Al₂O₃ layers with thicknesses in the 25–120 nm range were deposited by plasma enhanced atomic layer deposition at 70 °C. Trimethylaluminum was used as organometallic precursor, O₂ and H₂O as oxidant agents and Ar as a purge gas. The deposition cycle consisted of 50 ms TMA pulse/10 s purge time/6 s of plasma oxidation at 200 W/10 s purge time. The optical constants and thicknesses of the grown layers were determined by spectroscopic ellipsometry, while the roughness was measured by atomic force microscopy, giving RMS values in the 0.29–0.32 nm range for films deposited under different conditions and having different thicknesses. High transmittance, ~90%, was measured by UV–Vis spectroscopy. X-ray photoelectron spectroscopy revealed that, with both types of oxidants, the obtained films are close to stoichiometric composition and, with high purity, no carbon was detected. Electrical characterization showed good insulating properties of both types of films, though the H₂O oxidant leads to better I-V characteristics.

Thermal atomic layer deposition (TALD) and plasma atomic layer deposition (PALD) were used for producing thin NiO _x films from nickel(II) acetylacetonate Ni(acac)₂, employing different oxidizing agents (deionized water H₂O, ozone O₃, and molecular oxygen O₂). The films were deposited at 300 °C (TALD) and 220 °C (PALD) over glass substrates; their physical and chemical properties were considerably influenced by the choice of oxidizing agents. In particular, ALD(H₂O) samples had a low growth per cycle (GPC) and a high concentration of defects. The best NiO _x parameters were achieved with PALD(O₂), featuring high GPC (0.07 nm/cycle), high optical transparency in the visible region, electrical resistivity (1.18 × 10⁴ Ω·cm), good carrier concentration (8.82 × 10¹³ cm^-3), and common mobility (5.98 cm²/V·s). The resulting NiO _x films are polycrystalline and homogeneous in thickness and composition. According to ultraviolet photoelectron spectroscopy (UPS), work function φ and the valence band maximum E _V can be tuned by the choice of the coreactant employed, with variations of up to ∼1 eV between TALD and PALD synthesis. Our results suggest that PALD permits one to achieve a better energy band alignment of NiO _x and CsFAMAPbBrI perovskite, which is promising for solar cell applications.

Graphitic carbon nitride (g-C₃N₄) is emerging as one of the most promising non-metallic semiconductors for the degradation of pollutants in water by photocatalytic processes. Its exceptional reduction–oxidation (redox) potentials and adequate band gap of approximately 2.7 eV give it the ability to absorb in the visible light range. However, the characteristic sensitivity to light absorption is limited, leading to rapid recombination of electron–hole pairs. Therefore, different strategies have been explored to optimize this charge separation, among which the formation of heterostructures based on g-C₃N₄ is highlighted. This review addresses recent advances in photocatalysis mediated by g-C₃N₄ heterostructures, considering the synthesis methods enabling the optimization of the morphology and active interface of these materials. Next, the mechanisms of charge transfer are discussed in detail, with special emphasis on type II, type S, and type Z classifications and their influence on the efficiency of photodegradation. Subsequently, the progress in the application of these photocatalysts for the degradation of water pollutants, such as toxic organic dyes, pharmaceutical pollutants, pesticides, and per- and polyfluoroalkyl substances (PFAS), are analyzed, highlighting both experimental advances and remaining challenges. Finally, future perspectives oriented towards the optimization of heterostructures, the efficiency of synthesis methods, and the practical application of these in photocatalytic processes for environmental remediation.

The capacity of untreated cotton stalk to remove and adsorb Cu²⁺ ions in synthetic and natural aqueous solutions was evaluated. The influence of three sensitive parameters of the adsorption process—solution pH, adsorbent dosage, and contact time—on the percentage of Cu²⁺ removal in agricultural wastewater, livestock wastewater, and synthetic samples was studied. Physicochemical and morphological properties were studied using thermogravimetry, Fourier infrared spectrophotometry, and scanning electron microscopy. The elemental composition, proximal composition, zero charge point, and acid–base sites were determined. In addition, kinetic studies were performed, and the adsorption equilibrium was analyzed. The optimum conditions for Cu²⁺ adsorption were the following: solution pH = 5.5, adsorbent dosage of 0.6 g, and contact time of 60 min. Under these conditions, the percentage of Cu²⁺ removal in synthetic samples was 66.5% when the initial copper concentration was 50 mg/L. The removal percentage in agricultural and livestock wastewater samples was 87.60% and 85.05%, respectively, when the initial copper concentration was 25 mg/L. The adsorption data are consistent with the Freundlich isotherm model, which achieved a quadratic fit of 0.991 compared to 0.5542 for the Langmuir model. The experimental results indicate that the adsorption adequately fits the pseudo-second-order kinetic model. The results suggest that cotton stalks are a promising adsorbent for the ecological and economical removal of Cu²⁺ in wastewater. This research, therefore, provides relevant information that contributes to the sustainable management of agricultural waste and instills hope for a reduction in water pollution from heavy metals derived from agricultural activities.