514 results on '"Alexander Eychmüller"'
Search Results
2. Metal-Based Aerogels and Porous Composites as Efficient Catalysts: Synthesis and Catalytic Performance
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Ran Du and Alexander Eychmüller
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n/a ,Chemical technology ,TP1-1185 ,Chemistry ,QD1-999 - Abstract
Faced with the threat of energy shortage and environment pollution in modern society, the development of efficient and cost-effective catalytic systems is becoming increasingly important [...]
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- 2023
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3. Unveiling reductant chemistry in fabricating noble metal aerogels for superior oxygen evolution and ethanol oxidation
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Ran Du, Jinying Wang, Ying Wang, René Hübner, Xuelin Fan, Irena Senkovska, Yue Hu, Stefan Kaskel, and Alexander Eychmüller
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Science - Abstract
Non-efficient gelation methods for noble metal particles limit the development of the corresponding gel materials. Here the authors describe the role of reductants, unlocking ligand chemistry, and largely expanding the composition space of noble metal aerogels for high-performance electrocatalysis.
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- 2020
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4. Heterostructured Bismuth Telluride Selenide Nanosheets for Enhanced Thermoelectric Performance
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Christoph Bauer, Igor Veremchuk, Christof Kunze, Albrecht Benad, Volodymyr M. Dzhagan, Danny Haubold, Darius Pohl, Gabi Schierning, Kornelius Nielsch, Vladimir Lesnyak, and Alexander Eychmüller
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bismuth chalcogenides ,colloidal synthesis ,core/shell heterostructures ,nanosheets ,thermoelectrics ,Materials of engineering and construction. Mechanics of materials ,TA401-492 - Abstract
The n‐type semiconductor system Bi2Te3Bi2Se3 is known as a low‐temperature thermoelectric material with a potentially high efficiency. Herein, a facile approach is reported to synthesize core/shell heterostructured Bi2Te2Se/Bi2Te3 nanosheets (NSs) with lateral dimensions of 1–3 μm and thickness of about 50 nm. Bi2Te3 and Bi2Se3, as well as heterostructured Bi2Te2Se/Bi2Te3 NSs are obtained via colloidal synthesis. Heterostructured NSs show an inhomogeneous distribution of the chalcogen atoms forming selenium and tellurium‐rich layers across the NS thickness, resulting in a core/shell structure. Detailed morphological studies reveal that these structures contain nanosized pores. These features contribute to the overall thermoelectric properties of the material, inducing strong phonon scattering at grain boundaries in compacted solids. NSs are processed into nanostructured bulks through spark plasma sintering of dry powders to form a thermoelectric material with high power factor. Electrical characterization of our materials reveals a strong anisotropic behavior in consolidated pellets. It is further demonstrated that by simple thermal annealing, core/shell structure can be controllably transformed into alloyed one. Using this approach pellets with Bi2Te2.55Se0.45 composition are obtained, which exhibit low thermal conductivity and high power factor for in‐plane direction with zT of 1.34 at 400 K.
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- 2021
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5. Expanding the Range: AuCu Metal Aerogels from H2O and EtOH
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Maximilian Georgi, Johannes Kresse, Karl Hiekel, René Hübner, and Alexander Eychmüller
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metal ,aerogel ,gold ,copper ,ethanol ,water ,Chemical technology ,TP1-1185 ,Chemistry ,QD1-999 - Abstract
Due to their self-supporting and nanoparticulate structure, metal aerogels have emerged as excellent electrocatalysts, especially in the light of the shift to renewable energy cycles. While a large number of synthesis parameters have already been studied in depth, only superficial attention has been paid to the solvent. In order to investigate the influence of this parameter with respect to the gelation time, crystallinity, morphology, or porosity of metal gels, AuxCuy aerogels were prepared in water and ethanol. It was shown that although gelation in water leads to highly porous gels (60 m2g−1), a CuO phase forms during this process. The undesired oxide could be selectively removed using a post-washing step with formic acid. In contrast, the solvent change to EtOH led to a halving of the gelation time and the suppression of Cu oxidation. Thus, pure Cu aerogels were synthesized in addition to various bimetallic Au3X (X = Ni, Fe, Co) gels. The faster gelation, caused by the lower permittivity of EtOH, led to the formation of thicker gel strands, which resulted in a lower porosity of the AuxCuy aerogels. The advantage given by the solvent choice simplifies the preparation of metal aerogels and provides deeper knowledge about their gelation.
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- 2022
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6. 'Green' Aqueous Synthesis and Advanced Spectral Characterization of Size-Selected Cu2ZnSnS4 Nanocrystal Inks
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Oleksandr Stroyuk, Alexandra Raevskaya, Oleksandr Selyshchev, Volodymyr Dzhagan, Nikolai Gaponik, Dietrich R. T. Zahn, and Alexander Eychmüller
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NC Inks ,Nanocrystals ,Aqueous Synthesis ,CZTS NCs ,Size-selective Precipitation ,Medicine ,Science - Abstract
Abstract Structure, composition, and optical properties of colloidal mercaptoacetate-stabilized Cu2ZnSnS4 (CZTS) nanocrystal inks produced by a “green” method directly in aqueous solutions were characterized. A size-selective precipitation procedure using 2-propanol as a non-solvent allows separating a series of fractions of CZTS nanocrystals with an average size (bandgap) varying from 3 nm (1.72 eV) to 2 nm (2.04 eV). The size-selected CZTS nanocrystals revealed also phonon confinement, with the main phonon mode frequency varying by about 4 cm−1 between 2 nm and 3 nm NCs.
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- 2018
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7. The distribution and degradation of radiolabeled superparamagnetic iron oxide nanoparticles and quantum dots in mice
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Denise Bargheer, Artur Giemsa, Barbara Freund, Markus Heine, Christian Waurisch, Gordon M. Stachowski, Stephen G. Hickey, Alexander Eychmüller, Jörg Heeren, and Peter Nielsen
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biodistribution ,chromium(III) ,51Cr ,quantum dots ,SPIOs ,zinc metabolism ,65Zn ,Technology ,Chemical technology ,TP1-1185 ,Science ,Physics ,QC1-999 - Abstract
51Cr-labeled, superparamagnetic, iron oxide nanoparticles (51Cr-SPIOs) and 65Zn-labeled CdSe/CdS/ZnS-quantum dots (65Zn-Qdots) were prepared using an easy, on demand, exchange-labeling technique and their particokinetic parameters were studied in mice after intravenous injection. The results indicate that the application of these heterologous isotopes can be used to successfully mark the nanoparticles during initial distribution and organ uptake, although the 65Zn-label appeared not to be fully stable. As the degradation of the nanoparticles takes place, the individual transport mechanisms for the different isotopes must be carefully taken into account. Although this variation in transport paths can bring new insights with regard to the respective trace element homeostasis, it can also limit the relevance of such trace material-based approaches in nanobioscience. By monitoring 51Cr-SPIOs after oral gavage, the gastrointestinal non-absorption of intact SPIOs in a hydrophilic or lipophilic surrounding was measured in mice with such high sensitivity for the first time. After intravenous injection, polymer-coated, 65Zn-Qdots were mainly taken up by the liver and spleen, which was different from that of ionic 65ZnCl2. Following the label for 4 weeks, an indication of substantial degradation of the nanoparticles and the release of the label into the Zn pool was observed. Confocal microscopy of rat liver cryosections (prepared 2 h after intravenous injection of polymer-coated Qdots) revealed a colocalization with markers for Kupffer cells and liver sinusoidal endothelial cells (LSEC), but not with hepatocytes. In J774 macrophages, fluorescent Qdots were found colocalized with lysosomal markers. After 24 h, no signs of degradation could be detected. However, after 12 weeks, no fluorescent nanoparticles could be detected in the liver cryosections, which would confirm our 65Zn data showing a substantial degradation of the polymer-coated CdSe/CdS/ZnS-Qdots in the liver.
