title: Sulfonated poly(ether ether ketone)/poly(vinyl alcohol) sensitizing system for solution photogeneration of small Ag, Au, and Cu crystallites.
abstract: Illumination of air-free aqueous solutions containing sulfonated poly(ether ether ketone) and poly(vinyl alcohol) with 350 nm light results in benzophenone ketyl radicals of the polyketone. The polymer radicals form with a quantum yield 0.02 and decay with a second-order rate constant 6 orders of magnitude lower than that of typical alpha-hydroxy radicals. Evidence is presented that the polymeric benzophenone ketyl radicals reduce Ag+, Cu2+, and AuCl4- to metal particles of nanometer dimensions. Decreases in the reduction rates with increasing Ag(I), Cu(II), and Au(III) concentrations are explained using a kinetic model in which the metal ions quench the excited state of the polymeric benzophenone groups, which forms the macromolecular radicals. Quenching is fastest for Ag+, whereas Cu2+ and AuCl4- exhibit similar rate constants. Particle formation becomes more complex as the number of equivalents needed to reduce the metal ions increases; the Au(III) system is an extreme case where the radical reactions operate in parallel with secondary light-initiated and thermal reduction channels. For each metal ion, the polymer-initiated photoreactions produce crystallites possessing distinct properties, such as a very strong plasmon in the Ag case or the narrow size distribution exhibited by Au particles.
authors.affiliation: Department of Chemistry, Auburn University, Alabama 36849, USA.
authors.forename: A S
authors.initials: AS
authors.lastname: Korchev
authors.forename: T S
authors.initials: TS
authors.lastname: Shulyak
authors.forename: B L
authors.initials: BL
authors.lastname: Slaten
authors.forename: W F
authors.initials: WF
authors.lastname: Gale
authors.forename: G
authors.initials: G
authors.lastname: Mills