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Zweiphotonen-Photoemission topologischer Isolatoren (2021)
Sebastian, Otto
In dieser Arbeit werden die intrinsisch p-dotierten topologischen Isolatoren SnSb(2)Te(4), SnBi(0,1)Sb(1,9)Te(4), SnBi(0,2)Sb(1,8)Te(4) und GeSb(2)Te(4) untersucht, deren topologische Oberflächenzustände innerhalb der Bandlücke bestimmt, und mit Zirkulardichroismus-Messungen auf ihre Spinpolarisation getestet. Der Machbarkeit einer selektiven Anregung spinpolarisierter Zustände, und damit der Erzeugung eines Spinstromes, wird mit zirkular polarisierten Anregungspulsen nachgegangen und im Kontext der ultraschnellen Dynamik der Systeme, sowie aktuellen Entwicklungen in der Literatur diskutiert.
Cathepsin D Variants Associated With Neurodegenerative Diseases Show Dysregulated Functionality and Modified α-Synuclein Degradation Properties (2021)
Bunk, Josina ; Prieto Huarcaya, Susy ; Drobny, Alice ; Dobert, Jan Philipp ; Walther, Lina ; Rose-John, Stefan ; Arnold, Philipp ; Zunke, Friederike
Cathepsin D (CTSD) is a lysosomal protease important for the degradation of various substrates, including disease-associated proteins like α-synuclein (a-syn), amyloid precursor protein (APP) and tau, all of which tend to aggregate if not efficiently degraded. Hence, it is not surprising that genetic variants within the CTSD gene have been linked to neurodegenerative diseases, like Parkinson’s and Alzheimer’s disease (PD, AD), as well as the lysosomal storage disorder neuronal ceroid lipofuscinosis type-10 (NCL10). Although recent studies have shown the molecular dependence of substrate degradation via CTSD within autophagic pathways, only little is known about the precise role of lysosomal CTSD function in disease development. We here performed biochemical, cellular and structural analyses of eleven disease-causing CTSD point mutations found in genomic sequencing data of patients to understand their role in neurodegeneration. These CTSD variants were analyzed for cellular localization, maturation and enzymatic activity in overexpression analyses. Moreover, for PD-associated mutants, intracellular degradation of a-syn was monitored. In summary, our results suggest that NCL10-associated CTSD variants are significantly impaired in lysosomal maturation and enzymatic activity, whereas the AD- and PD-associated variants seemed rather unaffected, indicating normal maturation, and lysosomal presence. Interestingly, a PD-associated CTSD variant (A239V) exhibited increased enzymatic activity accompanied by enhanced a-syn degradation. By structural analyses of this mutant utilizing molecular dynamics simulation (MDS), we identified a structural change within a loop adjacent to the catalytic center leading to a higher flexibility and potentially accelerated substrate exchange rates. Our data sheds light onto the role of CTSD in disease development and helps to understand the structural regulation of enzymatic function, which could be utilized for targeted CTSD activation. Because of the degradative function of CTSD, this enzyme is especially interesting for therapeutic strategies tackling protein aggregates in neurodegenerative disorders.
Cinematic Rendering in Mixed-Reality Holograms: A New 3D Preoperative Planning Tool in Pediatric Heart Surgery (2021)
Gehrsitz, Pia ; Rompel, Oliver ; Schöber, Martin ; Cesnjevar, Robert ; Purbojo, Ariawan ; Uder, Michael ; Dittrich, Sven ; Alkassar, Muhannad
Cinematic rendering (CR) is based on a new algorithm that creates a photo-realistic three-dimensional (3D) picture from cross-sectional images. Previous studies have shown its positive impact on preoperative planning. To date, CR presentation has only been possible on 2D screens which limited natural 3D perception. To depict CR-hearts spatially, we used mixed-reality technology and mapped corresponding hearts as holograms in 3D space. Our aim was to assess the benefits of CR-holograms in the preoperative planning of cardiac surgery. Including 3D prints allowed a direct comparison of two spatially resolved display methods. Twenty-six patients were recruited between February and September 2019. CT or MRI was used to visualize the patient's heart preoperatively. The surgeon was shown the anatomy in cross-sections on a 2D screen, followed by spatial representations as a 3D print and as a high-resolution hologram. The holographic representation was carried out using mixed-reality glasses (HoloLens®). To create the 3D prints, corresponding structures were segmented to create STL files which were printed out of resin. In 22 questions, divided in 5 categories (3D-imaging effect, representation of pathology, structure resolution, cost/benefit ratio, influence on surgery), the surgeons compared each spatial representation with the 2D method, using a five-level Likert scale. The surgical preparation time was assessed by comparing retrospectively matched patient pairs, using a paired t-test. CR-holograms surpassed 2D-monitor imaging in all categories. CR-holograms were superior to 3D prints in all categories (mean Likert scale 4.4 ± 1.0 vs. 3.7 ± 1.3, P < 0.05). Compared to 3D prints it especially improved the depth perception (4.7 ± 0.7 vs. 3.7 ± 1.2) and the representation of the pathology (4.4 ± 0.9 vs. 3.6 ± 1.2). 3D imaging reduced the intraoperative preparation time (n = 24, 59 ± 23 min vs. 73 ± 43 min, P < 0.05). In conclusion, the combination of an extremely photo-realistic presentation via cinematic rendering and the spatial presentation in 3D space via mixed-reality technology allows a previously unattained level of comprehension of anatomy and pathology in preoperative planning.
