Protonation-induced fluorescence modulation of carbazole-based emitters

Abstract

The development of high-efficiency organic light-emitting diodes is of great importance for the growing lighting and display technologies. A potential way of responding to this demand is thermally activated delayed...

A proton-assisted AIE active luminescent material having tunable emission in solution and solid state for anti-counterfeiting application: smart high contrast on–off–on fluorescence switch

“…Usually, the quenching of fluorescence in a twisted structure of a molecule is a result of the excited state energy consumed by the rotary motion of the molecule. 19,21…”

“…Usually, the quenching of fluorescence in a twisted structure of a molecule is a result of the excited state energy consumed by the rotary motion of the molecule. 19,21 Anti-counterfeiting application Nowadays, it is a very serious global problem of illegal trafficking of counterfeit goods as a huge money-making source for organized crimes. 31,32 Thus, developing powerful anticounterfeiting technologies for security is highly demanding.…”

“…14,15 The bipolar host materials containing both electron donating and electron-withdrawing units have been paid increasing attention in a smarter emitter design approach. [16][17][18] The design of bipolar host molecules having spatially separated donor with HOMO and acceptor LUMO favors the development of an intramolecular charge transfer (ICT) state, and this may show a twisted structure consequence to the excited state energy being utilized by the rotary motion of the molecule, [19][20][21] resulting in the quenching of fluorescence and low emission quantum yield.…”

“…This occurrence, together with alterations in the electronic profile due to protonation, elucidate the bathochromic shift of the fluorescence spectra with the enhancement in fluorescence quantum yield. 21,26,27 However, the enhancement of fluorescence quantum yield of DPABHz in solid-state occurs due to the protonation of -NH 2 group. However, no such noticeable increase in the fluorescence quantum yield of its parent molecule DPAB was observed upon protonation.…”

The emission efficiency of cationic solid state luminophores is directly proportional to the intermolecular charge transfer intensity

“…8 b ,10 In particular, Py + -containing luminophores have demonstrated dual emission, 11 aggregation induced emission (AIE) 8,10,12 and thermally activated delayed fluorescence (TADF) behavior. 13 Notably, charged π + -system-containing emitters display high emission efficiency also in solution 14 and have found applications in sensing of alkylating reagents 15 as well as reversible solid 10 c and solution state 16 sensing of acids.…”