Now showing 1 - 10 of 18
  • Placeholder Image
    Publication
    Green approach for the large-scale synthesis of metal/metal oxide nanoparticle decorated multiwalled carbon nanotubes
    (21-01-2013)
    Baro, Mridula
    ;
    Nayak, Pranati
    ;
    Baby, Tessy Theres
    ;
    Herein we report a green approach for the synthesis of metal/metal oxide nanoparticle decorated multiwalled carbon nanotubes using focused solar radiation. The synthesis method demonstrates a large scale, cost effective and spontaneous production of carbon nanotube supported metal/metal oxide nanoparticles for energy and biological applications. © 2013 The Royal Society of Chemistry.
  • Placeholder Image
    Publication
    Enhanced convective heat transfer using graphene dispersed nanofluids
    (01-01-2011)
    Baby, Tessy Theres
    ;
    Nanofluids are having wide area of application in electronic and cooling industry. In the present work, hydrogen exfoliated graphene (HEG) dispersed deionized (DI) water, and ethylene glycol (EG) based nanofluids were developed. Further, thermal conductivity and heat transfer properties of these nanofluids were systematically investigated. HEG was synthesized by exfoliating graphite oxide in H2 atmosphere at 200°C. The nanofluids were prepared by dispersing functionalized HEG (f-HEG) in DI water and EG without the use of any surfactant. HEG and f-HEG were characterized by powder X-ray diffractometry, electron microscopy, Raman and FTIR spectroscopy. Thermal and electrical conductivities of f-HEG dispersed DI water and EG based nanofluids were measured for different volume fractions and at different temperatures. A 0.05% volume fraction of f-HEG dispersed DI water based nanofluid shows an enhancement in thermal conductivity of about 16% at 25°C and 75% at 50°C. The enhancement in Nusselts number for these nanofluids is more than that of thermal conductivity. © 011 Baby and Ramaprabhu.
  • Placeholder Image
    Publication
    Enhanced optical limiting and carrier dynamics in metal oxide-hydrogen exfoliated graphene hybrids
    (21-12-2014)
    Anand, Benoy
    ;
    Kaniyoor, Adarsh
    ;
    Swain, Debasis
    ;
    Baby, Tessy Theres
    ;
    Rao, S. Venugopal
    ;
    Sai, S. Siva Sankara
    ;
    ;
    Philip, Reji
    Hydrogen exfoliated graphene (HEG) is an interesting class of few-layer graphene, which is synthesized via hydrogen induced simultaneous exfoliation-reduction of graphite oxide. HEG exhibits strong optical limiting (OL) due to defect states arising from a large number of structural defects as well as oxygen functionalities present on its surface. Recently, we have shown that OL in HEG can be improved by simple acid functionalization, as it results in an increased number of defects. In the present study, we demonstrate that the OL performance of functionalized HEG (f-HEG) can be further improved, in both the short-pulse (nanosecond) and ultrafast (femtosecond) laser excitation regimes, using hybrids of f-HEG with transition metal oxide nanoparticles (NPs) such as CuO. The enhancement in the OL efficiency of the hybrid arises from strong nonlinear absorption in CuO NPs, which is determined mostly by interband and intraband transitions. The presence of defect states in the samples is confirmed using ultrafast pump-probe measurements, which reveal a delayed carrier relaxation due to carrier trapping by these states. Furthermore, we show that the occurrence of induced thermal scattering is minimal in these water dispersed systems, such that OL occurs predominantly due to nonlinear absorption.
  • Placeholder Image
    Publication
    Investigation of thermal and electrical conductivity of graphene based nanofluids
    (15-12-2010)
    Baby, Tessy Theres
    ;
    We report for the first time, the synthesis of highly stable exfoliated graphene based nanofluids with water and ethylene glycol as base fluids with out any surfactant and the subsequent studies on their thermal and electrical conductivities. Graphene was synthesized by thermal exfoliation of graphene oxide at 1050 °C in Ar atmosphere. The as-synthesized graphene has been suitably functionalized and further dispersed it in the base fluids without any surfactant. Thermal and electrical conductivities of these nanofluids were measured for varying volume fractions and at different temperatures. An enhancement in thermal conductivity by about 14% has been achieved at 25 °C with deionized water (DI) as base fluid at a very low volume fraction of 0.056% which increases to about 64% at 50 °C. Electrical conductivity measurements for these nanofluids indicate an enormous enhancement at 25 °C for a volume fraction of 0.03%in DI water. © 2010 American Institute of Physics.
