Ultra-small carbon quantum dots via Hibiscus Sabdariffa for pyridoxine sensing applications

This study proposes an alternative for producing carbon quantum dots through green synthesis using Hibiscus sabdariffa as a carbon source. The synthesis methodology incorporates mesoporous zeolite 4A as a refractory material during thermal treatment and as a sieve for particle size selection. Transmission electron microscopy (TEM) analysis revealed a narrow size distribution of approximately 1.2 nm, aligning with the α-cage diameter of zeolite 4A. Additionally, the CQDs were evaluated as surface-enhanced Raman spectroscopy substrates on a pyridoxine molecule (C₈H₁₁NO₃), which showed an enhancement of the pyridinic ring breathing mode at approximately 1000 cm⁻¹. Furthermore, employing density functional theory (DFT), several carbon structures were theoretically used to represent the CQD–pyridoxine interaction. Based on the molecular descriptor behavior, the charge transfer effects between both systems were studied to determine the elements responsible for the SERS effect associated with the chemical enhancement mechanism. This comprehensive approach provides insight into the structural and optical properties of the synthesized CQDs, with significant implications for their potential application in different areas, particularly in SERS.