Yuanzhi Hong,Yadong Meng,Guangyi Zhang,Bingxin Yin,Yong Zhao,Weidong Shi,Changsheng Li
Novel carbon quantum dots (CQDs)/graphitic-like carbon nitride (g-C 3 N 4 ) metal-free heterojunctions were firstly synthesized via a facile low temperature process. Multiple physicochemical techniques were carried out to characterize the samples. The CQDs with the average size of about 5 nm are attached to the surfaces of g-C 3 N 4 nanosheets. The photocatalytic activity of as-prepared samples was carefully evaluated by the degradation of rhodamine B (RhB) and tetracycline hydrochloride (TC-HCl) under visible light irradiation. Photocatalysis result displayed that the CQDs/g-C 3 N 4 heterojunctions can significantly enhance visible-light photocatalytic activity in compared to that of pristine g-C 3 N 4 . The reaction rate constant of the optimum active C0.50%/CN heterojunction for the photodegradation of RhB and TC-HCl were about 3.7-fold and 1.9-fold higher than that of bare g-C 3 N 4 , respectively. The efficiently enhanced photoactivity was attributed to the CQDs not only can improve the photogenerated electron–hole pair’s separation, but also can increase light harvesting by the up-conversion photoluminescence behavior. Moreover, the as-prepared C0.50%/CN sample also exhibited excellent photostability and recyclability for both photodegradation of RhB and TC-HCl. In addition, the possible enhanced photocatalytic mechanism was proposed and analyzed by the active species trapping experiments. This work will bring about potential for application in environmental purification and useful for designing other CQDs-based photocatalyst in energy conversion.
The widespread use of antibiotics has caused the rapid emergence of antibiotic-resistant bacterial strains and antibiotic resistance genes in the past few decades. Photocatalytic inactivation, a promising approach for the killing of pathogens, efficiently avoids the problems induced by antimicrobial drugs. However, traditional photocatalysts usually have some disadvantages, such as high costs of raw materials, ultraviolet ray excitation, and potential leaching of toxic metals. Here, a metal-free heterojunction photocatalyst, denoted as CQDs/g-C 3 N 4 , is synthesized through incorporating carbon quantum dots (CQDs) on graphitic carbon nitride (g-C 3 N 4 ), which significantly enhances photocatalytic inactivation of Staphylococcus aureus ( S. aureus ) compared with pure g-C 3 N 4 in vitro. CQDs/g-C 3 N 4 causes a rapid increase of intracellular reactive oxygen species levels and destruction of cell membranes under visible light, eventually leading to death of bacteria. The efficacy of CQDs/g-C 3 N 4 is further examined by a mouse cutaneous infection model of S. aureus . CQDs/g-C 3 N 4 markedly reduces the bacterial loads and prompts lesion recovery in mice, as compared with g-C 3 N 4 -treated group. In vivo and in vitro toxicity analyses show that the side effects of CQDs/g-C 3 N 4 are negligible. Considering the efficient photocatalytic inactivation and nontoxicity of CQDs/g-C 3 N 4 , this visible-light-driven photocatalyst paves a brand new avenue for the treatment of S. aureus infection.
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