A colorimetric and fluorescent dual-channel cyanide ion probe using crosslinked polymer microspheres functionalized with protonated Brooker's merocyanine

•Protonated Brooker's Merocyanine functionalised polymer microspheres was designed.•The microspheres display colorimetric and fluorescent sensing properties toward CN–.•The microspheres can be reversed for many times for monitoring and detection of CN–.•The microspheres are applicable for determination of CN– in real samples.

This paper describes the development of a colorimetric and fluorescent cyanide probe based on crosslinked polymer microspheres functionalized with a protonated merocyanine. The functionalised microspheres were prepared by free radical polymerization using 4-((E)-2-[(4-hydroxylphenyl) ethenyl-1-allyl pyridinium bromide as the functional monomer, ethylene glycol dimethacrylate as the crosslinker, and azobisisobutylnitrile as the radical initiator. Upon introducing CN– to a suspension of the functionalised microspheres in ethanol/H2O (9:1, v/v), a change from yellow to red and a decrease in fluorescence intensity at 497 nm were immediately observed. This CN– probe can be reversed many times, which is cost efficient and beneficial to the environment. Analytical application of the functionlised microspheres to measure CN– concentration in spiked water samples was explored with good recoveries. Thus, the colorimetric and fluorescent CN− probe has high potential for the ultrasensitive detection of CN− in real samples.

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