In this work, pure BiFeO₃ and samples doped with different concentrations of chromium were synthesized to improve the optical properties and efficiency of solar cells based on BiFeO₃. The sol-gel method was used for synthesis due to its ability to produce nanostructured materials with high purity and good homogeneity, as well as the possibility of controlling the size and shape of the resulting particles. The samples were characterized by different analytical techniques. Thermal analysis results indicate that the dopant increases the weight loss of the sample from 61 to 81%, with an increase in the exothermal in the nucleation and crystallization temperature range. The X-ray diffraction patterns and UV-visible spectra show a dependence of the crystallite size and bandgap with respect to the amount of Cr dopant, decreasing from 168 to 73 nm and from 2.14 to 1.92 eV, respectively. Scanning electron microscopy images display a decreasing grain size as a result of an increasing amount of dopant. The I-V analysis results show a 1% Cr-doped BiFeO₃ photovoltaic device exhibits enhanced photovoltaic performance with higher photocurrent and 4.17 times greater energy conversion efficiency compared with a pure BiFeO₃ photovoltaic device. For their behavior, Cr-doped BiFeO_3-based photoelectrodes are very promising materials for photovoltaic devices.

This study presents a sustainable and scalable biosynthesis method for zinc oxide (ZnO) nanoparticles using Bacillus subtilis, focusing on their application in photocatalytic cyanide degradation in aqueous solutions. The bacterial strain was molecularly identified through 16S rRNA gene sequencing and phylogenetic analysis. The optimized biosynthesis process yielded crystalline ZnO nanoparticles in the zincite phase with an average size of 21.87 ± 5.84 nm and a specific surface area of 27.02 ± 0.13 m²/g. Comprehensive characterization confirmed the formation of high-purity hexagonal ZnO (space group P63mc) with a bandgap of 3.20 eV. Photocatalytic tests under UV irradiation demonstrated efficient concentration-dependent cyanide degradation, achieving 75.5% removal at 100 ppm and 65.8% at 500 ppm within 180 min using 1.0 g/L ZnO loading. The degradation kinetics followed a pseudo-first-order model with rate constants ranging from 6.64 × 10⁻³ to 3.98 × 10⁻³ min⁻¹. The enhanced photocatalytic performance is attributed to the optimal crystallite size, high surface area, and surface defects identified through a microscopic analysis. These results establish biosynthesized ZnO nanoparticles as promising eco-friendly photocatalysts for industrial wastewater treatment.

In this study, we synthesized pure and cobalt-doped NiTiO₃ perovskite nanostructures using a sol–gel method and characterized them to investigate the impact of cobalt incorporation on their photocatalytic hydrogen production under UV light. XRD analysis confirmed the formation of the hexagonal ilmenite structure, with lattice parameters increasing with cobalt doping, indicating the substitution of larger Co²⁺ ions onto smaller Ni²⁺ sites. Raman spectroscopy revealed a decrease in the intensity of active modes, suggesting crystal structure distortion and oxygen vacancy generation. UV-vis spectroscopy showed a decrease in bandgap energy from 2.24 to 2.16 eV with cobalt doping up to 5%, enhancing UV light absorption. SEM and TEM images revealed nanoparticle agglomeration, while cobalt doping did not significantly alter particle size up to 5% doping. Photoluminescence spectroscopy revealed an initial increase in PL intensity for NiTiO₃-1%Co, followed by a systematic decrease with higher cobalt concentrations, with NiTiO₃-10%Co exhibiting the lowest intensity. Photocatalytic experiments demonstrated a remarkable improvement in hydrogen evolution rate with increasing cobalt doping, with NiTiO₃-10%Co exhibiting the highest rate of 940 μmol∙g⁻¹·h⁻¹, a 60.4% increase compared to pure NiTiO₃. This enhanced performance is attributed to the substitution of Co²⁺ on Ni²⁺ sites, the modification of electronic structure, the suppression of electron–hole recombination, and the creation of surface catalytic sites induced by cobalt incorporation. The proposed mechanism involves the introduction of Co²⁺/Co³⁺ energy levels within the NiTiO₃ bandgap, facilitating charge separation and transfer, with the Co⁺/Co²⁺ redox couple aiding in suppressing electron–hole recombination. These findings highlight the potential of cobalt doping to tune the properties of NiTiO₃ perovskite for efficient hydrogen production under UV light.