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- 2015
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8. Synthesis of radioactively labelled CdSe/CdS/ZnS quantum dots for in vivo experiments
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Gordon M. Stachowski, Christoph Bauer, Christian Waurisch, Denise Bargheer, Peter Nielsen, Jörg Heeren, Stephen G. Hickey, and Alexander Eychmüller
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biomarker ,CdSe/CdS/ZnS ,quantum dots ,radioactive labelling ,65Zn ,Technology ,Chemical technology ,TP1-1185 ,Science ,Physics ,QC1-999 - Abstract
During the last decades of nanoparticles research, many nanomaterials have been developed for applications in the field of bio-labelling. For the visualization of transport processes in the body, organs and cells, luminescent quantum dots (QDs) make for highly useful diagnostic tools. However, intercellular routes, bio-distribution, metabolism during degradation or quantification of the excretion of nanoparticles, and the study of the biological response to the QDs themselves are areas which to date have not been fully investigated. In order to aid in addressing those issues, CdSe/CdS/ZnS QDs were radioactively labelled, which allows quantification of the QD concentration in the whole body or in ex vivo samples by γ-counting. However, the synthesis of radioactively labelled QDs is not trivial since the coating process must be completely adapted, and material availability, security and avoidance of radioactive waste must be considered. In this contribution, the coating of CdSe/CdS QDs with a radioactive 65ZnS shell using a modified, operator-safe, SILAR procedure is presented. Under UV illumination, no difference in the photoluminescence of the radioactive and non-radioactive CdSe/CdS/ZnS colloidal solutions was observed. Furthermore, a down-scaled synthesis for the production of very small batches of 5 nmol QDs without loss in the fluorescence quality was developed. Subsequently, the radio-labelled QDs were phase transferred by encapsulation into an amphiphilic polymer. γ-counting of the radioactivity provided confirmation of the successful labelling and phase transfer of the QDs.
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- 2014
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9. The cell-type specific uptake of polymer-coated or micelle-embedded QDs and SPIOs does not provoke an acute pro-inflammatory response in the liver
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Markus Heine, Alexander Bartelt, Oliver T. Bruns, Denise Bargheer, Artur Giemsa, Barbara Freund, Ludger Scheja, Christian Waurisch, Alexander Eychmüller, Rudolph Reimer, Horst Weller, Peter Nielsen, and Joerg Heeren
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hepatocytes ,inflammation ,Kupffer cells ,liver sinusoidal endothelial cells ,nanoparticle toxicity ,nanoparticle uptake ,quantum dots ,superparamagnetic iron-oxide nanocrystals ,Technology ,Chemical technology ,TP1-1185 ,Science ,Physics ,QC1-999 - Abstract
Semiconductor quantum dots (QD) and superparamagnetic iron oxide nanocrystals (SPIO) have exceptional physical properties that are well suited for biomedical applications in vitro and in vivo. For future applications, the direct injection of nanocrystals for imaging and therapy represents an important entry route into the human body. Therefore, it is crucial to investigate biological responses of the body to nanocrystals to avoid harmful side effects. In recent years, we established a system to embed nanocrystals with a hydrophobic oleic acid shell either by lipid micelles or by the amphiphilic polymer poly(maleic anhydride-alt-1-octadecene) (PMAOD). The goal of the current study is to investigate the uptake processes as well as pro-inflammatory responses in the liver after the injection of these encapsulated nanocrystals. By immunofluorescence and electron microscopy studies using wild type mice, we show that 30 min after injection polymer-coated nanocrystals are primarily taken up by liver sinusoidal endothelial cells. In contrast, by using wild type, Ldlr-/- as well as Apoe-/- mice we show that nanocrystals embedded within lipid micelles are internalized by Kupffer cells and, in a process that is dependent on the LDL receptor and apolipoprotein E, by hepatocytes. Gene expression analysis of pro-inflammatory markers such as tumor necrosis factor alpha (TNFα) or chemokine (C-X-C motif) ligand 10 (Cxcl10) indicated that 48 h after injection internalized nanocrystals did not provoke pro-inflammatory pathways. In conclusion, internalized nanocrystals at least in mouse liver cells, namely endothelial cells, Kupffer cells and hepatocytes are at least not acutely associated with potential adverse side effects, underlining their potential for biomedical applications.
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- 2014
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10. Current Advances in TiO2-Based Nanostructure Electrodes for High Performance Lithium Ion Batteries
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Mahmoud Madian, Alexander Eychmüller, and Lars Giebeler
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battery ,anode ,titania ,anodic oxidation ,composite materials ,carbon ,performance effect ,mixed oxides ,Production of electric energy or power. Powerplants. Central stations ,TK1001-1841 ,Industrial electrochemistry ,TP250-261 - Abstract
The lithium ion battery (LIB) has proven to be a very reliably used system to store electrical energy, for either mobile or stationary applications. Among others, TiO2-based anodes are the most attractive candidates for building safe and durable lithium ion batteries with high energy density. A variety of TiO2 nanostructures has been thoroughly investigated as anodes in LIBs, e.g., nanoparticles, nanorods, nanoneedles, nanowires, and nanotubes discussed either in their pure form or in composites. In this review, we present the recent developments and breakthroughs demonstrated to synthesize safe, high power, and low cost nanostructured titania-based anodes. The reader is provided with an in-depth review of well-oriented TiO2-based nanotubes fabricated by anodic oxidation. Other strategies for modification of TiO2-based anodes with other elements or materials are also highlighted in this report.
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- 2018
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11. Mechanochemical Functionalization of Carbon Black at Room Temperature
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Desirée Leistenschneider, Katharina Zürbes, Christina Schneidermann, Sven Grätz, Steffen Oswald, Karl Wegner, Benjamin Klemmed, Lars Giebeler, Alexander Eychmüller, and Lars Borchardt
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carbon black ,hydrophilization ,functionalization ,mechanochemistry ,one-pot synthesis ,room temperature ,Organic chemistry ,QD241-441 - Abstract
Carbon nanomaterials such as carbon blacks are intrinsically hydrophobic with limited wettability in aqueous media, thus restricting their potential applications. To improve their hydrophilicity, common methods tend to utilize harmful chemicals and conditions, such as a mixture of KMnO4 and H2SO4 or a complex and expensive synthesis setup. In our work, we report a simple method to improve the wettability of these materials by a mechanochemical treatment completed within 1 h at room-temperature utilizing a NH3 solution. Besides increasing the specific surface area of the carbon black from 67 m2·g−1 up to 307 m2·g−1, our process also incorporates nitrogen- and oxygen-containing functional groups into the carbon. This reduces the contact angle from 80° to 30°, confirming an enhanced wettability. Our work presents an easy, fast, and straightforward pathway towards the functionalization of carbon nanomaterials and can be of use in various applications where aqueous wettability is advantageous.
