Synthesis of Diketopyrrolopyrrole Containing Copolymers: A Study of Their Optical and Photovoltaic Properties

The diketopyrrolopyrrole-based copolymers PDPP-BBT and TDPP-BBT were synthesized and used as donor for bulk heterojunction photovoltaic devices. The photophysical properties of these polymers showed absorption in the range 500-600 nm with a maximum peak around 563 nm, while TDPP-BBT showed broadband absorption in the range 620 - 800 nm with a peak around 656 nm. The power conversion efficiencies (PCE) of the polymer solar cells based on these copolymers and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) were 0.68% (as cast PDPP-BBT:PCBM), 1.51% (annealed PDPP-BBT:PCBM), 1.57% (as cast TDPPBBT: PCBM), and 2.78% (annealed TDPP-BBT:PCBM), under illumination of AM 1.5 (100 mW/cm2). The higher PCE for TDPP-BBT-based polymer solar cells has been attributed to the low band gap of this copolymer as compared to PDPP-BBT, which increases the numbers of photogenerated excitons and corresponding photocurrent of the device. These results indicate that PDPP-BBT and TDPP-BBT act as excellent electron donors for bulk heterojunction devices.

Preparation, characterization and electrical conductivity studies of MWCNT/ZnO nanoparticles hybrid

Multiwall carbon nanotubes (MWCNTs) were decorated with crystalline zinc oxide nanoparticles (ZnO NPs) by wet chemical route to form MWCNT/ZnO NPs hybrid. The hybrid sample was characterized by scanning and transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. Electrical conductivity of the hybrid can be tuned by varying the ZnO NPs content in the hybrid. In order to investigate the effect of nanoparticles loading on the conduction of MWCNTs network, electrical conductivity studies have been carried out in the wide temperature range 1.5-300K. The electrical conductivity of the hybrid below 100K is explained with the combination of variable range hopping conduction and thermal fluctuation induced tunnelling model. (C) 2009 Elsevier B.V. All rights reserved.

Studies on structural and electrical properties of sprayed SnO2 : Sb films

Thin films of antimony-doped tin oxide (SnO2:Sb) were prepared by spray pyrolysis using stannous chloride (SnCl2) and antimony trichloride (SbCl3) as precursors. The antimony doping was varied from 0 to 4 wt%. Scanning electron microscopy (SEM) revealed the surface morphology to be very smooth, yet grainy in nature. X-ray diffraction (XRD) shows films to have preferred orientation, which varies with the extent of antimony doping: undoped films prefer the (2 1 1) orientation, while the (3 0 1) orientation is preferred for doping levels of 0.5 and 1.0 wt%. For higher doping levels, the (2 0 0) orientation is preferred. This difference in preferred orientations is reflected in the SEM of the films. Atomic force microscopy (AFM) reveals that film roughness is not affected by antimony doping. The minimum sheet resistance (2.17 ohm/square) achieved in the present study is lower than values reported to date in SnO2:Sb films prepared from SnCl2 precursor. The Hall mobility of undoped SnO2 films was found to be 109.52 cm(2)/V s, which reduces to 2.55 cm(2)/ Vs for the films doped with 4 wt% of Sb. On the other hand, the carrier concentration, which is 1.23 x 10(19) cm(-3) in undoped films, increases to 2.89 x 10(21) cm(-3) for the films doped with 4 wt% of Sb. (c) 2004 Elsevier B.V. All rights reserved.

Charge distribution, dipole moments and infrared spectra of some thiol and thio acids

The dipole moments of thioglycollic (2.28 D), β-mereaptopropionic (2.25 D), thiomalic (2.47 D), malic (3.12 D), and dithiodiacetic (3.17 D) acids have been measured in dioxan at 35° C. Using the scheme of Smith, Ree, Magee and Eyring, the formal charge distribution in and hence the electric moments of these acids have been evaluated, compared with the theoretical moments, and discussed in terms of their various possible structures. Infrared spectra of these acids (liquid and nujol mull) indicate association through hydrogen bonding. These bonds are broken in solution. © 1969.

Charge distribution, dipole moments and infrared spectra of some thiol and thio acids

The dipole moments of thioglycollic (2.28 D), β-mereaptopropionic (2.25 D), thiomalic (2.47 D), malic (3.12 D), and dithiodiacetic (3.17 D) acids have been measured in dioxan at 35° C. Using the scheme of Smith, Ree, Magee and Eyring, the formal charge distribution in and hence the electric moments of these acids have been evaluated, compared with the theoretical moments, and discussed in terms of their various possible structures. Infrared spectra of these acids (liquid and nujol mull) indicate association through hydrogen bonding. These bonds are broken in solution.