Reduction of π‐Expanded Cyclooctatetraene with Lithium: Stabilization of the Tetra‐Anion through Internal Li+ Coordination (2021)
Zhou, Zheng ; Zhu, Yikun ; Wei, Zheng ; Bergner, John ; Neiß, Christian ; Doloczki, Susanne ; Görling, Andreas ; Kivala, Milan ; Petrukhina, Marina A.
Abstract The chemical reduction of a π‐expanded polycyclic framework comprising a cyclooctatetraene moiety, octaphenyltetrabenzocyclooctatetraene, with lithium metal readily affords the corresponding tetra‐anion instead of the expected aromatic dianion. As revealed by X‐ray crystallography, the highly contorted tetra‐anion is stabilized by coordination of two internally bound Li+, while two external cations remain solvent separated. The variable‐temperature 7Li NMR spectra in THF confirm the presence of three types of Li+ ions and clearly differentiate internal binding, consistent with the crystal structure. Density‐functional theory calculations suggest that the formation of the highly charged tetra‐reduced carbanion is stabilized through Li+ coordination under the applied experimental conditions.
Metallic Barium: A Versatile and Efficient Hydrogenation Catalyst (2021)
Stegner, Philipp ; Färber, Christian ; Zenneck, Ulrich ; Knüpfer, Christian ; Eyselein, Jonathan ; Wiesinger, Michael ; Harder, Sjoerd
Abstract Ba metal was activated by evaporation and cocondensation with heptane. This black powder is a highly active hydrogenation catalyst for the reduction of a variety of unactivated (non‐conjugated) mono‐, di‐ and tri‐substituted alkenes, tetraphenylethylene, benzene, a number of polycyclic aromatic hydrocarbons, aldimines, ketimines and various pyridines. The performance of metallic Ba in hydrogenation catalysis tops that of the hitherto most active molecular group 2 metal catalysts. Depending on the substrate, two different catalytic cycles are proposed. A: a classical metal hydride cycle and B: the Ba metal cycle. The latter is proposed for substrates that are easily reduced by Ba0, that is, conjugated alkenes, alkynes, annulated rings, imines and pyridines. In addition, a mechanism in which Ba0 and BaH2 are both essential is discussed. DFT calculations on benzene hydrogenation with a simple model system (Ba/BaH2) confirm that the presence of metallic Ba has an accelerating effect.
Quartzite procurement in conglomerates and deposits: Geoarchaeological characterization of potential catchment areas in the central part of the Cantabrian Region, Spain (2021)
Prieto, Alejandro ; Yusta, Iñaki ; García‐Rojas, Maite ; Arrizabalaga, Alvaro ; Baena Preysler, Javier
Abstract Raw material characterization in Paleolithic archaeology has widened our knowledge of Middle Paleolithic societies. Procurement of raw material, specifically flint, has allowed the tracing of the mobility of both stones and people, as well as selective processes to obtain specific types or even extraction activities. The analysis of quartzite has also developed in recent years, providing an opportunity to better understand prehistoric societies. This study characterizes the procurement strategies implemented by Middle Paleolithic people in the mountainous region of the Picos de Europa. To this end, we present a comprehensive characterization of potential catchment areas: massive outcrops, conglomerates, and river deposits. The exploitation of quartzite at the sites of El Habario and El Arteu allows us to understand the territorial management of this mountainous area through the combination of selective processes and mobility mechanisms in lower and middle altitudes. These perspectives enable us to view the mountainous region not as a barrier but as an environmental mosaic managed by Middle Paleolithic groups. This study shows strategies that bring together direct and embedded procurement based on both intensive and extensive searches. These discourses are more closely related to the daily life of people than those only considering the mobility of people and objects.
