Functionalized Nanoporous Gold Leaf Electrode Films for the Immobilization of Photosystem I

Ciesielski, P. et al. ACS Nano, Article ASAP (2008)

Purpose of the Study
The purpose of this study was to develop a technique for fabricating nanoporous gold leaf electrode films, and functionalize the surface of the electrode with PSI for solar energy conversion.

Methods
Nanoporous gold leaf was fabricated from an initial gold/silver alloy film. Immersion in concentrated nitric acid dissolved the silver, dealloying the film. The porous film was then placed on a gold/silicon support substrate. Characterization was performed using cyclic voltammetry and SEM. Self-assembled monolayers were formed by exposing the film to a variety of ω-terminated alkyl thiols. Presence of SAMs was determined using electrochemical impedance spectroscopy (EIS). Photosystem I was directly attached to the NPGL by functionalizing the electrode surface with terephthaldialdahyde (TPDA). Measurements were made of photocurrent enhancement with PSI adsorption.

Key Findings

• Maximum surface area enhancement occurs for short dealloying times, but maximum photocurrent enhancement occurs for longer dealloying times. This is due to the small pore size associated with short dealloying times.
• Immobilization of PSI on NPGL electrodes provides an increase in PSI-catalyzed photocurrent, compared to planar electrodes.

Definitions

• Cyclic voltammetry – A potentiodynamic electrochemical measurement which sweeps the working electrode potential linearly, and reverses direction when reaching a set potential. This can cycle several times during an experiment, and gives information about the oxidation and reduction of mediator species in solution.
• Electrochemical impedance spectroscopy – Probes energy storage in a device by measuring the impedance of a system over a range of AC frequencies.