Lardani Davide, Ronchi Alessandra, Hu Xueqian, Monguzzi Angelo, Weder Christoph
Adolphe Merkle Institute, University of Fribourg Chemin des Verdiers 4 1700 Fribourg Switzerland
Department of Material Science, University of Milano-Bicocca Via Roberto Cozzi 55 20125 Milan Italy
J Mater Chem C Mater. 2025 Aug 12. doi: 10.1039/d5tc02434j.
Ultraviolet (UV) light plays a central role in applications ranging from photochemistry to sterilization and water treatment. However, its low abundance in sunlight (∼10%) limits the direct solar use of UV-driven processes. Sensitized triplet-triplet annihilation upconversion (TTA-UC) offers a promising route to generate UV light from visible light under low-power excitation. Yet, molecular systems capable of efficient visible-to-UV TTA-UC remain scarce. Here, we demonstrate that 1,4-bis(phenylethynyl)benzene (BPEB) and its alkoxylated derivative serve as efficient UV-emitting annihilators when paired with the visible-light sensitizer Ir(ppy) in toluene solution. These systems achieve upconverted emission centered at 380 nm, with anti-Stokes shifts exceeding 0.6 eV with respect to excitation energy and threshold excitation intensities as low as 11.5 mW cm. Spectroscopic studies suggest that modulation of high-energy excited-state dynamics plays a key role in optimizing upconversion performance. By broadening the molecular design space of UV-emitting annihilators beyond traditional polycyclic aromatics, this study provides a foundation for future development of low-intensity visible-to-UV TTA-UC systems. These findings expand the molecular toolkit for photonic applications where UV emission from ambient light is required.
紫外线（UV）在从光化学到杀菌和水处理等一系列应用中发挥着核心作用。然而，其在阳光中的低丰度（约10%）限制了紫外线驱动过程对太阳能的直接利用。敏化三线态-三线态湮灭上转换（TTA-UC）提供了一条在低功率激发下从可见光产生紫外线的有前景的途径。然而，能够实现高效可见光到紫外线TTA-UC的分子体系仍然稀少。在此，我们证明1,4-双（苯乙炔基）苯（BPEB）及其烷氧基化衍生物与可见光敏化剂Ir(ppy)在甲苯溶液中配对时，可作为高效的紫外线发射湮灭剂。这些体系实现了以380 nm为中心的上转换发射，相对于激发能量的反斯托克斯位移超过0.6 eV，阈值激发强度低至11.5 mW/cm²。光谱研究表明，高能激发态动力学的调制在优化上转换性能中起关键作用。通过拓宽紫外线发射湮灭剂的分子设计空间，超越传统的多环芳烃，本研究为未来低强度可见光到紫外线TTA-UC体系的发展奠定了基础。这些发现扩展了用于需要从环境光发射紫外线的光子应用的分子工具包。
