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Indian Journal of Chemistry

Sect. A: Inorganic, Bio-inorganic, Physical, Theoretical & Analytical

 

VOLUME 44A

NUMBER 5

May 2005

CONTENTS

 

861

 

Nanomaterials and electrochemistry — A review on some less familiar aspects

 

 

 

 

 

 

Wahid U Malik & Rajendra N Goyal*

 

 

 

Nanomaterials and their applications in electrochemistry in several less familiar aspects are described. The presence of nanomaterials at the electrode surface catalyzes the redox process of metal ions, complexes and biomolecules.

 

 

875

 

Advances in magnesium electrochemistry —
A challenge for nanomaterials

 

 

 

 

 

 

 

 

Doron Aurbach*, Yossi Gofer, Orit Chusid,
Elena Levi, Mikhail D Levi, Yulia Vestfrid,
Haim Gizbar & Eli Lancry

 

 

 

 

 

891

 

Electrochemistry at nanoelectrodes

 

 

 

 

 

Yunhua Wu & Shengshui Hu*

 

 

 

An overview of the electrochemistry at nanoelectrodes has been given. The major focus is on the fundamental advances of nanoelectrodes in electrochemistry, the fabrication of nanoelectrodes and their impact on electroanalytical chemistry.

899

 

Atomistic aspects of electrochemical alloy formation: A review of nucleation and growth of nano-clusters and thin films

 

 

 

 

 

 

 

 

 

 

 

 

 

Alexander Milchev* & Georgi Staikov

 

 

 

Atomistic aspects of electrochemical alloy formation are discussed on the basis of theoretical considerations and experimental results obtained in selected model systems. An experimental method to study the size and composition of critical alloy nuclei obtained at constant supersaturation is proposed and applied to mercury-silver clusters electrodeposited on a platinum single crystal electrode. Correlation between deposition conditions and the composition and properties of alloy coatings is demonstrated on the basis of data for the growth of Ag-Au alloy.

 

 

 

913

 

Development of electrocatalysts for direct alcohol fuel cells

 

 

 

 

 

Luhua Jiang, Shuqin Song, Zhenhua Zhou, Shiyou Yan, Huanqiao Li, Gongquan Sun,
Bing Zhou & Qin Xin*

 

 

 

The recent progress in electrocatalysts for direct alcohol fuel cells has been summarized, focussing on electrocatalysts for both alcohol oxidation and oxygen reduction. A modified ethylene polyol method to prepare well-dispersed nano-sized Pt-based electrocatalysts with high loadings is reported. The bimetallic electrocatalysts prepared by the modified EG method display uniform size and homogeneous components at nanometer scale.

 

 

 

924

 

Electrochemical characterisation of ultrathin carbon nanofiber– chitosan multi-layer films

 

 

 

 

 

 

 

 

Maria A Murphy, Geoff D Wilcox, Ralf H Dahm & Frank Marken*

 

 

 

A novel method for the layer-by-layer deposition of very thin layers of hydrophilised carbon nanofibers with a chitosan binder has been developed. Possible applications of the ultrathin carbon/chitosan deposits as transparent carbon electrodes are discussed.

 

 

932

 

Electrodeposition of gold nanorods with a uni-directional crystal growth and lower Au(111) facets area

 

 

 

 

 

 

 

 

 

Feifei Gao, Mohamed S El-Deab &
Takeo Ohsaka*

 

 

 

Stable Au nanorods with a uni-directional pin-like morphology have been prepared on the surface of glassy carbon electrodes via a potential-step electrodeposition method from H2SO4 solution containing Na[AuCl4]. In the presence of cysteine as an additive, there is significant enrichment of Au(100) and Au(110) facets in contrast to the spherical Au nanoparticles deposited in the absence of cysteine.

 

 

938

 

Electrochemical responses on gold nanoparticles directly attached indium tin oxide electrodes fabricated using a ‘touch’ seed-mediated growth method

 

 

 

 

Akrajas Ali Umar & Munetaka Oyama*

 

 

 

The   electrochemical   responses   of   hydroquinone  and
p-aminophenol in phosphate buffer solutions (pH 7.4) on gold nanoparticles directly attached indium tin oxide (AuNP/ITO) electrodes fabricated by a seed-mediated growth method are reported. The AuNP/ITO electrode fabricated via the ‘touch’ seeding and 24 h growth shows improved electrochemical responses, with peak separation values of 480 mV and 110 mV for hydroquinone and p-aminophenol, respectively.

