Atomic-scale surface science phenomena studied by scanning tunneling microscopy

Following the development of the scanning tunneling microscope (STM), the technique has become a very powerful and important tool for the field of surface science, since it provides direct real-space imaging of single atoms, molecules and adsorbate structures on surfaces. From a fundamental perspective, the STM has changed many basic conceptions about surfaces, and paved the way for a markedly better understanding of atomic-scale phenomena on surfaces, in particular in elucidating the importance of local bonding geometries, defects and resolving non-periodic structures and complex co-existing phases. The so-called “surface science approach”, where a complex system is reduced to its basic components and studied under well-controlled conditions, has been used successfully in combination with STM to study various fundamental phenomena relevant to the properties of surfaces in technological applications such as heterogeneous catalysis, tribology, sensors or medical implants. In this tribute edition to Gerhard Ertl, we highlight a few examples from the STM group at the University of Aarhus, where STM studies have revealed the unique role of surface defects for the stability and dispersion of Au nanoclusters on TiO₂, the nature of the catalytically active edge sites on MoS₂ nanoclusters and the catalytic properties of Au/Ni or Ag/Ni surfaces. Finally, we briefly review how reaction between complex organic molecules can be used to device new methods for self-organisation of molecular surface structures joined by comparatively strong covalent bonds.     

二维配位聚合物[Cd(bix)2Cl2]n的合成、晶体结构与荧光性能研究

利用金属离子和多功能的有机配体的自组装过程构筑得到的金属-有机配位聚合物,由于具有丰富的拓扑结构及其在分子与离子交换、吸附、选择性催化、光电子、磁学性能、孔洞材料、非线性光学等领域具有潜在的应用价值而成为众多科学家研究的热点领域[1～10].文献已经报道了大量具有新型拓扑结构的化合物,如一维链状、梯形、铁轨型:二维正方形或长方形格子、双层结构、砖墙结构和蜂窝状结构:三维八面体和类八面体结构、金刚石结构等.     

半透射高光谱结合流形学习算法同时识别马铃薯内外部缺陷多项指标

针对马铃薯内外部缺陷多项指标难以同时识别的问题,提出了一种半透射高光谱成像技术采用流形学习降维算法与最小二乘支持向量机(LSSVM)相结合的方法,该方法可同时识别马铃薯内外部缺陷的多项指标。试验以315个马铃薯样本为研究对象,分别采集合格、外部缺陷(发芽和绿皮)和内部缺陷(空心)马铃薯样本的半透射高光谱图像,同时为了符合生产实际,将外部缺陷马铃薯的缺陷部位以正对、侧对和背对采集探头的随机放置方式进行高光谱图像采集。提取马铃薯样本高光谱图像的平均光谱(390~1 040 nm)进行光谱预处理,然后分别采用有监督局部线性嵌入(SLLE)、局部线性嵌入(LLE)和等距映射(Isomap)三种流形学习算法对预处理光谱进行降维,并分别建立基于纠错输出编码的最小二乘支持向量机(ECOC-LSSVM)多分类模型。通过分析和比较建模结果,确定SLLE为最优降维算法,SLLE-LSSVM为最优马铃薯内外部缺陷识别模型,该方法对测试集合格、发芽、绿皮和空心马铃薯样本的识别率分别达到96.83%,86.96%,86.96%和95%,混合识别率达到93.02%。试验结果表明：基于半透射高光谱成像技术结合SLLE-LSSVM的定性分析方法能够同时识别马铃薯内外部缺陷的多项指标,为马铃薯内外部缺陷的快速在线无损检测提供了技术参考。     

低成本富勒烯衍生物电子传输层在钙钛矿太阳能电池的应用

Organic-inorganic hybrid perovskite solar cells (PSCs) have attracted significant attention owing to their high absorption coefficient and ambipolar charge transport properties. With only several years of development, the power conversion efficiency (PCE) has increased from 3.8% to 22.7%. In general, PSCs have two types of structural architecture: mesoporous and planar. The latter possesses higher potential for commercialization due to its simpler structure and fabrication process, especially the inverted planar structure, which possesses negligible hysteresis. In an inverted PSC, the electron transport materials (ETM) are deposited on a perovskite film. Only a few ETMs can be used for inverted PSCs as the perovskite film is easily damaged by the solvent used to dissolve the ETM. Furthermore, the energy levels of the ETM should be well aligned with that of the perovskites. Normally it is difficult to use inorganic ETMs as they require high temperatures for the annealing process to improve the electron conductivity; the perovskite film cannot sustain these high temperatures. To date, the fullerene derivative, [6, 6]-phenyl-C61-butyric acid methyl ester (PCBM), is the most commonly used organic ETM for high efficiency inverted planar PSCs. However, the high manufacturing cost due to its complex synthesis retards the industrialization of the PSCs. Here, we introduce a fullerene pyrrolidine derivative, N-methyl-2-pentyl-[60]fullerene pyrrolidine (NMPFP), synthesized via the Prato reaction of C₆₀ directly with cheap hexanal and sarcosine. Then the NMPFP electron transport layer (ETL) was prepared by a simple solution process. The properties of the resulting NMPFP ETLs were characterized using UV-Vis absorption spectroscopy, cyclic voltammetry measurements, atomic force microscopy, and conductivity test. From the results of the UV-Vis absorption spectroscopy and cyclic voltammetry measurements, the LUMO level of NMPFP ETL was calculated to be 0.2 eV higher than that of the PCBM ETL. This contributes to a higher open-circuit photovoltage. In addition, the NMPFP film presented higher conductivity than the PCBM film. Thus, the photo-generated charge carriers in the perovskite films should be transported more efficiently to the NMPFP electron transport layer (ETL) than to the PCBM ETL. This was confirmed by the results of the steady-state photoluminescence spectroscopy. Finally, the NMPFP as an alternative low-cost ETL was employed in an inverted planar PSC to evaluate the device performance. The device made with the NMPFP ETL yielded an efficiency of 13.83% with negligible hysteresis, which is comparable to the PCBM counterpart devices. Moreover, since stability is another important parameter retarding the commercialization of PSCs, the stability of the PCBM and NMPFP base PSCs were investigated and compared. It was found that the NMPFP devices possessed significantly improved stability due to the higher hydrophobicity of the NMPFP. In conclusion, this research demonstrates that NMPFP is a promising ETL to replace PCBM for the industrialization of cheap, efficient and stable inverted planar PSCs.     

