Department of Physics
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Item Alignment Of Liquid Crystalson Lb Films Of Stearic Acid(CIB Tech, 2012) Gupta, Raj Kumar; Manjuladevi, V.We formed the Langmuir monolayer of stearic acid at the air-water (A-W) interface. The Langmuir-Blodgett (LB) films were deposited on solid substrates at different surface pressures. The liquid crystal cells were prepared over such LB films. We found that these cells exhibit a tendency to align in planar orientation for the liquid crystal. We found that the liquid crystal alignment improves in cells prepared with substrates deposited at higher surface pressure like 25mN/m. We present the results on the liquid crystal alignment as a function of number of layers of LB films deposited on the substrates at various surface pressures. We propose that LB films of stearic acid can be used as an aligning agent for liquid crystals.Item Surface Plasmon Resonance Study Of Langmuir-blodgett Films Of Stearic Acid(CIB Tech, 2012) Manjuladevi, V.; Gupta, Raj KumarStearic acid is one of the commonly studied fatty acid. It exhibits interesting behavior on surfaces. The Langmuir Blodgett films of stearic acid were fabricated on solid substrates. We have developed a surface plasmon resonance (SPR) instrument in the Kretschmann configuration. The change in SPR angle due to molecular specific interaction is potentially employed for sensing application. In this paper we report our studies on SPR of stearic acid deposited on solid substrates. We find a significant change in the resonance angle.Item Periodic array of nanoparticles on gold substrate(AIP, 2013-06) Gupta, Raj Kumar; Manjuladevi, V.The thin films of nanoparticles of titanium dioxide were deposited on gold deposited substrates by drop cast method. The films were characterized employing the atomic force microscope in contact mode. We obtained a high degree of orderness among the nanoparticles. The orderness are different in different direction.Item Scanning tunneling spectroscopy of thin films of carbon nanotubes(AIP, 2013) Gupta, Raj Kumar; Manjuladevi, V.The thin films of single walled carbon nanotubes (CNT) were deposited on indium tin oxide (ITO) glass substrates. The films were characterized using scanning tunneling microscopy and spectroscopy. The topographic images reveal a high degree of orientational order in the arrangement of bundles of CNT onto the ITO substrates. We found a significant narrowing of the band gap of the CNT films on ITO as compared to that of ITO film on glass substrate.Item Studies on Adsorption of DNA on Functional Ultrathin Films of Cationic Surfactant(Hindawi Publishing Corporation, 2014-01) Manjuladevi, V.; Gupta, Raj KumarWe have investigated the interaction of DNA with a highly ordered functional ultrathin layer of cationic surfactant, dioctadecyl ammonium bromide (DOAB). The ultrathin film of DOAB is fabricated by Langmuir-Blodgett technique onto the pretreated quartz crystal wafers. The solution of DNA in phosphate buffer saline (PBS) is injected through a flow cell in a quartz crystal microbalance (QCM) loaded with the functional ultrathin film. The QCM data indicate a slower kinetics (time constant = 162.2 seconds) for the adsorption of DNA on DOAB layer as compared to PBS on DOAB. The surface morphology of the aggregation of DNA over the DOAB layer is investigated using atomic force microscope (AFM). The AFM image indicates the trapping of DNA over the DOAB layer. Such trapping of DNA can be potentially employed in the field of genomics.Item Formation of H-type liquid crystal dimer at air-water interface(AIP, 2014) Manjuladevi, V.; Gupta, Raj KumarWe have formed the Langmuir monolayer of H-shaped Azo linked liquid crystal dimer molecule at the air-water interface. Isocycles of the molecule showed hysteresis suggesting the ir-reversible nature of the monolayer formed. The thin film deposited on the silicon wafer was characterized using Atomic Force Microscopy (AFM) and Field Emission Scanning Electron Microscopy (FESEM). The images showed uniform domains of the dimer molecule. We propose that these molecules tend to take book shelf configuration in the liquid phase.Item Effect of Functionalized CNT on Nematic anchoring(ARXIV, 2015-07) Manjuladevi, V.; Gupta, Raj KumarNematic phase is the most fundamental mesophase