Transfer of Individual Micro- and Nanoparticles for High- Precision 3D Analysis Using 360° Electron Tomography

A versatile approach is demonstrated, providing a general routine for an extensive and advanced 3D characterization of individually selected micro- and nanoparticles, enabling the combination of complementary and scale-bridging techniques. Quintessential to the method is the transfer of individual particles onto tailored tips using a conventional scanning electron microscope equipped with a suitable micromanipulator. The method enables a damage- and contamination-free preparation of freestanding particles. This is of significant importance for applications addressing the measurement of structural, physical, and chemical properties of specifically selected particles, such as 360° electron tomography, atom probe tomography, nano X-ray tomography, or optical near-field measurements. In this context, the method is demonstrated for 360° electron tomography of micro-/macroporous zeolite particles with sizes in the micrometer range and mesoporous alpha-hematite nanoparticles exhibiting sizes of 50–100 nm, including detailed pre- and postcharacterization on the nanoscale.“Deutsche Forschungsgemeinschaft” (DFG) within the framework of the SPP 1570 (project DFG SP 648/4-3 “3D analysis of complex pore structures using ET and high-resolution TEM”) and the research training group GRK 1896 (“In situ Microscopy with Electrons, X-rays and Scanning Probes”) as well as through the Cluster of Excellence “Engineering of Advanced Materials” at the Friedrich-Alexander-Universität Erlangen-Nürnberg (Germany)FIBJulian Losche

Quantifying surface properties of silica particles by combining Hansen Parameters and Reichardt's Dye indicator data

To obtain quantitative understanding of the effects of a chemisorbed organic modification on the surface of particles, the use of Reichardt's dye (RD) and Hansen solubility parameter (HSP) is discussed, whereby the S should be understood in terms of “similarity” rather than solubility as dispersibility is in focus. Silica nanoparticles modified to different extents with a medium chain silane including completely hydrophilic and hydrophobic particles are chosen. During spray‐drying such particles form fully redispersible micro‐raspberry superstructures. After qualitative estimations of the particles' polarity based on measuring both immersion time and ability of modified particles to stabilize oil–water emulsions, surface properties are quantified by HSP and RD. With increasing hydrophobicity, i.e., increasing amount of silane at the surface, all three contributions to HSP change. At the same time, RD analysis reveals that the normalized solvent polarity parameter decreases progressively. HSP and RD analysis are in good agreement, giving strong confidence on each method applied individually. This work demonstrates that after noticeable attempts for combined solubility parameters in case of molecules, carbon allotropes, and gelators, such studies can be extended toward functional (nano)particles and that a full picture of particle surface properties is possible via the combination of different, quantitative techniques

New possibilities of accurate particle characterisation by applying direct boundary models to analytical centrifugation

Analytical centrifugation (AC) is a powerful technique for the characterisation of nanoparticles in colloidal systems. As a direct and absolute technique it requires no calibration or measurements of standards. Moreover, it offers simple experimental design and handling, high sample throughput as well as moderate investment costs. However, the full potential of AC for nanoparticle size analysis requires the development of powerful data analysis techniques. In this study we show how the application of direct boundary models to AC data opens up new possibilities in particle characterisation. An accurate analysis method, successfully applied to sedimentation data obtained by analytical ultracentrifugation (AUC) in the past, was used for the first time in analysing AC data. Unlike traditional data evaluation routines for AC using a designated number of radial positions or scans, direct boundary models consider the complete sedimentation boundary, which results in significantly better statistics. We demonstrate that meniscus fitting, as well as the correction of radius and time invariant noise significantly improves the signal-to-noise ratio and prevents the occurrence of false positives due to optical artefacts. Moreover, hydrodynamic non-ideality can be assessed by the residuals obtained from the analysis. The sedimentation coefficient distributions obtained by AC are in excellent agreement with the results from AUC. Brownian dynamics simulations were used to generate numerical sedimentation data to study the influence of diffusion on the obtained distributions. Our approach is further validated using polystyrene and silica nanoparticles. In particular, we demonstrate the strength of AC for analysing multimodal distributions by means of gold nanoparticles

Wissen kommunizieren: Leitpunkte aus der Jungen Akademie: Ein Debattenbeitrag der Projektgruppe Wissen kommunizieren

