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81.
A new multiferroic system comprising of BaTiO3 (BT) and BaFe12O19 (BF) have been synthesized and investigated. The presence of both phases i.e., Piezoelectric/Ferroelectric and Piezomagnetic/Ferrimagnetic phases was confirmed by X-ray diffraction studies. With the decrease of Ferrite content, the ferroelectric polarization values have increased and hysteresis loops were recorded. The ferrimagnetic nature was dominant in all the ferrite compositions with a high coercivity of 3.5 kOe. Magnetoelectric hysteresis loops were recorded from the room temperature magnetoelectric (ME) measurements and the output has shown non-linearity indicating striction induced phenomena in BT–BF system. 相似文献
82.
Composite electrolytes are well-known multiphase systems and exhibit maxima in the conductivity at certain second-phase concentration.
An attempt has been made to investigate a number of sodium sulfate (Na2SO4)-based composite systems. The dispersoids that have been used are MgO, Al2O3, and SiO2. The samples have been characterized using impedance spectroscopy, X-ray diffraction, and differential scanning calorimetry.
The maximum conductivity has been observed for MgO dispersed system, and the percolation threshold has been observed at 30-mol%
dispersoid, MgO concentration. Interestingly, two maxima have been observed in case of the Na2SO4–SiO2 and Na2SO4–Al2O3 composite systems. In the Na2SO4–SiO2 system, the first maximum occurs at lower concentration, i.e., in the range between 10 and 20 mol%, whereas the second occurs
at the 40-mol% dispersoid concentration. For the Na2SO4–Al2O3 system, although slightly indistinguishable, two peaks in the conductivity vs composition plot have been observed around
12- and 30-mol% Al2O3 concentrations. 相似文献
83.
S. Kalyanasundaram A. Gopalan N. Muniyandi N. G. Renganathan Y. Saito H. Kataoka A. Manuel Stephan R. Nimma Elizabeth 《Ionics》2001,7(1-2):44-52
The lithium salt (x) (x=LiAsF6, LiPF6) was complexed with a blend of poly(vinyl chloride) (PVC) / poly(methyl methacrylate)(PMMA) and plasticized with a combination
of ethylene carbonate(EC) and propylene carbonate(PC). The electrolyte films were prepared using doctor blade method and subjected
to ionic conductivity measurements at nine different temperatures viz.,-30, -15, 0, 15, 30, 40, 50, 60 and 70 °C. The films
were also subjected to TG - DTA and FT-IR analysis. The effect of salt on ionic conductivity is discussed. A 75:25 PMMA/PVC
blend at 60 % plasticizer content has been found to possess optimal properties in terms of ionic conductivity, thermal and
electrochemical stability. 相似文献
84.
N. R. Subbaratnam S. P. Manickam P. Venuvanalingam A. Gopalan 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(1):117-128
The kinetics of cyclopolymerization of N,N' -methylenebisacrylamide (MBA) was carried out using peroxydisulfate ion as initiator. The rate of polymerization, Rp, was found to be proportional to [M] and [S2O8 2-]1/2 for the uncatalyzed system. A cyclopolymerization mechanism was found to fit the experimental results. The k21/kt 1/2 value for MBA polymerization was evaluated. Evidence in favor of the cyclopolymerization mechanism is provided. The addition of Ag ion enhances Rp. 相似文献
85.
N-Alkyl-N-benzyloxy carbamates, 2, undergo facile intramolecular cyclization with a variety of carbon nucleophiles to give functionalized five- and six-membered protected cyclic hydroxamic acids, 3, in good to excellent yields. This method can be extended to prepare seven-membered cyclic hydroxamic acids in moderate yields. The sulfone intermediates 3 from this study can be alkylated while the corresponding phosphonates have been shown to undergo HWE reaction. The α,β-unsaturated synthon, 8, prepared by thermal elimination of sulfoxide 3m, undergoes Michael addition with secondary amines. The usefulness of this approach to prepare polydentate chelators has been demonstrated by the synthesis of bis cyclic hydroxamic acids 12, 14, and 15. 相似文献
86.