This study investigates the effects of chromium (Cr³⁺) doping on BaTiO₃ nanoparticles synthesized via the sol–gel route. X-ray diffraction confirms a Cr-induced cubic-to-tetragonal phase transition, with lattice parameters and crystallite size varying systematically with Cr³⁺ content. UV–visible spectroscopy reveals a monotonic decrease in bandgap energy from 3.168 eV (pure BaTiO₃) to 2.604 eV (5% Cr³⁺-doped BaTiO₃). Raman and FTIR spectroscopy elucidate structural distortions and vibrational mode alterations caused by Cr³⁺ incorporation. Transmission electron microscopy and energy-dispersive X-ray spectroscopy verify nanoscale morphology and successful Cr³⁺ doping (up to 1.64 atom%). Antioxidant activity, evaluated using the DPPH assay, shows stable radical scavenging for pure BaTiO₃ (40.70–43.33%), with decreased activity at higher Cr³⁺ doping levels. Antibacterial efficacy against Escherichia coli peaks at 0.5% Cr³⁺ doping (10.569 mm inhibition zone at 1.5 mg/mL), decreasing at higher concentrations. This study demonstrates the tunability of structural, optical, and bioactive properties in Cr³⁺-doped BaTiO₃ nanoparticles, highlighting their potential as multifunctional materials for electronics, photocatalysis, and biomedical applications.

This study presents a comprehensive investigation into the synthesis, characterization, and photocatalytic performance of NiTiO₃/TiO₂ nanocomposites for solar hydrogen production. Through a carefully optimized sol–gel method, we synthesized a heterojunction photocatalyst comprising 99.2% NiTiO₃ and 0.8% anatase TiO₂. Extensive characterization using XRD, Raman spectroscopy, FTIR, UV–visible spectroscopy, photoluminescence spectroscopy, and TEM revealed the formation of an intimate heterojunction between rhombohedral NiTiO₃ and anatase TiO₂. The nanocomposite demonstrated remarkable improvements in optical and electronic properties, including enhanced UV–visible light absorption and an 85% reduction in charge carrier recombination compared to pristine NiTiO₃. Crystallite size analysis showed a reduction from 53.46 nm to 46.35 nm upon TiO₂ incorporation, leading to increased surface area and active sites. High-resolution TEM confirmed the formation of well-defined interfaces between NiTiO₃ and TiO₂, with lattice fringes of 0.349 nm and 0.249 nm corresponding to their respective crystallographic planes. Under UV irradiation, the NiTiO₃/TiO₂ nanocomposite exhibited superior photocatalytic performance, achieving a hydrogen evolution rate of 9.74 μmol min−1, representing a 17.1% improvement over pristine NiTiO₃. This enhancement is attributed to the synergistic effects of improved light absorption, reduced charge recombination, and efficient charge separation at the heterojunction interface. Our findings demonstrate the potential of NiTiO₃/TiO₂ nanocomposites as efficient photocatalysts for solar hydrogen production and contribute to the development of advanced materials for renewable energy applications.

Dye-sensitized solar cells (DSSCs) have attracted renewed research interest as a potential low-cost substitute for conventional silicon photovoltaics. This work aims to improve the photovoltaic performance of the DSSCs by incorporating multi-walled carbon nanotubes (MWCNTs) into the BaTiO₃ photoelectrode. The pure BaTiO₃ and BaTiO₃/MWCNT nanocomposites were sensitized with N719 dye and fabricated into solar cell devices for testing. The structural characterization confirmed the successful formation of the nanocomposite with an optimal dispersion at 6% of MWCNT incorporation, beyond which agglomeration effects manifested. The optical analysis verified the modulation of defect states and bandgap engineering induced by the MWCNT network. The morphological studies revealed irregular nanoparticle clusters with embedded nanotubes. Solar cell testing under AM1.5G-simulated sunlight demonstrated a peak power conversion efficiency of 4.044% for 6% of MWCNT doping, constituting a 6-fold increment versus pure BaTiO₃ (0.693%). It originated from the simultaneous enhancements in the open-circuit voltage and short-circuit current enabled by the favorable band structure alterations and percolation-assisted charge transport. However, further increasing MWCNT content deteriorated the device metrics, owing to emerging limitations like trapping. The rational integration of multi-walled carbon nanotubes with lead-free ferroelectric metal oxides can contribute to the development of emerging organic-inorganic hybrid solar platforms.