Electroactive biofilms (EABs) convert the chemical energy stored in reduced carbon compounds into electrical energy via extracellular electron transfer to metals and electrodes. EABs show also promise for wastewater treatment and electrobiosynthesis of bulk chemicals. Well-known electroactive microorganisms genera are Geobacter, Shewanella, and Desulfovibrio. Extracellular electron transfer in these microorganisms occurs either directly, through conductive biomolecules on their surface, or through microbially produced soluble electron transfer agents, or through a combination of the previous mechanisms. The core of EAB-based devices is the biofilm-electrode interface. In fact, both the chemistry and morphology of the electrode surface determine the microstructure and electroactivity of the biofilm.
Current EAB literature deals with low cost graphite electrodes. However, the interaction of other materials with electroactive biofilms is virtually unexplored.
Electroactive biofilms can be grown on transition metal oxide thin films, such as indium-doped tin oxide, obtained through pulsed laser deposition. The surface chemistry and morphology of these films can be tailored with great precision by changing the parameters of the deposition process. The addition of doping elements permits to change the electrical conductivity and the charge transfer resistance of the films. It is also possible to create micro- to nano-pores on the film, thereby increasing the surface available to electroactive biofilm and the electricity production when the biofilms are grown in electrochemical cells. Transparent metal oxides thin films permit to characterize EABs through various electrochemistry and biophotonic methods, such as cyclic voltammetry, visible and infrared spectroscopy, and confocal laser scanning microscopy.