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This paper demonstrates the preparation of ZnMn2O4 nanoparticles through thermal hydrolysis in different solvents, such as isopropanol, ethylene glycol, glycerol, and water, combined with pyrolysis. The obtained samples were characterised by using X-ray diffraction (XRD), infrared spectroscopy (FT‒IR), scanning electron microscopy (SEM), energy-dispersive X-ray mapping, nitrogen adsorption/desorption isotherms, and a vibrating sample magnetometer. The electrocatalytic activity of ZnMn2O4 nanoparticles was investigated toward the oxidation of uric acid (UA) and xanthine (XA). The ZnMn2O4-nanoparticle-modified electrode not only enhances the oxidation currents of the two purine derivatives but also successfully separates the voltammetric signals of the analytes in their binary mixture and, hence, is employed for their simultaneous determination. The factors affecting the analysis, such as pH, scan rate, linear range, detection limit, reproducibility, and interferents, were also investigated. The results show that the UA and XA limits of detection are as low as 0.55 and 1.28 µM, and the modified electrodes have satisfactory repeatability and reproducibility. The practical application of the modified electrode was demonstrated by simultaneously determining the concentrations of UA and XA in urine samples with exceptional accuracy. [ABSTRACT FROM AUTHOR]

Photocatalysis under low energy light is of great importance for study of environmental pollution impact. There is an increasing demand for preparing integrated photocatalysts to show their potential in persistent organic compound degradation under visible and near-infrared light. In this work, we have reported the structural combination of three functional components of NaYF4:Yb,Er, TiO2, Cu into photocatalytic nanocomposites for near-infrared light (NIR) photocatalysis. Uniform and monodisperse NaYF4:Yb,Er nanocubes prepared by hydrothermolysis were used as a photon converter and they were combined with TiO2 semiconductor and Cu co-catalysts by sequential deposition to fabricate NIR-active photocatalysts. The Cu/TiO2/NaYF4:Yb,Er nanocomposites were investigated for the organic degradation under NIR light. The Cu/TiO2/NaYF4:Yb,Er photocatalysts were photoactive with NIR light and full decomposition of methylene blue was reached for 90 min. These nanocomposites exhibit the NIR photocatalytic response caused by the NIR light absorption and photon electron transfer over NaYF4:Yb,Er, TiO2, and Cu components. [ABSTRACT FROM AUTHOR]