No small measure: Origins of nanorod diameter discovered

Mar 19, 2009

(PhysOrg.com) -- A new study answers a key question at the very heart of nanotechnology: Why are nanorods so small?

Researchers at Rensselaer Polytechnic Institute have discovered the origins of nanorod , demonstrating that the competition and collaboration among various mechanisms of atomic transport hold the key to nanorod size. The researchers say it is the first study to identify the fundamental reasons why nearly all have a diameter on the order of 100 nanometers.

"Scientists have been fabricating nanorods for decades, but no one has ever answered the question, 'Why is that possible?'" said Hanchen Huang, professor in Rensselaer's Department of Mechanical, Aerospace, and Nuclear Engineering, who led the study. "We have used computer modeling to identify, for the first time, the fundamental reasons behind nanorod diameter. With this new understanding, we should be able to better control nanorods, and therefore design better devices."

Results of the study, titled "A scale of nanorods diameter during growth," were recently published in the journal .

When fabricating nanorods, are released at an oblique angle onto a surface, and the atoms accumulate and grow into nanorods about 100 nanometers in diameter. A nanometer is one billionth of a meter in length.

The accumulating atoms form small layers. After being deposited onto a layer, it takes varying amounts of energy for atoms to travel or "step" downward to a lower layer, depending on the step height. In a previous study, Huang and colleagues calculated and identified these precise energy requirements. As a result, the researchers discovered the fundamental reason nanorods grow tall: as atoms are unable to step down to the next lowest layer, they begin to stack up and grow higher.

It is the cooperation and competition of atoms in this process of multi-layer that accounts for the fundamental diameter of nanorods, Huang shows in the new study. The rate at which atoms are being deposited onto the surface, as well as the temperature of the surface, also factor into the equation.

"Surface steps are effective in slowing down the mass transport of surface atoms, and aggregated surface steps are even more effective," Huang said. "This extra effectiveness makes the diameter of nanorods around 100 nanometers; without it the diameter would go up to 10 microns."

Beyond advancing scientific theory, Huang said the discovery could have implications for developing photonic materials and fuel cell catalysts.

More information: link.aps.org/doi/10.1103/PhysRevLett.101.266102

Source: Rensselaer Polytechnic Institute

Explore further: Imaging electric charge propagating along microbial nanowires

add to favorites email to friend print save as pdf

Related Stories

Purifying nanorods: Big success with tiny cleanup

Sep 22, 2008

Chemists at Rice University have discovered a novel method to produce ultra-pure gold nanorods -- tiny, wand-like nanoparticles that are being studied in dozens of labs worldwide for applications as broad as diagnosing disease ...

Engineering new uses for gold

Aug 22, 2008

The glitter of gold may hold more than just beauty, or so says a team of MIT researchers that is working on ways to use tiny gold rods to fight cancer, deliver drugs and more.

Gold nanorods shed light on new approach to fighting cancer

Oct 16, 2007

Researchers have shown how tiny "nanorods" of gold can be triggered by a laser beam to blast holes in the membranes of tumor cells, setting in motion a complex biochemical mechanism that leads to a tumor cell's self-destruction.

Recommended for you

Researchers develop world's thinnest electric generator

Oct 15, 2014

Researchers from Columbia Engineering and the Georgia Institute of Technology report today that they have made the first experimental observation of piezoelectricity and the piezotronic effect in an atomically ...

User comments : 0