Graphene/carbon nanotubes-based biosensors for glucose, cholesterol, and dopamine detection

Sensors, especially those for detecting biomolecules are becoming an essential commodity in the modern world. Biosensors are devices that can convert a biorecognition event into a measurable signal. Electrochemical biosensors are exceptional among the different types of biosensors due to their high sensitivity, selectivity, low cost, ease of use, and possibility of miniaturization compared to other sensors. Nanomaterials based devices are increasingly employed for the electrochemical detection of biomolecules, owing to their miniature size and hence potential for use everywhere. Novel nanomaterials such as nanotubes, nanoparticles, nanowires, nanorods and nanofibers, and nanostructures, including nanogap, interdigitated nanoelectrode array (IDEA), ring-disk nanoelectrode array, and anodic aluminum oxide (AAO) are investigated to improve the sensing characteristics, such as the limit of detection and sensitivity of biosensors for on-field applications. One dimensional Carbon nanotubes (CNTs) are investigated as sensing materials for a decade due to its high surface to volume ratio, better biocompatibility, high electrical conductivity, and electrochemical stability. Two-dimensional graphene, comprising of sp2 bonded carbon atoms arranged in a hexagonal lattice, has gained attention in the last decade in a multitude of applications, owing to its several extraordinary properties such as a large planar surface area (theoretically 2630 m2/g for single-layer graphene), superior elasticity, and mechanical strength, as well as very good electrical and thermal conductivities. Numerous approaches and nanomaterials have been investigated for the fabrication of biosensors. In this section, we have outlined CNT and graphene-based amperometric biosensors for the detection of glucose, cholesterol and dopamine. Compared to the bare electrode, the total surface area of carbon nanomaterials modified electrodes are expected to be higher, and as a result, the sensitivity of detection of biomolecules will be enhanced. A brief summary of the development of glucose, cholesterol, and dopamine biosensors is reviewed, and the mechanism of electrochemical detection and major theoretical/computational studies in the area are presented.