Additive value of transarterial embolization to systemic sirolimus treatment in kaposiform hemangioendothelioma (2020)
Brill, Richard ; Uller, Wibke ; Huf, Veronika ; Müller‐Wille, René ; Schmid, Irene ; Pohl, Alexandra ; Häberle, Beate ; Perkowski, Sybille ; Funke, Katrin ; Till, Anne‐Marie ; Lauten, Melchior ; Neumann, Jacob ; Güttel, Christian ; Heid, Esther ; Ziermann, Franziska ; Schmid, Axel ; Hüsemann, Dieter ; Meyer, Lutz ; Sporns, Peter B. ; Schinner, Regina ; Schmidt, Vanessa F. ; Ricke, Jens ; Rössler, Jochen ; Kapp, Friedrich G. ; Wohlgemuth, Walter A. ; Wildgruber, Moritz
Abstract Kaposiform hemangioendothelioma (KHE) is a rare vascular tumor in children, which can be accompanied by life‐threatening thrombocytopenia, referred to as Kasabach‐Merritt phenomenon (KMP). The mTOR inhibitor sirolimus is emerging as targeted therapy in KHE. As the sirolimus effect on KHE occurs only after several weeks, we aimed to evaluate whether additional transarterial embolization is of benefit for children with KHE and KMP. Seventeen patients with KHE and KMP acquired from 11 hospitals in Germany were retrospectively divided into two cohorts. Children being treated with adjunct transarterial embolization and systemic sirolimus, and those being treated with sirolimus without additional embolization. Bleeding grade as defined by WHO was determined for all patients. Response of the primary tumor at 6 and 12 months assessed by magnetic resonance imaging (MRI), time to response of KMP defined as thrombocyte increase >150 × 103/μL, as well as rebound rates of both after cessation of sirolimus were compared. N = 8 patients had undergone additive embolization to systemic sirolimus therapy, sirolimus in this group was started after a mean of 6.5 ± 3 days following embolization. N = 9 patients were identified who had received sirolimus without additional embolization. Adjunct embolization induced a more rapid resolution of KMP within a median of 7 days vs 3 months; however, tumor response as well as rebound rates were similar between both groups. Additive embolization may be of value for a more rapid rescue of consumptive coagulopathy in children with KHE and KMP compared to systemic sirolimus only.
Fabrication and characterization of Ag‐ and Ga‐doped mesoporous glass‐coated scaffolds based on natural marine sponges with improved mechanical properties (2020)
Ciraldo, Francesca E. ; Arango‐Ospina, Marcela ; Goldmann, Wolfgang H. ; Beltrán, Ana M. ; Detsch, Rainer ; Gruenewald, Alina ; Roether, J. A. ; Boccaccini, Aldo R.
Abstract Natural marine sponges were used as sacrificial template for the fabrication of bioactive glass‐based scaffolds. After sintering at 1050°C, the resulting samples were additionally coated with a silicate solution containing biologically active ions (Ag and Ga), well‐known for their antibacterial properties. The produced scaffolds were characterized by superior mechanical properties (maximum compressive strength of 4 MPa) and total porosity of ~80% in comparison to standard scaffolds made by using PU foam templates. Direct cell culture tests performed on the uncoated and coated samples showed positive results in terms of adhesion, proliferation, and differentiation of MC3T3‐E1 cells. Moreover, vascular endothelial growth factor (VEGF) secretion from cells in contact with scaffold dissolution products was measured after 7 and 10 days of incubation, showing promising angiogenic results for bone tissue engineering applications. The antibacterial potential of the produced samples was assessed by performing agar diffusion tests against both Gram‐positive and Gram‐negative bacteria.
