Reversible formation of gold crystallites takes place in methanol-swollen cross-linked polymers of diallyldimethylammonium chloride. Metal particles are generated in air-saturated gels via the photoreduction of Au(III) complexes. Oxidation of the crystallites proceeds through a dark reaction that regenerates the Au(III) species. The particle generation process remains completely reversible throughout several formation and decay cycles, indicating that this gel system behaves in a photoresponsive fashion.

AuCl4 - ions are transformed into Au crystallites via two consecutive photoreactions inside cross-linked polymers of diallyldimethylammonium chloride swollen with methanol. The photoreactions are markedly influenced by the gel matrix, which facilitates pathways not observed in homogeneous solutions and controls the direction of propagation. Initially, the reactions are repressed by air, but at longer times they are aided by products from the O2-reduction. The first process is an efficient monophotonic chain reduction of AuCl4 - with chain lengths in excess of 80 and an atypical pseudofirst-order termination. Kinetic data from fully swollen gels is understood in terms of a mechanism involving solution reactions of ·CH2OH radical chain carriers. Light-absorbing products of the first photoreaction, believed to be gold clusters, initiate the second process that yields metal particles. Several common kinetic features are displayed by both photoreactions. However, generation of Au crystallites takes place via an unusual biphotonic chain reaction, with reaction rates that are correlated to the number of particle formation and decay cycles.

Reductive dehalogenation of 1,1,2-trichlorotrifluoroethane (CFC 113) takes place upon illumination of air-free suspensions of TiO2 particles containing formate ions. Chloride ions and 1,2-dichlorotrifluoroethane (HCFC 123a) are the main reaction products. Reaction rates increase with increasing concentration of CFC even beyond the solubility limit of the Freon in water. Evidence is presented that a chain transformation of the Freon takes place in formate solutions. The results are explained assuming that reduction of the Freon proceeds via a radical chain mechanism, which involves participation of CFC and formate species located on as well as next to the oxide surface.

Giant reed is an invasive plant of riparian habitats throughout California and the United States. Glyphosate is approved for controlling giant reed in California. Sources indicate that 1.5% to 5% glyphosate solutions are effective at controlling giant reed. There is little published data on the relative efficacy of different concentrations of glyphosate which can be used to select an appropriate application regime for California habitats. We conducted two field experiments to test the hypothesis that glyphosate concentrations of 1.5%, 3%, and 5% applied as foliar sprays were equally effective at killing giant reed plants. Leaf chlorophyll content and the proportion of living stems declined significantly following treatment with 1.5% or greater solutions of glyphosate. New stems were observed the spring following treatment for plants treated with 1.5% glyphosate. No new stems were observed for plants treated with either 3% or 5% glyphosate. A treatment that included ''bending and breaking'' stems prior to treatment with 5% glyphosate provided control similar to 5% glyphosate alone. There was no there evidence that plants sprayed with only a mixture of the surfactant (Agridex), water, and a marking dye were affected beyond the short-term. These results indicate that 3% or 5% foliar applications with glyphosate were the most effective and consistent treatments for killing giant reed with a single late-season application. This result is especially important if the goal of the treatment program is to minimize the number of treatments, thus reducing labor costs and minimizing impacts on sensitive habitats by reducing the number of site visits. Nomenclature: Giant reed, Arundo donax L. ABKDO.

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