Conductivity measurement of electrospun PAN-based carbon nanofiber

Abstract

Although electrostatic generation, or electrospinning, of ultrafine fibers was invented as early as in 1930s [1], the technique has been used to produce conductive polymer fibers only recently [2]. Reneker and Chun et al. [3] electrospun polyaniline fibers from sulfuric acid into a coagulation bath. Chun et al. [4] electrospun polyacrylonitrile (PAN) nanofibers, and pyrolyzed them into carbon nanofibers. Because of their obvious high specific surface area, electrospun ultrafine fibers are expected to be used as high performance filters, or scaffolds in tissue engineering [5]. For the same reason, one may expect that chemisorbed gases may modulate the electrical conductivity, leading to the fabrication of sensor devices. Unfortunately, the electrical transport properties of these electrodeposited materials have caught the interest of few researchers except for Norris et al. [5], who used the indirect four-point probe method to measure the conductivity of the electrospun non-woven ultra-fiber mat of polyaniline doped with camphorsulfonic acid blended with polyethylene oxide (PEO). As the non-woven mat is highly porous and the “fill factor” of the fibers is less than that of a cast film, the measured conductivity tends to be lower than that of bulk [5]. In this paper, a direct method is used to measure the I -V curve and conductivity of the electrospun PAN-based carbon nanofibers. Commercial PAN powder and N,N-Dimethyl Formamide (DMF), in a ratio of 600 mg PAN to 10−5 m3 DMF, were used to prepare a solution. This mixture was vigorously stirred by an electromagnetically driven magnet at room temperature before it became a homogeneous polymer solution. The electrospinning was conducted in a homemade setup shown in Fig. 1. The DC power supply was an ES30-0.1P Model HV