D Band and G Band (Raman)
Definition
The characteristic Raman bands of graphitic carbon materials at approximately 1350 cm-1 (D, disorder) and 1590 cm-1 (G, graphitic C-C stretch); diagnostic for carbon black in black gel inks and permanent inks.
- D band position
- ~1350 cm-1, disorder-induced mode
- G band position
- ~1590 cm-1, graphitic C-C stretch
- Material
- Carbon black in ink pigments
- Application
- Diagnostic for black gel and permanent inks
Common questions
Why are the D and G bands useful for distinguishing ink types rather than just confirming carbon presence?+
The relative intensity ratio of the D and G bands (ID/IG) varies with the degree of structural disorder in the carbon black, which differs by manufacturing process. Comparing this ratio between a questioned ink and reference inks can help discriminate between carbon-black sources even when both simply appear black to the eye.
What limits Raman D/G band analysis when examining ink on a document?+
Fluorescence from paper, dyes, or binders can swamp the weaker Raman signal, and not all black inks contain carbon black at all, some use organic dyes or other pigments that produce no D/G bands. A negative result for these bands does not rule out a black ink; it only rules out a carbon-black-based one.
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