High Efficiency Carbazole-based Polymer Sensors For The Detection Of TNT And DNT

In recent years,terrorist activities have occurred from time to time,explosives endanger social stability and national security,which brings great harm to the people.Nitro-aromatic compounds are important compounds in the manufacture of high explosives,in addition to their high explosive,it also led to many health problems,for example,excessive inhalation of TNT vapor can cause abnormal liver function,may also cause severe neurological damage,at the same time,they are a typical organic pollutants,can cause some pollution to the environment.Therefore,how to quickly and accurately detect nitro-aromatic explosives,especially in the gas environment,has attracted a wide range of research and attention at home and abroad.The detection of nitroaromatic explosives by a wide variety of chemical sensors has been widely studied and applied.Among them,the fluorescent sensor has been widely used in the detection of nitro-aromatic explosives,because of its high sensitivity,high selectivity,high stability and easy to use.The detection mechanism is that the photo-induced electron transfer between the fluorescent molecules and the explosive molecules,which leads to the fluorescence quenching.Among them,the study of fluorescent conjugated polymers as sensors has attracted much attention,but compared to the hyperbranched polymers,dendrimers and microporous polymers,the dense conjugated polymer films often prevent the efficient diffusion of explosives molecules in the polymer,which will greatly limit their application.In this paper,we adopts the detection method of fluorescence signal sensing,and prepared the fluorescence sensor with carbazole as the sensing group,the polymer was PCzSiO and PCzSiPh with polysiloxane as the main chain and polysilylbenzene as the main chain.Two kinds of polymers are containing the non-conjugation of silicon,which prevents the self-quenching phenomenon and impart good solubility and film-forming property of the polymer.In the second chapter,two kinds of carbazole-based polymers PCzSiO and PCzSiPh were used to detect explosives TNT and DNT.The effects of polymer molecular structure and the film thickness on the fluorescence sensing were investigated.It was found that PCzSiPh has a loose molecular chain structure,showing better sensing properties.The quenching efficiencies in TNT and DNT saturated vapors were 91.0 ± 0.3%and 94.4 ± 0.3%,respectively.In addition,the fluorescence quenching of PCzSiPh towards TNT and DNT is little dependent on the film thickness.At the same time,PCzSiPh films have good reversibility,strong film forming ability and excellent thermal stability and morphology stability,which indicates that they have potential application in the sensing of detection devices.In the third chapter,the polymer PCzSiPh and the small molecule SimCP2 were used as electrochemical polymerization precursors to prepare the electrochemical thin films as the sensing films for the detection of TNT by electrochemical crosslinking.It is found that the electrochemical polymerization of PCzSiPh has a good response to TNT,and the fluorescence quenching efficiency in TNT saturated vapors 600 s can reach 80.68%.This indicates that the PCzSiPh electrochemical polymer film prepared by cyclic voltammetry is a thin film with good sensing for TNT vapor.The electrochemical polymerization of SimCP2 exposed to TNT saturated vapors for 600 s,the fluorescence quenching efficiency can reach 63.51%.The experimental results show that the response speed and sensitivity of PCzSiPh electrochemical polymer films to TNT vapor are better than SimCP2 electrochemical polymer films.