Secondary structure formation in hybrid synthetic/peptide polymers: insights from molecular dynamics simulations. - In: Macromolecular theory and simulations, ISSN 1521-3919, Bd. 0 (2023), 0, 2200070, S. 1-8
Proteins and peptides exhibit an immense variety of structures, which are generally classified according to simple structural motifs (mainly α helices and β sheets). Considerable efforts have been invested in understanding the relationship between chemical structure (primary structure) of peptides and their spatial motifs (secondary structure). However, little is known about the possibility to interfere intentionally in these structural driving forces, for example, by inserting (short) artificial polymer chains in the peptide backbone. Structure formation on such hybrid synthetic/biochemical polymers is still an emerging field of research. Here, molecular dynamics simulations are used to illustrate the influence of inserted polyethylene segments on the secondary structure of several peptide homopolymers. A loss of structure of ≈50% when the peptide chain length drops to ten amino acids and a practically complete absence for even shorter peptide segments.
Thermally induced oxygen vacancies in BiOCl nanosheets and their impact on photoelectrochemical performance. - In: ChemPhotoChem, ISSN 2367-0932, Bd. 7 (2023), 3, e202200192, S. 1-9
Oxygen vacancies (OVs) have been reported to significantly alter the photocatalytic properties of BiOCl nanosheets. However, their formation mechanism and their role in the enhancement of photoelectrochemical performance remain unclear. In this work, thermally induced oxygen vacancies are introduced in BiOCl nanosheets by annealing in He atmosphere at various temperatures and their formation mechanism is investigated by in-situ diffuse reflectance infrared (DRIFTS) measurements. The influence of OVs on band offset, carrier concentrations and photoelectrochemical performance are systematically studied. The results show that (1) the surface of BiOCl nanosheets is extremely sensitive to temperature and defects are formed at temperatures as low as 200 ˚C in inert atmosphere. (2) The formation of surface and bulk OVs in BiOCl is identified by a combination of XPS, in-situ DRIFTS, and EPR experiments. (3) The photocurrent of BiOCl is limited by the concentration of charge carriers and shallow defect states induced by bulk oxygen vacancies, while the modulation of these parameters can effectively increase light absorption and carrier concentration leading to an enhancement of photoelectrochemical performance of BiOCl.
Multiplexed random-access optical memory in warm cesium vapor. - In: Optics express, ISSN 1094-4087, Bd. 31 (2023), 6, S. 10150-10158
The ability to store large amounts of photonic quantum states is regarded as substantial for future optical quantum computation and communication technologies. However, research for multiplexed quantum memories has been focused on systems that show good performance only after an elaborate preparation of the storage media. This makes it generally more difficult to apply outside a laboratory environment. In this work, we demonstrate a multiplexed random-access memory to store up to four optical pulses using electromagnetically induced transparency in warm cesium vapor. Using a Λ-System on the hyperfine transitions of the Cs D1 line, we achieve a mean internal storage efficiency of 36% and a 1/e lifetime of 3.2 µs. In combination with future improvements, this work facilitates the implementation of multiplexed memories in future quantum communication and computation infrastructures.
Analysis of a quasilinear coupled magneto-quasistatic model: solvability and regularity of solutions. - In: Journal of mathematical analysis and applications, ISSN 1096-0813, Bd. 523 (2023), 2, 127033
We consider a quasilinear model arising from dynamical magnetization. This model is described by a magneto-quasistatic (MQS) approximation of Maxwell's equations. Assuming that the medium consists of a conducting and a non-conducting part, the derivative with respect to time is not fully entering, whence the system can be described by an abstract differential-algebraic equation. Furthermore, via magnetic induction, the system is coupled with an equation which contains the induced electrical currents along the associated voltages, which form the input of the system. The aim of this paper is to study well-posedness of the coupled MQS system and regularity of its solutions. Thereby, we rely on the classical theory of gradient systems on Hilbert spaces combined with the concept of E-subgradients using in particular the magnetic energy. The coupled MQS system precisely fits into this general framework.
Changing the interaction of a single-molecule magnetic moment with a superconductor. - In: Nano letters, ISSN 1530-6992, Bd. 23 (2023), 4, S. 1622-1628
The exchange interaction of a brominated Co-porphyrin molecule with the Cooper pair condensate of Pb(111) is modified by reducing the Co-surface separation. The stepwise dehalogenation and dephenylation change the Co adsorption height by a few picometers. Only the residual Co-porphine core exhibits a Yu-Shiba-Rusinov bound state with low binding energy in the Bardeen-Cooper-Schrieffer energy gap. Accompanying density functional calculations reveal that the Co dz2 orbital carries the molecular magnetic moment and is responsible for the intragap state. The calculated spatial evolution of the Yu-Shiba-Rusinov wave function is compatible with the experimentally observed oscillatory attenuation of the electron-hole asymmetry with increasing lateral distance from the magnetic porphine center.
Ultrahigh-rate and ultralong-duration sodium storage enabled by sodiation-driven reconfiguration. - In: Advanced energy materials, ISSN 1614-6840, Bd. 0 (2023), 0, 2204324, S. 1-12
Despite their variable valence and favorable sodiation/desodiation potential, vanadium sulfides (VSx) used as anode materials of sodium-ion batteries (SIBs) have been held back by their capacity decline and low cycling capability, associated with the structure distortion volume expansion and pulverization. This study reports an accessible process to tackle these challenges via fabricating a 3D-VSx anode for SIBs with ultrahigh-rate and ultralong-duration stable sodium storage. The sodiation-driven reactivation of micro-nano 3D-VSx activates the reconfiguration effect, effectively maintaining structural integrity. Interestingly, the mechanical degradation of 3D-VSx over the sodiation process can be controlled by fine-tuning the operating voltage. The self-reconfigured open nanostructures with large void space not only effectively withstand repetitive volume changes and mitigate the damaging mechanical stresses, but also in turn construct a self-optimized shortened ion diffusion pathway. Moreover, the sodiation-driven reconfiguration excites many active sites and optimizes a stable solid-electrolyte interface, thereby delivering a reversible capacity of 961.4 mA h g^-1 after 1500 cycles at a high rate of 2 A g^-1. This work provides new insight into the rational design of electrodes toward long-lived SIBs through sodiation-driven reconfiguration.
