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Chitosan was used in the sol-gel synthesis of zinc oxide nanoparticles (ZnO NPs) as a capping agent in order to control the size, morphology, optical bandgap, photocatalytic efficiency, and antimicrobial activity. Different chitosan sources were used for the sol-gel synthesis of ZnO NPs, namely chitosan of shrimp shells, crab shells, and Streptomyces griseus bacteria. The photocatalytic efficiency was studied by using the methylene blue (MB) photodegradation test, and the antibacterial activity of the different types of ZnO NPs was investigated by the agar well diffusion technique. The particle size of ZnO NPs varied between 20 and 80 nm, and the band gap energy ranged between 2.7 and 3.2 eV. Due to the different chitosan sources, the ZnO NPs showed different antibacterial activity against Listeria innocua, Bacillus Subtiliis, Staphylococcus Aureus, Salmonella Typhimurium and Pseudomonas Aeruginosa. The ZnO NPs with lower band gap values showed better antibacterial results compared to ZnO NPs with higher band gap values. The MB dye removal of ZnO (shrimp shells), ZnO (crab shells), and ZnO (Streptomyces griseus) reached 60%, 56%, and 44%, respectively, at a contact time of 60 min, a low initial MB dye concentration of 6 × 10−5 M, a solution temperature of 25 °C, and a pH = 7.

This paper investigates the chemical and crystal structural properties of sand dunes of El-Oued region from the northeast Sahara of Algeria. By using of Fourier-transform infrared (FT-IR) spectroscopy, X-ray fluorescence (XRF) and X-ray diffraction (XRD) we show that El-Oued sand dunes are composed mainly of 97.6% α-quartz (SiO 2 ) and 0.56% calcite (CaCO 3 ). Very low concentrations of some oxides as Al 2 O 3 , Fe 2 O 3, MgO and trace elements impurities were also found. The calculated crystallinity index CI = 0.975 confirm the highly crystalline nature of quartz. From the X-ray diffraction data, structural parameters of quartz and calcite minerals were determined. Quartz grains were found to have a hexagonal crystal structure with lattice parameters of a = b = 4.907 Å and c = 5.401 Å and calcite grains have a trigonal crystal structure with a = b = 4.977 Å and c = 17.04 Å. The calculated lattice parameters were similar to those of standard references. The crystallite sizes of quartz and calcite were estimated to be nanometric.

The novel synthesis of MgO from Laurus nobilis L. leaves was prepared using the green synthesis method. It is using direct blending process to decorate MgO/PEG nanocomposite to enhance the photodegradation properties and examine its physical properties using diverse characterization techniques, including XRD, FTIR, SEM, EDX, and UV–Vis. X-ray diffraction reveals a cubic phase of MgO with a 37-nm grain size. SEM images confirm spherical nanoparticles with a diameter size of 22.9 nm. The optical energy gap of MgO NPs was 4.4 eV, and the MgO/PEG nanocomposite was 4.1 eV, which made it an efficient catalyst under sunlight. The photocatalytic activity of Rose Bengal (RB) and Toluidine Blue (TB) dyes at 5 × 10 −5  mol/l dye concentration indicates excellent degradation efficiencies of 98% and 95% in 120 min, respectively, under sunlight irradiation. MgO/PEG is an excellent candidate nanocomposite for applications of photodegradation and could be used for its potential capability to develop conventionally used techniques.

Dye pollution resulting from the discharge of untreated wastewater has become a major environmental concern. In this study, we propose a green and cost-effective approach for the photocatalytic degradation of dye pollutants using a nanocomposite (NC) of manganese oxide (Mn 3 O 4 ) modified with polyvinylpyrrolidone (PVP). The Mn 3 O 4 nanoparticles (NPs) were synthesized through a green method using a biogenic extract of Pistacia lentiscus leaves. The resulting Mn 3 O 4 NPs were then modified with PVP, a non-ionic polymer, to enhance their stability and catalytic performance. The synthesized Mn 3 O 4 /PVP NC was characterized using various analytical techniques, including Fourier transform infrared spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy. The findings showed that the Mn 3 O 4 NPs and Mn 3 O 4 /PPV NC exhibit spherical morphology with an average size of 37 nm and 45 nm, respectively. The Mn 3 O 4 NPs and Mn 3 O 4 /PVP NC exhibited optical bandgap energies of 1.8 eV and 1 eV, indicating the effective use of these NPs as photocatalysts. The nanocomposite exhibited exceptional catalytic performance in degrading bromophenol blue (BPB) and ortho-toluidine blue (O-TB), achieving degradation rates of 98% and 95% within 75 minutes. In comparison, Mn 3 O 4 NPs showed lower efficiencies with approximately 14% degradation for BPB and 6% for O-TB. Optimal conditions for dye degradation and subsequent cycles were determined, and first-principles calculations revealed insight into the adsorption energy between the dyes and the Mn 3 O 4 /PVP surface. This study highlights the potential of Mn 3 O 4 /PVP nanocomposite as an effective and eco-friendly catalyst for dye pollutant degradation, offering a promising solution for wastewater treatment across industries.

This study reports the successful green synthesis of ZnO nanoparticles (NPs) utilizing an aqueous leaf extract of Olea europea L. The biogenic ZnO NPs were dreied at 100 °C and calcined at 450 °C. Their nanoscale dimensions were confirmed by UV-visible spectroscopy, scanning electron microscopy (SEM) revealing a size range of 40–60 nm, and X-ray diffraction (XRD) analysis confirming a hexagonal structure for both calcination processes. The ZnO particle size increased from 18.79 nm at 100 °C to 25.04 nm at 450 °C. The successful eco-friendly synthesis of ZnO NPs was further validated by FT-IR spectroscopy, which identified functional groups on the particle surface. Importantly, the ZnO NPs demonstrated remarkable efficiency in degrading Cephalexin, achieving a degradation rate of 95% for ZnO (100 °C) and 98% for ZnO (450 °C).The corresponding rate constants were determined to be 0.0334 min − 1 and 0.0250 min − 1 , respectively. Treatment with ZnO NPs at varying temperatures (100ºC and 450 ºC) exhibited inhibitory effects on the growth and reproduction of E. coli and S. typhimurium cells. The observed antibacterial activity is attributed to ZnO NPs, with potential mechanisms involving damage to bacterial cell membranes, extrusion of cytoplasmic contents, and the release of antimicrobial ions (Zn 2+ ) and reactive oxygen species (ROS). B. cereus and S. aureus cells treated with 200 µg/ml ZnO at different temperatures revealed varying growth patterns, indicating that ZnO non calcined (dried at 100 ºC) exhibited higher growth inhibition potential compared to ZnO (450 ºC).