 

 

945

 

Differential pulse voltammetric determination of uric acid at nanogold modified indium tin oxide (ITO) electrode

 

 

 

 

 

 

 

 

Rajendra N Goyal*, Munetaka Oyama,
Aditi Sangal & Sudhanshu P Singh

 

 

 

Uric acid has been determined at pH 7.2 (m = 0.1 M) at nanogold modified indium tin oxide electrode by differential pulse voltammetry.

 

 

 

950

 

Functionalization of carbon nanotubes for direct electrochemistry of horseradish peroxidase

 

 

 

 

 

Wei Zheng, Qingfen Li, Yiming Yan, Lei Su & Lanqun Mao*

 

 

 

 

 

956

 

Kinetic evaluation of the standard rate constant from cyclic voltammetric data at SWCNT–modified tungsten microelectrodes

 

 

 

 

 

 

 

 

 

 

 

 

A Curulli*, F Valentini, S Orlanducci &
M L Terranova

 

 

 

The electrochemical properties and the kinetic evaluation at single-walled carbon nanotubes-modified tungsten microelectrodes have been studied and compared with those of glassy carbon bare electrodes.

 

 

 

968

 

Proximity-induced superconductivity, spin entanglement and Luttinger liquid in carbon nanotubes prepared in alumina templates

 

 

 

 

I Takesue*, J Haruyama & N Kobayashi

 

 

 

Proximity-induced superconductivity has been observed in multi-walled carbon nanotubes (MWNTs) prepared in nanoporous alumina templates within a diffusive charge transport regime. As the 1D anisotropy of MWNTs becomes stronger, enhancement of spin entanglement in coherent electron pairs of the MWNT is observed.

975

 

Nano Si/G composite anode in Li ion battery for aerospace applications

 

 

 

Uday S Kasavajjula & Chunsheng Wang*

 

 

 

A composite anode material with composition, graphite-nano-silicon-ceramic-PEO+LiClO4 has been investigated for Li ion batteries. Its performance at different temperatures (from -40°0C to 45°0C) and current densities were using various electrochemical methods has been analyzed.

983

 

Novel Li-ion polymer batteries using LiFePO4 as positive electrode

0

 

 

K Zaghib*, P Charest, A Guerfi, R Veillette &
M Petitclerc

 

 

 

The aging and performance of natural graphite/PEO-based gel electrolyte/LiFePO4 cells have been reported. The Li-ion gel polymer battery shows a capacity fade of 13% after 180 cycles and has poor performance at low temperature. Li/polymer/LiFePO4 has an excellent stable cycle life.

 

 

989

 

Interactions between DNA and metal chelates at nanometer scale interface

 

 

 

 

 

 

 

 

Yan-Hua Bi, Bin Liang, Zhen-Li Huang,
Yuan-Di Zhao* & Zuo-Ning Gao

 

 

 

 

994

 

Preparation, characterization and electro-catalytic activity of phosphomolybdic acid embedded organic-inorganic nanocomposites



S Shanmugam, B Viswanathan* &
T K Varadarajan

 

 

 

Organic-inorganic nanocomposite containing Keggin polyoxometalate, H3PMo12O40, has been synthesized by sol-gel method. The prepared organic-inorganic nanocomposite has been employed for the reduction of nitrite in sulphuric acid medium. The electrode  response  is   linear  for  NO within  the  concentration  range  of
8.4 ´ 10-5 M to 15 ´ 10-3 M. The composite electrode has a sensitivity of 4.5 mA mM-1

 

 

1001

 

Kelvin probe force microscopy study on anodization-related variations of porous silicon nanostructures combined with photo-luminescence and Raman scattering

 

Ping He & Jinghong Li*

 

 

 

Microscopic structure of as-anodized porous silicon obtained at different current densities and anodization time has been studied using photoluminescence, Kelvin probe force microscopy and Raman scattering. A blue-shift of the photoluminescence band is observed on increasing the current density while a red-shift is observed on increasing the anodization time in the electrochemical etching process.

 

 

1009

 

Pt-Ru electrodeposition on nanofibrous polyaniline and their electrocatalytic properties for methanol oxidation

 

 

H H Zhou, X H Ning, J H Chen, W Z Wei &
Y F Kuang*

 

 

 

Pt-Ru microparticles have been electrodeposited by the pulse galvanostatic method onto nanofibrous polyaniline  film synthesized directly onto stainless steel. This electrode exhibits a considerably high electrocatalytic activity for methanol oxidation. The effects of the ratio of Pt to Ru, deposition charge of Pt-Ru, temperature, scan rate and methanol concentration on electrocatalytic acitivity have been evaluated. The activation energy of methanol oxidation on the electrode is 22.18 kJ mol-1.

