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A nano-silica-AgNPs composite material is proposed as a novel antifouling adsorbent for cost-effective and ecofriendly water purification. Fabrication of well-dispersed AgNPs on the nano-silica surface, designated as NSAgNP, has been achieved through protein mediated reduction of silver ions at ambient temperature for development of sustainable nanotechnology. The coated proteins on AgNPs led to the formation of stable NSAgNP and protected the AgNPs from oxidation and other ions commonly present in water. The NSAgNP exhibited excellent dye adsorption capacity both in single and multicomponent systems, and demonstrated satisfactory tolerance against variations in pH and dye concentration. The adsorption mainly occurred through electrostatic interaction, though π-π interaction and pore diffusion also contributed to the process. Moreover, the NSAgNP showed long-term antibacterial activity against both planktonic cells and biofilms of Gram-negative Escherichia coli and Pseudomonas aeruginosa. The antibacterial activity of AgNPs retarded the initial attachment of bacteria on NSAgNP and thus significantly improved the antifouling properties of the nanomaterial, which further inhibited biofilm formation. Scanning electron and fluorescence microscopic studies revealed that cell death occurred due to irreversible damage of the cell membrane upon electrostatic interaction of positively charged NSAgNP with the negatively charged bacterial cell membrane. The high adsorption capacity, reusability, good tolerance, removal of multicomponent dyes and E. coli from the simulated contaminated water and antifouling properties of NSAgNP will provide new opportunities to develop cost-effective and ecofriendly water purification processes.

Fabrication of nanofibrous biomaterials based on natural materials (collagen, gelatin, etc.) through various techniques is an important research topic. Electrospinning, a well-established technique for nanofiber production has also been extended for producing nanofibrous structures of natural materials. Collagen nanofiber production utilizes hexafluoro isopropanol (HFIP) as a solvent for electrospinning. Research efforts are now focused on replacing HFIP with an environmentally benign solvent. In this study, electrospinning of Type I collagen of bovine skin with polycaprolactone (PCL) as a blend and an environmentally benign solvent, acetic acid, was carried out. The samples produced were subjected to contact angle measurements, porosity estimation, SEM, FTIR, TGA, and DSC. Nanofibers in the range of 100-200 nm were produced with an optimum porosity of 60%. The instrumental analyses confirm the physical interaction between collagen and PCL. Electrospinning of collagen in an environmentally benign solvent has been carried out and its usage in tissue engineering is being investigated by our research group.Correspondence to: A. Gnanamani (gnanamani3@gmail. com) and V. R. Giridev (Giridev vrgiridev@yahoo.com).

Activated carbon composite prepared from rice husk using phosphoric acid activation has been studied through precarbonization of the precursor followed by chemical activation. This method can produce carbons with micro- and mesoporous structure. The ratio of chemical activating agent to precarbonized carbon was fixed at 4.2. The surface area, pore volume, and pore size distribution of carbon composite samples activated at three different temperatures (700, 800, and 900 °C) were measured using nitrogen adsorption isotherms at 77 K. The pore-opening and pore-widening effects occurred simultaneously during the process, as evidenced by scanning electron micrographs. The X-ray diffraction curve revealed the evolution of crystallites of carbon and silica during activation at higher temperature. The FTIR spectrum also provided evidence for the presence of silica in the carbon composite. The proper choice of the preparation conditions had an influence on the micropore and mesopore volumes of the activated carbon composite, which were 0.1187 and 0.2684 cm3/g, respectively. The production yield was observed to decrease with increasing activation temperature.

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