The Roles of Structural Order and Intermolecular Interactions in Determining Ionization Energies and Charge‐Transfer State Energies in Organic Semiconductors

The energy landscape in organic semiconducting materials greatly influences charge and exciton behavior, which are both critical to the operation of organic electronic devices. These energy landscapes can change dramatically depending on the phases of material present, including pure phases of one molecule or polymer and mixed phases exhibiting different degrees of order and composition. In this work, ultraviolet photoelectron spectroscopy measurements of ionization energies (IEs) and external quantum efficiency measurements of charge‐transfer (CT) state energies (E_CT) are applied to molecular photovoltaic material systems to characterize energy landscapes. The results show that IEs and E_CT values are highly dependent on structural order and phase composition. In the sexithiophene:C₆₀ system both the IEs of sexithiophene and C₆₀ shift by over 0.4 eV while E_CT shifts by 0.5 eV depending on molecular composition. By contrast, in the rubrene:C₆₀ system the IE of rubrene and C₆₀ vary by ≤ 0.11 eV and E_CT varies by ≤ 0.04 eV as the material composition varies. These results suggest that energy landscapes can exist whereby the binding energies of the CT states are overcome by energy offsets between charges in CT states in mixed regions and free charges in pure phases.     

论有机肥料在农业生态系统中的地位和作用

人类为了生存,要从自然界取走一些物质和能量,并以不同的形式将物质和能量归还给自然即生态系统。要维持自然生态系统的动态平衡,“取走”和“归还”必须保持永续和相对     

Organic matter transport in an Appalachian Mountain river in Virginia,U.S.A.

Organic material transport in the New River, Virginia, was investigated over a 12 month period. Collections were made using drift nets and grab water samples from bridges at two sites about 210 km apart. About midway between the two sampling sites is a 1920 ha impoundment used for flood control and power generation. Dissolved organic matter (DOM) ranged 1–50 mg l^–1 at Site 1, upstream from the impoundment, and 11–19 mg l^–1 at Site 2 and was the most abundant form of organic matter at both sites during most periods of the year. Fine particulate organic matter (FPOM) ranged 1–45 mg l^–1 at Site 1 and 1–9 mg l^–1 at Site 2. Concentration of coarse particulate organic matter (CPOM) ranged 0.1–0.7 mg l^–1 at Site 1 and 0.1–0.2 mg l^–1 at Site 2. On an annual basis, the organic matter loads at Site 1 and Site 2 were computed to be 67 000 and 76 800 T y^–1, respectively, suggesting that the impoundment trapped and processed POM, and that municipal and industrial treatment facilities between the study sites supplemented DOM in the river.     

A CFF 91-based Continuum Solvation Model: Solvation Free Energies of Small Organic Molecules and Conformations of the Alanine Dipeptide in Solution

Abstract

For molecular mechanics simulations of solvated molecules, it is important to use a consistent approach for calculating both the force field energy and the solvation free energy. A continuum solvation model based upon the atomic charges provided with the CFF91 force field is derived. The electrostatic component of the solvation free energy is described by the Poisson-Bolzmann equation while the nonpolar comonent of the solvation energy is assumed to be proportional to the solvent accessible surface area of the solute. Solute atomic radii used to describe the interface between the solute and solvent are fitted to reproduce the energies of small organic molecules. Data for 140 compounds are presented and compared to experiment and to the results from the well-characterized quantum mechanical solvation model AM1-SM2. In particular, accurate results are obtained for amino acid neutral analogues (mean unsigned error of 0.3 kcal/mol). The conformational energetics of the solvated alanine dipeptide is discussed.     

