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Glutathione（GSH）plays a critical role in maintaining oxidation-reduction homeostasis in biological systems.Considering the detection of GSH by fluorescence sensors is limited by either the short wavelength emission or the poor photostability,a highly stable colorimetric and ratiometric NIR fluorescent sensor（DCM-S）for GSH detection has been constructed on the basis of dicyanomethylene-4H-pyran（DCM）chromophore.The specific disulfide bond is incorporated via a carbamate linker as the GSH responsive group,which simultaneously blue-shifts and quenches the fluorescence.Upon addition of GSH,DCM-S exhibits outstanding colorimetric（from yellow to red）and ratiometric fluorescent response with the 6-fold enhancement of NIR fluorescence at 665 nm in quantum yield.More importantly,the GSH-treated DCM-S（DCM-NH2 actually）possesses 20-fold longer fluorescence half-life period as well as much better photostability than the FDA-approved ICG.Finally,the ratiometric detection of GSH is also successfully operated in the living cell imaging,exhibiting NIR fluorescence and large Stokes shift（215 nm）with nearly no background fluorescence interference.As a consequence,DCM-S can be utilized as colorimetric and ratiometric NIR fluorescent sensor for GSH,with a great potential in the development of GSH-induced drug delivery system.

The present work reports a sensitive and selective fluorescent sensor for the detection of mercury ion, Hg（II）, by hybridizing carbon nanodots （C-dots） and gold nanoclusters （Au NCs） through intrinsic interactions of the two components. The C-dots serve as the reference signal and the Au NCs as the reporter. This method employs the specific high affinity metallophilic Hg2~-Au＋ interactions which can greatly quench the red fluorescence of Au NCs, while the blue fluorescence of C-dots is stable against Hg（II）, leading to distinct ratiometric fluorescence changes when exposed to Hg（II）. A limit of detection of 28 nM for Hg（II） in aqueous solution was estimated. Thus we applied the sensor for the detection of Hg（II） in real water samples including tap water, lake water and mineral water samples with good results. We further demonstrated that a visual chemical sensor could be manufactured by immobilizing the nanohybrid probe on a cellulose acetate circular filter paper. The paper-based sensor immediately showed a distinct fluorescence color evolution from pink to blue after exposure to a drop of the Hg（II） solution

A non-sulfur chemosensor based on an easy to prepare double naphthalene Schiff base is reported for the colorimetric and flu- orometric dual-channel sensing of Hg2＋ ions by taking advantage of the twisted intramolecular charge transfer （TICT） mecha- nism. This work provides a novel approach for the selective recognition of mercury ions. Moreover, this sensor serves as a po- tential recyclable component in sensing materials and the complex L-Hg2＋ （L = 1-[（2-naphthalenylimino）methyl]-2-naphtha- lenol） can therefore be used as a fluorescent sensor for iodine anions. Notably, the color changes are very significant and all the recognition and recycling processes can be observed by the naked eye.

The development of sensors for selective detection of cyanide ion（CN~-） is an important mission to accomplish because of the versatility and toxicity of CN~-. In the present work, an ＂ensemble＂-based colorimetric and fluorescent sensor（L2-Zn~（2＋）） for CN~-ion has been developed. The addition of cyanide ions removed Zn~（2＋） from the ensemble（L2-Zn~（2＋）） in aqueous medium, resulting in a color change of the solution from red to buff and a ＂turn-on＂ fluorescent response. Also, the sensitivity of both the fluorescenceand colorimetric-based assay is below the maximum allowable level of cyanide ions in drinking water set by the World Health Organization. In addition, test strips, which served as convenient and efficient CN~- test kits, were fabricated based on the sensor.Notably, the selective detection of cyanide with L2-Zn~（2＋） for practical application was also performed in sprouting potatoes.

The BINOL-amino alcohol enantiomeric pair （S）-I and （R）-I are discovered to conduct both enantioselective and diastereose- lective fluorescent discrimination of the four stereoisomers of threonine derivatives. This study utilizes different fluorescence responses of one sensor at two emission wavelengths toward the stereoisomeric substrates which expands the capability of the sensor in chiral recognition. In addition, the sensor pair also allows visual recognition of the N-protected L-allo-threonine and D-allo-threonine by enantioselective precipitation.