Measurement uncertainties of size, shape, and surface measurements using transmission electron microscopy of near-monodisperse, near-spherical nanoparticles

Carbon nanotubes are currently one of the most important materials due to their strong mechanical resistance, light weight, and transport properties. Since the publication of Ijima’s paper on tubular carbon structures (Iijima, Nature 354:56–58, 1991), approximately 80,000 research articles have been published according to the ISI web of science (WOS) database, using “carbon nanotube*” as the search criterion in the search by topic option. In this work, the development and impact of nanoscience and nanotechnology (N&N) and carbon nanotubes on several research areas, journals, specific papers, and emerging research areas are analyzed and discussed. Considering the production of papers in these areas from 1997 to 2012, quantitatively speaking, the People’s Republic of China is emerging as the leading country in N&N and carbon nanotube research, passing the United States of America. WOS data analysis of nanoscience, nanotechnology, and carbon nanotube research in developed and developing countries is discussed, and some ideas for accelerating the progress in these important research areas are proposed.     

Einfache und schnelle analytische Methoden zur Bestimmung des Wirkungssubstanzgehalts von Pflanzenschutzmitteln

Ohne Zusammenfassung     

Extraction and derivatization of polar herbicides for GC-MS analyses

A sample preparation procedure including a simultaneous microwave-assisted (MA) extraction and derivatization for the determination of chlorophenoxy acids in soil samples is presented. For a selective and sensitive measurement, an analytical technique such as GC coupled with MS needs to be adopted. For GC analyses, chlorophenoxy acids have to be converted into more volatile and thermally stable derivatives. Derivatization by means of microwave radiation offers new alternatives in terms of shorter derivatization time and reduces susceptibility for the formation of artefacts. Extraction and derivatization into methyl esters (ME) were performed with sulphuric acid and methanol. Due to the novelty of the simultaneous extraction and derivatization assisted by means of microwave radiation, a careful investigation and optimization of influential reaction parameters was necessary. It could be shown that the combination of sulphuric acid and methanol provides a fast sample preparation including an efficient clean up procedure. The data obtained by the described method are in good agreement with those published for the reference material. Finally, compared to conventional heating and also to the standard procedure of the EPA, the sample preparation time could be considerably shortened.     

Study of variables for optimization of the dye indosol adsorption process using red mud and clay as adsorbents

The effluents from the textile industry, which not properly treated or discharged directly into water bodies, are a serious environmental problem. In order to find options to solve this problem, in this study, it was evaluate two alternative adsorbents: red mud and smectite clay, to remove the dye Indosol dark-blue SF-BL SGR 240. Assays were performed in batch using the experimental design to optimize the process and evaluate the influence of pH, mass and agitation speed on the adsorption capacity of dye by each material. The results showed that the adsorption process was influenced by the amount of mass of the adsorbent, by the pH and the by interaction between pH and mass, thereby obtaining a removal of approximately 0.110 and 0.119 mg g^?1 with red mud and smectite clay respectively.     

Structure of ethene adsorption sites on supported metal catalysts from in situ XANES Analysis

The structures of the catalytically active sites in supported metal catalysts are a long sought after goal. In this study, XAS has been used to establish these structures. The ethene-induced changes in the XAS spectra as a function of temperature and pressure were correlated to changes in the adsorption mode of the hydrocarbon. At low temperature, ethene was adsorbed in on-top (pi) and bridged (di-sigma) sites on small platinum clusters. Below room temperature, the adsorbed ethene was dehydrogenated to an ethylidyne species, which was adsorbed in threefold Pt sites. On larger clusters the dehydrogenation proceeded at higher temperature indicating a different reactivity. EXAFS results showed that changes in the geometrical structures were mainly due to (co)adsorbed hydrogen. Our results for platinum agree with those obtained using other techniques proving that detailed shape analysis of the L3 edge XANES is a practical tool to determine the structure of the sites that are involved in bonding to reactants and intermediates. Application to gold and alloy catalysts showed that ethene induced a significant change in the electronic structure of gold nanoclusters that could be interpreted as ethene adsorbed on top of single gold atoms or in bridged sites. Ethene adsorbed on both platinum and gold in the bimetallic clusters.     

Analysis of absorption enhancement in tailor‐made periodic polycrystalline silicon microarrays

We present a design study of 3D photonic poly‐Si microarchitectures on 2 µm periodically textured glass substrates for application as absorber layers in crystalline Si thin‐film solar cells. Different arrays of microholes and microcones were fabricated in a low‐cost process, by combining high rate electron beam evaporation, nanoimprint technology and self‐organized solid phase crystallization. Two promising designs exhibiting strong absorption enhancement were identified by optical analysis. High angular acceptance and calculated maximum achievable short‐circuit current density of 27.6 mA/cm² for an effective Si thickness of 1.1 µm highlight the optical potential of these microarchitectures as broadband absorbers in polycrystalline Si thin‐film solar cells.

     

Solution structure and conformational dynamics of deoxyxylonucleic acids (dXNA): an orthogonal nucleic acid candidate

Orthogonal nucleic acids are chemically modified nucleic acid polymers that are unable to transfer information with natural nucleic acids and thus can be used in synthetic biology to store and transfer genetic information independently. Recently, it was proposed that xylose-DNA (dXNA) can be considered to be a potential candidate for an orthogonal system. Herein, we present the structure in solution and conformational analysis of two self-complementary, fully modified dXNA oligonucleotides, as determined by CD and NMR spectroscopy. These studies are the initial experimental proof of the structural orthogonality of dXNAs. In aqueous solution, dXNA duplexes predominantly form a linear ladderlike (type-1) structure. This is the first example of a furanose nucleic acid that adopts a ladderlike structure. In the presence of salt, an equilibrium exists between two types of duplex form. The corresponding nucleoside triphosphates (dXNTPs) were synthesized and evaluated for their ability to be incorporated into a growing DNA chain by using several natural and mutant DNA polymerases. Despite the structural orthogonality of dXNA, DNA polymerase β mutant is able to incorporate the dXNTPs, showing DNA-dependent dXNA polymerase activity.