Highlights of our Work

2018 | 2017 | 2016 | 2015 | 2014 | 2013 | 2012 | 2011 | 2010 | 2009 | 2008 | 2007 | 2006 | 2005 | 2004 | 2003 | 2002 | 2001

Nanotube

image size: 205.5KB
made with VMD
movie ( 394.9KB )

A pendulum swinging back and forth every second due to the law of gravity is a common sight.  By going down to nanometer dimensions new phenomena emerge under different physical laws. According to a recent report, a potassium ion is found to swing back and forth inside a nanoscale tube at a terahertz frequency (a trillion times a second).  Unlike the pendulum, the ion's oscillation is driven by electrostatic interactions with electrons inside the nanotube wall as shown in the figure.  The tube, a carbon nanotube, is composed of a cylindrical hexagonal lattice of carbon atoms; the ion induces through a so-called dielectric response charges in the nanotube wall that interact back with the ion.  This dielectric response of the nanotube electrons, ordinarily, can be described only through time-consuming calculations, but based on previous work (see Jan 2005 highlight) the response can now be calculated very quickly, in effect,  on-the-fly along with the ion motion. The calculations revealed that carbon nanotubes attract ions into their inside and make them oscillate at Terahertz frequency. The Terahertz oscillator may serve as a detector in future imaging devices. (See also our  nanotube website).