Etched ion-track membranes are fabricated at GSI by heavy ion irradiation and chemical etching. Pore density and pore arrangement are selected by the irradiation conditions. Pore density can be adjusted during the irradiation step between 1 pore/sample and ~ 1010 ions/cm2. Pore size and geometry are controlled by the etching parameters. Typical pore sizes range between ~ 15 nm and few micrometers in diameter. Using this technique, cylindrical, conical, and bi-conical pores have been fabricated.
- Single nanopore membranes are fabricated at GSI by irradiation with a single heavy ion and subsequent chemical etching.
- After irradiation, the polymer foil is introduced in a two-compartment electrochemical cell. The ion track created by the ion is selectively etched. The etching process is monitored by recording the current-time characteristics, using two electrodes immersed each in one of the two compartents. Geometry and size of the resulting nanopore are controlled by the etching conditions (solution, concentration, temperature).
- Using the same electrochemical cell, two Ag/AgCl electrodes and corresponding electronic devies, the ionic transport through the single nanopore is investigated. These solid state polymeric nanopores are employed as model systems to study the controlled passage of ions through nanochannels. To understand the ionic flow through natural ion channels and artificial nanopores is of fundamental interest in biology, physics and chemistry.
- Single nanopore membranes are also used as sensors to detect the pass of a single molecules, viruses, or particles. In these experiments, the current through the single nanopore at a given potential is monitored. Variations of the current (events) are then correlated to the single objects blocking partly the nanopore on their way through.
- Another strategy to develop responsive systems and single nanopore sensors rely in incorporating sensing elements into polymer nanochannels.
Saccharide/glycoprotein recognition inside synthetic ion channels modified with boronic acid, Q.H. Nguyen, M. Ali, R. Neumann, W. Ensinger, Sensors and Actuators B 162 (2012) 216–222.
Biomolecular conjugation inside synthetic polymer nanopores via glycoprotein-lectin interactions, M. Ali, P. Ramirez, M.N. Tahir, S. Mafe, Z. Siwy, R. Neumann, W. Tremel, W. Ensinger, Nanoscale 3 (2011) 1894-1903.
Hydrogen peroxide sensing with horseadish peroxidase-modified polymer single conical nanochannels, M. Ali, M.N. Tahir, Z. Siwy, R. Neumann, W. Tremel, W. Ensinger, Analytical Chemistry 83 (2011) 1673-1680.
Sequence-specific recognition of DNA oligomer using peptide nucelic acid (PNA)-modified synthetic ion channels: PNA/DNA hybridization in nanoconfinemed environment, M. Ali, R. Neumann, W. Ensinger, ACS Nano 4 (2010) 7267–7274.
Layer by layer assembly of polyelectrolytes into ionic current rectifying solid state nanopores: insights from theory and experiment, M. Ali, B. Yameen, J. Cervera, P. Ramírez, R. Neumann, W. Ensinger, W. Knoll, O. Azzaroni, J. Am. Chem. Soc. 132 (2010) 8338–8348.
Nanopores in track-etched polymer membranes characterized by small-angle x-ray scattering, T.W. Cornelius, B. Schiedt, D. Severin, G. Pepy, M. Toulemonde, P.Y. Apel, P. Boesecke, C. Trautmann, Nanotechnology 21 (2010) 155702.