Size matters when reducing NiO nanoparticles

November 27, 2012 by Matt Shipman
The number and location of nucleation sites of nickel metal within nickel oxide nanoparticles during their reduction with hydrogen strongly depend on the nanoparticle size.

(—New research finds that size plays a major role in how nanoscale nickel oxide (NiO) shells behave when being reduced to solid nickel nanoparticles.

"This advances our fundamental understanding of how the structures of nanoparticles can be changed through , which has potential applications in and ," says Joe Tracy, a materials scientist at NC State and co-author of a paper on the work.

The researchers began by exposing nickel nanoparticles to air at 500 degrees Celsius in order to create NiO shells. This process is called oxidation. The smaller shells, 12 to 24 (nm) in diameter, are hollow, with the shell surrounding a single cavity. Larger shells, 40 to 96 nm in diameter, appear to have larger pores, and possibly contain multiple cavities.

The researchers then placed the shells in a environment at 350 degrees C. This process, called reduction, turns the NiO shells back into solid nickel nanoparticles.

What they found was that the size of the NiO shells dramatically affects the way that the reduction process manifests itself.

Image of a partially reduced 40 nm nickel oxide nanoparticle. The nickel region is colored red, and the nickel oxide is colored green. Click to enlarge image.

The smallest shells the researchers looked at, 12 nm in diameter, formed a single nucleation site of pure nickel, which then expanded to replace all of the NiO. Larger shells, 24 nm in diameter, responded differently – forming multiple nucleation sites in an approximate ring shape around the shell. These nucleation sites then grew and merged into a single nickel nanoparticle. The largest shells they looked at, 96 nm in diameter, looked more different still, with multiple nucleation sites forming throughout the NiO.

"The size of the nanoparticles before oxidation determines both the structure of the NiO nanoparticles and the pattern of the nucleation sites of nickel metal during reduction," says John Medford, an undergrad at NC State and lead author of the paper.

The paper, "Nanostructural Transformations During the Reduction of Hollow and Porous Nanoparticles," was published online Nov. 20 in the Royal Society of Chemistry journal Nanoscale.

Explore further: Study shows that size affects structure of hollow nanoparticles

More information:

Related Stories

Recommended for you

Nano-decoy lures human influenza A virus to its doom

October 25, 2016

To infect its victims, influenza A heads for the lungs, where it latches onto sialic acid on the surface of cells. So researchers created the perfect decoy: A carefully constructed spherical nanoparticle coated in sialic ...

New method increases energy density in lithium batteries

October 24, 2016

Yuan Yang, assistant professor of materials science and engineering at Columbia Engineering, has developed a new method to increase the energy density of lithium (Li-ion) batteries. He has built a trilayer structure that ...

Nanofiber coating prevents infections of prosthetic joints

October 24, 2016

In a proof-of-concept study with mice, scientists at The Johns Hopkins University show that a novel coating they made with antibiotic-releasing nanofibers has the potential to better prevent at least some serious bacterial ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.