 

 

1016

 

Electrochemical generation of silver nanowires

 

Xiangqin Lin* & Shuqing Wang

 

 

 

Novel silver nanowires, about 30-40 nm in diameter, have been successfully fabricated by electrochemical reduction in aqueous solution of poly(methacrylic acid) at room temperature. Different morphologic silver products have been obtained by adjusting the polymer concentration.

Authors for correspondence are indicated by (*)


Indian Journal of Chemistry

Vol. 44A, May 2005, pp. 861-874

 

Nanomaterials and electrochemistry — A review on some less familiar aspects

Wahid U Malik & Rajendra N Goyal*

Department of Chemistry, Indian Institute of Technology, Roorkee 247 667, India

Email: rngcyfcy@iitr.ernet.in

Received 27 December 2004

Nanomaterials and their applications in various less familiar aspects are described here. The presence of nanomaterials at the electrode surface has been found to catalyze the redox process of metal ions, complexes and biomolecules.

IPC Code: Int. Cl.7 B82B; C25B

Indian Journal of Chemistry

Vol. 44A, May 2005, pp. 875-890

 

Advances in magnesium electrochemistry¾A challenge for nanomaterials

Doron Aurbach*, Yossi Gofer, Orit Chusid, Elena Levi, Mikhail D Levi, Yulia Vestfrid, Haim Gizbar & Eli Lancry

Department of Chemistry, Bar-Ilan University, Ramat-Gan 52900, Israel

Email: aurbach@mail.biu.ac.il

Received 23 December 2004

In this review, very recent studies related to magnesium electrochemistry (in connection with R&D of Mg batteries) have been reported. These include the study of new electrolyte solutions, based on complexes with the formal stoichiometry, Mg(AlCl4-nRn)2 in ethers, their unique structures and analysis by electrochemical and spectroscopic methods, the study of Mg deposition processes by microelectrodes and microscopy, and the study of Mg insertion into hosts based on the so-called Chevrel phase structure (Mg0-2­Mo6X8, X=S, Se). The ionic mobility of Mg2+ ions and their ease of diffusion within these structures are discussed. It is demonstrated that the use of a nanostructured active mass may be highly important for reducing the diffusion length considerably, and hence, for increasing the kinetics of transport of the bivalent cations. We deal herein with some key factors that may affect the possibility of smooth and reversible Mg insertion into inorganic host materials, and the possible advantages in the use of nanoparticles for these systems.

IPC Code: Int. Cl.7 B82B; C25B9/10

Indian Journal of Chemistry

Vol. 44A, May 2005, pp. 891-898

 

Electrochemistry at nanoelectrodes

Yunhua Wu1, 2  & Shengshui Hu1, 2, *

1Department of Chemistry, Wuhan University, Wuhan 430072, PR China

2State Key Laboratory of Transducer Technology, Chinese Academy of Sciences, Beijing 100080, PR China

Email: sshu@whu.edu.cn

Received 2 November 2004

This review article gives an overview of the electrochemistry at nanoelectrodes. The major focus is on the fundamental advances of nanoelectrodes in electrochemistry, the fabrication of nanoelectrodes and their impact on the practice of electroanalytical chemistry.

IPC Code: Int. Cl.7 B82B; C25B; H01M4/00

 

Indian Journal of Chemistry

Vol. 44A, May 2005, pp. 899-912

 

Atomistic aspects of electrochemical alloy formation: A review of nucleation and growth of nano-clusters and thin films

Alexander Milcheva, * & Georgi Staikovb

aRostislav Kaischev Institute of Physical Chemistry, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
Email: amilchev@ipchp.ipc.bas.bg

bInstitute of Thin Films and Interfaces (ISG 3), and cni-Centre of  Nanoelectronic Systems for Information Technology,
Research Centre Jülich, D-52425 Jülich, Germany
Email: g.staikov@fz-juelich.de

Received 25 November 2004

Atomistic aspects of electrochemical alloy formation are reviewed and discussed on the basis of theoretical considerations and experimental results obtained in selected model systems. The role of interactions between co-deposited metal atoms, as well as metal-substrate interactions during the initial stages of electrochemical co-deposition has been discussed. Nucleation kinetics in binary alloy systems is considered theoretically, applying the atomistic approach. Experimental data on the nucleation rate, the size and the composition of Ag-Hg alloy nuclei electrodeposited on a platinum electrode are presented and discussed in detail. The formation of surface alloys is discussed in terms of models including place exchange between metal adatoms and substrate atoms, solid state diffusion and nucleation and growth phenomena. The correlation between the deposition conditions and the composition and properties of alloy coatings obtained in the advanced stages of electrochemical alloy formation is demonstrated on the basis of experimental data for the growth of Ag-Au alloy.

