Available online at www.sciencedirect.com Electrochimica Acta 53 (2008) 5092–5099 The fabrication and characterization of inkjet-printed polyaniline nanoparticle films Aoife Morrin a , Orawan Ngamna c , Eimer O’Malley a , Nigel Kent b , Simon E. Moulton c , Gordon G. Wallace c , Malcolm R. Smyth a , Anthony J. Killard a,∗ a School of Chemical Sciences, National Centre for Sensor Research, Dublin City University, Dublin 9, Ireland b School of Mechanical & Manufacturing Engineering, National Centre for Sensor Research, Dublin City University, Dublin 9, Ireland c ARC Centre of Excellence for Electromaterials Science, Intelligent Polymer Research Institute, University of Wollongong, Northfields Avenue, Wollongong, NSW 2522, Australia Received 21 December 2007; received in revised form 30 January 2008; accepted 2 February 2008 Available online 12 February 2008 Abstract This paper reports on the fabrication and characterization of electrodes modified with conducting polymer nanoparticle films, produced via inkjet printing. The polyaniline nanoparticle formulations were deposited via a desktop inkjet printer onto screen-printed carbon-paste electrodes (SPE), polyethylene terephthalate (PET) and gold-PET and their morphology studied at a range of length scales using profilometry, scanning electron microscopy and atomic force microscopy. The deposited films were found to form continuous polymer films depending upon film thickness, which was in turn dependent on the number of prints performed. The inkjet-printed films exhibited a smooth morphology on the SPEs at the micro-dimensional scale, as a result of the aggradation and coalescing of the nanoparticles upon deposition. The resulting modified electrodes were both conductive and electroactive, possessing good reversible polyaniline electrochemistry. Such a combination of materials and processing offers the potential of producing a range of low cost, solid state devices such as sensors, actuators and electrochromic devices. © 2008 Elsevier Ltd. All rights reserved. Keywords: Inkjet printing; Polyaniline; Nanoparticles; Screen-printed electrodes; Sensor 1. Introduction Conducting polymers are a unique class of organic materials that exhibit the electrical and optical properties of both metals and semiconductors [1]. They offer great prospects for prac- tical applications due to their levels of conductivity, low cost, and ease of synthesis. Among all of the conducting polymers, polyaniline (PANI) is probably the most widely studied because it has a broad range of tunable properties derived from its struc- tural flexibility. It has great potential in numerous applications including sensors, rechargeable batteries, light-emitting diodes, corrosion protection of metals and gas separation membranes. Yet, like many other electrically conducting polymers, PANI has proved difficult to exploit for a number of reasons. It is insolu- ∗ Corresponding author. Tel.: +353 1 700 7871; fax: +353 1 700 7873. E-mail address: tony.killard@dcu.ie (A.J. Killard). ble in common solvents, seriously hindering its processability. The monomer, aniline, is a carcinogen. It must be distilled prior to use and stored under nitrogen. Finally, acidic conditions are required for the formation of the most highly conductive form of PANI, which does not lend itself to entrapment of pH-sensitive materials such as proteins [2]. Recent breakthroughs in the synthesis and fabrication of con- ducting polymers with nanodimensional control have managed to overcome the issue of processability. A stable nanodispersion has an indistinguishable appearance from a true solution, and more importantly can be handled and applied in a similar fash- ion [3]. In addition, enhanced properties of conducting polymer materials become apparent at the nanodimension such as higher conductivity and more rapid, discrete, electrochemical switch- ing processes; properties directly applicable in electrode devices [4]. To date, several techniques have been employed in the fab- rication of polymer thin films, such as thermal evaporation, 0013-4686/$ – see front matter © 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.electacta.2008.02.010