Designing atomic interfaces in chalcogenides for boosting photocatalysis. - In: Solar RRL, ISSN 2367-198X, Bd. 0 (2023), 0, 2300025, S. 1-25
A deeper understanding of interfaces comes after the rapid development of nano-hybrids. Atomic interfaces with atomic-level thickness, intimate bonds, inferior charge-transport resistance, and robust stability have received escalating interest in the field of photocatalysis. Taking into account the fact that the carrier dynamics and spectrum response of candidate photocatalysts like chalcogenides remain suffering, sustained efforts are devoted. Hybridization, which is accompanied by interface designing, behaves as a supportive strategy to enlarge the photocatalytic output. Hence, the comprehensive survey for recent empirical studies on atomic interfaces in chalcogenides is highly desirable. Precisely, the fundamental of atomic interfaces, the devised approaches to design atomic interfaces in chalcogenides and their feasible roles for maneuvering photocatalysis, and the auxiliary advanced characterization are enumerated and summarized. The multifarious interaction of structure, chemical environment, optical and electric properties, and photocatalytic performance in chalcogenides with atomic interfaces is highlighted. Meanwhile, perspectives of atomic interfaces benefiting photocatalysis are given with a summary, and outlooks related to controllable architecture, nucleation mechanism, calculation, and the correlation between atomic interfaces and amended photocatalysis are presented discreetly. Herein, the review is meant to provide the first systematic account of designing atomic interfaces in chalcogenides served for ultimate photocatalytic applications.
Tapered cross section photoelectron spectroscopy provides insights into the buried interfaces of III-V semiconductor devices. - In: Advanced materials interfaces, ISSN 2196-7350, Bd. 10 (2023), 3, 2201648, S. 1-9
Interfaces are key elements that define electronic properties of the final device. Inevitably, most of the active interfaces of III-V semiconductor devices are buried and it is therefore not straightforward to characterize them. The Tapered Cross Section Photoelectron Spectroscopy (TCS-PES) approach is promising to address such a challenge. That the TCS-PES can be used to study the relevant heterojunction in epitaxial III-V architectures prepared by metalorganic chemical vapor deposition is demonstrated here. A MULTIPREP polishing system that enables controlling the angle between the sample holder and the polishing plate has been employed to improve the reproducibility of the polishing procedure. With this procedure, that preparing the TCS of III-V semiconductor devices with tapering angles lower than 0.02˚ is possible is demonstrated. The PES provides then information about the buried interfaces of Ge|GaInP and GaAs|GaInP layer stacks. Both, chemical and electronic properties have been measured by PES. It evidences that the preparation of the TCSs under an uncontrolled atmosphere modifies the pristine properties of the critical buried heterointerfaces. Surface states and reaction layers are created on the TCS surface, which restrict unambiguous conclusions on buried interface energetics.
Organic phase-change memory transistor based on an organic semiconductor with reversible molecular conformation transition. - In: Advanced science, ISSN 2198-3844, Bd. 10 (2023), 4, 2205694, S. 1-8
Phase-change semiconductor is one of the best candidates for designing nonvolatile memory, but it has never been realized in organic semiconductors until now. Here, a phase-changeable and high-mobility organic semiconductor (3,6-DATT) is first synthesized. Benefiting from the introduction of electrostatic hydrogen bond (S&hahog;&hahog;&hahog;H), the molecular conformation of 3,6-DATT crystals can be reversibly modulated by the electric field and ultraviolet irradiation. Through experimental and theoretical verification, the tiny difference in molecular conformation leads to crystalline polymorphisms and dramatically distinct charge transport properties, based on which a high-performance organic phase-change memory transistor (OPCMT) is constructed. The OPCMT exhibits a quick programming/erasing rate (about 3 s), long retention time (more than 2 h), and large memory window (i.e., large threshold voltage shift over 30 V). This work presents a new molecule design concept for organic semiconductors with reversible molecular conformation transition and opens a novel avenue for memory devices and other functional applications.
Silent death by sound: C60 fullerene sonodynamic treatment of cancer cells. - In: International journal of molecular sciences, ISSN 1422-0067, Bd. 24 (2023), 2, 1020, S. 1-17
The acoustic pressure waves of ultrasound (US) not only penetrate biological tissues deeper than light, but they also generate light emission, termed sonoluminescence. This promoted the idea of its use as an alternative energy source for photosensitizer excitation. Pristine C60 fullerene (C60), an excellent photosensitizer, was explored in the frame of cancer sonodynamic therapy (SDT). For that purpose, we analyzed C60 effects on human cervix carcinoma HeLa cells in combination with a low-intensity US treatment. The time-dependent accumulation of C60 in HeLa cells reached its maximum at 24 h (800 ± 66 ng/106 cells). Half of extranuclear C60 is localized within mitochondria. The efficiency of the C60 nanostructure’s sonoexcitation with 1 MHz US was tested with cell-based assays. A significant proapoptotic sonotoxic effect of C60 was found for HeLa cells. C60′s ability to induce apoptosis of carcinoma cells after sonoexcitation with US provides a promising novel approach for cancer treatment.