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- 2018
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12. Ternary CNTs@TiO2/CoO Nanotube Composites: Improved Anode Materials for High Performance Lithium Ion Batteries
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Mahmoud Madian, Raghunandan Ummethala, Ahmed Osama Abo El Naga, Nahla Ismail, Mark Hermann Rümmeli, Alexander Eychmüller, and Lars Giebeler
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titanium dioxide ,cobalt oxide ,anodic oxidation ,spray pyrolysis ,carbon nanotubes ,mixed oxide nanotubes ,composite materials ,Technology ,Electrical engineering. Electronics. Nuclear engineering ,TK1-9971 ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Microscopy ,QH201-278.5 ,Descriptive and experimental mechanics ,QC120-168.85 - Abstract
TiO2 nanotubes (NTs) synthesized by electrochemical anodization are discussed as very promising anodes for lithium ion batteries, owing to their high structural stability, high surface area, safety, and low production cost. However, their poor electronic conductivity and low Li+ ion diffusivity are the main drawbacks that prevent them from achieving high electrochemical performance. Herein, we report the fabrication of a novel ternary carbon nanotubes (CNTs)@TiO2/CoO nanotubes composite by a two-step synthesis method. The preparation includes an initial anodic fabrication of well-ordered TiO2/CoO NTs from a Ti-Co alloy, followed by growing of CNTs horizontally on the top of the oxide films using a simple spray pyrolysis technique. The unique 1D structure of such a hybrid nanostructure with the inclusion of CNTs demonstrates significantly enhanced areal capacity and rate performances compared to pure TiO2 and TiO2/CoO NTs, without CNTs tested under identical conditions. The findings reveal that CNTs provide a highly conductive network that improves Li+ ion diffusivity, promoting a strongly favored lithium insertion into the TiO2/CoO NT framework, and hence resulting in high capacity and an extremely reproducible high rate capability.
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- 2017
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13. Element Distributions in Bimetallic Aerogels
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Cui Wang, Juan Herranz, René Hübner, Thomas J. Schmidt, and Alexander Eychmüller
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General Medicine ,General Chemistry - Abstract
Metal aerogels assembled from nanoparticles have captured grand attention because they combine the virtues of metals and aerogels and are regarded as ideal materials to address current environmental and energy issues. Among these aerogels, those composed of two metals not only display combinations (superpositions) of the properties of their individual metal components but also feature novel properties distinctly different from those of their monometallic relatives. Therefore, quite some effort has been invested in refining the synthetic methods, compositions, and structures of such bimetallic aerogels as to boost their performance for the envisaged application(s). One such use would be in the field of electrocatalysis, whereby it is also of utmost interest to unravel the element distributions of the (multi)metallic catalysts to achieve a ratio of their bottom-to-up design. Regarding the element distributions in bimetallic aerogels, advanced characterization techniques have identified alloys, core-shells, and structures in which the two metal particles are segregated (i.e., adjacent but without alloy or core-shell structure formation). While an almost infinite number of metal combinations to form bimetallic aerogels can be envisaged, the knowledge of their formation mechanisms and the corresponding element distributions is still in its infancy. The evolution of the observed musters is all but well understood, not to mention the positional changes of the elements observed in operando or in beginning- vs end-of-life comparisons (e.g., in fuel cell applications). With this motivation, in this Account we summarize the endeavors made in element distribution monitoring in bimetallic aerogels in terms of synthetic methods, expected structures, and their evolution during electrocatalysis. After an introductory chapter, we first describe briefly the two most important characterization techniques used for this, namely, scanning transmission electron microscopy (STEM) combined with element mapping (e.g., energy-dispersive X-ray spectroscopy (EDXS)) and X-ray absorption spectroscopy (XAS). We then explain the universal methods used to prepare bimetallic aerogels with different compositions. Those are divided into one-step methods in which gels formed from mixtures of the respective metal salts are coreduced and two-step approaches in which monometallic nanoparticles are mixed and gelated. Subsequently, we summarize the current state-of-knowledge on the element distributions unraveled using diverse characterization methods. This is extended to investigations of the element distributions being altered during electrochemical cycling or other loads. So far, a theoretical understanding of these processes is sparse, not to mention predictions of element distributions. The Account concludes with a series of remarks on current challenges in the field and an outlook on the gains that the field would earn from a solid understanding of the underlying processes and a predictive theoretical backing.
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- 2023
14. Nanoparticle-Based Aerogels and Their Prospective Future Applications
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Alexander Eychmüller
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General Energy ,Physical and Theoretical Chemistry ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials - Published
- 2022
15. CO2 Electroreduction on Unsupported PdPt Aerogels: Effects of Alloying and Surface Composition on Product Selectivity
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Justus S. Diercks, Maximilian Georgi, Juan Herranz, Nataša Diklić, Piyush Chauhan, Adam H. Clark, René Hübner, Antoine Faisnel, Qinhao Chen, Maarten Nachtegaal, Alexander Eychmüller, and Thomas J. Schmidt
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Materials Chemistry ,Electrochemistry ,Energy Engineering and Power Technology ,Chemical Engineering (miscellaneous) ,Electrical and Electronic Engineering - Abstract
Due to its unique ability to reduce carbon dioxide (CO2) into CO or formate at high versus low overpotentials, respectively, palladium is a promising catalyst for the electrochemical CO2-reduction reaction (CO2RR). Further improvements aim at increasing its activity and selectivity toward either of these value-added species, while reducing the amount of hydrogen produced as a side product. With this motivation, in this work, we synthesized a range of unsupported, bimetallic PdPt aerogels and pure Pt or Pd aerogels and extensively characterized them using various microscopic and spectroscopic techniques. These revealed that the aerogels’ porous web consists of homogenous alloys of Pt and Pd, with palladium and platinum being present on their surface for all compositions. The subsequent determination of these aeorgels’ CO2RR performance unveiled that the high activity of these Pt surface atoms toward hydrogen evolution causes all PdPt alloys to favor this reaction over CO2 reduction. In the case of the pure Pd aerogel, although, its unsupported nature leads to a suppression of H2 evolution and a concomitant increase in the selectivity toward CO when compared to a commercial, carbon-supported Pd-nanoparticle catalyst.
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- 2022
16. Effects of the soft matrices in dielectric elastomer actuator electrodes on their actuation performance
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Jianan Yi, Volodymyr Shamraienko, Alexander Eychmüller, Iain A. Anderson, Andreas Richter, and Markus Henke
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- 2023
17. Spectroscopy vs. Electrochemistry: Catalyst Layer Thickness Effects on Operando/In Situ Measurements
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Justus S. Diercks, Juan Herranz, Kathrin Ebner, Nataša Diklić, Maximilian Georgi, Piyush Chauhan, Adam H. Clark, Maarten Nachtegaal, Alexander Eychmüller, and Thomas J. Schmidt
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Palladium Hydride ,Electrochemistry ,General Medicine ,General Chemistry ,Catalyst Loading ,Catalysis ,Electrode Thickness ,Spectroscopy - Abstract
In recent years, operando/in situ X-ray absorption spectroscopy (XAS) has become an important tool in the electrocatalysis community. However, the high catalyst loadings often required to acquire XA-spectra with a satisfactory signal-to-noise ratio frequently imply the use of thick catalyst layers (CLs) with large ion- and mass-transport limitations. To shed light on the impact of this variable on the spectro-electrochemical results, in this study we investigate Pd-hydride formation in carbon-supported Pd-nanoparticles (Pd/C) and an unsupported Pd-aerogel with similar Pd surface areas but drastically different morphologies and electrode packing densities. Our in situ XAS and rotating disk electrode (RDE) measurements with different loadings unveil that the CL-thickness largely determines the hydride formation trends inferred from spectro-electrochemical experiments, therewith calling for the minimization of the CL-thickness in such experiments and the use of complementary thin-film control measurements., Angewandte Chemie. International Edition, 62 (16), ISSN:1433-7851, ISSN:1521-3773, ISSN:0570-0833
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- 2023
18. Optimizing the Pd Sites in Pure Metallic Aerogels for Efficient Electrocatalytic H 2 O 2 Production
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Xin Zhang, Cui Wang, Kai Chen, Adam H. Clark, René Hübner, Jinhua Zhan, Liang Zhang, Alexander Eychmüller, and Bin Cai
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Mechanics of Materials ,Mechanical Engineering ,General Materials Science - Published
- 2023
19. Self-assembly of nanocrystals into strongly electronically coupled all-inorganic supercrystals
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Igor Coropceanu, Eric M. Janke, Joshua Portner, Danny Haubold, Trung Dac Nguyen, Avishek Das, Christian P. N. Tanner, James K. Utterback, Samuel W. Teitelbaum, ¸ Margaret H. Hudson, Nivedina A. Sarma, Alex M. Hinkle, Christopher J. Tassone, Alexander Eychmüller, David T. Limmer, Monica Olvera de la Cruz, Naomi S. Ginsberg, and Dmitri V. Talapin
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Multidisciplinary - Abstract
Colloidal nanocrystals of metals, semiconductors, and other functional materials can self-assemble into long-range ordered crystalline and quasicrystalline phases, but insulating organic surface ligands prevent the development of collective electronic states in ordered nanocrystal assemblies. We reversibly self-assembled colloidal nanocrystals of gold, platinum, nickel, lead sulfide, and lead selenide with conductive inorganic ligands into supercrystals exhibiting optical and electronic properties consistent with strong electronic coupling between the constituent nanocrystals. The phase behavior of charge-stabilized nanocrystals can be rationalized and navigated with phase diagrams computed for particles interacting through short-range attractive potentials. By finely tuning interparticle interactions, the assembly was directed either through one-step nucleation or nonclassical two-step nucleation pathways. In the latter case, the nucleation was preceded by the formation of two metastable colloidal fluids.
