Poly(vinylidenefluoride) film (PVDF) doped with Eu(III)(NO<sub>3</sub>)<sub>3</sub>(<i>o</i>-Phenanthroline)<sub>2</sub> complex (complex <b>A</b>) was manufactured using an extrusion technique. Emission spectrum of the film was compared to spectra of the dopant and polyethylene based film. Stretching the film resulted in a sharp growth of intensity and reshaping of the luminescence spectrum. The impact of the PVDF matrix on the photoluminescence spectra of complex <b>A</b> is attributed to the Stark effect. Reasons for the increase of luminescence intensity are discussed. Quantum chemical calculations revealed a marked longwave shift of the lowest triplet and singlet energy levels of complex<b> A</b> compared to free phenanthroline. The amplification and frequency shifting of the luminescent spectrum of europium-complex-doped PVDF may lead to promising applications.
Different versions of <i>ab initio</i> quantum chemical models (cluster and periodic boundary conditions approximations) have been used to analyze the effect of finite length and the partial filling of the highest occupied orbital on the band-gaps of carbon nanotubes. In agreement with the previous calculations in the tight-binding approximation and pi-electron open shell model, it has been shown that the ground state of the nanotube with the zigzag structure is triplet. It has been confirmed that these tubes exhibit metallic or semiconductor properties with a very narrow half-filled conduction band. The band-gap is of order few tens of eV, and it is estimated that approximately 0.1-0.2% of pi-electrons belong to the conduction band of finite zigzag nanotubes. The triplet state is predicted to be the ground state of finite-length carbon nanotubes.
In the framework of the semi-empirical version of TDHF approach, the spectral parameters, linear and higher polarizabilities (in particular, for THG and EFISH) are calculated for free C<sub>60</sub> molecule and crystal, and for closed-shell anions (C<sub>60</sub>)<sup>-2</sup>,(C<sub>60</sub>)<sup>-4</sup>,(C<sub>60</sub>)<sup>-6</sup> in fullerides. It is demonstrated that the direct calculation of polarizability for the neutral molecule in crystals and similar calculation by means of the Lorentz factors gives the equivalent results while for HP the direct calculation includes higher field effects resulting in the approximately 5% increase of HP as compared to the Lorentz type calculation.
The first hyperpolarizability (HP) of ullerene on the silica substructure, modeled by β-quartz layers, is calculated in the framework of the semi-empirical version of the time-dependent Hartree-Fock theory. The induced by the substrate orthogonal to the surface component of β-vector invariant is of the same order as in the 'push-pull' organic molecules with the expressed nonlinear optical properties. Just this component is responsible for generation of the second harmonic according to Hoshi and coauthors.
Matrix formulation of TDHF theory of HP is given, (2i+1)-rule for dynamic HP and compatibility of TDHF with finite field approach are proven. The definition of tensor invariants of HP is given for the general case. The above results are illustrated by calculations of HP in organic molecules with expressed nonlinear optical properties. A method of inclusion of intermolecular Madelung potential into HP calculation in crystals and crystal layers is described and illustrated by estimation of its influence on HP of some Langmuir-Blodgett films. Similar technique is developed for calculation of Lorentz factors in crystals and crystal layers, which have been used for transformation of molecular HP into higher susceptibilities of crystals and films.