High efficiency red organic light-emitting diodes based on microcavity structure

We demonstrate high efficiency red organic light-emitting diodes (OLEDs) based on a planar microcavity comprised of a dielectric mirror and a metal Mirror. The microcavity devices emitted red light at a peak wavelength of 610 nm with a full width at half maximum (FWHM) of 25 nm in the forward direction, and an enhancement of about 1.3 factor in electroluminescent (EL) efficiency has been experimentally achieved with respect to the conventional noncavity devices. For microcavity devices with the structure of distributed Bragg reflectors (DBR)/indium-tin-oxide(ITO)/V2O5/N,N'-di(naphthalene-1-yl)-N,N'-diphenyl-benzidine(NPB)/4-(dicy-anome-thylene)-2-t-butyl-6(1,1,7,7-tetrame-thyljulolidyl-9-enyl)-4H-pyran(DCJTB):tris(8-hydroxyquinoline) aluminium (Alq(3))/Alq(3)/LiF/Al, the maximum brightness arrived at 37000 cd/m(2) at a current density of 460.0 mA/cm(2), and the current efficiency and power efficiency reach 13.7 cd/A at a current density of 0.23 mA/cm(2) and 13.3 lm/W respectively.

Deformation mechanism of polystyrene toughened with sub-micrometer monodisperse rubber particles

Core-shell polybutadiene-graft-polystyrene (PB-g-PS) rubber particles with different ratios of polybutadiene to polystyrene were prepared by emulsion polymerization through grafting styrene onto polybutadiene latex. The weight ratio of polybutadiene to polystyrene ranged from 50/50 to 90/10. These core-shell rubber particles were then blended with polystyrene to prepare PS/PB-g-PS blends with a constant rubber content of 20 wt%. PB-g-PS particles with a lower PB/PS ratio (<= 570/30) form a homogeneous dispersion in the polystyrene matrix, and the Izod notched impact strength of these blends is higher than that of commercial high-impact polystyrene (HIPS). It is generally accepted that polystyrene can only be toughened effectively by 1-3 mu m rubber particles through a toughening mechanism of multiple crazings. However, the experimental results show that polystyrene can actually be toughened by monodisperse sub-micrometer rubber particles. Scanning electron micrographs of the fracture surface and stress-whitening zone of blends with a PB/PS ratio of 70/30 in PB-g-PS copolymer reveal a novel toughening mechanism of modified polystyrene, which may be shear yielding of the matrix, promoted by cavitation.

Synthesis, structure and characterization of a novel asymmetrical half-sandwich binuclear iron carborane complex [eta(5)-C5H3 (t-Bu)(2)](2)Fe-2 (CO)(3)Se2C2B10H10

Halfsandwich iron dicarbonyl complex [eta(5)-C5H3(t-Bu)(2)]Fe(CO)(2)Cl(1) reacts with 1, 2-dilithium diseleno carborane Li(2)Se(2)C(2)B(10)H10 (2) to give a binuclear iron carborane complex [eta(5)-C5H3(t-Bu)(2)](2)Fe-2(CO)(3) Se2C2B10H10(3). The X-ray diffraction analysis of complex 3 reveals that one of the iron atoms is chiral.

Measurement of the single-color three-photon resonant ionization spectrum of atomic uranium under the "equivalent wavelength effect laser" interaction

Using Nd: YAG laser (532 nm) pumped mixed-dye laser. we obtained the output of this dye enhanced at the wavelength interval equivalent to that given by the copper vapor laser pumped dye laser. This measure favored is with the measurement of single-color three-photon resonant ionization spectrum of atomic uranium in the range of 562-586 nm,which is otherwise not efficiently covered by Nd: YAG laser pumped dye laser with any single dye. Thus 140 U I energy levels were obtained and the peaks of interest 575.814 nm and 575.836 rim were well resolved and their relative intensity determined.

Synthesis, characterization and molecular structure of a novel asymmetrical half-sandwich binuclear iron carborane complex Cp ' Fe-2(2)(CO)(3)(Se2C2B10H10)

The half-sandwich methylcyclopentadlenyl iron carbonyl complex reacted with 1,2-dilithium diselenolate carborane Li2Se2C2B10H10 (1) which was produced by the insertion of element Se into 1, 2-dilithium carborane to give a half-sandwich binuclear iron carborane complex Cp'Fe-2(2)(CO) 3Se2C2B10H10 (3). X-ray structural analysis of complex 3 reveals that one of the iron atoms is chiral.

Dinuclear half-sandwich complexes containing bridging 1,2-dicarba-closo-dodecaborane-1,2-dichalcogenolato ligands. Molecular structures of Cp2Fe2(CO)(3)[mu-Se2C2(B10H10)], Cp2Ru2[mu-S2C2(B10H10)](2), and CP*Ru-2(2)(mu-Se)[mu-Se2C2(B10H10)].

