Enhanced hardness in B-doped ZnO thin films on fused quartz substrates by pulsed-laser deposition

B-doped ZnO thin films have been fabricated on fused quartz substrates using boron-ZnO mosaic target by pulsed-laser deposition technique, and the mechanical properties have been studied by nanoindentation continuous stiffness measurement technique and transmission electron microscope (TEM). Nanoindentation measurement revealed that the hardness of B-doped ZnO films, 9.32 ± 0.90 to 12.10 ± 1.00 GPa, is much greater than that of undoped ZnO films and very close to that of traditional semiconductor Si. The mean transmittance (%) is larger than 81% in the visible range (380-780 nm) for all the films, and the Hall effect measurement showed that the carrier density is around 2 × 10²⁰ cm⁻³ and the resistivity lower than 3 × 10⁻³ Ω cm. TEM characteristics show undoped thin films have more amorphous area between grains while the B-doped ZnO films have thin grain boundaries. We suggest that the grain boundaries act as the strain compensation sites and the decrease in thickness of grain boundaries enhances the hardness of the B-doped ZnO films.     

Phenylene vinylene‐based electroluminescent polymers with electron transport block in the main chain

We report a new route for the design of soluble phenylene vinylene (PV) based electroluminescent polymers bearing electron‐deficient oxadizole (OXD) and triazole (TZ) moieties in the main chains with the aryloxy linkage. Both series of the PV‐based polymers were prepared by Wittig reaction. By properly adjusting the OXD and/or TZ content through copolymerization, we can achieve an enhanced balance of hole‐ and electron injections, such that the device efficiency is significantly improved. Light‐emitting diodes fabricated from P1, P2, P3, P4, P5, P6, and P7 with the configuration of Indium–Tin Oxide (ITO)/Poly (styrene sulfonic acid) doped poly (ethylenedioxythiophene) (PEDOT)/polymer/Ca/Al, emit bright green light with the maximum peak around 500 nm. For the device using the optimal polymer (P4) as emitting layer, a maximum brightness of 1300 cd/m² at 20 V and a maximum luminance efficiency of 0.325 cd/A can be obtained. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3469–3478, 2006     

Eucaglobulin, A New Complex of Gallotannin and Monoterpene from Eucalyptus globulus

EucalyPtusgl0bulusLabill.(Myrtaceae)isakindofmedicinalplantwidelydistributedintheYunnanpr0vinceofChina.ItSleaves,rootSandffoitShavebeenusedastraditionalremediesforthetreatmentofinfluenza,dysentery,enteritis,rheumatalgiaandbleeding.BesidesvolatileterpenoidconstituentSintheessential0iloftheleavesandfruits,theoccurrenceofanumber0fphloroglucinol-sesquiterpene-or-m0n0terpene-c0upledcomPoundsnamedmacrocarpals'andeugl0bals'intheleavesandbudshasbeenrepofted.Inordertostudythechendcalandbioactivecon…     

A Novel Method to Synthesize Polyorganozircosilazane

A new kind of polyorganozircosilazane as Si/Zr/C/N-based ceramic precursor was synthesized from the condensation reaction of hexamethyleyclotrisilazane lithium salts(D3^NLi）and zirconium tetrachloride(ZrCl4).In the presence of N,N,N’,N’-tetramethyl ethylene diamine(TMEDA),polyorganozircosilazane was obtained in high yield.     

On the measure of the spectrum for the almost Mathieu operator

We obtain partial results on the conjecture that for the almost Mathieu operator at irrational frequency, , the measure of the spectrum,S(, , )=|4–2|. For ||2 we show that if _n is rational and irrational, then .Dedicated to Res Jost and Arthur WightmanResearch partially supported by U.S. NSF grant number DMS-8801918 and by BSF under grant number 88-00325     

A193Ir Mössbauer study of Pt−Ir catalysts prepared by impregnantion of silica with H2MCl6

The state of iridium on Pt?Ir catalysts prepared by impregnation of amorphous silica with H₂IrCl₆ and H₂PtCl₆ was studied by¹⁹³Ir Mössbauer spectroscopy after different steps of preparation. The Ir is adsorbed in its trivalent state, presumably as [IrCl₆]^3?. Calcination in air at 450°C converts this to IrO₂. The metallic clusters formed by subsequent reduction in H₂ at 200°C show a strong tendency towards segregation of Ir and Pt and re-oxidize partially when exposed to air at ambient temperature. In both respects the behaviour is similar to that of samples prepared by co-exchange from [Ir(NH₃)₅Cl]Cl₂ and Pt(NH₃)₄Cl₂. H₂O.     

Electromagnetic transition probability from the ground to the first excited 2+ state in138ce

The ratio of the B(E2) values for the 0 ₁ ⁺ → 2 ₁ ⁺ transitions in¹³⁸Ce and¹⁴²Ce was measured by Coulomb excitation with α-particles. From the known value of the transition probability in¹⁴²Ce it results: B(E2,¹³⁸Ce, 0 ₁ ⁺ → 2 ₁ ⁺ =0.45 +/?0.03 e² b ²     

Rhenium

Ohne Zusammenfassung     

Photophysical properties of borondipyrromethene analogues in solution

The photophysical properties of seven new 8-(p-substituted)phenyl analogues of 4,4-difluoro-3,5-dimethyl-8-(aryl)-4-bora-3a,4a-diaza-s-indacene (derivatives of the well-known fluorophore BODIPY) in several solvents have been studied by means of absorption and steady-state and time-resolved fluorimetry. For each compound, the fluorescence quantum yield and lifetime are lower in solvents with higher polarity owing to an increase in the rate of nonradiative deactivation. Increasing the electron withdrawing strength of the p-substituent on the phenyl group in position 8 also leads to lower fluorescence quantum yields and lifetimes. When the p-substituent on the phenyl group in position 8 is a tertiary amine [8-(4-piperidinophenyl), 8-(4-N,N-dimethylaminophenyl), and 8-(4-morpholinophenyl)], the low quantum yields of these compounds in more polar solvents can be rationalized by the inversion of the energy levels of an apolar, highly fluorescent and a polar, nonfluorescent excited state, where charge transfer from the tertiary amine to the BODIPY unit occurs. These amine analogues can be protonated at low pH in aqueous solution. Fluorescence titrations yielded pK(a) values of their conjugate ammonium salts which are in agreement with the electron donating tendency of the amine group: piperidino (4.15) > dimethylamino (2.37) > morpholino (1.47), with the pK(a) values in parentheses. The rate constant of radiative deactivation (k(f)) is the same for all compounds in all solvents studied (k(f) = 1.4 x 10(8) s(-1)).