Electronic transport in single polyaniline and polypyrrole microtubes

A Review on Electronic Transport Properties of Individual Conducting Polymer Nanotubes and Nanowires

“…3, it was found that the polypyrrole tube with a 560-400 nm outer diameter is poorly conductive and the room-temperature conductivity is only 0.13-0.29 S/cm. When the outer diameter decreased to 130 nm, the conductivity of the single nanotube increased to 73 S/cm (Long et al, 2005b). Such conductivity dependence on diameter was observed not only for templatesynthesized polymer tubes/wires but also for self-assembled polypyrrole tubes, which indicates that the polymer tubes/wires prepared by these two different methods have similar structural characteristic: the smaller the diameter, the larger the proportion of ordered polymer chains.…”

“…Diameter dependence of room-temperature conductivity of individual polypyrrole micro-/nanotubes prepared by template-free self-assembly method. (Long et al, 2005b) Since the electrical properties of conducting polymers are strongly influenced by the effect of disorder and temperature, three different regimes (namely, insulating, critical, and metallic regimes close to the metal-insulator transition) have sorted out based on the extent of disorder and conductivity dependence on temperature (Yoon et al, 1994;Menon et al, 1998;Heeger, 2002). In the insulating regime, for a three-dimensional system, the temperature dependent resistivity usually follows Mott variable-range hopping (VRH) model: ρ(T) = ρ 0 exp(T M /T) 1/4 .…”

“…Typical SEM images of an isolated polyaniline nanotube/wire (a, b and c) and polypyrrole nanotube/wire (d), and the attached platinum microleads. (Long et al, 2003a(Long et al, & 2005b The electrical connection between the Pt microleads and the sample holder was made by highly conductive silver paste and gold wires and the electrical measurements of individual polymer nanotube/wire were carried out using a Physical Property Measurement System from Quantum Design and a Keithley 6487 picoammeter/voltage source, or a Keithley 236 source-measure unit in an Oxford helium gas flow cryostat covering a wide temperature range from 300 down to 2 K. The four-probe resistance was measured by applying a very small current in the linear part of the I-V characteristics. The two-probe resistance was determined under V bias = 0.02 V, while no rectifying behaviour has been measured in our samples.…”

“…The method used to attach Pt microleads on an isolated polymer nanotube/wire was described in previous publications (Long et al, 2003a(Long et al, & 2005b. First, polymer nanotubes/ wires were ultrasonically dispersed in ethanol for template-free prepared nanotubes/wires and in dichloromethane for template-prepared PEDOT nanowires.…”

“…A common approach was generally realized by dispersing nanotubes/wires on patterned micro-or nanoelectrodes prepared by photo-lithography, electron-beam lithography and focused-ion beam deposition, followed by the subsequent searching of nanofibers just lying on the two or four electrodes only (Kim et al, 1999;MacDiarmid et al, 2001;Park et al, 2003;Lee et al, 2004;Aleshin et al, 2004;Samitsu et al, 2005;Joo et al, 2005;Aleshin, 2006;Gence et al, 2007Gence et al, & 2008Callegari et al, 2009). Particularly, focused-ion beam assisted deposition technique has been employed to attach metal microleads on isolated www.intechopen.com A Review on Electronic Transport Properties of Individual Conducting Polymer Nanotubes and Nanowires 225 nanotubes/wires directly (Long et al, 2003a(Long et al, , 2004b(Long et al, & 2005bHuang et al, 2006;Long et al, 2006c;Duvail et al, 2007;Lu et al, 2007;Long et al, 2008aLong et al, & 2009b. There are also reports demonstrating a directed electrochemical nanowire assembly technique for the fabrication and measurement of polymer nanowire arrays between pre-patterned electrodes (Ramanathan et al, 2004).…”