  • Placeholder Image
    Publication
    Synthesis and transport properties of metal oxide decorated graphene dispersed nanofluids
    (05-05-2011)
    Baby, Tessy Theres
    ;
    In the present work, a novel chemical reduction followed by calcination at considerably low temperature is used to synthesize copper oxide decorated graphene (CuO/HEG). Graphene has been synthesized via hydrogen induced exfoliation/reduction of graphite oxide. As-synthesized graphene is functionalized in acid medium to decorate copper oxide nanoparticles as well as to disperse it in polar medium. CuO/HEG is dispersed in deionized (DI) water and ethylene glycol without any surfactant, and the thermal transport properties of those nanofluids are studied. Thermal conductivity of CuO/HEG dispersed in DI water based nanofluid shows an enhancement of ∼28% at 25 AC for a volume fraction of 0.05%. In addition to thermal conductivity, the electrical conductivity of the nanofluids is also measured for different volume fractions at different temperatures. Heat transfer coefficient is measured in an indigenously fabricated setup for different volume fractions for different flow rates. © 2011 American Chemical Society.
  • Placeholder Image
    Publication
    Experimental investigation of the thermal transport properties of a carbon nanohybrid dispersed nanofluid
    (01-05-2011)
    Baby, Tessy Theres
    ;
    A hybrid nanostructure consisting of 1D carbon nanotubes and 2D graphene was successfully synthesized. Nanofluids were made by dispersing the hybrid nanostructure in deionized (DI) water and ethylene glycol (EG) separately, without any surfactant. Later the thermal conductivity and heat transfer coefficient of the nanofluids were experimentally measured. Meanwhile, multiwalled carbon nanotubes (MWNT) were prepared by catalytic chemical vapor deposition (CCVD), and hydrogen exfoliated graphene (HEG) was synthesized by exfoliating graphite oxide in a hydrogen atmosphere. The hybrid nanostructure (f-MWNT+f-HEG) of functionalized MWNT (f-MWNT) and functionalized HEG (f-HEG) was prepared by a post mixing technique, and the sample was characterized by powder X-ray diffraction, Raman spectroscopy, field emission scanning electron microscopy and transmission electron microscopy. Thermal conductivity of the nanofluids was measured for different volume fractions of f-MWNT+f-HEG at different temperatures. The hybrid nanostructure dispersed in the DI water based nanofluid shows a thermal conductivity enhancement of 20% for a volume fraction of 0.05%. Similarly, for a Reynolds number of 15500, the enhancement of the heat transfer coefficient is about 289% for a 0.01% volume fraction of f-MWNT+f-HEG. © 2011 The Royal Society of Chemistry.
  • Placeholder Image
    Publication
    Carbon nanostructure grown using bi-metal oxide as electrocatalyst support for proton exchange membrane fuel cell
    (20-05-2013)
    Puthusseri, Divya
    ;
    Baby, Tessy Theres
    ;
    Bhagavathi Parambhath, Vinayan
    ;
    Natarajan, Rajalakshmi
    ;
    A novel carbon nanostructure grown by catalytic chemical vapour deposition technique has been applied as an electrocatalyst support for oxygen reduction reaction in proton exchange membrane fuel cell. The growth of carbon nanostructure (CNS) is carried over a low cost bi-metal oxide catalyst (Fe-Sn-O) synthesized by sol-gel technique. Platinum nanoparticle decoration on Fe-Sn-O incorporated CNS (CNS-FSO) is performed by ethylene glycol reduction method. The structural as well as morphological analysis confirms the formation of CNS-FSO and platinum decoration on CNS-FSO. The electrochemically active surface area (ECSA) of platinum decorated CNS-FSO (Pt/CNS-FSO) is 68 m2 g -1, as revealed from cyclic voltammetry. Polarization studies are carried out at different temperatures (40 °C, 50 °C and 60 °C) to exploit the oxygen reduction reaction activity of Pt/CNS-FSO. A maximum power density of 449 mW cm-2 (without back pressure) at 60 °C shows the potential of this novel CNS-FSO as an electrocatalyst support in proton exchange membrane fuel cell. Copyright © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
