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Photogating of ionic currents across a lipid bilayer
C M Drain1, B Christensen, D Mauzerall
1Rockefeller University, New York, NY 10021.
Summary
Photoformation of metalloporphyrin cations in lipid bilayers modulates ion flow, creating a net charge gain. This photogating effect, driven by space charge, enhances conductivity significantly, acting as an organic field-effect phototransistor.
Area of Science:
- Biophysics
- Materials Science
- Organic Electronics
Background:
- Metalloporphyrins are photoactive molecules with potential applications in electronic devices.
- Lipid bilayers serve as model systems for biological membranes and have been explored for electronic functionalities.
Purpose of the Study:
- To investigate the photoinduced changes in ionic conductivity within a lipid bilayer system.
- To explore the mechanism of photogating and its potential for signal amplification in organic field-effect phototransistors.
Main Methods:
- Photoformation of metalloporphyrin cations within a lipid bilayer.
- Measurement of ionic currents with varying concentrations of hydrophobic ions (tetraphenylphosphonium and tetraphenylboride).
- Analysis of conductivity changes and charge gating effects.
Main Results:
- Photoformation of metalloporphyrin cations altered ionic currents, increasing negative ion flow and decreasing positive ion flow.
- Conductivity changes were dependent on hydrophobic ion concentration, with a 3.6-fold increase observed under saturated tetraphenylboride conditions.
- A 15-fold conductivity increase was achieved with carbonyl cyanide 3-chlorophenylhydrazone, demonstrating a net charge gain 300 times greater than the photogenerated charge.
Conclusions:
- Photogating in lipid bilayers, driven by space charge effects, can lead to significant signal amplification.
- This phenomenon establishes a functional organic field-effect phototransistor with potential for enhanced sensitivity.