- Published
- 2022
20. Self-Supported Three-Dimensional Quantum Dot Aerogels as a Promising Photocatalyst for CO2 Reduction
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Guocan Jiang, Jin Wang, Nuoya Li, René Hübner, Maximilian Georgi, Bin Cai, Zhengquan Li, Vladimir Lesnyak, Nikolai Gaponik, and Alexander Eychmüller
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General Chemical Engineering ,Materials Chemistry ,General Chemistry - Abstract
With the merits of quantum dots (QDs) (e.g., high molar extinction coefficient, strong visible light absorption, large specific surface area, and abundant functional surface active sites) and aerogels (e.g., self-supported architectures, porous network), semiconductor QD aerogels show great prospect in photocatalytic applications. However, typical gelation methods rely on oxidative treatments of QDs. Moreover, the remaining organic ligands (e.g., mercaptoacids) are still present on the surface of gels. Both these factors inhibit the activity of such photocatalysts, hampering their widespread use. Herein, we present a facile 3D assembly of II−VI semiconductor QDs capped with inorganic (NH4)2S ligands into aerogels using H2O as a dispersion solvent. Without any sacrificial agents, the resulting CdSe QD aerogels achieve a high CO generation rate of 15 μmol g-1 h-1, which is 12-fold higher than that of pristine-aggregated QD powders. Our work not only provides a facile strategy to fabricate QD aerogels but also offers a platform for designing advanced aerogel-based photocatalysts.
- Published
- 2022
21. An Undergraduate Project on the Assembly of Langmuir–Blodgett Films of Colloidal Particles
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Purnesh Chattopadhyay, Linlin Wang, Alexander Eychmüller, and Juliane Simmchen
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General Chemistry ,Education - Published
- 2022
22. Controllable electrostatic manipulation of structure building blocks in noble metal aerogels
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Wei Wei, René Hübner, Maximilian Georgi, Cui Wang, Xiaodong Wu, and Alexander Eychmüller
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Chemistry (miscellaneous) ,General Materials Science - Abstract
The important role of structure homogeneity in three-dimensional network nanostructures serving as noble metal aerogels (NMAs) has attracted extensive attention in the field of electrochemistry in the last two decades, whereas a comprehensive study of tailoring skeleton units and element distributions in NMAs is still lacking. Herein, a new modulation strategy to easily prepare multiscale NMAs with tunable composition is developed by utilizing the electrostatic interaction between oppositely charged colloidal metal nanoparticles. The modulation rule of the chemical distribution in bimetallic aerogels leads to the construction of the as-tailored double skeleton aerogels for the first time. Considering their specific structures, the intrinsic and exceptional catalytic and electrocatalytic performances of NMAs were investigated. This study optimizes the structure homogeneity of noble metal aerogels by investigating nanoparticle–ligand interactions and provides further proof of their exceptional electrocatalytic capabilities.
- Published
- 2022
23. Bimetallic Pt−Ni Two-Dimensional Interconnected Networks: Developing Self-Assembled Materials for Transparent Electronics
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Pavel Khavlyuk, Andrei Mitrofanov, Volodymyr Shamraienko, René Hübner, Johannes Kresse, Konstantin B. L. Borchert, and Alexander Eychmüller
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General Chemical Engineering ,Materials Chemistry ,General Chemistry - Abstract
Continuous advancements in science and technology in the field of flexible devices encourage researchers to dedicate themselves to seeking candidates for new flexible transparent conductive films (FTCFs). Our recently developed two-dimensional (2D) metal aerogels are considered as a new class of FTCFs. Here, we describe a new large-scale self-assembly synthesis of bimetallic Pt-Ni 2D metal aerogels with controllable morphology during the synthesis. The obtained 2D aerogels require only a low quantity of precursors for the synthesis of percolating nanoscale networks with areas of up to 6 cm2 without the need of an additional drying step. Stacks of the obtained monolayer structures display low sheet resistances (down to 270 Ω/sq), while decreasing the optical transparency. In perspective, the 2D bimetallic Pt-Ni aerogels not only enrich the structural diversity of metal aerogels but also bring forth new materials for further applications in flexible electronics and electrocatalysis with reduced costs of production.
- Published
- 2023
24. Polyol-Assisted Synthesis of Copper Particles
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Alexander Eychmüller, Purnesh Chattopadhyay, Thomas Gemming, and Juliane Simmchen
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chemistry.chemical_classification ,General Energy ,Materials science ,Chemical engineering ,Polyol ,chemistry ,chemistry.chemical_element ,Physical and Theoretical Chemistry ,Copper ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials - Published
- 2021
25. Influence of drying technique on Pt/In2O3 aerogels for methanol steam reforming
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Lukas Thoni, Nadia Metzkow, and Alexander Eychmüller
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Biomaterials ,Materials Chemistry ,Ceramics and Composites ,General Chemistry ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials - Abstract
In this paper we present a comparison of aerogels which are dried under different conditions. Of those, most important are the solvent, temperature, and pressure. Criteria of comparison rely mostly on results from analysis of nitrogen adsorption experiments, as well as transmission electron microscopy imaging. Platinum loaded indium oxide aerogels were picked as a model system for this study as they can be used as highly effective heterogeneous catalysts in methanol steam reforming. The compared drying methods include supercritical drying from CO2, supercritical CO2 - ethanol mixture, freeze drying from tert-butanol and ambient conditions drying from acetone and 1-Methoxyheptafluoropropane. High porosities and large specific surface areas can be achieved via supercritical, freeze- and ambient conditions drying, while retaining the original gel morphology in this system for most methods except freeze drying and ambient conditions drying from acetone.
