Silver nanoparticles: Green synthesis and their antimicrobial activities.

This review presents an overview of silver nanoparticles (Ag NPs) preparation by green synthesis approaches that have advantages over conventional methods involving chemical agents associated with environmental toxicity. Green synthetic methods include mixed-valence polyoxometallates, polysaccharide, Tollens, irradiation, and biological. The mixed-valence polyoxometallates method was carried out in water, an environmentally-friendly solvent. Solutions of AgNO 3 containing glucose and starch in water gave starchprotected Ag NPs, which could be integrated into medical applications. Tollens process involves the reduction of Ag(NH 3 ) 2 + by saccharides forming Ag NP films with particle sizes from 50-200 nm, Ag hydrosols with particles in the order of 20-50 nm, and Ag colloid particles of different shapes. The reduction of Ag(NH 3 ) 2 + by HTAB (n-hexadecyltrimethylammonium bromide) gave Ag NPs of different morphologies: cubes, triangles, wires, and aligned wires. Ag NPs synthesis by irradiation of Ag + ions does not involve a reducing agent and is an appealing procedure. Eco-friendly bio-organisms in plant extracts contain proteins, which act as both reducing and capping agents forming stable and shape-controlled Ag NPs. The synthetic procedures of polymer-Ag and TiO 2 -Ag NPs are also given. Both Ag NPs and Ag NPs modified by surfactants or polymers showed high antimicrobial activity against Gram-positive and Gram-negative bacteria. The mechanism of the Ag NP bactericidal activity is discussed in terms of Ag NP interaction with the cell membranes of bacteria. Silver-containing filters are shown to have antibacterial properties in water and air purification. Finally, human and environmental implications of Ag NPs to the ecology of aquatic environment are briefly discussed

Poly[aqua(μ-vinyl­phospho­nato)cadmium]

The title compound, [Cd(C2H3O3P)(H2O)]n, was obtained from vinyl­phospho­nic acid and cadmium nitrate. The vinyl groups project into the inter­lamellar space and the structure is held together via van der Waals forces. The Cd2+ ion is six-coordinate and the geometry is best described as distorted octa­hedral, with O—Cd—O angles falling within the range 61.72 (13)–101.82 (14)°. Five of the coordinated oxygen atoms originate from the phospho­nate group and the sixth from a bound water molecule. Cd—O distances lie between 2.220 (3) and 2.394 (2) Å. The water mol­ecule is hydrogen bonded to a phospho­nate oxygen atom