Brennstoffzellentechnik

More than 150 years ago Sir Groe invented the fuel cell. Material problems prohibited this type of gassupplied battery to go to market for a very long time. A break-through was achieved during the last 30 years so that today we can distinguish two low-temperature fuel cell technologies (phosphoric acid and membrane cells) from two high-temperature technologies (molten carbonate and oxide ceramic cells) with a working temperature of 650 and 80 to 900°C, respectively. But today only phosphoric acid fuel cells are offered commeriall as containerized 200-kW cogeneration power plants. Membrane cells are most suitable for electrotraction of aumobiles offering a remarkbly low weight per unit power and working with zero emission. The fuel is, however, a particular problem as hydrogen is not easy to store and too expensive. The ultimate goal is supplying the car with methanol and combusing methanol directly in the fuel cell. However, this aim might be only achieved after several more years of intensive research and development.     

A Sensitive LC-MS/MS Method for the Simultaneous Determination of Two Thia-Analogous Indirubin N-Glycosides and Indirubin-3′-Monoxime in Plasma and Cell Culture Medium

Indirubin was identified as an active component of Danggui Longhui Wan, an herbal mixture used in traditional Chinese medicine, and showed anticancer activity in clinical trials in patients with chronic leukemia. Investigations on the mechanisms of antitumor action of indirubins have mainly focused on the indirubin derivative indirubin-3′-monoxime (I3M). Meanwhile, antiproliferative and cytotoxic properties on cancer cells have also been demonstrated for several synthetic indirubin N-glycosides. In the present study, we demonstrate cytotoxic activity of the thia-analogous indirubin N-glycosides KD87 (3-[3′-oxo-benzo[b]thiophen-2′-(Z)-ylidene]-1-(β-d-glucopyranosyl)-oxindole) and KD85 (3-[3′-oxo-benzo[b]thiophen-2′-(Z)-ylidene]-1-(β-d-mannopyranosyl)-oxindole) against melanoma and squamous cell carcinoma cells as well as lung cancer and glioblastoma cells. The advanced state of preclinical studies on the effects of indirubins conducted to date underscores the need for pharmacokinetic data from cellular, animal, and human studies for which reliable quantification is required. Therefore, a sensitive liquid chromatography-tandem mass spectrometric (LC-MS/MS) method was developed and validated for the simultaneous measurement of KD87, KD85, and I3M in plasma and cell culture medium. Experimental conditions for sample preparation were optimized for human plasma protein precipitation and liquid-liquid extraction from plasma and cell culture medium. The methods were successfully validated in accordance with the U.S. Food and Drug Administration Bioanalytical Method Validation and evaluated for selectivity, sensitivity, matrix effect, recovery, carryover, calibration curve linearity, accuracy, precision, and stability. The applicability of the methods was demonstrated by the determination of KD87 in mouse plasma after prior intraperitoneal administration to mice.     

Desulfurization of Morupule Coal with Subcritical Aqueous Ethanol Extraction

Coal combustion greatly contributes to global emissions of toxic gases into the atmosphere, with sulfur emissions as one of the prominent pollutants in addition to carbon dioxide. Nevertheless, Botswana utilizes Morupule''s sub‐bituminous coal with average sulfur and ash contents, as determined in this study being 1.9 and 24.4 % by weight with an average calorific value of 22 MJ Kg⁻¹ to generate electricity. We report an optimized extraction method for reducing total sulfur in Morupule coal from 1.9±0.2 to 0.43±0.02 wt.% at optimum conditions of ethanol/water (90/10, v/v %) at 129 °C (105 bars) in 10 minutes. A Box–Behnken experimental design was employed to select the optimal conditions of temperature (100–180 °C), water proportion in ethanol (10–90, v/v %) and extraction time (10–30 minutes), thus reducing the total sulfur under these mild conditions compared to conventional extraction. The optimized conditions were however not efficient in removing ash.     

耦合波导管本征值的讨论

本文对文献提出一些不同的见解,对联系边界条件有另外的提法,在处理方法上亦有不同。本文认为耦合槽可以分为浅槽和深槽两种形式,首先对槽口的电场作了近似估计,然后用格林张量函数求出矩形和圆形波导耦合时的电磁场,再用边界条件得出本征方程;对于本征方程,认为可以用两个电路的导纳相等来理解。本文亦对耦合波导管的传输常数和原有波导管传输常数加以讨论,最后再对某些应用上的问题加以简单的讨论。