Graphene–hemin hybrid nanosheets as a label-free colorimetric platform for DNA and small molecule assays

Here we report a novel label-free colorimetric biosensing strategy based on graphene–hemin hybrid nanosheets (GHs) for DNA and small molecule assays. GHs were synthesized by a simple wet-chemical method and they possess excellent properties from both graphene and hemin. When mixed with ssDNA, GHs exhibited enhanced catalytic activity in the presence of ABTS and H2O2. In contrast, the GHs mixed with dsDNA had lower catalytic activity than those mixed with ssDNA. On the basis of this property of the GHs, a novel universal label-free colorimetric method was proposed. This simple strategy has advantages over conventional assays because of its label-free design, extreme operational simplicity and low cost. DNA and cocaine were studied as model cases and the results revealed that the developed method had potential for becoming a universal platform for detection of a wide range of analytes.