  • Placeholder Image
    Publication
    Non-enzymatic glucose and cholesterol biosensors based on silica coated nano iron oxide dispersed multiwalled carbon nanotubes
    (01-12-2011)
    Baby, Tessy Theres
    ;
    We report for the first time a non-enzymatic glucose biosensor fabricated using monodispersed SiO 2 coated magnetic Fe 3O 4 dispersed multiwalled carbon nanotubes (Fe 3O 4@SiO 2/MWNT) which has been successfully tested for rapid detection of glucose without the interference due to uric and ascorbic acids. This super paramagnetic nanocomposite, Fe 3O 4@SiO 2/MWNT combines the excellent electron transfer properties of nano Fe 3O 4, biocompatibility of nano sized silica and electron transport properties of MWNT. The electrochemical performance of the non-enzymatic biosensor has been investigated by cyclic voltammetry and amperometric i-t studies. The linearity of fabricated electrode for glucose detection is 3 μM to 14 mM. The same material is used for nonenzymatic cholesterol biosensor also. It shows a detection range of 10 μM to 4mM towards cholesterol. Moreover, the electrodes show good detection limit, high sensitivity and good selectivity in both the cases. A thin coating of Nafion is used to avoid the interference due to uric acid (UA) and ascorbic acid (AA). © 2011 IEEE.
  • Placeholder Image
    Publication
    A cholesterol biosensor based on gold nanoparticles decorated functionalized graphene nanoplatelets
    (01-06-2011)
    Aravind, Sasidharan Sasikala Jyothirmayee
    ;
    Baby, Tessy Theres
    ;
    Arockiadoss, Thevasahayam
    ;
    Rakhi, Raghavan Baby
    ;
    The fabrication of a cholesterol biosensor using gold nanoparticles decorated graphene nanoplatelets has been reported. Thermally exfoliated graphene nanoplatelets act as a suitable support for the deposition of Au nanoparticles. Cholesterol biosensor electrodes have been constructed with nafion solubilized functionalized graphene nanoplatelets (f-G) as well as Au nanoparticles decorated f-G, immobilized over glassy carbon electrode. f-G and Au/f-G thin film deposited glassy carbon electrodes were further functionalized with cholesterol oxidase by physical adsorption. Au nanoparticles dispersed over f-G demonstrate the ability to substantially raise the response current. The fabricated electrodes have been tested for their electrochemical performance at a potential of 0.2 V. The fabricated Au/f-G based cholesterol biosensor exhibits sensitivity of 314 nA/μM cm2 for the detection of cholesterol with a linear response up to 135 μM. Furthermore, it has been observed that the biosensor exhibits a good anti-interference ability and favorable stability over a month's period. © 2011 Elsevier B.V. All rights reserved.
  • Placeholder Image
    Publication
    Non-enzymatic amperometric glucose biosensor from zinc oxide nanoparticles decorated multi-walled carbon nanotubes
    (01-12-2011)
    Baby, Tessy Theres
    ;
    The present work describes the development of novel ZnO dispersed multi-walled carbon nanotubes (MWNT) based non-enzymatic glucose biosensor with 1 M NaOH solution as the supporting electrolyte. For a comparison, the same material has been used for the fabrication of enzymatic biosensor and studied its electrochemical activity with phosphate buffer solution as the electrolyte. MWNT have been synthesized by catalytic chemical vapor decomposition (CCVD) and a simple sol-gel method was used for decorating crystalline ZnO nanoparticles on MWNT. Cyclic voltammetry and chronoamperometry were used to study and optimize the electrochemical performance of the resulting enzymatic and non-enzymatic ZnO/MWNT biosensors. The non enzymatic Nafion/ZnO/MWNT/GC electrode shows linearity in the range 700 nM to 31 mM with the detection limit of 500 nM. Similarly enzymatic biosensor fabricated using Nafion/GOD/ZnO/MWNT on glassy carbon electrode (GCE) shows a linearity from 1 μM to 22 mM. This excellent performance of non enzymatic Nafion/ZnO/MWNT/GC is due to high surface area, good electron transfer rate of ZnO/MWNT and the high electrochemical catalytic activity of ZnO in NaOH solution. Copyright © 2011 American Scientific Publishers.