Abstract
Carbon quantum dots (CQDs) have recently drawn enormous attention due to not only their unique chemical, biological, and optical properties but also because a variety of renewable biomasses are readily utilized as carbon sources in their synthesis. This study investigated the synthesis, characterization, and functional evaluation of CQDs from unbleached mechanical pulp as a natural lignocellulosic resource. The CQDs were synthesized using a one-step hydrothermal synthesis with varying temperature, time, and pulp consistency. The resulting CQDs exhibit a spherical shape with a size distribution of 9.73 ± 0.82 nm and lattice parameters of 0.21 and 0.34 nm, indicating a graphite core. The photoluminescence spectra showed evident fluorescence characteristics, with an emission peak at 435 nm at an excitation wavelength of 370 nm. The as-prepared CQDs were also chemically composed of C=C and C=O bonds linked to the hydroxyl and carboxyl functional groups, which are typically found in lignocellulose-based CQDs. The CQDs demonstrated antibacterial activity exceeding 99.9% against E. coli at the lowest concentration of 0.75 mg/mL. Demonstrating its antioxidation property, the DPPH radical scavenging activity surpassed 90% with more than 40 µg/mL of the CQD solution.