Conjugated Polymers Based On Poly(fluorenylene Ethynylene)s:Syntheses And Sensing Performance For Nitroaromatics

With the progress and development of society,more and more attention was paid in to terrorist attacks,environmental issues.Some methods and materials have been used to detect explosives.However some new methods can quickly detected the trace nitroaromatics is still very important.In the current detection methods,fluorescence sensors have been proved a high selectivity and sensitivity methods.Therefore,fluorescence sensors were selected as the method for detecting nitro-aromatics in this article.2,4,6-trinitrotoluene(TNT),2,4-dinitrotoluene(DNT),picric acid(PA)and other nitroaromatic(NACs)are common components in explosives.These nitroaromatic compounds are electron-deficient substance however fluorescent conjugated polymers have properties of electron-rich,when NACs contact with conjugated polymer sensor,electron transfer from conjugated polymers to nitroaromatic and caused fluorescence quenching.At the same time due to the conjugated polymer with the "molecular wire effect" and therefore the sensitivity in detecting nitroaromatics is improved.Although the fluorescence detection method has a number of advantages but there still some disadvantage to affect the performance of fluorescence detection method in detecting nitroaromatics.π-π stacking can be occured between conjugated main chain,which seriously affect the solubility of the polymer and limiting its application range.π-πstacking also caused self-quenching between the polymers and reduced the sensing performance.According to the above disadvantages of conjugated polymers we designed and synthesized a series of fluorescent conjugated polymer to overcome its shortcomings.The synthesized polymers made in to spin-coated thin film sensors to detect the nitro-aromatics.Spin-coated film also have some disadvantages.such as instability,serious photobleching and poor permeability.To improve the detection performance of the nitro-aromatics electrospun nanofibers was made to detect the NACs.In order to get a more sensitive sensor,electrospun nanofibrous membrane sensor with double-layer structure,named as P-PS/GEL,were prepared.Firstly,a layer of gelatin electrospun nanofibrous membrane(named as GEL)was prepared onto the glass surface as the porous skeleton.Secondly,an electrospun nanofibrous membrane P-PS,which was prepared from the mixture of polymer P doped in PS/(THF:DMF)solution,was covered on the layer of GEL.The GEL layers possess several functions:i)Gelatin molecule contains a large number of electron-rich groups of amino and hydroxyl,which effectively absorb,NACs in the sensor surface by the hydrogen bonding interaction between NACs and gelatin.This NACs-rich effect benefits the detection of trace amounts of NACs.ii)The gelatin nanofibrous membrane is porous and locates at the bottom of the P-PS.It allows the NACs vapor permeate from both the upside and downside of the double-layer membrane,the way by which can improve the quenching efficiency and responding speed of the sensor to NACs.iii)Gelatin own a stronger polarity than PS,forming a stronger binding with the glass surface,make the double-layer structure of P-PS/Gel have a better mechanical stability.In the last of article,the anti-photobleaching performance of electrospinning gelatin membrane sensor(P-GEL)was discussed.The fluorescence intensity of the sensor(P-GEL)has not observed significant decline in 5000 s.Conversely,the fluorescence intensity have a slight enhancement in the middle of the time.the sensor of the P-GEL Exhibits very good resistance to photobleaching performance,which is very meaningful in practical applications in the future.