Three prototypes of dinuclear complexes were obtained from the reactions of dilithium 1,2-dicarbacloso-dodecaborane-1,2-dichalcogenolates, (B10H10)C-2-(ELi)(2) (E = S, Se), with CpFe(CO)(2)Cl (1), CpRu(PPh3)(2)Cl (2), or [Cp*RuCl2](2) (3), respectively, and their structures have been determined by X-ray crystallography.

Carbon ceramic electrodes modified with sub-micron particles of new methylene blue (NMB) intercalated alpha-zirconium phosphate

New methylene blue-intercalated a-zirconium phosphate (NMBZrP) was synthesized in the presence of n-butylamine and characterized by powder XRD, FTIR, TEM and elemental analysis. Sub-micron particles of NMBZrP in deionized water were apt to deposit onto the surface of graphite powder to yield graphite powder-supported NMBZrP, which was subsequently dispersed into methyltrimethoxysilane-derived gels to fabricate surface-renewable, stable, rigid carbon ceramic electrodes containing new methylene blue. Cyclic voltammetric studies revealed that peak currents of the NMBZrP-modified electrode were surface-confined at low scan rates but diffusion-controlled. at high scan rates. In addition, NMBZrP immobilized in a carbon ceramic matrix presented a two-electron, three-proton redox process in acidic aqueous solution in the pH range from 0.52 to 3.95.

Lasing behavior in DCM-doped PVK microcavity

A surface emitting microcavity was formed by sandwiching a polymer film containing PVK, Alq(3) and DCM between a distributed Bragg reflector (DBR) with a reflectivity of 99% and a silver film (300 nm). The lasing phenomenon was observed in DCM-doped PVK microcavity. The full width at half maximum (FWHM) was 0.6 nm with the peak wavelength at 603 nm. The threshold energy for lasing was estimated to be about 2.5 mu J per pulse. (C) 2000 Published by Elsevier Science S.A. All rights reserved.

Stimulated emission in the blue wavelength region from a copolymer containing PPV segment

The lasing properties of a soluble conjugated polymer, Poly[1,8-octanedioxy-2,6-dimethoxy-1,4-phenylene-1,2-ethenylene-1,2-phenylene-1,2-ethenylene-3,5-dimethoxy-1,4-phenylene] (CNMBC-Ph) in chloroform solution were investigated. The third harmonic radiation of a Nd:YAG laser was used as the pump light. The stimulated emission with a linewidth of 15 nm was observed in the blue wavelength region with the peak at 450 nm. The threshold pulse peak power was about 2.8 MW/cm(2). The energy conversion yield of the laser was estimated to be about 3.4%. The maximum peak power of the laser output pulse reached 40 kW. (C) 2000 Published by Elsevier Science S.A. All rights reserved.

Photoluminescent properties of dye-doped poly(N-vinyleabzole) (PVK) in microcavity

A surface emitting microcavity was formed by sandwiching a polymer film containing poly(N-vinyleabzole) (PVK). 8-hydroxyquinoline aluminium (Alq(3)) and 4-(Dicyanome thylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-Pyran(DCM) between a distributed Bragg reflector (DBR) with a reflectivity of 99% and a silver film. The sample was optically pumped with 250 ps pulses at 2 Hz repetition rate by a 355 nm line of the third harmonic of a mode-lock Nd:YAG laser. The lasing phenomenon was observed in DCM-doped PVK microcavity. The full width at half maximum (FWHM) was 3 nm with the peak wavelength at 602 nm. The threshold energy for lasing was estimated to be about 3 mu J. (C) 2000 Elsevier Science S.A. All rights reserved.

Synthesis and characterization of polynuclear half-sandwich lanthanoid complexes [Na(THF)(6)](2)[(Cp6Sm6Se13)-Sm-t] and [Li(LHF4](2)[Cp6Nd6Se13]

The half-sandwich tert-butyl cyclopentadienyl lanthanoid complexes {[Cp ' Ln(THF)](2)(mu (2)-Cl)(2)(mu (3)-Cl)(3)Na(THF)}(n) [Cp ' = eta (5)-' BuC5H4; Ln = Nd (1a), Sm (1b), Gd (1c), Yb (1d)] are prepared by the reaction of anhydrous lanthanoid trichloride, LnCl(3), with NaCp ' in THF solution. Complex 1b reacts with Na2Se5 to give hexanuclear samarium polyselenide complexes [Na(THF)(6)](2)[Cp-6' SM6(mu (6)-Se)(mu -Se-2)(6)] (2). An analogous cyclopentadienyl neodymium polyselenide complex [Li(THF)(4)](2)[Cp6Nd6(mu (6)-Se)(mu -Se-2)(6)] (3) is synthesized by the reaction of [CpNdCl2. 2LiCl . 5THF] with Na2Se5 in THF solution. The molecular structures of 1a and 2 were determined by X-ray crystal structure analysis. Complex 2 contains an interstitial selenium atom which is coordinated with six samarium atoms. (C) 2001 Elsevier Science BN. All rights reserved.