A new approach to classification of 40 years of Antarctic sea ice concentration data (2021)
Wachter, Paul ; Reiser, Fabian ; Friedl, Peter ; Jacobeit, Jucundus
Abstract In this paper, we present a characterization of Antarctic sea ice based on the classification of annual sea ice concentration (SIC) data from 1979 to 2018. A clustering algorithm was applied to provide a climatological description of significant annual cycles of SIC and their spatial distribution around the Southern Ocean. Based on these classification results, we investigate the variability of SIC cycles on decadal and inter‐annual time scales. First, we discuss significant spatial shifts of SIC cycles during 1979–1998 and 1999–2018. In the Weddell Sea and in large parts of the Ross Sea, we observed higher SIC during the summer season, and an extension of sea ice cover in winter compared to the long‐term average. Second, we introduce the Climatological Sea Ice Anomaly Index (CSIAI), which is an annual measure for year‐round sea ice anomalies of the Southern Ocean and its regional sub‐sectors. By relating selected years of significant sea ice conditions (1981, 2007 and 2014) with atmospheric influences, we demonstrate that the CSIAI is very useful for assessing inter‐annular Antarctic SIC variability. Positive and negative sea ice anomalies can be qualitatively explained by atmospheric circulation anomalies in the years 1981 and 2007. However, in 2014, the year with the largest observed sea ice extent in our time series, we found that this positive sea ice anomaly was surprisingly not associated with a stationary and inter‐seasonally persistent pattern of circulation anomaly. This suggests that sub‐seasonal to seasonal circulation anomalies and ocean‐related processes favoured the formation of the sea ice maximum in 2014. With this study we provide additional information on the long‐term annual SIC variability around Antarctica. Furthermore, our classification approach and its results have potential for application in the evaluation of sea ice model results.
How To Make Nitroaromatic Compounds Glow: Next‐Generation Large X‐Shaped, Centrosymmetric Diketopyrrolopyrroles (2020)
Skonieczny, Kamil ; Papadopoulos, Ilias ; Thiel, Dominik ; Gutkowski, Krzysztof ; Haines, Philipp ; McCosker, Patrick M. ; Laurent, Adèle D. ; Keller, Paul A. ; Clark, Timothy ; Jacquemin, Denis ; Guldi, Dirk M. ; Gryko, Daniel T.
Abstract Red‐emissive π‐expanded diketopyrrolopyrroles (DPPs) with fluorescence reaching λ=750 nm can be easily synthesized by a three‐step strategy involving the preparation of diketopyrrolopyrrole followed by N‐arylation and subsequent intramolecular palladium‐catalyzed direct arylation. Comprehensive spectroscopic assays combined with first‐principles calculations corroborated that both N‐arylated and fused DPPs reach a locally excited (S1) state after excitation, followed by internal conversion to states with solvent and structural relaxation, before eventually undergoing intersystem crossing. Only the structurally relaxed state is fluorescent, with lifetimes in the range of several nanoseconds and tens of picoseconds in nonpolar and polar solvents, respectively. The lifetimes correlate with the fluorescence quantum yields, which range from 6 % to 88 % in nonpolar solvents and from 0.4 % and 3.2 % in polar solvents. A very inefficient (T1) population is responsible for fluorescence quantum yields as high as 88 % for the fully fused DPP in polar solvents.
Whole brain snapshot CEST at 3T using 3D‐EPI: Aiming for speed, volume, and homogeneity (2020)
Mueller, Sebastian ; Stirnberg, Rüdiger ; Akbey, Suzan ; Ehses, Philipp ; Scheffler, Klaus ; Stöcker, Tony ; Zaiss, Moritz
Purpose CEST MRI enables imaging of distributions of low‐concentrated metabolites as well as proteins and peptides and their alterations in diseases. CEST examinations often suffer from low spatial resolution, long acquisition times, and concomitant motion artifacts. This work aims to maximize both resolution and volume coverage with a 3D‐EPI snapshot CEST approach at 3T, allowing for fast and robust whole‐brain CEST MRI. Methods Resolution and temporal SNR of 3D‐EPI examinations with nonselective excitation were optimized at a clinical 3T MR scanner in five healthy subjects using a clinical head/neck coil. A CEST presaturation module for low power relayed nuclear Overhauser enhancement and amide proton transfer contrast was applied as an example. The suggested postprocessing included motion correction, dynamic B0 correction, denoising, and B1 correction and was compared to an established 3D‐gradient echo‐based sequence. Results CEST examinations were performed at 1.8 mm nominal isotropic resolution in 4.3 s per presaturation offset. In contrast to slab‐selective 3D or multislice approaches, the whole brain was covered. Repeated examinations at three different B1 values took 13 minutes for 58 presaturation offsets with temporal SNR around 75. The resulting CEST effects revealed significant gray and white matter contrast and were of similar quality across the whole brain. Coefficient of variation across three healthy subjects was below 9%. Conclusion The suggested protocol enables whole brain coverage at 1.8 mm isotropic resolution and fast acquisition of 4.3 s per presaturation offset. For the fitted CEST amplitudes, high reproducibility was proven, increasing the opportunities of quantitative CEST investigations at 3T significantly.