Ob Klimawandel, technologische Innovationen, Pandemien oder soziale Ungleichheit – für eine gut informierte öffentliche Debatte ist Wissenschaftskommunikation essenziell. Aber auch die Vermittlung von Wissen, das für die Gesellschaft einfach spannend oder interessant ist, ist ein wichtiger Teil der Wissenschaftskommunikation. Wir als Wissenschaftler:innen sind allerdings in erster Linie auf Forschung spezialisiert und kommunizieren unsere Ergebnisse vorwiegend innerhalb der Fachcommunity. Um unser Wissen auch effektiv mit der Öffentlichkeit teilen zu können, müssen wir anders kommunizieren. Sei es beim Erstellen eigener Beiträge für klassische und neue Medien und Plattformen, in Interviews und Gesprächen mit Journalist:innen oder in der Politikberatung. Sofern Ihr nicht unter Zeitdruck steht, könnt Ihr durch Workshops zur Wissenschaftskommunikation und durch das Verfassen von kleineren Beiträgen schrittweise Erfahrungen sammeln. Manchmal allerdings, gerade in Krisenzeiten, wird die eigene Expertise sehr plötzlich und dringend angefragt, so dass kaum Zeit bleibt, sich in die Wissenschaftskommunikation einzuarbeiten. Ganz gleich, ob Ihr langsam einsteigen wollt oder plötzlich gebraucht werdet, ob Ihr die Debatte nur verfolgt oder aktiv mitgestalten wollt – mit diesem Leitfaden möchten wir Euch eine Orientierung bieten, damit Ihr die geschriebenen und ungeschriebenen Regeln der Wissenschaftskommunikation besser nutzen, verstehen und reflektieren könnt. Wir als Team der Jungen Akademie haben zahlreiche strukturierte Interviews mit Expert:innen aus Wissenschaft, Politik und Journalismus geführt, um Euch eine um fassende Orientierung und praxisnahe Tipps für eine erfolgreiche Wissenschaftskommunikation an die Hand zu geben. Darüber hinaus fußt dieser Leitfaden auch auf einer breit gefächerten Literaturgrundlage, die Ihr im Anhang findet. Insgesamt haben wir fünf Leitpunkte herausgearbeitet, die die Form und Grenzen der Kommunikation abstecken sollen. Ergänzend dazu haben wir konkrete Tipps und eine Checkliste zusammengestellt. Ihr findet zudem Hintergrundinformationen zu den Kommunikationskanälen, Regeln und Gepflogenheiten im Umgang mit Medienanfragen sowie Ansätze zum Umgang mit Fehlern, Angriffen oder Desinformation. Zum Abschluss präsentieren wir eine Vision der Wissenschaftskommunikation: Denn nur, wenn wir unsere Ziele formulieren, können wir sie auch erreichen. Einige Disclaimer vorab: Selbstverständlich können wir das Thema Wissenschaftskommunikation nicht in seiner gesamten Tiefe und Breite abdecken. Unser Leitfaden erhebt daher explizit nicht den Anspruch einer umfassenden wissenschaftlichen Analyse. Zudem konzentrieren wir uns auf die Interaktion mit klassischen Medien und professionellen Journalist:innen. Wir sind allerdings der Ansicht, dass für neue Plattformen, die noch vielfältigere Möglichkeiten für Kommunikation und Diskurs bieten, dieselben Grundsätze gelten. Weiterhin konzentrieren sich viele unserer Beispiele auf die empirischen Wissenschaften, zum Beispiel bei der Einordnung von Datenerhebungen oder der Erfassung von statistischer Unsicherheit. Auch hier gilt, dass die Grundprinzipien für viele andere Fachrichtungen ebenso anwendbar sind. Wählt also aus dem breiten Themenspektrum für Euch das Passende aus; sei es zur ersten Orientierung oder zum Reflektieren über die öffentliche Debatte. Trotz – oder gerade wegen – der zahlreichen Herausforderungen in der Wissenschaftskommunikation wünschen wir Euch viel Freude und Inspiration beim Lesen des Leitfadens und viel Erfolg bei Eurer Wissenschaftskommunikation! Euer Team „Wissenschaftskommunikation“ der Jungen Akademi

