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Nanocrystalline NiO/CuO solid solutions and heterostructured powders are prepared by a sol–gel auto combustion method. Herein, the NiO/CuO compounds at various molar ratio, including 100/0, 97.5/2.5, 95/5, 92.5/7.5, 90/10, 80/20, 50/50, 20/80, 10/90, 5/95 and 0/100, are investigated. The structures, morphologies, optical, and magnetic properties of all samples are explored. The detailed structures of the NiO/CuO system are deduced from Rietveld refinements of X‐ray diffraction (XRD) data and the combination of experimental and simulation studies of X‐ray absorption spectroscopy (XAS) spectra. It is found that a small addition of CuO in NiO enhances the formation of rock salt CuxNi1–xO solid solutions with 0 ≤ x ≤ 0.1. The NiO/CuO composites with CuO mole fractions (m) of 20% ≤ m ≤ 95% are affirmed by the coexistence of NiO rock salt and CuO tenorite phases. The composites rich in CuO exhibit strong adsorption in the visible and ultraviolet spectral regions, while the absorption of composites rich in NiO is absent in certain regions of visible and infrared light. In addition, the superparamagnetism of NiO can be tuned to ferromagnetism by a small addition of CuO. The photocatalytic degradation efficiencies of rhodamine B, methylene blue, methyl orange, and methyl red over NiO/CuO reach 92%–97% within a period of 150 min under sunlight irradiation. [ABSTRACT FROM AUTHOR]

Using the sol–gel auto combustion method with diethanolamine (DEA) as fuel, a sequence of iron‐substituted zinc aluminates, ZnFexAl2‐xO4 powders, including variable Fe3+ ion concentrations (0 ≤ x ≤ 2) were effectively prepared. X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), the Brunauer–Emmett–Teller (BET) method, UV–visible diffuse reflectance spectroscopy (UV‐DRS), and vibrating sample magnetometer (VSM) were employed to examine the structures, chemical bonds, morphologies, composition, surface area, and optical properties as well as the magnetic behavior of the obtained samples. A single‐phase spinel structure was obtained for the calcined aluminate powders with different interplanar spacing and crystallite sizes, as revealed by the classification results. The bandgap energy (Eg) of adapted aluminates was in the range of 2.04‐3.14 eV, identified as being much lower compared to the pure sample (5.60 eV). Thus, Fe3+‐substituted ZnAl2O4 samples could be successfully photoexcited using both ultraviolet and visible light, as suggested by the results. Examination of how the four main pollutant types decay when irradiated by sunlight was carried out to assess the samples and establish photocatalytic activity. These contaminants included rhodamine B (RhB), methylene blue (MB), methyl orange (MO), and methyl red (MR). The performance of photocatalytic degradation reached 98% after 150 min for all optimal samples of organic dyes. Besides, each of the altered photocatalysts could be recycled and displayed high stability. The S‐shaped curve of ferrimagnetism can result in those samples as found by the magnetic measurements, though pure ZnAl2O4 displays diamagnetic characteristics. The adapted samples show intense improvement in the remanent magnetization (Mr) when compared to pure ZnAl2O4, signifying that magnetic photocatalyst recovery by applying an external magnetic field is easy. Thus, these results offer a convincing sign that ZnAl2O4 powders replaced by Fe3+ could provide the ability to aid in the ecologically friendly collection of solar energy. [ABSTRACT FROM AUTHOR]

In the present work, the sol–gel auto-combustion method has been used to synthesize nanocrystalline copper-zinc oxide composite powders with different weight ratios using diethanolamine (DEA) as fuel. The structural, morphological, optical, and magnetic properties including the local atomic structure of each calcined sample were systematically characterized by means of XRD, SEM, UV-DRS, VSM, and synchrotron XANES measurements. The XRD results revealed the complete formation of CuO/ZnO nanocomposites, composed of monoclinic CuO and hexagonal wurtzite ZnO structures without any impurity phases. The observation of XANES spectra confirms that both Zn and Cu ions in all samples exhibit only fourfold coordination with oxygen atoms. UV-DRS analysis demonstrated that CuO-rich composites exhibited strong absorption in visible light with moderate infrared reflection efficiency as compared to the pure ZnO sample, but ZnO-rich composites show distinctive absorption in infrared region. According to magnetic measurements, both paramagnetism and ferromagnetism can simultaneously arise as the CuO content increases within the CuO/ZnO composites. The photocatalytic activity of CuO/ZnO composites was evaluated by the decomposition of four types of pollutants: phenol rhodamine B (RhB), heteropolyaromatic methylene blue (MB), azoic methyl orange (MO), and methyl red (MR) under sunlight irradiation. In comparison with pure ZnO, those CuO/ZnO samples for which the ratio has been optimized exhibit enhanced photocatalytic degradation in all organic dyes, reaching 90–96% within a period of 150 min. From these results, it can be argued that CuO/ZnO composites show considerable potential for the harvesting of solar energy as well as environmental remediation. [ABSTRACT FROM AUTHOR]

Binary metal pyrophosphates; Cu(2-x)ZnxP2O7(x= 0.0–2.0) compounds, were prepared via the solid solution method. The synthesize powders were characterized by X-ray diffraction (XRD). The local structure of Cu was analyzed by the mean of synchrotron X-ray absorption near the edge structure (XANES). The Cu2+-O1, Cu2+-O2 and Cu-Cu/Zn distances determined are extended X-ray absorption fine structure (EXAFS) measurements at the Cu K-edge, with a distance of about 1.52, 2.11, and 2.74 Å. The correlation between the structural changes and Cu content was analyzed and discussed. The analysis of the EXAFS spectra collected at the Cu K-edge indicates that the local structure around Cu atoms also is affected by the introduction of Zn atoms in the structure. [ABSTRACT FROM PUBLISHER]