Brackish water algal reefs – facies analysis as a tool to identify palaeoenvironmental variations in Miocene deposits (Mainz‐Weisenau, Germany) (2021)
Nohl, Theresa ; Knoblach, Julia ; Teichert, Sebastian
Brackish‐water carbonates are far less studied than their marine or limnic counterparts. However, their association with few, specialized species enables the documentation of fine‐scale changes in the depositional environment. The Cenozoic Mainz Basin (Germany) was only sporadically connected to the North Sea and the Paratethys, exposing several transitions from marine to fresh water influence. Focusing on one outcrop of the Rüssingen Formation of Mainz‐Weisenau (Aquitanian, Miocene), we present a detailed analysis of the faunal and sedimentological responses to changing salinities and water depth, including algal reef growth and facies development. The deposits include allochthonous limestones surrounding an autochthonous reef complex and several smaller reef patches. The allochthonous facies is dominated by the gastropod Hydrobia inflata, and the reef facies is mainly made up by the green alga Cladophorites sp. The algal thalli are overgrown by cryptocrystalline, organic precipitations, and laminated, chemical precipitations. Locally, quiver‐shaped structures of Trichoptera sp. protective cases occur. The depositional setting was a shallow, low energy, and brackish environment supersaturated by carbonate. We could not confirm a general trend of reducing salinities as reported for the Rüssingen Formation. Our results question previously reported episodic desiccation events, because apparent caliche horizons actually represent thin beds of increased Cladophorites growth. Set‐up, distribution of the reef facies, and reef debris indicate short‐time variations of temperature, salinity and water depth. We conclude that these variations are based on the geographic position at the edge of an algal reef barrier, separating the Mainz Basin from the Rhine Rift Valley.
Reversible Activation and Transfer of White Phosphorus by Silyl‐Stannylene (2021)
Sarkar, Debotra ; Weetman, Catherine ; Munz, Dominik ; Inoue, Shigeyoshi
Abstract Use of a silyl supported stannylene (MesTerSn(SitBu3) [MesTer=2,6‐(2,4,6‐Me3C6H2)2C6H3] enables activation of white phosphorus under mild conditions, which is reversible under UV light. The reaction of a silylene chloride with the activated P4 complex results in facile P‐atom transfer. The computational analysis rationalizes the electronic features and high reactivity of the heteroleptic silyl‐substituted stannylene in contrast to the previously reported bis(aryl)stannylene.
Potential of laponite incorporated oxidized alginate–gelatin (ADA‐GEL) composite hydrogels for extrusion‐based 3D printing (2020)
Cai, Fei‐Fan ; Heid, Susanne ; Boccaccini, Aldo R.
Abstract The concept of adding inorganic fillers into hydrogels to form hydrogel nanocomposites often provides advantageous properties which can be exploited for successful 3D biofabrication. In this study, a new composite hydrogel combining oxidized alginate–gelatin (ADA‐GEL) hydrogel and laponite nanoclay as inorganic nanofiller was successfully developed and characterized. The results showed that the addition of 0.5% (wt/vol) laponite nanoplatelets improved the printability of ADA‐GEL hydrogels enabling the fabrication of detailed structures since a low effect of material spreading and reduced tendency to pore closure appeared. Furthermore, a comparison of different needle types (cylindrical and conical; same inner diameter of 250 μm) in filament fusion test showed that the pattern dispensed by cylindrical tip has enhanced printing accuracy and pattern fidelity when compared with the pattern from conical tip. A glass flip test determined a processing window of 1–2 h after composite ink preparation. Overall, laponite/ADA‐GEL hydrogel composites are confirmed as promising inks for 3D bioprinting.