Madhavan?Jaccob Gopalan?RajaramanEmail author Federico?TottiEmail author 《Theoretical chemistry accounts》2012,131(3):1150
Abounding potential technological applications is one of the many reasons why adsorption of aliphatic thiols on gold surface
is a subject of intense research by many research groups. Understanding and exploring the nature of adsorbed species, the
site of adsorption and the nature of interaction between adsorbed species and the gold surface using experimental and theoretical
investigations is an active area of pursuit. However, despite a large number of investigations to understand the atomistic
structures of thiols on Au(111), some of the basic issues are still unaddressed. For instance, there is still no clear information
about the mechanism of adsorption of alkylthiol on gold surface. Furthermore, the reactivity and mechanism of adsorption of
alkylthiol is likely to differ when gold adatoms and/or vacancies in the gold layers are considered. In this work, we have
tackled these issues by computing the stationary states involved in the thiols adsorption in order to shed light on the kinetics
aspects of adsorption process. In this respect, we have considered a variety of thiols into consideration such as methylthiol,
dimethylsulfide, dimethyldisulfide, thioacetates, and thiocyanates. We have also considered the cleavage mechanism in the
clean and the reconstructed surface scenario and the structure, energetics and spin densities have been computed using electronic
structure calculations. For all the studied cases, an homolytic cleavage of CH3S–X (X = H, CH3, SCH3, CN, and COCH3) bond has been found to occur upon adsorption on the gold surface. 相似文献
87.
Hydroxo‐Bridged Dimers of Oxo‐Centered Ruthenium(III) Triangle: Synthesis and Spectroscopic and Theoretical Investigations 下载免费PDF全文
Apoorva Upadhyay Jitendrasingh Rajpurohit Mukesh Kumar Singh Richa Dubey Anant Kumar Srivastava Prof. Dr. Ashutosh Kumar Prof. Dr. Gopalan Rajaraman Prof. Dr. Maheswaran Shanmugam 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(20):6061-6070
The homometallic hexameric ruthenium cluster of the formula [RuIII6(μ3‐O)2(μ‐OH)2((CH3)3CCO2)12(py)2] ( 1 ) (py=pyridine) is solved by single‐crystal X‐ray diffraction. Magnetic susceptibility measurements performed on 1 suggest that the antiferromagnetic interaction between the RuIII centers is dominant, and this is supported by theoretical studies. Theoretical calculations based on density functional methods yield eight different exchange interaction values for 1 : J1=?737.6, J2=+63.4, J3=?187.6, J4=+124.4, J5=?376.4, J6=?601.2, J7=?657.0, and J8=?800.6 cm?1. Among all the computed J values, six are found to be antiferromagnetic. Four exchange values (J1, J6, J7 and J8) are computed to be extremely strong, with J8, mediated through one μ‐hydroxo and a carboxylate bridge, being by far the largest exchange obtained for any transition‐metal cluster. The origin of these strong interactions is the orientation of the magnetic orbitals in the RuIII centers, and the computed J values are rationalized by using molecular orbital and natural bond order analysis. Detailed NMR studies (1H, 13C, HSQC, NOESY, and TOCSY) of 1 (in CDCl3) confirm the existence of the solid‐state structure in solution. The observation of sharp NMR peaks and spin‐lattice time relaxation (T1 relaxation) experiments support the existence of strong intramolecular antiferromagnetic exchange interactions between the metal centers. A broad absorption peak around 600–1000 nm in the visible to near‐IR region is a characteristic signature of an intracluster charge‐transfer transition. Cyclic voltammetry experiments show that there are three reversible one‐electron redox couples at ?0.865, +0.186, and +1.159 V with respect to the Ag/AgCl reference electrode, which corresponds to two metal‐based one‐electron oxidations and one reduction process. 相似文献
88.
