title: Synthesis of new liquid crystals embedded gold nanoparticles for photoswitching properties.
abstract: A new series of liquid crystals decorated gold nanoparticles is synthesized whose molecular architecture has azobenzenes moieties as the peripheral units connected to gold nanoparticles (Au NPs) via alkyl groups. The morphology and mesomorphic properties were investigated by field emission scanning electron microscope, high-resolution transmission electron microscopy, differential scanning calorimetry and polarizing optical microscopy. The thiolated ligand molecules (3a-c) showed enantiotropic smectic A phase, whereas gold nanoparticles (5a-c) exhibit nematic and smectic A phase with monotropic nature. HR-TEM measurement showed that the functionalized Au NPs are of the average size of 2nm and they are well dispersed without any aggregation. The trans-form of azo compounds showed a strong band in the UV region at ∼378nm for the π-π(∗) transition, and a weak band in the visible region at ∼472nm due to the n-π(∗) transition. These molecules exhibit attractive photoisomerization behaviour in which trans-cis transition takes about 15s whereas the cis-trans transition requires about 45min for compound 5c. The extent of reversible isomerization did not decay after 10 cycles, which proved that the photo-responsive properties of 5c were stable and repeatable. Therefore, these materials may be suitably exploited in the field of molecular switches and the optical storage devices.
authors.affiliation: Faculty for Science and Natural Resources, Universiti Malaysia Sabah, 88400 Kota Kinabalu, Sabah, Malaysia. Electronic address: lutfor73@gmail.com.
authors.forename: Md Lutfor
authors.initials: ML
authors.lastname: Rahman
authors.affiliation: Faculty of Industrial Sciences & Technology, Universiti Malaysia Pahang, 26300 Gambang, Kuantan, Pahang, Malaysia.
authors.forename: Tapan Kumar
authors.initials: TK
authors.lastname: Biswas
authors.affiliation: Faculty of Industrial Sciences & Technology, Universiti Malaysia Pahang, 26300 Gambang, Kuantan, Pahang, Malaysia.
authors.forename: Shaheen M
authors.initials: SM
authors.lastname: Sarkar
authors.affiliation: Faculty of Industrial Sciences & Technology, Universiti Malaysia Pahang, 26300 Gambang, Kuantan, Pahang, Malaysia.
authors.forename: Mashitah Mohd
authors.initials: MM
authors.lastname: Yusoff
authors.affiliation: Raman Research Institute, C.V. Raman Avenue, Sadashivnagar, Bangalore 560080, India.
authors.forename: A R
authors.initials: AR
authors.lastname: Yuvaraj
authors.affiliation: Raman Research Institute, C.V. Raman Avenue, Sadashivnagar, Bangalore 560080, India.
authors.forename: Sandeep
authors.initials: S
authors.lastname: Kumar
keywords: Gold nanoparticles; Liquid crystals; Molecular switches; Optical storage; Photoswitching