IPC Code: Int. Cl.7 B82B; C25B; C25D3/56

Indian Journal of Chemistry

Vol. 44A, May 2005, pp. 913-923

 

Development of electrocatalysts for direct alcohol fuel cells

Luhua Jianga, Shuqin Songa, Zhenhua Zhoua, b, Shiyou Yana, Huanqiao Lia,
Gongquan Suna, Bing Zhoua, b & Qin Xina, c,*

aDirect Alcohol Fuel Cell Laboratory, cState Key Laboratory of Catalysis,
Dalian Institute of Chemical Physics, Graduate School of the Chinese Academy of Sciences, CAS, China

bHeadwater NanoKinetix, 1501 New York Avenue, Lawrenceville, NJ 08648, USA

Email: xinqin@dicp.ac.cn

Received 17 November 2004

In the present review, we summarize the recent progress in electrocatalysts for direct alcohol fuel cells, focussing on the research of electrocatalysts for both alcohol oxidation and oxygen reduction, which are crucial in the development of fuel cells. A modified EG (ethylene polyol) method to prepare well-dispersed nano-sized Pt-based electrocatalysts with high loadings is reported. By this method, a more active carbon supported PtRu catalyst for methanol oxidation reaction and a PtSn catalyst for ethanol oxidation reaction have been synthesized successfully. Furthermore, a methanol tolerant Pd-based catalyst for cathode oxygen reduction reaction has been developed. HRTEM and HR-EDS have been employed to characterize the microstructure and micro-components of the above electrocatalysts. Results show that the bimetallic electrocatalysts prepared by the modified EG method display uniform size and homogeneous components at nanometer scale.

IPC Code: Int. Cl.7 B82B; C25B; H01M8/00; B01J23/14; B01J23/40

Indian Journal of Chemistry

Vol. 44A, May 2005, pp. 924-931

 

Electrochemical characterisation of ultrathin carbon nanofiber-chitosan
multi-layer films

Maria A Murphya, Geoff D Wilcox, Ralf H Dahma & Frank Markenb, *

a Institute of Polymer Technology and Materials Engineering, Loughborough University, Loughborough, Leicestershire, LE11 3TU, UK

b Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK

Email: F.Marken@bath.ac.uk

Received 31 October 2004

Carbon nanofibers can be oxidized and solubilised in alkaline or neutral aqueous media. Deposition of the solution by solvent evaporation allows well-defined amounts of carbon nanofiber material to be deposited onto tin-doped indium oxide (ITO) electrodes and studied electrochemically. Next, a layer-by-layer deposition process is employed to produce homogeneous and ultrathin films of carbon nanofibers with a chitosan binder with controlled thickness. Films with a thickness similar to the nanofiber diameter, 50-200 nm, are produced and characterized via electron microscopy, conductivity measurements, and quartz crystal microbalance gravimetry. Electrochemically, even very thin films of hydrophilised carbon nanofibers are readily detected due to their (pseudo-)capacitive current response (ca. 150 F g-1 over a limited potential range). Electrochemical reactions, such as the oxidation of hydroquinone in aqueous phosphate buffer, are shown to be catalysed by the presence of hydrophilised carbon nanofiber fragments (with respect to the same process at a bare ITO electrode). Based on voltammetric responses, the electron transfer across a barrier between carbon nanofibers and the ITO substrate is identified as rate limiting in the presence of chitosan. Possible applications of ultrathin carbon/chitosan deposits, for example as transparent carbon electrodes, are discussed.

