SCI: Nanoparticle trap achieved

Max More (
Fri, 29 Aug 1997 10:18:14 -0700

The American Institute of Physics Bulletin of Physics News
Number 333 August 26, 1997 by Phillip F. Schewe and Ben

ELECTRODES has been controllably achieved for the first time,
enabling researchers to deposit individual nanoparticles onto
surfaces and offering possibilities such as single-nanoparticle
switches. Researchers (Cees Dekker, Delft University of
Technology, construct a circuit
containing two platinum electrodes separated by as little as 4
nm--a gap that the researchers believe to be a world record. To
trap nm-scale molecules or clusters, they immerse the electrodes
in a solution containing the nanoparticles. Applying a voltage to
the electrodes polarizes each particle and attracts a particle to the
gap between the electrodes. Once a particle bridges the gap,
current flows through the circuit, and a resistor then sharply
reduces the electric field, discouraging any additional
nanoparticles from entering the gap. In principle, this
electrostatic-trapping technique can work for any polarizable
nanoparticle; it has been demonstrated for nanometer-scale
clusters of palladium (Pd) atoms, carbon nanotubes, and a 5
nm-long chain of thiophene (a conducting polymer). The
researchers have also studied the properties of single electrons as
they cross a Pd nanocluster between the electrodes. (A.
Bezryadin et al., Applied Physics Letters, 1 September; images at