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Ratnadurai R.,University of South Florida | Niemann M.U.,University of South Florida | Phani A.R.,Nano Research for Advanced Materials and Technologies | Goswami D.Y.,University of South Florida | Stefanakos E.K.,University of South Florida
International Journal of Hydrogen Energy | Year: 2010

Due to its many physisorption sites as well as chemisorption sites, polyaniline (PANI) has been investigated for hydrogen storage purposes. The PANI was produced in house via traditional chemical synthesis methods and then electrospun to produce fibers. These PANI fibers were investigated and compared with standard bulk PANI and found to be stable up to 150 °C. When investigating PANI fibers, using PCT measurements, it was found that a reversible hydrogen storage capacity of ∼3-10 wt.% could be obtained at different temperatures. Hydrogen kinetic sorption measurements in prolonged cycles (up to 66 cycles) reveal an uptake and release of >6-10 wt.% on these PANI materials. The importance of the type of measurement is discussed as to its effect on the morphology and structure of the PANI nanofibers. The surface morphologies before and after hydrogen sorption on these PANI fibers encompass significant changes in the microstructure (nanofibrallar swelling effect). Detailed chemical and physical characterization of the PANI fibers is reported as part of this work. © 2009 Professor T. Nejat Veziroglu.


Kumar R.R.,Indian Institute of Science | Parmar M.,Indian Institute of Science | Parmar M.,Chonnam National University | Narasimha Rao K.,Indian Institute of Science | And 2 more authors.
Scripta Materialia | Year: 2013

A simple thermal evaporation method is presented for the growth of crystalline SnO2 nanowires at a low substrate temperature of 450 °C via an gold-assisted vapor-liquid-solid mechanism. The as-grown nanowires were characterized by scanning electron microscopy, transmission electron microscopy and X-ray diffraction, and were also tested for methanol vapor sensing. Transmission electron microscopy studies revealed the single-crystalline nature of the each nanowire. The fabricated sensor shows good response to methanol vapor at an operating temperature of 450 °C.© 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.


Rakesh Kumar R.,Indian Institute of Science | Narasimha Rao K.,Indian Institute of Science | Rajanna K.,Indian Institute of Science | Phani A.R.,Nano Research for Advanced Materials and Technologies
Advanced Materials Letters | Year: 2013

Silicon nanowires were grown on tin (Sn) coated Si substrates using electron beam evaporation technique at a growth temperature of 350°C. The as grown Si nanowires were characterized by Field Emission Scanning Electron Microscope (FESEM), Transmission Electron Microscopy attached with Energy Dispersive X-Ray Analyser (TEM-EDX) for their morphological, structural, and compositional properties, respectively. The grown Si nanowires were randomly oriented on the substrate with a length of ~ 500 nm for a deposition time of 15 min. Silicon nanowires have shown tin nanoparticle (capped) on top of it confirming the Vapor-Liquid-Solid (VLS) growth mechanism responsible for Si nanowires growth. The nanowire growth rate was measured to be ~30 nm/min. Transmission Electron Microscope (TEM) measurements have revealed single crystalline nature of Si nanowires. The obtained results have indicated good progress towards finding alternative catalyst to gold for the synthesis of Si nanowires. © 2013 VBRI press.


Kumar R.R.,Indian Institute of Science | Rao K.N.,Indian Institute of Science | Phani A.R.,Nano Research for Advanced Materials and Technologies
Materials Letters | Year: 2012

For the first time silicon nanowires have been grown on indium (In) coated Si (100) substrates using e-beam evaporation at a low substrate temperature of 300 °C. Standard spectroscopic and microscopic techniques have been employed for the structural, morphological and compositional properties of as grown Si nanowires. The as grown Si nanowires have randomly oriented with an average length of 600 nm for a deposition time of 15 min. As grown Si nanowires have shown indium nanoparticle (capped) on top of it confirming the Vapor Liquid Solid (VLS) growth mechanism. Transmission Electron Microscope (TEM) measurements have revealed pure and single crystalline nature of Si nanowires. The obtained results have indicated good progress towards finding alternative catalyst to gold for the synthesis of Si nanowires. © 2011 Elsevier B.V.


Kumar R.R.,Indian Institute of Science | Rao K.N.,Indian Institute of Science | Phani A.R.,Nano Research for Advanced Materials and Technologies
Materials Letters | Year: 2012

Silicon nanowires (NWs) have been grown in the vapor phase for the first time with bismuth (Bi) as a catalyst using the electron beam evaporation method at a low substrate temperature of 280 °C. The grown Si nanowires were randomly oriented on the substrate with an average length of 900 nm for a deposition time of 15 min. Bi faceted nanoparticles (crowned) at the end of the grown Si nanowires have been observed and attributed to the Vapor-Liquid-Solid (VLS) growth mechanism. Transmission Electron Microscopy analysis on the nanowires revealed their single crystalline nature and interestingly bismuth particles were observed in Si nanowires. The obtained results have shown a new window for Si nanowires growth with bismuth as a catalyst. © 2012 Elsevier B.V. All rights reserved.


