Herein, we report a novel single-step hydrothermal synthesis of a photocatalytically stable and magnetically separable g-Fe3O4/RGO nanocomposite in the presence of Averrhoa carambola leaf extract as a natural surfactant for multipurpose water purification application. The Averrhoa carambola leaf extract played a major role in the modification of structural, optical, and electronic properties of the Fe3O4 nanoparticle. At room temperature, the g-Fe3O4/2RGO nanocomposite showed 97% and 76% of Cr­(VI) reduction and phenol degradation, respectively. The higher activity of g-Fe3O4/2RGO was attributed to the in situ loading of RGO, and the synergism developed between RGO and the super magnetic Fe3O4 nanoparticle results in better separation of photoexcited charge carriers (e–/h+) which was concluded from photoluminescence and photocurrent measurements. Further, the g-Fe3O4/2RGO nanocomposite showed better antimicrobial activity against three bacterial pathogens such as Staphylococcus aureous (MTCC-737), Bacillus subtilis (MTCC-736), and Escherichia coli (MTCC-443) compared to GO with respect to a standard antibiotic (30 μg).

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We designed an electrospinning synthesis protocol to obtain in situ, the mesoporous TiO 2 nanofibers, which are surface-decorated with plasmonic AuAg nanoparticles (AuAg-mTNF-H). Such alloy nanoparticles are found to be partially exposed on the surface of the nanofibers. Characterization by HRTEM and EDS confirmed the formation of 1:1 AuAg alloy nanoparticles on the surface of TiO 2 nanofibers with heterojunction at the interfaces. On the basis of electron microscopic characterization, we proposed that, during the formation of the nanofibers, the incorporated metal ions with surface capping of negative charges migrated toward the outer surface of the nascent fibers under the influence of high positive voltage required for electrospinning. As a result, after the subsequent thermal treatment, the crystallization of TiO 2 nanofibers and the formation of alloy nanoparticles took place, leading to the formation of a deep heterojunction through partial embedment of the nanoparticles. The formation of AuAg alloy also restricted the oxidation of Ag, thus making the nanoparticles highly stable in ambient condition. Accordingly, such unique AuAg-mTNF-H photocatalyst shows strong light absorption property covering the entire range of visible wavelengths with stability. The solar light harvesting property of AuAg-mTNF-H was verified by monitoring solar light induced H 2 evolution via water splitting and photodecomposition of MB. In both the cases AuAg-mTNF-H showed excellent H 2 evolution and photodecomposition of dye.

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The antibacterial screening of extracts of the leaves of Finlaysonia obovata with hexane, chloroform and alcohol was carried out against fresh water fish pathogenic bacteria viz., Micrococcus Sp. (multidrug resistant strain), Aeromonas hydrophila, Pseudomonas aeruginosa, Vibrio alginolyticus, Staphylococcus aureus, Escherichia Coli, Edwardsiella tarda by disc-assay method. The hexane and chloroform extracts were found active against four and five pathogens, respectively. The highly active chloroform extract was taken up for fractionations, further screening and isolation of secondary metabolites by chromatographic techniques. The triterpene acid Urs-3beta-hydroxy-12-en-27-oic acid (3), which is very rarely found from plant sources is isolated first time from this plant along with known compounds; Lupeol acetate (1) and beta-Sitosterol (2). This article presents for the first time all the spectral data for Urs-3beta-hydroxy-12-en-27-oic acid (3), which showed moderate activity against four pathogens. This is the first report of antibacterial activity of a triterpene against fish pathogens.