Catalyst-free synthesis of lithium hydride at room temperature.

An organic solvent-assisted catalyst-free mechanochemical reaction is developed to synthesize lithium hydride at mild gas pressures and room temperature. Studies show that the formation of intermediates on the surface of bulk lithium metal is crucial for the synthesis of high purity (>98%) LiH. This provides a new strategy for the large-scale production of lithium-based hydrogen storage materials.

One-Step Synthesis of Light Metal Nanoparticle from Metastable Complex.

Metal nanoparticles have attracted considerable scientific and technological interest in recent years, most related explorations and reports are focused on transition and noble metals. However, the synthesis and application of light metal nanoparticles represented by Mg have not been fully exploited, limited by their ultrahigh reactivity in air and preparation in harsh conditions. In this work, a simple and effective one-step organic solvent-assisted ball-milling process is developed to synthesize Mg and Li nanoparticles, which permits the formation of MgH2 in a hydrogen atmosphere in a one-step reaction process at ambient temperature. Further studies suggest that acetone chemisorbs on defects/surfaces of Mg during ball milling leading to the formation of a metastable magnesium complex, which significantly alters the physical and chemical characteristics of Mg grains. The formation of metastable complexes provides an attractive strategy to produce light metal nanoparticles and inspires the authors to study the interaction of organic solvents with light metals.

Superior Sodium Storage of Carbon-Coated NaV6O15 Nanotube Cathode: Pseudocapacitance Versus Intercalation.

To realize the effect of Na+ pseudocapacitance on the sodium storage of cathode materials, clewlike carbon-coated sodium vanadium bronze (NaV6O15) nanotubes (Na-VBNT@C) were synthesized via a facile combined sol-gel/hydrothermal method. The resultant Na-VBNT@C delivers high reversible capacities of 209 and 105 mA h g-1 at the rates of 0.1 and 10 C, respectively. Notably, at the higher rate of 5 C (1250 mA g-1), it can retain 94% of the initial capacity after 3000 cycles. It was found that the outstanding rate performance and the long-term cycling life of Na-VBNT@C are primarily due to the Na+ pseudocapacitance. Our study reveals that the design of Na+ pseudocapacitance is beneficial for harvesting the superior performance of NaV6O15 cathode material in sodium-ion batteries.

The Preparation and Electrochemical Performance of Olivine Cathode Materials Based on LiMn1/3Fe1/3Co1/3PO4/C.

Solid solution LiMn1/3Fe3Co1/33PO4/C ternary materials were prepared by sol-gel method with glycine or citric acid as chelating agents. SEM images indicate that the particles are well distributed with regular morphologies, and the particle sizes are around 300 nm for both samples. The cyclic voltammetry (CV) and charge-discharge curves show that the reversibility of Mn²+/Mn3+ couple is improved apparently. The redox potential corresponding to Fe²âº/Fe³âº couple has been increased which is beneficial to the energy density, and the redox potential related to Co²âº/Co³âº couple has been declined which could accelerate dynamics of intercalation/deintercalation and make the electrochemical reaction more smoothly. The obtained LiMn1/3Fe1/3Co1/33PO4/C materials with glycine as chelating agent deliver a capacity of 151.5, 142.6, 122.8, 97.9 mAh g⁻¹ at 0.05 °C, 0.1 C, 0.5 C and 1 C, respectively. And the obtained material with citric acid as chelating agent delivers a capacity of 150.8, 135.0, 111.5, 85.2 mAh g⁻¹, respectively, at the same rates.

Improving Photovoltaic Performance of the Linear A-Ar-A-type Small Molecules with Diketopyrropyrrole Arms by Tuning the Linkage Position of the Anthracene Core.

Two isomeric A-Ar-A-type small molecules of DPP2An(9,10) and DPP2An(2,6), were synthesized with two acceptor arms of diketopyrropyrroles (DPP) and a planar aryl hydrocarbon core of the different substituted anthracene (An), respectively. Their thermal stability, crystallinity, optoelectronic, and photovoltaic performances were investigated. Significantly red-shifted absorption profile and higher HOMO level were observed for the DPP2An(2,6) with 2,6-substituted anthracene relative to the DPP2An(9,10) with 9,10-substituted anthracene, as the former exhibited better planarity and a larger conjugate system. As a result, the solution-processing solar cells based on DPP2An(2,6) and PC71BM (w/w,1:1) displayed remarkably increased power conversion efficiency of 5.44% and short-circuit current density (Jsc) of 11.90 mA/cm(2) under 1% 1,8-diiodooctane additive. The PCE and Jsc values were 3.7 and 2.9 times those of the optimized DPP2An(9,10)-based cells, respectively. This work demonstrates that changing the linkage position of the anthracene core in the A-Ar-A-type SMs can strongly improve the photovoltaic properties in organic solar cells.

