The white organic light emitting device (OLED) with single-structure using a polymer blend as the light emitting layer is fabricated.Heat treatment is used to control the ratio between the intensities of main electrol...The white organic light emitting device (OLED) with single-structure using a polymer blend as the light emitting layer is fabricated.Heat treatment is used to control the ratio between the intensities of main electroluminescent spectral peaks.The electroluminescent spectrum of our device is quite similar to that of white inorganic LED produced by Nichia Corporation after being annealed,and its turn-on voltage can be decreased by 1 V.展开更多
Two alkyl substituted polythiophene derivatives: poly(3-hexylthiophene)(P3HT) and poly(3-decylthiophene)(P3DT), have synthesized by oxidation coupling polymerization of 3-alkylthiophene using iron(III) chloride as cat...Two alkyl substituted polythiophene derivatives: poly(3-hexylthiophene)(P3HT) and poly(3-decylthiophene)(P3DT), have synthesized by oxidation coupling polymerization of 3-alkylthiophene using iron(III) chloride as catalyst in chloroform. While both polymers in pure chloroform solution have maximum absorption at approximately same wavelength of 440nm, they behave differently with respect to changes observed on their UV-visible and photoluminescence spectra when the quality of the poor solvent is changed in good solvent (chloroform) / poor solvent (methanol) mixtures. With increasing volume fraction of methanol in mixtures, the absorption spectra of P3HT and P3DT red-shift, peaking at maximum wavelength of 495nm (P3HT) and 510nm(P3DT). Furthermore, the absorption spectra of the two polymers in chloroform blue-shift as the temperature rises. P3HT shows 4.73nm blue-shifts at 50℃ in contrast to the case at 20℃, while P3DT blue-shifts about 5.04nm. The photoluminescence spectra of the two polymers in mixed solution are also investigated, which show that the luminescence spectra shift to longer wavelength with an accompanying drop in the PL intensity as methanol is increased. The absorption and emission spectra of the two polymers in a poor solvent and a thin film are similar, which indicate that a similar longer conjugation length in the two cases. It could conclude that the polymers exist almost the same conformations and aggregations in both a poor solvent and a thin film. P3DT exhibits more sensitive spectra properties (big red-shifts in both absorption and luminescence spectra in poor solvents and large blue-shifts at high temperature) with contrast to P3HT, which imply that long side alkyl may improve the chromic properties of the polymer.展开更多
Cadmium （Cd） concentrations in the water extracts of ten contaminated soils by arsenic （As） with various iron （Fe） contents were measured using inductively coupled plasma atomic emission spectrometry （ICP-AES）...Cadmium （Cd） concentrations in the water extracts of ten contaminated soils by arsenic （As） with various iron （Fe） contents were measured using inductively coupled plasma atomic emission spectrometry （ICP-AES） and electrothermal atomic absorption spectrometry （ETAAS）, Due to the potential spectral interferences of As and Fe in the quantification of Cd, two methods were used for the background compensation. The first method was based on the use of a deuterium lamp （BGCD2 mode）. The second one required a Cd hollow cathode lamp pulsated with a current for which the intensity varies in the course of time （BGCSR mode）. The results showed that the choices of the analytical technique and the method used for the background compensation depend on the Cd, As and Fe concentrations in the solution and the concentration ratios As/Cd or/and Fe/Cd. In comparison with the ICP-AES and the ETAAS in combination with the BGCD2 mode, it was shown that the high-speed self-reversal method （HSSR） was a more appropriate method to correct As and Fe spectral interferences during the Cd measurements. On the other hand, depending on the Cd concentration, it was established that no significant Fe interference occurred during the Cd determination even if Fe concentration was 50 mg/L, reflecting the efficiency of the HSSR method to overcome the Fe interferences in the determination of Cd concentration by ETAAS without any matrix modifier in water extracts.展开更多
Geothermal power plants are receiving increasing attention as regards the mobilization of mercury （Hg） to the environment. Hg is a trace element that may be present in the geothermal fluid, but due to its volatility...Geothermal power plants are receiving increasing attention as regards the mobilization of mercury （Hg） to the environment. Hg is a trace element that may be present in the geothermal fluid, but due to its volatility, it is transferred mainly into the vapor phase. Hence, it may be mostly discharged to the atmosphere with the non-condensable gases. Olkaria geothermal field hosts 3 geothermal power plants. In this area Hg deposition fluxes have not been studied. Concentrations and wet deposition fluxes of total mercury （T-Hg） were determined from April 2009 to May 2010 at 2 sites in this field. Event-based precipitation samples were collected using