A simple method for amino-functionalization of carbon nanotubes and electrodeposition to modify neural microelectrodes

Aiming to improve the charge transfer ability at the neural electrode interface, a new and simple method for amino-functionalization of carbon nanotubes (CNTs) has been attempted, and the amino-functionalized CNTs after quaternization were electrodeposited onto pretreated Pt microelectrodes using an 80 V cell voltage in anhydrous solvent. The formation of amino-functionalized CNTs and electrodeposition of the functionalized CNTs were confirmed by Fourier transform infrared (FT-IR) spectroscopy and SEM images respectively. The deposited electrodes exhibited a reduction by 91% in the electrode impedance at 1 kHz compared to smooth Pt electrodes. In addition, the CNT deposited electrodes possessed a large charge storage capacity, and provided an increased safe charge injection (Qinj) limit (1.6–2.0 mC/cm2) that is ten times higher than that of Pt electrodes. Electrochemical stability is another important characteristic required by neural electrodes. It was found that the CNT deposited microelectrodes were very stable during electrical stimulation, which is highly desirable for implantable neural electrodes. In summary, this study developed an easy and mild coating method for elevating the safe charge injection limit of neural microelectrodes, which can be applied to neural prostheses such as visual prostheses.