Adsorption-photocatalytic degradation abilities of γ-irradiated chitosan-ZnO-AgNP composite for organic dye removal and antibacterial activity.

We synthesized a γ-irradiated chitosan-ZnO-AgNPs (ICZA) composite by using a simple hydrogels method. We evaluated its adsorption/photocatalytic degradation abilities for the removal of an organic dye and its antibacterial activity. The XRD, SEM, TEM, EDS, and FTIR techniques were used to characterize the obtained samples. Based on the adsorption and degradation of methylene blue (MB) in the dark and under UV light irradiation, the adsorption and the photocatalytic activity of the as-obtained samples were evaluated. The optimum conditions for synthesizing the composite were as follows: contact time of 210 min, a dosage of 2 g/L, MB concentration of 40 mg/L, and a solution pH of 8.0. The ICZA had a high adsorption capacity, which was suitable for removing MB from the aqueous solutions; it showed a maximum adsorption capacity (qm) of 92.59 mg/g. The fit of the adsorption isotherms with the Langmuir model was satisfactory. The photocatalytic degradation ability of the composite was also better than that of other catalysts in the presence of UV light, with an apparent rate constant (kapp) of 3.08 × 10-2. The synthesized ICZA also showed good antibacterial activity against Staphylococcus aureus, with a minimum inhibitory concentration (MIC) and a minimum bactericidal concentration (MBC) of 12.5 g/mL and 50 g/mL under light-incubation and dark-incubation conditions. Finally, we discussed the hypothesized mechanism of the adsorption/photocatalytic activity and antibacterial activity of the ICZA composite in this study.

Photocatalytic degradation of organic dyes on magnetically separable barium hexaferrite as photocatalyst under conditions of visible light irradiation.

In this paper, we present the first attempt to evaluate the role of carboxymethyl cellulose (CMC) as a chelating agent in the sol-gel auto-combustion method of producing barium hexaferrite (BaFe12O19). We also report the application of the system as a photocatalyst for dye degradation. The formation, morphology, and crystalline structure of the synthesized nanoparticles are determined using XRD, SEM, EDS, VSM, FTIR, and TEM techniques. High efficiency under visible light, with a band gap of 1.62 eV and a BET surface of 17.93 m2/g, has been observed for the BaFe12O19 catalyst. The operating parameters, such as reaction time, initial dye concentration, light intensity, reusability, and dye type, are studied. Degradation rates as high as 98.26% (Kapp = 0.082 min-1) and 89.07% (Kapp = 0.0743 min-1) were obtained for cases of methylene blue and malachite green under conditions of visible light irradiations when BaFe12O19 was used. The BaFe12O19 catalyst has been shown to exhibit a high degradation performance for cationic dyes. Furthermore, BaFe12O19 magnetic nanoparticles show excellent reusability for dye degradation because the photocatalyst did not exhibit a significant decrease in its activity even after five runs (81.56%). As a result, the current study confirmed that photocatalytic degradation was a promising technology for saving water and treating wastewater formed from textile dye industries. The technique can be used to study the efficiency of photocatalytic degradation and understand the process of recycling waste effluents under conditions of minimized water use.

Effect of Na and Al doping on ZnO nanoparticles for potential application in sunscreens.

This study investigated the environment-friendly production and characterization of zinc oxide nanoparticles (ZnO NPs) doped with sodium (Na) and aluminum (Al) metals to decrease the photocatalytic activity of ZnO for use in sunscreen. The metal-doped zinc oxide (ZnO) materials were prepared by the microwave method using extracts of Averrhoa carambola, also known as star fruit, as a reducing agent. The effects of metal-ion doping on the crystal structure, morphology, and optical characteristics of ZnO were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX), transmission electron microscopy (TEM), and ultraviolet-visible (UV-Vis) spectroscopy. The sun protection factor (SPF) of the sunscreen formulations containing undoped ZnO, Na-doped ZnO (Na/ZnO), and Al-doped ZnO (Al/ZnO) NPs were found to be 10.10, 25.10, and 43.08, respectively. Therefore, Na/ZnO and Al/ZnO showed increased SPF. Additionally, the prepared nanomaterials and sunscreens were effective against Gram-positive and Gram-negative bacteria and showed antioxidant activities. The methylene blue (MB) degradation was used to evaluate the photocatalytic activities of the undoped ZnO, Na/ZnO, and Al/ZnO NPs, which were found to be 66%, 46%, and 38%, respectively. Therefore, due to the structural defects of ZnO NPs, their photocatalytic activity was decreased with Na- and Al- doping. Additionally, Al/ZnO is an ideal candidate as an ingredient in sunscreens.

Microwave-assisted synthesis of Ag/ZnO nanoparticles using Averrhoa carambola fruit extract as the reducing agent and their application in cotton fabrics with antibacterial and UV-protection properties.

This is the first time Averrhoa carambola fruit extract has been used as a reducing agent to synthesize Ag/ZnO composites for coating cotton to develop antibacterial activity and UV protection under domestic microwave irradiation. The effects of the molar concentration of silver nitrate solutions, applied power, reaction duration, and pH on the yield of nanoparticles were determined. The treated fabrics were subjected to the investigation of surface morphology and chemical structure using SEM and EDX techniques, respectively. The antibacterial activity of the ZnO NPs and the Ag/ZnO nanocomposite coated on cotton fabric was evaluated against E. coli and S. aureus using the agar well diffusion method. The results revealed good antibacterial activity in the cotton fabric treated with the Ag-doped ZnO composite. The stability of the Ag/ZnO nanocomposite coated fabrics was determined by a wash durability test, the results of which demonstrated that this fabric could retain good antibacterial activity even after 20 wash cycles. The UV-blocking capacity of the treated fabrics was evaluated based on the ultraviolet protection factor (UPF) value determined in the range of 280-400 nm. The UPF value determined for the Ag/ZnO-coated fabric was 69.67 ± 1.53, which indicated an excellent ability to block UV radiation. Collectively, these results demonstrated the Ag/ZnO nanocomposite prepared in the present study as a promising material for preparing textiles with good antibacterial activity and UV protection.