Insight into the multiple roles of nitrogen doped carbon quantum dots in an ultrathin 2D-0D-2D all-solid-state Z scheme heterostructure and its performance in tetracycline degradation under LED illumination

The rational design of an all-solid-state Z scheme composite through a single-step hydrothermal treatment by combining ultrathin defect engineered graphitic carbon nitride nanosheets (DCN), tungsten oxide hydrate nanoplates (W), and nitrogen doped carbon quantum dots (NCQDs) has been reported. For the first time, this study demonstrates that NCQD could successfully exfoliate g-C3N4 to produce few-layered thick g-C3N4 nanosheets, besides playing the role of an electron mediator in the composite. The 10%W/1%NCQD/DCN composite exhibited the highest photocatalytic tetracycline degradation efficiency under an 18 W LED illumination. It illustrated a 31.5, 7.7, and 5.2-times higher apparent degradation rate constant (0.044 min−1) than W, bulk g-C3N4, and DCN, respectively. Further, the composite exhibited an outstanding efficacy toward the degradation of various real water matrices. The composite demonstrated high stability and reusability. Furthermore, a plausible all-solid-state Z scheme charge carrier mechanism is proposed based on the results of the radical scavenging experiments.