- Published
- 2022
26. Interparticle Charge-Transport-Enhanced Electrochemiluminescence of Quantum-Dot Aerogels
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Xuwen Gao, Guocan Jiang, Cunyuan Gao, Anatol Prudnikau, René Hübner, Jinhua Zhan, Guizheng Zou, Alexander Eychmüller, and Bin Cai
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General Chemistry ,General Medicine ,Catalysis - Abstract
Electrochemiluminescence (ECL) represents a widely explored technique to generate light, in which the emission intensity relies critically on the charge-transfer reactions between electrogenerated radicals. Two types of charge-transfer mechanisms have been postulated for ECL generation, but the manipulation and effective probing of these routes remain a fundamental challenge. Here, we demonstrate the design of quantum dot (QD) aerogels as novel ECL luminophores via a versatile water-induced gelation strategy. The strong electronic coupling between adjacent QDs enables efficient charge transport within the aerogel network, leading to the generation of highly efficient ECL based on the selectively improved interparticle charge-transfer route. This mechanism is further verified by designing CdSe-CdTe mixed QD aerogels, where the two mechanistic routes are clearly decoupled for ECL generation. We anticipate our work will advance the fundamental understanding of ECL and prove useful for designing next-generation QD-based devices.
- Published
- 2022
27. Tribute for Professor Horst Weller
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Alexander Eychmüller, Alf Mews, and Paul Mulvaney
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General Energy ,Physical and Theoretical Chemistry ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials - Published
- 2022
28. Accurate wavelength tracking by exciton spin mixing
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Anton Kirch, Toni Bärschneider, Tim Achenbach, Felix Fries, Max Gmelch, Robert Werberger, Chris Guhrenz, Aušra Tomkevičienė, Johannes Benduhn, Alexander Eychmüller, Karl Leo, Sebastian Reineke, and „Wiley' grupė
- Subjects
transient photocurrent ,Mechanical Engineering ,organic room-temperature phosphorescence ,FOS: Physical sciences ,Physics::Optics ,Applied Physics (physics.app-ph) ,Physics - Applied Physics ,colloidal quantum dots ,organic wavelength sensors ,dual-state Forster resonance energy transfer ,Mechanics of Materials ,General Materials Science ,Optics (physics.optics) ,Physics - Optics - Abstract
Wavelength-discriminating systems typically consist of heavy benchtop-based instruments, comprising diffractive optics, moving parts, and adjacent detectors. For simple wavelength measurements, such as lab-on-chip light source calibration or laser wavelength tracking, which do not require polychromatic analysis and cannot handle bulky spectroscopy instruments, lightweight, easy-to-process, and flexible single-pixel devices are attracting increasing attention. Here, a device is proposed for monotonously transforming wavelength information into the time domain with room-temperature phosphorescence at the heart of its functionality, which demonstrates a resolution down to 1 nm and below. It is solution-processed from a single host-guest system comprising organic room-temperature phosphors and colloidal quantum dots. The share of excited triplet states within the photoluminescent layer is dependent on the excitation wavelength and determines the afterglow intensity of the film, which is tracked by a simple photodetector. Finally, an all-organic thin-film wavelength sensor and two applications are demonstrated where this novel measurement concept successfully replaces a full spectrometer.
- Published
- 2022
29. Unprecedented Catalytic Activity and Selectivity in Methanol Steam Reforming by Reactive Transformation of Intermetallic In–Pt Compounds
- Author
-
Benjamin Klemmed, Alexander Eychmüller, Marc Heggen, Lukas Thoni, Nicolas Köwitsch, Marc Armbrüster, Albrecht Benad, and Paul Paciok
- Subjects
Materials science ,Intermetallic ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Small molecule ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Catalysis ,Steam reforming ,chemistry.chemical_compound ,Hydrogen storage ,Hydrogen carrier ,General Energy ,Chemical engineering ,chemistry ,ddc:530 ,Methanol ,Physical and Theoretical Chemistry ,0210 nano-technology ,Selectivity - Abstract
Hydrogen storage in the form of small molecules and subsequent release are foreseen to play a fundamental role in future energy systems or carbon cycles. Methanol is an ideal hydrogen carrier due to the high H/C ratio, the lack of C–C bonds, and being liquid under ambient conditions. Methanol steam reforming is an advantageous reaction for the release of the chemically bound hydrogen. Pd- or Pt-based intermetallic compounds have shown to be CO2-selective and long-term stable catalytic materials. However, an intrinsic understanding of the underlying processes is still lacking. In this study, we show that the redox activity in the In–Pt system can be steered by gas-phase changes and leads to highly active catalytic materials at 300 °C [1500 mol (H2)/(mol (Pt) × h)] with an excellent CO2 selectivity of 99.5%, thus clearly outperforming previous materials. Reactive transformations between In2Pt, In3Pt2, and In2O3 have been identified to cause the high selectivity. Redox activity of intermetallic compounds as part of the catalytic cycle was previously unknown and adds an understanding to the concept of different adsorption sites.
- Published
- 2021
30. Bimetallic Pt‐Hg Aerogels for Electrocatalytic Upgrading of Ethanol to Acetate
- Author
-
Xin Zhang, Tao Wang, Cui Wang, René Hübner, Alexander Eychmüller, Jinhua Zhan, and Bin Cai
- Subjects
Biomaterials ,General Materials Science ,General Chemistry ,Biotechnology - Published
- 2023
31. A Roadmap for 3D Metal Aerogels: Materials Design and Application Attempts
- Author
-
Yue Hu, René Hübner, Xiaodi Jiang, Alexander Eychmüller, and Ran Du
- Subjects
Engineering ,business.industry ,Design elements and principles ,General Materials Science ,Nanotechnology ,Materials design ,business ,Porous network - Abstract
Summary Armed with merits of the metals (e.g., electrical conductivity, catalytic activity, and plasmonic properties) and aerogels (e.g., monolithic structure, porous network, and large specific surface area), metal aerogels (MAs) have stood out as a new class of porous materials in the last decade. With unparalleled potential in electrocatalysis, plasmonics, and sensing, they are envisaged to revolutionize the energy- and detection-related application fields. However, MA development is severely retarded by the lack of a sufficient material basis. Suffering from the ambiguous understanding of formation mechanisms, big challenges remain for tailoring MAs for task-specific applications. By surveying state-of-the-art developments, this review strives to summarize design principles and arouse interest in broad scientific communities. Moreover, critical challenges and opportunities are highlighted to provide a research roadmap for this young yet promising field.
- Published
- 2021
32. Rapid synthesis of gold–palladium core–shell aerogels for selective and robust electrochemical CO2 reduction
- Author
-
Ran Du, Yue Hu, Lin Zhou, Geng Xue, Hengbo Wu, René Hübner, Alexander Eychmüller, and Wei Jin
- Subjects
Materials science ,Renewable Energy, Sustainability and the Environment ,chemistry.chemical_element ,Aerogel ,General Chemistry ,engineering.material ,Overpotential ,Electrocatalyst ,Catalysis ,Chemical engineering ,chemistry ,Desorption ,engineering ,General Materials Science ,Noble metal ,Faraday efficiency ,Palladium - Abstract
Noble metal aerogels (NMAs), one class of the youngest members in the aerogel family, have drawn increasing attention in the last decade. Featuring the high catalytic activity of noble metals and a 3D self-supported porous network of the aerogels, they have displayed profound potential for electrocatalysis. However, considerable challenges reside in the rapid fabrication of NMAs with a well-tailored architecture, constraining the manipulation of their electrochemical properties for optimized performance. Here, a disturbance-assisted dynamic shelling strategy is developed, generating self-supported Au–Pd core–shell gels within 10 min. Based on suitable activation and desorption energies of the involved species as suggested by theoretical calculations, the Au–Pd core–shell aerogel manifests outstanding CO selectivity and stability at low overpotential (faradaic efficiency > 98% at −0.5 V vs. RHE over 12 hours) for the electrochemical CO2 reduction reaction (CO2RR). The present strategy offers a new perspective to facilely design architecture-specified high-performance electrocatalysts for the CO2RR.
