Two-dimensional structural ordering in a chromophoric ionic liquid for triplet energy migration-based photon upconversion

Abstract

A novel chromophoric ionic liquid (IL) with two-dimensional (2D) nanostructural order is developed, and its structure-property relationship is investigated by harnessing photon upconversion based on triplet energy migration. An ion pair of 9,10-diphenylanthracene-2-sulphonate (DPAS) and asymmetric quaternary phosphonium ion exhibited both ionic crystal (IC) and supercooled IL phases at room temperature. Single crystal X-ray analysis of the IC phase showed an alternate alignment of polar (ionic) and non-polar (non-ionic) layers, and this layered structure was basically maintained even in the IL phase. The diffusion length of triplet excitons in the IL phase, obtained by the analysis of upconverted emission in succession to triplet-triplet annihilation (TTA), is larger than the domain size estimated from powder X-ray analysis. This suggests that triplet excitons in chromophoric ILs can diffuse over the nanostructured domains.

Visible‐to‐UV Photon Upconversion in Nanostructured Chromophoric Ionic Liquids

“…The low‐angle peak at 2.7° of P 66614 PPOS was in accordance with those of the precursor IL P 66614 Cl and our previous blue‐emitting chromophoric IL having the same P 66614 cation . The distance of 1.75 nm corresponds to the separation between the ionic domains, which is mainly determined by the size of the bulky cation …”

“…This was also supported by the absence of sharp peaks in its synchrotron powder X‐ray diffraction (PXRD) pattern (Figure d). The PXRD pattern also indicated the existence of the bicontinuous network nanostructures in P 66614 PPOS composed of polar ionic and nonpolar alkyl/chromophore domains . The low‐angle peak at 2.7° of P 66614 PPOS was in accordance with those of the precursor IL P 66614 Cl and our previous blue‐emitting chromophoric IL having the same P 66614 cation .…”

“…The BET quantum yield ( Φ BET ) was evaluated as 31 % by analyzing the fluorescence lifetimes of neat P 66614 PPOS with and without Ir(ppy) 3 (Figure S5). Triplet excitons may also be trapped at the strongly‐interacting sites, as observed previously for the chromophoric IL …”

Photon-upconverting chiral liquid crystal: significantly amplified upconverted circularly polarized luminescence

“…The D sol value (in toluene solution) was calculated to be 4.3 × 10 –6 cm 2 s –1 . The triplet diffusion length L sol could be calculated using the following expression:48where τ T,sol is the lifetime of an acceptor excited triplet, namely twice the value of the lifetime of the upconversion (568 μs). The value of L sol (in toluene solution) was calculated to be 0.49 μm.…”

Photon upconverting bioplastics with high efficiency and in-air durability

“…However, fabricating efficient solidstate TTA-UC materials faces several challenges, such as aggregation-induced quenching of emitter fluorescence and triplet quenching by molecular oxygen in air. 45 Various solidstate TTA-UC materials developed to date include polymers doped with dye molecules, [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] dye nano/microparticles, [46][47][48] dye-bridged metal-organic frameworks (MOFs), [49][50][51][52][53][54][55][56] dye-based glasses, 57,58 and crystals. [59][60][61][62] Among these, the molecular diffusion (MD) based TTA-UC in soft synthetic polymers has been a simple and effective approach to achieve high TTA-UC efficiency even in air.…”