Due to the unique physical and chemistry properties, graphene has been viewed as a promising material for fabricating chemical and biological sensors with high sensitivity, chemical stability, and biocompatibility. Solution-gated graphene transistors (SGGT), in which the gate voltage applied on the graphene channel through an electrolyte instead of gate insulator, have been widely studied for detection of biological relevant analytes because the related reactions require aqueous environment.
Whole-graphene solution-gated transistors are designed and realized as high sensitive dopamine sensors. Graphene serve as both the channel and the gate eletrode in the transistor, which provide the possibility for high density integration. Different from previous SGGT-based dopamine sensors, the sensing mechanism is based on the change of effective gate voltage applied on the transistors induced by the electro-oxidation of dopamine at the graphene gate electrodes. The device show high sensitivity with the limit of detection (LOD) of dopamine as low as 1 nM, which is three orders of magnitude lower than conventional electrochemical methods. The interference from glucose, uric acid (UA) and ascorbic acid (AA) on the dopamine sensor is characterized. In order to improve the selectivity of the dopamine sensor, the gate electrode is modified with a biocompatible Nafion film. After the modification, the detection limit of the device to dopamine, uric acid, and ascorbic acid are 1nM, 10 uM and 1 uM respectively, exhibiting excellent selectivity to dopamine.
In conclusion, whole-graphene SGGT-based dopamine sensor with high sensitivity and selectivity was fabricated. The mechanism of functionalizing the gate electrodes for specific detection could be used for developing many other types of biosensors. Therefore the SGGTs have great potential for the applications as low-cost, high density and multifunctional biosensors in future.