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Abstract: Changes with Li extraction in the crystal structure and electronic structure of monoclinic LiMnO2 have been investigated by first-principle calculations using spin-polarized generalized gradient approximation method. It is found that the Li extraction has changed the oxidation state of Mn ion from 3+ to 4+ and thereby induced a phase transition from the monoclinic structure to rhombohedral symmetry, which opens channels for the migration of Mn ions from their own octahedral sites to the interlayer Li vacancies. It is the migration of Mn ions that responds for the phase transition to a spinel-like structure and the severe capacity loss during the electrochemical cycles of monoclinic LiMnO2. [Copyright &y& Elsevier]

Abstract: Based on one-electron-on-a-helix model and two-coupled-oscillator model, zero-frequency first hyperpolarizabilities of chiral molecules are investigated. Their expressions and the relations between them and microscopic parameters of chiral molecules are obtained by theoretical derivation. Furthermore, the relations of zero-frequency first hyperpolarizabilities with the wavelength of incident light and microscopic parameters of chiral molecules are simulated numerically. We find the fact that influences of microscopic parameters of chiral molecules on zero-frequency first hyperpolarizabilities are different by using different chiral molecular microscopic parameters such as the helix radius and the helix pitch for one-electron-on-a-helix model and α for two-coupled-oscillator model. Furthermore, the influence of microscopic molecular parameter to the zero-frequency first hyperpolarizabilities can also help to comprehend nonlinear optical mechanism of chiral molecules. [Copyright &y& Elsevier]

The key problem which needs to be solved during the commercialization process of the organic light emitting diode (OLED) lighting technology is how to improve the efficiency and stability of optoelectronic materials. In order to solute this issue, we explore the regulation of Ag nanoparticles (NPs) on the photoluminescence (PL) characteristics of an efficient organic optoelectronic polymer poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene-vinylene] (MEH-PPV). Because of the coupling between the localized surface plasmons from the Ag NPs and the PL emission of the MEH-PPV, the Ag NPs could effectively enhance the PL intensity, modulate the spectral line shape and shorten the lifetime of interchain species. The temperature-dependent PL measurement exhibits that with the introduction of Ag NPs, the thermal exchange process between the sample and the surrounding environment becomes more effective, and the activation energy decreases from 448 to 318 meV. The excitation intensity (EI)-dependent PL measurement demonstrates that the thermal accumulation effect and the nonlinearity of EI-dependent PL enhancement are both suppressed by the Ag NPs. The results of this study will provide experimental guidance to the design and fabrication of OLED devices with high efficiency and stability. [ABSTRACT FROM AUTHOR]

Through comparing the linear and nonlinear optical property of two pull-push chromophores, which are composed of difluoroboron β-diketonate functionalized with carbazole and tert-butyl carbazole, the role of tert-butyl in chromosphere has been discussed in detail. The tert-butyl unit would lead to the absorption and fluorescence peak red shift and accelerate the fluorescence relaxation rate of chromophores. Moreover, the tert-butyl unit would affect obviously the two-photon optical property of chromophore according to the Z-scan test. The transient absorption (TA) data shows that these two pull-push chromopphores both own intramolecular charge transfer (ICT) characteristics and the tert-butyl unit accelerate the dynamic rate of ICT generation and relaxation process, which may be responsible for the variance of fluorescence property. [ABSTRACT FROM AUTHOR]

Two push-pull compounds, which are comprised of triphenylamine (TPA) (electron donor units) and functionalized β-diketones difluorboron complexes (electron acceptor units) are probed by many spectroscopies, which offers the relationship between electron acceptor and the intrinsic excited state properties of push–pull chromophores. We found that the photoluminescence (PL) intensity would enhance with the number of electron acceptor. Transient absorption (TA) data shows that intramolecular charge transfer (ICT) process really exists in the two molecules after photoexcitation and this process would be prolonged through increasing the electron-acceptor, which would be responsible for the improvement of PL property. [ABSTRACT FROM AUTHOR]

Abstract: The properties of phonon-polaritons in one-dimensional undoped and ion-doped periodically poled superlattice lithium niobate (PPLN) crystals are studied theoretically. In this paper, we focus on the case that the electric field vector of the electromagnetic wave is parallel to the acoustic propagation vector. The phonon-polaritons are products of the coupling between electromagnetic and acoustic waves of mutually perpendicular propagations. Based on the theory of the phonon-polariton in PPLN, we investigate the phonon-polariton in ion-doped PPLN. The effects of the duty cycle and the impurities upon the properties of phonon-polaritons are discussed in detail. Some potential applications are also discussed. [Copyright &y& Elsevier]

Abstract: In this paper, the probe absorption spectra of a V-type atom embedded in photonic band gap (PBG) reservoir have been investigated under conditions that quantum interference among decay channels is important. The effect of the probe polarization on the absorption amplitude and spectral structure is investigated in detail. Comparing with similar models located in vacuum reservoir studied earlier, the study here shows that the probe polarization has some different effects on the absorption spectra in PBG reservoir. [Copyright &y& Elsevier]

We design the piezoelectric photonic crystal (PPC) with periodically reversed ferroelectric domains on the base of the structure of the piezoelectric superlattice, and study theoretically the transmission properties of electromagnetic (EM) waves in the PPC through Transfer Matrix Method of the photonic crystal (PhC). We analyze the mechanism for the influence of the piezoelectric effect on the transmission properties of EM waves in the PPC. The piezoelectric effect can influence the transmission properties of EM waves by changing the dielectric properties of the PPC. And we discuss the difference between the PPC and PhC. In the low frequency region, the reflection spectrum of PPC appear the total reflection and zero refractive indexes, and which doesn't exist in the PhC. In the high frequency region, the frequency positions and widths of the photonic band gaps of the PPC are higher and wider than cases of the PhC, respectively. Some potential applications are also discussed. • We have designed the piezoelectric photonic crystal with periodically reversed ferroelectric domains. • We have analyzed the mechanism for the influence of the piezoelectric effect on the electromagnetic waves. • We have studied theoretically the entire reflection spectrums of the piezoelectric photonic crystal. • We have also discussed which factors influence the photonic band gaps. • Some potential applications are discussed. [ABSTRACT FROM AUTHOR]

The properties of the multi-field coupling phonon-polaritons in magneto-electro-elastic metamaterials are studied theoretically on the base of the theory of the phonon-polaritons in the piezoelectric superlattices. The mechanism for multi−field coupling is analyzed. We discuss the factors that influence the properties of the multi−field coupling phonon-polaritons. We also study the negative magnetic permeability and negative refraction of the magneto-electro-elastic metamaterial. Some potential applications are also discussed. • The properties of the multi-field coupling phonon-polariton in magneto-electro-elastic metamaterials have been studied theoretically. •The mechanism for the multi-field coupling phonon-polariton coupling has been analyzed. •We have investigated the factors that influence the properties of the multi-field coupling phonon-polariton. •We have studied the negative magnetic permeability and negative refraction of magneto-electro-elastic metamaterials. [ABSTRACT FROM AUTHOR]