Family of Mixed-Valence Oxovanadium(IV/V) Dinuclear Entities Incorporating N4O3-Coordinating Heptadentate Ligands: Synthesis, Structure, and EPR Spectra

Dinuclear ((VVV)-V-IV) oxophenoxovanadates of general formula [V2O3L] have been synthesized in excellent yields by reacting bis(acetylacetonato)oxovanadium(IV) with H3L in a 2:1 ratio in acetone under an N-2 atmosphere. Here L3- is the deprotonated form of 2,6-bis[{{(2-hydroxybenzyl)(N',N'-(dimethylamino)ethyl)}amino}methyl]-4-methylphenol (H3L1), 2,6-bis[{{(5-methyl-2-hydroxybenzyl)(N',N'-(dimethylamino)ethyl)}amino}methyl]-4-methylphenol (H3L2) 2,6-bis[ {{(5-tert-butyl-2-hydroxybenzyl)(N',N'-(dimethylamino)ethyl)}amino}methyl]-4-methylphenoI (H3L3), 2,6-bis[{{(5-chloro-2-hydroxybenzyl)(N',N'-(dimethylamino)ethyl)}amino}methyl]-4-methylphenol (H3L4) , 2,6-bis[{{(5-bromo-2-hydroxybenzyl)(N',N'-(dimethylamino)ethyl)}amino}methyl]-4-methylphenol (H3L5), or 2,6-bis[{{(5-methoxy-2-hydroxybenzyl)(N',N'-(dimethylamino)ethyl)}amino}methyl]-4-methylphenol (H3L6). In [V2O3L1], both the metal atoms have distorted octahedral geometry. The relative disposition of two terminal V=O groups in the complex is essentially cis. The O=V...V=O torsion angle is 24.6(2)degrees. The V-O-oxo-V and V-O-phenoxo-V angles are 117.5(4) and 93.4(3)degrees, respectively. The V...V bond distance is 3.173(5) Angstrom. X-ray crystallography, IR, UV-vis, and H-1 and V-51 NMR measurements show that the mixed-valence complexes contain two indistinguishable vanadium atoms (type 111). The thermal ellipsoids of O2, O4, C10, C14, and C15 also suggests a type III complex in the solid state. EPR spectra of solid complexes at 77 K display a single line indicating the localization of the odd electron (3d(xy)(1)). Valence localization at 77 K is also consistent with the V-51 hyperfine structure of the axial EPR spectra (3d(xy)(1) ground state) of the complexes in frozen (77 K) dichloromethane solution: S = 1/2, g(parallel to) similar to 1.94, g(perpendicular to) similar to 1.98, A(parallel to) similar to 166 x 10(-4) cm(-1), and A(perpendicular to) similar to 68 x 10(-4) cm(-1). In contrast isotropic room-temperature solution spectra of the family have 15 hyperfine lines (g(iso) similar to 1.974 and A(iso) similar to 50 x 10(-4) cm(-1)) revealing that the unpaired electron is delocalized between the metal centers. Crystal data for the [V2O3L1].CH2Cl2 complex are as follows: chemical formula, C32H43O6N4C12V2; crystal system, monoclinic; space group, C2/c; a = 18.461(4), b = 17.230(3), c = 13.700(3) Angstrom; beta = 117.88(3)degrees; Z = 8.

Infra-red and raman spectra of BaCl2.2H2O and BaCl2.2D2O

The infra-red and Raman spectra of ordinary and deuterated barium chloride dihydrate have been studied to throw light on the intramolecular hydrogen bonds in these two crystals. The frequencies of the stretching, bending and librational modes observed in infra-red and Raman spectra exclude the possibility of at least one of the OH.... Cl hydrogen bonds, contrary to the results of NMR and neutron diffraction studies.

On the conformation of cyclohexane-1,4-dione and its derivatives—I : Infrared and raman spectra of cyclohexane 1,4-dione and infrared spectrum of its octadeutero analogue

Raman spectra of cyclohexane 1,4-dione (I), in chloroform, benzene and water solutions have been recorded. Temperature effect on the spectrum has been studied. The IR spectra of I and its octadeutero analogue in the solid state have also been studied. The spectra have been found on the basis of selection rules applicable for Raman and IR spectra, to be consistent with a single conformer of C2 symmetry. Plausible causes of conformational preference have been discussed.

Dielectric relaxation and electrical conductivity in Bi5NbO10 oxygen ion conductors prepared by a modified sol–gel process

Crystalline Bi5NbO10 nanoparticles have been achieved through a modified sol–gel process using a mixture of ethylenediamine and ethanolamine as a solvent. The Bi5NbO10 nanoparticles were characterized by X-ray diffraction (XRD), differential scanning calorimetry/thermogravimetry (DSC/TG), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) and Raman spectroscopy. The results showed that well-dispersed 5–60 nm Bi5NbO10 nanoparticles were prepared through heat-treating the precursor at 650 °C and the high density pellets were obtained at temperatures lower than those commonly employed. The frequency and temperature dependence of the dielectric constant and the electrical conductivity of the Bi5NbO10 solid solutions were investigated in the 0.1 Hz to 1 MHz frequency range. Two distinct relaxation mechanisms were observed in the plots of dielectric loss and the imaginary part of impedance (Z″) versus frequency in the temperature range of 200–350 °C. The dielectric constant and the loss in the low frequency regime were electrode dependent. The ionic conductivity of Bi5NbO10 solid solutions at 700 °C is 2.86 Ω−1 m−1 which is in same order of magnitude for Y2O3-stabilized ZrO2 ceramics at same temperature. These results suggest that Bi5NbO10 is a promising material for an oxygen ion conductor.

