الفهرس 
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Abstract
One of the greatest challenges in the field of photocatalysis is to devise new catalysts that possess high activity under visible light illumination. This would allow the use of an abundant and green energy source, sunlight, to derive chemical reactions. The objective of the presented project was to study the effect of alloying transition metal oxides TMOs (FeO) with ZnO on the photocatalytic process and find out whether alloying TMOs could introduce active photocatalysts active under visible irradiation or not. In particular, the current study involved preparation of (Fe1-xZnxO at x = 0.75) nanoalloys alone, enhanced by assembling over rGO nanosheets and doped with (Au-Ag) nanoalloys. The activity of the obtained nanomaterials was evaluated through the degradation of Chlorpyrifos (CP) as a model of pesticides. Moreover, the obtained nanomaterials were used as safe antifungal agents in inhibiting the linear growth of Aspergillus niger. Nanosized photocatalysts ZnO NPs, Fe0.25Zn0.75O Nanoalloys, ZnO/rGO and Fe0.25Zn0.75O/rGO nanocomposites were synthesized using Co-precipitation method, GO nanosheets were synthesized using Hummers method, and Au-Ag/Fe0.25Zn0.75O/rGO nanocomposites were synthesized using Microwave method. The as-synthesized samples were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), and UV-Vis spectroscopy. The XRD patterns indicated that all of the as-synthesized photocatalysts were successfully obtained in pure form with the presence of all nanomaterial components with desired ratios. TEM images indicated that all synthesized photocatalysts were obtained in nano size. Band gap energy of the as-synthesized nanomaterials was considered and calculated in the present study by Tauc relation. The obtained band gap values for ZnO, ZnO/rGO, Fe0.25Zn0.75O, Fe0.25Zn0.75O/rGO and Au-Ag/ Fe0.25Zn0.75O/rGO samples recorded 3.26, 3.07, 2.25, 2.14 and 2.01 eV, respectively. Band gap energy of pure ZnO NPs (3.26 eV) and Fe0.25Zn0.75O nanoalloys (2.25 eV) confirms our expectations that alloying TMOs could introduce photocatalysts active under solar irradiation. The photocatalytic activity of the as-synthesized nanomaterials was evaluated by photodegradation of Chlorpyrifos (CP, 100 mg/L) in aqueous ethanol solution under different irradiation sources (UV and Vis). Nevertheless, no effect of the as-synthesized nanomaterials was noticed in both acidic medium (pH = 3) or free pH on the degradation of CP. The degradation was achieved only in basic medium (pH = 11) For the control experiments (pH = 11) under UV and Vis irradiation, the results obtained showed weak degradation values (42.62٪ and 28.20٪) under UV and Vis irradiation, respectively, within 300 min experimental time. ZnO NPs showed weak activity under Vis irradiation with degradation value (61.3٪) compared to (100٪) under UV irradiation within 300 min. Decorating ZnO NPs with rGO nanosheets showed remarkable enhancement in the photocatalytic activity of ZnO NPs as (100٪) of CP was degraded within 120 min under UV irradiation and (78.3٪) was degraded under Vis irradiation within 300 min. The rate constant under UV irradiation The results obtained with Fe0.25Zn0.75O nanoalloys showed good photocatalytic efficiencies for the degradation of CP, where (100٪) was degraded into TCP under UV irradiation within 120 min and (100٪) within 60 min under Vis irradiation. Moreover, Fe0.25Zn0.75O/rGO nanocomposites showed also high and fast photocatalytic activity for degradation of CP as (100٪) was degraded within 100 min under UV irradiation and (100٪) was obtained after 40 min under Vis irradiation. The highest degradation values with short time in the present study were recorded for Au-Ag/Fe0.25Zn0.75O/rGO nanocomposites as (100٪) of CP degraded into TCP within 75 min under UV irradiation and (100٪) under Vis irradiation within 30 min. Antifungal effect of tested nanomaterials (Fe0.25Zn0.75O, Fe0.25Zn0.75O/rGO and Au-Ag/Fe0.25Zn0.75O/rGO) on the linear growth of Aspergillus niger was also examined under three different incubation conditions, complete darkness, continuous fluorescent light and under UV irradiation. The untreated Aspergillus niger (control plates) showed full growth under both complete darkness and after irradiation with UV light for 6.5 hours. The only inhibition in control was noted under continuous fluorescent light condition with negligible percentage (2.22 ٪). On the other hand, the highest inhibition ratio under complete dark condition was observed with Fe0.25Zn0.75O Nanoalloys (2 µg/ml) with inhibition ratio of (34.11 ٪). For experiments occurred under continuous fluorescent light condition, Fe0.25Zn0.75O nanoalloys (2 µg/ml) showed also the highest inhibition for Aspergillus niger with inhibition ratio of (46.66٪). For the case of irradiation to UV light and before incubation in complete darkness, Fe0.25Zn0.75O nanoalloys (2 µg/ml) showed also the highest antifungal activity among several tested nanomaterials with inhibition ratio of about (47.77٪).