查看更多>>摘要：The pyrolytic decomposition of diazotetranoic acid (DA) to yield either methylene ketene (MK) and CO2 or carbon suboxide and formaldehyde, with liberation of nitrogen gas (N-2) in both cases, has been studied computationally using the composite CBS-QB3 method and accurate CCSD(T)/CBS level of theory. DA first undergoes a ring contraction reaction to form an intermediate (lactoketene) with the release of N-2. The lactoketene can then dissociate to form either MK and CO2 or carbon suboxide and formaldehyde. Thermodynamic and kinetic calculations indicate that the former reaction is spontaneous and occurs with low activation energy under normal temperature and pressure conditions.
查看更多>>摘要：In this study, we investigated the initial and subsequent decomposition mechanisms for MTNI(1-Methyl-2,4,5-trinitroimidazole) by DFT calculations. In the second stage of the nitro isomerization, a stable loose intermediate -ONO isomer is not generated but an unstable tight three-membered ring structure is generated, resulting in the direct production of NO. In the initial and subsequent process of H transfer, under certain conditions, a synergistic reaction occurs. The occurrence of the synergistic reaction is determined by the orientation of the -OH group on the hydroxymethyl group. Compared with the common decomposition mechanism, less energy is needed absorbed in above reaction.
查看更多>>摘要：In view of the potential applications via regulating excited state behaviors, in this work, excited state dynamics of 4-methoxy-3-hydroxyflavone (4M3HF) with different atomic electronegativities (i.e., 4M3HF-O, 4M3HF-S and 4M3HF-Se) are explored theoretically. Dominating chemical parameters, infrared (IR) spectra, and bond critical point (BCP) analyses reveal hydrogen bond could be enhanced in S-1 state. Via light-induced excitation, by comparing the energy gaps of frontier molecular orbitals (MOs) and charge recombination, we find low atomic electronegativity promotes ESIPT reaction. Insights into potential energy curves (PECs) and transition state (TS) forms, we present low atomic electronegativity facilitates ESIPT behavior for 4M3HF system.
查看更多>>摘要：We describe a lattice model to analyze the effect of protein surface charge distributions on protein solubility, aggregation, and condensation. Surface charges were modeled by considering a protein as a cubic particle with each face covered by two negative and positive patches (net zero charge). Particles were moved to adjacent lattice points according to a Monte Carlo algorithm. We observed that proteins having the same isoelectric point can have distinct aggregation propensities, depending on surface charge arrangements. Furthermore, with regard to the effect of heterogeneous intracellular environment, mixing two particle types affected the aggregation properties of the individual type.
查看更多>>摘要：We investigate the conformational dynamics of photoexcited poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) in toluene by femtosecond time-resolved near-infrared stimulated Raman spectroscopy. A vinylene C-H out-of-plane bend band at 945 cm(-1) decays partly with a time constant of 8.2 ps while the other bands do not exhibit the same decay component. The 945 cm(-1) band shows a high-frequency shift with a time constant of 11 ps, which reasonably agrees with its decay constant. The mode-specific decay and shift can be explained by torsional relaxation toward a less distorted structure, but not fully planar, around the vinylene groups.
查看更多>>摘要：Hydrothermal synthesis of cobalt oxide (CoO) nanostructures were grown on fluorine doped tin oxide (FTO) substrates for electrochemical NO detection. The NO sensing performance of the electrodes has been improved by depositing gold nanoparticles using photoreduction method. The electrochemical NO sensing was performed using amperometric i-t measurements. The optimized Au decorated CoO electrode demonstrated sensitivity 1.37 mM(-1) mu A cm(-2) with wide linear range 10 mu M 1.4 mM. The determination of dissolved NO in tap water and tube well water have been studied using such Au-CoO electrodes.
查看更多>>摘要：We consider the energy-dependent quantum dot with GaAs/GaAlAs Gaussian potential encompassment. Depending on the experimental or theoretical results for different types of interactions, the energy dependency can also be chosen as quadratic, fractional or any other type. The solutions of the wave equation for the energy dependent Gaussian quantum dot are performed numerically by employing the Runge-Kutta-Fehlberg method. The optical specifications of the structure are examined by using the compact-density-matrix formalism within iterative method. The total refractive index changes, the total absorption coefficients, the charge-currents and the induced magnetic fields are studied for different values of the energy dependency parameter.
查看更多>>摘要：WO3 nanorods as electrode material are synthesized using the hydrothermal method. X-ray Diffraction pattern confirmed the pure phase development of as-prepared material. Further, the shape and size of the particles of synthesized samples are explored by SEM, and FTIR spectra confirmed the functional groups and bonding vibrations associated with the synthesized sample. The electrochemical study was done using the three-electrode system in different aqueous electrolytes i.e. H2SO4, KNO3 and KOH. The maximum specific capacitance of 741 F/ g at 1 mA is achieved in the H2SO4 electrolyte. Trassati and Dunn methods were employed which revealed the contribution of capacitive and diffusion currents.
查看更多>>摘要：We have previously proposed a dielectric screened-exchange approach in which the dielectric constant is used to describe system-dependent features of the electronic structures of materials (Chem. Phys. Lett., 466, pp. 91-94, 2008). In the present paper, we discuss the theoretical effects of the nonlocal short-range exchange term on molecular excitations and compare them with the effects of the local Slater approximation. We show that the nonlocal short-range term is useful in describing precisely the (excited) electronic structures of molecules with large HOMO-LUMO gaps. Conversely, the local Slater approximation works effectively for systems with small HOMO-LUMO gaps.
查看更多>>摘要：In this paper, we present the geometric and electronic structure analyses of three Au-42(SR)(26) isomers based on a combination of grand unified model (GUM), ring model, superatom network model, and density functional theory calculations. Structural decompositions, Au-Au and Au-S distances, Wiberg bond orders, density of states, composition of the frontier orbitals, and origin of the optical absorption spectra are presented and discussed in detail. The structural decomposition of the Au cores of the three isomers into eight tetrahedral Au4 elementary blocks based on GUM shows that the isomeric mechanism of the three isomers can be ascribed to core and complex isomerism. Inspection of Au-Au and Au-S distances reveals the key role of the aurophilic interactions in the stability of the three Au-42(SR)(26) isomers. Furthermore, by analyzing the composition of the frontier orbitals, the origin of the optical absorption spectra of the three isomers is attributed to the sp. sp transition. Overall, the geometric and electronic structure analyses of the three Au-42(SR)(26) isomers illustrate the inherent structure-property correlations among these isomers.
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Elsevier