- Published
- 2021
33. Proving a Paradigm in Methanol Steam Reforming: Catalytically Highly Selective InxPdy/In2O3 Interfaces
- Author
-
Lukas Thoni, Isabel Köwitsch, Paul Paciok, Marc Heggen, Albrecht Benad, Nicolas Köwitsch, Michael Mehring, Marc Armbrüster, Alexander Eychmüller, and Benjamin Klemmed
- Subjects
Materials science ,Hydrogen ,010405 organic chemistry ,Intermetallic ,chemistry.chemical_element ,Aerogel ,General Chemistry ,010402 general chemistry ,Highly selective ,Heterogeneous catalysis ,01 natural sciences ,Catalysis ,0104 chemical sciences ,Steam reforming ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,ddc:540 ,Methanol - Abstract
Methanol steam reforming provides clean hydrogen by onboard production, which can directly be used for fuel cell applications–while using appropriate catalysts. InxPdy/In2O3 aerogels exhibit excell...
- Published
- 2020
34. Tailoring the Morphology and Fractal Dimension of 2D Mesh‐like Gold Gels
- Author
-
Maximilian Georgi, Swetlana Jungblut, Alexander Eychmüller, and Karl Hiekel
- Subjects
Phase boundary ,Materials science ,Fabrication ,Silicon ,Stacking ,chemistry.chemical_element ,Nanotechnology ,02 engineering and technology ,Glassy carbon ,010402 general chemistry ,01 natural sciences ,Fractal dimension ,Catalysis ,Research Articles ,Sheet resistance ,chemistry.chemical_classification ,2D structures ,010405 organic chemistry ,Aerogels ,General Medicine ,General Chemistry ,Polymer ,gold ,021001 nanoscience & nanotechnology ,fractal structures ,0104 chemical sciences ,chemistry ,0210 nano-technology ,Research Article - Abstract
As there is a great demand of 2D metal networks, especially out of gold for a plethora of applications we show a universal synthetic method via phase boundary gelation which allows the fabrication of networks displaying areas of up to 2 cm2. They are transferred to many different substrates: glass, glassy carbon, silicon, or polymers such as PDMS. In addition to the standardly used web thickness, the networks are parametrized by their fractal dimension. By variation of experimental conditions, we produced web thicknesses between 4.1 nm and 14.7 nm and fractal dimensions in the span of 1.56 to 1.76 which allows to tailor the structures to fit for various applications. Furthermore, the morphology can be tailored by stacking sheets of the networks. For each different metal network, we determined its optical transmission and sheet resistance. The obtained values of up to 97 % transparency and sheet resistances as low as 55.9 Ω/sq highlight the great potential of the obtained materials., Stacked fractals: 2D gold mesh‐like gels with areas of up to 2 cm2 are synthesized via phase boundary gelation. The structures are described as fractals. By variation of experimental details, web thicknesses between 4.1 nm and 14.7 nm are achieved. The networks can be stacked or transferred to different substrates.
- Published
- 2020
35. Semiconductor Nanocrystal Heterostructures: Near-Infrared Emitting PbSe-Tipped CdSe Tetrapods
- Author
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Vladimir Lesnyak, Peng Zhang, Mahdi Samadi Khoshkhoo, Alexander Eychmüller, Annett Reichhelm, Karl Hiekel, and Beatriz Martín-García
- Subjects
Materials science ,Condensed Matter::Other ,business.industry ,General Chemical Engineering ,Near-infrared spectroscopy ,Physics::Optics ,Heterojunction ,02 engineering and technology ,General Chemistry ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Condensed Matter::Materials Science ,Semiconductor ,Materials Chemistry ,Semiconductor nanocrystals ,Optoelectronics ,0210 nano-technology ,business ,Astrophysics::Galaxy Astrophysics - Abstract
We report on a near-infrared (NIR) emitting semiconductor nanocrystal (NC) heterostructure with tunable optical properties. This heterostructure is built of two different semiconductor sections in ...
- Published
- 2020
36. Freeze–Thaw‐Promoted Fabrication of Clean and Hierarchically Structured Noble‐Metal Aerogels for Electrocatalysis and Photoelectrocatalysis
- Author
-
Jan-Ole Joswig, Lin Zhou, Ran Du, Wei Wei, Yue Hu, René Hübner, and Alexander Eychmüller
- Subjects
Materials science ,Nanostructure ,Fabrication ,Nanotechnology ,engineering.material ,010402 general chemistry ,Electrochemistry ,Electrocatalyst ,01 natural sciences ,sol–gel process ,Catalysis ,nanostructures ,Research Articles ,Sol-gel ,010405 organic chemistry ,General Medicine ,General Chemistry ,gels ,0104 chemical sciences ,Electrochemistry | Hot Paper ,electrochemistry ,engineering ,Photocatalysis ,Noble metal ,photocatalysis ,Research Article - Abstract
Noble‐metal aerogels (NMAs) have drawn increasing attention because of their self‐supported conductive networks, high surface areas, and numerous optically/catalytically active sites, enabling their impressive performance in diverse fields. However, the fabrication methods suffer from tedious procedures, long preparation times, unavoidable impurities, and uncontrolled multiscale structures, discouraging their developments. By utilizing the self‐healing properties of noble‐metal aggregates, the freezing‐promoted salting‐out behavior, and the ice‐templating effect, a freeze–thaw method is crafted that is capable of preparing various hierarchically structured noble‐metal gels within one day without extra additives. In light of their cleanliness, the multi‐scale structures, and combined catalytic/optical properties, the electrocatalytic and photoelectrocatalytic performance of NMAs are demonstrated, which surpasses that of commercial noble‐metal catalysts., Coming in from the cold: By utilizing the freezing‐promoted salting‐out and the ice‐templating effect, a freeze–thaw method is developed to fabricate various noble‐metal hydrogels within one day. In light of their catalytically/optically active sites and multi‐scale structures, the impressive performance for electrocatalysis and photoelectrocatalysis is demonstrated for electro‐oxidation of ethanol.
- Published
- 2020
37. General Colloidal Synthesis of Transition-Metal Disulfide Nanomaterials as Electrocatalysts for Hydrogen Evolution Reaction
- Author
-
Christian Meerbach, Vladimir Lesnyak, René Hübner, Hu Young Jeong, Alexander Eychmüller, Christoph Bauer, Daniel Spittel, Hyeon Suk Shin, Denise Erb, Youngjin Park, and Benjamin Klemmed
- Subjects
Materials science ,Disulfide bond ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrocatalyst ,01 natural sciences ,0104 chemical sciences ,Nanomaterials ,Metal ,Transition metal ,visual_art ,Monolayer ,visual_art.visual_art_medium ,General Materials Science ,Hydrogen evolution ,0210 nano-technology ,Colloidal synthesis - Abstract
The material-efficient monolayers of transition-metal dichalcogenides (TMDs) are a promising class of ultrathin nanomaterials with properties ranging from insulating through semiconducting to metallic, opening a wide variety of their potential applications from catalysis and energy storage to optoelectronics, spintronics, and valleytronics. In particular, TMDs have a great potential as emerging inexpensive alternatives to noble metal-based catalysts in electrochemical hydrogen evolution. Herein, we report a straightforward, low-cost, and general colloidal synthesis of various 2D transition-metal disulfide nanomaterials, such as MoS2, WS2, NiSx, FeSx, and VS2, in the absence of organic ligands. This new preparation route provides many benefits including relatively mild reaction conditions, high reproducibility, high yields, easy upscaling, no post-thermal annealing/treatment steps to enhance the catalytic activity, and, finally, especially for molybdenum disulfide nanosheets, high activity in the hydrogen evolution reaction. To underline the universal application of the synthesis, we prepared mixed CoxMo1-xS2 nanosheets in one step to optimize the catalytic activity of pure undoped MoS2, which resulted in an enhanced hydrogen evolution reaction performance characterized by onset potentials as low as 134 mV and small Tafel slopes of 55 mV/dec.
