%0 Journal Article %J Journal of Photochemistry and Photobiology a-Chemistry %D 2006 %T Using silica films and powders modified with benzophenone to photoreduce silver nanoparticles %A Eustis, Susie %A Krylova, G. %A Smirnova, N. %A Eremenko, A. %A Tabor, C. E. %A Huang, Wenyu %A El-Sayed, Mostafa A %X Porous silica (SiO2 films and powders), modified with benzophenone (BP), facilitates the formation of stable sliver nanoparticles by taking advantage of the solid supported photosensitizer. The silica serves as a carrier for the BP into an aqueous solution and its subsequent removal. Benzophenone, bound to a silica film, was able to reduce silver ions to generate nanoparticles in solution, while silica powder with bound BP generates silver nanoparticles that are attracted to the silica. Silver nanoparticles are also fabricated in porous silica films by incorporating silver ions into the films before casting and then irradiating the film in a solution containing BP. From pH studies, it is concluded that the ketyl-radicals and anion-radicals of BP and IPA both take part in the reduction of silver ions. These synthetic studies provide a new photochemical reduction method by immobilizing the reactant on a silica surface allowing generation of silver nanoparticles in solution attached to powders or inside a film for catalytic applications or increased conductivity of silica films. (c) 2006 Elsevier B.V. All rights reserved. %B Journal of Photochemistry and Photobiology a-Chemistry %V 181 %P 385-393 %8 Jul %@ 1010-6030 %G eng %M WOS:000238963700034 %R 10.1016/j.jphotochem.2005.12.024 %0 Journal Article %J Photochemical & Photobiological Sciences %D 2005 %T Growth and fragmentation of silver nanoparticles in their synthesis with a fs laser and CW light by photo-sensitization with benzophenone %A Eustis, Susie %A Krylova, G. %A Eremenko, A. %A Smirnova, N. %A Schill, A. W. %A El-Sayed, Mostafa A %X The photo-sensitization synthetic technique of making silver nanoparticles using benzophenone is studied using both a laser and a mercury lamp as light sources. The power and irradiation time dependence of the synthesized nanoparticle absorption spectra and their size distribution [as determined by transmission electron microscopy (TEM)] are studied in each method and compared. In the laser synthesis, as either the laser power or the irradiation time increases, the intensity of the surface plasmon resonance absorption at 400 nm is found to increase linearly first, followed by a reduction of the red edge of the plasmon resonance absorption band. The TEM results showed that in the laser synthesis low powers and short irradiation times produce nanoparticles around 20 nm in diameter. Increasing the power or irradiation time produces a second population of nanoparticles with average size of 5 nm in diameter. These small particles are believed to be formed from the surface ablation of the large particles. The surface plasmon absorption band is found to be narrower when the nanoparticles are produced with laser irradiation. Throughout the exposure time with the CW lamp, the plasmon resonance absorption band of the particles formed first grows in intensity, then blue shifts and narrows, and finally red shifts while decreasing in intensity. The TEM results for lamp samples showed particle formation and growth, followed by small nanoparticle formation. The above results are discussed in terms of a mechanism in which, the excited benzophenone forms the ketal radical, which reduces Ag+ in solution and on the Ag nanoparticle surface. As the time of irradiation or the light energy increases the benzophenone is consumed, which is found to be the limiting reagent. This stops the formation of the normal large nanoparticles while their photo-ablation continues to make the small particles. %B Photochemical & Photobiological Sciences %I Royal Society of Chemistry %V 4 %P 154-159 %G eng %N 1 %R 10.1039/B411488D