Preparation of noble metal supported carbon electrodes using photochemically reduced heteropolyanions in composite films

Silver polymer nanocomposites by photoreduction of AgNO3 and simultaneous photocrosslinking of the acrylic matrix: effect of PVP on Ag particle formation

We studied the effect of poly-N-vinylpyrrolidone (PVP) and its concentrations on the photoinduced formation of silver nanoparticles (Ag NPs) as well as Ag-polymer nanocomposites. First, the effect of PVP concentration on the photoinduced reduction of Ag nitrate (AgNO3) in solution was studied by UV-Vis absorption spectroscopy monitoring the plasmon band of Ag. Dynamic light scattering (DLS) results showed that Ag NPs formed in the presence of stabilizer up to 4 wt% were narrower; the size distribution was also narrower. The PVP also had a significant influence on the formation of polymer nanocomposites by simultaneous photoinduced synthesis of NPs and polymerization of the acrylic matrix; NPs embedded in the crosslinked polymer were well dispersed, as detected by field-emission scanning electron microscopy (FESEM), and showed an average diameter of 20 nm.

Ranking the lacunary (Bu4N)9[H[alpha2-P2W17O61]] polyoxometalate's stabilizing ability for Ir(0)(n) nanocluster formation and stabilization using the five-criteria method plus necessary control experiments

The primary goal of the present studies is to rank the monoprotonated, lacunary Wells-Dawson-type polyoxometalate [H[alpha2-P2W17O61]](9-) as a stabilizing anion for the formation and subsequent stabilization of Ir(0)(n) nanoclusters in acetone using the five-criteria method developed previously ( Ozkar , S. ; Finke , R. G. J. Am. Chem. Soc. 2002 , 124, 5796 ). A related goal is to compare this potentially tetradentate, three W-O(-) plus one W-OH ligand [H[alpha2-P2W17O61]](9-) system to the nanocluster formation and stabilization abilities of the present "gold standard" polyoxometalate, [P2W15Nb3O62]9-, with its established tridentate, three Nb-O-Nb ligating system. A comprehensive table of 54 references at present examining polyoxometalates (POMs) as additives/stabilizers of nanoclusters is also provided as Table S1 of the Supporting Information . To accomplish the above-noted two main goals, the organic-solvent-soluble tetrabutylammonium salts, (Bu4N)8.4[H1.6[alpha2-P2W17O61]] x 1.4H2O, (Bu4N)9[H[alpha2-P2W17O61]], and (Bu4N)9[P2W15Nb3O62] were prepared and their basic structures (by IR) and purity (by 31P NMR, plus elemental analysis where appropriate) were determined. The parent Wells-Dawson POM (Bu4N)6[alpha-P2W18O62] was also prepared, characterized, and then used as a control of a polyoxometalate with little surface anionic charge density, one therefore expected to be a poor stabilizer for at least metal(0)(n), overall neutral core, nanoclusters. Also prepared and characterized was (Bu4N)4[H3[PW11O39]], but its attempted deprotonation by (Bu4N)OH with direct 31P NMR monitoring did not yield a clean product by 31P NMR, so studies with this second lacunary POM were deemphasized. The resultant POMs of known composition, protonation state, and thus overall charge were then evaluated by the five criteriathe one presently available methodfor their ability to promote the kinetically controlled formation, stabilization, and subsequent catalytic activity of prototype Ir(0)(n) nanoclusters. A number of additional control experiments necessary to provide confidence in the results are also reported. One main finding is that the efficacy of the POMs studied herein, as stabilizers for Ir(0)(n) nanoclusters in acetone solvent, is [P2W15Nb3O62]9- > [H[alpha2-P2W17O61]]9- >> [alpha-P2W18O62]6- approximately [H3[PW11O39]]4-, the potentially tetradentate, lacunary [H[alpha2-P2W17O61]]9-proving somewhat less efficacious as a stabilizer than the tridentate Nb-O-Nb containing [P2W15Nb3O62]9-POM. Another finding is that the degree of protonation and the overall charge of the POM matter, the more highly charged [H[alpha2-P2W17O61]]9- POM being a better stabilizer then the more protonated, less charged [H2[alpha2-P2W17O61]]8-. Two additional important findings are better insights into the inherent errors underlying three of the five criteria, and thus the use of the five-criteria method itself, and further evidence supporting the hypothesis that future studies of direct measurements of nanocluster agglomeration rate constants k3 and k4 ( Ott , L. S. ; Finke , R. G. Chem. Mater. 2008 , 20, 2592 - 2601 ) should prove valuable.

Photochemically reduced polyoxometalate assisted generation of silver and gold nanoparticles in composite films: a single step route

A simple method to embed noble metal (Ag, Au) nanoparticles in organic–inorganic nanocomposite films by single step method is described. This is accomplished by the assistance of Keggin ions present in the composite film. The photochemically reduced composite film has served both as a reducing agent and host for the metal nanoparticles in a single process. The embedded metal nanoparticles in composites film have been characterized by UV–Visible, TEM, EDAX, XPS techniques. Particles of less than 20 nm were readily embedded using the described approach, and monodisperse nanoparticles were obtained under optimized conditions. The fluorescence experiments showed that embedded Ag and Au nanoparticles are responsible for fluorescence emissions. The described method is facile and simple, and provides a simple potential route to fabricate self-standing noble metal embedded composite films.