Electrospray ion beam deposition and mass spectrometry of nonvolatile molecules and nanomaterials

The vacuum deposition of complex functional molecules and nanoparticles by thermal sublimation is often hindered due to their extremely low vapor pressure. This especially impedes the application of ultrahigh vacuum (UHV) based analytical and surface modification techniques for the investigation of these extremely interesting systems. On the other hand, specimen prepared under ambient conditions or in solution are typically not sufficiently well-defined and clean to allow a thorough and precise characterization. In order to bridge this technological gap, a novel ion beam source for controlled soft landing deposition in ultrahigh vacuum is constructed. The ion beam of nonvolatile particles is created by electrospray ionization (ESI). The deposition apparatus consists of six differential pumping stages designed to overcome the pressure difference of 13 orders of magnitude between the ambient pressure side, where ionization occurs, and the high or ultrahigh vacuum, where the deposition takes place. A variety of ion optical devices is employed to form, mass select and guide the ion beam through the pumping stages onto the deposition target. The ion beam is sampled from a supersonic expansion by a skimmer, collimated in a high pressure quadrupole ion guide, mass selected in a low pressure quadrupole ion guide and focused by electrostatic lenses. In order to have full control over all relevant parameters, the ion beam is characterized before the deposition by a linear time-of-flight mass spectrometer and a retarding grid energy detector. The flux, the composition and the kinetic energy of the ion beam can thus be measured and adjusted. The concept of ion beam deposition in high and ultrahigh vacuum is demonstrated by extensive mass spectrometric and deposition experiments. Many different types of ion beams, for instance composed of organic molecules, organic and inorganic ionically bound clusters, polymers and proteins, are created by ESI. Their properties are analyzed by mass spectrometry, with special focus on their behavior upon energetic collisions with a neutral gas, since these processes bear many similarities to collisions with a solid surface. Some of the ion beams are used for deposition. Ion beams of the protein BSA , of the dye molecule Rhodamine 6G (Rho6G), of organic ionic surfactant clusters composed of sodium-dodecyl sulfate (SDS) and of inorganic nanoparticles (gold colloids, carbon nanotubes, CdS nanorods and V2O5 nanowires), are deposited onto graphite and silicon oxide (SiOx) surfaces in high vacuum. The fluorescence of Rho6G is detected after its deposition, which is a proof for the destruction-free ion beam deposition, i.e. of a successful soft landing. For the other classes of deposited particles, diffusion on the surface and sometimes formation of nanostructures is observed. BSA forms fractal agglomerations on graphite, while it does not show any diffusion on SiOx surfaces. SDS forms flat, two dimensional islands on graphite and silicon. Finally it is demonstrated that large, inorganic nanoparticles (up to 106 µ) can be ionized and soft landed by the developed apparatus. Having proven the principle of low energy ion beam deposition for a wide variety of nonvolatile particles, the technique is now ready for being integrated with in-situ characterization techniques such as scanning tunneling and atomic force microscopy (STM, AFM). For this purpose, the ion beam deposition setup has been expanded by two vacuum chambers for sample preparation and analysis. Future experiments aim at the deposition and analysis of complex organic molecules in UHV, and at gaining a more detailed understanding of the soft landing process

The Perfect Data-Marriage: Transitional Justice Research and Oral History Life Stories

There is a growing recognition in transitional justice research of the crucial significance of context-appropriate measures of justice practices and needs, which account for the diversity, locality, and complexity of individuals’ experiences of the past. In this perspective, this paper highlights the significance of oral history collections for exploring pluralistic understandings of the personal past and their relation to symbolic justice practices and needs. We argue that their audio-visual dimension and multi-layered nature makes them a unique qualitative data source that can contribute to a more realistic assessment of justice concerns in transitional settings. As tools of social dialogue and inclusive justice, they are also valuable means to promote the mutual acceptance and recognition of suffering and responsibility. We demonstrate how findings based on the analysis of survey data collected in Bosnia-Herzegovina (BiH) can be enriched by the exploration of oral history narratives from a dataset collected in BiH

