Aluminum‐doped zinc oxide (AZO) is a suitable material for use as transparent electrode. Due to its lower price it is applied in the production of silicon solar cells. However, it is difficult to ...obtain suitable electrical properties at low deposition temperatures. Moreover, the AZO films with low thickness exhibit significantly higher average resistivity, which limits their usability, especially if they are prepared on flexible substrates. A lot of effort is invested to replace indium tin oxide (ITO) to a much greater extent now, since Indium is rare and its price is rising, thus the preparation of low‐thickness AZO films at low temperature is also subject of intense research. The presented paper summarizes the reported results, discusses the causes of the differences between ITO and AZO films, and suggests the direction of research and the potential solution that should lead to increased usability of AZO films and also possible replacement of ITO films.
This paper reviews the influence of deposition parameters on the electrical properties of aluminum doped zinc oxide, which is cheap and non‐toxic transparent conductive material, but its usability is limited due to higher resistivity of low thickness ZnO films prepared at low temperature. The main reasons are discussed and the potential solutions to improve the electrical properties are proposed.
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A broad overview of how experimental parameters affect the performance of Li–S batteries is presented here, extending the view on these batteries beyond sophisticated conductive sulfur hosts, which ...have been the primary focus of many studies in recent years. The exquisite sensitivity of the Li–S system to various experimental parameters speaks to the importance of directing future research towards the entire Li–S‐battery set‐up, rather than just some components. The main overall goal should be to produce cells with high specific energy and energy density. These are challenging tasks and more work is required, in particular in the area of cell engineering. The achievements spotlighted in this report show that outstanding results can be obtained by suitably engineering cathodes and other cell parts, without the need to use advanced structured hosts for sulfur. A lot of stimulating, original and successful research has been done recently in the field, leading to satisfying Li–S battery performances and paving the way for more applied research, with the goal of entering a pre‐application phase in Li–S battery development.
A broad overview of how experimental parameters affect the performance of Li–S batteries beyond sophisticated conductive sulfur hosts is presented. The exquisite sensitivity of the Li–S system to various experimental parameters speaks to the importance of directing future research towards the entire Li–S‐battery set‐up, rather than just some components.
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The solid electrolyte interphase (SEI) is a protecting layer formed on the negative electrode of Li-ion batteries as a result of electrolyte decomposition, mainly during the first cycle. Battery ...performance, irreversible charge “loss”, rate capability, cyclability, exfoliation of graphite and safety are highly dependent on the quality of the SEI. Therefore, understanding the actual nature and composition of SEI is of prime interest. If the chemistry of the SEI formation and the manner in which each component affects battery performance are understood, SEI could be tuned to improve battery performance. In this paper key points related to the nature, formation, and features of the SEI formed on carbon negative electrodes are discussed. SEI has been analyzed by various analytical techniques amongst which FTIR and XPS are most widely used. FTIR and XPS data of SEI and its components as published by many research groups are compiled in tables for getting a global picture of what is known about the SEI. This article shall serve as a handy reference as well as a starting point for research related to SEI.
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The lithium (de)-insertion mechanism from LiNi0.80Co0.15Al0.05O2 (NCA) has been investigated by means of combined electrochemical analysis, operando differential electrochemical mass spectrometry ...(DEMS) experiments, and in situ X-ray diffraction (XRD) experiments during the first three cycles. Qualitative analysis of cyclic voltammetry data illustrated a possible irreversible activation of the material. Operando DEMS and internal cell pressure measurements combined with ex situ XRD and electrochemical impedance spectroscopy demonstrated that Li2CO3 surface film on the NCA electrode degrades on oxidation and reforms on reduction, which has an effect on the lithium (de)-insertion reaction kinetics. In situ XRD studies clearly show mechanistic differences in the reaction pathways between the first and second cycle/following cycles. While the first charge reveals a combination of an irreversible two-phase transition plus a reversible solid solution reaction mechanism, the second charge is mainly dominated by a solid solution process. Such differences have been ascribed to changes in two factors, the electronic conductivity and the Li ion mobility of the NCA electrode.
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While tools for the automated analysis of MS and LC-MS/MS data are continuously improving, it is still often the case that at the end of an experiment, the mass spectrometrist will spend time ...carefully examining individual spectra. Current software support is mostly provided only by the instrument vendors, and the available software tools are often instrument-dependent. Here we present a new generation of mMass, a cross-platform environment for the precise analysis of individual mass spectra. The software covers a wide range of processing tasks such as import from various data formats, smoothing, baseline correction, peak picking, deisotoping, charge determination, and recalibration. Functions presented in the earlier versions such as in silico digestion and fragmentation were redesigned and improved. In addition to Mascot, an interface for ProFound has been implemented. A specific tool is available for isotopic pattern modeling to enable precise data validation. The largest available lipid database (from the LIPID MAPS Consortium) has been incorporated and together with the new compound search tool lipids can be rapidly identified. In addition, the user can define custom libraries of compounds and use them analogously. The new version of mMass is based on a stand-alone Python library, which provides the basic functionality for data processing and interpretation. This library can serve as a good starting point for other developers in their projects. Binary distributions of mMass, its source code, a detailed user’s guide, and video tutorials are freely available from www.mmass.org.
