Characterization of carbon materials with Raman spectroscopy

Significance of the topic

Raman spectroscopy offers a rapid, selective and noninvasive approach to probe the microcrystalline structure of carbon nanomaterials. As graphene, graphite, carbon nanotubes and carbon black find growing use in applications ranging from energy storage to industrial composites and sporting goods, a reliable and simple characterization method becomes essential for quality control and materials development.

Study objectives and overview

This application note demonstrates the use of a portable Raman system to characterize various carbon allotropes following ASTM E3220 guidelines. Key goals include identification of the characteristic G, D and 2D bands, calculation of the defect‐to‐order intensity ratio (ID/IG), and establishment of a fast pass/fail quality control metric for graphene‐based samples in manufacturing environments.

Methodology and instrumentation

All Raman measurements employed a 532 nm excitation source on an i-Raman Prime 532H system. A fiber-optic probe mounted in a holder enabled consistent positioning and repeatable sampling. Typical operating conditions were 34 mW laser power, acquisition times between 30 and 90 seconds, and single scans without spectral averaging. Spectral processing included baseline correction to remove atmospheric contributions before peak intensity extraction.

Used instrumentation

• i-Raman Prime 532H portable Raman spectrometer with 532 nm laser
• Fiber-optic probe holder (BAC150B)
• Laser safety enclosure (BAC152C) for class 1 operation
• BWSpec software for data acquisition, baseline correction, and ID/IG calculation

Results and discussion

Spectra of pristine graphene displayed only sharp G and 2D bands near 1580 cm−1 and 2700 cm−1, confirming high crystallinity and very low defect levels. Introduction of defects or edges generated a measurable D band around 1350 cm−1. By measuring the intensities of D and G bands after baseline removal, the ID/IG ratio served as a semi-quantitative indicator of disorder. Values ranged from approximately 0.5 for high-quality graphene to over 1.5 for heavily disordered nanofiber samples. Carbon nanotubes exhibited a split G band (G⁺ and G−) due to curvature effects, while carbon black showed broad, overlapping D and G bands and the highest ID/IG ratios, reflecting its amorphous nature.

Benefits and practical applications

• Fast, non-destructive quality control of graphene and related materials
• Simple pass/fail criteria based on ID/IG for inline or offline manufacturing checks
• Portable setup enables on-site analysis in production environments
• Clear distinction among different carbon allotropes for process optimization and R&D

Future trends and opportunities

Advances in Raman instrumentation and data analytics are expected to further enhance sensitivity to subtle structural variations. Integration of automated mapping and machine learning could enable real-time monitoring of large-area films, composite interfaces and evolving defect populations during processing. Coupling Raman data with complementary techniques such as infrared spectroscopy or electron microscopy may offer a more comprehensive materials fingerprint for next-generation carbon nanomaterials.

Conclusion

Portable Raman spectroscopy following ASTM E3220 provides a robust platform for rapid characterization of carbon nanomaterials. The ID/IG ratio calculated from D and G band intensities yields a reliable metric for structural disorder, supporting quality assurance in both research and industrial settings.

Reference

1. Ferrari AC. Raman Spectroscopy of Graphene and Graphite Disorder, Electron–Phonon Coupling, Doping and Nonadiabatic Effects. Solid State Communications. 2007;143(1):47–57.
2. ASTM International. Standard Guide for Characterization of Graphene Flakes; ASTM E3220-20; ASTM International; 2020.