Fluorene-Based Copolymers Containing Dinaphtho-s-indacene as New Building Blocks for High-Efficiency and Color-Stable Blue LEDs

By incorporating a new building block, 7,7,15,15-tetraoctyldinaphtho-s-indacene (NSI), into the backbone of poly(9,9-dioctylfluorene) (PFO), a novel series of blue light-emitting copolymers (PFO-NSI) have been developed. The insertion of the NSI unit into the PFO backbone leads to the increase of local effective conjugation length, to form low-energy fluorene-NSI-fluorene (FNF) segments that serve as exciton trapping sites, to which the energy transfers from the high-energy PFO segments. This causes these copolymers to show red-shifted emissions compared with PFO, with a high efficiency and good color stability and purity. The best device performance with a luminance efficiency of 3.43 cd . A(-1), a maximum brightness of 6 539 cd . m(-2) and CIE coordinates of (0.152, 0.164) was achieved.

Preparation and Luminescence Properties of Gd2MoO6:Eu3+ Nanofibers and Nanobelts by Electrospinning

Gd2MoO6:Eu3+ nanofibers and nanobelts have been prepared by a combination method of the sol-gel process and electrospinning. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy, photoluminescence, and low voltage cathodoluminescence as well as kinetic decays were used to characterize the resulting samples. The results of XRD and FTIR indicate that the Gd2MoO6:Eu3+ samples have crystallized at 600 degrees C with the monoclinic (alpha) structure. The SEM and TEM results indicate that the as-formed precursor fibers and belts are uniform and that the as-prepared nanofibers and nanobelts consist of nanoparticles. Gd2MoO6:Eu3+ phosphors show their strong characteristic emission under UV excitation (353 nm) and low voltage electron-beam excitation (3 kV), making the materials have potential applications in fluorescent lamps and field-emission displays.

Improved color purity and efficiency by a coguest emitter system in doped red light-emitting devices

We demonstrate red organic light-emitting diodes (OLEDs) with improved color purity and electroluminescence (EL) efficiency by codoping a green fluorescent sensitizer 10-(2-benzothiazolyl)-2,3,6,7-tetrahydro-1, 1, 7,7-tetramethyl-1H, 5H, 11H-(1)-benzopyropyrano(6,7-8-ij)quinolizin-11-one (C545T) as the second dopant and a red fluorescent dye 4-(dicyanomethylene)-2-t-butyl-6(1,1,7,7tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) as the lumophore into tris(8-hydroquinoline) aluminum (Alq(3)) host. It was found that the C545 T dopant did not by itself emit but assisted the carrier trapping from the host Alq(3) to the red emitting dopant. The red OLEDs realized by this approach not only kept the purity of the emission color, but also significantly improved the EL efficiency. The current efficiency and power efficiency, respectively, reached 12 cd/A at a current density of 0.3 mA/cm(2) and 10lm/W at a current density of 0.02 mA/cm(2), which are enhanced by 1.4 and 2.6 times compared with devices where the emissive layer is composed of the DCJTB doped Alq(3), and a stable red emission (chromaticity coordinates: x = 0.64, y = 0.36) was obtained in a wide range of voltage. Our results indicate that the coguest system is a promising method for obtaining high-efficiency red OLEDs.

Green light-emitting polyfluorenes with improved color purity incorporated with 4,7-diphenyl-2,1,3-benzothiadiazole moieties

By incorporating 4,7-diphenyl- 2,1,3 benzothiadiazole instead of 2,1,3-benzothiadiazole into the backbone of polyfluorene, we developed a novel series of green light- emitting polymers with much improved color purity. Compared with the state-of-the-art green light-emitting polymer, poly(fluorene-co-benzothiadiazole) (lambda max = 537 nm), the resulting polymers (lambda(max) = 521 nm) showed 10-20 nm blueshifted electroluminescence (EL) spectra and greatly improved color purity because the insertion of two phenylene units between the 2,1,3-benzothiadiazole unit and the fluorene unit reduced the effective conjugation length in the vicinity of the 2,1,3-benzothiadiazole unit. As a result, the resulting polymers emitted pure green light with CIE coordinates of (0.29, 0.63), which are very close to (0.26, 0.65) of standard green emission demanded by the National Television System Committee (NTSC). Moreover, the insertion of the phenylene unit did not affect the photoluminescence (PL) and EL efficiencies of the resulting polymers. PL quantum efficiency in solid films up to 0.82 was demonstrated. Single-layer devices (ITO/PEDOT/ polymer/Ca/Al) of these polymers exhibited a turn-on voltage of 4.2 V, luminous efficiency of 5.96 cd A(-1) and power efficiency of 2.21 lm W-1. High EL efficiencies and good color purities made these polymers very promising for display applications.

