leveraging simple spectral features and the ID/IG ratio for rapid quality assessment. Its adaptability, safety, and ease of use make it well suited for modern production workflows requiring nondestructive, at-line analysis.

References

1. A. C. Ferrari, Solid State Communications, 143, 47–57 (2007)
2. ASTM E3220-20, Standard Guide for Characterization of Graphene Flakes, ASTM International, West Conshohocken, PA, 2020