An investigation of a novel MnO2 network-Ni/PVDF double shell/core membrane as an anode for lithium ion batteries.

A novel MnO2 network-Ni/PVDF double shell/core fiber membrane is synthesized for the first time as an anode material for lithium ion batteries. The freestanding MnO2 nanosheet network is grown directly onto a conductive network-Ni/PVDF shell/core fiber membrane 3D current collector, avoiding the application of binders and conductive additives and simplifying the fabrication processing. The MnO2 nanosheet network can be tightly anchored to the Ni/PVDF fiber 3D current collector, and some small pores between the fibers and between the MnO2 nanosheets lead to fast charge transfer and ion transport. The unique MnO2 network-Ni/PVDF double shell/core fiber membrane exhibits a high charge/discharge capacity, long-term cycling stability and good rate capability.

Synthesis, optoelectronic properties of a dinuclear platinum(II) complex containing a binary cyclometalated ligand in the single-emissive-layer PLEDs.

A novel dinuclear platinum complex of (dfppy-mhb-dfppy)Pt(2)(acac)(2) was synthesized and characterized, where dfppy-mhb-dfppy is a binary C^N cyclometalated ligand containing two bridged 2,4-difluorophenylpyridine (dfppy) units and acac is 2,4-pentanedione anion. Compared to previously reported dinuclear platinum complexes with a binary ancillary ligand, this dinuclear platinum complex showed more intense excimer emission, peaking at 617 nm, besides its intrinsic emission in dilute dichloromethane solution. Single-emissive-layer (SEL) polymer light-emitting devices (PLEDs) using (dfppy-mhb-dfppy)Pt(2)(acac)(2) as dopant and a blend of poly (N-vinylcarbazole) (PVK) and 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD) as host matrix exhibited stable white emission at 1 wt% doping concentration under applied voltages from 7 V to 11 V. The stable white emission observed in the (dfppy-mhb-dfppy)Pt(2)(acac)(2)-doped SEL PLEDs indeed implies that the dinuclear platinum complex constructed by a binary cyclometalated ligand has a potential application in white-emitting SEL PLEDs.

Star-shaped trinuclear cyclometalated platinum(II) complexes as single-component emitters in white-emitting PLEDs.

Two star-shaped phosphorescent small molecules, Ph-3FPt(pic) and 4Ph-3FPt(pic), are single-component emitters in polymer white-light-emitting diodes (WPLEDs) that are comprised of three blue-light-emitting phosphorescent chromophores of FPt(pic) and are attached to benzene-1,3,5-trioxy- and 1,3,5-tri(4-oxyphenyl)benzene cores through a hexyloxy chain, respectively. Compared to their corresponding mono- or dinuclear platinum complexes, this class of star-shaped homotrinuclear cyclometalated platinum(II) complexes exhibited controllable excimer emission. Stable white/near-white emission was obtained in single-emissive-layer PLEDs by using the Ph-3FPt(pic) or 4Ph-3FPt(pic) as a single dopant and a blend of poly(vinylcarbazole) and 2-(4-biphenyl)-5-(4-tert-butyl-phenyl)-1,3,4-oxadiazole as a host matrix at dopant concentrations of 1-4 wt.%. Our results provide an efficient way to control excimer formation and to obtain a single-component emitter for use in WPLEDs.

Synthesis and optoelectronic properties of a heterobimetallic Pt(II)-Ir(III) complex used as a single-component emitter in white PLEDs.

