Antimicrobial Potential of Chitosan Film Incorporated with Microwave-Synthesised Sodium-Doped Carbon Quantum Dots Against Escherichia coli and Staphylococcus aureus

Chitosan films, versatile and valuable in biomedicine, have attracted keen research interest. These films have been subject to modification and crosslinking with various materials to enhance their properties. This study focuses on the crosslinking of microwave-synthesised blue fluorescence sodium-doped carbon quantum dots (Na-CQDs) with chitosan to form a composite film (CHT/Na-CQDs) using the solvent casting method as potential wound dressings. High-resolution transmission electron microscopy and fluorescence spectroscopy were used to determine the particle size of the Na-CQDs (1.0 to 4.5 nm) and quantum yield (12.3%). X-ray diffraction indicates that Na-CQDs have an amorphous structure resembling the hexagonal phase of graphite. The proposed crosslinking mechanism between chitosan and Na-CQDs involves chemical bonding, hydrogen bonding, and electrostatic attraction. The CHT/Na-CQDs has lower crystallinity compared to Na-CQDs. The swelling capacity of CHT/Na-CQDs (715%) was significantly lower than that of the chitosan film (2300%). Antibacterial testing demonstrated a higher potential of CHT/Na-CQDs against Staphylococcus aureus, a Gram-positive bacterium, compared to Escherichia coli, a Gram-negative bacterium.