Carbon nanotubes were grown on flexible polyimide substrates at temperatures below 400 degrees C as electrodes for extracellularly neuronal recording. The electrical charge-transfer and electrochemical properties of such CNT electrodes were enhanced by UV-ozone exposure, which induced the formation of C-O, C=O, and O-C=O bonds and reduced the CNT/electrolyte interfacial impedance while increasing the interfacial capacitance.