Simple multistep assembly of hybrid carbon material based microelectrode for highly sensitive detection of neurotransmitters

The miniature sensor has become one of the most popular tools for electroactive biomarker molecule sensing, but the challenge for preparing microelectrodes of hybrid materials still exists. In this contribution, we report a novel strategy for constructing a hybrid nitrogen-doped graphene microelectrode (NGR ME) to efficiently and reliably detect neurotransmitters. The construction procedure is a simple, green, easy-to-operate multistep assembly sequence coated on a customizable micro/nanoscale substrate. Meanwhile, polydopamine (PDA) is a biologically friendly polymer and playing multiple roles. It starts from classic adhesion ability on micro/nanoscale substrates, and its rich amino functional groups electrostatically adsorbed with graphene oxide (GO). Finally, it provided a nitrogen source for nitrogen atom doping in hybrid graphene materials. Since the self-assembled multilayers undergo a pyrolysis process, the synergistic interaction between the multilayers has endowed the microelectrodes excellent electrical conductivity and electrocatalytic performance. This work demonstrates our approach to designing microelectrodes with customizable sizes, proving that it can be used for neurotransmitter sensing with high sensitivity, excellent selectivity and low detection limit (0.69 nM for DA, 6.5 nM for 5-HT), and also can be implanted into a cannula to make a portable and micro-volume device for detecting real human serum samples, which demonstrates promising prospects in clinical diagnosis.