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Sharma S.,Institute of Advanced Study in Science and Technology Paschim Boragaon | Pal A.R.,Institute of Advanced Study in Science and Technology Paschim Boragaon | Chutia J.,Institute of Advanced Study in Science and Technology Paschim Boragaon | Bailung H.,Institute of Advanced Study in Science and Technology Paschim Boragaon | And 3 more authors.
Applied Surface Science | Year: 2012

Deposition of composite thin film of polyaniline/TiO 2 (PAni/TiO 2) has been carried out by a combined process of magnetron sputtering and plasma polymerization at a pressure of 5 × 10 -2 Torr using titanium as a target material for sputtering, aniline as monomer, oxygen as reactive gas and argon as carrier gas/ion source for sputtering. The deposition has been achieved using direct current (dc) discharge power of 35 W for sputtering and radio frequency (rf) power of 8-12 W at substrate bias values in the ranges of -80 to -100 V for polymerization. The composition of the film has been studied using infrared spectroscopy, Raman spectroscopy as well as X-ray photoelectron spectroscopy. The morphology of the film has been characterized with the help of a transmission electron microscopy and atomic force microscopy. The ultraviolet (UV) photo-stability of the composite film has been studied by exposing the film deposited on silicon substrate for different reaction times up to 1 h under UV radiation at wave length range of 280-400 nm with an intensity of 0.4 mW/cm 2. An organic/inorganic nanocomposite film based photovoltaic device has been developed. The device has an aluminum/composite/indium tin oxide sandwiched structure that shows strong photoresponse in ultraviolet region and hence the device has potential for application as an UV detector. © 2012 Elsevier B.V. All rights reserved.


Choudhury A.J.,Institute of Advanced Study in Science and Technology Paschim Boragaon | Kakati H.,Institute of Advanced Study in Science and Technology Paschim Boragaon | Pal A.R.,Institute of Advanced Study in Science and Technology Paschim Boragaon | Patil D.S.,Bhabha Atomic Research Center | Chutia J.,Institute of Advanced Study in Science and Technology Paschim Boragaon
Journal of Physics: Conference Series | Year: 2010

The deposition of polystyrene films by capacitively coupled rf plasma on bell metal was investigated. Argon/styrene gas mixture was used for coating in the pressure range (7-16) × 10 -2 mbar at different rf powers (40-150 Watt). The structure and composition of these polystyrene films were characterized by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis. The deposition condition of these films was optimized for good adhesive and corrosion resistance behaviours. The results showed the possible application of polystyrene films as corrosion resistance coating on bell metal. © 2010 IOP Publishing Ltd.


Baruah U.,Institute of Advanced Study in Science and Technology Paschim Boragaon | Chowdhury D.,Institute of Advanced Study in Science and Technology Paschim Boragaon
RSC Advances | Year: 2016

Preparation of graphene oxide quantum dot-inorganic nanoparticle hybrids is still an unexplored area of graphene-centred research. The present study demonstrates the ethylene diamine mediated in situ synthesis of cobalt oxide nanoparticles (Co3O4 NPs) studded on graphene oxide quantum dots (GOQDs). Ethylene diamine(en) is known to form a stable coordination complex with Co2+. CoCl2 was used as a precursor material for Co-nanoparticle formation as small sized Co2+ ions can enter the interlayer spacing between the graphene sheets. Ethylene diamine gets attached to the GOQDs via ring opening of epoxy groups on the GOQDs and pulls the Co2+ ions from the medium onto the GOQDs. On treating this system with hydrogen peroxide, GOQDs-en-Co3O4 nanoparticle composites with enhanced optical properties could be successfully prepared. We also tried to explore the potential of our system as a reversible on/off fluorescence switching material based on oxidation-reduction chemistry and could find satisfactory results. Such systems we believe can prove to be model systems for quantum level graphene-inorganic nanoparticle hybrid nanocomposites with potential for application in optoelectronic devices. © The Royal Society of Chemistry 2016.


Baruah U.,Institute of Advanced Study in Science and Technology Paschim Boragaon | Deka M.J.,Institute of Advanced Study in Science and Technology Paschim Boragaon | Chowdhury D.,Institute of Advanced Study in Science and Technology Paschim Boragaon
RSC Advances | Year: 2014

We demonstrate a simple, facile, and reversible on/off fluorescence switching by functionalization of carbon dots (CDs) via esterification. The CDs synthesized from citric acid show pH-dependent photoluminescence (PL), with higher PL intensity observed at pH 7 than at pH 1. The hydroxyl and carboxyl group-bearing CDs were also esterified with different alcohols, and their PL properties were studied. It is interesting to note that in all the cases, low PL intensity of CDs at pH 1 can be transformed into a high PL system by esterification of CDs. However, at neutral pH 7, the PL intensity was found to be lower after esterification of CDs. Moreover, at pH 1, the subsequent hydrolysis of esterified CDs again results in low PL intensity, thereby demonstrating the reversibility of the process. © the Partner Organisations 2014.


Sharma S.K.,Institute of Advanced Study in Science and Technology Paschim Boragaon | Boruah A.,Institute of Advanced Study in Science and Technology Paschim Boragaon | Bailung H.,Institute of Advanced Study in Science and Technology Paschim Boragaon
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2014

The collision between two counterpropagating dust acoustic solitary waves in a strongly coupled dusty plasma has been observed. The measured velocity and width of the solitary wave agree with the solution of the Korteweg-de Vries equation derived by using the generalized hydrodynamic model. The two counterpropagating solitary waves of equal amplitude merge into a single pulse with twice the individual soliton amplitude and then pass through each other. The solitons suffer a small time delay in propagation after collision. The measured delay time obtained from their trajectories is also presented. © 2014 American Physical Society.


Konwar A.,Institute of Advanced Study in Science and Technology Paschim Boragaon | Chowdhury D.,Institute of Advanced Study in Science and Technology Paschim Boragaon
RSC Advances | Year: 2015

Synthesis of nanocomposites of biopolymers is the answer to obtaining superior properties which are biocompatible but also possess good mechanical properties. In this work we made an attempt to study the property relationship of alginate and alginate-carbon dot nanocomposites with different bivalent and trivalent cross-linker ions. Biopolymer alginates were crosslinked with five different bivalent and trivalent metal ions and their corresponding carbon-dot (CD) nanocomposites have been prepared successfully. The carbon dots were prepared from commercially available 'Assam Tea'. The alginate and alginate-carbon dot nanocomposite films were characterized with UV-visible spectroscopy, FTIR, SEM, and fluorescent microscopy. The tensile strength measurements of all the film samples have been carried out. It was observed that alginate films crosslinked by metal ions with larger sizes (Ba2+) show higher tensile strength and higher thermostability. Tensile strength values for Ba2+ crosslinked alginate films increased from 24.5 MPa to 43.5 MPa and weight loss at 200 °C decreased to 9% on incorporation of 2% CDs. Moreover loading of carbon-dots in the crosslinked alginate system led to higher absorption in the UV region showing the potential use of alginate-carbon dot films as UV blockers. For Ca2+ and Ba2+ crosslinked films minimum transmittance values significantly reduced to 4 and 5% respectively in the region from 200 to 400 nm for nanocomposite films with maximums of 2% CDs. Some mechanistic aspect of the superior property shown by Ba2+ crosslinked alginate and alginate-carbon dot nanocomposites is also discussed. © 2015 The Royal Society of Chemistry.

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