Exploring the Molecular Conformation Space by Soft Molecule–Surface Collision

Biomolecules function by adopting multiple conformations. Such dynamics are governed by the conformation landscape whose study requires characterization of the ground and excited conformation states. Here, the conformational landscape of a molecule is sampled by exciting an initial gas-phase molecular conformer into diverse conformation states, using soft molecule-surface collision (0.5-5.0 eV). The resulting ground and excited molecular conformations, adsorbed on the surface, are imaged at the single-molecule level. This technique permits the exploration of oligosaccharide conformations, until now, limited by the high flexibility of oligosaccharides and ensemble-averaged analytical methods. As a model for cellulose, cellohexaose chains are observed in two conformational extremes, the typical "extended" chain and the atypical "coiled" chain-the latter identified as the gas-phase conformer preserved on the surface. Observing conformations between these two extremes reveals the physical properties of cellohexaose, behaving as a rigid ribbon that becomes flexible when twisted. The conformation space of any molecule that can be electrosprayed can now be explored

Choosing the right model for unified flexibility modeling

Using aggregated flexibility from distributed small-scale power devices is an extensively discussed approach to meet the challenges in modern and increasingly stochastic energy systems. It is crucial to be able to model and map the flexibility of the respective power devices in a unified form to increase the value of the cumulative flexibility from different small-scale power devices by aggregation. In order to identify the most suitable approach for unified flexibility modeling we present a framework to evaluate and compare the advantages and disadvantages of already existing modeling approaches in different levels of detail. As an introduction to flexibility modeling and as a basis for the evaluation process we initially provide a comprehensive overview of the broad range of flexibility models described in scientific literature. Subsequently, five selected modeling approaches allowing the generation of a unified flexibility representation for different power devices are presented in detail. By using an evaluation metric we assess the suitability of the selected approaches for unified flexibility modeling and their applicability. To allow a more detailed performance analysis, the best evaluated models are implemented and simulations with different small-scale devices are performed. The results shown in this paper highlight the heterogeneity of modeling concepts deriving from the various interpretations of flexibility in scientific literature. Due to the varying complexity of the modeling approaches, different flexibility potentials are identified, necessitating a combination of approaches to capture the entire spectrum of the flexibility of different small-scale power devices. Furthermore, it is demonstrated that a complex model does not necessarily lead to the discovery of higher flexibility potentials, and recommendations are given on how to choose an appropriate model. © 2022, The Author(s)

Soft-landing electrospray ion beam deposition of sensitive oligoynes on surfaces in vacuum

AbstractAdvances in synthetic chemistry permit the synthesis of large, highly functional, organic molecules. Characterizing the complex structure of such molecules with highly resolving, vacuum-based methods like scanning probe microscopy requires their transfer into the gas phase and further onto an atomically clean surface in ultrahigh vacuum without causing additional contamination. Conventionally this is done via sublimation in vacuum. However, similar to biological molecules, large synthetic compounds can be non-volatile and decompose upon heating. Soft-landing ion beam deposition using soft ionization methods represents an alternative approach to vacuum deposition. Using different oligoyne derivatives of the form of R1(CC)nR2, here we demonstrate that even sensitive molecules can be handled by soft-landing electrospray ion beam deposition. We generate intact molecular ions as well as fragment ions with intact hexayne parts and deposit them on clean metal surfaces. Scanning tunneling microscopy shows that the reactive hexayne segments of the molecules of six conjugated triple bonds are intact. The molecules agglomerate into ribbon-like islands, whose internal structure can be steered by the choice of the substituents. Our results suggest the use of ion beam deposition to arrange reactive precursors for subsequent polymerization reactions