Relating Frontier Orbital Energies from Voltammetry and Photoelectron Spectroscopy to the Open‐Circuit Voltage of Organic Solar Cells

For 19 diketopyrrolopyrrole polymers, the highest occupied molecular orbital (HOMO) energies are determined from i) the oxidation potential with square‐wave voltammetry (SWV), ii) the ionization potential using ultraviolet photoelectron spectroscopy (UPS), and iii) density functional theory (DFT) calculations. The SWV HOMO energies show an excellent linear correlation with the open‐circuit voltage (V_oc) of optimized solar cells in which the polymers form blends with a fullerene acceptor ([6,6]‐phenyl‐C₆₁‐butyl acid methyl ester or [6,6]‐phenyl‐C₇₁‐butyl acid methyl ester). Remarkably, the slope of the best linear fit is 0.75 ± 0.04, i.e., significantly less than unity. A weaker correlation with V_oc is found for the HOMO energies obtained from UPS and DFT. Within the experimental error, the SWV and UPS data are correlated with a slope close to unity. The results show that electrochemically determined oxidation potentials provide an excellent method for predicting the V_oc of bulk heterojunction solar cells, with absolute deviations less than 0.1 V.     

1997-2006年中国城市建成区有机碳储量的估算

随着城市区域碳排放的增加,城市碳循环在全球碳循环中的地位越来越重要,而城市碳排放和碳储量的估算是城市碳循环研究的基础.本研究利用统计资料,参考国内外相关研究成果,对1997-2006年中国城市建成区有机碳储量进行估算.结果表明： 1997-2006年,中国城市建成区总有机碳储量呈上升趋势,由0.13～0.19 Pg C（平均值为0.16 Pg C）增加到0.28～0.41 Pg C（平均值为0.34 Pg C）;建成区有机碳密度由9.86～14.03 kg C·m^-2（平均值为11.95 kg C·m^-2）增加到10.54～15.54 kg C·m^-2（平均值为13.04 kg C·m^-2）.建成区的有机碳主要储存在土壤中,其次是建筑物和绿地,居民有机体的碳储量可忽略不计.1997和2006年,土壤、建筑物、绿地和居民有机体在总碳库中的比例分别为78%、12%、9%、1%和73%、16%、10%、1%.     

土壤有机质和外源有机物对甲烷产生的影响

对土壤有机质含量及组分、外源有机物和根系分泌对甲烷产生的影响作了综述。土壤产甲烷量和甲烷排放量随有机质含量增加而提高,与土壤中易矿化有机碳或沸水浸提有机碳含量呈显著相关。外源有机碳加入促进了土壤排放甲,刺激效果与外源有机碳的用量和组成有关。还原力强的有机物如纤维素和半纤维素较还原力弱的有机物如类脂和多糖能够产生更多的甲烷。甲醇、甲基化氨基酸等无其它微生物竞争利用的有机物能被产甲烷菌更多地转化成甲烷。植物根系分泌物也促进甲烷的产生,促进作用大小与植物种类及分泌物的数量和质量有关。外源有机物通过3种方式促进土壤甲烷产生;提高土壤的甲烷底物供应量,降低土壤氧化还原电位,刺激土壤原有有机碳的转化。     

土壤活性有机碳的表征及其生态效应

土壤活性有机碳指在一定的时空条件下,受植物、微生物影响强烈、具有一定溶解性、在土壤中移动比较快、不稳定、易氧化、分解、易矿化,其形态,空间位置对植物、微生物来说活性比较高的那一部分土壤碳素。国外描述这一部分碳素的术语为有效碳、水溶性碳、易氧化碳、可矿...     

有机肥和无机肥对稻田养分循环的影响

一、引言研究养分在农田生态系统中的循环,是农业生态学的重要内容之一。对有机肥和无机肥肥效及其对农作物产量的影响曾有过不少研究。虽然大量研究表明有机肥对水稻产量的作用与化肥一样有效,甚至更好,也有许多试验,尤其是一些长期对比试验表明有机肥对作物产量的作用不及化肥,只是使用有机肥的试验小区有很长的残效,连续使用20年家畜肥的小区停肥40年后,大麦产量仍为对照化肥小     

沈阳西部污灌水中有机污染物的分析

沈阳西部污灌水中有机污染物的分析刘海玲,张丽珊,姚家彪,于殿臣,朱岩,可夫,姜萍（中国科学院沈阳应用生态研究所,１１００１５）ＡｎａｌｙｓｉｓｏｆＯｒｇａｎｉｃＰｏｌｌｕｔａｎｔｓｉｎＩｒｒｉｇａｔｅｄｓｅｗａｇｅＩｎＷｅｓｔｅｒｎＳｈｅｎｙａｎｇ．...     