Sahoo S.,Plnayak Research Foundation | Sasmal A.,Plnayak Research Foundation | Nanda R.,Plnayak Research Foundation | Phani A.R.,Nano Research for Advanced Materials and Technologies | Nayak P.L.,Plnayak Research Foundation
Carbohydrate Polymers | Year: 2010

In the present research work chitosan has been blended with different amounts of polycaprolactone (PCL) (80:20, 75:25, 60:40 and 50:50) for using them for control delivery of ofloxacin. The blends were characterized by Fourier transmission infra red spectroscopy (FTIR), UV-visible spectroscopy (UV), scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis. From the FTIR spectra the various groups present in chitosan and PCL blend were monitored. The homogeneity, morphology and crystallinity of the blends were ascertained from SEM and XRD data, respectively. The swelling studies have been measured at different drug loading. The kinetics of the drug delivery system has been systematically studied. Drug release kinetics was analyzed by plotting the cumulative release data vs. time by fitting to an exponential equation which indicated the non-Fickian type of kinetics. The drug release was investigated at different pH medium and it was found that the drug release depends upon the pH medium as well as the nature of matrix. © 2009 Elsevier Ltd.


Kumar R.R.,Indian Institute of Science | Rao K.N.,Indian Institute of Science | Rajanna K.,Indian Institute of Science | Phani A.R.,Nano Research for Advanced Materials and Technologies
Materials Letters | Year: 2013

Antimony doped tin oxide (Sb:SnO2) nanowires were grown by thermal and e-beam assisted co-evaporation of Sb and Sn in the presence of oxygen at a low substrate temperature of 450 C. The field emission scanning electron microscopy study revealed that the nanowires had a length and diameter of 2-4 μm and 20-60 nm respectively. Transmission electron microscopy study revealed the single crystalline nature of the nanowires; energy dispersive X-ray spectroscopy (EDS) and EDS mapping on the nanowires confirmed the presence of Sb doping in the nanowires. UV light detection study on the doped SnO 2 nanowire films exhibited fast response and recovery time compared to undoped SnO2 nanowire films. This is an innovative and simple method to grow doped SnO2 nanowires. © 2013 Elsevier B.V.


Kumar R.R.,Indian Institute of Science | Rao K.N.,Indian Institute of Science | Rajanna K.,Indian Institute of Science | Phani A.R.,Nano Research for Advanced Materials and Technologies
Materials Research Bulletin | Year: 2013

For the first time, high quality tin oxide (SnO2) nanowires have been synthesized at a low substrate temperature of 450 °C via vapor-liquid-solid mechanism using an electron beam evaporation technique. The grown nanowires have shown length of 2-4 μm and diameter of 20-60 nm. High resolution transmission electron microscope studies on the grown nanowires have shown the single crystalline nature of the SnO2 nanowires. We investigated the effect of growth temperature and oxygen partial pressure on SnO2 nanowires growth. Variation of substrate temperature at a constant oxygen partial pressure of 4 × 10-4 mbar suggested that a temperature equal to or greater than 450 °C was the best condition for phase pure SnO2 nanowires growth. The SnO2 nanowires grown on a SiO2 substrate were subjected to UV photo detection. The responsivity and quantum efficiency of SnO2 NWs photo detector (at 10V applied bias) was 12 A/W and 45, respectively, for 12 μW/cm2 UV lamp (330 nm) intensity on the photo detector. © 2012 Elsevier Ltd.


Rakesh Kumar R.,Indian Institute of Science | Narasimha Rao K.,Indian Institute of Science | Phani A.R.,Nano Research for Advanced Materials and Technologies
Materials Letters | Year: 2013

For the first time, Tin oxide (SnO2) multiple branched nanowires (NWs) have been synthesized by thermal evaporation of tin (Sn) in presence of oxygen without use of metal catalysts at low substrate temperature of 500 °C. Synthesized product consists of multiple branched nanowires and were single crystalline in nature. Each of the nanowire capped with catalyst particle at their ends. Energy dispersive X-ray analysis on the nanowires and capped nanoparticle confirms that Sn act as catalyst for SnO2 nanowires growth. A self catalytic vapor-liquid-solid (VLS) growth mechanism was proposed to describe the SnO2 nanowires growth. © 2012 Elsevier B.V.


Jotiram K.P.,Health Science University | Jotiram K.P.,La Trobe University | Prasad R.G.S.V.,Health Science University | Jakka V.S.,Health Science University | And 2 more authors.
Nano Biomedicine and Engineering | Year: 2012

Nanostructured and conducting polymer polyaniline (PANI) is used in numerous applications in electrotherapy, electro-magnetic materials for monitoring health, antimicrobial clothing, data transfer in smart textiles, biosensors and for defense technology. An important criterion for all the above mentioned utilities is, producing polymeric conductive fibers. In the present study we prepared conducting PANI nanofibres combined with mupirocin, a topical antimicrobial agent, through a self-assembly process. The prepared polymer was then tested for the antibacterial properties against various Gram positive and Gram negative bacteria such as Streptococcus pyogenes, Staphylococcus epidermidis, Staphylococcus aureus and Escherichia coli. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were used to identify the chemical structure of the PANI nanofibres. The antibacterial properties were assessed by measuring the zones of inhibition. It was evident from these results that antimicrobial activity increased with increasing PANI and PANI combined with mupirocin (PANI-mupirocin) concentrations. It was also found that PANI-mupirocin has enhanced antimicrobial activity compared to PANI alone. This information might be useful to evaluate the potential use of nanostructured polyaniline in fabrics incorporated with antibacterial agents as a prophylactic use against bacterial skin infections in the near future. © 2012 K.P. Jotiram, et al.

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