Weighing a single atom using a coupled plasmon-carbon nanotube system.

We propose an optical weighing technique with a sensitivity down to a single atom, using a surface plasmon and a doubly clamped carbon nanotube resonator. The mass of a single atom is determined via the vibrational frequency shift of the carbon nanotube while the atom attaches to the nanotube surface. Owing to the ultralight mass and high quality factor of the carbon nanotube, and the spectral enhancement by the use of surface plasmon, this method results in a narrow linewidth (kHz) and high sensitivity (2.3×10-28 Hz· g-1), which is five orders of magnitude more sensitive than traditional electrical mass detection techniques.