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.

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.

Cyanide (CN) is a toxic environmental pollutant generated by various industrial activities, necessitating the application of bioremediation techniques for its degradation. Biodegradation is a more cost-effective and environmentally friendly technique with high efficiency in CN removal. This study isolated cyanide-degrading bacteria from Tutupaca mining site soil from Tacna, Peru. Bacillus subtilis strain TT10s was selected for its exceptional capacity to rapidly and completely eliminate cyanide under alkaline conditions (pH 10.5), removing 1000 ppm cyanide within 48 h. A kinetic analysis revealed that the biodegradation follows second-order rate kinetics (k₂ = 0.08649 mg/(mg·h), R² = 0.96622), consistent with the literature attribution of the rate-limiting step to the inducible cyanide dihydratase enzyme, which converts cyanide into ammonia and formate via the Michaelis–Menten model. Fourier-transform infrared spectroscopy (FTIR) spectral analysis further corroborated this enzymatic mechanism, showing the disappearance of CN peaks coupled with the emergence of ammonia (NH) and formate (C=O) peaks. Quantitative kinetic modelling integrated with FTIR profiles and degradation curves implicates cyanide dihydratase as the key rate-controlling enzyme in alkaline cyanide biodegradation without the need for an extra carbon source, generating interest for future bioremediation applications in highly contaminated environments.

Glioblastoma multiforme (GBM) remains the most aggressive primary brain tumor with median survival of 14.6 months, necessitating novel therapeutic approaches. Here, we report the biogenic synthesis of zinc oxide nanoparticles (ZnO NPs) using Bacillus licheniformis strain TT14s isolated from mining environments and demonstrate their selective anti-glioma efficacy. ZnO NPs exhibited hexagonal wurtzite structure (crystallite size: 15.48 nm) with spherical morphology (19.37 ± 5.28 nm diameter) as confirmed by XRD, HRTEM, and comprehensive physicochemical characterization. Colloidal stability analysis revealed an isoelectric point at pH 7.46, ensuring optimal dispersion in biological media. Cytotoxicity evaluation revealed remarkable selectivity: at 100 μg/mL, ZnO NPs reduced NG-108 glioblastoma cell viability to 36.07 ± 1.89% within 1 h while maintaining 78.9 ± 0.94% viability in primary retinal cells. The selective cytotoxicity was attributed to the interplay of convergent mechanisms acting under dark conditions, including defect-mediated ROS generation supported by photoluminescence analysis revealing a characteristic oxygen vacancy emission at 550 nm, pH-dependent dissolution enhanced in the acidic tumor microenvironment, and preferential cellular uptake by rapidly proliferating cancer cells with compromised antioxidant defenses. Time-course analysis demonstrated concentration-dependent effects with therapeutic windows favoring normal cell preservation. The intrinsic cytotoxic activity under dark laboratory conditions eliminates the need for external activation, providing practical advantages for therapeutic applications. These findings establish ZnO NPs as promising candidates for targeted glioblastoma therapy, warranting further in vivo validation and mechanistic elucidation for clinical translation.

Iron is one of the most widely used dopants for enhancing the photocatalytic properties of oxide semiconductors. In this work, nickel titanium ilmenite was synthesized by the sol–gel method and doped with small amounts of iron substituting for nickel to determine the dopant’s influence on its structural, optical, and photocatalytic properties. The materials were characterized by XRD with Rietveld refinement, Raman spectroscopy, FTIR, SEM, TEM, UV-Vis diffuse reflectance, XPS, and steady-state and time-resolved photoluminescence, and were evaluated for photocatalytic hydrogen generation, including reuse tests. The characterization confirmed a pure ilmenite phase characteristic of NiTiO₃, with iron incorporated substitutionally and no secondary iron-containing phase. Raman deconvolution quantifies the resulting lattice disorder: the A_g mode at 710 cm⁻¹ broadens from 44.8 to 60.4 cm⁻¹ and loses more than 90% of its integrated area across the series. UV-Vis diffuse reflectance shows a systematic red shift in the apparent optical absorption edge, from 2.25 to 1.88 eV; the Urbach energy increases from 118 to 365 meV, a magnitude comparable to the shift itself, indicating that the red shift is dominated by disorder-induced band tailing rather than by a rigid displacement of the band edges. Time-resolved photoluminescence shows that the photogenerated carrier lifetime increases from 1.78 ± 0.01 ns in pristine NiTiO₃ to 2.14 ± 0.02 ns in Ni_0.97Fe_0.03TiO₃ and decreases again at higher dopant contents, reproducing the volcano-shaped dependence of the photocatalytic activity. The Ni_0.97Fe_0.03TiO₃ sample exhibited the highest hydrogen production rate in the presence of ethanol as a sacrificial agent, 378.3 ± 15.6 μmol∙g⁻¹h⁻¹, a 31% improvement compared to pristine NiTiO₃ (288.8 ± 10.8 μmol∙g⁻¹h⁻¹), achieved without any co-catalyst. Across the series, activity correlates strongly with carrier lifetime (r = 0.85) but not with the absorption edge (r = −0.33), identifying the regulation of charge carrier dynamics by Fe³⁺ trap states as the origin of the enhancement. The ilmenite structure was preserved after four consecutive reuse cycles. These results show that iron is an effective dopant for NiTiO₃ and identify the optimum composition for subsequent development.