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This work focuses on the preparation of aerogel composite beads based on Zn(II)-crosslinked alginate and loaded with different percentages of AgNPs using a simple approach. The obtained samples were evaluated in two different applications: the first application consists in their use as catalysts for the reduction of MB, MO, OG and CR dyes in a simple and binary system under the presence of NaBH4. For this, several parameters affecting the catalytic behavior of these catalysts have been investigated and discussed such as the catalyst mass, AgNPs content, dye nature, and the selectivity of the catalyst in a binary system. The second application concerns their antibacterial activities towards two Gram-negative bacteria Escherichia coli (ATCC 25922), and Pseudomonas aeruginosa (ATCC 27853), and a Gram-positive bacteria Staphylococcus aureus (ATCC 25923). The physico-chemical properties of different samples were characterized by XRD, FTIR, SEM/EDS, and TGA analysis. The obtained results confirmed the presence of AgNPs on a highly porous alginate structure. The dispersion of a high percentage of AgNPs leads to the formation of nanoparticles on the outer surface of the alginate which led to their leaching after the catalytic test, while the composite having a low percentage of AgNPs showed good results through all dyes without leaching of AgNPs. For the antibacterial application of the different samples, it was shown that a composite with a higher percentage of AgNPs was the most effective against all bacteria. [ABSTRACT FROM AUTHOR]

Interest in the biosynthesis of nanoparticles has increased in the last era by researchers. Nanoparticles have several applications in different fields like optoelectronics, magnetic devices, drug delivery, and sensors. Nanoparticle synthesis by green methods is safe for the environment and should be explored and encouraged popularly since various plants' have the high extent to form these nanoparticles. Worldwide, UV spectroscopy, X-ray diffraction, Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Dynamic Light Scattering (DLS), Atomic Force Microscopy (AFM) besides Fourier Transform Infrared Spectroscopy (FTIR) are used in many ways for characterize nanoparticles. The most advantageous use of AgNPs is their great attribution to be used as antimicrobial agents. Finally, concept of AgNPs synthesis is deserved to be the modern technical and medical concern. The current review shows a complete comprehensive and analytical survey of the biosynthesis of AgNPs with a particular focus on their activities as antimicrobials and the possible theories of their effect on the microbial cell and all influenced secondary metabolites. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Ag0@CeO 2 @MCM-41 catalyst was prepared by calcination. • Reduction of MO, OG, MB, 4-NP, CR organic pollutants in a simple and binary system under low concentration of NaBH 4 was investigated. • The effect of the reducing agent on the behavior of the catalyst in a binary system was investigated. • The Ag-Ce-MCM-2 catalyst was stable and reusable with high conversion of MB dye during seven consecutive cycles. In this work, mesoporous silica MCM-41 was prepared by hydrothermal route, and the obtained as-synthesized material (CTA-MCM-41) was modified by two different methods using silver and cerium assisted by thermal treatment. The modified materials were characterized by XRD, FTIR, XRF, XPS, nitrogen sorption measurements at −196 °C, SEM, and TEM analyses. The modified materials were tested as catalysts in a simple and binary system via the reduction reaction of Methylene Blue (MB), Congo Red (CR), 4-Nitrophenol (4-NP), Methyl Orange (MO), Orange G (OG) in the presence of NaBH 4. The effect of the nanoparticles size, their dispersions, the nature of the organic pollutant, the initial concentration of the organic pollutant, and the concentration of the reducing agent NaBH 4 have been studied and discussed. The obtained results confirmed that the preparation method plays an important role in the content and nature of nanoparticles, their sizes, their dispersions, and also on their catalytic performance. The Ag-Ce-MCM-2 material was selected as the best catalyst due to the synergistic effect between AgNPs and CeO 2. The rate constant calculated in the simple system for the different pollutants was as follows: 0.1829 s−1, 0.1762 s−1, 0.0606 s−1, 0.0585 s−1, 0.0556 s−1 for MO, OG, MB, 4-NP, CR, respectively. The reduction in a binary system containing CR and MB or MO and MB was in competition, in which the CR or MO degrades together with the MB dye. Whereas for the other binary systems containing 4-NP/MB or OG/MB, the catalyst Ag-Ce-MCM-2 was more selective towards the MB dye. This catalyst demonstrated efficiency and reusability across different cycles, in which the conversion of the MB dye was complete in each reuse. [ABSTRACT FROM AUTHOR]