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The investigation of plant genome structure and evolution requires comprehensive characterization of repetitive sequences that make up the majority of higher plant nuclear DNA. Since genome-wide ...characterization of repetitive elements is complicated by their high abundance and diversity, novel approaches based on massively-parallel sequencing are being adapted to facilitate the analysis. It has recently been demonstrated that the low-pass genome sequencing provided by a single 454 sequencing reaction is sufficient to capture information about all major repeat families, thus providing the opportunity for efficient repeat investigation in a wide range of species. However, the development of appropriate data mining tools is required in order to fully utilize this sequencing data for repeat characterization.
We adapted a graph-based approach for similarity-based partitioning of whole genome 454 sequence reads in order to build clusters made of the reads derived from individual repeat families. The information about cluster sizes was utilized for assessing the proportion and composition of repeats in the genomes of two model species, Pisum sativum and Glycine max, differing in genome size and 454 sequencing coverage. Moreover, statistical analysis and visual inspection of the topology of the cluster graphs using a newly developed program tool, SeqGrapheR, were shown to be helpful in distinguishing basic types of repeats and investigating sequence variability within repeat families.
Repetitive regions of plant genomes can be efficiently characterized by the presented graph-based analysis and the graph representation of repeats can be further used to assess the variability and evolutionary divergence of repeat families, discover and characterize novel elements, and aid in subsequent assembly of their consensus sequences.
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Lithium-ion batteries are the state-of-the-art electrochemical energy storage technology for mobile electronic devices and electric vehicles. Accordingly, they have attracted a continuously ...increasing interest in academia and industry, which has led to a steady improvement in energy and power density, while the costs have decreased at even faster pace. Important questions, though, are, to which extent and how (fast) the performance can be further improved, and how the envisioned goal of truly sustainable energy storage can be realized.
Herein, we combine a comprehensive review of important findings and developments in this field that have enabled their tremendous success with an overview of very recent trends concerning the active materials for the negative and positive electrode as well as the electrolyte. Moreover, we critically discuss current and anticipated electrode fabrication processes, as well as an essential prerequisite for “greener” batteries – the recycling. In each of these chapters, we eventually summarize important remaining challenges and propose potential directions for further improvement. Finally, we conclude this article with a brief summary of the performance metrics of commercial lithium-ion cells and a few thoughts towards the future development of this technology including several key performance indicators for the mid-term to long-term future.
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•Comprehensive review of commercially used Li-ion active materials and electrolytes.•Overview of relevant electrode preparation and recycling technologies.•Critical discussion of the state of the art and remaining challenges.•Indication of future research directions towards further improved Li-ion batteries.•Proposal of key performance indicators for the mid- & long-term future development.
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Memory effects are well known to users of nickel-cadmium and nickel-metal-hydride batteries. If these batteries are recharged repeatedly after being only partially discharged, they gradually lose ...usable capacity owing to a reduced working voltage. Lithium-ion batteries, in contrast, are considered to have no memory effect. Here we report a memory effect in LiFePO4-one of the materials used for the positive electrode in Li-ion batteries-that appears already after only one cycle of partial charge and discharge. We characterize this memory effect of LiFePO4 and explain its connection to the particle-by-particle charge/discharge model. This effect is important for most battery uses, as the slight voltage change it causes can lead to substantial miscalculations in estimating the state of charge of batteries.
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Repetitive DNA makes up large portions of plant and animal nuclear genomes, yet it remains the least-characterized genome component in most species studied so far. Although the recent availability of ...high-throughput sequencing data provides necessary resources for in-depth investigation of genomic repeats, its utility is hampered by the lack of specialized bioinformatics tools and appropriate computational resources that would enable large-scale repeat analysis to be run by biologically oriented researchers.
Here we present RepeatExplorer, a collection of software tools for characterization of repetitive elements, which is accessible via web interface. A key component of the server is the computational pipeline using a graph-based sequence clustering algorithm to facilitate de novo repeat identification without the need for reference databases of known elements. Because the algorithm uses short sequences randomly sampled from the genome as input, it is ideal for analyzing next-generation sequence reads. Additional tools are provided to aid in classification of identified repeats, investigate phylogenetic relationships of retroelements and perform comparative analysis of repeat composition between multiple species. The server allows to analyze several million sequence reads, which typically results in identification of most high and medium copy repeats in higher plant genomes.
Trifluoromethylation of α‑Haloketones Novák, Petr; Lishchynskyi, Anton; Grushin, Vladimir V
Journal of the American Chemical Society,
10/2012, Volume:
134, Issue:
39
Journal Article
Peer reviewed
The C–X bond (X = Br, Cl) of α-haloketones is smoothly trifluoromethylated with the fluoroform-derived CuCF3 reagent recently developed in our laboratories. This is the first nucleophilic ...α-trifluoromethylation reaction of carbonyl compounds and a rare example of CF3–C(sp3) coupling. The transformation employs only low-cost chemicals and cleanly occurs in up to 99% yield at room temperature, thereby providing an unprecedentedly easy entry to valuable 2,2,2-trifluoroethylketones.
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