fabricated bulk precipitation samplers. Samples were treated according to trace metal protocol and analyzed by cold vapor atomic fluorescence spectrometry （CVAFS）. This paper thus reports the first ever determination of T-Hg concentrations and fluxes in precipitation. The T-Hg concentration in samples ranged from 0.002-0.0602 μg/L at the two sites, however, the volume-weighted mean concentration and wet deposition flux were 0.01974 and 0.02884μg.L^-1 and 0.0167-1.45 μg.m2 during the study period. The annual volume-weighted mean wet deposition fluxes of T-Hg for 2 sites were 13.74 and 19.83 μg.m-2.yr-1 with an average flux of 16.785μg.m-2.yr-1. Hg concentrations and the Hg fluxes in precipitation showed seasonal trends being lowest in the short-rains and highest in the long rains. The concentrations of T-Hg for the 2 sites is negatively correlated with the precipitation depth （r2 = 0.26 ＆ r2 = 0.0065）, suggesting that scavenging of particle-bound mercury from the atmosphere is an important mechanism contributing to mercury in rainwater. Mean Hg concentrations in precipitation at the study sites were comparable to the ranges reported for Canada and the USA by the Mercury Deposition Network （MDN）.展开更多
Yellow light-emitting diodes(LEDs) are widely utilized in high-quality lighting, light communication,indicator lamps, etc. Owing to their outstanding material properties and device performance, the metal halide perovs...Yellow light-emitting diodes(LEDs) are widely utilized in high-quality lighting, light communication,indicator lamps, etc. Owing to their outstanding material properties and device performance, the metal halide perovskites have demonstrated a significant potential for LED applications. However, the performance of the yellow perovskite LEDs(PeLEDs) is inferior to that of their green and red counterparts, with the maximum external quantum efficiency(EQE) limited to ~3.1%. Further, a majority of the yellow PeLEDs are fabricated using the spin-coating methods. The current study reports the development of the yellow CsPbBr_(2)I PeLEDs based on an all-vacuum deposition approach, which has been widely employed in the commercial organic LEDs(OLEDs). By controlling the co-evaporation rate of CsI and PbBr;, the growth kinetics of the perovskite layer are regulated to achieve a small grain size of~31.8 nm. Consequently, an improved radiative recombination rate(8.04 × 10^(-9)cm^(3)/s) is obtained owing to the spatial confinement effect. The PeLEDs based on the optimal perovskite film demonstrate the yellow electroluminescence(574 nm) with a maximum EQE of ~3.7% and luminance of~16,200 cd/m^(2), thus, representing one of the most efficient and bright yellow PeLEDs. Overall, this study provides a useful guideline for realizing the efficient PeLEDs based on the thermal evaporation strategy and highlights the potential of PeLED as an efficient and bright yellow light source.展开更多
文摘The white organic light emitting device (OLED) with single-structure using a polymer blend as the light emitting layer is fabricated.Heat treatment is used to control the ratio between the intensities of main electroluminescent spectral peaks.The electroluminescent spectrum of our device is quite similar to that of white inorganic LED produced by Nichia Corporation after being annealed,and its turn-on voltage can be decreased by 1 V.
基金National Natural Science Foundation of China (60277002)
文摘Two alkyl substituted polythiophene derivatives: poly(3-hexylthiophene)(P3HT) and poly(3-decylthiophene)(P3DT), have synthesized by oxidation coupling polymerization of 3-alkylthiophene using iron(III) chloride as catalyst in chloroform. While both polymers in pure chloroform solution have maximum absorption at approximately same wavelength of 440nm, they behave differently with respect to changes observed on their UV-visible and photoluminescence spectra when the quality of the poor solvent is changed in good solvent (chloroform) / poor solvent (methanol) mixtures. With increasing volume fraction of methanol in mixtures, the absorption spectra of P3HT and P3DT red-shift, peaking at maximum wavelength of 495nm (P3HT) and 510nm(P3DT). Furthermore, the absorption spectra of the two polymers in chloroform blue-shift as the temperature rises. P3HT shows 4.73nm blue-shifts at 50℃ in contrast to the case at 20℃, while P3DT blue-shifts about 5.04nm. The photoluminescence spectra of the two polymers in mixed solution are also investigated, which show that the luminescence spectra shift to longer wavelength with an accompanying drop in the PL intensity as methanol is increased. The absorption and emission spectra of the two polymers in a poor solvent and a thin film are similar, which indicate that a similar longer conjugation length in the two cases. It could conclude that the polymers exist almost the same conformations and aggregations in both a poor solvent and a thin film. P3DT exhibits more sensitive spectra properties (big red-shifts in both absorption and luminescence spectra in poor solvents and large blue-shifts at high temperature) with contrast to P3HT, which imply that long side alkyl may improve the chromic properties of the polymer.
