Optical,structural and electrochromic studies of molybdenum oxide thin films with nanorod structure

The MoO₃ thin films were prepared via sol–gel dip coating method on glass and FTO glass substrate. The optical and other properties of multilayered MoO₃ films with 2–10 layers were investigated. The MoO₃ films were studied using UV–Visible transmission, XRD, SEM, FTIR and Cyclic Voltammetry (CV) measurements. The band gap value for MoO₃ films was evaluated and in the range of 3.2 eV–3.72 eV. The XRD spectrum reveals that the crystallinity increases along the (020) and (040) planes with the increase in thickness. The SEM images showed the formation of nanorods upto six layers. The FTIR spectrum confirms the formation of MoO₃. The 6 layered films show the maximum anodic (spike)/cathodic (peak) diffusion coefficient of 18.84/1.701 × 10^?11 cm²/s. The same film exhibits the change in optical transmission of 49% with the bleached/coloured state transmission of 62/13%.     

An atomistic assessment of the impact of flaw orientation on the elastic and failure behavior of single-crystal Si nanometre-thick slabs

Abstract

Failure of nanoscale Si thin films was examined using molecular dynamics (MD) simulations that employed the modified embedded atom method (MEAM) interatomic potential. Specifically, nanometre-thick slabs of different crystallographic orientations containing asymmetric, high aspect ratio surface flaws were subjected to uniaxial tensile strains with the strain applied perpendicular to the flaw major axis. The ensuing elastic response and failure behaviour were examined as a function of variation in crystallographic orientation relative to the surface flaw. For certain flaw orientations, crack propagation was accompanied by slip along preferred directions, while in other cases, failure was purely brittle. In addition, a significant dependence of the computed elastic constants and yield stress, on the relative orientation of the surface flaw was observed. This work offers new insights into the role of surface flaws on the mechanical failure of silicon-based, nanoscale, engineered structures.     

Studies of a molecular hourglass: synthesis and magnetic characterisation of a cyclic dodecanuclear {Cr10Cu2} complex

The synthesis, structure, EPR, and magnetic studies of two dodecanuclear heterometallic cyclic clusters are reported. The compounds have the general formula [R(2)NH(2)](2)[Cr(10)Cu(2)F(14)(O(2)CCMe(3))(22)] (R=Me, 1 or iPr, 2). Both structures contain an array of metal centers which describe an approximate "hourglass", with an ammonium cation in the center of each half of the figure. The chromium sites are all six-coordinate, with the two copper sites five-coordinate. The majority of metal-metal edges are bridged by a single fluoride and two pivalate ligands, while two Cr--Cu edges are bridged by a single fluoride and a single pivalate. Magnetic studies show that 1 and 2 exhibit similar (but not identical) behavior, which can be attributed to ten antiferromagnetic and two ferromagnetic exchange interactions around the ring which gives an S=0 ground state. Quantum Monte Carlo calculations have been used to quantify the exchange interactions by successfully simulating the susceptibility for the full temperature range and thus clarifying the distinction between 1 and 2. EPR spectroscopy shows signals due to excited states, and a variable-temperature study has provided an estimate of the energy gap between the first excited state (S=1) and second excited state (S=2) for 1 that is consistent with the value obtained using the QMC method.     

Luminescence studies on gamma irradiated KCl: Ce crystals

This paper reports thermoluminescence(TL), optical absorption and TL emission studies that are made on Ce³⁺ doped KCl single crystals irradiated at room temperature. The glow curve and optical absorption studies indicate the participation of Ce³⁺ ions in the TL process. The TL study suggests the presence of low concentration of Ce³⁺ ions which reduces the TL efficiency with respect to pure KCl samples. On F bleaching γ irradiated crystals Z₁ centers are observed. A broader and strongly intense violet blue emission at 290, 370, 423 and 488 nm has been observed with 240 nm excitation. This emission has been attributed due to the transition from 5d(2D) excited energy level to the 4f¹ ground stable energy level (2F_5/2 and 3F_7/2) of Ce³⁺ doped KCl crystals.     

Structure of the Nematic Phase of Pbaba

X-ray diffraction investigations of the nematic phase (191°C - 276°C) of p-n-propyloxybenzylidene-p-amino benzoic acid have shown that this phase is a skewed cybotactic nematic phase. The diffraction patterns, obtained with aligned samples, reveal an additional surprising structural feature, - the presence of one dimensional molecular correlation in a direction parallel to the nematic director. At 192°C, it is found that the molecular unit, thus correlated, is about 37 Å in length (dimer length) and the correlation range extends up to about seven such units. This l-d correlation persists up to the N-I transition.     

Creatinine complexes of zinc,cadmium and mercury

Zinc, cadmium and mercury(II) complexes of creatinine of the composition M(Creat)₂X₂ (X = Cl, Br or I) are prepared. The complexes are characterized by analytical and spectral methods. The increase in cyclic NH stretching frequency in the case of complexes (3350 cm^?1) from that of the free ligand (3300 cm^?1) suggested that secondary nitrogen is involved in coordination. The shift in the resonances of cyclic NH proton in the ¹H NMR and carbonyl and imine carbons in ¹³C NMR when compared to the ligand indicated that cyclic nitrogen coordinates. Conductivity measurements in N, N-dimethylformamide suggested that the complexes are non-electrolytes. Thermal decomposition behaviour of the complexes is also discussed.     

XPS studies of the valence electron levels of metalloporphyrins

We have studied the valence electron spectra of several tetraphenylmetalloporphyrins by XPS. The most striking features of the spectra are those derived from the metal d levels. These reveal that the metal and porphine levels are nearly uncoupled in the copper and zinc porphyrins but that the two kinds of levels interact more extensively in the cobalt compound.     

Electrochemical behaviour of Cu-NTA complexes

The deposition of copper was found to involve adsorbed monovalent copper which follows nonactivated Temkin isotherm. The presence of nitrilotriacetic acid stabilises it and the second electron transfer is slow.     

An insight into the self-discharge of Fe3O4 electrodes in alkali solutions

Iron oxide development is necessary as the Iron electrodes exhibit high self discharge and poor charging efficiency in alkaline batteries. Pressed electrodes containing electrolytic iron powder with varying amounts of Fe₃O₄ have been used. The variation of open circuit potential and self discharge currents with alkali concentration is followed. For better understanding of these variations, cyclic polarisation (−1.3 V to + 0.4 Vvs Hg/HgO) and hydrogen evolution studies are carried out. Beyond −0.5 Vvs Hg/HgO, the surface is covered by hydrolysed layer and the protons diffuse away from this layer. The hydrogen evolution takes place with the discharge of K⁺ ions as the rate determining step.     

Base catalyzed acylative decarboxylation. Part III. Acylation of homophthalic acid

Homophthalic acid (I) reacts with acetic anhydride in the presence of base to form the expected product, o-carboxyphenylacetone (III). Besides III, three other new products were formed, namely, 3-methyl-4-carboxyisocoumarin (II), 4-acetyl-3-methylisocoumarin (IV) and 8-acetyl-7-methylnaphtho[1,2-c]isocoumarin. A mechanism for the formation of these compounds is presented. The presence of 3-methyl-4-carboxyisocoumarin (II) supports an earlier suggestion (1) that acylation can occur prior to and without decarboxylation, which has been a point of concern in this reaction.