Industrial effluents are a leading major threat for water contamination, subsequently which results in severe health associated risks. Hence, purifying wastewater before releasing into the water resources is essential to avoid contamination. In this study, ZnO/Cu-DPA nano-composites were prepared by altering the percentage of Cu-DPA (20%, 30%, 40%, and 50% which are denoted to be ZnO/20%Cu-DPA, ZnO/30%Cu-DPA, ZnO/40%Cu-DPA and ZnO/50%Cu-DPA) using a simple mechanical grinding process. Several spectroscopic studies were employed such as electron paramagnetic analysis (EPR), powdered X-ray diffractometer (PXRD), UV–Vis absorbance spectroscopy, Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscope to characterize these nano-composites. The photo-catalytic activities of the prepared nano-composites were studied by degrading MB under visible light irradiation. ZnO, ZnO/20%Cu-DPA, ZnO/30%Cu-DPA, ZnO/40%Cu-DPA and ZnO/50%Cu-DPA degradation efficiencies were determined to be 71.8, 78.5, 77.1, and 66.1%, respectively. Among the composite catalysts, the ZnO/20%Cu-DPA coupled system are demonstrated the best efficiency (87%) for photo-degradation of MB within 80 min when exposed to visible light. The ZnO/Cu-DPA nano-composites had a greater MB photodegradation efficiency than pristine ZnO owing to p-n heterojunction in the linked system. Under visible light irradiation, the ZnO/20%Cu-DPA catalysed the conversion of dissolved O₂ to hydroxyl radicals (OH·), triggering the reduction of MB. This suggests that ·OH is the primary specific active radical involved in the photo-catalytic decomposition of MB. Furthermore, EPR analysis indicates the existence of ·OH in the photo-catalytic system. The proposed nano-composites (ZnO/20%Cu-DPA) reusability was investigated across three cycles as the most efficient photo-catalyst. The results show that, the ZnO/Cu-DPA nano-catalyst is a potential candidate for the remediation of dirty water.

Heavy metals like Cadmium, Lead, and Chromium are the pollutants emitted into the environment through industrial development. In this work, a new diphenylamine coordinated cobalt complex (Co-DPA) has been synthesized and tested for its efficiency in removing heavy metals from wastewater, and its adsorption capacity was investigated. The effectiveness of heavy metals removal by Co-DPA was evaluated by adjusting the adsorption parameters, such as adsorbent dose, pH, initial metals concentration, and adsorption period. Heavy metal concentrations in real sample were 0.267, 0.075, and 0.125 mg/L for Cd²⁺, Pb²⁺, and Cr³⁺ before using as-synthesized Co-DPA to treat wastewater. After being treated with synthesized Co-DPA the concentration of heavy metals was reduced to 0.0129, 0.00028, 0.00054 mg/L for Cd²⁺, Pb²⁺, and Cr³⁺, respectively, in 80 min. The removal efficiency was 95.6%, 99.5%, and 99.5% for the respective metals. The adsorption process fitted satisfactorily with Freundlich isotherm with R²(0.999, 0.997, 0.995) for Cd²⁺, Pb²⁺, and Cr³⁺, respectively. The kinetic data obeyed the pseudo-second order for Cd²⁺ and Cr²⁺ and the pseudo-first order for Pb²⁺. Based on the results obtained within the framework of this study, it is concluded that the as-synthesized Co-DPA is a good adsorbent to eliminate heavy metal ions like Cd²⁺, Pb²⁺, and Cr³⁺from wastewater solution. In general, Co-DPA is a promising new material for the removal of heavy metal ions from water. Graphical Abstract

Composites of gold nanomaterials and imaging agents show promise in cancer therapy. Here we have demonstrated a rapid, facile, environmentally friendly, and organic solvent-free method for the synthesis of a gold/gadolinium-doped carbon quantum dot (Au/GdC) nanocomposite for magnetic resonance imaging (MRI) and photothermal ablation (PTA) therapy. The gadolinium-doped carbon quantum dots (Gd@CQDs) were synthesized using a one-pot, microwave-assisted method, and used as reducing and stabilizing agents to both form the Au/GdC nanocomposite and prevent its agglomeration. Formation of the Au/GdC nanocomposite is achieved by simple mixing of Gd@CQDs and a gold precursor, without the addition of any other reducing agents, surface passivating agents, surfactants, or organic solvents. The Au/GdC nanocomposite shows paramagnetism, surface plasma resonance in the near infrared region (NIR), and excellent photostability. Furthermore, it provides high longitudinal relaxivity (r₁ = 13.95 mM⁻¹ s⁻¹), indicating its potential for use as a T₁ contrast agent in MRI. Furthermore, in vitro and in vivo studies using HeLa cells and zebrafish embryos as cancer and animal cell models, respectively, confirmed the low toxicity and excellent biocompatibility of the Au/GdC nanocomposite. Notably, our results demonstrate the ability of the Au/GdC nanocomposite to efficiently destroy cancer cells using PTA. Therefore, this work reveals a simple and powerful strategy to fabricate an Au/GdC nanocomposite for MRI and photothermal ablation of cancer cells.