Inorganic (silica-titania)-organic (polyethylene oxide) hybrid films with variable refractive index (RI) values were synthesized and Ag nanoparticles were generated in situ inside such hybrid films to develop coloured coatings specially on plastic substrates. The hybrid films and the corresponding Agincorporated films were prepared from sols derived from a mixture of silicon tetraethoxide (STE), 3-(glycidoxypropyl)trimethoxysilane (GPTMS), titanium tetraisopropoxide (TTIP) and silver nitrate following a sol-gel dip-coating method and cured at low temperature (90°C), followed by UV treatment with an energy equivalent to $5.3 \pm 0.1$ J cm-2. The equivalent SiO2: SiO1.5(CH2)3OCH2CH(CH2)O : TiO2: Ag molar ratios (nominal) of the final cured films are varied in the ranges (67.9-0) : 29.1 : (0-67.9) : 3. The refractive index values of the cured hybrid films were found to be increased systematically from 1.475 to 1.710 with increasing Ti-component. The Ag-SPR peak, in case of silica-polyethylene oxide host (RI = 1.475), observed at 419 nm, gradually red-shifted to 497 nm upon increasing the Ticomponent (equivalent TiO2 content 67.9 mol%; RI = 1.710) of the film. As a consequence, a systematic change of Ag-SPR position yielded yellow, yellowish-orange, orange, brownish-orange and orangish-brown coloured coatings.
Volume 135, 2023
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