Anti-counterfeiting Behaviour of Organic-Inorganic Hybrid Silica Film with a Chiral Smectic C Structure

Graphical Structurally coloured organic-inorganic hybrid silica films with a SmC* structure were prepared. Due to the light scattering of the nanoparticles on film surface and the selective Bragg reflection of film inside, the colourful patterns can be observed in the oblique view and not be observed in the vertical view. Therefore, the OIHS films can be used for anti-counterfeiting. Artificial photonic materials based on chiral liquid-crystalline nanostructures have attracted increasing interests for their wide applications as sensors, anti-counterfeit measures, displays and colour filters. Although the structurally coloured films with chiral nematic structures or blue phases have been prepared, the ones fabricated by fixing chiral smectic C (SmC*) phases have been rarely reported. In this work, organic-inorganic hybrid silica (OIHS) films with a SmC* structure were reported for the first time. An organosilane (CSC) with an enantiotropic SmC* phase was synthesized. The OIHS films with a SmC* structure were fabricated by the polycondensation of CSC under an acidic condition. The colour patterns can be observed in the oblique view, but not be observed in the vertical view, which is mainly due to the light scattering of the nanoparticles on film surface and the selective Bragg reflection of film inside. Therefore, such properties make the OIHS films promising candidates for anti-counterfeiting applications.