Publications (12) View all
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Article: Linear and Nonlinear Optical Properties of Multi Walled Carbon Nanotubes with Attached Gold Nanoparticles
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ABSTRACT: Small, homogenously distributed gold nanoparticles (Au-NPs) in water are synthesised by liquid phase pulsed laser ablation. The UV-visible spectra of Au colloidal solutions shows strong surface plasmon resonance bands indicating the presence of Au-NPs. Homogenous attachment of the Au-NPs to the surface of multi walled carbon nanotubes (MWCNTs) without acid functionalization of the CNTs is achieved by adding a small amount of ethanol. X-ray diffraction shows that the Au-NPs are small face centred cubic Au crystallites. Transmission electron microscopy shows that the Au-NPs have an average diameter of 7 nm. A stable and flexible optical limiting (OL) device is fabricated by dispersing these MWCNTs in a poly vinyl alcohol matrix (PVA). The open aperture Z-scan traces of thin films containing pure MWCNTs, as well as those with attached Au-NPs in a PVA matrix shows that the samples can be used for OL applications. An increase in the OL property has been observed with increasing density of Au-NPs which is attributed to the surface plasmon absorption processes in the Au-NPs at 532 nm causing strong nonlinear scattering effect.Journal of The Electrochemical Society. 09/2011; 158(10):K187-K191. -
Article: Linear and Nonlinear Optical Properties of Gold Nanoparticle Attached MWCNTs
Journal of Electrochemical Society. 01/2011; 158:K187. -
Article: Violet luminescence from ZnO nanorods grown by room temperature Pulsed Laser Deposition
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ABSTRACT: ZnO thin films were deposited at room temperature by pulsed laser deposition (PLD) varying the oxygen pressure. Morphological analysis using scanning electron microscope (SEM) and atomic force microscopy (AFM) demonstrated the formation of ZnO nanorods at a particular oxygen pressure. Room temperature violet luminescence was observed from these ZnO nanorods and temperature dependence of luminescence was studied. Influence of oxygen pressure on the growth of ZnO thin films by PLD was studied using the X-ray photoelectron spectroscopy of both post ablated targets and deposited films. The ZnO films were crystalline and the formation of crystalline phase is found to follow a pressure–temperature (P–T) scaling with increase of temperature.Current Applied Physics. 01/2010; 10:693. -
Article: Co2+ Doped ZnO Nanoflowers Grown by Hydrothermal Method
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ABSTRACT: Undoped zinc oxide (ZnO) and cobalt doped ZnO nanostructures without any surfactant were grown by hydrothermal method by varying the process parameters such as molarity of precursors and time of growth. X-ray diffraction spectra of the sample show wurtzite ZnO without any secondary Co phases. SEM image confirms the formation of hexagonal shaped rods and these rods assembled like a flower. Inductively coupled plasma atomic emission spectroscopic (ICP AES) studies confirm the incorporation of cobalt in the ZnO nanostructures. The electronic structure as well as the optical properties of ZnO:Co2+ have been characterized. In the energy range below the band gap, the optical absorption spectra show the internal dd transitions related to Co2+ incorporated on the Zn site in ZnO lattice. The g-values of ZnO:Co samples obtained from electron paramagnetic resonance confirms the incorporation of Co2+ in ZnO. Photoluminescence (PL) studies shows that these nanostructures exhibit a blue luminescence on excitation with wavelength 350nm due to the Zn interstitial related defects.Journal of the Ceramic Society of Japan. 01/2010; 118:333. -
Article: Linear and nonlinear optical properties of luminescent ZnO nanoparticles embedded in PMMA matrix
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ABSTRACT: ZnO nanoparticles embedded in the PMMA matrix were prepared by wet chemical synthesis. The optical band gap of the ZnO nanoparticles decreases with increase in NaOH concentration. The photoluminescence spectra of the ZnO colloids show strong UV, green and blue emissions. The optical absorptive nonlinearity of the ZnO:PMMA composites was analyzed using an open aperture Z-scan technique which shows optical limiting type nonlinearity due to the two photon absorption in ZnO. The efficiency of limiting is found to increase with decrease in the band gap. ZnO:PMMA shows a negative value for nonlinear refractive index n2 and the magnitude of n2 increases with decrease of band gap. Stability as well as the mechanical properties of the nanoparticles embedded in the PMMA matrix makes it more suitable for device fabrication as compared to the ZnO nanoparticles dispersed in solution.Optics Communications. 01/2010; 283:2908.
