Browsing by Subject "Polymethyl methacrylate"

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    Preparation of Au and Au-Pt nanoparticles within PMMA matrix using UV and X-ray irradiation
    (2009) Ozkaraoglu, E.; Tunc, I.; Süzer, Şefik
    Au and Au-Pt alloy nanoparticles are prepared and patterned at room temperature within the PMMA polymer matrix by the action of 254 nm UV light or X-rays. The polymer matrix enables us to entangle the kinetics of the photochemical reduction from the nucleation and growth processes, when monitored by UV-vis spectroscopy. Accordingly, increase of the temperature to 50 °C of the reaction medium increases the nucleation and growth rates of the nanoparticle formation by more than one order of magnitude, due to enhanced diffusion and nucleation at the higher temperature, but has no effect on the photochemical reduction process. Presence of Pt ions also increases the same rate, but by a factor two only. Similar photochemical reduction and particle growth take also place within the PMMA matrix, when these metal ions are subjected to prolonged exposure to X-rays, as evidenced by XPS analysis. Both angle-resolved and charge-contrast measurements using XPS reveal that the resultant Au and Pt species are in close proximity to each other, indicating the Au-Pt alloy formation to be the most likely case.
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    Reaction-based sensing of fluoride ions using built-in triggers for intramolecular charge transfer and photoinduced electron transfer
    (American Chemical Society, 2010) Bozdemir, O. A.; Sozmen, F.; Buyukcakir, O.; Guliyev, R.; Cakmak, Y.; Akkaya, E. U.
    Two Bodipy derivatives with silyl-protected phenolic functionalities signal fluoride concentrations both In solution and in a poly(methyl methacrylate) matrix. The exact location of the "nascent" phenolate group is Important. If it Is at the meso position, photoinduced electron transfer is triggered; however, if It is In full conjugation via a styryl moiety to the Bodipy core, strong intramolecular charge transfer Is triggered, resulting In a large red shift in the absorbance peak. In either case, a selective methodology for fluoride sensing is the Invariable result.