This is simply two layers of graphene. This type of graphene was synthesized by Geim and Novosolev in their first experiments and would fall into the category of Very Few Layers (VFL) graphene.
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Biosensors
A biosensor is an analytical device that can detect a biomolecule-related element with an appropriate transducer to generate a measurable signal from the sample. In general, graphene possesses attractive qualities for sensors and biosensors, such as ultra-high charge mobility, transparency, large surface area, non-toxicity, high-tensile strength and high thermal conductivity to name a few. However, for graphene to maintain these properties, it has to be kept in a pretty pure form.