One-pot redox syntheses of heteronanostructures of Ag nanoparticles on MoO3 nanofibers

A new one-pot redox route has been developed for simultaneous syntheses of Ag nanoparticles on MoO(3) nanofibers. Four different synthetic reactions that have been integrated into the one-pot synthesis include the oxidation of [Na(H(2)O)(2)](0.25)MoO(3) bronze, the reduction of silver ions, and the in situ simultaneous growth of the self-organized Ag nanoparticles and the MoO(3) nanofibers. This new strategy can be generally applicable to grafting various metal nanoparticles on nanofibers for new catalysis-related applications.     

Electrochemically partitioned assembly of organosulfur monolayers and nanoparticles

Partitionally assembled organosulfur monolayers were prepared by using an electrochemically assisted assembly method on gold films that were preseparated into two regions insulated from each other. Cyclic voltammetry (CV) and X-ray photoelectron spectroscopy (XPS) were employed to characterize the n-dodecanethiol (DDT) and the 11-mercaptoundecanoic acid (MUA) monolayers, which were separately assembled on different substrate regions. CV results indicated that both the DDT- and MUA-coated gold electrodes showed a blocking property toward the negatively charged redox probe Fe(CN)6(3-). However, when positively charged Ru(NH3)6(3+) was used as the redox probe, the MUA- and DDT-modified electrodes showed quasireversible and blocking CV features, respectively. These phenomena were attributed to different interactions between the negatively charged MUA surface and the negatively or positively charged redox probes. XPS spectra obtained on the MUA modified region exhibited an O(1s) peak and a small discrete C(1s) peak, which arose from the oxygen and the carbon atoms in the carboxylic acid groups, respectively. For the DDT-modified region, these two peaks were absent. CV and XPS experimental results provided strong evidence that different SAMs were selectively deposited onto different regions of the preexisting patterns of the substrate by electrochemically partitioned assembly. The partitionally assembled sulfur-based monolayers with different terminal groups were used to form location-selective nanoparticle assemblies. This electrochemically partitioned assembly technique has great potential in controllable constructions of molecular layers and nanostructures on different surface microarchitectures that are closely integrated on one substrate but insulated from each other.     

Application of chelate phosphine oxide ligand in EuIII complex with mezzo triplet energy level, highly efficient photoluminescent, and electroluminescent performances

The chelate phosphine oxide ligand bis(2-(diphenylphosphino)phenyl) ether oxide (DPEPO) was used as a unit neutral ligand to prepare the complex Eu(TTA)(3)(DPEPO) 1 (TTA = 2-thenoyltrifluoroacetonate). Compound 1 has a photoluminescence (PL) quantum yield of 55.3%, which is more than the twice of the PL quantum yield of Eu(TTA)(3)(TPPO)(2) (TPPO = triphenylphosphine oxide). Investigation indicated that DPEPO in 1 has the mezzo first triplet excited energy level (T(1)) between the first singlet excited energy level (S(1)) and T(1) of TTA, which may support one more additional energy transfer routines from the T(1) energy level of DPEPO to that of TTA, and consequently results in the improvement of energy transfer in the Eu(III) complex. DPEPO forms a complex with a more rigid and compact structure that can improve energy transfer between ligands and the center Eu(III) ion, support the higher saturation level by the coordinating ability of the oxygen atom in the ether moiety, and consequently enhance the PL intensity and efficiency of the corresponding Eu(III) complex. The multilayered electroluminescent (EL) device of 1 used as the red dopant exhibited an impressive brightness of 632 cd m(-2) at 25 V. The device had the excellent voltage-independent spectral stability with an emission peak at 615 nm. To the best of our knowledge, this luminescence is the brightest emission among Eu complexes with phosphine oxide ligands. The maximum external quantum yield (eta(ext)) of 2.89% and the maximum current and power efficiency of 4.58 cd A(-1) and 2.05 lm W(-1) were achieved at a low turn-on voltage of 7 V and current density of 0.021 mA cm(-2). These properties demonstrate that the chelate phosphine oxides ligand DPEPO can not only be favorable to form the rigid and compact complex structure and increase the efficiency of devices, but also reduce the ability of the formation of exciplex. DPEPO shows much better performance compared with the ordinary phosphine oxide ligand triphenylphosphine oxide.     

Formation and characterization of Sb2Te3 nanofilms on Pt by electrochemical atomic layer epitaxy

A nanocrystalline Sb2Te3 VA-VIA group compound thin film was grown via the route of electrochemical atomic layer epitaxy (ECALE) in this work for the first time. The electrochemical behavior of Te and Sb on Pt, Te on Sb-covered Pt, and Sb on Te-covered Pt was studied by methods of cyclic voltammetry, anode potentiodynamic scanning, and coulometry. A steady deposition of the Sb2Te3 compound could be attained after negatively stepped adjusting of the UPD potentials of Sb and Te on Pt in each of the first 40 depositing cycles. The structure of the deposit was proven to be the Sb2Te3 compound by X-ray diffraction. The 2:3 stoichiometric ratio of Sb to Te was verified by EDX quantitative analysis, which is consistent with the result of coulometric analysis. A nanocystalline microstructure was observed for the Sb2Te3 deposits, and the average grain size is about 20 nm. Cross-sectional SEM observation shows an interface layer about 19 nm in thickness sandwiched between the Sb2Te3 nanocrystalline deposit and the Pt substrate surface. The optical band gap of the deposited Sb2Te3 film was determined as 0.42 eV by FTIR spectroscopy and it is blueshifted in comparison with that of the bulk Sb2Te3 single crystal because of its nanocrystalline microstructure.     

Existence of multiple positive solutions for one-dimensional p-Laplacian

In this paper we consider the multipoint boundary value problem for one-dimensional p-Laplacian

     

1H NMR spectral studies on the polymerization mechanism of indole and its derivatives

The existence of NH bond according to the hydrogen nuclear magnetic resonance ((1)H NMR) spectra of polyindole and its derivatives, such as poly(5-bromoindole), poly(5-cyanoindole), poly(5-nitroindole), poly(5-methylindole), proved polymerization of high-quality polyindoles, which were electrosynthesized from middle strong Lewis acid boron trifluoride diethyl etherate (BFEE) and its mixed electrolytes with additional diethyl ether, occurred at 2,3-position. The elongation of the conjugation length made the chemical shift of all the protons of polyindoles to lower field in comparison with those of monomers.     

The observation of abnormal signals in laser flash photolysis: a type of probable synchronized nuclear spin signals

In laser flash photolysis (LFP) work, noise-like signals were observed together with transient absorption decay spectra in time domain. Analyzed results show that it is a valuable resonance spectrum of excited state molecules, in which four molecular cases are given here. We proposed that this kind signal might originate from nuclear or nuclear and electron spin resonance features in the excited molecules based on radio wave frequency spectrum levels and the significant interaction with static magnetic field.     

Alkali-metal-catalyzed addition of primary and secondary phosphines to carbodiimides. A general and efficient route to substituted phosphaguanidines

Organo alkali metal compounds such as (n)BuLi and (Me3Si)2NK act as excellent catalyst precursors for the addition of phosphine P-H bonds to carbodiimides, offering a general and atom-economical route to substituted phosphaguanidines, with excellent tolerability to aromatic C-Br and C-Cl bonds.