Wang Zhihang, Jones Beatrice E, Franca Larissa G, Lawson Takashi, Jevric Martyn, Moth-Poulsen Kasper, Evans Rachel C
Department of Materials Science and Metallurgy, University of Cambridge 27 Charles Babbage Road Cambridge CB3 0FS UK
Department of Chemistry and Chemical Engineering, Chalmers University of Technology Kemivagen 4 Gothenburg 412 96 Sweden.
J Mater Chem C Mater. 2024 Nov 26;12(47):19030-19034. doi: 10.1039/d4tc03513e. eCollection 2024 Dec 5.
Photoswitchable materials are of significant interest for diverse applications from energy and data storage to additive manufacturing and soft robotics. However, the absorption profile is often a limiting factor for practical applications. This can be overcome using indirect excitation complementary photophysical pathways, such as triplet sensitisation or photon upconversion. Here, we demonstrate the use of triplet-triplet annihilation upconversion (TTA-UC) to drive photoswitching of the energy storing photoswitch norbornadiene-quadricyclane (NBD-QC) in the solid-state. A photoswitchable bilayer polymer film, incorporating the TTA-UC sensitiser-emitter pair of platinum octaethylporphyrin (PtOEP) and 9,10-diphenylanthracene (DPA), was used to trigger the photoinduced [2+2] cycloaddition of NBD to form QC using visible instead of UV light. The isolated TTA-UC film showed green-to-blue upconversion, with a competitive upconversion efficiency of (1.9 ± 0.1%) for the solid-state in air. Direct photoswitching of the isolated NBD film was demonstrated with a narrow UV light source (340 nm). However, in the bilayer film, spectral overlap between the upconverted blue emission in the TTA-UC film and the absorbance band of the NBD film resulted in indirect photoswitching using visible green light (532 nm, 1 W cm), thus extending the spectral operational window of the photoswitching film. The results demonstrate proof-of-feasibility of TTA-UC-promoted photoswitching in the solid-state, paving the way for potential applications in light-harvesting devices and smart coatings, using a wider selection of irradiation wavelengths.
可光开关材料在从能量和数据存储到增材制造及软体机器人等各种应用中具有重大意义。然而，吸收光谱往往是实际应用中的一个限制因素。这可以通过间接激发互补光物理途径来克服，例如三线态敏化或光子上转换。在此，我们展示了利用三线态-三线态湮灭上转换（TTA-UC）来驱动固态储能光开关降冰片二烯-四环烷（NBD-QC）的光开关过程。一种包含TTA-UC敏化剂-发射体对铂八乙基卟啉（PtOEP）和9,10-二苯基蒽（DPA）的可光开关双层聚合物薄膜，被用于触发NBD的光致[2+2]环加成反应以形成QC，使用的是可见光而非紫外光。分离出的TTA-UC薄膜显示出从绿色到蓝色的上转换，在空气中固态时的上转换效率具有竞争力，为（1.9±0.1%）。使用窄紫外光源（340nm）证明了分离出的NBD薄膜的直接光开关过程。然而，在双层薄膜中，TTA-UC薄膜中向上转换的蓝色发射与NBD薄膜的吸收带之间的光谱重叠导致了使用可见光绿光（532nm，1W/cm）的间接光开关过程，从而扩展了光开关薄膜的光谱操作窗口。结果证明了TTA-UC促进的固态光开关的可行性，为在光捕获装置和智能涂层中的潜在应用铺平了道路，可使用更广泛的照射波长选择。
