Showing papers by "Sundara Ramaprabhu published in 2009"

Nanostructured Pt decorated graphene and multi walled carbon nanotube based room temperature hydrogen gas sensor

Abstract: Herein, we report the fabrication of hydrogen gas sensors based on noble nanometal decorated one dimensional multi walled carbon nanotubes and two dimensional graphene by a simple drop casting technique, with practical applications in view. Pt decorated functionalized graphene sheets (Pt/f-G) and Pt decorated functionalized multi walled carbon nanotubes (Pt/f-MWNT) were synthesized and employed as hydrogen sensors. Systematic investigation of hydrogen sensing, at a low detection level of 4 vol% hydrogen in air, of (Pt/f-G) reveals a response time comparable to that of (Pt/f-MWNT) but with a two fold increase in the sensitivity at room temperature. These sensors were also found to be stable over repeated cycles of hydrogenation and dehydrogenation.

Thermal conductivity studies of metal dispersed multiwalled carbon nanotubes in water and ethylene glycol based nanofluids

Abstract: High thermal conducting metal nanoparticles have been dispersed on the multiwalled carbon nanotubes (MWNTs) outer surface. Structural and morphological characterizations of metal dispersed MWNTs have been carried out using x-ray diffraction analysis, high resolution transmission electron microscopy, energy dispersive x-ray analysis, and Fourier transform infrared spectroscopy. Nanofluids have been synthesized using metal-MWNTs in de-ionized water (DI water) and ethylene glycol (EG) base fluids. It has been observed that nanofluids maintain the same sequence of thermal conductivity as that of metal nanoparticles Ag-MWNTs>Au-MWNTs>Pd-MWNTs. A maximum enhancement of 37.3% and 11.3% in thermal conductivity has been obtained in Ag-MWNTs nanofluid with DI water and EG as base fluids, respectively, at a volume fraction of 0.03%. Temperature dependence study also shows enhancement of thermal conductivity with temperature.

A glucose biosensor based on deposition of glucose oxidase onto crystalline gold nanoparticle modified carbon nanotube electrode.

Abstract: A new amperometric biosensor, based on deposition of glucose oxidase (GOD) onto crystalline gold (Au) nanoparticle modified multiwalled carbon nanotube (MWNT) electrode, is presented. MWNTs have been synthesized by catalytic chemical vapor decomposition of acetylene over rare-earth-based AB2 (DyNi2) alloy hydride catalyst. Purified MWNTs have been decorated with nanocrystalline Au metal clusters using a simple chemical reduction method. The characterization of metal-decorated CNTs has been done using X-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, and energy-dispersive X-ray analysis. Amperometric biosensor fabricated by depositing GOD over Nafion-solubilized Au−MWNT electrode retains its biocatalytic activity and offers fast and sensitive glucose quantification. The performance of the biosensor has been studied using cyclic voltammetry, amperometry, and hydrodynamic voltammetry, and the results have been discussed. The fabricated gluc...

A non-aqueous electrolyte-based asymmetric supercapacitor with polymer and metal oxide/multiwalled carbon nanotube electrodes

Abstract: A supercapacitor using non-aqueous electrolyte and multiwalled carbon nanotube (MWNTs) nanocomposite electrodes has been designed with polymer and metal oxide loaded carbon nanotubes as electrodes. These nanocomposites were coated on the carbon paper with Nafion solution to obtain the flexible electrodes. Carbon paper with the nanocomposite coating was pressed on either sides of the Nafion membrane, which acts both as a separator and as an electrolyte. The performance of asymmetric assembly of electrochemical double layer capacitor with polymer- and metal oxide-dispersed MWNTs composite materials with non-aqueous Nafion electrolyte is compared with symmetric assemblies, and the results are discussed.

Electron field emitters based on multi-walled carbon nanotubes coated with conducting polymer/metal/metal-oxide composites

Abstract: The present work describes the field emission properties of multi-walled nanotubes (MWNTs)-based conducting polymer/metal-oxide/metal/MWNTs composites (polyaniline (PANI)/SnO2/Sn/MWNTs). MWNTs were synthesised by chemical vapour deposition technique. SnO2/Sn/MWNTs were prepared by using chemical reduction followed by calcination. By in situ polymerisation method, surface of SnO2/Sn/MWNTs were coated with PANI. PANI/SnO2/Sn/MWNTs field emitters were fabricated over flexible graphitised carbon fabric substrate by spin coating technique. High-resolution transmission electron microscopy and scanning electron microscopy were used to characterise the field emitters. Field emission properties have been studied using an indigenously made facility. The fabricated PANI/SnO2/Sn/MWNTs field emitters exhibited excellent field emission properties with a turn on field of 1.83 V µm−1 and a field enhancement factor of 4800.

Development of MWNT based disposable biosensor on glassy carbon electrode for the detection of organophosphorus nerve agents.

Abstract: The development of a disposable Acetylcholinesterase (AChE) based biosensor is described. Synthesis, purification and further functionalization with oxygen containing hydrophilic functional groups of Carbon nanotubes (CNTs) have been detailed. Biosensing activity of functionalized multi walled carbon nanotubes (MWNTs) towards the detection of Organo phosphorus (OP) compound, paraoxon, has been tested using Amperometric method. Functional groups on the surface of MWNTs creates favorable surface for enzyme immobilization and enhances the enzyme electrode interaction by increasing the electron transfer rate due to high electrical conductivity of the MWNTs. Inhibition of AChE by paraoxon is determined by the decrease in catalytic activity of AChE. This results in less production of enzymatic product thiocholine, which leads to reduction in the electroxidation current. The ability of MWNTs based sensor to reliably measure concentration in the range 7 to 0.5 nM has been demonstrated. The detection limit of biosensor has been found to be as low as 0.5 nM.

Biological Sensors Using DNA Functionalized Multiwalled Carbon Nanotubes

Abstract: : In the first part of this work, electrochemical detecting behavior of MWNT functionalized with single strand DNA was studied. The MWNT was synthesized as described in the report. Purified MWNT was functionalized with aqua regia for dispersion improve combining capacity with the DNA. Special machine grade DNA [AC] 15 was used for functionalization of MWNT by sonication. Characterizations have been carried out using various techniques. Cyclic voltammetry gave well-defined quasi-reversible voltametric responses, showing that DNA-MWNT film is a good electrochemical sensor. Further, we demonstrate highly selective and sensitive detection of a low concentration of dopamine. In the second part of this work, a new amperometric biosensor, based on deposition of glucose oxidase (GOD) on to crystalline gold (Au) nanoparticle modified multi walled carbon nanotube (MWNT) electrode, is presented. Purified MWNTs were decorated with nanocrystalline Au metal clusters using a simple chemical reduction method. Amperometric biosensor fabricated by depositing glucose oxidase (GOD) over Nafion-solubilized Au/MWNT electrode retains its biocatalytic activity and offers fast and sensitive glucose quantification.