Synthesis, characterization, fluorescent emission of sodium poly(ethylene glycol) and its uses in sensing, cell imaging and data encryptions

In contrast to conventional fluorescent polymers featuring large conjugated structures or classical chromophores, a class of fluorescent polymers, free of all conjugations and chromophores, has been gaining significance in immerging applications that conventional fluorescent materials cannot achieve. Poly(ethylene glycol) (PEG) is a popular biopolymer widely used in biomedical fields and reportedly fluorescent emissive under limited conditions. By simply reacting with concentrated NaOH, Na alkoxidation of low molecular weight PEG is achieved (Mn 200 to 600), and the highest alkoxidation is achieved with PEG of Mn 400. The formation of the sodium PEG (NaPEG) is confirmed through multiple perspectives: a distinct color change from colorless to dark brown for the reaction mixture, reaction materials balance, NMR and FTIR analyses, fluorescent emission and the detection of its cluster sizes, all in comparison with the starting material PEG. Comparing to PEG, the fluorescence emission of NaPEG is largely enhanced by more than 20 times, thanks to its enhanced clustering capacity based on clustertriggered emission principle, confirmed by different testing. NaPEG is used for detections of Cr6+, Fe3+, H2O2 and antibiotic doxycycline (DOX), out-performing most of reported sensors. Practically nontoxic, NaPEG is also used for data encryption of different versions, HeLa cell imaging and monitoring of Fe3+ and DOX under physiological conditions. This work provides therefore a simple protocol for synthesis of a novel green polymer sensor of great potential for multipurpose applications, in particular as sensors in biomedical areas.