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Mind the (Nano) Gap

How nanotechnology opens up new routes for biosensing and healthcare

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Nanopores are tiny holes with diameters of only tens of nanometres. These holes can be made in glass, very thin materials like graphene, or even DNA origami. As different biological molecules pass through the nanopore, they each partially block the pore in characteristic ways. This allows us to “see” the size and shape of molecules as they pass through the nanopore even though both the pore and the molecules are too small to see with a normal microscope! One way that these nanopores could be used is for sensing different proteins and DNA as a medical diagnostic sensor.

We can find diseases using sensors made out of a material called graphene. Graphene is made from graphite, as found in pencil leads. We use graphene because it’s incredibly thin – a sheet of graphene is made from a single layer of carbon atoms. The thin graphene surface is extremely sensitive to anything touching it, like a very thin and delicate membrane.  We can add antibodies to the graphene which stick to the antigens. Every antigen has a unique antibody that it can bind to – they fit together like a key in a lock. nanogap2
nanogap3 Plasmons are collective oscillations of the electrons which are caused by shining light on metal surfaces. The oscillating electromagnetic field of light pushes and pulls on the electrons inside conductive materials like gold. These oscillating electrons create very intense, local electromagnetic fields. By shining light on two gold nanoparticles separated by a single nanometre, we strongly confine the electromagnetic field to the nanoscale between the nanoparticles. This extremely intense light in the nano-gap vigorously shakes the bonds of molecules causing them to emit different colours.  This allows us to see the molecules inside the nano-gap.

 

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