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1.
K Kiruthiga P Aravindan S Anandan P Maruthamuthu 《Research on Chemical Intermediates》2006,32(2):115-135
N,N,N′,N′-Tetramethylbenzidine (TMB) is an aromatic amine that undergoes oxidation by various oxidizing agents such as Ce4+, MnO−4, Cr2O2−7; HSO−5, S2O−8, H2O2, Cl2, Br2 and I2, thereby serving as a reducing substrate. One-electron oxidation of TMB results in a radical cation (TMB˙+), and on further oxidation leads to the product dication (TMB++) were monitored by stopped-flow spectrophotometer at the absorption wavelength of TMB˙+(λmax; 460 nm). ESR data was also provided to confirm the formation of radical cation. The rates of both the formation and decay
of TMB˙+ have been followed by a total second-order kinetics, a first-order dependence each on [TMB] (or) [TMB˙+] and [oxidant]. The kinetic and transition state parameters have been evaluated for the effects of pH and temperature on
the formation and decay of TMB˙+ and discussed with suitable reaction mechanisms. Also, the rate constants for the reactions of the radical cation with various
reducing agents such as sulfite (SO2−3), thiosulfate (S2O2−3), dithionite (S2O2−4) and disulfite (S2O2−5) and ascorbic acid (vitamin C, AH2 were determined. Besides these, this article also explains how TMB acts as a better electron relay than unsubstituted benzidine,
even though both of them undergo one-electron oxidation and are used in the chemical routes to solar energy conversions. The
observed rate constants for electron transfer were correlated theoretically using Marcus theory. The observed and calculated
rate constants have good correlation. 相似文献
2.
Carbon‐Coated LiTi2(PO4)3: An Ideal Insertion Host for Lithium‐Ion and Sodium‐Ion Batteries 下载免费PDF全文
Dr. Vanchiappan Aravindan Dr. Wong Chui Ling Steffen Hartung Nicolas Bucher Prof. Srinivasan Madhavi 《化学:亚洲杂志》2014,9(3):878-882
We report the extraordinary performance of carbon‐coated sodium super ion conductor (NASICON)‐type LiTi2(PO4)3 as an ideal host matrix for reversible insertion of both Li and Na ions. The NASICON‐type compound was prepared by means of a Pechini‐type polymerizable complex method and was subsequently carbon coated. Several characterization techniques such as XRD, thermogravimetric analysis (TGA), field‐emission (FE) SEM, TEM, and Raman analysis were used to study the physicochemical properties. Both guest species underwent a two‐phase insertion mechanism during the charge/discharge process that was clearly evidenced from galvanostatic and cyclic voltammetric studies. Unlike that of Li (≈1.5 moles of Li), Na insertion exhibits better reversibility (≈1.59 moles of Na) while experiencing a slightly higher capacity fade (≈8 % higher than Li) and polarization (780 mV) than Li. However, excellent rate capability profiles were noted for Na insertion relative to its counterpart Li. Overall, the Na insertion properties were found to be superior relative to Li insertion, which makes carbon‐coated NASICON‐type LiTi2(PO4)3 hosts attractive for the development of next‐generation batteries. 相似文献
3.
In the present paper, we describe utilization of cathode active material as anode active material, for example, Li2MnSiO4. The lithium manganese silicate has been successfully synthesized by solid-state reaction method. The X-ray diffraction pattern
confirms the orthorhombic structure with Pmn2
1 space group. The Li/Li2MnSiO4 cell delivered the initial discharge capacity of 420 mA h g−1, which is 110 mA h g−1 higher than graphitic anodes. The electrochemical reversibility and solid electrolyte interface formation of the Li2MnSiO4 electrode was emphasized by cyclic voltammetry. 相似文献
4.
Synthesis of 2D/2D Structured Mesoporous Co3O4 Nanosheet/N‐Doped Reduced Graphene Oxide Composites as a Highly Stable Negative Electrode for Lithium Battery Applications 下载免费PDF全文
Palanichamy Sennu Hyo Sang Kim Jae Youn An Dr. Vanchiappan Aravindan Prof. Yun‐Sung Lee 《化学:亚洲杂志》2015,10(8):1776-1783
Mesoporous Co3O4 nanosheets (Co3O4‐NS) and nitrogen‐doped reduced graphene oxide (N‐rGO) are synthesized by a facile hydrothermal approach, and the N‐rGO/Co3O4‐NS composite is formulated through an infiltration procedure. Eventually, the obtained composites are subjected to various characterization techniques, such as XRD, Raman spectroscopy, surface area analysis, X‐ray photoelectron spectroscopy (XPS), and TEM. The lithium‐storage properties of N‐rGO/Co3O4‐NS composites are evaluated in a half‐cell assembly to ascertain their suitability as a negative electrode for lithium‐ion battery applications. The 2D/2D nanostructured mesoporous N‐rGO/Co3O4‐NS composite delivered a reversible capacity of about 1305 and 1501 mAh g?1 at a current density of 80 mA g?1 for the 1st and 50th cycles, respectively. Furthermore, excellent cyclability, rate capability, and capacity retention characteristics are noted for the N‐rGO/Co3O4‐NS composite. This improved performance is mainly related to the existence of mesoporosity and a sheet‐like 2D hierarchical morphology, which translates into extra space for lithium storage and a reduced electron pathway. Also, the presence of N‐rGO and carbon shells in Co3O4‐NS should not be excluded from such exceptional performance, which serves as a reliable conductive channel for electrons and act as synergistically to accommodate volume expansion upon redox reactions. Ex‐situ TEM, impedance spectroscopy, and XPS, are also conducted to corroborate the significance of the 2D morphology towards sustained lithium storage. 相似文献
5.