From Cyclopentasilane to Thin‐Film Transistors (2021)
Gerwig, Maik ; Ali, Abid Shaukat ; Neubert, David ; Polster, Sebastian ; Böhme, Uwe ; Franze, Georg ; Rosenkranz, Marco ; Popov, Alexey ; Ponomarev, Ilia ; Jank, Michael P. M. ; Viehweger, Christine ; Brendler, Erica ; Frey, Lothar ; Kroll, Peter ; Kroke, Edwin
Abstract Cyclopentasilane (CPS) has been studied as an liquid precursor for the deposition of thin silicon films for printed electronics and related applications. The processing involves a UV‐induced prepolymerization of CPS followed by liquid deposition and low‐temperature thermolysis. An insight into the oligomer and polymer formation including crosslinking in solution using 29Si NMR spectroscopy and electron spin resonance spectroscopy is reported. Formation of SiH (T‐units) and SiH3 (M‐units) is observed as well as short‐lived paramagnetic species. Additionally, the polymerization is followed by Raman spectroscopy. Reactive molecular dynamics simulations are applied to develop a theoretical model for the CPS‐ring‐opening and crosslinking steps. The experimental and computational data correspond well to each other and allow insight into the mechanism of polymer formation. The processing steps include spin‐coating, thermal drying, and conversion to amorphous silicon, H‐passivation, and fabrication of a CPS‐derived thin‐film transistor (TFT), without intermediate silicon crystallization. Further improvement is gained by using tetralene as a solvent, leading to a reduction of the time‐consuming polymerization step by one order of magnitude compared to cyclooctane. The overall quality and characteristics of the CPS‐derived spin‐coated silicon thin films correspond to standard plasma enhanced chemical vapor deposition‐derived devices with respect to performance levels.
Predeformed geometrically exact beam model for a dynamic‐response prosthesis (2021)
Scheiterer, Eduard S. ; Leyendecker, Sigrid
Abstract Clinical trials have shown that the storage and release of energy in prosthetic feet plays a major role in the resulting walking comfort for the patient. In comparison to rigid multi‐axis prosthetic feet, dynamic‐response prosthetic feet show good energy storage and release capabilities and thereby increase the walking comfort of the patient. To accurately simulate such a prosthesis in a gait cycle simulation, its model has to represent the deformation energy as accurately as possible. Based on the theory of predeformed geometrically exact beams [1], this work proposes a model for a carbon spring foot prosthesis, continuing the work from [3]. The model is based on the Össur Vari‐Flex®, which has been non destructively reverse engineered resulting in a CAD representation and various parameters. Additionally, the parameters for density and elasticity and shear modulus were refined with parameter optimisation [4]. The geometrically exact beam model of the prosthesis offers a good representation of the deformation energy for large deformations occurring during the gait cycle while reducing the computational cost. The model's implementation is validated numerically and a brief mesh study is performed. The next step is the consideration of epistemic uncertainty and to investigate its influence on the prediction of the energy storage and release capabilities of the prosthesis.
π‐Extended Diaza[7]helicenes by Hybridization of Naphthalene Diimides and Hexa‐peri‐hexabenzocoronenes (2021)
Dusold, Carolin ; Sharapa, Dmitry I. ; Hampel, Frank ; Hirsch, Andreas
Abstract The synthesis of an unprecedented, π‐extended hexabenzocorene (HBC)‐based diaza[7]helicene is presented. The target compound was synthesized by an ortho‐fusion of two naphthalene diimide (NDI) units to a HBC‐skeleton. A combination of Diels–Alder and Scholl‐type oxidation reactions involving a symmetric di‐NDI‐tolane precursor were crucial for the very selective formation of the helical superstructure via a hexaphenyl‐benzene (HPB) derivative. The formation of the diaza[7]helicene moiety in the final Scholl oxidation is favoured, affording the symmetric π‐extended helicene as the major product as a pair of enantiomers. The separation of the enantiomers was successfully accomplished by HPLC involving a chiral stationary phase. The absolute configuration of the enantiomers was assigned by comparison of circular dichroism spectra with quantum mechanical calculations.
