RESUMEN
Collagen is one of the most important biomaterials for tissue engineering approaches. Despite its excellent biocompatibility, it shows the non-negligible disadvantage of poor mechanical stability. Photochemical crosslinking with rose bengal and green light (RGX) is an appropriate method to improve this property. The development of collagen laminates is helpful for further adjustment of the mechanical properties as well as the controlled release of incorporated substances. In this study, we investigate the impact of crosslinking and layering of two different collagen scaffolds on the swelling behavior and mechanical behavior in micro tensile tests to obtain information on its wearing comfort (stiffness, strength and ductility). The mechanical stability of the collagen material after degradation due to cell contact is examined using thickness measurements. There is no linear increase or decrease due to layering homologous laminates. Unexpectedly, a decrease in elongation at break, Young's modulus and ultimate tensile strength are measured when the untreated monolayer is compared to the crosslinked one. Furthermore, we can detect a connection between stability and cell proliferation. The results show that with variation in number and type of layers, collagen scaffolds with tailored mechanical properties can be produced. Such a multi-layered structure enables the release of biomolecules into inner or outer layers for biomedical applications.
RESUMEN
We developed an upcycling process of polyurethane obtaining porous nitrogen-doped carbon materials that were applied in supercapacitor electrodes. In detail, a mechanochemical solvent-free one-pot synthesis is used and combined with a thermal treatment. Polyurethane is an ideal precursor already containing nitrogen in its backbone, yielding nitrogen-doped porous carbon materials with N content values of 1-8 wt %, high specific surface area values of up to 2150 m2·g-1 (at a N content of 1.6 wt %) and large pore volume values of up to 0.9 cm3·g-1. The materials were tested as electrodes for supercapacitors in aqueous 1 M Li2SO4 electrolyte (100 F·g-1), organic 1 M TEA-BF4 (ACN, 83 F·g-1) and EMIM-BF4 (70 F·g-1).
RESUMEN
The identification and quantification of reaction intermediates and products in a time-resolved fashion is of great value for the understanding of mechanisms underlying the electro-catalytic oxidation of alcohols. Using a newly developed in situ cell, the identification of different intermediates, products, and side products became possible by monitoring the ethanol electro-oxidation in operando by 13C NMR spectroscopy.
RESUMEN
Highly selective electrooxidation catalysts were synthesized by functionalizing a commercially available reference electrooxidation catalyst (Pt/Vulcan XC 72R) with a coating of the highly hydrophobic porous zeolitic imidazolate framework ZIF-8, an adsorbent with high affinity for the extraction of aliphatic alcohols from water. According to cyclovoltammetric studies in alkaline media at 25 °C, the ZIF-8 functionalized catalyst shows a high selectivity for the electrooxidation of small alcohols such as ethanol and methanol over more hydrophobic alcohols ( n-butanol, n-propanol). In contrast, the noncoated reference catalyst (Pt/Vulcan XC 72R) oxidizes all investigated alcohols with comparable current densities. Tafel curves confirm these observations and indicate a limited conversion of long chain alcohols, especially n-butanol, caused by the high affinity of the ZIF-8 for this molecule resulting in significant diffusion limitations.