- Published
- 2020
38. Promoting the Electrocatalytic Performance of Noble Metal Aerogels by Ligand‐Directed Modulation
- Author
-
Ran Du, Sven Reichenberger, Stephan Barcikowki, Guocan Jiang, Swen Zerebecki, René Hübner, Alexander Eychmüller, Xuelin Fan, Yue Hu, and Galina Marzum
- Subjects
Materials science ,Chemie ,Nanotechnology ,noble metals ,engineering.material ,ligand ,010402 general chemistry ,Electrocatalyst ,01 natural sciences ,Catalysis ,electrocatalysis ,Metal nanoparticles ,Research Articles ,aerogels ,010405 organic chemistry ,Ligand ,General Medicine ,General Chemistry ,laser ,0104 chemical sciences ,engineering ,Noble Metal Aerogels ,Noble metal ,Porous medium ,Research Article - Abstract
Noble metal aerogels (NMAs) are an emerging class of porous materials. Embracing nano‐sized highly‐active noble metals and porous structures, they display unprecedented performance in diverse electrocatalytic processes. However, various impurities, particularly organic ligands, are often involved in the synthesis and remain in the corresponding products, hindering the investigation of the intrinsic electrocatalytic properties of NMAs. Here, starting from laser‐generated inorganic‐salt‐stabilized metal nanoparticles, various impurity‐free NMAs (Au, Pd, and Au‐Pd aerogels) were fabricated. In this light, we demonstrate not only the intrinsic electrocatalytic properties of NMAs, but also the prominent roles played by ligands in tuning electrocatalysis through modulating the electron density of catalysts. These findings may offer a new dimension to engineer and optimize the electrocatalytic performance for various NMAs and beyond., Worth its weight in gold: Starting from laser‐generated inorganic‐salt‐stabilized metal nanoparticles, various impurity‐free noble metal aerogels are fabricated, allowing the investigation of their intrinsic properties. Moreover, prominent roles played by ligands, which are interpreted from electron transfer between NMAs and respective ligands, are demonstrated, offering a new dimension to engineer electrocatalytic properties of broad materials.
- Published
- 2020
39. Largely boosted methanol electrooxidation using ionic liquid/PdCu aerogels via interface engineering
- Author
-
Songlin Zhang, Wenling Gu, Zhao Liu, Xin Luo, Jun Chen, Chengzhou Zhu, Zhixiang Cai, Xiaoqian Wei, Hengjia Wang, Weiwei Cai, Bo Z. Xu, Yu Wu, and Alexander Eychmüller
- Subjects
Materials science ,Process Chemistry and Technology ,Kinetics ,Redox ,Catalysis ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Mechanics of Materials ,Chemisorption ,Ionic liquid ,General Materials Science ,Density functional theory ,Methanol ,Electrical and Electronic Engineering ,Methanol fuel - Abstract
Tuning electrocatalysts via interface engineering is widely adopted as a valid way to manipulate the electrocatalytic activity. Herein, the interface engineering of PdCu aerogels is successfully achieved by the integration of an ionic liquid (IL), which not only accelerates the gelation kinetics but also leads to the modulation of the interface electronic properties, enabling IL functionalized PdCu aerogels (IL/PdCu) as advanced electrocatalysts for the methanol oxidation reaction (MOR) with splendid electrocatalytic activity. Density functional theory (DFT) calculations also demonstrate that IL-involved interface engineering dramatically reduces the chemisorption energy of CO-containing intermediates and thus significantly boosts the MOR performance. Furthermore, direct methanol fuel cells (DMFCs) using an IL/Pd3Cu1 anode catalyst exhibit a higher power density than those containing Pd3Cu1 and commercial Pd catalysts. This work highlights the superiority of designing advanced electrocatalysts by interface engineering.
- Published
- 2020
40. Hybrid Plasmonic–Aerogel Materials as Optical Superheaters with Engineered Resonances
- Author
-
Alexander O. Govorov, Zhiming Wang, Maximilian Georgi, Lucas V. Besteiro, Albrecht Benad, Benjamin Klemmed, and Alexander Eychmüller
- Subjects
Work (thermodynamics) ,Materials science ,Radiation ,010402 general chemistry ,01 natural sciences ,7. Clean energy ,Catalysis ,photoheaters ,Energy transformation ,Research Articles ,Plasmon ,Energy Conversion ,Thermal equilibrium ,010405 organic chemistry ,business.industry ,Aerogel ,General Chemistry ,gold nanorods ,0104 chemical sciences ,hybrid aerogel ,Optoelectronics ,Nanorod ,business ,Hybrid material ,surface plasmon resonance ,Research Article - Abstract
Solar radiation is a versatile source of energy, convertible to different forms of power. A direct path to exploit it is the generation of heat, for applications including passive building heating, but it can also drive secondary energy‐conversion steps. We present a novel concept for a hybrid material which is both strongly photo‐absorbing and with superior characteristics for the insulation of heat. The combination of that two properties is rather unique, and make this material an optical superheater. To realize such a material, we are combining plasmonic nanoheaters with alumina aerogel. The aerogel has the double function of providing structural support for plasmonic nanocrystals, which serve as nanoheaters, and reducing the diffusion rate of the heat generated by them, resulting in large local temperature increases under a relatively low radiation intensity. This work includes theoretical discussion on the physical mechanisms impacting the system's balanced thermal equilibrium., White light, white heat: Gold nanorods (AuNRs) embedded into highly insulating alumina aerogel pellets give a hybrid system that has a tremendous light to heat conversion performance. The AuNRs withstand the high local temperatures (175 °C) with little to no melting. The system allows the design and modelling of novel concepts for photoheaters.
- Published
- 2019
41. Hybrid Plasmonic–Aerogel Materials as Optical Superheaters with Engineered Resonances
- Author
-
Benjamin Klemmed, Lucas V. Besteiro, Albrecht Benad, Maximilian Georgi, Zhiming Wang, Alexander Govorov, and Alexander Eychmüller
- Subjects
02 engineering and technology ,General Medicine ,010402 general chemistry ,021001 nanoscience & nanotechnology ,0210 nano-technology ,01 natural sciences ,7. Clean energy ,0104 chemical sciences - Published
- 2019
42. Electrochemical Surface Area Quantification, CO
- Author
-
Piyush, Chauhan, Karl, Hiekel, Justus S, Diercks, Juan, Herranz, Viktoriia A, Saveleva, Pavel, Khavlyuk, Alexander, Eychmüller, and Thomas J, Schmidt
- Abstract
The efficient scale-up of CO
- Published
- 2021
43. Assembling graphene aerogel hollow fibres for solar steam generation
- Author
-
Guangyong Li, Dan Fang, Guo Hong, Alexander Eychmüller, Xuetong Zhang, and Wenhui Song
- Subjects
Polymers and Plastics ,Mechanics of Materials ,Materials Chemistry ,Ceramics and Composites - Published
- 2022
44. Morphogenesis of Magnetite Mesocrystals: Interplay Between Nanoparticle Morphology and Solvation Shell
- Author
-
Julian Brunner, Britta Maier, Sabrina L. J. Thomä, Felizitas Kirner, Igor Baburin, Dmitry Lapkin, Rose Rosenberg, Sebastian Sturm, Dameli Assalauova, Jerome Carnis, Young Yong Kim, Zhe Ren, Fabian Westermeier, Sebastian Theiss, Horst Borrmann, Sebastian Polarz, Alexander Eychmüller, Axel Lubk, Ivan Vartanyants, Helmut Cölfen, Mirijam Zobel, Elena Sturm, and Elena Sturm (née Rosseeva)
- Abstract
In this study, faceted mesocrystals have been assembled from the dispersion of truncated cubic-shaped iron oxide nanoparticles stabilized by oleic acid (OA) molecules using the non-solvent “gas phase diffusion technique” into an organic solvent. The effects of synthesis conditions as well as of the nanoparticle size and shape on the structure and morphogenesis of mesocrystals were examined. The interactions of OA capped iron oxide nanoparticles with solvent molecules were probed by analytical ultracentrifugation and double difference pair distribution function analysis. It was shown that the structure of the organic shell significantly depends on the nature and polarity of solvent molecules.
