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.

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.