A preparative mass spectrometer to deposit intact large native protein complexes

Electrospray ion-beam deposition (ES-IBD) is a versatile tool to study the structure and reactivity of molecules from small metal clusters to large protein assemblies. It brings molecules gently into the gas phase, where they can be accurately manipulated and purified, followed by controlled deposition onto various substrates. In combination with imaging techniques, direct structural information on well-defined molecules can be obtained, which is essential to test and interpret results from indirect mass spectrometry techniques. To date, ion-beam deposition experiments are limited to a small number of custom instruments worldwide, and there are no commercial alternatives. Here we present a module that adds ion-beam deposition capabilities to a popular commercial MS platform (Thermo Scientific Q Exactive UHMR mass spectrometer). This combination significantly reduces the overhead associated with custom instruments, while benefiting from established high performance and reliability. We present current performance characteristics including beam intensity, landing-energy control, and deposition spot size for a broad range of molecules. In combination with atomic force microscopy (AFM) and transmission electron microscopy (TEM), we distinguish near-native from unfolded proteins and show retention of the native shape of protein assemblies after dehydration and deposition. Further, we use an enzymatic assay to quantify the activity of a noncovalent protein complex after deposition on a dry surface. Together, these results not only indicate a great potential of ES-IBD for applications in structural biology, but also outline the challenges that need to be solved for it to reach its full potential

The Perfect Data-Marriage

There is a growing recognition in transitional justice research of the crucial significance of context-appropriate measures of justice practices and needs, which account for the diversity, locality, and complexity of individuals’ experiences of the past. In this perspective, this paper highlights the significance of oral history collections for exploring pluralistic understandings of the personal past and their relation to symbolic justice practices and needs. We argue that their audio-visual dimension and multi-layered nature makes them a unique qualitative data source that can contribute to a more realistic assessment of justice concerns in transitional settings. As tools of social dialogue and inclusive justice, they are also valuable means to promote the mutual acceptance and recognition of suffering and responsibility. We demonstrate how findings based on the analysis of survey data collected in Bosnia-Herzegovina (BiH) can be enriched by the exploration of oral history narratives from a dataset collected in BiH

Visualizing Chiral Interactions in Carbohydrates Adsorbed on Au(111) by High‐Resolution STM Imaging

Carbohydrates are the most abundant organic material on Earth and the structural “material of choice” in many living systems. Nevertheless, design and engineering of synthetic carbohydrate materials presently lag behind that for protein and nucleic acids. Bottom-up engineering of carbohydrate materials demands an atomic-level understanding of their molecular structures and interactions in condensed phases. Here, high-resolution scanning tunneling microscopy (STM) is used to visualize at submolecular resolution the three-dimensional structure of cellulose oligomers assembled on Au(1111) and the interactions that drive their assembly. The STM imaging, supported by ab initio calculations, reveals the orientation of all glycosidic bonds and pyranose rings in the oligomers, as well as details of intermolecular interactions between the oligomers. By comparing the assembly of D- and L-oligomers, these interactions are shown to be enantioselective, capable of driving spontaneous enantioseparation of cellulose chains from its unnatural enantiomer and promoting the formation of engineered carbohydrate assemblies in the condensed phases

Fast Molecular Compression by a Hyperthermal Collision Gives Bond-Selective Mechanochemistry

Using electrospray ion beam deposition, we collide the complex molecule Reichardt’s Dye (C41H30NO+) at low, hyperthermal translational energy (2 - 50 eV) with a Cu(100) surface and image the outcome at single-molecule level by scanning tunneling microscopy. We observe bond-selective reaction induced by the translational kinetic energy. The collision impulse compresses the molecule and bends specific bonds, prompting them to react selectively. This dynamics drives the system to seek thermally inaccessible reactive pathways, since the compression timescale (sub-ps) is much shorter than the thermalization timescale (ns), thereby yielding reaction products that are unobtainable thermally

Having a creative day:understanding entrepreneurs’ daily idea generation through a recovery lens

Prior research has shown that trait creativity is important for becoming an entrepreneur and successful in business. We explore a new perspective by investigating how recovery from work stress influences entrepreneurs’ daily idea generation, a key aspect of creativity. Physio-logical and mental recovery enables the cognitive processes of creative problem-solving. Moreover, differences in mental recovery processes help to explain age-related changes in en-trepreneurs’ creativity. Multilevel analyses based on 415 daily data from 62 entrepreneurs support our predictions. Our study introduces a new “state” perspective to understanding en-trepreneurs’ creativity, and highlights the critical role of recovery processes for idea genera-tion