Studies of redox reactions in electro-active proteins using optical impedance spectroscopy at single-mode waveguides

Xue Han; Sergio B. Mendes

doi:10.1117/12.2024106

11 September 2013 Studies of redox reactions in electro-active proteins using optical impedance spectroscopy at single-mode waveguides

Xue Han, Sergio B. Mendes

Author Affiliations +

Proceedings Volume 8812, Biosensing and Nanomedicine VI; 881207 (2013) https://doi.org/10.1117/12.2024106
Event: SPIE NanoScience + Engineering, 2013, San Diego, California, United States

Abstract

An electro-active platform based on a single-mode integrated optical waveguide over-coated with a 13-nm indium tin oxide film was developed for highly sensitive investigations on the kinetics of redox reactions from a sub-monolayer of cytochrome-c proteins. Optical impedance spectra (with and without cytochrome-c proteins present in the spectroelectrochemical flow-cell) were measured with the single-mode integrated optical waveguide for a 10-mV ac electric potential modulation. Significant changes in the ac component of the optical baseline response were observed, and a new analysis was developed to factor out the working electrode effects and deliver accurate results for the Faradaic process. Faradaic current density and active surface coverage were reconstructed at several modulation frequencies. As small as 7x10^-14 mole/cm² of cytochrome-c proteins were detected under such electric potential modulation leading to a faradaic current of about 200 nA/cm². Such level of faradaic current is extremely difficult to be isolated by other electrochemical techniques (e.g. electrical impedance measurements) due to the strong background created by an always present electric double layer. We were able to achieve those detection limits because the optical signal is immune to those events and can be tuned solely to the Faradaic process. This highly sensitive and accurate strategy of spectro-electrochemistry is proved powerful for measurements of extreme small amount of electro-active proteins and has the potential to be used in many other important electrochemical processes.

Citation Download Citation

Xue Han and Sergio B. Mendes "Studies of redox reactions in electro-active proteins using optical impedance spectroscopy at single-mode waveguides", Proc. SPIE 8812, Biosensing and Nanomedicine VI, 881207 (11 September 2013); https://doi.org/10.1117/12.2024106

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