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The elemental mercury (Hg0) release characteristics from the Hg-contaminated soil applied with Humic acid fertilizer (HAF) in the greenhouse were identified. The adsorption features of mercuric ion (Hg2+) on HAF under different reaction times and pH were investigated to elucidate the influencing mechanism of HAF on soil Hg0 release. Besides, the microstructure of HAF loading with Hg2+ was characterized by using Fourier transform infrared spectroscopy (FTIR) and scanning electron micrograph-energy dispersive spectrometry-EDS). The results showed that with the increasing HAF dosage, soil oxidation-reduction potential (Eh), and organic matter (SOM) content, as well as the decreasing soil pH, the soil Hg0 release fluxes showed a decreasing tendency. The soil pH, Eh, SOM, and total Hg content are the key factors that can affect the soil Hg0 release fluxes. The interior air temperature, light intensity, soil moisture, and soil temperature have little impact on soil Hg0 release fluxes when the greenhouse soil is applied with HAF. The HAF can immobilize Hg2+ and reduce its activity by surface precipitation and specific adsorption, then affecting the soil Hg0 release fluxes. The results of this study provide a basis for the application of HAF to reduce soil Hg0 release fluxes in the greenhouse of Hg-contaminated areas. [ABSTRACT FROM AUTHOR]

The in-lab incubation experiments were conducted to identify the passivation effect of corn vinasse biochar, which was prepared at different temperatures, on heavy metal Pb in paddy soil of the Pb-Zn mining area. The results showed that after 30 days of biochar amended to the soil, the soil pH and organic carbon content increased by 2.72%-8.47% and 27.79%- 65.26%, respectively. The CO32- and OH- contained in corn vinasse biochar could react with Pb and generate carbonate and hydroxide of Pb. In comparison with the treatment control, the bioavailable fractions of Pb were reduced by 26.6%, 23.30%, 26.95%, and 35.33%, respectively, in biochar-amended treatments. Exchangeable fractions of Pb decreased by 21.50%, 21.33%, 22.58%, and 22.58% for the treatment 3% (300°C), 6% (300°C), 3% (600°C), and 6% (300°C) corn vinasse biochar, respectively, compared with the treatment control. As a whole, corn vinasse biochar could effectively promote the transformation of Pb in soil from the exchangeable fractions into the Fe-Mn oxide-bound fractions and residue fractions, with a significant passivation effect for Pb in soil and more effective passivation by high-temperature preparation and increased dosage of biochar. [ABSTRACT FROM AUTHOR]

Transient electroluminescence (EL) from polymer light emitting diodes is investigated by measurements of the response to short voltage pulses. The carrier mobility is derived from the delay time between the electrical pulse and the onset of EL, μapprox. 3×10[sup -4] cm[sup 2]/V s. Bilayer devices with a polyethylene-dioxythiophene (PEDOT), hole injection layer are also studied. The delay time between the electrical pulse and the onset of EL is independent of the thickness of the injection layer, implying that the conducting PEDOT functions as a part of the electrode. When a dc forward bias is applied to the device, the delay time decreases, probably as a result of the shift of the emission zone towards the anode. The EL turn-on depends on the amplitude of the voltage pulse. The data are modeled by an equivalent circuit with a fixed capacitance connected in parallel with a nonlinear resistance. The solution of the differential equation depends on the exact form of the device’s I–V curve. Two analytical solutions are provided, and an analysis based on space-charge-limited current is presented. By applying a dc forward bias in advance to precharge the space-charge capacitance, the turn-on response time is reduced to 12 ns. The EL decay consists of two components with time constants of 15 ns and 1 μs. The decay does not depend on either the amplitude of the voltage pulse or the prebias. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A biquaternary ammonium salt catalyst, chloride-1,4-dibenzyl-diaza-bi-cyclo [2.2.2] octane peroxotungstate (peroxotungstate biquaternary ammonium salt), was prepared, the structure of which was determined through infrared spectrometry, and was applied in desulfurization of simulated diesel fuel. Under the circumstances in which the close ion-pair of biquaternary ammonium cation and peroxotungstate anion was formed, the mechanism of phase transfer catalysis was offered with analyzing experimental process and data. The desulfurization efficiency reached 99.35% when the reaction temperature was 60°C, the reaction time was 20 min, and the molar ratio of peroxotungstate biquaternary ammonium salt to H2O2 was 0.015. [ABSTRACT FROM PUBLISHER]

A blue organic light-emitting diode employing perylene as light emitting dopant and 9,10-bis(3’5’-diaryl)phenyl anthracene (DPA) as host has been studied for its decay mechanisms. The device structure is ITO(indium tin oxide)/CuPc(copper phthalocyanine)/NPD(α-naphthylphenylbiphenyl diamine)/DPA:perylene/Alq3 (8-hydroxy-quinoline aluminum)/MgAg. In this device, CuPc and NPD are used as hole injection and transporting layers, DPA as a blue host, perylene as a blue emitting dopant, Alq3 as an electron transport layer, MgAg as cathode, respectively. A luminance of 4359 cd/m2 at 15 V and a current efficiency of 3 cd/A at 5 V have been achieved. The breakdown of the interfaces in the device is found to be one of the factors for the decay and the decomposition of the light emitter is not significantly studied by current–voltage–luminance, photoluminescence, and electroluminescence measurements. The lifetime is not intrinsic for this type of device. [ABSTRACT FROM AUTHOR]

Highly efficient light-emitting polymers have become possible by molecular engineering. Photoluminescence (PL) quantum yield above 90% in the solid state is reported for the alternating block copolymer of distyrylbenzene. We conclude that the alternate arrangement of conjugated and nonconjugated segments with surrounding side groups for chromophores effectively confine the excitons for radiative emission. The effectiveness of the exciton confinement is confirmed through the temperature independence of the PL quantum yield. The time-resolved PL decay measurement supports this model through the independence of the PL yield on temperature and emission wavelength. The synthesized copolymers have been employed for the fabrication of electroluminescent (EL) devices, demonstrating high external EL efficiency with low operation threshold. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]