An electron-transporting host material compatible with diverse triplet emitters used for highly efficient red- and green-electrophosphorescent devices

A bifluorene analogue, T2N, containing a pyridyl moiety serves as both a host and an efficient electron-transporting material that is compatible with various heavy metal-containing red (Ir, Ru, Os, and Pt) and green (Ir) phosphors for highly efficient phosphorescent OLEDs possessing simple device architectures.     

Experimental and theoretical investigation of the stability of Pt-3d-Pt(111) bimetallic surfaces under oxygen environment

The stability of the Pt-3d-Pt(111) (3d = Ti, V, Cr, Mn, Fe, Co, or Ni) bimetallic surface structures in the presence of adsorbed oxygen has been investigated by means of density functional theory (DFT). The dissociative binding energies of oxygen on Pt-3d-Pt(111) (i.e., subsurface 3d monolayer) and 3d-Pt-Pt(111) (i.e., surface 3d monolayer) were calculated. All of the Pt-3d-Pt(111) surfaces were found to have weaker oxygen binding energies than pure Pt(111) whereas all of the 3d-Pt-Pt(111) surfaces were found to have stronger oxygen binding energies than pure Pt(111). The total heat of reaction was calculated for the segregation for 3d metal atoms from Pt-3d-Pt(111) to 3d-Pt-Pt(111) when exposed to a half monolayer of oxygen. All of the Pt-3d-Pt(111) subsurface structures were predicted to be thermodynamically unstable with adsorbed oxygen. In addition, the segregation of subsurface Ni and Co to the surfaces of Pt-Ni-Pt(111) and Pt-Co-Pt(111) was investigated experimentally using Auger electron spectroscopy (AES) and high-resolution electron energy loss spectroscopy (HREELS). AES and HREELS confirmed the trend predicted by DFT modeling and showed that both the Pt-Ni-Pt(111) and Pt-Co-Pt(111) surface structures were unstable in the presence of adsorbed oxygen. The activation barrier of the segregation of surbsurface Ni and Co atoms was determined to be 15 +/- 2 and 7 +/- 1 kcal/mol, respectively. These results are further discussed for their implication in the design and selection of cathode bimetallic electrocatalysts for the oxygen reduction reaction (ORR) in polymer electrode membrane (PEM) fuel cells.     

Synthesis, structure, and magnetic properties of Cs(2-x)RbxCu3P4O14 (0.0 </= x </= 0.8): a new series of copper(II) phosphates containing periodic arrays of staggered square-planar CuO4 trimers

In our continued exploratory synthesis of compounds containing transition-metal oxide magnetic nanostructures, a new copper(II) phosphate phase, Cs2Cu3P4O14 (1), was isolated employing the mixed CsCl/2CsI molten flux. The X-ray single-crystal structural analysis shows that the Cs2Cu3P4O(14) phase crystallizes in a monoclinic space group with a = 7.920(2) A, b = 10.795(2) A, c = 7.796(2) A, beta = 103.90(3) degrees , and V = 646.9(2) A(3); P2(1)/c (No. 14); Z = 2. The structure has been refined by the full-matrix least-squares method to a final solution with R1 = 0.0248, wR2 = 0.0553, and GOF = 1.02. The three-dimensional Cu-O-P framework exhibits pseudo-one-dimensional channels where the Cs+ cations reside. The framework consists of trimeric CuO4 square-planar units stacked in a staggered configuration. These CuO4 trimers are interlinked by the P2O7 units via vertex-sharing O atoms. The stacked CuO4 units are slanted with respect to the Cu...Cu...Cu vector, resulting in additional Cu-O long bonds, 2.71(1) A, and a possibly shortened Cu...Cu distance, 3.38(3) A. 1 shows limited cation substitution with smaller alkali-metal cations; in fact, only a relatively small concentration of Cs+ can be substituted by Rb+ to form Cs(2-x)RbxCu3P4O14 (0.0 相似文献   

Surfactant-assisted hollowing of Cu nanoparticles involving halide-induced corrosion-oxidation processes

We have demonstrated a simple fabrication of hollow nanoparticles by halide-induced corrosion oxidation with the aid of surfactants. Cuprous oxide Cu2O nanoshells can be generated by simply mixing Cu nanoparticles with alkyltrimethylammonium halides at 55 degrees C for 16 min. The hollowing mechanism proposed is that absorption of surfactants onto the Cu surface facilitates the formation of the void interior through an oxidative etching process. Upon extending the reaction up to 4 h, fragmentation, oxidation, and self-assembly were observed and the CuO ellipsoidal structures were formed. The headgroup lengths of the surfactants influenced the degree of CuO ellipsoidal formation, whereby longer surfactants favored the generation of ellipsoids. Optical absorption measured by UV-visible spectroscopy was used to monitor both oxidation courses of Cu-->Cu2O and Cu2O-->CuO and to determine the band-gap energies as 2.4 eV for Cu2O nanoshells and 1.89 eV for CuO ellipsoids. For the contact-angle measurements, the wettability changed from hydrophilicity (18 degrees) to hydrophobicity (140 degrees) as the Cu2O nanoshells shifted to CuO ellipsoids.