Developing Atomically Layered Heterostructures as Electrochemical Dopamine Sensors

Abstract

Atomically thin materials, such as graphene layers, have received an exponentially growing interest for biochemical sensing applications. Their high surface-to-volume ratio and exceptionally tunable electronic properties allow them to respond to  specific analytes with high sensitivity. The electrochemical sensing of dopamine, a key neurotransmitter, is an essential analytical tool for studying complex nervous systems. Graphene is a favorable sensing material for dopamine detection due to its strong π−π interaction with the aromatic rings of dopamine. However, the minimal charge density at pristine graphene layers limits the electrochemical kinetics of dopamine electrooxidation. In the study, atomically layered heterostructures composed of graphene and molybdenum trioxide (MoO3) were developed to enhance the electrochemical activity towards dopamine reaction. The high work function of MoO3 induced spontaneous hole doping of graphene, leading to enhanced charge density at the graphene surface. Graphene, hexagonal boron nitride (hBN) and MoO3 were mechanically exfoliated and assembled into heterostructures with a transfer system. The presence of MoO3 in the heterostructure was found to increase the graphene sheet conductance by more than two folds, indicating that charge modulation is effective and beneficial for dopamine detection. This work may pave the way for biosensors that take advantage of the excellent tunability of atomically layered heterostructures.