Boron and nitrogen co-doped vertical graphene electrodes for scalp electroencephalogram recording

Graphene has shown immense potential for applications in monitoring scalp electroencephalogram (EEG) signals. However, the radial head shape, high-resistance scalp cuticle, and hair prevent graphene from contacting skin, resulting in high contact impedances and low signal-to-noise ratios (SNRs) in EEG signals. Therefore, B and N co-doped vertical graphene (BNVG) electrodes are synthesized to improve the skin affinity and sweat adsorption capacity. X-ray photoelectron spectroscopy results show that the series of BNVG electrodes comprise B-doping contents of 1.25–9.85 at% and N-doping contents of 1.12–6.48 at%. A systematic analysis of the effects of B and N atom contents on the real-time scalp-contact resistances, EEG correlation coefficients between BNVG and Ag/AgCl electrodes, and SNRs of the EEG signals are conducted. The BNVG electrode comprising 4.47 at% B and 3.18 at% N is determined as the optimum electrode for scalp EEG signal acquisition. Furthermore, an EEG cap assembled with 19 optimized BNVG electrodes records spontaneous and evoked EEG signals. The BNVG-based EEG cap used with sweat or aqueous NaCl solution is confirmed to be advantageous and can be applied to clinical and brain-computer interface systems.