Reduced Graphene Oxide for Surface-Enhanced Infrared Absorption Detection of Cannabidiol in Beverages

Surface-enhanced infrared absorption (SEIRA) spectroscopy is a powerful tool for trace molecular detection, but its efficiency strongly depends on the choice of substrate and its molecular interactions. In this study, we report the synthesis of reduced graphene oxide (rGO) as an enhancement layer for SEIRA-based detection of cannabidiol (CBD). rGO was chemically synthesized using ascorbic acid and characterized via scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and UV–visible spectroscopy to confirm its morphological and electronic properties. SEIRA measurements were performed using a Bio-ATR setup integrated with a Bruker Vertex MCT detector. Laboratory-synthesized rGO yielded markedly stronger vibrational signals than commercially procured graphene nanoplatelets. This effect is attributed to improved molecular adsorption and charge-transfer pathways, which was confirmed by XPS analysis. Density functional theory (DFT) simulations were employed to support spectral assignments. Furthermore, concentration-dependent measurements confirmed the sensitivity of the rGO substrate. The practical application is illustrated by the detection of CBD in complex real beverage solutions. These findings demonstrate that rGO can serve as an effective and scalable substrate for sensitive SEIRA detection of cannabinoid compounds, with potential applications in pharmaceutical quality control, industrial, and forensic analysis.