Polypyrrole nanowires

Fig. 21 SEM image of polypyrrole nanowires prepared using a nanoporous PCHE template. Reproduced from [91]... 

Polymers consisting of but not limited to poly thiophene, polypyrrole and poly aniline have been extensively used to make polymer nanofibers. In general, any metal that can be electroplated has most likely appeared in a nanowire. Semiconductors, polymers, and insulators have also been used in the design of nanowires.Furthermore, different metals can be plated in succession to give striped nanowires. 

Similar approach has also been taken by Ferain and Legras [133,137,138] and De Pra et al. [139] to produce nanostructured materials based on the template of the membrane with etched pores. Polycarbonate film was also of use as the base membrane of the template, and micro- and nanopores were formed by precise control of the etching procedure. Their most resent report showed the successful formation of ultrasmall pores and electrodeposited materials of which sizes were as much as 20 nm [139]. Another attractive point of these studies is the deposited materials in the etched pores. Electrochemical polymerization of conjugated polymer materials was demonstrated in these studies, and the nanowires based on polypyrrole or polyaniline were formed with a fairly cylindrical shape reflecting the side wall structure of the etched pores. Figure 10 indicates the shape of the polypyrrole microwires with their dimension changes by the limitation of the thickness of the template. 

A very recent paper details the biomolecular functionalization of a polypyrrole nanowire. ZnSe/CdSe quantum dots were functionalized with avidin and these quantum dots were incorporated into a polypyrrole nanowire during its electrochemical formation between two electrodes 100 nm apart [32], Biotin with a DNA strand attached was shown to modulate the conductivity of the avidin nanowire, but not an unfunctionalized polypyrrole nanowire fabricated similarly. Presumably, the DNA-biotin-avidin complex would also be sensitive to changes in the hybridization state of the DNA. 

Gao, M., Dai, L., and Wallace, G.G. 2003. Glucose sensors based on glucose-oxidase-containing polypyrrole/aligned carbon nanotube coaxial nanowire electrodes. Syntheticmet 137, 1393-1394. 

Fig. 13.6 In-situ nanowire synthesis The working electrode and counter electrode are contacted by probe tips. A probe tip is also used as a pseudo reference electrode, submerged in the solution containing the analyte. The nanowire (red) is growing in the direction of the arrow, from the working electrode to the counter electrode, confined to a predetermined path by the photoresist. The inset shows an SEM micrograph of a polypyrrole nanowire fabricated by in-situ synthesis...

Figure 3.12 SEM (a) and TEM (b) micrographs of 100-nm-diameter polypyrrole nanowires after the removal of alumina template membranes. (Reprinted with permission from Reference [54]. Copyright 2007 American Chemical Society.)...

Extremely low-dimensional conducting nanowires (as small as 3 nm in diameter) for use in nanoelectronics can be produced with the electrospinning technique [103]. Using template methods, insulating PLA fibers with an average diameter of 200-700 nm as core materials were electrospun and subsequently coated with thin 50-100 nm films of polyaniline or polypyrrole by in situ polymer deposition methods. The PLA core fibers decompose upon relatively mild thermal treatment under inert atmosphere, leaving... 

J. Li and X. Lin, Electrocatalytic oxidation of hydrazine and hydroxylamine at gold nanoparticle-polypyrrole nanowire modified electrode. Sensors Act. B, 126, 527-535 (2007). 

J. Li and X. Lin, A composite of polypyrrole nanowire platinum modified electrode for oxygen reduction and methanol oxidation reactions, J. Electrochem. Soc., 154, B1074— B1079 (2007). 

T. Zhang, R. Yuan, Y. Chai, W. Li, and S. Ling, A novel nonenz3fmatic hydrogen peroxide sensor based on a polypyrrole nanowire-copper nanocomposite modified gold electrode, Sensors, 8, 5141-5152 (2008). 

Figure 9.17 AFM images of PPy-DNA nanowires and nanopores on a SiOJSi surface (a) nanowires observed 3 h after preparation (b) and (c) two representative images of nanorope samples observed after standing for 24 h. (Reprinted with permission from Advanced Functional Materials, Self-Assembly of DNA-Templated Polypyrrole Nanowires Spontaneous Formation of Conductive Nanoropes by S. Pruneanu, S. A. Farha Al-Said, L. Dongetal., 18, 16, 2444-2454. Copyright (2008) Wiley-VCH)...

S. Pruneanu, S.A.F Al-Said, L. Dong, T.A. Hollis, M.A. Galindo, N.G. Wright, A. Houton, and B.R. Horrocks, Self-assembly of DNA-templated polypyrrole nanowires spontaneous formation of conductive nanoropes, Adv. Func. Mater., 18, 2444-2454 (2008). 

Figure 10.39 An optical micrograph of a wire grown from aqueous EDOT/PSS solution. Inset a scanning electron micrograph of a PEDOT nanowire. The scale bars represent 10 pm except for those in the insets, which denote 500 nm. (Reprinted with permission from Applied Physics Letters, Directional growth of polypyrrole and polythiophene wires by P. S. Thapa, D.J. Yu,J. P. Wicksted eta ., 94, 3 (2009) American Institute of Physics)...

S.C. Hernandez, D. Chaudhuri, W. Chen, N.V. Myung, and A. Mulchandani, Single polypyrrole nanowire ammonia gas sensor. Electroanalysis 19, 2125-2130 (2007). 

Y. Tian, J.X. Wang, Z. Wang, and S.C. Wang, Solid-phase extraction and amperometric determination of nitrite with polypyrrole nanowire modified electrodes. Sens. Actuat. B, 104, 23-28 (2005). 

S. Aravamudhan and S. Bhansali, Development of micro-fluidic nitrate-selective sensor based on doped-polypyrrole nanowires. Sens. Actuat. B, 132, 623-630 (2008). 

Gao et al. reported the synthesis of aligned coaxial nanowire of carbon nanotubes with polypyrrole or polyaniline using a cyclic voltammetric technique [50]. DC conductivity of the polyaniline-coated nanotube film was measured to be 10 S cm , which is higher than that of polyaniline film electrochemically deposited on a gold plate under the same conditions. This is possibly due to the doping effect associated with carbon nanotubes. 

The fabrication of polypyrrole wires via electropolymerization within poly(methyl methacrylate) nanochannels on an indium tin oxide (ITO) substrate was reported by Chen et al. [53]. The electrochemical synthesis of polypyrrole was performed by a cyclic voltammetry method in aqueous 0.1 M NaC104 containing 0.1 M pyrrole monomer. The potential was scanned 10 times between -0.7 and +0.6 V vs. Pt at a scan rate of 100 mV s . The nanochannels act as templates for electropolymerization of polypyrrole nanowires. 

---