Carbon-based nanocomposites coated with iron oxides were synthesized using a wet impregnation method with thermally annealed coal and an iron nitrate precursor. The influence of the thermal treatment atmosphere (air, vacuum, or nitrogen) on the morphology, structure, and magnetic properties of the nanocomposites was examined by X-ray diffraction, Raman spectroscopy, and transmission electron microscopy. It was found that the vacuum thermal treatment produced carbon-based nanocomposite containing iron oxide with the highest crystallinity, according to XRD analysis, while also inducing the greatest degree of structural defects in the carbon matrix, as evidenced by Raman analysis. Mössbauer spectroscopy confirmed that all thermal treatment methods promote the formation of the hematite phase, which was found to be the only phase formed in the air-treated nanocomposites, whereas traces of magnetite and the formation of Fe(OH)₃ were detected in the vacuum- and nitrogen-treated nanocomposites, respectively. Magnetic characterization revealed that all nanocomposites exhibit ferromagnetic-like behavior, attributed to the weak ferromagnetic nature of hematite. The best magnetic response (highest saturation magnetization with the widest hysteresis loop) was observed in the vacuum-treated nanocomposites. These findings collectively demonstrate that the synthesis atmosphere plays a crucial role in tailoring the structural and magnetic characteristics of carbon-based iron oxide nanocomposites, offering pathways for their optimization in applications such as catalysis, environmental remediation, or sensing technologies.

Solution-processing is a low-cost solution method to preparea variety of organic or inorganic thin films. For metal oxide compounds, a solution-processing solution of an organometallic compound is frequently used as a precursor to be spin coated, followed by a thermal annealing to form metal oxide. In this work, vanadium oxide powders are obtained from a simple acid-base reaction, and then they are dispersed in isopropyl alcohol to form a solution for spin-coating. Different amount of cobalt salt are also added together with VOx into isopropyl alcohol to form VOx:Co2+ solutions. After thermal annealing at 200 °C, continuous transparent thin films are obtained. Optical, structural, morphological and chemical binding energies of those films are analyzed. It is found that amorphous VO2:Co2+ compound is formed in those films with V:Co atomic ratios between 6.6:1 and 1.6:1. Optical absorption onsets of those films are around 2.3 eV. An interesting interconnected porous morphology is observed when the atomic ratio of V:Co is around 4.9:1. It is concluded that porous amorphous cobalt doped vanadium oxide thin films can be obtained from a spin-coating process at low annealing temperature from a simple solution without any complex agent.

Monoclinic scheelite BiVO₄ is a visible-light photocatalyst whose performance is limited by charge–carrier recombination and inefficient charge transport. Here, a surfactant-free 3² full factorial design was used to study the effects of initial pH (0.25, 0.50, and 0.75) and hydrothermal temperature (160, 180, and 200 °C) on the structural, morphological, optical, photoelectrochemical, and photocatalytic properties of BiVO₄. All nine samples exhibited the monoclinic scheelite phase, with no detectable secondary crystalline phases within the XRD detection limits, and showed nearly invariant unit-cell parameters, V−O bond length, crystallite size, and optical band gap (2.44 ± 0.06 eV). In contrast, the I(040)/I(110) intensity ratio, used as a descriptor of preferential crystallographic orientation, varied from 2.32 to 3.36 and showed a strong correlation with the apparent rate constant for methylene blue (MB) discoloration (r = 0.931; Bonferroni-corrected p = 0.002), with the correlation remaining robust in leave-one-out sensitivity analysis. Higher ratios were associated with plate-like morphologies, lower charge-transfer resistance, and higher photocurrent. Response-surface analysis identified an optimum within the experimental domain, and the sample prepared at pH 0.50 and 180 °C reached 86.8% MB discoloration in 90 min (k_app = 0.0224 min⁻¹), with an apparent rate constant approximately six times than of the least active sample. Scavenger tests indicated that O₂ reduction pathways and photogenerated holes are the main contributors. These results identify preferential crystallographic orientation as a useful, though not exclusive, structural descriptor of photocatalytic activity in monoclinic BiVO₄.