Metamaterials are a fascinating subject, worthy of a blog post at some point (to be written in my copious spare time, of course). If a real material won’t do what you need, you design one. Instead of atoms, you place small dots (known as quantum dots or nanodots) containing semiconducting or metallic atoms in a lattice pattern, making a two-dimensional solid with special electronic properties. A recent paper described the fabrication of a metamaterial built from gold nanodots, which has very precise response to light: when photons of a specific wavelength strike the surface at a given angle, almost nothing gets reflected back, whereas shifting the angle or wavelength slightly produces measurable reflection. The researchers used this metamaterial to make a sensitive molecular sensor, one capable of sniffing out individual proteins.

V. G. Kravets and colleagues demonstrated the detection of tiny masses, on the order of a single biomolecule, using nanoscale optics. They fabricated a material that responded resonantly to light. When a tiny amount of mass was added to the surface, it caused a dramatic change in the amount of reflected light. This enabled the researchers to detect the presence of mass accumulation to the level of 10-15 grams over a millimeter patch—equivalent to detecting a single human skin cell landing on a coffee table. [Read more...]

Foreign contaminant! Detection on molecular level using gold nanodots