Conducting Nanofibrous Membranes

Most of the polymers used in electrospinning are nonconductive. In the next section, different procedures to prepare conductive nanofibrous membranes will be described and applied to the development of fiat and flexible electrode sheet thereby expanding the potential geometries used in electrochemistry. 

Alternatively, it is also possible to develop conductive nanofibrous membranes from any kind of nonconductive polymers. At this purpose, conducting fibers made by polyamide 

SEM image of nanofibers after the immobilization procedure with carbon nan- 

A unique feature of this sensor is that at the end of each analysis, the MWNT membrane can be easily peeled-off, leaving the electrode surface back to its original electrochemical behavior. No trace of fouling was recorded on the electrode. 

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Kai D., Prabhakaran M. R, Jin G., and Ramakrlshna S., Polypyrrole-contained electrospun conductive nanofibrous membranes for cardiac tissue engineering,/ Biomed. Mater. Res. A, 2011,99,3. 

A straightforward method to prepare conductive nanofibrous membrane (NFM) is from the electrospinning of conducting polymers (Figure 13.8), such as polypyrrole, polyaniline, polyethylene oxide, and polythiophene [64, 65]. Electrically conducting polymers are known to possess numerous features, which allow them to act as excellent materials for the development of sensing devices as well as for the immobilization of biomolecules in the design of biosensors [66]. 

To focus on the topic, in the next sections, the general term nanoelectrochemistry will be whittled down to the study of conductive surfaces coated with material having one or more external dimensions in the nanoscale and the apphcations will be limited to electrochemical sensors and biosensors modified with nonwoven nanofibrous membranes prepared by electrospinning. 

Furthermore, nanofibrous membranes can be used to develop flexible and conductive nanofibrous electrodes, either with their modification with conducting polymers, or with the inclusion of activated multiwalled carbon nanotubes. The resulting membranes, made conductive by the incorporation of carbon nanotubes or conductive polymers, can be modeled in different forms, as desired, such as cylinders, balloons, spirals, and so on. 

Fig. 12.10 (a) Optical image of flexible silica fibrous membranes when bent with PET film, (b) Thermogravimetric analysis of silica nanofibrous membranes (red line) and PVA/silica hybrid membranes (blue line) was conducted from 100 °C to 900 °C in air. (c) Filtration efficiency and pressure drop and (d) QF values of various silica nanofiber membranes at the face velocity of 5.3 cm s . (e) Filtration efficiency and pressure drop and (f) QF value variation versus basis weight of SNF3 membranes under the face velocity of 5.3 and 14.1 cm s ((a) Reprinted with permission from [76]. 2010 American Chemical Society, (b Reprinted with permission from [79]. 2012 The Royal Society of Chemistry)... 

Up until now, electrospun nanofibrous membranes have been studied as chemical sensors, gas sensors, biosensors and optical sensors [91-94], Ding et al. [95] used quartz crystal microbalances (QCM) sensors coated with poly (acrylic acid)/poly (vinyl alcohol), PAA/PVA electrospun nanofibers and discovered an increase in the sensitivity of QCM sensors. Similar studies were conducted on M0O3, W03, NO2 and Ti02 nanofibers [96-99], These nanofibers exhibited an increase in sensitivity when compared to traditional sensors. In some instances, nanofibers are used as batteries [100-103], catalyst [104-110] and enzyme [111-120] carriers, due to their intercormected porous nature, large surface area, and high permeability to reactants. 

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