Fabrication of Graphene and Molybdenum Disulfide Electrodes and Their Biosensor Applications

Abstract

Biosensors have received substantial attentions in analytical chemistry owing to their potential for a wide range of applications. Compared to various sensing methods, electrochemical sensing method is a very attractive and powerful tool for high-performance biosensors. Electrochemical biosensors recognize a measurable electrical signal through a transducer, leading to high sensitivity, low power consumption, simple instrumentation, and short analysis time. Among electrochemical biosensors, field-effect transistor (FET)-based sensors are promising candidates because of their ability to rapidly and sensitively detect analytes via efficient interfacial transfer of charge carriers. Transducers play a crucial role in improving the performance of FET sensors. From a material viewpoint, the characteristics of transducer materials significantly affect the sensing performance. Therefore, it is important to develop and utilize enhanced transducer materials for FET-type biosensors. This dissertation describes CVD graphene and MoS2 as transducers for biosensor applications. Graphene, two-dimensinal (2D) structures with hexagonal lattice, comprises single- or few- layer of sp2-hybridized carbon atoms. Graphene has grabbed considerable focus owing to its outstanding thermal, mechanical, and electrical properties. Transition metal dichalcogenides (TMDs) are graphene-like 2D layered materials. Molybdenum disulfide (MoS2), which is a layered TMD, features high carrier mobility and low noise level. From these attractive properties, three different nanostructures based on graphene and MoS2 were used as transducers for biosensors. First, graphene was prepared via chemical vapor deposition (CVD) process. CVD graphene was applied to HBsAg and taste sensors. Second, the flower-like MoS2 nanospheres were fabricated using a simple hydrothermal method. After vapor deposition polymerization (VDP), carboxylated polypyrrole-coated nanospheres showed improved performance in As(III) sensor. Lastly, MoS2 nanosheets were grown on graphene surface by hydrothermal process. The nanocomposite was applied to a highly sensitive nonenzymatic sensor for H2O2 detection. These transducer materials can provide enhanced sensing performance with high sensitivity, good selectivity, and rapid response for various sensor applications.