A facile and label-free ratiometric optical sensor for selective detection of norepinephrine by combining second-order scattering and fluorescence signals
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In this work, a facile and label-free ratiometric sensor is constructed for selective determination of norepinephrine (NE) by coupling second-order scattering (SOS) and fluorescence, two different and independent optical signals. Herein, polyethyleneimine (PEI) dilute solution medium shows an intensive SOS signal without any fluorescence response. Interestingly, NE can be selectively induced by PEI to emit bright fluorescence, and meanwhile causes an observable decrease in the SOS signal due to the interactions between NE and PEI. The simultaneous variation of the two independent signals can be used for ratiometric sensing of NE. Under the optimal conditions, the resultant ratiometric sensor displays high sensitivity and selectivity toward NE by simultaneously monitoring fluorescence and SOS signals with the same excitation wavelength. The proposed sensor exhibits a good linear relationship versus NE concentration in the range of 10.0 nM–45.0 μM with a detection limit of 2.0 nM (S/N = 3) and has been successfully applied to the determination of NE in real samples without the use of any extra reagent. The combination of fluorescence and SOS signals provides a new scheme for ratiometric sensor design, greatly simplifying experimental procedure and effectively enhancing detection accuracy. Moreover, the proposed analytical strategy further broadens the application of dilute solutions of polymers in research into optical sensor and green analytical chemistry.
KeywordsRatiometric sensor Turn-on fluorescence Light scattering Norepinephrine Polyethyleneimine
This work was financially supported by the National Natural Science Foundation of China (No. 21675131), the Natural Science Foundation of Chongqing (No. CSTC-2015jcyjB50001), Sichuan University of Science & Engineering (2016RCL26), the Project of Zigong City (2016XC12), the Scientific Research Fund of Sichuan Provincial Education Department (16ZB0256), the Sichuan 1000 Talents Program (No. 978), and the Undergraduate Innovation Foundation of Sichuan Province (201810622052).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
The study was approved by the Ethics Committee of Southwest University, and written informed consent was obtained from all individuals participating in the study prior to the collection of the human urine samples.
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