Synthesis and physical characterization of carbon quantum dots from watermelon seed towards a biological application

Carbon quantum dots (CQDs) incorporated into hydrogels are promising materials for drug delivery applications, especially for wound dressings. Its green synthesis, using biomass such as watermelon seeds, offers important economic, environmental, and technological advantages, aligning with the principles of the circular economy and supporting its potential for biomedical use. In this work the CQDs were synthesized via the hydrothermal method, and their physicochemical properties were thoroughly characterized using multiple techniques, including Atomic Force Microscopy (AFM), Dynamic Light Scattering (DLS), Fluorescence Microscopy, Fourier Transform Infrared (FTIR) spectroscopy, Raman spectroscopy, Scanning Electron Microscopy (SEM), Ultraviolet-visible (UV-vis) spectroscopy, and X-ray Photo electron Spectroscopy (XPS). Hydrogels were prepared using Polyvinyl Alcohol (PVA) and Hydroxypropyl Methylcellulose (HPMC) to assess the antimicrobial activity and cytotoxicity of CQDs, both in their pure form and integrated into the hydrogels. SEM analysis revealed that the CQDs exhibited a near-spherical morphology, with a grain size of approximately 142 nm. AFM give us smaller particle size, measuring around 10 nm. Raman spectroscopy identified two dominant peaks at 1340