Economical, one-pot, and green synthesis of plant-based carbon quantum dots for efficient visible-light photocatalytic dye degradation and water purification

Abstract

BackgroundGreen, in-situ, one-pot, facile, and economical synthesis of efficient photocatalysts to destroy emerging aqueous contaminants is essential. MethodBiocompatible carbon quantum dots (CQDs) photocatalysts were successfully synthesized from a plant source called garden thyme as a low-cost precursor by one-step calcination method. CQDs were synthesized in both pure form and co-doped with fluorine and boron indicating size of <10 nm and favorable quantum yield of 40%. Four key factors including synthesis temperature, synthesis time, fluorine and boron weight ratios, and CQDs size were investigated on removal rates of organic pollutant Rhodamine B (RhB). Significant findings10%F-10%B co-doped CQDs with synthesized at 400 ºC for 5 h with a size of <10 nm, showed the highest photocatalytic RhB degradation performances of 86.1% and 89% within 40 and 60 min, respectively. This improved performance was originated from synergetic influences of quantum size, co-doping, promising quantum yield, and great visible light harvesting, that satisfactorily separated and transported light-created electron-hole pair. Trapping experimental data approved that hydroxyl radicals were dominant reactive species that oxidized RhB on F,B co-doped CQDs catalysts upon visible light radiation. Overall, CQDs could be easily synthesized as a green and super-cheap photocatalyst and would be effective for wastewater treatments.