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In situ Generation of Au Nanoparticles in UV-curable Refractive Index Controlled SiO2−TiO2−PEO Hybrid Films

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journal contribution
posted on 17.07.2008, 00:00 by Sucheta De, Goutam De
UV-curable inorganic (SiO2−TiO2)−organic (polyetheylene oxide [PEO]) hybrid films with high refractive index (RI) values were synthesized, and Au nanoparticles were generated in situ inside such hybrid films. The hybrid films and the corresponding Au-doped films were prepared from sols derived from a mixture of silicon, titanium, and organically modified silicon alkoxides and gold chloride following a sol−gel dip-coating method. An equivalent SiO2/TiO2/PEO/Au molar ratio (nominal) of 27.7:46.1:23.0:3.2 was maintained in the sol. UV treatments of the dried (90 °C) films with energies from 5.3 ± 0.1 to 53.0 ± 0.5 J cm−2 resulted in densification with a gradual increase of the RI value up to 1.75. Drying and UV treatments of the corresponding HAuCl4-incorporated hybrid films induced generation of Au nanoparticles and showed the characteristic Au−plasmon peak. A gradual red-shifting of the Au−plasmon band from 545 to 571 nm was observed with respect to the UV-treatment energies. This red-shifting is initially due to the increase of RI of the film, and in the later stages it is mainly due to the Au−plasmon coupling concurrently with the slight increase of RI values. Transmision electron microscopy of the UV-treated films showed the presence of densely populated Au nanoparticles of mainly 4−5 nm in size inside the hybrid SiO2−TiO2−PEO film matrix.