Synthesis and characterization of clove residue-derived carbon quantum dots: Application in Pickering emulsion with enhanced antibacterial properties

Clove essential oil exhibits excellent antibacterial properties; however, its application is limited by low water solubility. To overcome this, solid particle-based Pickering emulsions have been explored. Carbon quantum dots (CQDs), which are promising solid particles for food applications, have not been studied regarding their synthesis from residual biomass for forming Pickering emulsions. This study aimed to synthesize CQDs from clove residue left over after the extraction of essential oil, assess their emulsifying efficacy, and compare their antibacterial properties with those of a traditional emulsion employing Polysorbate 80 as a surfactant. Four types of CQDs were synthesized using ultrapure distilled water and ethanol, with analyses such as 1H NMR, XPS, and interfacial tension confirming that CQDs synthesized with 40 % ethanol were the most effective as emulsifying agents. Additionally, the unique characteristics of CQDs rendered the Pickering emulsion's surface relatively rough, which enhanced its interaction with bacteria and demonstrated potent antibacterial effects through disruption of the cell membrane. Consequently, this study suggests that the emulsifying efficiency and properties of Pickering emulsions can be tailored by controlling the surface properties of the solid particles.