Quantum bandgap buffer layers can improve sunlight absorption in the short wavelength region, hence improving the performance of CIGS solar cells. In this study, we use numerical modelling to determine the impact of various buffer layers' electrical characteristics on the performance of CIGS thin film photovoltaic devices, particularly, carrier concentration and the quantum effect. As well Ag₂S buffer layer has been experimentally examined to fulfilment its effect in term of bulk and quantum bandgap. Experimental results depicted that, Ag₂S QDs has polycrystalline nature of films, with smooth surface roughness, and average diameter 4 nm. Meanwhile, a simulation revealed that the Fermi level of the (n-buffer layer) material shifts closer to the conduction band with an increase in carrier concentration. The findings indicate that, a buffer layer with a wider bandgap and carrier concentration is an essential demand for achieving a device with a higher conversion efficiency and a broader bandgap-CBO window. It was attributed to beneficial synergistic effects of high carrier concentration and narrower depletion region, which enable carriers to overcome high CBO barrier. Most importantly, modelling results indicate that the optic-electrical characteristics of the buffer layer are critical in determining the progress of a CIGS solar cell.

The current study investigates Bi₂S₃ thin films coated on ZnO NRAs with varying cationic concentrations through ionic layer adsorption and reaction (SILAR) technique. XRD patterns reveal that Bi₂S₃ is successfully synthesised and exhibits orthorhombic structure on the wurtzite ZnO NRAs. The band gap energy (E_g) of Bi₂S₃/ZnO NRAs shows a notable red shift with increasing cationic concentration. The photocurrent density increases significantly with increasing concentration from 1 mM to 3 mM before decreases at higher concentration due to agglomeration of Bi₂S₃ NPs and formation of recombination centres. The hybrid photoanode Bi₂S₃/ZnO NRAs at 3 mM exhibits the highest photocurrent value (1.92 mA cm⁻²), which is about six times greater than that of plain ZnO NRAs (0.337 mA cm⁻²). The high photoconversion efficiency value of 1.65% versus 0.5 V Ag A⁻¹g⁻¹C⁻¹l⁻¹ is obtained by Bi₂S₃/ZnO NRAs (3 mM) in comparison with pristine ZnO NRs, mainly due to the stepwise band alignment edge and significant enhancement of morphological and optical properties. The study reveals that controlling the cationic concentration can potentially improve the photoconversion efficiency.

This research focuses on improving the photoelectrochemical performance of binary heterostructure Ag₂S/ZnO NRs/ITO by manipulating synthesis conditions, particularly the concentrations of sliver nitrate AgNO₃ and thiourea CS(NH₂)₂. The photoelectrochemical performance of Ag₂S/ZnO nanorods on indium tin oxide (ITO) nanocomposite was compared to pristine ZnO NRs/ITO photoanode. The hydrothermal technique, an eco-friendly, low-cost method, was used to successfully produce Ag₂S/ZnO NRs at different concentrations of AgNO₃ and CS(NH₂)₂. The obtained thin films were characterized using field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), ultraviolet-visible spectroscopy (UV-vis), and photoelectrochemical studies (PECs). We observed that there was an enhancement in absorbance in the visible region and effective photoelectron transfer between the Ag₂S/ZnO NRs/ITO photoelectrode and the electrolyte Red-Ox when illuminated with 100 mW cm⁻². Increasing the concentration of AgNO₃ caused a remarkable decrease in the optical bandgap energy (E_g) values. However, we noticed that there was an unstable trend in E_g when the concentration of CS(NH₂)₂ was adjusted. The photoelectrochemical studies revealed that at a bias of 1.0 V, and 0.005 M of AgNO₃ and 0.03 M of CS(NH₂)₂, the maximum photocurrent of the Ag₂S/ZnO NRs/ITO photoanode was 3.97 mA/cm², which is almost 11 times that of plain ZnO nanorods. Based on the outcomes of this investigating, the Ag₂S/ZnO NRs/ITO photoanode is proposed as a viable alternative photoanode in photoelectrochemical applications.

A simple and efficient approach to preparing highly efficient and reusable NiO@SBA-15 nanocatalysts for the oxidation of cyclohexane to produce ketone-alcohol (KA) oil was reported. These nanocatalysts were prepared by the dispersion of NiO NPs into SBA-15 using a coordination-assisted grafting method. In this approach, four commercially available nickel salts were immobilized into amino-functionalized SBA-15. After washing and calcination, four new nanocatalysts were obtained. The high dispersion of NiO NPs into SBA-15 was confirmed by HR-TEM and XRD. Different oxidants such as O₂, H₂O₂, t-butyl hydrogen peroxide (TBHP), and meta-Chloroperoxybenzoic acid (m-CPBA) were evaluated. However, m-CPBA exhibited the highest catalytic activity. Compared to different catalysts reported in the literature, for the first time, 75–99% of cyclohexane was converted to KA oil over NiO@SBA-15. In addition, the cyclohexane conversion and K/A ratio were affected by the reaction time, catalyst dose, Ni content, and NiO dispersion. Moreover, NiO@SBA-15 maintained a high catalytic activity during five successive cycles.

The valorisation of waste from rose-based industrial products produces value-added substances and paves the way for advanced composites. The rose waste generated from the essential oil industry of the Taif rose (Rosa damascena trigintipetala Dieck) is significant, and its management or disposal is a source of concern. In this study, it was valorised to produce a value-added nanomaterial. The synthesis of biochar nanoparticles via high-energy ball milling has gained tremendous research interest in recent times because of its low cost and eco-friendliness. Ball milling is a solvent-free technology with strong potential for waste volatilisation and eco-sustainability through the production of engineered biochar nanoparticles. Different biochar samples were produced and characterised to harness the synergistic combination of biochar production and ball milling. They were prepared at a constant pyrolysis temperature of 300 °C by varying the pyrolysis times for 2 h, 5 h, and 10 h. The characterisation results showed that pyrolysis confirms a high content of carbon, minerals, graphitic structure, novel morphology and chemical characteristics attached to the biochar surface controlled by different pyrolysis durations. These properties were further enhanced by ball milling for 10 h. The results showed that ball milling enhanced the porosity, surface area, surface functional groups, visible light absorption, crystallinity, and carbon content, and these were accompanied by a reduction in the particle size and mineral impurities. The engineered biochar can be an important tool, with promising potential in novel composites for water purification and energy harvesting.

Model photocatalysts composed of titanium dioxide (TiO2) nanoparticles were prepared to assess the impact of different synthesis techniques on their photocatalytic activity towards methylene blue. TiO2 nanoparticles were synthesized using three distinct methods: high-energy ball-milling (HEBM), sonication, and pulse laser ablation. The engineered photocatalysts exhibited varying morphology, crystallinity, and optical properties, as evidenced by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The synthesis techniques notably resulted in different particle sizes, with mean sizes of 121.2 nm, 25.53 nm, and 22.38 nm, and corresponding crystallite sizes of 24.86 nm, 33.5 nm, and 34.4 nm for HEBM, sonication, and pulse laser ablation, respectively. All of the synthesized TiO2 nanoparticles displayed significantly enhanced photocatalytic activity under low-intensity UV light in comparison to the TiO2 raw material. However, the choice of synthesis method had a substantial impact on photocatalytic performance. Specifically, TiO2 prepared via ultrasonication and continuous ball milling exhibited the highest photocatalytic activity among the methods. The most rapid degradation rate (K = 0.0049 min^(-1)) was observed for TiO2 produced through continuous ball milling and ultrasonication. These findings indicate that the synthesized TiO2 nanoparticles hold potential for use as catalysts for degrading various types of organic pollutants.