Publications

Nanosponges are subject of intensive research due to their unique morphology, which leads among other effects to electrodynamic field localization generating a strongly nonlinear optical response at hot spots and thus enable a variety of applications. Accurate predictions of physical properties require detailed knowledge of the sponges’ chaotic nanometer-sized structure, posing a metrological challenge. A major goal is to obtain computer models with equivalent structural and optical properties. Here, to understand the sponges’ morphology, we present a procedure for their accurate 3D reconstruction using focused ion beam tomography. Additionally, we introduce a simulation method to create nanoporous sponge models with adjustable geometric properties. It is shown that if certain morphological parameters are similar for computer-generated and experimental sponges, their optical response, including magnitudes and hot spot locations, are also similar. Finally, we analyze the anisotropy of experimental sponges and present an easy-to-use method to reproduce arbitrary anisotropies in computer-generated sponges.

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.

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.

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.

In this paper, we study several classes of set-valued maps, which can be used in set-valued optimization and its applications, and their respective maximum and minimum value functions. The definitions of these maps are based on scalar-valued, vector-valued, and cone-valued maps. Moreover, we consider those extremal value functions which are obtained when optimizing linear functionals over the image sets of the set-valued maps. Such extremal value functions play an important role for instance for derivative concepts for set-valued maps or for algorithmic approaches in set-valued optimization. We formulate conditions under which the set-valued maps and their extremal value functions inherit properties like (Lipschitz-)continuity and convexity.