文摘Cadmium （Cd） concentrations in the water extracts of ten contaminated soils by arsenic （As） with various iron （Fe） contents were measured using inductively coupled plasma atomic emission spectrometry （ICP-AES） and electrothermal atomic absorption spectrometry （ETAAS）, Due to the potential spectral interferences of As and Fe in the quantification of Cd, two methods were used for the background compensation. The first method was based on the use of a deuterium lamp （BGCD2 mode）. The second one required a Cd hollow cathode lamp pulsated with a current for which the intensity varies in the course of time （BGCSR mode）. The results showed that the choices of the analytical technique and the method used for the background compensation depend on the Cd, As and Fe concentrations in the solution and the concentration ratios As/Cd or/and Fe/Cd. In comparison with the ICP-AES and the ETAAS in combination with the BGCD2 mode, it was shown that the high-speed self-reversal method （HSSR） was a more appropriate method to correct As and Fe spectral interferences during the Cd measurements. On the other hand, depending on the Cd concentration, it was established that no significant Fe interference occurred during the Cd determination even if Fe concentration was 50 mg/L, reflecting the efficiency of the HSSR method to overcome the Fe interferences in the determination of Cd concentration by ETAAS without any matrix modifier in water extracts.
文摘Geothermal power plants are receiving increasing attention as regards the mobilization of mercury （Hg） to the environment. Hg is a trace element that may be present in the geothermal fluid, but due to its volatility, it is transferred mainly into the vapor phase. Hence, it may be mostly discharged to the atmosphere with the non-condensable gases. Olkaria geothermal field hosts 3 geothermal power plants. In this area Hg deposition fluxes have not been studied. Concentrations and wet deposition fluxes of total mercury （T-Hg） were determined from April 2009 to May 2010 at 2 sites in this field. Event-based precipitation samples were collected using fabricated bulk precipitation samplers. Samples were treated according to trace metal protocol and analyzed by cold vapor atomic fluorescence spectrometry （CVAFS）. This paper thus reports the first ever determination of T-Hg concentrations and fluxes in precipitation. The T-Hg concentration in samples ranged from 0.002-0.0602 μg/L at the two sites, however, the volume-weighted mean concentration and wet deposition flux were 0.01974 and 0.02884μg.L^-1 and 0.0167-1.45 μg.m2 during the study period. The annual volume-weighted mean wet deposition fluxes of T-Hg for 2 sites were 13.74 and 19.83 μg.m-2.yr-1 with an average flux of 16.785μg.m-2.yr-1. Hg concentrations and the Hg fluxes in precipitation showed seasonal trends being lowest in the short-rains and highest in the long rains. The concentrations of T-Hg for the 2 sites is negatively correlated with the precipitation depth （r2 = 0.26 ＆ r2 = 0.0065）, suggesting that scavenging of particle-bound mercury from the atmosphere is an important mechanism contributing to mercury in rainwater. Mean Hg concentrations in precipitation at the study sites were comparable to the ranges reported for Canada and the USA by the Mercury Deposition Network （MDN）.
基金supported by the National Natural Science Foundation of China(62050039 61725401 5171101030 51761145048 62004075 62005089 and 51902113)the National Key R&D Program of China(2016YFA0204000 and 2016YFB0201204)+2 种基金the Fundamental Research Funds for the Central Universities(HUST: 2019421JYCXJJ004)the Fund for Innovative Research Groups of the Natural Science Foundation of Hubei Province(2020CFA034)the Graduates’ Innovation Fund of Huazhong University of Science and Technology(HUST)(2021yjscxcy036)。
文摘Yellow light-emitting diodes(LEDs) are widely utilized in high-quality lighting, light communication,indicator lamps, etc. Owing to their outstanding material properties and device performance, the metal halide perovskites have demonstrated a significant potential for LED applications. However, the performance of the yellow perovskite LEDs(PeLEDs) is inferior to that of their green and red counterparts, with the maximum external quantum efficiency(EQE) limited to ~3.1%. Further, a majority of the yellow PeLEDs are fabricated using the spin-coating methods. The current study reports the development of the yellow CsPbBr_(2)I PeLEDs based on an all-vacuum deposition approach, which has been widely employed in the commercial organic LEDs(OLEDs). By controlling the co-evaporation rate of CsI and PbBr;, the growth kinetics of the perovskite layer are regulated to achieve a small grain size of~31.8 nm. Consequently, an improved radiative recombination rate(8.04 × 10^(-9)cm^(3)/s) is obtained owing to the spatial confinement effect. The PeLEDs based on the optimal perovskite film demonstrate the yellow electroluminescence(574 nm) with a maximum EQE of ~3.7% and luminance of~16,200 cd/m^(2), thus, representing one of the most efficient and bright yellow PeLEDs. Overall, this study provides a useful guideline for realizing the efficient PeLEDs based on the thermal evaporation strategy and highlights the potential of PeLED as an efficient and bright yellow light source.