Aravindan V Gnanaraj J Madhavi S Liu HK 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(51):14326-14346
This paper presents an overview of the various types of lithium salts used to conduct Li(+) ions in electrolyte solutions for lithium rechargeable batteries. More emphasis is paid towards lithium salts and their ionic conductivity in conventional solutions, solid-electrolyte interface (SEI) formation towards carbonaceous anodes and the effect of anions on the aluminium current collector. The physicochemical and functional parameters relevant to electrochemical properties, that is, electrochemical stabilities, are also presented. The new types of lithium salts, such as the bis(oxalato)borate (LiBOB), oxalyldifluoroborate (LiODFB) and fluoroalkylphosphate (LiFAP), are described in detail with their appropriate synthesis procedures, possible decomposition mechanism for SEI formation and prospect of using them in future generation lithium-ion batteries. Finally, the state-of-the-art of the system is given and some interesting strategies for the future developments are illustrated. 相似文献
6.
S. Sankarrajan S. Aravindan R. Yuvakkumar K. Sakthipandi V. Rajendran 《Journal of magnetism and magnetic materials》2009,321(21):3611-3620
Nd1−xSrxMnO3 perovskite manganite material with different compositions (x=0.31, 0.35, 0.37, 0.39 and 0.41) have been prepared employing solid-state reaction technique. The ultrasonic velocities and attenuation of the above samples have been measured employing through transmission method operated at a fundamental frequency of 5 MHz over wide range of temperatures. The temperature dependence of ultrasonic velocities, attenuation, relative percentage variation in velocities and elastic constants show an interesting anomaly in all compositions. The observed anomalies in ultrasonic parameters at Tc in all compositions have been revealed in terms of existence of ferromagnetic (FM) state. Similarly, the anomalies at Tco show the transition from FM to charge-ordered antiferromagnetic (AFM) state. The observed results have been used to explore the competitions between FM and AFM. 相似文献
7.
8.
A. Aravindan P. Srinivasan N. Vijayan R. Gopalakrishnan P. Ramasamy 《Crystal Research and Technology》2007,42(11):1097-1103
Amino acid family crystals exhibit excellent nonlinear and electro‐optical properties. L‐alanine alaninium nitrate (LAAN) single crystal belonging to the amino acid group was grown by slow cooling solution growth technique. The High resolution X‐ray diffraction (HRXRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, UV‐Vis., Photoluminescence (PL) and Factor group analyses were carried out. The factor group analysis reveals 183 internal vibrations for the title compound. The second harmonic generation property was tested by Kurtz‐Perry powder technique. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
9.
A kinetic study has been carried out on the oxidation of N, N, N′, N′,-tetraethyl-p-phenylenediamine (TEPD) by metal ion like Ce4+, oxoanions viz., MnO4? and Cr2O72?; peroxides such as peroxomonosulphate (PMS), peroxodisulphate (PDS), and H2O2; and halogens namely Cl2, Br2, and I2. The fast kinetics of the formation and decay of the radical cation TEPD˙+ have been analyzed at 565 nm by the stopped-flow technique under pseudo-first-order conditions. From the kinetic data, it has been inferred that the reactions were found to be of first-order with respect to [TEPD] and [oxidant] but over all it has been of second-order. The observed second-order rate constants in both the formation and decay of TEPD˙+ has been correlated with the oxidation potentials of the various oxidants employed in this study. The effect of pH on the oxidation has been investigated in the formation and decay of TEPD˙+ as well as reduction studies have also been carried out using dithionite which has been found to regenerate the TEPD from the TEPD˙+ and the corresponding rate constant has also been determined. Besides these, this article also explains how the TEPD, which forms TEPD˙+ acts as a better electron relay than TMPD(N, N, N′, N′-tetramethyl-p-phenylenediamine) which forms TMPD˙+, even though both of them undergo one-electron oxidation and are used in the chemical routes to solar energy conversions. The observed rate constants for electron transfer were correlated theoretically using Marcus theory. The observed and calculated rate constants have good correlation. © 1995 John Wiley & Sons, Inc. 相似文献
10.
Lithium bis(oxalato)borate (LiBOB) salt-based nanocomposite gel polymer blend electrolyte (PVdF/PVC) membranes have been prepared
by solution casting technique for various concentrations of TiO2. The effect of anatase structure of nanosized titanium dioxide in the plasticized PVC/PVdF + LiBOB matrix has been observed
in the 2:1 salt filler ratio in the impedance measurements that the conductivity is increased one order of magnitude higher
than the filler-free electrolyte (1:0 salt:filler ratio). The phase morphology of this electrolyte membrane represents the
appearance of the free volume sites for ionic migration. 相似文献