Green electroluminescence generated from the thin film based on a soluble lanthanide complex

Electroluminescent (EL) devices based on a soluble complex Tb(MDP)(3) [Tris-(monododecyl phthalate)Terbium] doped with poly (N-vinylcarbazole) (PVK), (2-(4-biphenyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole) (PBD) were fabricated. The device structures of ITO/PVK/PVK:PBD:Tb(MDp)(2)/Aiq(3)/Al and ITO/PVK:PBD:Tb(MDP)(3)/Alq(3)/Al were employed. The Tb(MDP), as emissive layer was spin-coated. The EL cell exhibited characteristic emission of terbium ion. (C) 2000 Elsevier Science S.A. All rights reserved.

Charge carrier mobility and electroluminescence in a green-emitting alternating block copolymer with a methoxy Bi-substituted chromophore

We determine the mobility of positive and negative charge carriers in a soluble green-emitting alternating block copolymer with, a methoxy bi-subsbituted conjugated segment. The negative charge carrier mobility of 6 x 10(-11) cm(2)/V.s is directly determined using space-charge-limited current analytical expressions. Positive charge carrier transport is also space-charge-limited, with a mobility of I x 10(-8) cm(2)/V.s. The electron trap distribution is exponential, with a characteristic energy of similar to 0.12 eV. A hole trap with energy similar to 0.4 eV was observed. This copolymer is used as emissive material in organic light-emitting diodes that present brightness of similar to 900 cd/m(2) at 12.5 V.

Sol-gel-derived amperometric biosensor for hydrogen peroxide based on methylene green incorporated in Nafion film

A hydrogen peroxide biosensor was fabricated by coating a sol-gel-peroxidase layer onto a Nafion-methylene green modified electrode. Immobilization of methylene green (MG) was attributed to the electrostatic force between MG(+) and the negatively charged sulfonic acid groups in Nafion polymer, whereas immobilization of horseradish peroxidase was attributed to the encapsulation function of the silica sol-gel network. Cyclic voltammetry and chronoamperometry were employed to demonstrate the feasibility of electron transfer between sol-gel-immobilized peroxidase and a glassy carbon electrode. Performance of the sensor was evaluated with respect to response time, sensitivity as well as operational stability. The enzyme electrode has a sensitivity of 13.5 mu A mM(-1) with a detection limit of 1.0 x 10(-7) M H2O2, and the sensor achieved 95% of the steady-state current within 20 s. (C) 2000 Elsevier Science B.V. All rights reserved.

Fabrication of layer-by-layer deposited multilayer films containing DNA and its interaction with methyl green

Multilayer films were fabricated by layer-by-layer electrostatic deposition techniques between poly(diallyIdimethylammonium chloride) (PDDA) and calf thymus DNA (CT DNA) on glassy carbon and quartz substrates. Electrochemical impedance spectroscopy (EIS), Fourier transform infrared (FTIR) spectroscopy and UV-vis spectroscopy demonstrated the uniform assembly of PDDA/DNA multilayer films, and X-ray photoelectron spectroscopy confirmed the elemental composition of the films. Moreover, the interaction of DNA in PDDA/DNA films with methyl green was investigated by UV-vis spectroscopy and circular dichroism (CD). (C) 2001 Elsevier Science B.V. All rights reserved.

Bright green organic electroluminescent devices based on a novel thermally stable terbium complex

A navel thermally stable terbium carboxylate complex, Tb(MTP)(3)(phen) (MTP=monotetradecyl phthalate, phen=1,10-phehanthroline), was synthesized and characterized. The device structure of glass substrate/indium-tin-oxide/poly(p-phenylenevinylene) (PPV)/poly (N-vinycarbazole) (PVK):Tb(MTP)(3)(phen): 1,3,4-oxadizole derivative (PBD)/tris(8-hydroxyquinoline) (Alq(3))/aluminum (Al) was employed to study the electroluminescent properties of Tb(MTP)(3)(phen). A green emission with extremely sharp spectral band of less than 10 nm at 544 nm peak wavelength was observed. A maximum luminance of 152 cd/m(2) and an external quantum efficiency of 0.017% were achieved at a drive voltage of 24 V. A possible mechanism of energy transfer based on the polymer doped with lanthanide organic complex was also proposed.

A new high efficiency green luminescent material - the system Al2O3-B2O3 containing Ce3+ and Tb3+ ions

To obtain high efficiency luminescent materials, the system Al2O3-B2O3 containing Ce3+ and Tb3+ ions with variation of B2O3-content, has been prepared by Al2O3, H3BO3, CeO2 and Tb4O7 under reducing atmosphere at 1250(j)ae. It is notable that the brightness of the sample with appropriate composition is similar to that of commercial phosphorous containing Ce3+ and Tb3+, indicating that a new high efficency green luminescent material was obtained with appropriate B2O3-content.

