Cite this: RSC Advances, 2013, 3, 2154 Received 19th September 2012, Accepted 13th December 2012 Current dependent formation of PEDOT inverse nanotube arrays3{ DOI: 10.1039/c2ra22222a www.rsc.org/advances Damian Kowalski,* Sergiu P. Albu and Patrik Schmuki PEDOT nanostructures with distinct patterns can be formed by means of electrodeposition in titania nanotubes. The deposition process critically depends on the current protocol, leading to selective filling of the inner and/or outer space of the tubes. The approach allows for synthesis of vertically aligned PEDOT–titania composites or polymer nanostructures in the form of PEDOT inverse-nanotube-arrays and PEDOT nanopore-arrays. Intrinsically conducting polymers, such as polypyrrole (PPy), polyaniline (PANI), poly-3,4-ethylene-dioxythiophene (PEDOT) and poly-3hexylthiophene (P3HT), have been of wide interest since the first demonstration of electric conductivity in doped polyacetylene by Shirakawa et al. 1 Presently, the polymers find applications in plastic solar cells, 2,3 fuel cells, 4 self-healing materials, 5 light-emitting diodes, 6 actuators, 7 electro-catalytic materials, 8 etc. The position of the HOMO–LUMO energy gap and light absorption properties determine the desired application of the polymer. For instance PEDOT is often used as a charge collector in plastic solar cells and is considered as a transparent electrode in touchscreens and electronic paper due to its transparency for visible light. 3,9 The nanoscale arrangement of the polymers is typically achieved by formation of nanofibers, nanotubes, nanowires, and micro/nano-spheres by using hard alumina templates, micelle soft templates, mesoporous silica spheres, interfacial polymerization and dispersion polymeriza- tion. 10,11 Recently, 1-D TiO 2 nanotubes became of high interest due to a very high degree of control over its geometry and functional properties, arising from the semiconductive nature of titania. 12 Combining the anodization process (TiO 2 nanotubes) and electrodeposition (polymers) it is possible to construct organic– inorganic composites or use TiO 2 nanotubes as a template for the formation of polymers with unique geometrical architectures. Herein we demonstrate an electropolymerization approach to control the geometry of PEDOT by deposition in a TiO 2 nanotubular electrode. Scheme 1 shows the PEDOT nanostruc- tures formed in the TiO 2 nanotubes by pulsed deposition. By adjusting the current pulse protocol parameters two distinctly different selective deposition patterns can be established. The PEDOT can be either deposited on both sides of the nanotube wall or selectively in space in between the tubes, and unique organic– Department of Materials Science and Engineering, University of Erlangen-Nuremberg, Martensstr. 7, 91058 Erlangen, Germany. E-mail: kowalski@cat.hokudai.ac.jp; Fax: (+49) 9131-85-275-82; Tel: (+49) 9131-85-275-82 3 Electronic supplementary information (ESI) available. See DOI: 10.1039/c2ra22222a { The work was financially supported by a Marie Curie grant under the 7th Research Framework Programme FP7-PEOPLE-2009RG-249169 as well as by DFG and DFG cluster of excellence EAM. Scheme 1 Synthesis of PEDOT inverse-nanotube-array and nanopore-array by selective electrodeposition with a pulse current at 1.0 and 0.8 mA, respectively. The upper image represents a titania nanotube electrode, the middle ones are composites of titania and PEDOT and the lower images represent nanostructures of PEDOT obtained after dissolution of the template. RSC Advances COMMUNICATION 2154 | RSC Adv., 2013, 3, 2154–2157 This journal is ß The Royal Society of Chemistry 2013 Published on 14 December 2012. Downloaded by Universitat Erlangen Nurnberg on 02/09/2013 17:59:12. View Article Online View Journal | View Issue