Photoreversible On–Off Recording of Persistent Room‐Temperature Phosphorescence

Abstract

allow the movement of the targets to be detected, even when their motion is slow. Therefore, promising materials and techniques that enable clear detection of the local motion of an individual target independent of the persistent emission around the target and autofl uorescence still need to be designed. Photoactivated fl uorescent materials have been developed for highdensity recording and super-resolution imaging. [6][7][8][9][10][11][12] Some systems containing a fl uorescent compound and photochromic compound have also been reported. [8][9][10] The fl uorescence of the emissive materials is switched off and on by effi cient energy transfer from the fl uorescent compound to the photochromic one, which is triggered by photoisomerization of the photochromic compound. If persistent luminescent materials with the ability to be photoactivated can be prepared, the resulting photoactivated persistent emission process will potentially be useful for tracking the local movement of the target independent of other persistent emitting signals around the target as well as background autofl uorescence. However, persistent luminescence is commonly observed from rare metal-doped metal oxides [ 1,2,5 ] and it is still diffi cult to fabricate photoactivated metal oxide particles. Another approach that differs from conventional metal oxide-based persistent emitters is persistent room-temperature phosphorescence (RTP), which has a lifetime approaching one second and has recently been observed from purely organic amorphous [ 13 ] and crystalline materials. [ 14 ] The amorphous materials displaying RTP are composed of a metal-free aromatic guest in an amorphous hydroxyl steroidal host, which is rigid with an oxygen barrier because of its intermolecular hydrogen bonding. The rigidity and oxygen barrier of the steroidal host minimize the nonradiative deactivation from the triplet excited state of the purely organic guest caused by thermal relaxation and oxygen diffusion, resulting in effi cient persistent RTP from the guest species. In such amorphous host-guest materials, the rigidity and oxygen barrier of the amorphous hydroxyl steroidal host around the persistent RTP guest should remain when a small amount of photochromic compound is doped into the host as another guest. Therefore, we anticipate that effi cient energy transfer processes from the guest exhibiting persistent RTP to that exhibiting photochromism should occur in the amorphous hydroxyl steroidal host through photoisomerization of the photochromic compound, which should subsequently trigger on-off switching of persistent RTP.

Dynamic Ultralong Organic Phosphorescence by Photoactivation

“…Ultralong phosphorescence with al ong-lived excited state,t hat is,p ersistent luminescence,h as received considerable attention owing to its fundamental scientific importance and potential technological applications,r anging from display and emergency signage to document security and bioimaging, [18][19][20] which has been limited to inorganic materials.Intrinsic obstacles to the use of inorganic phosphors,such as harsh preparation conditions,s carcity of metal resource components,and high toxicity for bioapplications,have led to many alternate and effective approaches,s uch as host-guest doping, crystallization, and H-aggregation. [21][22][23][24] These approaches were recently investigated to generate ultralong phosphorescence in metal-free organics at room temperature. Such ultralong phosphorescence shows steady-state optical behavior.…”

Prolonging Ultralong Organic Phosphorescence Lifetime to 2.5 s through Confining Rotation in Molecular Rotor

“…Ultralong organic phosphorescence (UOP) in metal‐free organic functional materials has drawn an extensive attention due to its extremely long emission lifetime, giving birth to various potential applications, such as organic light emitting diodes (OLEDs), bioimaging, data encryption, thermal/optical recording, and molecular sensing . To obtain ultralong emission lifetime in organic functional materials, both the radiative and nonradiative decay rate of triplet excitons should be reduced .…”

Amorphous Pure Organic Polymers for Heavy‐Atom‐Free Efficient Room‐Temperature Phosphorescence Emission

“…Thus,i ti se ssential to develop pure organic amorphous RTPmaterials. Thecommon method to obtain such materials is to embed the phosphors into rigid polymer matrixes, [20,21] steroidal compound, [22,23] the cavity of macrocycle hosts, [24][25][26][27] and so forth. In addition, our group designed as eries of phosphors to copolymerize with acrylamide that could engender effective phosphorescence emission of different colors under ambient conditions, [27][28][29] in which the hydrogenbonding network restricted the molecular motions and the halogen atom (e.g.…”