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Tomar A.K.,Kurukshetra University | Tomar A.K.,Kurukshetra Institute of Technology and Management | Mahendia S.,Kurukshetra University | Chahal R.P.,Kurukshetra University | Kumar S.,Kurukshetra University
Synthetic Metals | Year: 2012

PMMA-PAni composite films have been prepared by mixing different wt.% of chemically synthesized PAni-DBSA in PMMA by sol-gel method. Effect of blending of PAni with PMMA on the structural and dielectric properties of PMMA has been analysed. Raman analysis confirms the formation of chemical network in PMMA and PAni functional groups. An increase in ac conductivity and decrease in dielectric constant were observed with increase in concentration of PAni in PMMA. The dielectric relaxation time reduces from 8.70 μs (in pure PMMA) to 2.30 μs after embedding PAni by 10 wt.% corroborating towards the enhanced conducting nature of blends. © 2012 Elsevier B.V. All rights reserved. Source


Mahendia S.,Kurukshetra University | Tomar A.K.,Kurukshetra University | Tomar A.K.,Kurukshetra Institute of Technology and Management | Chahal R.P.,Kurukshetra University | And 2 more authors.
Journal of Physics D: Applied Physics | Year: 2011

Hydrosol of Au nanoparticles was prepared by citrate reduction of chloroauric acid. The synthesized nanoparticles were characterized through transmission electron microscopy (TEM) and UV-Visible spectroscopy. The prepared nanoparticles were almost spherical in shape with their mean diameter ∼6 nm and possessed face-centred-cubic (fcc) structure. The absorption spectrum of the as-prepared nanoparticles shows the SPR peak at 530 nm in agreement with that predicted from calculations based on Mie theory. These nanoparticles were dispersed in poly(vinyl alcohol) (PVA) using the sol-gel method to prepare PVA-Au nanocomposite films with different concentrations of Au. Optical and structural properties of these nanocomposites were studied using UV-Visible spectroscopy, x-ray diffraction (XRD) and FTIR spectroscopy. The value of optical band gap deduced from the UV-Visible absorption spectroscopy is found to be reduced from 4.98 eV (for pure PVA) to 3.85 eV after embedding 0.074 wt% of Au nanoparticles. Further, the refractive index behaviour for pure PVA and PVA-Au nanocomposite films was studied through transmission and reflection behaviour. The induced structural changes, revealed through XRD and FTIR spectroscopy, are responsible for the observed changes in optical behaviour of PVA after embedding Au nanoparticles in it. © 2011 IOP Publishing Ltd. Source


Mahendia S.,Kurukshetra University | Tomar A.K.,Kurukshetra University | Tomar A.K.,Kurukshetra Institute of Technology and Management | Kumar S.,Kurukshetra University
Materials Science and Engineering B: Solid-State Materials for Advanced Technology | Year: 2011

Hybrids of nano-Ag and PVA films prepared via sol-gel method have been characterized through XRD, TEM, UV-vis spectroscopy and I-V measurements. The change in optical band gap value and room temperature dc conduction behaviour of undoped and nano-Ag doped PVA films have been studied. The value of optical band gap has been found to be reduced from 4.92 eV (for undoped PVA) to 3.93 eV on doping 1.32% (by wt.) nano-Ag in PVA. This decrease in optical band gap and observed increase in conduction can be correlated to the formation of the charge transfer complexes within the polymer network on dispersing nano-Ag in it. Current-voltage behaviour suggests that Poole-Frenkel mechanism is primarily responsible for the observed conduction for both undoped and nano-Ag doped PVA films. © 2011 Elsevier B.V. All rights reserved. Source


Chahal R.P.,Kurukshetra University | Mahendia S.,Kurukshetra University | Tomar A.K.,Kurukshetra University | Tomar A.K.,Kurukshetra Institute of Technology and Management | Kumar S.,Kurukshetra University
Journal of Alloys and Compounds | Year: 2012

Polyvinyl alcohol-silver (PVA/Ag) nanocomposites were prepared through in situ reduction of silver nitrate (AgNO 3) within PVA hydrogel under continuous stirring at 60 °C. The observed characteristic surface plasmon resonance band at around 425 nm in the recorded UV-Visible absorption spectrum confirmed the formation of Ag nanoparticles embedded in a dielectric matrix. It was found that pure PVA exhibited indirect optical energy gap (E g) of 4.92 eV, which reduced to 4.57 eV after embedding Ag nanoparticles, suggesting the formation of charge transport complexes (CTCs) between the localized highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy bands of PVA. On exposure to gamma (γ) radiations at a dose of 50 kGy, the value of E g was reduced further and found to be 3.72 eV. The decrease in optical energy gap and the observed increase in refractive index (n) of PVA/Ag nanocomposites before and after gamma irradiation in comparison with pure PVA suggest the possibility of their use in optical device applications. The induced structural changes in PVA after the formation of embedded Ag nanoparticles and subsequently through gamma irradiation, were revealed through X-ray diffraction (XRD) and Fourier transform infra-red (FTIR) spectroscopy, corroborating the observed changes in their optical behavior. © 2012 Elsevier B.V. All rights reserved. Source


Mahendia S.,Kurukshetra University | Tomar A.K.,Kurukshetra University | Tomar A.K.,Kurukshetra Institute of Technology and Management | Kumar S.,Kurukshetra University
Journal of Alloys and Compounds | Year: 2010

Poly(vinyl alcohol)-silver (PVA-Ag) nanocomposite films were prepared by the soft chemical route. Effect of concentration of embedded Ag nanoparticles on conductivity and dielectric relaxation behaviour of these nanocomposite films has been studied. An increase in dc conductivity from 1.38 × 10 -11 to 9.17 × 10 -11 S/cm and decrease in frequency dependent dielectric constant (from 1.74 to 1.07 at 75 kHz) are observed with the increase in concentration of Ag nanoparticles in PVA from 0 to 1.32 wt%. The values of ac conductivity and polarization relaxation time, deduced from dielectric data, also corroborate towards the enhanced conducting behaviour of PVA matrix with increase in the concentration of embedded Ag nanoparticles. © 2010 Elsevier B.V. All rights reserved. Source

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