Jason F. Khoury Jiangang He Jonathan E. Pfluger Ido Hadar Mahalingam Balasubramanian Constantinos C. Stoumpos Rui Zu Venkatraman Gopalan Chris Wolverton Mercouri G. Kanatzidis 《Chemical science》2020,11(3):870
Subchalcogenides are uncommon, and their chemical bonding results from an interplay between metal–metal and metal–chalcogenide interactions. Herein, we present Ir6In32S21, a novel semiconducting subchalcogenide compound that crystallizes in a new structure type in the polar P31m space group, with unit cell parameters a = 13.9378(12) Å, c = 8.2316(8) Å, α = β = 90°, γ = 120°. The compound has a large band gap of 1.48(2) eV, and photoemission and Kelvin probe measurements corroborate this semiconducting behavior with a valence band maximum (VBM) of −4.95(5) eV, conduction band minimum of −3.47(5) eV, and a photoresponse shift of the Fermi level by ∼0.2 eV in the presence of white light. X-ray absorption spectroscopy shows absorption edges for In and Ir do not indicate clear oxidation states, suggesting that the numerous coordination environments of Ir6In32S21 make such assignments ambiguous. Electronic structure calculations confirm the semiconducting character with a nearly direct band gap, and electron localization function (ELF) analysis suggests that the origin of the gap is the result of electron transfer from the In atoms to the S 3p and Ir 5d orbitals. DFT calculations indicate that the average hole effective masses near the VBM (1.19me) are substantially smaller than the average electron masses near the CBM (2.51me), an unusual feature for most semiconductors. The crystal and electronic structure of Ir6In32S21, along with spectroscopic data, suggest that it is neither a true intermetallic nor a classical semiconductor, but somewhere in between those two extremes.Subchalcogenides are uncommon, and their chemical bonding results from an interplay between metal–metal and metal–chalcogenide interactions. 相似文献
89.
Dhanusuraman Ragupathy Anantha Iyengar Gopalan Kwang-Pill Lee 《Electrochemistry communications》2009,11(2):397-401
We report an ingenious approach for the fabrication of a promising glucose sensor, GOx/Au/CS–IL–MWNT(SH), that exploits the synergistic beneficial characteristics of multiwalled-carbon nanotubes (MWNTs), gold nanoparticles (AuNPs), chitosan (CS) and room temperature ionic liquid (RTIL). Direct electron transfer between glucose oxidase (GOx) and electrode was achieved. Scanning electron microscopy and atomic force microscopy images of GOx/Au/CS–IL–MWNT(SH) reveal that MWNTs and AuNPs are dispersed in CS–IL matrix. Cyclic voltammetry, impedance spectroscopy and chronoamperometry were used to evaluate the performance of biosensor. The GOx/Au/CS–IL–MWNT(SH) biosensor exhibits a linear current response to glucose concentration (1–10 mM) at a low potential of 0.10 V and precludes interferences from uric acid and ascorbic acid. The GOx/Au/CS–IL–MWNT(SH) biosensor has superior performances over GOx/CS–IL–MWNT(SH). 相似文献
90.
Tolis EI Engelhardt LP Mason PV Rajaraman G Kindo K Luban M Matsuo A Nojiri H Raftery J Schröder C Timco GA Tuna F Wernsdorfer W Winpenny RE 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(35):8961-8968
The synthesis and structural characterization of a nonanuclear FeIII cage complex is reported. The nine iron centers in [Fe9(mu3-O)4(O3PPh)3(O2CCMe3)13] lie on the vertices of an incomplete icosahedron, with the P atoms of triphenylphosphonate at the other three vertices. The paramagnetic core therefore describes a tridiminished icosahedron. Magnetic studies suggest an S=1/2 ground state for the molecule. Analysis of exchange paths and the susceptibility data point to the interpretation that the cluster can be divided into two nearly decoupled sections: an {Fe6O3} section, with an S=0 ground state, in which three oxo-centered triangles bound a central triangle that is not oxo-centered; and an {Fe3O} triangle with S=1/2. The analysis of the susceptibility data leads to a Heisenberg model based on three significant antiferromagnetic exchange interactions, with values of 173.7 cm-1 in the {Fe3O} triangle, and 30.9 and 19.1 cm-1 within the {Fe6O3} section, while the exchange between them is <1 cm-1. With these assignments, the theoretical low-temperature differential susceptibility is also in very good agreement with measurements up to 50 T. Magnetic measurements in the milli-kelvin range reveal striking hysteresis loops and magnetization reversals associated with a Landau-Zener-Stückelberg (LZS) transition as enhanced by the occurrence of a phonon bottleneck. 相似文献