Ion Track Technology


Reimar Spohr

PostHeaderIcon Abstract

Diode-like single-ion track membrane prepared by electro-stopping; Apel, P. Yu.; Korchev, Yu. E.; Siwy, Z.; Spohr, R.; Yoshida, M..; Nucl. Instrum. Methods Phys. Res., Sect. B (2001), 184(3), 337-346

The preparation of an asymmetric membrane in poly (ethylene terephthalate), PET, is described, using a combination of chemical and electro-stopping. For this purpose, a single-ion irradiated PET film is inserted into an electrolytic cell and etched from one side in 9 M sodium hydroxide while bathing the other side in a mixture of 2M KCl and 2M HCOOH (1:1 by volume), electrically retracting the OH- ions from the tip of the etch pit during pore break-through. When a preset current has been reached, the etch process is interrupted by replacing the etching solution with acidic 1 M potassium chloride solution. After etching, the current-voltage (I-V) characteristic is determined under symmetric bathing conditions, immersing both sides of the membrane in KCl solutions of identical concentration (0.01 to 1 M) and pH (3 to 8). The I-V characteristic is strongly nonlinear, comparable to that of an electrical diode. If the polarity during etching is reversed, pushing the OH- ions into the tip of the etch pit, the resulting pores are larger and the degree of asymmetry smaller. The importance of electro-stopping is compared with chemical stopping.