IPC Code: Int. Cl.7 B82B; C25B

Indian Journal of Chemistry

Vol. 44A, May 2005, pp. 932-937

 

Electrodeposition of gold nanorods with a uni-directional crystal

growth and lower Au(111) facets area

 

Feifei Gao1, Mohamed S El-Deab2 & Takeo Ohsaka*

Department of Electronic Chemistry, Interdisciplinary Graduate School of Science and Engineering,
Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502, Japan

Email: ohsaka@echem.titech.ac.jp

Received 11 November 2004

Stable Au nanorods with a uni-directional pin-like morphology have been prepared on the surface of glassy carbon (GC) electrodes via a potential-step electrodeposition method from H2SO4 solution containing Na[AuCl4] in the presence of cysteine as an additive. The Au nanorods are characterized by a relatively low Au(111) facets area because of a continuous uni-directional growth of the crystal along the (111) orientation leading to a pin-like morphology of the crystals. In other words, there is a significant enrichment of Au(100) and Au(110) facets in contrast to the spherical Au nanoparticles prepared in the absence of cysteine. The peak potential of the oxygen reduction reaction, measured in O2-saturated 0.5 M H2SO4, at the thus-prepared Au nanorods electrodeposited onto glassy carbon (nano-Au/GC) electrodes shows a significant positive shift compared to that obtained at the nano Au/GC electrode prepared in the absence of cysteine, demonstrating a higher electrocatalytic activity of these Au nanorods.

IPC Code: Int. Cl.7 B82B; C25B; C25D

Indian Journal of Chemistry

Vol. 44A, May 2005, pp. 938-944

 

Electrochemical responses on gold nanoparticles directly attached indium tin oxide electrodes fabricated using a ‘touch’ seed-mediated growth method

 

Akrajas Ali Umara & Munetaka Oyamab,*

aVenture Business Laboratory, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan

bDivision of Research Initiatives, International Innovation Center, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan

Email: oyama@iic.kyoto-u.ac.jp

Received 2 November 2004

The electrochemical responses of hydroquinone and p-aminophenol in phosphate buffer solutions (pH 7.4) on gold nanoparticles directly attached indium tin oxide (AuNP/ITO) electrodes fabricated by a seed-mediated growth method are reported. Although the electron transfer reactions of these compounds are sluggish on the bare ITO electrode, improved electrochemical responses are observed on the AuNP/ITO electrodes, in particular, on those fabricated with the ‘touch’ seed-mediated growth method. In this method, by touching a seed solution containing 4 nm AuNP onto an ITO surface with a tissue paper, the attachment of Au seed is promoted. The AuNP/ITO electrode fabricated via the ‘touch’ seeding and 24 h growth shows better improved electrochemical responses, with peak separation values of 480 mV and 110 mV for hydroquinone and p-aminophenol, respectively. The degree of improvement has been compared with the previous results reported for the Au-sputtered ITO electrodes. Advantages of this new type of nanoelectrode ensembles are described.

IPC Code: Int. Cl.7 B82B; C25B; H01M4/48

Indian Journal of Chemistry

Vol. 44A, May 2005, pp. 945-949

 

Differential pulse voltammetric determination of uric acid at nanogold modified indium tin oxide (ITO) electrode

Rajendra N Goyal*, Munetaka Oyamaa, Aditi Sangal & Sudhanshu P Singh

Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee 247 667, India

Email: rngcyfcy@iitr.ernet.in

aDivision of Research Initiatives, International Innovation Center, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan

Received 15 December 2004

The determination of uric acid has been carried out at pH 7.2 (m = 0.1 M) at nanogold modified indium tin oxide electrode by differential pulse voltammetry in absence and presence of ascorbic acid and other common interferents. A well - defined oxidation peak has been observed at around 840 mV vs Ag/AgCl electrode for uric acid at pH 7.2. The plot of peak current versus concentration plot is linear in the range 0.5 – 100 mM with a correlation coefficient of 0.995 and a sensitivity of 0.0004 nA/mM. The detection limit (3s) is found to be 0.5 mM. Ascorbic acid in concentrations lower than 10 mM does not interfere, whereas, at higher concentrations it interferes. Xanthine, hypoxanthine and adenine do not interfere even at eight-fold excess. The method is simple and convenient with the only limitation that the electrode cannot be used more than eight times.

