Stimuli-responsive fluorescence switching of novel aggregation-induced emission (AIE)-active fluorophores

• Main Author: Lee, Hung Jiang
• Other Authors: Lu Xuehong
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2024
• Subjects: Chemistry; Aggregation-induced emission; Mechanochromic luminescence
• Online Access: https://hdl.handle.net/10356/176585
• Institution: Nanyang Technological University

Compounds that exhibit both aggregation-induced emission (AIE) and mechanochromic luminescence (MCL) have sparked significant interest due to their wide range of potential applications such as optical data storage and security papers. In pursuit of novel organic small molecules that exhibit both AIE and MCL, a quintet of tetraphenylethene-derived compounds (C1-C5), each with distinct diarylamine donors was synthesised and systematically characterised. Their optical and MCL properties were then investigated. All compounds (C1-C5) displayed AIE and reversible MCL. High colour contrast reversible MCL behaviour from blue to yellow for C1, C2 and green to yellow for C3, C4 and C5 was observed. C2 displayed the largest grinding emission shift (Δλ) of 49 nm while C4 exhibited the lowest at 15 nm. Fuming with acetone could successfully restore the pristine state for all compounds while annealing was successful for only C3 and C4. The other compounds demonstrated partial or minimal recovery with annealing. A potential application of rewritable coloured paper was explored to confirm our analysis so far by coating the compounds onto filter and A4 papers. All compounds barring C2 were successful in the filter paper application. However, only C1 and C3 maintained this success in A4 paper application. In this case, annealing was deemed as the more effective recovery method due to the ease of performing it and its success in pristine fluorescence restoration. C1 and C3 are deemed the best performing compounds due to their relatively large (Δλ) of 40 nm and 22 nm, respectively, superior reversibility and success in potential real world applications. Thus, this research not only elucidates the optical properties of TPE-based organic small molecules but also show that subtle structural alterations can significantly steer their color-switching responses.