- Published
- 2021
45. Morphogenesis of Magnetite Mesocrystals: Interplay Between Nanoparticle Morphology and Solvation Shell
- Author
-
Helmut Cölfen, Jerome Carnis, Sebastian Sturm, Julian Schlotheuber né Brunner, Mirijam Zobel, Sebastian Polarz, Rose Rosenberg, Sabrina L. J. Thomä, Britta Maier, Felizitas Kirner, Sebastian Theiss, Dameli Assalauova, Young Yong Kim, Horst Borrmann, Axel Lubk, Fabian Westermeier, Dmitry Lapkin, Alexander Eychmüller, Ivan A. Vartanyants, Zhe Ren, Elena V. Sturm, and Igor A. Baburin
- Subjects
Materials science ,Morphology (linguistics) ,High interest ,General Chemical Engineering ,Nanoparticle ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,chemistry.chemical_compound ,Solvation shell ,chemistry ,Chemical engineering ,Materials Chemistry ,Self-assembly ,0210 nano-technology ,Magnetite - Abstract
In this study, faceted mesocrystals have been assembled from the dispersion of truncated cubic-shaped iron oxide nanoparticles stabilized by oleic acid (OA) molecules using the non-solvent “gas phase diffusion technique” into an organic solvent. The effects of synthesis conditions as well as of the nanoparticle size and shape on the structure and morphogenesis of mesocrystals were examined. The interactions of OA capped iron oxide nanoparticles with solvent molecules were probed by analytical ultracentrifugation and double difference pair distribution function analysis. It was shown that the structure of the organic shell significantly depends on the nature and polarity of solvent molecules.
- Published
- 2021
46. Mechanical Characterization of Self-Supported Noble Metal Gel Monoliths
- Author
-
Inga Melnyk, Alexander Eychmüller, Günter K. Auernhammer, Andreas Fery, Karl Hiekel, and Kristian Schneider
- Subjects
General Energy ,Materials science ,engineering ,Noble metal ,Nanotechnology ,Physical and Theoretical Chemistry ,engineering.material ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Characterization (materials science) - Abstract
Noble metal hydro- and aerogels exhibit a variety of unique properties, including large surface areas, ultralow densities, and high porosities. While their potential use in various applications ran...
- Published
- 2019
47. Highly Luminescent and Water-Resistant CsPbBr3–CsPb2Br5 Perovskite Nanocrystals Coordinated with Partially Hydrolyzed Poly(methyl methacrylate) and Polyethylenimine
- Author
-
Xuelin Fan, Chris Guhrenz, Alexander Eychmüller, Sebastian Reineke, Nikolai Gaponik, Christoph Bauer, Guocan Jiang, Anton Kirch, Jin Wang, and Luisa Sonntag
- Subjects
Polyethylenimine ,Materials science ,General Engineering ,General Physics and Astronomy ,Halide ,02 engineering and technology ,Thermal treatment ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Poly(methyl methacrylate) ,0104 chemical sciences ,chemistry.chemical_compound ,Hydrolysis ,chemistry ,Chemical engineering ,Nanocrystal ,visual_art ,visual_art.visual_art_medium ,General Materials Science ,0210 nano-technology ,Luminescence ,Perovskite (structure) - Abstract
All inorganic lead halide perovskite nanocrystals (PNCs) typically suffer from poor stability against moisture and UV radiation as well as degradation during thermal treatment. The stability of PNC...
- Published
- 2019
48. Highly Conductive Copper Selenide Nanocrystal Thin Films for Advanced Electronics
- Author
-
Mahdi Samadi Khoshkhoo, Josephine F. L. Lox, Hans Lesny, Yvonne Joseph, Alexander Eychmüller, Andreas Koitzsch, and Vladimir Lesnyak
- Subjects
Nanocrystal ,Electrical resistivity and conductivity ,Materials Chemistry ,Electrochemistry ,Nanotechnology ,Self-assembly ,Electronics ,Thin film ,Copper selenide ,Surface plasmon resonance ,Electrical conductor ,Electronic, Optical and Magnetic Materials - Abstract
Investigation of the influence of the nanocrystal (NC) surface chemistry on the (opto)electronic properties of NC-based thin films is of paramount importance for their further application in variou...
- Published
- 2019
49. Emerging Noble Metal Aerogels: State of the Art and a Look Forward
- Author
-
Ran Du, Xinyi Jin, Alexander Eychmüller, Xuelin Fan, René Hübner, and Yue Hu
- Subjects
engineering ,Structure control ,General Materials Science ,Nanotechnology ,Noble metal ,engineering.material ,Grand Challenges - Abstract
Noble metal aerogels (NMAs), as the most important class of noble metal foams (NMFs), appear as emerging functional porous materials in the field of materials science. Combining the irreplaceable roles of noble metals in certain scenarios, as well as monolithic and porous features of aerogels, NMAs can potentially revolutionize diverse fields, such as catalysis, plasmonics, and biology. Despite profound progress, grand challenges remain in their fabrication process, including the efficient structure control, the comprehensive understanding of the formation mechanisms, and the generality of the fabrication strategies, thus inevitably retarding the material design and optimization. This Perspective focuses on the key progress, especially of the fabrication strategies for NMAs during the last two decades, while other NMFs are also succinctly introduced. Challenges and opportunities are summarized to highlight the unexploited space and future directions in expectation of stimulating the broad interest of interdisciplinary scientists.
- Published
- 2019
50. Influence of the average molar mass of poly(N-vinylpyrrolidone) on the dimensions and conductivity of silver nanowires
- Author
-
Luisa Sonntag, Jannick M. Sonntag, Rainer Jordan, Ludwig Bormann, Dhriti Sundar Ghosh, Nikolai Gaponik, Karl Leo, Alexander Eychmüller, Franziska Eichler, and Nelli Weiß
- Subjects
chemistry.chemical_classification ,Molar mass ,Materials science ,N-Vinylpyrrolidone ,General Physics and Astronomy ,02 engineering and technology ,Conductivity ,Silver nanowires ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Chain length ,chemistry.chemical_compound ,Reaction temperature ,chemistry ,Polyol ,Chemical engineering ,Electrode ,Physical and Theoretical Chemistry ,0210 nano-technology - Abstract
We investigate the influence of the average molar mass (Mw) of the capping agent poly(N-vinylpyrrolidone) (PVP) on the conductivity of a silver nanowire (AgNW) network. During the polyol process, the chain length of PVP is known to influence the AgNW diameters and lengths. By altering the reaction temperature and time and using PVP of different chain lengths, we synthesized AgNWs with varying diameters, lengths and PVP coverage. The obtained plethora of AgNWs is the basis for conductivity investigations of networks made of AgNWs with a diameter of either 60 nm or 80 nm. The results show a negative influence of long-chain PVP on the conductivity of the subsequent network if 60 nm thick AgNWs are employed. Overall, we obtain well performing AgNW transparent electrodes on glass with RS = 24.4 Ω sq-1 at 85.5%T550nm.
- Published
- 2019
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