Investigation of the size–property relationship in CuInS2 quantum dots

In this work we investigated fundamental properties of CuInS2 quantum dots in dependence of the particle size distribution (PSD). Size-selective precipitation (SSP) with acetone as poor solvent was performed as an adequate post-processing step. Our results provide deep insight into the correlation between particle size and various optical characteristics as bandgap energy, absorption and emission features and the broadness of the emission signal. These structure–property relationships are only achieved due to the unique combination of different analytical techniques. Our study reveals that the removal of 10 wt% of smallest particles from the feed results in an enhancement of the emission signal. This improvement is ascribed to a decreased quenching of the emission in larger particles. Our results reveal the impact of PSDs on the properties and the performance of an ensemble of multicomponent QDs and anticipate the high potential of controlling PSDs by well-developed post-processing

Ni-Co-O anodes for the alkaline oxygen evolution reaction: Multistage electrode optimization and plasma-assisted activity enhancement enabled by a coherent workflow

Improving the performance of oxygen evolution reaction (OER) catalysts through proper catalyst design and processing represents a critical step toward enhancing the efficiency of water electrolysis. While many studies focus on structure-activity relationships and mechanistic insights confined to a particular stage during the anode fabrication, an integrated approach covering all process steps is crucial to optimize performance-relevant properties such as composition, morphology, and electrode architecture. In this study, we demonstrate a comprehensive approach for developing Ni-Co-O anodes as a model system through the entire process chain. Starting from the initial powder characterization through operando to post-catalysis analyses, we first underpin the critical impact of catalyst ink optimization through solvent matrix screening, enabling high-quality electrode layers via ultrasonic spray coating on Ni plates. This enables us to uncover the effects of post nitrogen plasma treatment integrated into our coherent workflow yielding binder-free Ni-Co-O anode surfaces with enhanced redox reversibility, Fe uptake, porosity, and wettability. These improvements reduce the OER overpotential by ~43 mV at 100 mA/cm2 compared to untreated counterparts. The durable performance of these electrodes is further demonstrated in a single cell configuration. Our holistic approach from catalyst powder to post-mortem analysis highlights the benefits of a coherent anode development strategy employing plasma post-processing which is broadly applicable and easily transferable to other benchmark electrocatalysts

Unraveling Complexity: A Strategy for the Characterization of Anisotropic Core Multishell Nanoparticles

Abstract In this work, a widely applicable routine to characterize the core, surface, stability, and optical properties of CdSe/CdS/ZnS core–shell–shell nanorods after multiple growth steps is established. First, size, shape, and shell thickness of the nanorods are characterized by transmission electron microscopy (TEM), analytical ultracentrifugation (AUC), and small angle X‐ray/neutron scattering (SAXS/SANS). In the next step, Fourier‐transform infrared (FT‐IR) spectroscopy, thermogravimetric analysis (TGA), and SANS measurements are applied to determine the surface species of nanorods. Then, the colloidal stability of the nanorods is investigated by UV–vis spectroscopy and dynamic light scattering (DLS) after different washing cycles. Finally, photoluminescence quantum yield (PLQY) of the nanorods during washing and sample storage is determined. With this highly complementary routine for particle characterization, the core, surface, stability, and optical properties of nanorods after multiple growth steps are resolved. The results demonstrate the importance of the developed toolbox to characterize such highly complex, anisotropic nanorods for a technical environment. This is of major importance for the handling of colloidal quantum materials and their quality control in industrial applications

Electrically Addressable Hybrid Architectures of Zinc Oxide Nanowires Grown on Aligned Carbon Nanotubes

The fabrication and characterization of hybrid architectures of ZnO nanowires (ZNWs) grown on organized carbon nanotubes (CNTs), by a two-step chemical vapor deposition (CVD) process involving CNT growth from a hydrocarbon source followed by ZNW growth using a Zn metal source, is reported. The ZNWs grow uniformly and radially from individual CNTs and CNT bundles, and the aligned morphology of the CNTs is not disturbed by the ZNW growth process. The nucleation and growth of ZnO crystals on CNTs are analyzed in relation to the classical vapor–solid mechanism. Importantly, the CNTs make uniform and distributed electrical contact to the ZNWs, with up to a 1000-fold yield advantage over conventional ZNW growth on a flat substrate. Hybrid ZNW/CNT sheets are fabricated by scalable CVD, rolling, and printing methods; and their electrical properties, which are governed by transport through the anisotropic CNT network, are characterized. Functional interaction between the ZNWs and CNTs is demonstrated by photoconductive behavior and photocurrent generation of the hybrid material under UV illumination. There is significant future opportunity to extend these processing methods to fabricate other functional oxides on CNTs, and to build devices that harness the attractive properties of ZNWs and CNTs with high volumetric efficiency over large areas.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77980/1/2470_ftp.pd