Tailoring the Conductivity of Polypyrrole Films Using Low-Energy Platinum Ion Implantation

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 × 10¹⁶ 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 Pt⁰ 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/Pt⁰ films where Pt⁰ 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