Turn-On Fluorescence Chemical Sensing through Transformation of Self-Trapped Exciton States at Room Temperature

Abstract

Most of the current fluorescence sensing materials belong to the turn-off type, which make it hard to detect toxic substances such as benzene, toluene, and xylene (BTX) due to the lack of active chemical sites, thereby limiting their development and practical use. Herein, we show a guest–host mechanism stemming from the confined emitter’s self-trapped exciton (STE) states or electron–phonon coupling to achieve turn-on fluorescence. We designed a luminescent guest@metal–organic framework (LG@MOF) composite material, termed perylene@MIL-68(In), and established its E-type excimeric emission properties in the solid state. Upon exposure to BTX, especially xylene, we show that the E-excimer readily converts into the Y-excimer due to nanoconfinement of the MOF structure. Such a transformation elevates the fluorescence intensity, thus realizing a turn-on type fluorescent sensor for detecting BTX solvents. Our results further demonstrate that controlling the STE states of perylene at room temperature (vs the previous report of <50 K) is possible via nanoscale confinement, paving the way to enabling turn-on type luminescent sensors for engineering practical applications.

Tunable emission in the visible range from a single organic fluorophore through time-controlled morphological evolution

“…These results indicate that the extent of J-aggregation increases across the sequentially obtained four compounds (PyS-B → PyS-G → PyS-Y → PyS-R). 58–62 Furthermore, we performed concentration-dependent lifetime experiments for PyS-Y in an ethanol and toluene mixture (1 : 2), and observed that the excited state lifetime increased with increasing concentration (Fig. S22d, ESI†).…”

Strategic Design of Non-d10 Luminescent Metal–Organic Frameworks as Dual-Mode Ultrafast and Selective Sensing Platforms for Aldehydes at the ppb Level

“…34,35 Thus, there is a lack of luminescent sensing of such VOCs via the rare "turn-on" detection that eliminates the risk of faulty responses and avoids signal-to-noise ratio and is more applicable for onground detection. 6,36 Given the above background and significance, it is highly desirable to contribute to the underexplored Ni(II) MOFs as dual luminescent and electrochemical sensors. 37 (3), that are synthesized under environmentally-friendly, ambient conditions.…”

“…In view of this scenario, handleable sensory probes are in demand for easy, prompt, and selective sensing of such VOCs. Although the luminescent sensing of such VOCs at the ppb level is a handful, all are based on the quenching (turn-off) mechanism. , Thus, there is a lack of luminescent sensing of such VOCs via the rare “turn-on” detection that eliminates the risk of faulty responses and avoids signal-to-noise ratio and is more applicable for on-ground detection. , …”

DFT studies of proton transfer of 2, 4-dihydroxybenzoic acid derivatives

“…Organic small molecules have been studied extensively due to their many applications, such as in solar cells 7,[31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49] and other fields. 2,[50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67] These wide applications are due to their facile synthesis and versatile tuning ability to meet specific requirements. For instance, by covalently bonding three segments, we were able to construct an organic small molecule with cascade electronic energy levels in the format of D-A1-A2 31 or with delocalization for excitons 68 for solar cell applications.…”