The 14th Global Conference on Materials Science and Engineering
(CMSE 2025)

Abstract: To be updated

Abstract: The hardness of the contact surface of carbonitrided JIS-SCM420 low-alloy steel is higher than that of carburized one after the rolling-sliding contact fatigue test, which shows the greater resistance of the former to temper softening. The tangential force decreases until 1.0 × 10⁴ cycles and then increases gradually. Tribofilms are formed after 10⁴ cycles, and these cycles are fitted to the transition of the tangential forces. In the subzero-treated material, a crack formed vertically from a horizontal crack in the interior to the contact surface. The depth at which the horizontal crack formed corresponds to the maximum-shear-stress regime. In addition to the maximum-shear-strain regime, severe plastic deformation may generate horizontal microcracks in the interior of the specimen. Subsequently, the crack can propagate vertically to the rolling surface, where tensile stress is exerted, thus opening the subsurface crack. In the non-subzero-treated material, cracks formed on the surface and are connected to voids in the interior of the specimen. Solid dissolved nitrogen can create N₂ gas voids that change the direction of crack propagation.

Abstract: Flavins have emerged as promising photocatalysts for organic transformations, yet their practical application faces significant challenges, including synthetic accessibility, photostability, solubility, and tunable redox properties. We aims to establish general design principles for sustainable, high-performance flavin derivatives tailored for photocatalysis. By systematically exploring structural variations, we investigate how modifications to the flavin core—such as isoalloxazines, alloxazines, and deazaflavins—impact key properties like absorption spectra, triplet state energetics, and singlet oxygen generation. Our approach integrates experimental studies with quantum chemical calculations to optimize photophysical and redox properties, enabling the use of mild visible light sources and enhancing catalytic efficiency.

A major focus is on tuning singlet oxygen production for selective oxygenation reactions while minimizing unwanted side reactions. We also explore strategies to extend absorption into the red region, enabling photocatalysis with low-energy light and reducing substrate degradation. Additionally, we address photobleaching and stability issues by optimizing flavin structures and exploring alternative oxidants for catalyst regeneration. The results highlight the potential of tailored flavin derivatives for diverse photocatalytic applications, including sulfoxidations, benzylic oxidations, and energy-transfer cycloadditions. This work provides a roadmap for the rational design of flavin-based photocatalysts, bridging the gap between fundamental research and practical implementation in sustainable chemistry.

Keywords: Flavins, spectroscopy, photocatalysis, photochemistry, singlet oxygen

Acknowledgements: This work was supported by the Czech Science Foundation (Grant No 24-11386K) and by the research grant WEAVE-UNISONO UMO-2023/05/Y/ST4/00062, from The National Science Centre of Poland (NCN).