Novel ternary Z scheme carbon quantum dots (CQDs) decorated WS2/PANI ((CQDs@WS2/PANI):0D:2D:1D) nanocomposite for the photocatalytic degradation and electrochemical detection of pharmaceutical drugs

The endocrine-disrupting chemicals (EDCs) and antibiotics are causing negative effects on human beings and animals by disrupting the endocrine system and spreading antimicrobial resistance. The current need is to eradicate pharmaceutical waste from water bodies using advanced catalytic systems with high efficiency. Novel ternary carbon quantum dots (CQDs) decorated Z-Scheme WS₂-PANI nanocomposite was prepared by a green synthesis assisted in-situ polymerization for the photodegradation and detection of Estradiol (EST) and Nitrofurantoin (NFT). HRTEM micrographs revealed the formation of CQDs with a mean size of 4 ​nm anchored on the surface of WS₂/PANI (width:PANI ​∼ ​20–30 ​nm). The ternary nanocomposite showed excellent photocatalytic activity, degraded NFT (95.7 ​% in 60 ​min), and EST (96.6 ​% in 60 ​min). The rate kinetics study confirms the reaction followed pseudo first-order model. This heterostructure exhibited enhanced performances by modulating the energy level configuration, enhancing the absorption of visible light (2.4 ​eV), and significantly improving the charge separation, three times higher than pristine WS₂. These are highly favorable for increasing the generation of photoinduced charges and enhancing the overall performance of the catalyst. Further, the electrochemical sensor was prepared using CQDs@WS₂/PANI nanocomposite on a paper-based electrode. The CQDs@WS₂/PANI exhibit a linear response of 0.1–100 ​nM, with a limit of detection of 13 ​nM. This synergistic interfacial interaction resulted in the significantly improved electrochemical performance of the modified electrode. The proposed Z-scheme was justified by electron paramagnetic resonance (EPR) and scavenger experiment. An intermediate degradation pathway was also proposed. The synthesized materials were characterized using FESEM, HRTEM, XRD, FTIR, XPS, UV-visible spectroscopy, PL, and TRPL. Therefore, this study provides a direct approach to fabricate a heterojunction that combines two-dimensional, one dimensional, and zero-dimensional properties, enabling control over the energy level configuration and subsequent improvements in photocatalytic and electrocatalytic efficiency.