Daike Wang

Effects of the interactions between selenium and phosphorus on the growth and selenium accumulation in rice (Oryza sativa).

The solution culture, paddy soil culture and the simulation experiments in the laboratory were conducted to clarify the interactions between selenium and phosphorus, and its effects on the growth and selenium accumulation in rice. Results revealed that a suitable supply of selenium could promote rice growth and excessive selenium could injure rice plant, causing lower biomass, especially in the roots. The supply of selenite could enhance the selenium contents of rice shoots and roots in solution culture and in soil culture. The selenium concentrations in roots were much higher than those in shoots supplied with the same rates of selenium and phosphorus. The interaction between selenium and phosphorus was evident. When the phosphorus supply increased to meet the needs of plant growth, phosphorus could promote absorption and accumulation of selenium in the shoots. If the phosphorus supply was excessive, phosphorus could inhibit the accumulation of selenium in the shoots at the lower selenite level (2 μmol l−1), but could not at the higher selenite level (10 μmol l−1). With the supply of phosphate increased, the selenium concentrations in the roots decreased significantly at both selenite levels. The presence of phosphate could decrease Se sorption on the soil surface and increase the selenium concentration in the soil solution. The concentrations of selenium in shoots and roots supplied with 0.08 g kg−1 phosphorus were lower than those with no phosphorus supplied. With the increase of phosphorus added to 0.4 g kg−1, the selenium concentration in shoots and roots increased. The effect of phosphorus on the concentration was statistically significant at all three selenium levels.

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

Abstract A novel thermally stable terbium carboxylate complex, Tb(MTP),(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),(phen): 1,3,4-oxadizole derivative (PBD)/tris(8-hydroxyquinoline) (AIq 3 )/aluminum (Al) was employed to study the electroluminescent properties of Tb(MTP),(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.

Bright blue electroluminescent devices utilizing poly(N-vinylcarbazole) doped with fluorescent dye

Abstract Bright blue electroluminescent devices have been fabricated using poly( N -vinylcarbazole) (PVK) doped with perylene as the emissive layer, poly( p -phenylenevinylene) (PPV) as the hole-transporting layer, 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD), tris(8-hydroxyquinoline) aluminum (Alq 3 ) as the electron-transporting layer, and Al as the cathode. A luminance of 700 cd/m 2 and a luminescent efficiency of 0.8% are achieved at a drive voltage of 36 V. In the experiment, it is found that the introduction of electron-transporting layer PBD has a great effect on the emissive color of the electroluminescent devices prepared by PVK doped with perylene. Yellow-green emission is observed from the device structure of glass substrate/indium-tin-oxide/PVK:perylene/Al. The possible emissive mechanisms are given. The effect of the transporting layer on the electroluminescence is also discussed.

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-substituted conjugated segment. The negative charge carrier mobility of 6 × 10-11 cm /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 1 × 10-8 eV. The electron trap distribution is exponential, with a characteristic energy of ~ 0.12 eV. A hole trap with energy ~ 0.4 eV was observed. This copolymer is used as emissive material in organic light-emitting diodes that present brightness of ~ 900 dc/m2 at 12.5 V.

Luminescence enhancement by blending PVK with blue PPV copolymer

The PL and EL properties of the polymer blends of PVK and blue PPV copolymer were studied. Considerable enhancement of both the photoluminescent and the electroluminescent intensity were observed by using the polymer blends as emission layer in the LED devices. The energy transfer process and the formation of exciplex in the polymer blends were also discussed.

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

Lasing behavior in DCM-doped PVK microcavity

A surface emitting microcavity was formed by sandwiching a polymer film containing PVK, Alq(3) and DCM between a distributed Bragg reflector (DBR) with a reflectivity of 99% and a silver film (300 nm). The lasing phenomenon was observed in DCM-doped PVK microcavity. The full width at half maximum (FWHM) was 0.6 nm with the peak wavelength at 603 nm. The threshold energy for lasing was estimated to be about 2.5 mu J per pulse

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%

Photoluminescent properties of dye-doped poly(N-vinyleabzole) (PVK) in microcavity

A surface emitting microcavity was formed by sandwiching a polymer film containing poly(N-vinyleabzole) (PVK). 8-hydroxyquinoline aluminium (Alq(3)) and 4-(Dicyanome thylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-Pyran(DCM) between a distributed Bragg reflector (DBR) with a reflectivity of 99% and a silver film. The sample was optically pumped with 250 ps pulses at 2 Hz repetition rate by a 355 nm line of the third harmonic of a mode-lock Nd:YAG laser. The lasing phenomenon was observed in DCM-doped PVK microcavity. The full width at half maximum (FWHM) was 3 nm with the peak wavelength at 602 nm. The threshold energy for lasing was estimated to be about 3 mu J

Synthesis and enhancement of quantum efficiency of a series of novel PPV derivative copolymers

A series of novel PPV derivative copolymers with good solubility in common organic solvents were synthesized. The emitting color of these copolymers could range from red to blue by adjusting the structures and the compositions of monomers. Investigation on their optical properties showed that the PL quantum efficiency could be increased by energy transfer and conjugation reduction. The PL quantum efficiency of most green/blue copolymer films on slide glass was higher than 80%.