Transient and Persistent Room‐Temperature Mechanoluminescence from a White‐Light‐Emitting AIEgen with Tricolor Emission Switching Triggered by Light

Abstract

Persistent luminescence from purely organic materials is basically triggered by light and electricity,w hichl argely confines its practical applications.Apurely organic AIEgen exhibits not only persistent photoluminescence,b ut also transient and persistent room-temperature mechanoluminescence.B ys imply turning on and off aU Vl amp,t ricolor emission switching between blue,w hite,a nd yelloww as achieved. The data from single-crystal structure analysis and theoretical calculation suggest that mechanism of the observed persistent mechanoluminescence (pML) is correlated with the strong spin-orbit coupling of the bromine atom, as well as the formation of H-aggregates and restriction of intramolecular motions in noncentrosymmetric crystal structure.These results outline af undamental principle for the development of new pML materials,p roviding an important step forward in expanding the application scope of persistent luminescence.

A Metal–Organic Supramolecular Box as a Universal Reservoir of UV, WL, and NIR Light for Long‐Persistent Luminescence

“…Time-dependent DFT calculations were performed to explore the mechanism of the fluorescence and phosphorescence emissions of Cd 2 L 2 .The HOMO and LUMO orbitals of Cd 2 L 2 mainly reside on the biphenyl-tetrazole and terpyridine groups,r espectively,i na ccordance with the Dp-A nature of the ligand, and there exist multiple intersystem-crossing channels from the singlet to triplet transitions in Cd 2 L 2 (S 1 !T 2 -T 7 ,F igure 4a;s ee also Table S6). [11] The existence of multiple intersystem-crossing channels is favorable for the population of triplet exciton states and accounts for the generation of RTPand LPL in Cd 2 L 2 ,which are absent in the pure organic ligand. From the above experimental and theoretical results,w ep ropose the following energy-transfer mechanism for Cd 2 L 2 (Figure 1): First, the metal-organic supramolecules absorb UV/WL/NIR light energy through either the OPAorTPA pathway and transfer it to the excited singlet states S n ,w hich can emit blue fluorescence.A lternatively,S n states transit by intersystem crossing to the excited triplet states T n ,w hich then emit orange phosphorescence.…”

“…[1] In the past decades, an umber of LPL materials have been designed and synthesized by different methods,a nd have attracted considerable attention in various fields,i ncluding LEDs,d isplays and decorations,s ensors,a nti-counterfeiting barcodes,m ilitary night vision, and bioimaging labels. [8][9][10][11][12][13] However,t he LPL in materials explored so far is dominantly triggered by one-photon absorption (OPA) of UV light, although some recent studies have expanded the radiation to visible white light. Recently,o rganic-based LPL materials have been gradually developed by several strategies,including the construction of pure organic solids or host-guest cocrystals,m etal-organic hybrids and metal-organic frameworks.…”

“…Recently,o rganic-based LPL materials have been gradually developed by several strategies,including the construction of pure organic solids or host-guest cocrystals,m etal-organic hybrids and metal-organic frameworks. [8][9][10][11][12][13] However,t he LPL in materials explored so far is dominantly triggered by one-photon absorption (OPA) of UV light, although some recent studies have expanded the radiation to visible white light. [3,5] LPL excited by anear-infrared (NIR) source remains basically unknown, although it might have the merits of low energy and deep penetrability,and could be more applicable in such fields as biological imaging and military anti-counterfeiting.…”

Amorphous Ag2S Micro-rods-Enhanced Fluorescence on Liquid Crystals: Cation-π Interaction-Triggered Aggregation-Induced Emission Effect

“…However, the luminescent performance in liquid crystalline phase has been confined by the intense intermolecular interactions among the extremely ordered LC molecules for formation of π-π stacking interactions, which would lead to intrinsic self-quenching of a majority of luminogens, described as aggregation-caused quenching (ACQ) effects (Chiang et al., 2008, Grimsdale et al., 2009, Jiang et al., 2017). Recently, a novel photophysical phenomenon of aggregation-induced emission (AIE) was discovered based on some propeller-like organic molecules (Huang et al., 2018, Li et al., 2018, Luo et al., 2001, Sugiuchi et al., 2017, Zhao et al., 2018). Instead of the normally observed quenching in “conventional” luminophores, the restriction of intramolecular motion (RIM) (Chi et al., 2012, Mao et al., 2019, Mei et al., 2015, Zhang et al., 2015b) in aggregation state would intensify their fluorescence, transforming the weakly luminescent chromo-gens into fierce luminophores.…”

Colour-tunable ultralong organic phosphorescence upon temperature stimulus

“…[12][13][14] However, the luminescence of these materials with intelligent-response are mostly limited to uorescence or room temperature phosphorescence (RTP) with relatively short lifetimes. [15][16][17][18] Few samples display persistent luminescent feature. 19 Most organic compounds can only tune their aerglow properties by changing molecular side groups or multicomponent doping.…”