Photocatalysis is a more proficient technique that involves the breakdown or decomposition of different organic contaminants, various dyes, and harmful viruses and fungi using UV or visible light solar spectrum. Metal oxides are considered promising candidate photocatalysts owing to their low cost, efficiency, simple fabricating method, sufficient availability, and environment-friendliness for photocatalytic applications. Among metal oxides, TiO₂ is the most studied photocatalyst and is highly applied in wastewater treatment and hydrogen production. However, TiO₂ is relatively active only under ultraviolet light due to its wide bandgap, which limits its applicability because the production of ultraviolet is expensive. At present, the discovery of a photocatalyst of suitable bandgap with visible light or modification of the existing photocatalyst is becoming very attractive for photocatalysis technology. However, the major drawbacks of photocatalysts are the high recombination rate of photogenerated electron–hole pairs, the ultraviolet light activity limitations, and low surface coverage. In this review, the most commonly used synthesis method for metal oxide nanoparticles, photocatalytic applications of metal oxides, and applications and toxicity of different dyes are comprehensively highlighted. In addition, the challenges in the photocatalytic applications of metal oxides, strategies to suppress these challenges, and metal oxide studied by density functional theory for photocatalytic applications are described in detail.

Among the existing commercial cathodes, Ni-rich NCM are the most promising candidates for next-generation LIBs because of their high energy density, relatively good rate capability, and reasonable cycling performance.

In this study, cellulose was extracted from sugarcane bagasse (SCB) through a convenient five-step treatment, and procedures were performed. During the alkaline curing process of the extraction of cellulose, NaOH has a concentration of (0.5, 1.5, 2.75, and 4) and the extraction time (15, 30, and 45min) at a constant temperature of 120°C were taken as variables and perfectly optimized by response surface methodology (RSM) for cellulose with the highest product. The optimum conditions were found to be 2.75 NaOH, 120°C, and 45min with a cellulose yield of 73.71±0.67 cellulose, 17.22±0.82 hemicellulose, and 9.07±0.95 lignin. Though most of the lignin was eliminated during the alkaline and dilute acid pretreatment process, the remaining lignin was removed by a solution treatment of 4 NaOH, and 21.92 H₂O₂ at 121°C for 44.97min where the cellulose yield was found as 89.75±0.64, hemicellulose was 6.15±0.83, and lignin was 2.65±0.66. Morphological analysis revealed that the average diameter of the cellulose was 12.06µm. Thermal and XRD diffraction analysis showed that the cellulose is thermally stable and has a crystallinity index of 31.63. FTIR spectra demonstrate that cellulose was successfully extracted due to the removal of noncellulose components.

Crystalline lead sulfide (PbS) nanowires doped with terbium (Tb³⁺) ions were synthesized by the chemical bath deposition method at room temperature. The powder was obtained from an aqueous solutions using lead acetate dehydrate, terbium nitrate, thiourea, potassium hydroxide and ammonia. The terbium molar concentrations were varied in the deposition process to investigate the effect on the structural, optical, morphological and luminescent properties of PbS nanowires. The crystalline size was found to be dependent on the concentration of the Tb³⁺ ions used. The estimated average crystalline sizes were calculated from the X-ray diffraction and found to be 34, 33 and 37 nm for PbS: 0% Tb³⁺, PbS: 0.2% Tb³⁺ and PbS: 0.5% Tb³⁺, respectively. The scanning electron microscopy micrographs depict nanowire shape for the undoped as well as Tb-doped samples. The energy-dispersive X-ray and Auger electron spectroscopy analyses confirmed the presence of all the expected elements. The solid powder nanowires exhibited high absorptions in the UV–Vis regions. The band gap energies were estimated in the range of 1.99–2.46 eV. The absorption edge and the band gap energies of these PbS nanowires have shifted depending on the concentration of the dopant. The maximum luminescence intensity was obtained for PbS: 0.2% Tb³⁺ ions and luminescent quenching was observed for higher terbium concentrations. Graphic abstract

This study uses the Quantum ESPRESSO code to introduce Hubbard correction (U) to the density functional theory (DFT) in order to examine the effects of non-metals (C, F, N, and S) doping on the structural, electronic, and optical characteristics of rutile TiO₂. Rutile TiO₂ is a substance that shows promise for use in renewable energy production, including fuels and solar energy, as well as environmental cleanup. Its wide bandgap, however, restricts their uses to areas with UV light. In order to move the rutile TiO₂ absorption edge toward visible light, one atom of each dopant was substituted at oxygen atom locations in this work. The calculated band structures yielded a bandgap of 3.03 eV for pure rutile TiO₂, which is in good agreement with the experimental measurement. The bandgap of all doped materials, with the exception of F-doped TiO₂, displayed a redshift. The absorption edges in C, N, and S-doped TiO₂ are displaced toward the visible area, as indicated by the imaginary component of the dielectric function peaks. The appropriateness of C, N, and S-doped TiO₂ for photocatalysis applications is demonstrated by the shift in the absorption coefficient to the highest wavelength. The presence of extra charges that attenuate the transmission of light in materials is shown by the increase in refractive index following doping. Furthermore, this discovery is crucial for experimentalists since it helps them understand how non-metal doping affects the characteristics of rutile TiO₂ for photocatalysis applications.

Pathogens with multidrug resistance have recently been responsible for widespread disease, fatalities, and economic distress. A nanomaterial with antibacterial characteristics is used to reduce the infection’s resistance. Metal-oxide nanocomposites are nanomaterials that exhibit outstanding physical and chemical characteristics. They are prime candidates for innovative functional materials with antimicrobial activity as one of their main uses. This review will summarize the current progress on the antimicrobial activity of metal-oxide nanocomposite, including widely recognized research outputs and recent findings, as these materials can overcome the limitation of the individual material due to their utterly different properties from the single materials. Additionally, it describes several metal-oxide nanocomposites that are produced using various methods for the application of antimicrobial activity, as well as the variables that can affect such activities and the main inhabitation mechanisms of this materials.