Preparation Of Boron And Nitrogen Co-doped Vertical Graphene And Its Electroencephalographic Sensing Properties

Graphene and its derivatives are widely used in wearable sensors such as electronic skin,ECG and EEG electrodes due to their high electrical conductivity,biocompatibility,and electrical and electrochemical stability.In particular,the vertically grown graphene film effectively solves the layer-by-layer stacking problem of graphene sheets,and the doping method can control the Fermi level of graphene,which is expected to further improve the electrophysiological sensing performance of graphene.In this project,a series of boron and nitrogen co-doped vertical graphene(BNVG)electrodes were synthesized by chemical vapor deposition technology.By introducing active sites such as B-C,N-C,andB-N-C,the skin affinity,sweat adsorption capacity and electrochemical activity were improved.This develops BNVG electrodes and EEG caps with low scalp contact impedance and high signal-to-noise ratio for electroencephalography(EEG).First,a series of boron and nitrogen co-doped vertical graphene(BNVG)electrodes were fabricated by chemical vapor deposition.By adjusting the doping ratio of boron and nitrogen,it is found that the growth direction of BNVG nanosheets does not change,but its thickness and crystallinity are affected.With the increase of boron and nitrogen fluxes and the decrease of methane fluxes,the boron and nitrogen doping amounts in BNVG nanosheets increased significantly,with boron doping amounts reaching 1.25?9.85 at% and nitrogen doping contents ranging from 1.12 to 6.48 at%.Secondly,taking boron and nitrogen atomic contents as independent variables,the variation law of real-time scalp contact resistance,EEG correlation coefficient(R)between BNVG and commercial electrodes,and SNR of EEG signals was systematically analyzed.EEG signal analysis showed that the BNVG electrode with boron content of 4.47 at% and nitrogen content of 3.18 at% had relatively low scalp contact impedance(4.47 k?),high R(99.45%),high SNR(10.16 dB)and long-term Stability,is the best electrode for scalp EEG signal acquisition.In addition,19 optimizedBNVG electrodes were used to assemble the EEG cap,and the sensing performance of spontaneous and visually evoked EEG signals was tested,and high SNR and accurate EEG signals were obtained,proving the reliability of its practical application.The BNVG electrodes and EEG caps developed in this paper can be applied to clinical EEG pathological analysis and visually evoked braincomputer interface systems.