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41.
D.C. conductivity of the ferroelectric BaHPO4 is measured and is found to lie between usual conductivities of semiconductor and insulator. Its temperature dependence shows intrinsic conduction in defective crystals due to H+ ions. The a.c. conductivity calculated from the measured dielectric constant follows σ˜ω1.54, a power law. Frequency of 20 kHz resolves the resistivity peak of a.c. conduction into two Gaussians. The ln sigma vs f plots at different temperatures show an exponential dependence and existence of a focal point. 相似文献
42.
Bijesh Sekaran Andrew Dawson Youngwoo Jang Kusum V. MohanSingh Prof. Dr. Rajneesh Misra Prof. Dr. Francis D'Souza 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(57):14335-14344
Using a combination of cycloaddition-retroelectrocyclization reaction, free-base and zinc porphyrins (H2P and ZnP) are decorated at their β-pyrrole positions with strong charge transfer complexes, viz., tetracyanobuta-1,3-diene (TCBD)-phenothiazine ( 3 and 4 ) or TCBD-aniline ( 7 and 8 ), novel class of push-pull systems. The physico-chemical properties of these compounds (MP-Donor and MP-TCBD-Donor) have been investigated using a range of electrochemical, spectroelectrochemical, DFT as well as steady-state and time-resolved spectroscopic techniques. Ground-state charge transfer interactions between the porphyrin and the electron-withdrawing TCBD directly attached to the porphyrin π-system extended the absorption features well into the near-infrared region. To visualize the photo-events, energy level diagrams with the help of free-energy calculations have been established. Switching the role of porphyrin from the initial electron acceptor to electron donor was possible to envision. Occurrence of photoinduced charge separation has been established by complementary transient absorption spectral studies followed by global and target data analyses. Better charge stabilization in H2P derived over ZnP derived conjugates, and in phenothiazine derived over aniline derived conjugates has been possible to establish. These findings highlight the importance of the nature of porphyrins and second electron donor in governing the ground and excited state charge transfer events in closely positioned donor-acceptor conjugates. 相似文献
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44.
A methodology is described for the synthesis of 2,6-disubstituted dihydro[2H]pyrans through a Lewis-acid catalyzed 6-endo-trig cyclization of β-hydroxy-γ,δ-unsaturated alcohols. Employing alkyl-substituted allylic diols and catalytic amounts of a Lewis acid, such as BF3·OEt2, the corresponding syn-pyrans are formed highly diastereoselectively and in good yields. The described process is simple to execute, proceeds readily at ambient temperature, and is scalable. 相似文献
45.
The concept of band tailing with focal point and width of the tail from IR absorption spectra of different organic conductors
is found valid even for thermal and elastic changes. The experimental situations like change of solvents, method of preparation,
applied pressure and pressure cycle apart from compositions is analyzed within the framework of tailing of states. Non-equilibrium
due to coupling between applied energy and free electrons can be responsible for the exponential relaxation from non-equilibrium
to equilibrium 相似文献
46.
Gupta Annika Durve Gupta Arvind Reyes-Calderón Almendra Merupo Victor Ishrayelu Kalita Golap Herrera-Celis Jośe Chandra Naresh Sharma Ashutosh Ramirez Jose Tapia Arriaga L. G. Oza Goldie 《Journal of fluorescence》2021,31(5):1445-1459
Journal of Fluorescence - Metal sulfide nanoparticles are semi-conductors that possess many applications in optics, optoelectronics and magnetic devices. There are physical and chemical methods for... 相似文献
47.
Creep and stress relaxation are known to be interrelated in linearly viscoelastic materials by an exact analytical expression. In this article, analytical interrelations are derived for nonlinearly viscoelastic materials which obey a single integral nonlinear superposition constitutive equation. The kernel is not assumed to be separable as a product of strain and time dependent parts. Superposition is fully taken into account within the single integral formulation used. Specific formulations based on power law time dependence and truncated expansions are developed. These are appropriate for weak stress and strain dependence. The interrelated constitutive formulation is applied to ligaments, in which stiffness increases with strain, stress relaxation proceeds faster than creep, and rate of creep is a function of stress and rate of relaxation is a function of strain. An interrelation was also constructed for a commercial die-cast aluminum alloy currently used in small engine applications. 相似文献
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Abstract The electrical resistivities of seven organic semiconductors and two nickel organometallics were found to have pressure dependencies which can be expressed as very simple analytic forms. These dependencies suggest that simple theoretical models for the resistivity should be possible. 相似文献
50.
A novel series of transition metal complexes have been synthesized from the reaction of 5-((3-(methylthio)-5-(pyridin-4-yl)-4H- 1,2,4-triazol-4-ylamino)melhyl)quinolm-8-ol with transition metal salts.The structures of these compounds have been elucidated by elemental and spectral analysis.Furthermore,compounds were screened for in vitro antimicrobial activity against the representative panel of two Gram-positive and two Gram-negative bacteria and two strains of fungus.The various compounds show potent inhibitory action against test organisms. 相似文献