19 results
Search Results
Now showing 1 - 10 of 19
- ItemHigh‐Entropy Sulfides as Electrode Materials for Li‐Ion Batteries(Weinheim : Wiley-VCH, 2022) Lin, Ling; Wang, Kai; Sarkar, Abhishek; Njel, Christian; Karkera, Guruprakash; Wang, Qingsong; Azmi, Raheleh; Fichtner, Maximilian; Hahn, Horst; Schweidler, Simon; Breitung, BenHigh-entropy sulfides (HESs) containing 5 equiatomic transition metals (M), with different M:S ratios, are prepared by a facile one-step mechanochemical approach. Two new types of single-phase HESs with pyrite (Pa-3) and orthorhombic (Pnma) structures are obtained and demonstrate a homogeneously mixed solid solution. The straightforward synthesis method can easily tune the desired metal to sulfur ratio for HESs with different stoichiometries, by utilizing the respective metal sulfides, even pure metals, and sulfur as precursor chemicals. The structural details and solid solution nature of HESs are studied by X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray spectroscopy, electron energy loss spectroscopy, X-ray photoelectron spectroscopy, inductively coupled plasma optical emission spectroscopy, and Mössbauer spectroscopy. Since transition metal sulfides are a very versatile material class, here the application of HESs is presented as electrode materials for reversible electrochemical energy storage, in which the HESs show high specific capacities and excellent rate capabilities in secondary Li-ion batteries.
- ItemTransparent Power-Generating Windows Based on Solar-Thermal-Electric Conversion(Weinheim : Wiley-VCH, 2021) Zhang, Qihao; Huang, Aibin; Ai, Xin; Liao, Jincheng; Song, Qingfeng; Reith, Heiko; Cao, Xun; Fang, Yueping; Schierning, Gabi; Nielsch, Kornelius; Bai, Shengqiang; Chen, LidongIntegrating transparent solar-harvesting systems into windows can provide renewable on-site energy supply without altering building aesthetics or imposing further design constraints. Transparent photovoltaics have shown great potential, but the increased transparency comes at the expense of reduced power-conversion efficiency. Here, a new technology that overcomes this limitation by combining solar-thermal-electric conversion with a material's wavelength-selective absorption is presented. A wavelength-selective film consisting of Cs0.33WO3 and resin facilitates high visible-light transmittance (up to 88%) and outstanding ultraviolet and infrared absorbance, thereby converting absorbed light into heat without sacrificing transparency. A prototype that couples the film with thermoelectric power generation produces an extraordinary output voltage of ≈4 V within an area of 0.01 m2 exposed to sunshine. Further optimization design and experimental verification demonstrate high conversion efficiency comparable to state-of-the-art transparent photovoltaics, enriching the library of on-site energy-saving and transparent power generation.
- ItemCurrent State-of-the-Art in the Interface/Surface Modification of Thermoelectric Materials(Weinheim : Wiley-VCH, 2021) He, Shiyang; Lehmann, Sebastian; Bahrami, Amin; Nielsch, KorneliusThermoelectric (TE) materials are prominent candidates for energy converting applications due to their excellent performance and reliability. Extensive efforts for improving their efficiency in single-/multi-phase composites comprising nano/micro-scale second phases are being made. The artificial decoration of second phases into the thermoelectric matrix in multi-phase composites, which is distinguished from the second-phase precipitation occurring during the thermally equilibrated synthesis of TE materials, can effectively enhance their performance. Theoretically, the interfacial manipulation of phase boundaries can be extended to a wide range of materials. High interface densities decrease thermal conductivity when nano/micro-scale grain boundaries are obtained and certain electronic structure modifications may increase the power factor of TE materials. Based on the distribution of second phases on the interface boundaries, the strategies can be divided into discontinuous and continuous interfacial modifications. The discontinuous interfacial modifications section in this review discusses five parts chosen according to their dispersion forms, including metals, oxides, semiconductors, carbonic compounds, and MXenes. Alternatively, gas- and solution-phase process techniques are adopted for realizing continuous surface changes, like the core–shell structure. This review offers a detailed analysis of the current state-of-the-art in the field, while identifying possibilities and obstacles for improving the performance of TE materials.
- ItemApplications of Carbon Nanotubes in the Internet of Things Era(Berlin ; Heidelberg [u.a.] : Springer, 2021) Pang, Jinbo; Bachmatiuk, Alicja; Yang, Feng; Liu, Hong; Zhou, Weijia; Rümmeli, Mark H.; Cuniberti, GianaurelioThe post-Moore's era has boosted the progress in carbon nanotube-based transistors. Indeed, the 5G communication and cloud computing stimulate the research in applications of carbon nanotubes in electronic devices. In this perspective, we deliver the readers with the latest trends in carbon nanotube research, including high-frequency transistors, biomedical sensors and actuators, brain-machine interfaces, and flexible logic devices and energy storages. Future opportunities are given for calling on scientists and engineers into the emerging topics.
