Synthesis, Properties Of Fluorescent Polymers And Their Sensing Of Metal Ions And Small Organic Molecules

Environmental pollution and safety issues have been the centre of attention,especially the pollution of metal ions and the harm of nitro aromatic explosives,has aroused the focus of the researchers.Fluorescent polymers are widely used in metal ions and organic small molecules detection because of its high sensitivity,good selectivity,easy operation and real-time on-line.In this paper,a series of fluorescent polymers were prepared by the amine-aldehyde condensation using a simple and easy method of heating reflux,which mainly solved the problems of polymer synthesis process cumbersome,monomer rare and fluorescent color adjustment difficult.Then,the series of polymers were used in metal ions and nitro aromatic explosives detection.The main research contents are as follows:In the second chapter,the blue-light emission polymer solution was obtained with melamine and glyoxal as simple raw materials by amine-aldehyde condensation by heating reflux,then the solution was deposited with acetone solvent to give a solid blue light material.We analyzed the structure and properties of the product by FT-IR,13C-NMR,PXRD,TG-DTA,fluorescence spectroscopy,UV-vis absorption spectra and fluorescence lifetime.The fluorescence of solid product dispersed in aqueous solution and the response of various metal ions to the fluorescence of the solution showed that the blue-light polymer had good selectivity,high sensitivity and anti-interference when detecting Cu2+ in aqueous solution.The fluorescence quenching degree showed an increasing trend with the increase of Cu2+ concentration from 5 nM to 750 ?M.When the Cu2+ concentration is in the range of 0-100 nM,the Stern-Volmer curve between the relative fluorescence intensity F0/F and Cu2+ concentration exhibits a good linear relationship,and the linear correlation coefficient is 0.99226,the detection limit is 16.2 n M.According to Environmental Protection Agency(EPA)data,the standard for Cu2+ in drinking water is about 20 ?M and the target in sewage discharge is about 7.8 ?M,both of which are within the detectable range.Since Cu2+ easily forms a complex with the abundant N,O elements in the polymer,which may cause the quenching of the fluorescence to achieve the purpose of detection.The above results show that the melamine-glyoxal blue-light emitting material has potential application in the field of copper ion fluorescence sensing.In the third chapter,A series of novel bis-Schiff base conjugated polymers were prepared by the amine-aldehyde condensation reaction using heating reflux method with low cost,bifunctional terephthalaldehyde and ammonium hydroxide as simple raw materials,methanol,DMF and DMSO as solvent,respectively.And their fluorescent colors have changed from blue-green to green to yellow-green.The structures of the polymers were analyzed by 13C-NMR,PXRD and FT-IR.The morphological characteristics were analyzed by FE-SEM.The thermal stability of the conjugated polymers was investigated by TG-DTA.It was found that the synthesized polymer with methanol as solvent had good thermal stability and uniform particle morphology through the comparison of the fluorescence intensity and wavelengths stability of the conjugated poly-Schiff base suspension,and the analysis of morphology and thermal stability,Which is the reason why conjugated polymer P-meth is selected to detect organic small molecule explosives nitrobenzene.In this paper,the fluorescence of the suspension was almost completely quenched by nitrobenzene when exploring the response of various organic small molecules to the fluorescence of the suspension.Through the selective,competitive and sensitive experiments,it was found that the concentration of conjugated polymer P-meth detecting nitrobenzene was as low as 10 ppm.When the nitrobenzene concentration is in the range of 10-250 ppm,the curve of fluorescence quenching efficiency and nitrobenzene concentration showed a good linear relationship,and the linear correlation coefficient is 0.9953.The detection mechanism is considered to be attributed to the electrons transfer from electron-rich conjugated poly-Schiff base to electron-withdrawing nitrobenzene through the electrostatic interactions,which results in fluorescence quenching.However,up till now,application of fluorescent Schiff base is limited in metal ions detection,while small molecules or explosives are still rarely reported.Therefore,it is of great significance to apply fluorescent conjugated poly-Schiff base to nitrobenzene(NB)detection in this chapter.