Numerous advancements have been made in transparent electrode technologies that can complement optogenetics and imaging modalities. However, several obstacles restrict the design and material of electrode devices, including the required flexibility, transparency, low impedance, high charge storage
capacity (CSC), and high charge injection capacity (CIC), among others. The impedance of transparent graphene arrays is higher, and its CIC is significantly lower than platinum, a metal typically employed for electrophysiological recording and stimulation. It is possible to enhance the electrochemical properties
of planar, transparent graphene electrodes by functionalizing their surfaces with platinum nanoparticles (Pt NPs), effectively increasing the electrode surface area. Existing research on platinum nanoparticles on transparent graphene electrodes has solely focused on simultaneous electrical recording and optical imaging of neuronal activity. There is currently no quantitative evidence of the extent to which platinum nanoparticles can impact the stimulating properties of transparent graphene electrodes and any indication of the stability of the coating. Therefore, material and electrochemical device characterizations were conducted to compare the recording and stimulating properties of graphene versus graphene with Pt NPs of varying surface densities.