Entanglement and Sources of Magnetic Anisotropy in Radical Pair-Based Avian Magnetoreceptors

One of the principal models of magnetic sensing in migratory birds rests on the quantum spin-dynamics of transient radical pairs created photochemically in ocular cryptochrome proteins. We consider here the role of electron spin entanglement and coherence in determining the sensitivity of a radical pair-based geomagnetic compass and the origins of the directional response. It emerges that the anisotropy of radical pairs formed from spin-polarized molecular triplets could form the basis of a more sensitive compass sensor than one founded on the conventional hyperfine-anisotropy model. This property offers new and more flexible opportunities for the design of biologically inspired magnetic compass sensors

Structure–Function Relationship of Organic Semiconductors: Detailed Insights From Time-Resolved EPR Spectroscopy

Organic photovoltaics (OPV) is a promising technology to account for the increasing demand for energy in form of electricity. Whereas the last decades have seen tremendous progress in the field witnessed by the steady increase in efficiency of OPV devices, we still lack proper understanding of fundamental aspects of light-energy conversion, demanding for systematic investigation on a fundamental level. A detailed understanding of the electronic structure of semiconducting polymers and their building blocks is essential to develop efficient materials for organic electronics. Illuminating conjugated polymers not only leads to excited states, but sheds light on some of the most important aspects of device efficiency in organic electronics as well. The interplay between electronic structure, morphology, flexibility, and local ordering, while at the heart of structure—function relationship of organic electronic materials, is still barely understood. (Time-resolved) electron paramagnetic resonance (EPR) spectroscopy is particularly suited to address these questions, allowing one to directly detect paramagnetic states and to reveal their spin-multiplicity, besides its clearly superior spectral resolution compared to optical methods. This article aims at giving a non-specialist audience an overview of what EPR spectroscopy and particularly its time-resolved variant (TREPR) can contribute to unraveling aspects of structure–function relationship in organic semiconductors

Strategie, Kommunikation und Pilotierung

Am Bundesinstitut für Risikobewertung (BfR) ist das Forschungsdatenmanagement (FDM) als Bestandteil des wissenschaftlichen Forschungszyklus definiert. Der Fokus liegt darauf, dass FDM-Konzepte, -Methoden und -Dienstleistungen auf allen Ebenen einer öffentlichen Einrichtung berücksichtigt werden müssen: auf politischer, strategischer und operativer Ebene für verschiedene Interessengruppen in der Forschung, IT und auf Leitungsebene. Der Aufbau des FDM am BfR steht darüber hinaus vor der Herausforderung, die gesetzlichen Regelungen des E-Government-Gesetzes sowie die Koordination mit den weiteren Ressortforschungseinrichtungen unter der Leitung des Bundesministeriums für Ernährung und Landwirtschaft in seinem FDM-Framework einzubinden. Das in diesem Beitrag vorgestellte FDM-Framework des BfR basiert auf einem FDM-Konzept, das auf drei Säulen aufgebaut ist: Strategie, Kommunikation und Pilotierung. In einer ersten Pilotphase startet das BfR 2022 die Etablierung eines institutionellen FDM. Dieser Beitrag stellt das FDM-Framework am BfR vor und beschreibt erste Beispiele für die Umsetzung

All-optical manipulation of singlet exciton transport in individual supramolecular nanostructures by triplet gating

Directed transport of singlet excitation energy is a key process in natural light-harvesting systems and a desired feature in assemblies of functional organic molecules for organic electronics and nanotechnology applications. However, progress in this direction is hampered by the lack of concepts and model systems. Here we demonstrate an all-optical approach to manipulate singlet exciton transport pathways within supramolecular nanostructures via singlet-triplet annihilation, i.e., to enforce an effective motion of singlet excitons along a predefined direction. For this proof-of-concept, we locally photo-generate a long-lived triplet exciton population and subsequently a singlet exciton population on single bundles of H-type supramolecular nanofibres using two temporally and spatially separated laser pulses. The local triplet exciton population operates as a gate for the singlet exciton transport since singlet-triplet annihilation hinders singlet exciton motion across the triplet population. We visualize this manipulation of singlet exciton transport via the fluorescence signal from the singlet excitons, using a detection-beam scanning approach combined with time-correlated single-photon counting. Our reversible, all-optical manipulation of singlet exciton transport can pave the way to realising new design principles for functional photonic nanodevices

Direct Detection of Photoinduced Charge Transfer Complexes in Polymer:Fullerene Blends

We report transient electron paramagnetic resonance (trEPR) measurements with sub-microsecond time resolution performed on a P3HT:PCBM blend at low temperature. The trEPR spectrum immediately following photoexcitation reveals signatures of spin-correlated polaron pairs. The pair partners (positive polarons in P3HT and negative polarons in PCBM) can be identified by their characteristic g-values. The fact that the polaron pair states exhibit strong non-Boltzmann population unambiguously shows that the constituents of each pair are geminate, i.e. originate from one exciton. We demonstrate that coupled polaron pairs are present even several microseconds after charge transfer and suggest that they embody the intermediate charge transfer complexes which form at the donor/acceptor interface and mediate the conversion from excitons into free charge carriers

Double Doping of a Low-Ionization-Energy Polythiophene with a Molybdenum Dithiolene Complex

Doping of organic semiconductors is crucial for tuning the charge-carrier density of conjugated polymers. The exchange of more than one electron between a monomeric dopant and an organic semiconductor allows the polaron density to be increased relative to the number of counterions that are introduced into the host matrix. Here, a molybdenum dithiolene complex with a high electron affinity of 5.5 eV is shown to accept two electrons from a polythiophene that has a low ionization energy of 4.7 eV. Double p-doping is consistent with the ability of the monoanion salt of the molybdenum dithiolene complex to dope the polymer. The transfer of two electrons to the neutral dopant was also confirmed by electron paramagnetic resonance spectroscopy since the monoanion, but not the dianion, of the molybdenum dithiolene complex features an unpaired electron. Double doping allowed an ionization efficiency of 200% to be reached, which facilitates the design of strongly doped semiconductors while lessening any counterion-induced disruption of the nanostructure

