Single-molecule detection level approached using metamaterials

Ars Technica : A layer of gold nanodots is the basis of a new molecule detection technique that is sensitive enough to detect masses of just 10 ^-15 g in a surface area of just 1 mm ². A team led by V. G. Kravets of the University of Manchester in the UK reached that level of sensitivity by putting a layer of graphene on top of the nanodots. The two layers of lattices allowed the researchers to reflect a very narrow range of photons from the material. The presence of hydrogen atoms attached to the layer of graphene significantly decreased the amount of reflected light. The researchers were able to determine the relationship between the mass of the hydrogen present and the decreased reflectivity. They then created another metamaterial using a layer of carboxylate and biotin (vitamin B ₇) on top of gold nanodots. Biotin binds with a protein that is commonly found in certain bacteria. The researchers measured the reflectivity of the surface before and after exposure to the protein, and determined that they could detect the presence of 1â4 protein molecules on a single nanodot. Detectors with this level of sensitivity could be very useful in medicine, pharmacology, and other areas where chemicals often have modest molecular weights.