To tune aggregation/excimer emission and obtain a single active emitter for white polymer light-emitting devices (PLEDs), a heterobimetallic Pt(II)-Ir(III) complex of FIr(pic)-C(6)DBC(6)-(pic)PtF was designed and synthesized, in which C(6)DBC(6) is a di(phenyloxyhexyloxy) bridging group, FIr(pic) is an iridium(III) bis[(4,6-difluorophenyl)pyridinato-N,C(2)'] (picolinate) chromophore and FPt(pic) is a platinum(II) [(4,6-difluorophenyl)pyridinato-N,C(2)'] (picolinate) chromophore. Its physical and opto-electronic properties were investigated. Interestingly, the excimer emission was efficiently controlled by this heterobimetallic Pt(II)-Ir(III) complex compared to the PL profile of the mononuclear FPt(pic) complex in the solid state. Near-white emissions were obtained in the single emissive layer (SEL) PLEDs using this heterobimetallic Pt(II)-Ir(III) complex as a single dopant and poly(vinylcarbazole) as a host matrix at dopant concentrations from 0.5 wt% to 2 wt%. This work indicates that incorporating a non-planar iridium(III) complex into the planar platinum(II) complex can control aggregation/excimer emissions and a single phosphorescent emitter can be obtained to exhibit white emission in SEL devices.

Synthesis and optoelectronic properties of a carbazole-modified platinum(II) complex in polymer light-emitting devices.

To improve opto-electronic properties and efficiently suppress excimer emission, a phenylpyridine (ppy)-based platinum(II) complex (C(16)OCz-ppy)Pt(acac) was synthesized and characterized, where C(16)OCz-ppy is a 2-phenylpyridine derivative appending a carbazole moiety and three hexadecyloxy methyl units in the parent phenylpyridine, and acac is acetylacetone. This carbazole-modified platinum(II) complex exhibited good thermal stability and three times higher photoluminescent quantum yield than its parent (2-phenylpyridine-C(2),N)(2,4-pentanedionato-O,O)platinum(II) complex [(ppy)Pt(acac)]. Single-emissive-layer polymer light-emitting devices using (C(16)OC(Z)-ppy)Pt(acac) as dopant and a blend of poly(N-vinylcarbazole) and 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole as host matrix presented a maximum current efficiency of 1.51 cd A(-1), which was 1.5 times higher than that from the (ppy)Pt(acac)-doped device with the same device structure. Little excimer emission and minor aggregation emission were observed in the (C(16)OC(Z)-ppy)Pt(acac)-doped PLEDs at different dopant concentrations and applied voltages. This work indicates that introducing a carbazole and three hexadecyloxy methyl groups into the planar platinum(II) complex can reduce molecular aggregation and excimer emissions, thus resulting in high luminance and stable EL spectra in comparison with the parent (ppy)Pt(acac).

Synergetic effect of efficient energy transfer and 3D pi-pi stack for white emission based on the block copolymers containing nonconjugated spacer.

A series of block copolymers containing nonconjugated spacer and 3D pi-pi stacking structure with simultaneous blue-, green-, and yellow-emitting units has been synthesized and characterized. The dependence of the energy transfer and electroluminescence (EL) properties of these block copolymers on the contents of oligo(phenylenevinylene)s has been investigated. The block copolymer (GEO8-BEO-YEO4) with 98.8% blue-emitting oligomer (BEO), 0.8% green-emitting oligomer (GEO), and 0.4% yellow-emitting oligomer (YEO) showed the best electroluminescent performance, exhibiting a maximum luminance of 2309 cd/m(2) and efficiency of 0.34 cd/A. The single-layer-polymer light-emitting diodes device based on GEO2-BEO-YEO4 emitted greenish white light with the CIE coordinates of (0.26, 0.37) at 10 V. The synergetic effect of the efficient energy transfer and 3D pi-pi stack of these block copolymers on the photoluminescent and electroluminescent properties are investigated.

A microfluidic device using a green organic light emitting diode as an integrated excitation source.

A simply fabricated microfluidic device using a green organic light emitting diode (OLED) and thin film interference filter as integrated excitation source is presented and applied to fluorescence detection of proteins. A layer-by-layer compact system consisting of glass/PDMS microchip, pinhole, excitation filter and OLED is designed and equipped with a coaxial optical fiber and for fluorescence detection a 300 microm thick excitation filter is employed for eliminating nearly 80% of the unwanted light emitted by OLEDs which has overlaped with the fluorescence spectrum of the dyes. The distance between OLED illuminant and microchannels is limited to approximately 1 mm for sensitive detection. The achieved fluorescence signal of 300 microM Rhodamine 6G is about 13 times as high as that without the excitation filter and 3.5 times the result of a perpendicular detection structure. This system has been used for fluorescence detection of Rhodamine 6G, Alexa 532 and BSA conjugates in 4% linear polyacrymide (LPA) buffer (in 1 x TBE, pH 8.3) and 1.4 fmol and 35 fmol mass detection limits at 0.7 nl injection volume for Alexa and Rhodamine dye have been obtained, respectively.