IPC Code: Int. Cl.7 B82B; C25B; G01N27/00; H01M4/48

 

Indian Journal of Chemistry

Vol. 44A, May 2005, pp. 950-955

 

Functionalization of carbon nanotubes for direct electrochemistry of
horseradish peroxidase

Wei Zheng1, Qingfen Li1, Yiming Yan2, Lei Su2 & Lanqun Mao2, *

1School of Mechanical and Electrical Engineering, Harbin Engineering University, Harbin 150001, PR China

2Center for Molecular Science, Institute of Chemistry, The Chinese Academy of Sciences, Beijing 100080, PR China

Email: lqmao@iccas.ac.cn

Received 9 November 2004

New strategies for functionalization of carbon nanotubes (CNTs) for facilitating direct electron transfer of horseradish peroxidase (HRP) are reported. The CNTs are covalently functionalized with hydroxyl and carboxyl groups and noncovalently functionalized with block copolymer (Pluronic P123). The functionalized CNTs are found to possess an improved solubility in aqueous solution and may have an enhanced biocompatibility with biomacromolecules such as proteins and enzymes. Moreover, all the functionalized CNTs have been demonstrated for the first time to be capable of facilitating the direct electron transfer of HRP, in which the noncovalently P123-functionalized CNTs are shown to be advantageous over those covalently functionalized with –OH and –COOH groups. The catalytic activities of HRP adsorbed onto the P123-functionalized CNTs towards the reductions of dioxygen (O2) and hydrogen peroxide (H2O2) are also discussed.

IPC Code: Int. Cl.7 B82B; C25B

 

Indian Journal of Chemistry

Vol. 44A, May 2005, pp. 956-967

 

Kinetic evaluation of the standard rate constant from cyclic voltammetric data at SWCNT-modified tungsten microelectrodes

A Curulli1, *, F Valentini2, S Orlanducci2, 3 & M L Terranova2, 3

1 Istituto Materiali Nanostrutturati (ISMN) CNR Division 2, via del Castro Laurenziano 7, 00161 Rome, Italy
2Dipartimento di Scienze e Tecnologie Chimiche Università degli Studi di Roma Tor Vergata,
via della Ricerca Scientifica 1, 00133 Rome, Italy
3 INSTM (Consorzio Nazionale Scienze e Tecnologie dei Materiali) Università degli Studi di Roma Tor Vergata,
via della Ricerca Scientifica 1, 00133 Rome, Italy

Email: antonella.curulli@uniroma1.it

Received 9 November 2004

The electrochemical properties and the kinetic evaluation at Single-Walled Carbon Nanotubes (SWCNTs) -modified tungsten (W) microelectrodes have been studied and compared with those of Glassy Carbon (GC) bare electrodes. Field Emission Scanning Electron Microscopy (FEG-SEM) and Raman spectroscopy have been used to characterize the modified-electrode morphology and microstructure, respectively. Cyclic voltammetry (CV) has been used to study the electrochemical performances, with seven different redox systems serving as probes (Fe(CN)63-/4-; Ru(NH3)63+/2+, Ir(Cl)62-/3-, catechol, dopamine, ferrocene monocarboxylic acid and caffeic acid). The analytical response for different systems is highly reproducible for each type of tungsten microelectrode modified with SWCNT coating by Chemical Vapor Deposition method (CVD). For all seven redox systems, the forward reaction peak current varies linearly with the square root of scan rate (v)1/2, indicative of electrode reaction kinetics controlled by mass transport (semi-infinite linear diffusion) of the reactant. Apparent heterogeneous electron-transfer rate constants, K°app, for all seven redox systems have been determined from DEp-v experimental data, according to the method described by Nicholson. K°app values of 1.02-1.17 cm/s have been observed for Ru(NH3)63+/2+, Ir(Cl)62-/3-, and Fe(CN)63-/4- without any extensive electrode pretreatment (e.g., polishing). Lower K°app values of 10-6-10-2 cm/s have been found for catechol, dopamine, ferrocene monocarboxylic acid, and caffeic acid. The voltammetric responses for Ru(NH3)63+/2+, Ir(Cl)62-/3, and Fe(CN)63-/4- have also been examined at SWCNT- modified W electrodes in different solutions pH (1.1 –10.0), and the corresponding DEp, ipox; ipred; and K°app values for the most part, have been unaffected by the solution pH. This is probably related to the absence of oxygen-functionalities at SWCNT-modified W microelectrodes, which is in contrast to the typical behavior of the oxygenated, sp2 carbon electrodes, such as glassy carbon or graphite.