exhibited by most of the rod shaped anisotropic liquid crystalline molecules. Nematics are orientationally ordered fluids whose average orientation direction can be manipulated on application of electric and magnetic fields. Carbon nanotube (CNT), a highly shape anisotropic object can find numerous industrial application because of its interesting electronic and mechanical properties. The self-organizing properties of nematics can be used to align CNTs dispersed in them. We have dispersed functionalized CNTs in nematic liquid crystal and carried out many experimental studies. We will present results of electro-optic switching and dielectric measurements on some CNT-LC dispersion. We have observed that addition of functionalized CNTs in a liquid crystal (LC) has led to improvement in the nematic ordering which is evidential from enhancement in dielectric anisotropy (De) measurement. These results indicate that the anchoring energy at alignment layers has been influenced by presence of FCNT in the LC host. The anchoring enhancement can be attributed to p-p electron stacking between the FCNT, LC and the alignment layer.Item Sensing of contaminants in potable water using TiO{sub 2} functional film(AIP, 2016) Manjuladevi, V.The piezoelectric based quartz crystal microbalance is employed for sensing contaminants in potable water. A spin coated thin layer of TiO{sub 2} nanoparticles was formed at the sensing area of a 5 MHz AT-cut quartz wafer. The thin film of TiO{sub 2} nanoparticles forms a mesoporous functional layer for the trapping of water borne contaminants. The morphology of the thin film of TiO{sub 2} nanoparticles was studied using field emission scanning electron microscope (FESEM). The surface morphology of the TiO{sub 2} nanoparticles reveals the mesoporous structures indicating large number of defects and porous sites. Such film was employed for the detection of water borne contaminants by detecting the piezoelectric response from a quartz crystal microbalance. We found the film to be very sensitive to the contaminants. The minimum detection limit was found to be 330 ppb. The effect of surface recharging was also studied by altering the physical conditions so that the film can be used for repetitive usage.Item Sensing of contaminants in potable water using TiO2 functional film(AIP, 2016-04) Manjuladevi, V.; Gupta, Rajiv; Gupta, Raj KumarThe piezoelectric based quartz crystal microbalance is employed for sensing contaminants in potable water. A spin coated thin layer of TiO2 nanoparticles was formed at the sensing area of a 5 MHz AT-cut quartz wafer. The thin film of TiO2 nanoparticles forms a mesoporous functional layer for the trapping of water borne contaminants. The morphology of the thin film of TiO2 nanoparticles was studied using field emission scanning electron microscope (FESEM). The surface morphology of the TiO2 nanoparticles reveals the mesoporous structures indicating large number of defects and porous sites. Such film was employed for the detection of water borne contaminants by detecting the piezoelectric response from a quartz crystal microbalance. We found the film to be very sensitive to the contaminants. The minimum detection limit was found to be 330 ppb. The effect of surface recharging was also studied by altering the physical conditions so that the film can be used for repetitive usage.Item Studies on morphology of Langmuir-Blodgett films of stearic acid deposited with different orientation of substrates with respect to compression(AIP, 2016-05) Gupta, Raj Kumar; Manjuladevi, V.The Langmuir monolayer at an air-water interface shows remarkably different surface pressure – area isotherm, when measured with the surface normal of a Wilhemly plate parallel or perpendicular to the direction of compression of the monolayer. Such difference arises due to difference in stress exerted by the monolayer on the plate in different direction. In this article, we report the effect of changing the direction of substrate normal with respect to the compression of the monolayer during Langmuir-Blodgett (LB) film deposition on the morphology of the films. The morphology of the LB film of stearic acid was studied using an atomic force microscope (AFM). The morphology of the LB films was found to be different due to difference in the stress in different directions