Publikationen

This study presents the development of a hierarchical design concept for the synthesis of multi-scale polymer particles with up to five levels of organization. The synthesis of core-shell microparticles containing nested sets of dispersed metal and polymer micro- and nanoparticles is achieved through in situ photopolymerization using a double co-axial capillaries microfluidic device. The flow rates of the carrier, shell, and core phases are optimized to control particle size and result in stable core-shell particles with well-dispersed three-level composites in the shell matrix. The robustness and reversibility of these core-shell particles are demonstrated through five cycles of drying and re-swelling, showing that the size and structure of core-shell particles remain unchanged. Additionally, the permeability and mobility of dye molecules within the shell matrix are tested and showed that different molecular weight dyes have different penetration times. This study highlights the potential of microfluidics as a powerful tool for the controlled and precise synthesis of complex structured materials and demonstrates the versatility and potential of these core-shell particles for sensing applications as particle-based surface-enhanced Raman scattering (SERS).

Online NMR measurements are introduced in the current study as a new analytical setup for investigation of the oxymethylene dimethyl ether (OME) synthesis. For the validation of the setup, the newly established method is compared with state-of-the-art gas chromatographic analysis. Afterwards, the influence of different parameters, such as temperature, catalyst concentration and catalyst type on the OME fuel formation based on trioxane and dimethoxymethane is investigated. As catalysts, AmberlystTM 15 (A15) and trifluoromethanesulfonic acid (TfOH) are utilized. A kinetic model is applied to describe the reaction in more detail. Based on these results, the activation energy (A15: 48.0 kJ mol^-1 and TfOH: 72.3 kJ mol^-1) and the order in catalyst (A15: 1.1 and TfOH: 1.3) are calculated and discussed.

Graphene oxide (GO) derived from the oxidization of graphite exhibits high specific surface area with potential in electrochemical applications. Furthermore, silver and zinc oxide nanoparticles, further denoted as AgNPs and ZnONPs, respectively, display superior physicochemical and electronic properties, that would significantly improve the electrocatalytic properties by being applied in electrochemical sensing. Consequently, in the present work, three different hybrid nanomaterials consisting of reduced graphene oxide (rGO) modified with either AgNPs, ZnONPs, or combined AgZnONPs were synthesized and characterized. The synthesis of GO was performed by a modified Hummer's method, while the decoration of GO with the nanoparticles was carried out by self-assembly solvothermal processes. The Ag-rGO, ZnO-rGO, and AgZnO-rGO nanocomposite hybrid materials were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), Raman spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) combined with energy-dispersive X-ray spectroscopy (EDX). Furthermore, the electrochemical responses of the fabricated nanocomposites towards the standard ferrocyanide/ferricyanide [Fe(CN)6]3-/4- redox system were investigated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. The results have been explained in terms of structural differences between the nanoparticles formed on the surface of the fabricated nanocomposite materials. Namely, the improved electrochemical performance of ZnO-rGO can be attributed to the high surface to volume ratio of ZnO, which provides greater area of electrode/electrolyte junction and consequently, large number of sites at the electrolyte-ZnO interface. The aim of the present work is the fabrication of novel high-performance rGO-based nanomaterials for applications in electrochemical sensing.

As a potential anode material for potassium-ion batteries (PIBs), bimetallic sulfides are favored by researchers for their high specific capacity, low cost, and long cycle life. However, the non-ideal diffusion rate and poor cycle stability pose significant challenges in practical applications. In this work, bimetallic sulfide CuSbSyC with a yolk-shell structure was synthesized by in situ precipitation and carbonization. When CuSbSy is applied in the anode of PIBs, it can provide the desired capacity and reduce the volume expansion of the compound through the synergistic effect between copper and antimony. At the same time, the existence of the nitrogen-doped carbon shell confines the material within the shell while improving its electrical conductivity, inhibiting its volume expansion and aggregation. Therefore, CuSbSy@C exhibits a satisfactory capacity (438.8 mAh g^-1 at 100 mA g^-1 after 60 cycles) and an excellent long cycle life (174.5 mAh g^-1 at 1000 mA g^-1 after 1000 cycles).