Effect of graphene oxide on affinity-immobilization of purple membranes on solid supports

The effect of graphene oxide (GO) on the surface fabrication of purple membranes (PM) containing photosensitive bacteriorhodopsin is first reported in this study. GO was initially modified with biotin and then coupled with oxidized avidin to generate a GO-avidin complex, which was subsequently used as a linker to immobilize biotinylated PM (b-PM) onto amine-functionalized supports. Indium-tin-oxide glass coated with the GO-avidin complex was more hydrophilic than the electrode coated only with oxidized avidin, and the successive b-PM adsorption yielded a 1.4-fold higher (410 nA/cm(2)) photoelectric activity. AFM analysis on mica revealed that the GO-avidin complex layer had less surface roughness and dissipation energy than the pure oxidized avidin linker layer. For subsequent b-PM fabrication, GO addition not only reduced the stacking of immobilized b-PM patches but also improved their interior compactness and surface smoothness. This study demonstrates a convenient way to introduce GO into PM fabrication technology to provide enhanced surface morphology and photoelectric activity.