Dual responses of near infrared fluorescence probe to viscosity and polarity
A fungal fluorescein-based near-infrared fluorescence probe FUNG was synthesized from Witting reaction between 3,4-dimethoxypyranone as electron-withdrawing group and semicarbocyanine dye as electron-donating group,and characterized by 1HNMR,13CNMR and HRMS.The response performance of the probe to viscosity and polarity of different solution systems was evaluated,while its anti-interference ability and pH applicability during the response process were also investigated.The results showed that the Stokes shift of FUNG in water was 178 nm,and the fluorescence emission wavelength(λem)was 700 nm.The probe could respond to the viscosity and polarity of different solution systems simultaneously,following a complex twisted intramolecular charge transfer(TICT)mechanism.In glycerol/water solutions with different glycerol volume fractions,the fluorescence intensity of the probe showed a linear relationship with solution viscosity,with its fluorescence intensity at 700 nm increased by about six times with the increase of the solution viscosity and its fluorescence lifetime increased accordingly.The response of the probe FUNG to the polarity of the solution was reflected by the red-shift of its fluorescence emission spectra,with its emission wavelength(λem)red-shifted from 606 nm to 698 nm with the increase of solvent polarity parameter.λem red-shifted from 669 nm to 712 nm with the decrease of the volume fraction of toluene from 100%to 10%in toluene/dimethyl sulfoxide(DMSO)solution,and from 631 nm to 717 nm when the volume fraction of 1,4-dioxane decreased from 100%to 10%in 1,4-dioxane/DMSO solution.The response of probe FUNG to the viscosity and polarity of solution displayed good selectivity,strong anti-interference ability,and a wide pH range.
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