Photoactive Films of Photosystem I on Transparent Reduced Graphene Oxide Electrodes: Supporting Information Preparation of RGO film To prepare the reduced graphene oxide (RGO) electrode, we first functionalized the glass slide by soaking the glass in 1% aminopropyl triethoxysilane

To prepare the reduced graphene oxide (RGO) electrode, we first functionalized the glass slide by soaking the glass in 1% aminopropyl triethoxysilane (APTES) in ethanol for 1 hour. We then washed the slide with ethanol. Previously, we tried washing the slide with water but this caused the slide to become opaque. Also, we originally cleaned the slide first with piranha solution, but eliminating this step did not appear to change the results and made the process much faster, safer, and easier. Then we spin coated graphene oxide (GO) onto the functionalized glass slide. We used 500 μL of 5 mg/mL GO in ethanol and spin coated at 800 rpm for 4 min. Originally, we tried to spin coat the GO out of water, but the resulting film was extremely uneven. We then reduced the GO film via a hydrazine vapor reduction method. We placed the GO coated slides in a small petri dish and then placed this small petri dish in a larger petri dish that also contained 1 mL of hydrazine. We covered the larger petri dish and heated it to 30 °C for 3 hrs. The color change from light brown to dark grey visibly indicates the reduction of the GO. The following figure summarizes the method and parameters for the RGO film preparation (SFigure 1).