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Methoxy substitution at acceptor end of TPA-acetophenone fluorophore showed white light emission, tunable emission by morphological transformation and mechano-responsive reversible fluorescence switching. [Display omitted] • White light emission from single fluorophore by methoxy substitution. • Tunable fluorescence by methoxy substitution and morphological transformation. • Fluorescent polymorphs with tunable emission. • Stimuli-responsive reversible and self-reversible fluorescence switching. Introducing methoxy substituent into triphenylamine-acetophenone based donor-π-acceptor fluorophore, 3-(4-(diphenylamino)phenyl)-1-phenylprop-2-en-1-one (1), produced strong solvatofluorochromism including white light emission, fluorescent polymorphs and mechano-responsive fluorescence switching. The unsubstituted and methoxy substituted compounds displayed strong solvent polarity mediated tunable emission in the solution. Interestingly, 3-(4-(diphenylamino)phenyl)-1-(4-methoxyphenyl)prop-2-en-1-one (2) and 3-(4-(diphenylamino)-2-methoxyphenyl)-1-(4-methoxyphenyl)prop-2-en-1-one (3) showed single molecule white light emission in DMSO and ethanol, respectively. 1-3 exhibited strong green/yellow fluorescence in the solid-state (Quantum yield (Φ f) = 10 to 23%). 2 produced fluorescent polymorphs (green (2-G) and yellow (2-Y). Single crystal structural analysis revealed that donor and acceptor phenyl units adopted coplanar conformation in 2-G and 3 whereas twisted molecular conformation in 1 and 2-Y. Further, 2-G exhibited π...π interactions facilitated isolated dimers whereas 2-Y showed well separated molecules in the crystal lattice. Aggregation induced emission (AIE) studies showed morphological transformation induced fluorescence tuning for 2. The intramolecular charge transfer (ICT) from TPA to acetophenone was confirmed by computational studies. Mechanofluorochromic (MFC) studies of 1 showed only slight reduction of intensity without modulating fluorescence wavelength significantly but 2 and 3 exhibited visible emissive colour change from yellow to green and vice versa by crushing and heating. Both 2 and 3 also exhibited self-reversible fluorescence switching that was confirmed by PXRD pattern. Thus, methoxy group introduction resulted in obtaining white light emitting fluorescence molecules in the solution state and self-reversible fluorescence switching materials. [ABSTRACT FROM AUTHOR]

Triphenylamine (TPA) based di-aldehyde fluorophores have been synthesised and utilized for fabricating solid thin film fluorescence assay for hydrazine sensing and rewritable fluorescence platform. Addition of hydrazine reacts with aldehyde and strongly quenched the fluorescence intensity in solutions. Interestingly, fluorophores integrated into PMMA thin films showed strong blue fluorescence and exhibited turn-off fluorescence upon immersing in hydrazine solution (5%) and turn-on fluorescence by immersing in acetic acid (5%). Concentration dependent studies revealed the limit of detection (LOD) of 9.3–14.0 μM in solution and 0.021% by solid matrix. Reversible off-on fluorescence switching both in solution and PMMA matrix has been achieved by acid and base exposure that has been successfully used for demonstrating rewritable fluorescent platforms. Reusable solid fluorescent sensor and rewritable fluorescent platforms have been developed by integrating di-triphenylamine aldehyde fluorophore with PMMA matrix. Image 1 • Halochromic off-on fluorescence switching in solution as well as solid state. • Fabrication of rewritable fluorescence platforms. • Selective fluorescence sensing hydrazine. • PMMA based reusable solid fluorescence assay for hydrazine. [ABSTRACT FROM AUTHOR]