Amphiphilic Conjugated Polyelectrolyte-Based Sensing System for Visually Observable Detection of Neomycin with High Sensitivity

Abstract

To detect neomycin, one of the common antibiotics in the environment and in food and which may pose harm to human health, a fluorescence sensing system based on an amphiphilic conjugated polyelectrolyte (CPE) was constructed. The CPE, PFPE-COONa, with poly[fluorenyl-alt-p-phenyleneethynylene] (PFPE) as the backbone and carrying four pendant hydrophilic carboxylate groups and two long hydrophobic alkoxyl chains in each repeat unit, was successfully synthesized. The photophysical study found that PFPE-COONa emission was solvent dependent, displaying a 58 nm red shift in wavelength and a nearly 150-fold enhancement in intensity for the emission maximum, by varying the ratios of the mixed solvent. Based on an understanding of the photophysics, the sensing condition was optimization to dissolve PFPE-COONa in the THF/H2O mixed solvent with a ratio of 1:1. The sensing system displayed excellent sensing performance toward neomycin at a neutral pH value. The blue-to-green fluorescence color change of the polymer solution, which can be clearly observed by the naked eye, upon around 0.7 μM of neomycin and the limit of detection (LOD) was calculated to be 0.78 nM. In addition, other possible interferents had no significant influence on the detection of neomycin. The mechanism study confirmed that the polymer aggregation, which induced strong electrostatic static interaction between the carboxylate groups of high density in the polymer and the dense positively charged primary amino groups in neomycin, was the main reason for such a visually fluorescent color change. This study provides a general strategy for the future design of sensing systems for organic pollutants.