Research Projects

Organic luminescent materials (OLMs) with photothermally reversible luminescence (PTRL) features in solid states hold promise for applications like photosensitization, photon energy storage, data security, and optoelectronics. These materials achieve their effects through photo-thermal isomerization, a process where molecular bonds break and reform. Researchers are working on organic switches that shift to a metastable form, storing photon energy within chemical bonds. Fluorescence switches (FS) are common in sensing and imaging. However, creating PTRL switching remains challenging. Current FSs are often limited to liquid media, where photoluminescence quenching occurs due to aggregation and direct UV excitation, which leads to byproduct formation from high-energy UV irradiation. The main challenge is enabling PTRL through indirect photoexcitation or visible light excitation, especially in solid phases. Integrating PTRL with triplet-harnessing features into a single molecular design is also crucial. In this context, interest has grown in harvesting triplet energy via delayed fluorescence, which converts triplet excitons into singlet states. Achieving ambient phosphorescence from organic systems remains challenging, as triplet states are sensitive to thermal vibrations and oxygen exposure. Developing visible-light-activated PTRL switches for reversible triplet switching has become a pressing need. This project aims to design visible light-absorbing organic donor-acceptor conjugates with photothermally active chromophores (PACs), like norbornadiene, to optimize the singlet-triplet energy gaps (ΔEST) by separating HOMO and LUMO regions. Another goal is to create organic triplet photosensitizers that use Dexter-energy transfer to indirectly excite photo-switches, enabling photothermally reversible luminescence (PTRL) in solid states. To achieve this, we’ll design donor-acceptor conjugates linked through single C–N or C–C bonds, forming twisted geometries. Each donor and acceptor component will be functionalized with PACs. Multiple donor-acceptor conjugates will be integrated into a single cyclic system, enhancing visible light absorption and triplet harnessing. Donors will include carbazole, 9-phenylcarbazole, triphenylamine, phenoxazine, and 10H-phenothiazine, while acceptors will feature quinoline, quinoxaline, benzonitrile, and triazine derivatives. These carefully crafted structures, with minimized ΔEST, will support efficient PTRL through indirect excitation, broadening applications for solid-state luminescent materials. This project offers young researchers hands-on training with advanced characterization techniques. Detailed PTRL and PL analyses will reveal valuable insights into photochemistry and photophysics, while quantum chemistry calculations will define HOMO/LUMO and energy levels. Researchers will then assemble and optimize PTRLs for real-world applications.