Preparation Of Polymer Composite Fluorescent Nanofibers And Applications In Selectivity Of Explosives Detection

Nitro explosives of trinitrotoluene（TNT）,dinitrotoluene（DNT）,and nitrotoluene（NT）,etc.are common ingredients of industrial explosives.Tthe toxicity,carcinogenicity and mutagenicity of nitro explosives pose a serious threat to the environment and public health.Thus,the capability to reliably detect trace nitro explosive vapors is of great significance.In recent years,scientists have advocated green,non-polluting,repeatable,portable and low-cost sensors to detect explosive vapors,so sensing materials are generally made into solid films to detect traces of explosive vapors.Electrospinning is one of the most effective methods for the preparation of organic,organic/inorganic composite nanofibers because of its simple manufacturing equipment,low spinning costs,various types of spinnable materials,and process controllability.Due to its high porosity and large specific surface area,nanofibrous membranes play an important role in gas sensing,optoelectronic devices,and biomedical applications.In this paper,a series of composite nanofibers composed of small-molecule fluorescent probe 9-（pyren-1-yl）-9H-carbazol（PyCz）and different matrixs were fabricated by electrospinning,and their sensing properties on the detection of explosives vapor were studied in depth.1.PS/PyCz composite nanofibers were fabricated by electrospinning and doping blue-emission PyCz to polystyrene（PS）.Due to the favorable electron transfer driving forcet between the singlet excited state of the sensor molecules and extendedπ-πconjugated interactions between PyCz and phenyl pendants of PS,thus,the composite nanofiber can detect nitro explosives with high sensitivity.The fluorescence quenching efficiency of PS/PyCz composite nanofibers towards2,4-DNT vapor in air at 2 h were 89%.However,the nanofibers also have a fluorescence quenching response of 20%-30%for interferents such as naphthalene,urea,smoke,formaldehyde and ethanol.2.Hydrophobic PS/PyCz porous composite fibers were successfully prepared with the help of the pore-forming function of the polymer surface active material（Triton X-100）.The PS/PyCz porous composite fibers can recognize nitro explosives with high sensitivity.The fluorescence quenching efficiency of PS/PyCz composite nanofibers towards 2,4-DNT vapor was 77%at 2 h.Moreover,PS/PyCz porous composite fibers has almost no response to trace water vapor.PEO/PyCz composite nanofibers were further prepared using a hydrophilic polyethylene oxide（PEO）matrixs,which exhibit highly sensitive fluorescence quenching for nitro explosives and watery interferents.After PEO/PyCz nanofibers were exposed to water vapor,due to the hydrogen bonding between PEO and H₂O,the three-dimensional network structure of the nanofibers gradually collapsed into a quasi-liquid state,and the molecular rotational freedom of PyCz increased to cause energy loss.3.PNIPAM/PyCz composite nanofibers were prepared by electrospinning and amphiphilic poly（N-isopropylacrylamide）matrix,which exhibit highly sensitive fluorescence quenching for nitro explosives and watery interferents.The above results show that the hydrophobic sensing material based on the porous PS/PyCz composite nanofibers has special advantages in the detection of explosives in humid or multi-water areas;the hydrophilic composite nanofibers doped with PyCz have broad prospects in the field of humidity detection.