Tailoring the Conductivity of Polypyrrole Films Using Low-Energy Platinum Ion Implantation Marsilea Adela Booth, †,‡ Je ́ rôme Leveneur, †,§ Alexsandro Santos Costa, † John Kennedy, §,⊥ and Jadranka Travas-Sejdic* ,†,⊥ † Polymer Electronics Research Centre (PERC), University of Auckland, Private Bag -92019, Auckland, New Zealand ‡ Institute of Environmental Science Research Ltd. (ESR), Private Bag 92-021, Auckland, New Zealand § National Isotope Centre, GNS Science, 30 Gracefield Road, Lower Hutt, New Zealand ⊥ MacDiarmid Institute for Advanced Materials and Nanotechnology, New Zealand * S Supporting Information ABSTRACT: Low-energy platinum ions were implanted with 15 keV under normal incidence into synthesized conducting polymer films with the aim to improve film conductivity and to demonstrate the use of implanted platinum in a simple sensing design. Conductivity measurements, cyclic voltammetry, and Raman spectroscopy were performed on samples both before and following ion implantation. Results display an optimum fluence of ion implantation for which polypyrrole films implanted with 2 × 10 16 at. cm -2 display and retain enhanced conductivity compared with nonimplanted samples. X-ray photoelectron spectroscopy (XPS) and scanning electron microscope-energy-dispersive X- ray spectroscopy (SEM-EDS) confirmed that implanted platinum is present mainly as Pt 0 and indicated that the depth and amount of ion implantation are in agreement with a simulated implantation profile. Raman spectroscopy showed a surface-enhanced Raman spectroscopy (SERS) effect with platinum’s presence. The advantageous increase in conductivity can be rationalized by two chemical modifications to the polymer upon high-fluence implantation: (1) an increase in the number of charge carriers (dications) within the polymer and (2) the presence of elemental platinum metal and its synergistic effect on conductivity. A simple DNA sensor was constructed on the basis of polypyrrole/Pt 0 films where Pt 0 was able to serve as anchoring points for DNA attachment as well as an enhancer of the film’s conductivity. This enabled a DNA sensor capable of successful detection of cDNA, and a good discrimination of noncDNA, thus opening a way to direct electrochemical biosensing on the basis of ion implanted highly conducting polymer films. ■ INTRODUCTION Ion implantation provides a means to modify mechanical, physical, and chemical properties of materials. 1 It works through the controlled incorporation of atoms of one material into another material thereby bringing about physical and chemical property changes. A variety of effects are observed from the radiation caused by ion implantation, such as an increase in conductivity, damage to the polymer backbone, amorphization, and damage or loss of polymer counterions 1-5 as well as the presence of the foreign chemical species within the sample. Current industries utilize this for semiconductor device fabrication 6 demonstrating the value and ease of implementation of the technique. Many existing research directions involve implantation of metals into nonconducting polymers. 5,7 By utilizing a conductive precursor, a smaller quantity of noble metal may be required to enhance conductivity thereby decreasing the cost of the composite. To this cause, intrinsically conducting polymers (ICPs) may fulfill the role of the conductive precursor material. With some mechanical properties of plastics, flexibility, control over growth, low-cost, and the ability to conduct upon oxidation, ICPs offer versatility in applications ranging from batteries and solar cells to biosensing. 8,9 Polypyrrole (PPy) in particular has been targeted for application in biosensors, which have the potential to aid progress in medical diagnostics and forensic investigations. 9,10 Previous studies on ion-implanted and swift heavy irradiated (∼Me V/u energy) conducting polymers, targeted for a range of applications such as p or n type junctions, capacitors, and actuators, 7,8,11 have reported a range of outcomes from decreases to increases in conductivity. 2,4,7,8,11-15 The energy, type, and fluence (number of ions deposited) of implanted ions affect the changes in conductivity observed. Increases in conductivity are reported and are explained by increases in ionic and charge carrier concentrations within the films, cross- linking of polymer chains and facilitated hopping of charge carriers within the polymer, 4,8,16,17 and light reordering of polymer chains. 12 Meanwhile, decreases in conductivity are thought to arise from damage to the conducting polymer rings (as revealed through X-ray photoelectron spectroscopy (XPS) Received: January 19, 2012 Revised: March 20, 2012 Published: March 21, 2012 Article pubs.acs.org/JPCC © 2012 American Chemical Society 8236 dx.doi.org/10.1021/jp300682q | J. Phys. Chem. C 2012, 116, 8236-8242