IPC Code: Int. Cl.7 B82B; C25B; H01M4/00; G01N27/00

 

Indian Journal of Chemistry

Vol. 44A, May 2005, pp. 968-974

 

Proximity-induced superconductivity, spin entanglement and Luttinger liquid in carbon nanotubes prepared in alumina templates

I Takesue1, 2, *, J Haruyama1, 2 & N Kobayashi1

1Aoyama Gakuin University, 5-10-1 Fuchinobe, Sagamihara, Kanagawa 229-8558, Japan

2 JST, CREST, 4-1-8 Hon-machi, Kawaguchi, Saitama 332-0012, Japan

Email: takesue@ee.aoyama.ac.jp

Received 8 December 2004

Proximity-induced superconductivity has been observed in multi-walled carbon nanotubes (MWNTs), prepared in nanoporous alumina templates, within a diffusive charge transport regime. As the 1D anisotropy of MWNTs becomes stronger, enhancement of spin entanglement in coherent electron pairs of the MWNT is observed. On reducing the length of the MWNT below a mean free path, it exhibits Tomonaga-Luttinger liquid behaviour. The study indicates a possibility that Cooper pairs, injected from a superconductor electrode are separated into individual spin by the TLL behaviour of MWNTs.

IPC Code: Int. Cl.7 B82B; C25B; C04B35/00

Indian Journal of Chemistry

Vol. 44A, May 2005, pp. 975-982

 

Nano Si/G composite anode in Li ion battery for aerospace applications

Uday S Kasavajjula & Chunsheng Wang*

Department of Chemical Engineering, Tennessee Technological University, Cookeville, TN-38505, USA.

E-mail:  cswang@tntech.edu

Received 20 December 2004

A composite anode material with a composition of graphite-nano-silicon-ceramic-PEO+LiClO4 has been investigated for Li ion batteries, and its performance at different temperatures (from -40°0C to 45°0C) and current densities were analyzed using various electrochemical methods. Electrochemical behavior of composite anodes with different Si and ceramic compositions were has been studied using galvanostatic charge-discharge cycling, and AC impedance analysis. Composite anode with a composition of Ggraphite (50%)-nano Si (10%)-Cceramic (20%)-PEO+LiClO4 (20%) (Wt %) showsed a stable reversible capacity of 300 mAh/g over 50 cycles at room temperature, and a reversible capacity of 160 mAh/g at -30°0C. Enhanced low temperature performance was has been observed due to the addition of ceramic, which in turn increasesd the Li ion conductivity of the anode and hence resulted resulting in improved charge transfer kinetics.

IPC Code: Int. Cl.7 B82B; H01M4/40; C04B35/71

 

Indian Journal of Chemistry

Vol. 44A, May 2005, pp. 983-988

 

Novel Li-ion polymer batteries using LiFePO4 as positive electrode

K Zaghib*, P Charest, A Guerfi, R Veillette & M Petitclerc

Institut de Recherche d’Hydro-Québec, 1800 Lionel-Boulet, Varennes, QC, J3X 1S1, Canada

Email : karimz@ireq.ca

Received 8 January 2005

The aging and performance of natural graphite/PEO-based gel electrolyte/LiFePO4 cells have been reported. The gel polymer electrolytes have been produced by electron-beam irradiation and then soaked in a liquid electrolyte. The natural graphite anode in gel electrolyte containing LiBF4-EC/GBL exhibits high reversible capacity (345mAh/g) and high coulombic efficiency (91%). The LiFePO4 cathode in the same gel-polymer exhibits a reversible capacity of 150 mAh/g and 83% coulombic efficiency. Better performance has been obtained at high-rate discharge with 6% carbon additive in the cathode. However, the graphite anode performance suffers at high rate. The Li-ion gel polymer battery shows a capacity fade of 13% after 180 cycles and has poor performance at low temperature. Li/polymer/LiFePO4 has an excellent stable cycle life.

IPC Code: Int. Cl.7 C25B; H01M4/40

Indian Journal of Chemistry

Vol. 44A, May 2005, pp. 989-993

 

Interactions between DNA and metal chelates at nanometer scale interface

 

