Revisiting the Raman disorder band in graphene-based materials: A critical review

Graphene-based materials, including composites with metals, metal oxides, or polymers, demonstrate enhanced vibrational, electronic, and mechanical properties, rendering them highly promising for applications in energy, sensing, and catalysis. Vibrational spectroscopy is extensively used to characterize these materials, with primary focus on the G band (first-order in-plane vibrational band), the 2D band (second-order overtone), and the defect-activated D band. Although the D band frequently appears in chemically modified or structurally complex graphene systems, its spectral characteristics, such as peak position, linewidth, and relative intensity, alongside variations in the G and 2D bands, are often underreported or inadequately interpreted. This review underscores the critical importance of the D band in assessing disorder, edge structure, doping, and matrix interactions within graphene-based materials. Revisiting the role of the D band in conjunction with the G and 2D bands highlights the necessity for a more comprehensive vibrational analysis framework to accurately evaluate structural perturbations and interfacial effects in graphene-based materials.