Yan Zhang,Xiaofeng Yang,Guoxin Sun,Hao Zhang,Xiaolei Liu,Fengqiao Zhu,Shuchun Qin,Ziqi Zhao,Yu Cui
A series of colorimetric and reversible receptors for fluoride anions based on diketopyrrolopyrrole (DPP) were designed and synthesized successfully. The position of nitro substituent on the phenylhydrazide affected the alteration of photophysical properties to varying degrees. While the photoluminescence intensity of receptor 1 was weaker than that of receptor 2 and receptor 3 on account of the formation of intramolecular hydrogen bond deriving from oxygen atom of nitro substituent and hydrogen atom of hydrazide . The receptor 2 was a preferable chemosensor for responding fluoride anions. The fluorescence was quenched in the presence of fluoride anion resulted from the photo-induced electron transfer (PET) effect from the amide. The formation of deprotonation species, which produced by hydrazide N H moiety and F − was answerable for the spectral changes. Especially, the spectral and color responses of receptors could be switched back and forth successively by adding F − and HSO 4 − anions in DMSO solution. These receptors could response fluoride anion sensitively, visually and selectively in a manner of reversible with a low determination.
Two novel fluoride ion probes 11-(2-iminothiourea-2-phenyl)benzimidazole-isoquinolinone ( 3 ) and 10-(2-iminothiourea-2-phenyl)benzimidazole-isoquinolinone ( 3′ ) have been designed, synthesized and confirmed structurally by 1 H NMR、 13 C NMR and HRMS-ESI. Obvious color changes could be seen by naked-eye after the addition of F − to the DMSO solution of above probes. Both probes showed dual-channel properties: UV–vis absorption red-shift and fluorescence turn-off upon reacting with F − . More importantly, the F − induced visual and spectroscopic changes were fully reversible upon addingHSO 4 - .And the new probes could realize the distinguish recognition of F − and OH − by adding over 40 equivalents OH − . The detection limits of new probes were 0.6 nM. The recognition mechanism deduced from the 1 H NMR titration experiment and theoretical calculation was a combined process including hydrogen bonding and deprotonation between the probes and fluoride ion.
Xiaofei Qin,Can Chen,Shiyu Zhang,Jixin Zhu,Yongxiang Wang,Jinhua Liu
3,3′,5,5′-Tetramethylbenzidine (TMB) is one of the traditional enzyme substrates that has been widely used in the fields of artificial enzyme mimics and natural enzymes. However, the development of TMB-based probes for fluorescence and colorimetric dual models remains a great challenge. Herein, we developed a facile method to fabricate a colorimetric and fluorescent nanoswitch based on near-infrared fluorescent TMB dots (TMBDs) for the reversible recognition (CFRR) of Fe3+ and Cys. The proposed CFRR nanoswitch was based on an oxidation–reduction mechanism by which the TMBDs are oxidized by Fe3+ to form ensembles and Cys reduces the ensembles to TMBDs. The CFRR nanoswitch exhibited high sensitivity for the colorimetric and fluorescent recognition of Fe3+ with limits of detection (LODs) of 0.17 μM and 7.5 μM and of Cys with LODs of 0.1 μM and 1.5 μM, respectively. The response speed was very fast, within 5 min. Moreover, two output signals, namely near-infrared fluorescent and colorimetric, were exhibited in this CFRR sensor; the recognition was reversible and retained good stability after three cycles. It is noteworthy to mention that the CFRR nanoswitch performed successfully in urine, and molecular logic gate systems were readily established. Therefore, these investigations will shed light on the development of multi-mode output signals for nanoprobes.
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