Spectroscopic studies on liquid crystalline p-n-nonyloxy benzoic acid (9oba) dispersed citrate capped gold nanoparticles

Systematic studies are carried out on liquid crystalline (LC) p-n-nonyloxy benzoic acid (9oba) with homogeneous dispersion of citrate capped gold nanoparticles (gnps) in various concentrations at four wavelengths 635, 589.3, 500 and 460 nm respectively. XRD pattern have shown face centered cubic lattice (fcc). SEM has evidenced the homogeneous dispersion of citrate capped gold nanoparticles in LC compounds. Co-occurrence matrix method is used to identify the phase transition. UV–vis spectroscopy is performed to confirm the presence of citrate capped gnps in 9oba. The LC nanocomposite is used to observe the changes occurred in optical parameters like birefringence and order parameter with different concentrations at various wavelengths. With the help of indigenously designed and fabricated modified spectrometer, the birefringence (δn) is calculated from refractive indices data (ne and no). The birefringence values of 9oba increase with gradual enhancement of the concentrations of citrate capped gnps due to sturdy van der waal’s interaction which occurs between the citrate capped gnps and LC molecules. From the birefringence data, the order parameter S is evaluated with internal field models, Kuczynski method, Effective geometry method and Vuks method respectively. The order parameter of the molecules of 9oba increases from 1.47 to 25.32 % with the increasing concentrations of nanoparticle dispersion in all the above models, which find potential applications in LC display devices.