Sensors electrospun nanofibers

Composites of PANI-NFs, synthesized using a rapid mixing method, with amines have recently been presented as novel materials for phosgene detection [472]. Chemiresistor sensors with nanofibrous PANI films as a sensitive layer, prepared by chemical oxidative polymerization of aniline on Si substrates, which were surface-modified by amino-silane self-assembled monolayers, showed sensitivity to very low concentration (0.5 ppm) of ammonia gas [297]. Ultrafast sensor responses to ammonia gas of the dispersed PANI-CSA nanorods [303] and patterned PANI nanobowl monolayers containing Au nanoparticles [473] have recently been demonstrated. The gas response of the PANI-NTs to a series of chemical vapors such as ammonia, hydrazine, and triethylamine was studied [319,323]. The results indicated that the PANI-NTs show superior performance as chemical sensors. Electrospun isolated PANI-CSA nanofiber sensors of various aliphatic alcohol vapors have been proven to be comparable to or faster than those prepared from PANI-NF mats [474]. An electrochemical method for the detection of ultratrace amount of 2,4,6-trinitrotoluene with synthetic copolypeptide-doped PANI-NFs has recently been reported [475]. PANI-NFs, prepared through the in situ oxidative polymerization method, were used for the detection of aromatic organic compounds [476]. 

The electric response of isolated PANI fibers to vapors of aliphatic alcohols depends on the laige surfece-to-volume ratio, the uniformity of diameter, and the quantity of active material. The sensor constructions are comparable to or faster than those prepared from nanofiber mats of the same polymer. Also, the sensors made from individual fibers exhibit larger responses, especialty for bigger alcohol molecules, and also show true saturation upon exposure and removal of the alcohol vapor. The response of sensors made from electrospun nanofibers to small alcohol molecules is opposite to that observed for cast nanofiber mats, which can be related to the doping process used in the preparation of the polymer in either case. ... 

The sensing behaviors of PEDOT-PSS/PVP (Fig. 5.21) and PVP nanofibers on ethanol, methanol, THF, and acetone vapors are studied. The sensing was carried out for several q cles by repeated exposure of the nanofibers to saturated organic vapors and air alternately. Both PEDOT-PSS/PVP and PVP electrospun nanofiber sensors have exhibited good reversibility, reproducibility and response and recovery time. The response and recovery time of PEDOT-PSS/PVP nanofibers upon exposure to ethanol vapor are much faster than those of PVP nanofibers. 

In the PANI.TSA/PLA blended electrospun nanofibers no phase segregation of PANI in a PLA matrix was observed, while phase segregation was observed in cast films with the same composition. Due to rapid solvent evaporation in the electrospinning process, no crystalline structures in fiber mats were formed compared to cast films. Highly homogeneous electroactive fibers can be useful in the construction of electronic devices and sensors. Similar behavior was observed in the PVDF-TrFE/PANI-PSSA electrospun nanofibers. 

Electrospun nanofibers have been confirmed to be good candidates for ultrasensitive gas sensors due to the improved surface-area-to-volume ratios of coatings. " A higher surface area led to higher sensitivity and fast response time. 

Similarly, Aussawasathien et al. [185] compared the performance of CSA-doped polyaniline-polystyrene electrospun nanofibers with a thin film of the same composition for the electrochemical detection of hydrogen peroxide. As expected, the thin-film sensor showed significantly weaker currents than those of the electrospun nanofibers, with both materials showing a linear response of the redox current as a function of hydrogen peroxide concentration. However, the electrospun nanofiber sensor showed a much higher sensitivity, as evidenced by the greater slope. It was also shown that the detection of... 

Electrospun nanofibers are used in many applications such as filtration [61], catalyst support [62], biomedical [63] and sensors in electronics [64]. 

Electrospun nanofibers of several polymers, among others PVB were used in a surface acoustic wave resonator (30). The surface acoustic wave resonator is used as an ultrafast response humidity sensor. 

Ding B, Wang M, Yu J, Sun G (2009) Gas sensors based on electrospun nanofibers. Sensors 9 1609-1624 Dong B, Krutschke M, Zhang X, Chi LF, Fuchs H (2005a) Fabrication of polypyrrole wires between microelectrodes. Small 1 520-524... 

In comparison with other nanomaterials, electrospun nanofibers are featured with good continuity, extremely large length-to-diameter ratio, high surface-area-to-volume ratio, and ease of surface functionalization. Meanwhile, multiple extra functions can be incorporated into electrospun nanofibers fo broaden their significances in applications. Because of this, we have found in the open literature that more than 50 polymers have been successfully fabricated into sensors, involving polyamide-6 (PA-6), polyamide-6,6 (PA-6,6), polyacrylonitrile (PAN), polyurethane (PU), poly(acrylic acid) (PAA), Ti02, ZnO, cellulose acetate (CA), polyethylene oxide (PEO), polystyrene (PS), poly(vinylidene fluoride) (PVdF), etc. (Fig. 11.1). 

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