Efficient green electroluminescent cells using a poly(p-phenylene vinylene) multiblock copolymer sandwiched between carrier-transporting layers

With a newly synthesized poly(p-phenylene vinylene) (PPV) multiblock copolymer used in a triple-layer structure, efficient green light-emitting diodes with low driving voltage have been fabricated. The devices are turned on at 2.5 V, the brightness at 5 V is above 100 cd/m(2) and at 7 V is about 1650 cd/m(2), with an external quantum efficiency of about 1%. (C) 1998 Elsevier Science S.A. All rights reserved.

Synthesis and high efficiency green light-emitting diode of a soluble polymer

A soluble polymer emitting green color with high efficiency was synthesized. Bright green electroluminescence devices, both single layer and multilayer, were fabricated. The luminous efficiency was improved dramatically. Carrier injection from the electrodes to the emissive layer and concomitant green electroluminescence from the emissive layer were observed. A luminance of 920 cd/m(2) and luminous efficiency of 5.35 1m/W were achieved at a drive voltage of 15 V for the multilayer device. (C) 1997 Elsevier Science S.A.

Interaction of brilliant cresyl blue and methylene green with DNA studied by spectrophotometric and voltammetric methods

The binding behavior of two cationic dyes, brilliant cresyl blue (BCB) and methylene green (MG) to calf thymus DNA was studied by spectrophotometric and voltammetric methods. A red shift of the adsorption spectra and hypochromism accompany the binding of BCB and MG to calf thymus DNA. In 5 x 10(-2) mol dm(-3) NaCl, 5 x 10(-3) mol dm(-3) tris-HCl pH 6.87 buffer solution, the apparent binding constants are: K-BCB+ 3.0 x 10(4)M(-1) (N = 4.13) and K-MG+ = 8.8 x 10(4)M(-1) (n = 4.44). Electrochemical studies show that the formal potentials shift negatively upon addition of DNA, indicating that the oxidized forms of the dyes have stronger affinity to DNA than the reduced ones. K-BCB+/K-BCBH and K-MG+/K-MGH are evaluated to be 10.39 and 7.04. respectively. Our investigation suggests that the two cationic dyes interact with DNA predominantly via electrostatic interaction.

ELECTROCATALYTIC OXIDATION OF REDUCED NICOTINAMIDE COENZYMES AT METHYLENE GREEN-MODIFIED ELECTRODES AND FABRICATION OF AMPEROMETRIC ALCOHOL BIOSENSORS

Chemically modified electrodes with Methylene Green adsorbed on the graphite surface and incorporated into carbon paste exhibit excellent electrocatalytic ability for oxidation of NADH. Alcohol dehydrogenase, nicotinamide adenine dinucleotide (NAD+) and m

Characterization of the main light-harvesting chlorophyll a/b-protein complex of green alga, Bryopsis corticulans

The main light-harvesting chlorophyll a/b -protein complex (LHC II) has been isolated directly from thylakoid membranes of shiphonous green alga, Bryopsis corticulans Setch. by using two consecutive runs of anion exchange and gel-filtration chromatography. Monomeric and trimeric subcomplexes of LHC 11 were obtained by using sucrose gradient ultracentrifugation. Pigment analysis by reversed-phase high performance liquid chromatography showed that chlorophyll a (Chl a), chlorophyll b (Chl b), neoxanthin, violaxanthin and siphonaxanthin were involved in LHC 11 from B. corticulans. The properties of electronic transition of monomeric LHC II showed similarities to those of trimeric LHC II. Circular dichroism spectroscopy showed that strong intramolecular interaction of excitonic dipoles between Chl a and between Chl b exist in one LHC II apoprotein, while the intermolecular interaction of these dipoles can be intensified in the trimeric structure. The monomer has high efficient energy transfer from Chl b and siphonaxanthin to Chl a similarly to that of the trimer. Our results suggest that in B. corticulans, LHC II monomer has high ordered pigment organization that play effective physiological function as the trimer, and thus it might be also a functional organization existing in thylakoid membrane of B. corticulans.

Langmuir-Blodgett film of phycobilisomes from blue-green alga Spirulina platensis

The phycobilisomes were isolated from blue-green alga Spirulina platensis, and could form monolayer film at air/water interface. The monolayer film of phycobilisomes was transferred to newly cleaved mica, and coated with gold. Scanning tunneling microscope was used to investigate the structure of the Langmuir-Blodgett film of phycobilisomes. It was shown that phycobilisomes in the monolayer arrayed in rows with core attaching on the substrate surface and rods radiating towards the air phase, this phenomenon was similar to the arrangement of phycobilisomes on cytoplasmic surface of thylakoid membrane in vivo. The possible applications of the Langmuir-Blodgett film of phycobilisomes were also discussed.