Fluorescent and colorimetric sensor for Cu2+ ion based on formaldehyde modified hyperbranched polyethylenimine capped gold nanoparticles

In this paper, we propose a fluorescent and colorimetric sensor for Cu2+ ion based on formaldehyde modified hyperbranched polyethylenimine capped gold nanoparticles (F-hPEI Au NPs). The fluorescent sensor is prepared by one-pot synthesis, of which the fluorescence intensity could be quenched by Cu2+ ion. The response behavior of the sensor is dependent on the pH value of the solution. At pH 4.0, the sensor exhibits a linear response for Cu2+ ion over a wide concentration range of 0.15 μM-23 μM. The detection limit for the sensor is estimated to be 77 nM (S/N = 3), and the precision for five replication detections of 2.0 μM Cu2+ ion is 4.7% (relative standard deviation). Both the color and fluorescence intensity of the sensor change obviously and could be observed with the naked eyes when there is continuous addition of Cu2+ ion. The fluorescence intensity of quenched sensor could be recovered by EDTA, which provides a potential method to regenerate the sensor. Furthermore, the sensor shows satisfying reliability and accuracy in practical Cu2+ ion detection applications.