Date of Graduation

5-2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Microelectronics-Photonics (PhD)

Degree Level

Graduate

Department

Microelectronics-Photonics

Advisor/Mentor

Li, Jiali

Committee Member

Fritsch, Ingrid

Second Committee Member

Naseem, Hameed A.

Third Committee Member

Singh, Surendra P.

Fourth Committee Member

Wise, Rick L.

Keywords

Artificial Photosynthesis; Bio-solarcell; Lipid Membranes; Lipid-protein membranes; Photocurrent; Renewable Energy

Abstract

Motivated to produce electricity with photon activated ion pumps, the main purpose of this work was to characterize the photosynthetic membrane proteins bacteriorhodopsin (proton pump) and halorhodopsin (chloride pump). The proteins were re-suspended in lipid bilayers. For this work, an experimental set-up was built which included: chambers for lipid bilayer formation and characterization, lasers for ion pump activation, and an AxoPatch electrophysiology system for small photocurrent measurement. Lipid bilayer membranes were formed using mostly folding method: folding two monolayers together. The membranes were characterized by their resistance, capacitance, and generated photocurrent. Photocurrent was generated upon illumination of lipid-protein membranes with lasers. A green (532 nm) laser was used to illuminate bacteriorhodopsin containing membranes to produce proton-based positive photocurrent, while a purple (405 nm) laser was used to illuminate halorhodopsin containing membranes to generate chloride-based negative photocurrent. The investigation included: the generation of photocurrent using formed lipid-protein membranes and their voltage dependence, the study of the effect of laser intensity and protein concentration on the photocurrent amplitude and efficiency, the TEM-imaging of photocurrent generating lipid-protein solutions, and an equation that can help predict photocurrent amplitude in the defined protein concentration range.

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