Yan-Hua Bia, Bin Liangb, Zhen-Li Huanga, Yuan-Di Zhaoa, * & Zuo-Ning Gaob

aKey Laboratory of Biomedical Photonics of Ministry of Education, Huazhong University of Science & Technology,
Wuhan, HuBei 430074, PR China

bDepartment of Chemistry, Ningxia University, Yinchuan, NingXia 750021, PR China

Email: zydi@mail.hust.edu.cn

Received 6 November 2004

Interactions between double-stranded DNA (dsDNA) and [Co(phen)3]3+/2+ (Phen=1,10-phenanthroline) at multiwalled carbon nanotubes (MWCNTs)-based nanometer-scale size interface have been studied by the cyclic voltammetry. The results demonstrate that the interactions between dsDNA and [Co(phen)3]3+/2+ increase considerably at MWCNTs-based nanoscale size interface as compared to those at common large size interface. At MWCNTs nanoscale size interface, the binding constant of [Co(phen)3]2+ with dsDNA [kA= (2.53±0.22)´104 Lmol-1] is greater than that obtained at large size interface [(1.68±0.15)´104 Lmol-1]. The dissociation rate constant for [Co(phen)3]2+ bound to dsDNA at large size interface is 0.16 min-1, which is also considerably larger than that obtained at nanoscale size interface (0.0025 min-1). The study reveals that the interactions of DNA with small molecules increase remarkably at nano size interface as compared with those at normal electrodes.

IPC Code: Int. Cl.7 B82B; C25B; G01N27/00; H01M4/00

Indian Journal of Chemistry

Vol. 44A, May 2005, pp. 994-1000

 

Preparation, characterization and electrocatalytic activity of
phosphomolybdic acid embedded organic-inorganic nanocomposites

S Shanmugam, B Viswanathan* & T K Varadarajan

Department of Chemistry, Indian Institute of Technology Madras, Chennai 600 036, India

Email: bviswanathan@hotmail.com

Received 23 January 2005

Organic-inorganic nanocomposite containing Keggin polyoxometalate, H3PMo12O40 has been designed and synthesized by sol-gel method. The embedded polyoxometalate has been characterized by various physico-chemical techniques like TGA, SEM, TEM, cyclic voltammetry and IR, UV-visible and electrochemical impedance spectroscopy. Detailed electrochemical studies have been carried out. Effects of pH, potential variation and stability have been studied. The prepared organic-inorganic nanocomposite has been employed for the reduction of nitrite in sulphuric acid medium by using cyclic voltammetric and chronoamperometric methods. The electrode response has been found to be linear for NO2- within the concentration range of 8.4 ´ 10-5 M to 15 ´ 10-3 M. The composite electrode has a sensitivity of 4.5 mA mM-1.

IPC Code: Int. Cl.7 B82B; C25B; C04B85/17

Indian Journal of Chemistry

Vol. 44A, May 2005, pp. 1016-1018

 

Pt-Ru electrodeposition on nanofibrous polyaniline and their electrocatalytic properties for methanol oxidation

H H Zhoua, X H Ninga, J H Chenb, W Z Weib & Y F Kuanga, *

aCollege of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, PR China

bState Key Laboratory of Chemo/Biosensing and Chemometrics. Changsha 410082, PR China

Email: yafeik@163.com

Received 10 December 2004

Pt-Ru microparticles have been electrodeposited by the pulse galvanostatic method onto nanofibrous polyaniline (PANI) film synthesized directly onto stainless steel (SS). The Pt-Ru/nanofibrous PANI/SS electrode has been characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy. Electrocatalytical properties of the Pt-Ru/nanofibrous PANI/SS electrode have been investigated by cyclic voltammetry in 1 M CH3OH+0.5 M H2SO4 solution. The results show that the electrode exhibits a considerably high electrocatalytic activity for methanol oxidation. The effects of the ratio of Pt to Ru, deposition charge  of Pt-Ru, temperature, scan rate and methanol concentration have been evaluated. The activation energy of methanol oxidation on the electrode has been found to be 22.18 kJ mol-1.

IPC Code: Int. Cl.7  B82B; C25B; C25D

Indian Journal of Chemistry

Vol. 44A, May 2005, pp. 1016-1018

 

Electrochemical generation of silver nanowires

 

Xiangqin Lin* & Shuqing Wang

Department of Chemistry, University of Science and Technology of China, Hefei, Anhui 230026, PR China

Email: xqlin@ustc.edu.cn

Received 11 December 2004

Novel silver nanowires about 30-40 nm in diameter have been successfully fabricated by electrochemical reduction in aqueous solution of poly(methacrylic acid) at room temperature. Different morphologic silver products have been obtained by adjusting the polymer concentration. Field emission scanning electron microscopy and X-ray photoelectron spectroscopy have been used to characterize the obtained silver products. The possible formation mechanism is discussed. The synthesis process provides a facile method for low temperature solution growth of metal nanowires.

IPC Code: Int. Cl.7 B82B; C25B; C25D1/04; H01M4/75