Chemical Doping of Conjugated Polymers with the Strong Oxidant Magic Blue

Molecular doping of organic semiconductors is a powerful tool for the optimization of organic electronic devices and organic thermoelectric materials. However, there are few redox dopants that have a sufficiently high electron affinity to allow the doping of conjugated polymers with an ionization energy of more than 5.3\ua0eV. Here, p-doping of a broad palette of conjugated polymers with high ionization energies is achieved by using the strong oxidant tris(4-bromophenyl)ammoniumyl hexachloroantimonate (Magic Blue). In particular diketopyrrolopyrrole (DPP)-based copolymers reach a conductivity of up to 100 S cm−1 and a thermoelectric power factor of 10 \ub5W m−1 K−2. Further, both electron paramagnetic resonance (EPR) as well as a combination of spectroelectrochemistry and chronoamperometry is used to estimate the charge-carrier density of the polymer PDPP-3T doped with Magic Blue. A molar attenuation coefficient of 6.0\ua0\ub1\ua00.2 7 103 m2 mol−1 is obtained for the first polaronic sub-bandgap absorption of electrochemically oxidized PDPP-3T. Comparison with chemically doped PDPP-3T suggests a charge-carrier density on the order of 1026 m−3, which yields a charge-carrier mobility of up to 0.5 cm2 V−1 s−1 for the most heavily doped material

Neurologic phenotypes associated with COL4A1/2 mutations

Objective: To characterize the neurologic phenotypes associated with COL4A1/2 mutations and to seek genotype–phenotype correlation. Methods: We analyzed clinical, EEG, and neuroimaging data of 44 new and 55 previously reported patients with COL4A1/COL4A2 mutations. Results: Childhood-onset focal seizures, frequently complicated by status epilepticus and resistance to antiepileptic drugs, was the most common phenotype. EEG typically showed focal epileptiform discharges in the context of other abnormalities, including generalized sharp waves or slowing. In 46.4% of new patients with focal seizures, porencephalic cysts on brain MRI colocalized with the area of the focal epileptiform discharges. In patients with porencephalic cysts, brain MRI frequently also showed extensive white matter abnormalities, consistent with the finding of diffuse cerebral disturbance on EEG. Notably, we also identified a subgroup of patients with epilepsy as their main clinical feature, in which brain MRI showed nonspecific findings, in particular periventricular leukoencephalopathy and ventricular asymmetry. Analysis of 15 pedigrees suggested a worsening of the severity of clinical phenotype in succeeding generations, particularly when maternally inherited. Mutations associated with epilepsy were spread across COL4A1 and a clear genotype–phenotype correlation did not emerge. Conclusion: COL4A1/COL4A2 mutations typically cause a severe neurologic condition and a broader spectrum of milder phenotypes, in which epilepsy is the predominant feature. Early identification of patients carrying COL4A1/COL4A2 mutations may have important clinical consequences, while for research efforts, omission from large-scale epilepsy sequencing studies of individuals with abnormalities on brain MRI may generate misleading estimates of the genetic contribution to the epilepsies overall

Strategie, Kommunikation und Pilotierung : Die drei Säulen zur Implementierung des forschungsorientierten Forschungsdatenmanagements am Bundesinstitut für Risikobewertung

Am Bundesinstitut für Risikobewertung (BfR) ist das Forschungsdatenmanagement (FDM) als Bestandteil des wissenschaftlichen Forschungszyklus definiert. Der Fokus liegt darauf, dass FDM-Konzepte, -Methoden und -Dienstleistungen auf allen Ebenen einer öffentlichen Einrichtung berücksichtigt werden müssen: auf politischer, strategischer und operativer Ebene für verschiedene Interessengruppen in der Forschung, IT und auf Leitungsebene. Der Aufbau des FDM am BfR steht darüber hinaus vor der Herausforderung, die gesetzlichen Regelungen des E-Government-Gesetzes sowie die Koordination mit den weiteren Ressortforschungseinrichtungen unter der Leitung des Bundesministeriums für Ernährung und Landwirtschaft in seinem FDM-Framework einzubinden. Das in diesem Beitrag vorgestellte FDM-Framework des BfR basiert auf einem FDM-Konzept, das auf drei Säulen aufgebaut ist: Strategie, Kommunikation und Pilotierung. In einer ersten Pilotphase startet das BfR 2022 die Etablierung eines institutionellen FDM. Dieser Beitrag stellt das FDM-Framework am BfR vor und beschreibt erste Beispiele für die Umsetzung

LabInform: A Modular Laboratory Information System Built From Open Source Components

A framework for reproducible data analysis is only half the battle if it comes to reproducible research. Additional essential requirements are a way to safely store both, raw data and metadata and a method to uniquely refer to a dataset or any piece of information. Such unique identifier is fully independent of the actual place the information referred to is stored and does not change over time. Additionally, numeric IDs for samples and alike come in quite handy. A knowledge base and an electronic lab notebook, both based on wiki software and thus easily accessible requiring only a web browser and connection to the intranet, complete the system. Overarching design rules are simplicity, robustness and sustainability, focussing on small-scale deployment of the system retaining compatibility with future developments and community efforts. Key aspects in setting up the system are its use of well-proven open-source tools combined with maximal modularity, resulting in a low entry threshold and allowing to implement and develop it along the way of focussing on actual research