A fluorescent nonconjugated zwitterionic polymer dot: hydrothermal synthesis and application in the nano-molar sensing of 2,4,6-trinitrophenol

Developing nonconjugated polymer dot-based sensors with high quantum yield for a targeted application is a challenging research field. Herein, we report the synthesis of a zwitterionic polymer dot (PD PAMAM 2.5, average diameter 12 nm), which contains a poly(aminoamide) core and amine and acid groups on the surface. The molecular structure and functionalities of the polymer dot were carefully established using various spectroscopic techniques, including NMR, FTIR, and XPS. The polymer dot revealed greenish blue/aqua emission (λ_max = 470 nm) with a quantum yield of 28%. The mechanism for the synthesis of polymer dot with respect to its structure and fluorescence property was examined using a combination of techniques, including NMR, zeta potential and fluorescence spectrometry. The application of the fluorescent polymer dot for the selective detection of 2,4,6-trinitrophenol was studied in detail. The limit of detection was determined to be 0.77 nM, which was the best value among the current state-of-the-art. Furthermore, application of the polymer dot in real life scenarios was demonstrated using real life wastewater samples and a paper-based strip-test method.