Preparation And Fluorescence Properties Of Poly (Ethylene Glycol) Sodium

In the past 2 decades,fluorescent materials have been becoming more and more important in biomedical research and applications.Traditional fluorescent materials usually contain benzene ring and carbazole with largely conjugated structures,and are hardly soluble in water.Their applications are therefore largely limited.In recent years,there have been a lot of studies on a new type of fluorescent polymers,which are featured by the absence of typical chromophores,and contain only oxygen,nitrogen,sulfur or phosphore atoms.They are characterized in general by good biocompatibility,better water solubility.These non-typical fluorescent polymers have been widely used in bioengineering and drug detection.Poly（ethylene glycol）（PEG）is a typical example of these non-typical fluorescent polymers.It contains only oxygen atoms as the electron-rich heteroatom,and is known to be non-toxic,non-irritating with good water solubility.Used in cell imaging,biological markers,and other bioengineering,PEG is of considerable prospects.However,PEG only has strong fluorescence emission under specific conditions,including high molecular weight（Mn）,high concentration under narrow excitation.Generally speaking,fluorescence emission is very weak for PEG of low Mn below600.This brings one to think that,fluorescence emission may be intensified with some modification on PEG chain.If realized,its application field would be broadened.In this context,PEG is reacted with NaOH solution of high concentration（40mg/mL）in order to obtain its PEG sodium,denoted as PEGNa hereafter.The fluorescence emission of PEGNa is measured,the emission mechanism is discussed,and PEGNa is used as a probe for Fe³⁺detection.The details are as follows:PEGs of low Mn（200,400,600）were reacted with NaOH,to obtained PEGNa.Subsequently,the fluorescence properties of different PEGNa were tested,and compared with each other and with PEG itself.Experimental conditions of PEGNa preparation was optimized with regards to PEG concentration,NaOH amount,reaction temperature and pH etc.It was found that PEG of low Mn（200）enhanced the fluorescence intensity from PEG to PEGNa by 8 times,and PEG of low Mn（400）enhanced the fluorescence intensity from PEG to PEGNa by nearly 10 times.It shows that the fluorescence emission intensity of low molecular weight PEG is successfully enhanced by this method.The structure of PEGNa by Fourier Transform Infrared spectroscopy（FTIR）,nuclear magnetic resonance（¹H NMR）and fluorescence mechanism was studied.Na content of PEGNa was determined by inductively coupled plasma emission spectrometer（ICP）.The reaction for PEGNa formation was discussed.It was concluded that the mechanism of fluorescence of PEGNa is the same to that of PEG,which belongs to cluster trigged emission（CTE）due to oxygen aggregation,indicating that oxygen aggregation from PEG to PEGNa was significantly enhanced.PEGNa was used as probe for Fe³⁺detection.It was found that a significant quenching was observed by Fe³⁺in the presence of 10 different metal ions.Selective detection of H₂O₂was also done,only Fe³⁺can quenchthe fluorescence of PEGNa.The detection limit of Fe³⁺was 0.34μM by using PEGNa,which was significantly lower than the standard detection limit of Fe³⁺in drinking water set by US Environmental Protection Agency（EPA）（5.4μM）.Accordingly,PEGNa and Fe²⁺aqueous solutions were used as fluorescence probes to detect H₂O₂with a detection limit of 0.4μM.The application of PEGNa in information encryption and paper sensor has been explored,and the effect is remarkable.The effect of tetracycline drugs on PEGNa fluorescence performance was also explored.PEGNa was used to detect tetracycline drug doxycycline,and the detection limit of doxycycline was 0.4μM,and the quenching mechanism was studied.The results show that PEGNa really has application prospect in Fe³⁺,H₂O₂,tetracycline drug detection,information encryption and paper sensor.