Fabrication of Conducting Polymer Nanowires

The advancement of nanotechnology provides opportunities for fabrication of nanoscale materials and higher performance devices using nanomaterials with high precision. Currently, various nanomaterials and nanostructures in the range of 1 to 100 nm have been produced by chemical and physical methods. Among various nanostructured materials, one-dimensional (1D) materials, such as nanowires, nanotubes, nanorods, and nanobelts, have potential applications in nanoscale electronics (Cui & Lieber, 2001), optoelectronics (Duan et al., 2001), photonics (Gudiksen et al., 2002; Huang et al., 2001), sensors (Cui et al., 2001), and solar cells (Law et al., 2005) due to their unique electrical, chemical, and optical properties (Li et al., 2006; Thelander et al., 2006; Wang et al., 2008). Nanowires are useful in chemical or biological sensors for detecting single molecules because they have a high surfaceto-volume ratio and a highly sensitive 1D nanostructure that gives rise to large conductivity change associated with binding molecules (Cui et al., 2001; Ramanathan et al., 2005). Conducting polymers, such as polypyrrole, polyaniline, polythiophene, and their derivatives, are promising materials for synthesis of nanostructured materials and devices (Langea et al., 2008; Malinauskas et al., 2005). Compared with other materials, conducting polymers have some unique electrical, chemical, and optical properties because of their conjugated structures, and they are easily synthesized using chemical or electrochemical synthetic methods at room temperatures with low cost (Aleshin, 2006; Briseno et al., 2008; Guimard et al., 2007; Xia et al., 2010). Conducting polymers have electrical and optical properties similar to those of metals and semiconductors, while maintaining the flexibility and properties commonly associated with conventional polymer substances (Dai et al., 2002; Heeger, 2002; Shirakawa, 2002). For example, the electrical conductivity of these polymers can be adjusted from an insulator to traditional metals by varying the species and concentrations of doping ions. Undoped conducting polymers with conductivities of 10-10 to 10-5 S cm-1 can be changed into semiconducting or metallic materials with conductivities of 1 to 104 S cm-1 through a chemical or electrochemical doping process (MacDiarmid, 2002). Also, optical absorption bands and mechanical volume of conducting polymers can be changed by entrapped doping ions. Therefore, they have been used for various applications such as electronic devices (Hashizume, 2006), optoelectronic devices (Noy et al., 2002), actuators (Berdichevsky & Lo, 2006), transistors (Alam et al., 2005), and chemical sensors (Bangar et al., 2009; García-Aljaro et al., 2010). In recent years, 1D conducting polymer nanostructures have been demonstrated to have improved performance with low dimensionality. Many different fabrication methods have