Determination of purity and molecular weight of calmodulin by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

The purity and molecular weight of calmodulin have been determined by means of matrix-assisted laser desorption/ionization time of flight mass spectrometry, and the results have been discussed. The experimental results demonstrate that this method is high sensitive and rapid as compared with other traditional methods.

Purification of High-quality Plastid DNA from the Brown Alga Laminaria japonica Sporophytes

Extracting DNA from a variety of algae is rather difficult because of high levels of polysaccharides, tannins, and phenolics as these interfere with DNA isolation and downstream applications. High-quality plastid DNA (ptDNA) purification is particularly difficult because of its small proportion in total genomic DNA. This report describes an improved protocol for ptDNA purification that efficiently produces high-quality ptDNA from sporophytes of Laminaria japonica and several other algae. This improved protocol simplifies procedures for ptDNA purification and improves yield to 150-200 mu g of ptDNA per 100 g of frozen algal tissue. Polymerase chain reaction (PCR) amplification of conserved sequences has been used to verify purity of the ptDNA product.

An efficient combination of supercritical fluid extraction and high-speed counter-current chromatography to extract and purify homoisoflavonoids from Ophiopogon japonicus (Thunb.) Ker-Gawler

Supercritical fluid extraction (SFE) was used to extract homoisoflavonoids from Ophiopogon japonicus (Thunb.) Ker-Gawler. The optimization of parameters was carried out using an orthogonal test L-9 (3)(4) including pressure, temperature, dynamic extraction time and the amount of modifier. The process was then scaled up by 100 times with a preparative SFE system under the optimized conditions of 25 MPa, 55 degrees C, 4.0 h and 25% methanol as a modifier. Then crude extracts were separated and purified by high-speed counter-current chromatography (HSCCC) with a two-phase solvent system composed of n-hexane/ethyl acetate/methanol/ACN/water (1.8:1.0:1.0:1.2:1.0 v/v). There three homoisoflavonoidal compounds including methylophiopogonanone A 6-aldehydo-isoophiopogonone A, and 6-formyl-isoophiopogonanone A, were successfully isolated and purified in one step. The collected fractions were analyzed by HPLC. In each operation, 140 mg crude extracts was separated and yielded 15.3 mg of methylophiopogonanone A (96.9% purity), 4.1 mg of 6-aldehydo-isoophiopogonone A (98.3% purity) and 13.5 mg of 6-formyl-isoophiopogonanone A (97.3% purity) respectively. The chemical structure of the three homoisoflavonoids are identified by means of ESI-MS and NMR analysis.

One step isolation and purification of liquiritigenin and isoliquiritigenin from Glycyrrhiza uralensis Risch using high-speed counter-current chromatography

High-speed counter-current chromatography (HSCCC) technique in semi-preparative scale has been successfully applied to the separation of bioactive flavonoid compounds, liquiritigenin and isoliquiritigenin in one step from the crude extract of Glycyrrhiza uralensis Risch. The HSCCC was performed using a two-phase solvent system composed of n-hexane-ethyl acetate-methanol-acetonitrile-water (2:2:1:0.6:2, v/v). Yields of liquiritigenin (98.9% purity) and isoliquiritigenin (98.3% purity) obtained were 0.52% and 0.32%. Chemical structures of the purified liquiritigenin and isoliquiritigenin were identified by electrospray ionization-MS (ESI-MS) and NMR analysis. (c) 2005 Published by Elsevier B.V.