Synthesis, Characterization, and Modeling of Naphthyl-Terminated sp Carbon Chains: Dinaphthylpolyynes

We report a combined study on the synthesis, spectroscopic characterization and theoretical modelling of a series of {\alpha},{\omega}-dinaphthylpolyynes. We synthesized this family of naphtyl-terminated sp carbon chains by reacting diiodoacetylene and 1-ethynylnaphthalene under the Cadiot-Chodkiewicz reaction conditions. By means of liquid chromatography (HPLC), we separated the products and recorded their electronic absorption spectra, which enabled us to identify the complete series of dinaphthylpolyynes Ar-C2n-Ar (with Ar = naphthyl group and n = number of acetilenic units) with n ranging from 2 to 6. The longest wavelength transition (LWT) in the electronic spectra of the dinaphthylpolyynes red shifts linearly with n away from the LWT of the bare termination. This result is also supported by DFT-LDA simulations. Finally, we probed the stability of the dinaphthylpolyynes in a solid-state precipitate by Fourier-transform infrared spectroscopy and by differential scanning calorimetry (DSC).Comment: This document is the unedited Author's version of a Submitted Work that was subsequently accepted for publication in [J. Phys. Chem. B], copyright \c{opyright} American Chemical Society after peer review. To access the final edited and published work see http://pubs.acs.org/doi/abs/10.1021%2Fjp104863

Effect of high oxygen deficiency in nano-confined bismuth sesquioxide

Bismuth sesquioxidein its cubic form, i.e.delta-Bi2O3,is the fastest oxygen ionic conductor knownwith important applications in energy technologies.However, the material is unstable asit undergoes to high-density polymorphic transitionsand degradation. In this work, we show that delta-Bi2O3can be stabilized both at high and low temperatures (T < 775°C) under low oxygen partial pressure (pO2< 10-5atm), where the material is nanostructured in multi-layered thin film coherent heterostructures with yttriumstabilized zirconia(YSZ).DFT calculation confirms sucha form of metastability, also showingthat highoxygen defect concentration favorsthe cubic phase.Moreover, high oxygen deficiencyin the nanoionics leadsto an unexpected“two-regime” conductivitywith high values(sigma> 1 S cm-1at 600 °C)at high pO2and lowerionic conductivity (sigma~0.1 S cm-1at 600 °C) at low pO2.Ionic conductivity at low pO2occurs with high activation energy (Ea > 1.5 eV), suggestingthusa drastic decrease in mobility for high concentration of defects

Bandgap calculations and trends of organometal halide perovskites

Energy production from the Sun requires a stable efficient light absorber. Promising candidates in this respect are organometal perovskites (ABX3), which have been intensely investigated during the last years. Here, we have performed electronic structure calculations of 240 perovskites composed of Cs, CH3NH3, and HC(NH2)2 as A-cation, Sn and Pb as B-ion, and a combination of Cl, Br, and I as anions. The calculated gaps span over a region from 0.5 to 5.0 eV. In addition, the trends over bandgaps have been investigated: the bandgap increases with an increase of the electronegativities of the constituent species, while it reduces with an increase of the lattice constants of the system

Vibrational characterization of dinaphthylpolyynes: A model system for the study of end-capped sp carbon chains

We perform a systematic investigation of the resonance and vibrational properties of naphthyl-terminated sp carbon chains (dinaphthylpolyynes) by combined multi-wavelength resonant Raman (MWRR) spectroscopy, ultraviolet-visible spectroscopy, and Fourier-transform infrared (FT-IR) spectroscopy, plus ab initio density functional theory (DFT) calculations. We show that the MWWR and FT-IR spectroscopies are particularly suited to identify chains of different lengths and different terminations, respectively. By DFT calculations, we further extend those findings to sp carbon chains end-capped by other organic structures. The present analysis shows that combined MWRR and FT-IR provide a powerful tool to draw a complete picture of chemically stabilized sp carbon chains.Comment: The following article has been accepted by Journal of Chemical Physics. After it is published, it will be found at http://jcp.aip.org

2-Photon tandem device for water splitting:comparing photocathode first versus photoanode first designs

This work analyzes the differences between a ‘photoanode first’ and a ‘photocathode first’ 2-photon water splitting device.</p