- ItemInfluence of nanobody binding on fluorescence emission, mobility, and organization of GFP-tagged proteins(Amsterdam [u.a.] : Elsevier, 2020) Schneider, Falk; Sych, Taras; Eggeling, Christian; Sezgin, ErdincAdvanced fluorescence microscopy studies require specific and monovalent molecular labeling with bright and photostable fluorophores. This necessity led to the widespread use of fluorescently labeled nanobodies against commonly employed fluorescent proteins (FPs). However, very little is known how these nanobodies influence their target molecules. Here, we tested commercially available nanobodies and observed clear changes of the fluorescence properties, mobility and organization of green fluorescent protein (GFP) tagged proteins after labeling with the anti-GFP nanobody. Intriguingly, we did not observe any co-diffusion of fluorescently labeled nanobodies with the GFP-labeled proteins. Our results suggest significant binding of the nanobodies to a non-emissive, likely oligomerized, form of the FPs, promoting disassembly into monomeric form after binding. Our findings have significant implications on the application of nanobodies and GFP labeling for studying dynamic and quantitative protein organization in the plasma membrane of living cells using advanced imaging techniques.
- ItemOn-Chip Micro Temperature Controllers Based on Freestanding Thermoelectric Nano Films for Low-Power Electronics(Berlin ; Heidelberg [u.a.] : Springer, 2024) Jin, Qun; Guo, Tianxiao; Pérez, Nicolás; Yang, Nianjun; Jiang, Xin; Nielsch, Kornelius; Reith, HeikoDense and flat freestanding Bi2Te3-based thermoelectric nano films were successfully fabricated by sputtering technology using a newly developed nano graphene oxide membrane as a substrate. On-chip micro temperature controllers were integrated using conventional micro-electromechanical system technology, to achieve energy-efficient temperature control for low-power electronics. The tunable equivalent thermal resistance enables an ultrahigh temperature control capability of 100 K mW−1 and an ultra-fast cooling rate exceeding 2000 K s−1, as well as excellent reliability of up to 1 million cycles.
- ItemHumic Substance Photosensitized Degradation of Phthalate Esters Characterized by 2H and 13C Isotope Fractionation(Columbus, Ohio : American Chemical Society, 2023) Min, Ning; Yao, Jun; Li, Hao; Chen, Zhihui; Pang, Wancheng; Zhu, Junjie; Kümmel, Steffen; Schaefer, Thomas; Herrmann, Hartmut; Richnow, Hans HermannThe photosensitized transformation of organic chemicals is an important degradation mechanism in natural surface waters, aerosols, and water films on surfaces. Dissolved organic matter including humic-like substances (HS), acting as photosensitizers that participate in electron transfer reactions, can generate a variety of reactive species, such as OH radicals and excited triplet-state HS (3HS*), which promote the degradation of organic compounds. We use phthalate esters, which are important contaminants found in wastewaters, landfills, soils, rivers, lakes, groundwaters, and mine tailings. We use phthalate esters as probes to study the reactivity of HS irradiated with artificial sunlight. Phthalate esters with different side-chain lengths were used as probes for elucidation of reaction mechanisms using 2H and 13C isotope fractionation. Reference experiments with the artificial photosensitizers 4,5,6,7-tetrachloro-2′,4′,5′,7′-tetraiodofluorescein (Rose Bengal), 3-methoxy-acetophenone (3-MAP), and 4-methoxybenzaldehyde (4-MBA) yielded characteristic fractionation factors (−4 ± 1, −4 ± 2, and −4 ± 1‰ for 2H; 0.7 ± 0.2, 1.0 ± 0.4, and 0.8 ± 0.2‰ for 13C), allowing interpretation of reaction mechanisms of humic substances with phthalate esters. The correlation of 2H and 13C fractions can be used diagnostically to determine photosensitized reactions in the environment and to differentiate among biodegradation, hydrolysis, and photosensitized HS reaction.