Chemical Characteristics and Origin of Dissolved Organic Matter in the Yukon River

Monthly (or bi-weekly) water samples were collected from the Yukon River, one of the largest rivers in North America, at a station near the US Geological Survey Stevens Village hydrological station, Alaska from May to September 2002, to examine the quantity and quality of dissolved organic matter (DOM) and its seasonal variations. DOM was further size fractionated into high molecular weight (HMW or colloidal, 1 kDa–0.45 μm) and low molecular weight (LMW, <1 kDa) fractions. Dissolved organic carbon (DOC), colored dissolved organic matter (C-DOM) and total dissolved carbohydrate (TCHO) species were measured in the size fractionated DOM samples. Concentrations of DOC were as high as 2830 μmol-C l⁻¹ during the spring breakup in May and decreased significantly to 508–558 μmol-C l⁻¹ during open-water season (June–September). Within the DOC pool, up to 85% was in the colloidal fraction (1 kDa–0.45 μm) in early May. As DOC concentration decreased, this colloidal portion remained high (70–85% of the bulk DOC) throughout the sampling season. Concentrations of TCHO, including monosaccharides (MCHO) and polysaccharides (PCHO), varied from 722 μmol-C l⁻¹ in May to 129 μmol-C l⁻¹ in September, which comprised a fairly constant portion of bulk DOC (24±2%). Within the TCHO pool, the MCHO/TCHO ratio consistently increased from May to September. The C-DOM/DOM ratio and the size fractionated DOM increased from May to September, indicating that DOM draining into the Yukon River contained increased amounts of humified materials, likely related to a greater soil leaching efficiency in summer. The average composition of DOM was 76% pedogenic humic matter and 24% aquagenic CHO. Characteristics of soil-derived humic substances and low chlorophyll-a concentrations support a dominance of terrestrial DOM in Yukon River waters.     

Organic carbon dynamics in two regulated rivers in northwestern Montana,USA

We studied the transport of particulate organic carbon (POC) and dissolved organic carbon (DOC) in two regulated rivers during minimum and increasing discharges. Mean annual concentrations of total POC, measured monthly during conditions of minimum discharge from the dams, were twice as high at a station below a dam with a selective withdrawal system on the Kootenai River (KR, 0.15 mg 1^–1), as at station below a dam with hypolimnetic water releases on the Flathead River (FR, 0.07 mg 1^–1). Annual mean concentrations of DOC were similar below both dams (1.62 mg 1^–1 FR; 1.71 KR). The percentage of POC in four size fractions differed in regulated and unregulated reaches of each river system; the smallest size fraction (0.45–10 smm) constituted a larger percentage of the total POC at the stations below the dams (50–93%), because POC in large size classes had settled out in the reservoir. The three largest size fractions (10–1000 µm) comprised a larger percentage of the total POC when samples were taken during conditions of full discharge from the dam. We measured large increases in all size classes of POC in samples collected during increasing discharges in a regulated reach, reflecting the component of sloughed periphyton and resuspended organic matter that were added during periods of hydropower generation at the dam. Seston (355 µm to 1 cm) collected in nets increased dramatically during increasing flows; concentrations of particulate organic matter (POM) in samples collected two and three hours after water levels began to rise were 572 and 1440 times higher than those collected during minimum discharge at the dam.     

