Reversible Ultralong Organic Phosphorescence for Visual and Selective Chloroform Detection

Abstract

Volatile organic compounds (VOCs) are widespread in our daily life and greatly harmful to human health, as well as to the environment. To date, it remains a formidable challenge to develop a highly sensitive visual system for selective detection of VOCs. Herein, we report on a metal-free organic molecule of 2,4-di(10 H-phenothiazin-10-yl)-1,3,5-triazine (TDP) with ultralong organic phosphorescence (UOP) feature as a visible chemical probe for chloroform detection. In the pristine solid state, this phosphor shows a green UOP with a lifetime of 56 ms after the removal of excitation light source; however, the UOP greatly diminishes when fumed with chloroform, which is ascribed to the variation in both radiative and nonradiative transitions in crystal with embedded chloroform. Remarkably, TDP materials demonstrate great potential as a visual chemical probe for chloroform, showing high sensitivity, excellent selectivity, and good repeatability. The limitation for chloroform detection is as low as 5 ppm. Combining experimental data and theoretical calculations, it is reasoned that the space confinement via intermolecular interactions between chloroform and TDP molecules play a vital role for high selectivity of chloroform detection. These results pave the way toward expanding the scope of organic luminogens with UOP as well as their applications.

Organic Room Temperature Phosphorescence Materials for Biomedical Applications

“…Organic phosphorescence, an electronic transition from the excited triplet state to the singlet ground state, has attracted increasing attention recently, owing to its long-lived triplet excitons and large Stokes shifts. [1] During past years, various phosphorecent materials have been widely applied in newly emerged technologies, such as data encryption and display, [2][3][4][5] molecule sensing and imaging, [6][7][8][9] organic light emitting diodes [10][11][12][13] and so forth. [14][15] Early researches on phosphorescent materials mainly focused on the metal-containing compounds, for example, europium, iridium and platinum-containing complexes.…”

Room‐Temperature Phosphorescence in Metal‐Free Organic Materials

“…This phenomenon is often observed in inorganic materials and organometallic complex material . Beyond this limit, recently, room‐temperature phosphorescence (RTP) from pure organic materials has attracted great attention owing to its various functional applications in the fields of optoelectronic and bioelectronics, such as organic light‐emitting diodes, digital security, optical recording devices, sensors, bioimaging, and so on.…”

Polymorphic Pure Organic Luminogens with Through‐Space Conjugation and Persistent Room‐Temperature Phosphorescence

“…To address these issues, it is of crucial importance to develop diverse p ‐RTP luminogens and to summarize their general underlying principles. So far, researchers have tried to promote the spin‐orbit coupling (SOC) and subsequent intersystem crossing (ISC) through incorporation of carbonyl groups (C=O), halogens, and heteroatoms . At the same time, several other approaches, including radical‐ion pairs, σ–n conjugation, crystallization, embedding in a rigid matrix, H aggregation, metal–organic frameworks or organic–inorganic perovskites, have been proposed to stabilize the triplet excitons as a means to achieve efficient p ‐RTP luminogens.…”

“…In particular, those with persistent RTP (p-RTP) are also promising owing to the retaining of RTP emissione ven after ceasing the excitation sources, which means they can be used in encryption, oxygen and chemical sensing, and high-resolution molecular imaging with ideal signal-to-noise ratios. [17,[20][21][22][23][24][25][26][27][28][29][30][31] Meanwhile, whenc ompared to their inorganic or organometallic counterparts, pure organic RTP luminogens benefit from their good biocompatibility,a ppreciable processability,w ide variety,a nd so on. [17,[20][21][22]31] Despite dramatic advances having been achieved in the development of such p-RTP luminogens, [17,[20][21][22] solutions to some fundamental issues, such as au niversal molecular design strategy and the effective modulation of the photophysicalp rocesses and the emission mechanism, remaini n their infancy.T oa ddress these issues, it is of crucial importance to develop diverse p-RTP luminogens and to summarize their general underlying principles.…”

“…So far,r esearchers have tried to promote the spin-orbit coupling (SOC) and subsequent intersystem crossing( ISC) through incorporation of carbonyl groups (C=O), halogens, and heteroatoms. [17,[20][21][22]31] At the same time, several other approaches, including radical-ion pairs, [32] s-n conjugation, [33] crystallization, [24,[34][35][36][37] embeddingi n ar igid matrix, [9,[38][39][40] Ha ggregation, [8,31,41] metal-organic frameworks or organic-inorganic perovskites, [42][43][44] have been proposed to stabilize the triplet excitons as am eans to achieve efficient p-RTP luminogens.…”