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.

Modifying the conductivity of polypyrrole through low-energy lead ion implantation

“…The variation in outcomes is generally explained as effects arising from the type, energy and fluence of implanted ions [9]. With a relatively low implanted fluence as employed here a typical increase in conductivity is observed, as well as an increase in the number of defects present [6]. Other characteristics of ion implanted ICPs are changes to surface morphology, crystallinity, mechanical stiffness, electrochemical features, mechanical work outputs and stability [10,12,14,16,19,20].…”

“…X-ray photoelectron spectroscopy (XPS) was recorded on a Kratos Axis Ultra DLD (Kratos Analytical, Manchester U.K.), using monochromatic Al K a X-rays (1486.69 eV) with X-ray power of 150 W, under conditions previously specified [6]. Data analysis was performed using CasaXPS using Kratos' relative sensitivity factors, under conditions identical to those previously used [6].…”

“…Data analysis was performed using CasaXPS using Kratos' relative sensitivity factors, under conditions identical to those previously used [6]. Argon ablation of the film surface was performed using a 5 kV argon beam and an emission current of w10.4 mA, which was maintained between 10 and 12 mA throughout the experiment.…”

“…4A. Calculations of conductivity were performed using the formula for a thin sheet [6,29]. Freshly grown PPy films displayed conductivity on the order of 120 AE 20 S cm À1 .…”

“…Composition, characteristics and behavior are also examined. Platinum has been previously implanted [6], as a metal of high electrical conductivity. Lead, meanwhile, is a metal of lower electrical conductivity (lead displays about half the conductivity of platinum), is a commonly used metal for purposes such as soldering, is corrosion resistant, and is more abundant than platinum.…”