玉米根冠粘胶和铝的结合及有机酸累积

玉米根系分泌较多的植物粘胶 ,用 0 .0 1%中性红溶液使粘胶染成红色。 30 μmol/L的AlCl3 处理根系 1h后 ,不除去粘胶的根尖的铝含量大于除去粘胶的根尖的铝含量。粘胶的铝含量随着处理的铝浓度的增加而增加。用高效液相色谱仪能使粘胶 铝复合物分离成均含糖和铝的两种组分。 5 μmol/L的AlCl3 处理根系 2 4h后 ,粘胶中积累了铝诱导分泌的有机酸。粘胶中含有酸性磷酸酶 ,它的活性随着处理的铝浓度的增加而降低。这些结果证明了植物粘胶能够和铝结合、粘胶液滴能够积累有机酸及磷酸酶的假说     

永春县柑橘林生态系统的碳储量及其动态变化

通过野外实地调查对永春县天马山柑橘林生态系统碳储量及分布特点进行研究。结果表明:柑橘的树高和基径的相关系数为0.8933。柑橘各器官生物量回归模型显示,柑橘各器官的生物量与其树高和基径的相关性较好,其中树干、树叶、果实器官的相关系数均大于0.90。柑橘林生态系统有机碳密度为222.796t.hm-2,其中土壤(0-100cm)碳密度为200.214t.hm-2,占总有机碳密度的89.864%,果树碳密度为22.582t.hm-2,占10.136%。1952-2007年,永春县柑橘林生态系统碳储量从445.592t增加到2.205×106t,表现为碳汇。     

Nongeminate Recombination in Planar and Bulk Heterojunction Organic Solar Cells

Nongeminate recombination in organic solar cells based on copper phthalocyanine (CuPc) and C₆₀ is investigated. Two device architectures, the planar heterojunction (PHJ) and the bulk heterojunction (BHJ), are directly compared in view of differences in charge carrier decay dynamics. A combination of transient photovoltage (TPV) experiments, yielding the small perturbation charge carrier lifetime, and charge extraction measurements, providing the charge carrier density is applied. In organic solar cells, charge photogeneration and recombination primarily occur at the donor–acceptor heterointerface. Whereas the BHJ can often be approximated by an effective medium due to rather small scale phase separation, the PHJ has a well defined two‐dimensional heterointerface. In order to study nongeminate recombination dynamics in PHJ devices the charge accumulation at this interface is most relavent. As only the spatially averaged carrier concentration can be determined from extraction techniques, the charge carrier density at the interface n_int is derived from the open circuit voltage. Comparing the experimental results with macroscopic device simulation, the differences of recombination and charge carrier densities in CuPc:C₆₀ PHJ and BHJ devices are discussed with respect to the device performance. The open circuit voltage of BHJ is larger than for PHJ at low light intensities, but at 0.3 sun the situation is reversed: here, the PHJ can finally take advantage of its generally longer charge carrier lifetimes, as the active recombination region is smaller.     

Seasonal Variability of Particulate Organic Matter in a Mountain Stream in Central Spain

The aim of this paper was to study the influence of environmental characteristics of the Mediterranean climate on seasonal variability of particulate organic matter abundance in a mountain stream. Coarse and fine fractions of both suspended and benthic particulate organic matter were determined on 14 occasions between February 1998 and November 1999 in a second‐order Mediterranean stream in Central Spain (Arroyo Mediano). Temporal variability of suspended organic matter followed a seasonal pattern, attributed to litter‐fall inputs, instream processing, and the hydrological regime. Suspended organic matter (SOM) and its seasonal variability fall well within the range reported for streams in temperate non‐Mediterranean deciduous forest. However, we found no seasonal trend in benthic organic matter (BOM) storage, and it seems that the amount of BOM remained fairly constant throughout the year. Reach retention (evaluated as the ratio between BOM and SOM per m²) was higher in summer during reduced stream flow, mainly due to coarse particulate organic matter storage. These observations do not differ from those reported for other headwater streams in temperate forested biomes, from which we conclude that there was no evidence of a Mediterranean influence on particulate organic matter dynamics in the Mediano stream, nor probably in other headwater Mediterranean streams. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

酪氨酸酶在有机介质中的酶活性

研究了蘑菇酪氨酸酶在有机溶剂中催化邻苯二酚向邻苯醌的转化反应,结果表明酪氨酸酶在有机介质中能保持较高的活性,其活性主要受体系中的水活度控制.在适当控制酶分子上结合水的条件下,酶活性随温度升高而增大.无机盐的水合物可用于控制这种低水有机介质中的水活度.