Dual-Channel Luminescent Signal Readout Strategy for Classifying Aprotic/Protic Polar Organic Medium and Naked-Eye Monitoring of Water in Organic Solvents

Abstract

Developing a convenient and rapid detection method for water is greatly desirable in the field of chemical industry. Herein, we present a simple and effective strategy combining a fluorescence sensor and a one-to-two fluorescence colorimetric logic operation to monitor water in a wide range of organic media and classify aprotic/protic polar solvents. The dual-emitting luminescent detector was prepared by incorporating a fluorescent dye Rhodamine 6G (R6G) with strong green light emission within a red light-emitting Eu-metal–organic framework (MOF) through the “bottle around ship” method. R6G@Eu-MOF displays completely different fluorescence response behaviors to various organic solvents. Thus, when one made use of the intensity ratio of different fluorescence emission centers, a 3D decoded map was proposed to reliably and effectively distinguish different aprotic/protic polar solvents. Moreover, R6G@Eu-MOF exhibited two different ratiometric sensing modes when detecting water in aprotic/protic polar solvents due to the hydrogen bonding interaction, that is ratiometry with one reference signal or two reversible signal changes. Furthermore, using water content as the input signal and two kinds of fluorescence emission as the output signals, a one-to-two logic gate system was constructed, making it possible to develop an intelligence system for water detection. Overall, we demonstrated for the first time that R6G@Eu-MOF could serve as an efficient platform for tracing water in organic media and distinguishing protic/aprotic polar organic solvents.

Engineering of Metal–Organic Frameworks as Ratiometric Sensors

“…165−167 Lu and co-workers reported the Eu-based fluorescence MOF sensor to monitor water in organic media and categorize aprotic/protic polar solvent. 168 The dual-emitting MOF sensor, R6G@Eu-MOF, was synthesized by incorporating strong green light emission Rhodamine 6G (R6G) dye into the Eu-MOF having red-light-emitting feature (Figure 54).…”

“…Schematic presentation for the synthesis of the R6G@Eu-MOF for the recognition of water in organic medium. Reproduced with permission from ref . American Chemical society, Copyright 2020.…”

Dual-Emission Carbon Dots for Ratiometric Fluorescent Water Sensing, Relative Humidity Sensing, and Anticounterfeiting Applications

“…8,9 For example, Li et al developed ratiometric R6G@Eu-MOF water sensors with distinguishable fluorescence color change. 10 Qian et al designed a high-sensitivity water sensor-based dual-emission covalent organic framework that can exhibit emissive colors visible to naked eyes. 11 Li et al prepared ratiometric fluorescence nanosensor Tb 97.11 Eu 2.89 -L1 and revealed its great potential for visual water sensing.…”

“…Recently, numerous sensing methods with outstanding advantages, such as chromatography, electrochemical, nuclear magnetic resonance, and spectroscopic, etc., have been developed for water detection. , Among them, fluorescence methods are broadly considered due to high sensitivity, good selectivity, convenient operation, and fast response. , Different from single-emission fluorescence detection, the ratiometric fluorescent sensor takes dual-wavelength fluorescence intensity as the evaluation index. It has a self-correction function, which greatly reduces the interference of the external environment, has high detection sensitivity, and provides easy-to-discriminate fluorescence color and intensity changes. , For example, Li et al developed ratiometric R6G@Eu-MOF water sensors with distinguishable fluorescence color change . Qian et al designed a high-sensitivity water sensor-based dual-emission covalent organic framework that can exhibit emissive colors visible to naked eyes .…”

Encapsulation of Luminescent Guests to Construct Luminescent Metal–Organic Frameworks for Chemical Sensing

“…In addition, a ratiometric fluorescence sensor can also be constructed according to the opposite fluorescence change. Li et al 104 incorporated the green dye R6G into the Eu-MOF framework with red light emission, and the synthesized R6G@ Eu-MOF has double-emission centers. The ratiometric fluorescence detection of water in aprotic and protic polar solution was discussed, respectively.…”