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The study investigates the synthesis and characterisation of the Sb2S3/Sb2O3 composite materials through thermal oxidation at 350 °C with varying heating times. The structural, morphology, and electrical behaviours were characterised using XRD, FT-IR, SEM, EDS, UV–Vis spectroscopy, PL, and EIS. The phase transformation from stibnite (Sb2S3) to Sb2O3 phases (senarmontite and valentinite) is observed and discussed. The FT-IR spectra confirm the presence of characteristic Sb–S and Sb–O vibrations. The absorbance spectrum reveals a shift in the energy bandgap (Eg) with values of 1.58–2.23 eV, indicating the compositional changes due to prolonged heating. The emergence of electron donor Sb5+ ions (at 541.36 eV) and Sb3+ (at 540 eV) was investigated in the XPS study. In association, PL emission at 560 nm is attributed to the oxidative transformation of Sb3+ to Sb5+, suggesting the redox transformations within the composite. EIS analysis reveals the fastest interfacial charge-transfer process in the 60 min—heated sample. As a result, the prolonged heating time influences the phase transition and composition, resulting in the properties tailoring of the Sb2S3/Sb2O3 composites. [ABSTRACT FROM AUTHOR]

Owing to the confinement of ZnO in the photocatalytic application: the wide bandgap, the rapid photogenerated carriers recombination, and the expensive cost for the catalyst separation from the wastewater, the p-n heterojunction of NiFe2O4 magnetic phase and ZnO is considered to improve the photocatalytic efficiency and the catalyst separation by the external magnetic. The NiFe2O4/ZnO composites with 0–12 wt% of NiFe2O4 were prepared by an ordinary process and characterized using XRD, Raman, SEM, EDS, TEM, HRTEM, UV–Vis spectroscopy, and PL techniques. The Raman spectra confirm the crystallinity of ZnO and NiFe2O4, including their defects. As increasing NiFe2O4 incorporation, the crystallite size of ZnO phase depicts a lower value with changing from 53.14 to 40.49 nm, whereas NiFe2O4 phase reveals a greater value of 60.61–141.55 nm. The dislocation density, lattice constants, and atomic coordinates are also discussed in terms of ion diffusion. The morphology analysis reveals ZnO particles on the surface of NiFe2O4 microcrystals, confirming the p-n heterojunction formation. The energy bandgap of the as-synthesized samples is in the range of 1.52–2.85 eV, suggesting to the visible light photocatalysis. The prominent PL spectrum indices the forming of Zn interstitial defect state. Under the visible light irradiation, the dye degradation was investigated as a result of the photoreduction percentage and catalyst dosage. With prepared by a facile process, 12 wt% NiFe2O4-loaded ZnO displayed the high methylene blue degradation of 96.96 % within 150 min under visible light irradiation, confirming an excellent photocatalyst. Due to the microstructural composite, the active surface site and the p-n heterojunction were elucidated as the principal mechanism for the difference in reaction time. The dye degradation was discussed in association with the structural constants, morphology, and defects. [ABSTRACT FROM AUTHOR]

The intrinsic defect of ZnO depicts a crucial role in the charge transfer owing to the suppression of the exciton recombination, exhibiting superior semiconducting performance. In this study, the intrinsic defect of ZnO nanostructures prepared by direct thermal activation of 300–900 °C was investigated. X-ray diffraction (XRD) was employed to analyze phase, crystallite size, Zn–O bond length, and dislocation density. The relation of Williamson–Hall (W–H) was used to calculate crystallite size and micro-strain. The atomic coordination was approximated through the Rietveld method. Morphology and crystal growth investigation was carried on by scanning electron microscope (SEM) and tunneling electron microscope (TEM), exhibiting rod-like nanostructures transform to oval shape particle with high residual strain when increasing calcination temperature, exhibiting the crystal growth direction of (101). Specific surface and pore analysis reveals a significant value corresponding to SEM analysis. Fourier transform infrared spectroscopy (FT-IR) detected Zn–O stretching vibration bands, presenting a notable increase in the intensity when heat at 600 °C. Relating to the thermal regime, energy bandgap (Eg) was found to be 3.41–3.50 eV as increasing heat treatment temperatures. Photoluminescence (PL) was applied to determine intrinsic defects through emissive spectra. The surface charge was determined through the zeta potential measurement. The photo-induced dye degradation was measured to understand the effect of the defect in semiconductors. The X-ray photoelectron spectroscopy (XPS) confirms the wurtzite structure appearance, including the intrinsic defects. The observed intrinsic defects are discussed, associating with the structural constants, emissive spectra, cationic dye degradation, and binding energy. [ABSTRACT FROM AUTHOR]