Half-sandwich metal diselenolate complexes Cp#M(NO)(SePh)(2) (M = Mo or W; Cp# = Cp or MeCp) as ligands. Synthesis of selenolate-bridged heterobimetallic compounds

The reactions of half-sandwich diselenolate Mo and W complexes (CpM)-M-#(NO)(SePh)(2) (M = Mo; Cp-# = Cp' (1a), MeCp (1b); M = W; Cp-# = Cp' (1c)) with (Norb)Mo(CO)(4), Ni(COD)(2) and Fe(CO)(5) have been investigated. Treatment of (1a), (1b) and (1c) with (Norb)Mo(CO)(4) in PhMe gave the bimetallic complexes: Cp'Mo(NO)(mu -SePh)(2)Mo(CO)(4) (2a), MeCpMo(NO)(mu -SePh)(2)Mo(CO)(4) (2b) and Cp'W(NO)(mu -SePh)(2)Mo(CO)(4) (2c) in moderate yields. Irradiation of (1a) and (1c) in the presence of Fe(CO)(5) gave heterobimetallic complexes Cp'Mo(CO)(mu -SePh)(2)Fe(CO)(3) (3a) and Cp'W(NO)(mu -SePh)(2)Fe(CO)(3) (3c). Ni(COD)(2) reacts with two equivalents of (1a), (1b) and (1c) to give [Cp'Mo(NO)(mu -SePh)(2)](2)Ni (4a), [MeCpMo(NO)(mu -SePh)(2)](2)Ni (4b) and [Cp'W(NO)(mu -SePh)(2)](2)Ni (4c) in good yields. The new heterobimetallic complexes were characterized by i.r., H-1-n.m.r., C-13-n.m.r. and EI-MS spectroscopy.

Molecular dynamics simulation of sub-transition for polyethersulfone

Molecular dynamics (MD) simulations of a polyethersulfone (PES) chain are carried out in the amorphous state by using the Dreiding 2.21 force field at four temperatures. Two types of molecular motion, i.e, rotations of phenylene rings and torsions of large segments containing two oxygen atoms, two sulfur atoms, and five phenylene rings on the backbone, are simulated. The modeling results show that the successive phenylene rings should be in-phase cooperative rotations, whereas the successive large segments should be out-of-phase cooperative torsions. By calculating the diffusion coefficient for the phenylene ring rotations, it is found that this rotation contributes to the beta -transition of PES.

Stimulated emission in blue wavelength region from a copolymer

A dye laser based on the soluble conjugated polymer, Poly[1,8-octanedioxy-2,6-dimethoxy-1,4-phenylene-1,2-ethenylene-1, 4-phenylene-1,2-ethenylene-3,5-dimethoxy-1,4-phenylene], has been fabricated. The laser was pumped by light pulses from the third harmonic radiation of an Nd:YAG laser. The lasing was observed in the blue wavelength region with the peak at 450 nm. The threshold energy is about 19 mu J. The energy conversion yield of the laser is about 3.4%. The maximum peak power of the laser output pulse arrives at about 20 kW.

Half-sandwich cyclopentandienyl molybdenum and tungsten nitrosyl complexes containing bidentate sulfur ligands

Half-sandwich nitrosyl complexes Cp*M(NO)I-2 (M = Mo, or W) react with dithiocarbamates (NaS2CNMe2 and NaS2CNEt2) in THF to form of complexes: Cp*Mo(NO)I (S2CNMe2) (1), Cp*Mo(NO)I(S2CNEt2) (2), Cp*W(NO)I(S2CNMe2) (3) and Cp*W(NO)I(S2CNEt2) (4) in high yields. Treatments of Cp*M(NO)I-2 (M = Mo, W) or [CpMo(NO)I-2](2) with phosphinodithioate (NaS2PMe2) and phosphorodithioate [(NH4)S2P(OMe)(2)] result in complexes: Cp*Mo(NO)I(S2PMe2) (5a), CpMo(NO)I (S2PMe2) (5b), Cp*Mo(NO)(S2PMe2)(2) (6a), CpMo (NO) (S2PMe2)(2) (6b) and Cp*Mo(NO)I[S2P(OMe)(2)] (7), Cp*W(NO)I(S2PMe2) (8), Cp*W(NO) I[S2P(OMe)](2) (9). Treatment of (5a) and (5b) with an excess of NaS2PMe2 gives (6a) and (6b). The complexes have been characterized by their elemental analyses, i.r., H-1, C-13-n.m.r. and by EI-MS spectrometry.