DOI: 10.25442/hku.28692053
title: Supporting data for "STUDIES ON THE MECHANISM AND APPLICATION OF ORGANIC AFTERGLOW MATERIALS"

description: This PhD thesis explores the development and characterization of advanced organic afterglow materials through various innovative strategies. The research focuses on achieving multi-color emissions, high-temperature phosphorescence, stimuli-responsive afterglow, and narrowband emissions, addressing significant challenges in the field of organic afterglow materials and extending their potential applications in photodynamic therapy, bioimaging, data encryption, and medical cosmetology. The thesis begins with the synthesis and characterization of host–guest supramolecular complexes composed of α-cyclodextrin and diphenylacetylene (DPA) or its derivatives. These complexes exhibit dual afterglow emissions: thermally activated delayed fluorescence (TADF) and room temperature phosphorescence (RTP). The observed gradient color emission after UV excitation is attributed to a unique space charge transfer mechanism from α-cyclodextrin to DPA, facilitated by long-range carrier transportation. The hydrophobic nature of α-cyclodextrin enables the LPL to be switched on by shedding water and off by organic solvent infiltration, demonstrating a novel approach to designing switchable afterglow materials. Following this, the thesis explores two nucleic-acid-base cocrystal systems that mimic the strong hydrogen bond interactions found in complementary base pairing. These cocrystals display phosphorescence with distinct colors and rare high-temperature phosphorescence properties. The strong hydrogen bond network stabilizes the triplet state and suppresses non-radiative transitions, enabling phosphorescence even at 425 K. This stabilization allows for the generation of reactive oxygen species through energy transfer, which has practical applications in photodynamic therapy and broad-spectrum microbicidal effects. In vitro experiments demonstrate the efficacy of these cocrystals in preventing dental caries by efficiently killing bacteria on tooth surfaces. To address the challenge of achieving stimuli-responsive afterglow and bio-friendly excitation in organic afterglow materials, the study introduces host-guest complexes with temperature-responsive dual-color afterglow, excited by visible light and near-infrared laser light. By incorporating a classical photocatalyst into an organic/inorganic matrix, the hybrid system stabilizes the triplet state and enhances intersystem crossing, resulting in persistent TADF and ultralong organic phosphorescence. The complexes exhibit temperature-dependent color changes from green to white to blue as the temperature increases from 200 K to 350 K. The efficient generation of reactive oxygen species further broadens their potential applications in microbicidal and pigment degradation, with demonstrated efficacy in teeth whitening and dental caries prevention. These cocrystals display phosphorescence with distinct colors and rare high-temperature phosphorescence properties. The strong hydrogen bond network stabilizes the triplet state and suppresses non-radiative transitions, enabling phosphorescence even at 425 K. This stabilization allows for the generation of reactive oxygen species through energy transfer, which has practical applications in photodynamic therapy and broad-spectrum microbicidal effects. In vitro experiments demonstrate the efficacy of these cocrystals in preventing dental caries by efficiently killing bacteria on tooth surfaces. To address the challenge of achieving stimuli-responsive afterglow and bio-friendly excitation in organic afterglow materials, the study introduces host-guest complexes with temperature-responsive dual-color afterglow, excited by visible light and near-infrared laser light. By incorporating a classical photocatalyst into an organic/inorganic matrix, the hybrid system stabilizes the triplet state and enhances intersystem crossing, resulting in persistent TADF and ultralong organic phosphorescence. The complexes exhibit temperature-dependent color changes from green to white to blue as the temperature increases from 200 K to 350 K. The efficient generation of reactive oxygen species further broadens their potential applications in microbicidal and pigment degradation, with demonstrated efficacy in teeth whitening and dental caries prevention. The final part of the thesis focuses on the development of narrowband organic afterglow materials with small full-width at half-maximum (FWHM). By doping narrowband TADF fluorophores into a robust inorganic framework formed through melt-cooling treatment, three distinct host-guest complexes are created. These complexes exhibit narrowband emissions with a FWHM of 33 nm, long persistent afterglow times over 20 seconds, and a maximum photoluminescence quantum yield of 68.1%. The study elucidates the mechanisms underlying the transition from persistent TADF to dual-color afterglow and URTP, providing new insights into the regulation of afterglow materials for high color purity and performance. In summary, this thesis advances the understanding and development of afterglow materials with diverse emission properties and broad application potentials.