Graphene based field-effect transistor biosensors functionalized using gas-phase synthesized gold nanoparticles

Research has focused on graphene for developing the next generation of label-free biosensors, capable of highly sensitive and specific detection of DNA or other biomolecules. The binding of charged analytes to the one-atom thick layer of graphene can greatly affect its electronic properties. However, graphene is highly chemically inert, thus surface functionalization through chemical treatment is typically necessary to immobilize receptors of the target biological analyte on the graphene. In this work, we use gas-phase synthesized gold nanoparticles (Au NPs) to functionalize and bind a DNA aptamer to the graphene surface. The graphene is employed in a liquid gated field-effect transistor (FET) configuration to detect the hybridization of the complementary DNA strand, as well as the protein streptavidin, at attomolar level (aM, 10(-18) mol L-1). The sensor shows a high dynamic detecting range from aM to picomolar (pM) levels (10(-18) to 10(-12) mol L-1), can discriminate between a complementary strand and a single nucleotide polymorphism (SNP) containing strand, and achieves a detection limit as low as 15 aM. The high detection limit suggests that decorating biosensors with Au NPs synthesized from magnetron sputtering inert gas condensing technique is a promising method for biosensor functionalization, particularly for larger-area sensors that employ two-dimensional materials such as graphene.