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We report a general and simple approach to take control of the color of light-emitting two-luminophore hybrid nanowires (NWs). Our strategy is based on the spatial control at the nanoscale (coaxial geometry) and the spectral selection of the two kinds of luminophores in order to restrict complex charge and energy transfers. Thus, it is possible to control the color of the photoluminescence (PL) as an interpolation of the CIE (Commission Internationale de l’Eclairage) coordinates of each luminophore. For this purpose, we selected a green-emitting semiconducting polymer and a red-emitting hexanuclear metal cluster compound, (n-Bu4N)2Mo6Br8F6, dispersed in a poly(methyl-methacrylate) (PMMA) matrix. The great potential and the versatility of this strategy have been demonstrated for two configurations. First, a yellow PL with a continuous change along the nanowire has been evidenced when the proportion of the PPV shell versusthe nanocomposite core, that is, the green/red volumic ratio, progressively shifts from 1:2 to 1:5. Second, an extremely abrupt change in the PL color with red-green-yellow segments has been achieved. A simple model corroborates the effectiveness of this strategy. PL excitation and time-resolved experiments also confirm that no significant charge and energy transfers are involved. The two-luminophore hybrid nanowires may find widespread nanophotonic applications in multicolor emitting sources, lasers and chemical and biological sensors.

The vibrational properties of β-SnWO4at center of the Brillouin zone are investigated by Raman at low temperature and infrared spectroscopies in connexion with ab initio calculations. In this cubic structure archetype of new materials with ionic conductivity properties, all 29 optical modes predicted by group theory are Raman-active. All lines have been unambiguously identified on the basis of depolarization ratio measurements. The phonon spectrum is calculated at the center of the Brillouin zone by GGA pseudopotentials within the PWSCF/QE suite. A remarkable agreement is obtained with the experimental frequencies, and a fairly good one is also observed with the Raman scattering cross sections calculated using LDA pseudopotentials for the internal modes of WO42–tetrahedra and the lattice modes as well. All Raman lines are assigned for the first time, and the normal coordinates characteristics are described. The whole results give a large credit to the calculation of the phonon spectra in this structural arrangement with such ions. The phonon density of states is deduced, and the characteristics are explained on the basis of the phonon dispersions curves along the [ξ00] and [ξξ0] high-symmetry directions of the Brillouin zone.

In NH 4 AlF 4 the NH 4 + molecules form a layered structure where the interlayer distance, 6.367 Å, is about twice as large as the intralayer nearest neighbours distance, 3.597 Å. There is an orientational order-disorder transition at T c = 156.9 - 0.1 K, explained by the Ising model, with first and second neighbours and a weak interlayer coupling. Monte Carlo simulations are presented based on this model.

Chemical preparation, single-crystal X-ray structure, and infrared and polarized Raman spectra of a new cadmium dibarium bis(monohydrogen monophosphate) bis(dihydrogen monophosphate) are presented. The atomic arrangement consists of anionic layers formed by HPO2−4and H2PO−4groups connected to each other through strong hydrogen bonds, resulting in a two-dimensional network. These sheets are held together by six oxygen-coordinated Cd2+and nine oxygen-coordinated Ba2+ions to build a three-dimensional framework. An assignment of lattice and internal vibrations in terms of symmetry species and approximate type of motion is given. A comparison with the vibrational fundamentals of the PO3−4ion in the isostructural CaBa2(HPO4)2(H2PO4)2(CaBa2) is also discussed. Band positions are found to be largely independent of the positive ion. Crystal data for CdBa2(HPO4)2(H2PO4)2(CdBa2): M=773.08 g mol−1, monoclinic, space group P21/c(No. 14), a=5.434(4) Å, b=10.140(2) Å, c=12.298(2) Å, β=100.43(3)°, Z=2, R1/wR2=0.024/0.066 [1858 observed reflections with I>6σ(I)].

The crystal structure of a new apatite Ca6Sm2Na2(PO4)6F2has been determined using 842 independent reflections (R=0.059, Rw=0.076). The unit cell constants are a=9.3895(3) Å, c=6.8950(4) Å with P63/mspace group. The structure contains disordered cations in both the Ca(1) and the Ca(2) sites. The formula assigned to the compound is [Ca1.57Sm0.43Na2](1) [Ca4.43Sm1.57](2)(PO4)6F2. The Raman spectra have been studied and they are consistent with the proposed structure. A comparison with fluorapatite shows that most of the Raman lines of the new compound are significantly broad, which is attributed to the random distribution of three kinds of atoms on the cation sites.

The cubic to tetragonal phase transition occurring at 198K in the fluoro-perovskite RbCaF3 has been studied by the 87Rb nuclei magnetic resonance.In the tetragonal phase, the CaF6 octahedra tilt angle Φ, which is the order-parameter, has been deduced from the quadrupolar coupling constant. Its temperature dependence is described by a power-law with a cross-over from a Landau-type exponent to an exponent β = 0,32 at 150 K.In the cubic phase, the intensity of the Larmor frequency signal deviates from a Curie law twenty degrees above Tc; this can be attributed to the existence of tetragonal domains.

The heat capacity of NH4AIF4 has been measured from 5 K to 330 K. An anomalous peak at 156.9 K and a broad shoulder above 100 K are discussed in relation with the NH4+-NH4+ direct and indirect interactions and the librations of the ammonium ions within an electrostatic point charge model.

The Raman spectra of RbAIF4 (phase II) and KAIF4 (Phase II and IV) at room temperature were measured under hydrostatic pressure up to 10 GPa and 4 GPa, respectively. While the frequencies of the former do not exhibit any significant singularity against temperature, in the case of KAIF4 a strong frequency jump is observed at 0.21 GPa. This is attributed to the martensitic phase transition already observed as a function of temperature. The pressure dependence of the frequencies in the two compounds is discussed in relation to their structure and the structural phase transitions.

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