A Small Dye Puzzle: π‐Conjugation of Perylenes with External Aromatic Compounds via Imidazo‐Quinoxaline Bridges (2021)
Dobeneck, Michaela ; Kaur, Ramandeep ; Platzer, Benedikt ; Guldi, Dirk M. ; Hirsch, Andreas
Abstract The synthesis and characterization of a library of unprecedented π‐extended perylenes is reported. For this purpose, a successful step‐by‐step connection of three puzzle pieces, namely a perylene, an imidazole‐quinoxaline bridge and an o‐quinone was developed. Our synthetic route allows for facile access to linearly π‐extended perylenes in a highly chemoselective manner. The absorption and fluorescence properties are solvent dependent and are bathochromically shifted relative to unbridged perylene references. Overall, the fluorescence quantum yields are high with values ranging from 46 % to 11 %. To complete the physico‐chemical characterization, differential pulse and cyclic voltammograms were recorded showing two reductions and two oxidations for each of the linearly π‐extended perylenes.
Device Performance of Emerging Photovoltaic Materials (Version 1) (2020)
Almora, Osbel ; Baran, Derya ; Bazan, Guillermo C. ; Berger, Christian ; Cabrera, Carlos I. ; Catchpole, Kylie R. ; Erten‐Ela, Sule ; Guo, Fei ; Hauch, Jens ; Ho‐Baillie, Anita W. Y. ; Jacobsson, T. Jesper ; Janssen, Rene A. J. ; Kirchartz, Thomas ; Kopidakis, Nikos ; Li, Yongfang ; Loi, Maria A. ; Lunt, Richard R. ; Mathew, Xavier ; McGehee, Michael D. ; Min, Jie ; Mitzi, David B. ; Nazeeruddin, Mohammad K. ; Nelson, Jenny ; Nogueira, Ana F. ; Paetzold, Ulrich W. ; Park, Nam‐Gyu ; Rand, Barry P. ; Rau, Uwe ; Snaith, Henry J. ; Unger, Eva ; Vaillant‐Roca, Lídice ; Yip, Hin‐Lap ; Brabec, Christoph J.
Abstract Emerging photovoltaics (PVs) focus on a variety of applications complementing large scale electricity generation. Organic, dye‐sensitized, and some perovskite solar cells are considered in building integration, greenhouses, wearable, and indoor applications, thereby motivating research on flexible, transparent, semitransparent, and multi‐junction PVs. Nevertheless, it can be very time consuming to find or develop an up‐to‐date overview of the state‐of‐the‐art performance for these systems and applications. Two important resources for recording research cells efficiencies are the National Renewable Energy Laboratory chart and the efficiency tables compiled biannually by Martin Green and colleagues. Both publications provide an effective coverage over the established technologies, bridging research and industry. An alternative approach is proposed here summarizing the best reports in the diverse research subjects for emerging PVs. Best performance parameters are provided as a function of the photovoltaic bandgap energy for each technology and application, and are put into perspective using, e.g., the Shockley–Queisser limit. In all cases, the reported data correspond to published and/or properly described certified results, with enough details provided for prospective data reproduction. Additionally, the stability test energy yield is included as an analysis parameter among state‐of‐the‐art emerging PVs.
A Functional Hexaphenylbenzene Library Comprising of One, Three, and Six Peripheral Rylene‐Diimide Substituents (2021)
Dusold, Carolin ; Platzer, Benedikt ; Haines, Philipp ; Reger, David ; Jux, Norbert ; Guldi, Dirk. M. ; Hirsch, Andreas
Abstract Synthesis and characterization of a series of rylene‐diimide substituted hexaphenylbenzenes (HPBs) is presented. The direct connection of the rylene‐diimide units to the HPBs via the imide‐N‐position without any linkers as well as the use of naphthalene‐diimides (NDIs) next to perylene‐diimides (PDIs) is unprecedented. While mono‐substituted products were obtained by imidization reactions with amino‐HPB and the respective rylene‐monoimides, key step for the formation of tri‐ and hexa‐substituted HPBs is the Co‐catalysed cyclotrimerization. Particular emphasis for physic‐chemical characterization was on to the number of NDIs/PDIs per HPB and the overall substitution patterns. Lastly, Scholl oxidation conditions were applied to all HPB systems to generate the corresponding hexa‐peri‐hexabenzocoronenes (HBCs). Importantly, the efficiency of the transformation strongly depends on the number of NDIs/PDIs. While three rylene‐diimide units already hinder the Scholl reaction, the successful synthesis of mono‐substituted HBCs is possible.

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