Synthesis and characterization of Zn-doped carbon dots derived from calendula officinalis and glucose: Antibacterial and photoluminescence properties

This study investigates the synthesis and characterization of carbon dots and Zn-doped carbon dots derived from glucose and Calendula officinalis . The synthesis method was hydrothermal, and the samples were characterized by XRD, FTIR, TEM, EDS, and mapping analyses. The Zn-doped carbon dots from Calendula officinalis exhibited superior photoluminescence properties, with higher emission intensity and Ion sensitivity studies demonstrated that Zn²⁺ and Ag⁺ ions notably enhanced the photoluminescence intensity by approximately 15–17 %, whereas Fe³⁺, Co²⁺, and Ni²⁺ induced significant quenching effects. Additionally, pH-dependent analysis revealed that the photoluminescence intensity peaked at pH 11, indicating optimal conditions for exciton recombination under mildly alkaline environments. The antibacterial activity was evaluated through colony counting, well diffusion, and minimum inhibitory concentration tests. Results showed that zinc doping significantly enhanced the antibacterial performance, with the Zn-doped carbon dots from glucose demonstrating the highest antimicrobial activity, with minimum inhibitory concentration values of 0.3125 mg/mL and 0.625 mg/mL against S. aureus and Escherichia coli , respectively. The MTT assay revealed no cytotoxic effect on the L929 cell line. These findings highlight the potential of Zn-doped carbon dots in antibacterial and biocompatible applications, as well as in optical sensing and light-emitting devices.