- ItemEvolution of Ozone Pollution in China: What Track Will It Follow?(Columbus, Ohio : American Chemical Society, 2022) Guo, Jia; Zhang, Xiaoshan; Gao, Yi; Wang, Zhangwei; Zhang, Meigen; Xue, Wenbo; Herrmann, Hartmut; Brasseur, Guy Pierre; Wang, Tao; Wang, ZheIncreasing surface ozone (O3) concentrations has emerged as a key air pollution problem in many urban regions worldwide in the last decade. A longstanding major issue in tackling ozone pollution is the identification of the O3 formation regime and its sensitivity to precursor emissions. In this work, we propose a new transformed empirical kinetic modeling approach (EKMA) to diagnose the O3 formation regime using regulatory O3 and NO2 observation datasets, which are easily accessible. We demonstrate that mapping of monitored O3 and NO2 data on the modeled regional O3-NO2 relationship diagram can illustrate the ozone formation regime and historical evolution of O3 precursors of the region. By applying this new approach, we show that for most urban regions of China, the O3 formation is currently associated with a volatile organic compound (VOC)-limited regime, which is located within the zone of daytime-produced O3 (DPO3) to an 8h-NO2 concentration ratio below 8.3 ([DPO3]/[8h-NO2] ≤ 8.3). The ozone production and controlling effects of VOCs and NOx in different cities of China were compared according to their historical O3-NO2 evolution routes. The approach developed herein may have broad application potential for evaluating the efficiency of precursor controls and further mitigating O3 pollution, in particular, for regions where comprehensive photochemical studies are unavailable.
- ItemNo Evidence for a Significant Impact of Heterogeneous Chemistry on Radical Concentrations in the North China Plain in Summer 2014(Columbus, Ohio : American Chemical Society, 2020) Tan, Zhaofeng; Hofzumahaus, Andreas; Lu, Keding; Brown, Steven S.; Holland, Frank; Huey, Lewis Gregory; Kiendler-Scharr, Astrid; Li, Xin; Liu, Xiaoxi; Ma, Nan; Min, Kyung-Eun; Rohrer, Franz; Shao, Min; Wahner, Andreas; Wang, Yuhang; Wiedensohler, Alfred; Wu, Yusheng; Wu, Zhijun; Zeng, Limin; Zhang, Yuanhang; Fuchs, HendrikThe oxidation of nitric oxide to nitrogen dioxide by hydroperoxy (HO2) and organic peroxy radicals (RO2) is responsible for the chemical net ozone production in the troposphere and for the regeneration of hydroxyl radicals, the most important oxidant in the atmosphere. In Summer 2014, a field campaign was conducted in the North China Plain, where increasingly severe ozone pollution has been experienced in the last years. Chemical conditions in the campaign were representative for this area. Radical and trace gas concentrations were measured, allowing for calculating the turnover rates of gas-phase radical reactions. Therefore, the importance of heterogeneous HO2 uptake on aerosol could be experimentally determined. HO2 uptake could have suppressed ozone formation at that time because of the competition with gas-phase reactions that produce ozone. The successful reduction of the aerosol load in the North China Plain in the last years could have led to a significant decrease of HO2 loss on particles, so that ozone-forming reactions could have gained importance in the last years. However, the analysis of the measured radical budget in this campaign shows that HO2 aerosol uptake did not impact radical chemistry for chemical conditions in 2014. Therefore, reduced HO2 uptake on aerosol since then is likely not the reason for the increasing number of ozone pollution events in the North China Plain, contradicting conclusions made from model calculations reported in the literature. © 2020 American Chemical Society.
- ItemThe Many Deaths of Supercapacitors: Degradation, Aging, and Performance Fading(Weinheim : Wiley-VCH, 2023) Pameté, Emmanuel; Köps, Lukas; Kreth, Fabian Alexander; Pohlmann, Sebastian; Varzi, Alberto; Brousse, Thierry; Balducci, Andrea; Presser, VolkerHigh-performance electrochemical applications have expedited the research in high-power devices. As such, supercapacitors, including electrical double-layer capacitors (EDLCs) and pseudocapacitors, have gained significant attention due to their high power density, long cycle life, and fast charging capabilities. Yet, no device lasts forever. It is essential to understand the mechanisms behind performance degradation and aging so that these bottlenecks can be addressed and tailored solutions can be developed. Herein, the factors contributing to the aging and degradation of supercapacitors, including electrode materials, electrolytes, and other aspects of the system, such as pore blocking, electrode compositions, functional groups, and corrosion of current collectors are examined. The monitoring and characterizing of the performance degradation of supercapacitors, including electrochemical methods, in situ, and ex situ techniques are explored. In addition, the degradation mechanisms of different types of electrolytes and electrode materials and the effects of aging from an industrial application standpoint are analyzed. Next, how electrode degradations and electrolyte decompositions can lead to failure, and pore blocking, electrode composition, and other factors that affect the device's lifespan are examined. Finally, the future directions and challenges for reducing supercapacitors' performance degradation, including developing new materials and methods for characterizing and monitoring the devices are summarized.