Liquid Crystals Decorated Gold Nanoparticles for Photoswitching Properties

Abstract

Liquid crystals decorated gold nanoparticles are synthesized as the molecular architecture consists of the azobenzenes moieties with alkene as the peripheral units, which are connected to gold nanoparticles (Au-NPs) via thiolated phenolic units are in the middle. The morphology and mesomorphic properties were investigated by the field emission scanning electron microscope, high-resolution transmission electron microscopy, differential scanning calorimetry, and polarizing optical microscopy. The aromatic thiolated azobenzene moieties with gold nanoparticles showed smectic A phase with monotropic nature only appeared in the cooling cycle. HR-TEM measurement showed that the functionalized Au-NPs are well dispersed without any aggregation. However, the absorption spectrum of peripheral azobenzene units shows strong absorption maxima in the ultraviolet region at 378 nm due to π-π* transition. For n-π* transition, a weak absorption band is observed in the visible region at 472 nm. The photo-isomerization characteristic is measured using absorption spectroscopy. The photosatur- ation of Au-NPs is found at the time duration of 16 s. The thermal back relaxation is completed after the time interval of 70 min. Moreover, Au-NPs showed excellent stability towards photo-decay. Therefore, Au-NPs compound is suitable in the field of optical storage and molecular switching.