Synthesis, magnetic and electrical properties of Fe-containing SiO2 nanocomposite

Nanocrystalline Fe powders were synthesized by transmetallation reaction and embedded in silica to form Fe-SiO2 nanocomposite. Thermomagnetic study of the as-prepared Fe sample indicates the presence of Fe3O4 and Fe particles. Oxidation studies of Fe and Fe-SiO2 show an increased thermal stability of Fe-SiO2 nanocomposite over pure Fe. The Fe-SiO2 shows an enhanced oxidation temperature (i.e., 780 K) and a maximum saturation magnetization value of (135 emu/g) with 64 wt.% of Fe content in silica. Electrical and dielectric behaviour of the Fe-SiO2 nanocomposite has been investigated as a function of temperature and frequency. Low frequency ac conductivity and dielectric constants were found to be influenced by desorptions of chemisorbed moisture. High saturation magnetization, thermal stability, frequency-dependent conductivity and low power loss make Fe-silica a promising material for high frequency applications. (C) 2010 Elsevier B.V. All rights reserved.

A comparative study of the magnetic and electrical properties of perovskite oxides and the corresponding two-dimensional oxides of K2NiF4

Electrical and magnetic properties of several oxide systems of K2NiF4 structure have been compared to those of the corresponding perovskites. Members of the La1−xSr1+xCoO4 system are all semiconductors with a high activation energy for conduction unlike La1−xSrxCoO3 (x ≥ 0.3) which is metallic; the latter oxides are ferromagnetic. La0.5Sr1.5CoO4 shows a magnetization of 0.5 μB at 0 K (compared to 1.5 μB of La0.5Sr0.5CoO3), but the high-temperature susceptibilities of the two systems are comparable. In SrO · (La0.5Sr0.5MnO3)n, both magnetization and electrical conductivity increase with the increase in n approaching the value of the perovskite La0.5Sr0.5MnO3. LaSrMn0.5Ni0.5(Co0.5)O4 shows no evidence of long-range ferromagnetic ordering unlike the perovskite LaMn0.5Ni0.5(Co0.5)O3; high-temperature susceptibility behavior of these two insulating systems is, however, similar. LaSr1−xBaxNiO4 exhibits high electrical resistivity with the resistivity increasing proportionately with the magnetic susceptibility (note that LaNiO3 is a Pauli-paramagnetic metal). High-temperature susceptibility of LaSrNiO4 and LaNiO3 are comparable. Susceptibility measurements show no evidence for long-range ordering in LaSrFe1−xNixO4 unlike in LaFe1−xNixO3 (x ≤ 0.35) and the electrical resistivity of the former is considerably higher. Electrical resistivity of Sr2RuO4 is more than an order of magnitude higher than that of SrRuO3. Some generalizations of the properties of two- and three-dimensional oxide systems have emerged from these experimental observations.

Sliding Modes for the Simulation of Mechanical and Electrical Systems Defined by Differential-Algebraic Equations

We offer a technique, motivated by feedback control and specifically sliding mode control, for the simulation of differential-algebraic equations (DAEs) that describe common engineering systems such as constrained multibody mechanical structures and electric networks. Our algorithm exploits the basic results from sliding mode control theory to establish a simulation environment that then requires only the most primitive of numerical solvers. We circumvent the most important requisite for the conventionalsimulation of DAEs: the calculation of a set of consistent initial conditions. Our algorithm, which relies on the enforcement and occurrence of sliding mode, will ensure that the algebraic equation is satisfied by the dynamic system even for inconsistent initial conditions and for all time thereafter. [DOI:10.1115/1.4001904]

Thermal and electrical switching studies on Ge20Se80-xBix (1 <= x <= 13) ternary chalcogenide glassy system

Alternating Differential Scanning Calorimetric (ADSC) and electrical switching studies have been undertaken on Ge20Se80-xBix glasses (1 <= x <= 13), to understand the effect of topological thresholds on thermal properties and electrical switching behavior. It is found that the compositional dependence of glass transition temperature (Tg), crystallization temperature (T-c1) and thermal stability (AT) of Ge20Se80-xBix glasses show anomalies at a composition x= 5, the rigidity percolation/stiffness threshold of the system. Further, unusual variations are also observed in different thermal properties, such as T-g, T-c1, Delta T, Delta C-p and Delta H-NR, at the composition x= 10, which indicates the occurrence of chemical threshold in these glasses at this composition. Electrical switching studies indicate that Ge20Se8o_RBig glasses with 5 11 exhibit threshold switching behavior and those with x = 12 and 13 show memory switching. A sharp decrease has been noticed in the switching voltages with bismuth concentration, which is due to the more metallic nature of bismuth and the presence of Bi+ ions. Further, a saturation is seen in the decrease in V-T around x = 6, which is related to bismuth phase percolation at higher concentrations of Bi. (C) 2010 Elsevier B.V. All rights reserved.