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In this study, a terpyridyl derivative 2-(6-(pyridin-2-yl)-4-(4-((E)-2-(pyridin-4-yl)-vinyl)phenyl)pyridin-2-yl)pyridine (abbreviated as PYTPY) has been designed and prepared with an A–π–A architecture (A = electron acceptor), whose spontaneous aggregation style can be triggered by different external conditions. Mathematical modelling through time dependent density functional theory (TD-DFT) provides a quantitative understanding of the equilibrium molecular geometries at the aggregated state between adjacent PYTPY molecules with addition of different additives, such as water, H+, and Ag+ ions. The vertical electronic excitations and the related UV-vis absorbing character of PYTPY under different conditions were also forecasted, which was verified by the examined absorption spectra. Our method of calculating intermolecular interactions between adjacent molecules and predicting spontaneous aggregation style and absorption performance under an external environment is generally applicable to design and create other functional organic materials. [ABSTRACT FROM AUTHOR]

Raman spectra and ultraviolet-visible absorption spectra of four different geographic origins of Radix Astragali were collected. These data were analyzed using kernel principal component analysis combined with sparse representation classification. The results showed that the recognition rate reached 70.44% using Raman spectra for data input and 90.34% using ultraviolet-visible absorption spectra for data input. A new fusion method based on Raman combined with ultraviolet-visible data was investigated and the recognition rate was increased to 96.43%. The experimental results suggested that the proposed data fusion method effectively improved the utilization rate of the original data. [ABSTRACT FROM AUTHOR]

Abstract: Titania nanoparticles were obtained by an ultrasonic assistant sol–gel method. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and thermal analysis. The optical absorption of the samples has been measured by photoacoustic (PA) spectroscopy, which is powerful for detecting small amount of strongly scattering materials. The structural variations of the sample during the phase transitions were firstly studied using Nd3+ as an absorption spectral probe. The PA results show that the TiO2 gel heated at 50°C is basically amorphous and still contains abundant trapped water and ethanol, which makes the environment around Nd3+ similar with that of its aqueous ion. For the sample calcined at higher temperature, the f–f transitions of Nd3+ exhibit a continuous red shift along with the gel-to-anatase transformation, indicating an increase of the “degree of covalency” for Nd3+ bonding. For the sample calcined at 1100°C, however, the f–f transitions of Nd3+ show blue shifts and the hypersensitive transition intensities of Nd3+ decrease, indicating an increase of ionicity for Nd3+ bonding. This can be attributed to the segregation of Nd3+ ions to the external surface, forming Nd4Ti9O24 during the anatase-to-rutile transition. [Copyright &y& Elsevier]

BiOI is reported to be a promising photocatalytic material for splitting water and decomposing pollutants in the visible range. However, previous investigations focus mainly on its photocatalytic property and other properties are not well studied. Here we put our effort to study the electronic, elastic and vibrational properties of BiOI. The results indicate that BiOI is an indirect narrow band gap semiconductor. Bi–O bonds have both covalent and ionic characteristics while Bi–I bonds may have more ionic nature. BiOI is mechanically and dynamically stable. However, calculated directional bulk and Young's moduli reveal that it is seriously mechanically anisotropic, originating from its layered structure. Its infrared absorption spectrum is simulated and four peaks are found. The origins of these peaks are explored based on the calculated Born effective charges and vibrational eigenvectors at the Brillouin zone center. In addition, the dielectric constants of BiOI are computed and discussed. We hope our study will enrich the knowledge of BiOI and other similar materials. • Bonding property within BiOI is studied by comprehensive methods. • Elastic properties of BiOI are investigated and detailedly analyzed. • Infrared absorption spectrum of BiOI is simulated and its origin is explored. [ABSTRACT FROM AUTHOR]

LiZnPS 4 is thought to be a promising mid-infrared optical crystal and lithium battery material, but its fundamental properties are still not well investigated. In this work, we performed a systematic study on its electronic, elastic, infrared and electrical properties. The results indicate that LiZnPS 4 is an indirect band gap crystal. Calculated partial density of states reveals that the top of its valence band is formed by the S 3p orbital while the component of the bottom of the conduction band is complex. The Zn 4p orbital is not empty in LiZnPS 4 owing to the tetrahedral coordination of the Zn atoms. Calculated elastic properties indicate that LiZnPS 4 is a mechanically stable crystal with elastic anisotropy. It has a relatively low Debye temperature of 294.8 K. Its infrared absorption spectrum was simulated and the origins of the strong peaks in it were revealed. Vibrational modes at the Brillouin zone center were illustrated and Born effective charges were calculated and discussed. Computed dielectric constants uncover that electrons contribute more to the total dielectric constants than ions. Studies imply that LiZnPS 4 –Li+ battery has a high theoretical voltage, a low electric capacity and a slightly high activation barrier. • Zn 4p orbital is found to be partly occupied for the special bonding pattern. • Infrared absorption spectrum is simulated and the related properties are studied. • Electrical properties of LiZnPS 4 are studied for possible use in lithium battery. [ABSTRACT FROM AUTHOR]

In 2 Se 3 is an important compound having a complex phase diagram. In this work, we found a non-layered phase of In 2 Se 3 with the help of the particle swarm optimization method. Studies indicate that this phase is dynamically stable. It is an indirect band gap semiconductor with a gap of 2.36 eV. Calculated elastic constants imply that it is mechanically stable with elastic anisotropy. It has a low bulk modulus and Debye temperature despite of its non-layered structure. There are five strong peaks in the simulated infrared absorption spectrum and the corresponding vibrational modes are presented. Born effective charges and dielectric constants are obtained and discussed. The computed birefringence indicates that it might be a potential nonlinear optical crystal. • A non-layered In 2 Se 3 with dynamical and mechanical stability is predicted. • It is an indirect band gap semiconductor formed by Se-linked tetrahedrons. • Computed birefringence indicates its possible use as nonlinear optical crystal. [ABSTRACT FROM AUTHOR]