Pentagonal nanorods show catalytic promise

Aug 13, 2014
Pentagonal nanorods show catalytic promise
A transmission electron microscopy image showing the uniformity of the gold–copper pentagonal nanorods. Reproduced, with permission, from Ref. 1 © 2013 Royal Society of Chemistry

Pentagonal nanorods have a unique morphology that confers interesting compositional and shape-dependent properties—including excellent stability and high catalytic activity—that make them excellent candidates for industrial catalysts. Now, researchers in Singapore have developed a simple chemical process to grow uniform pentagonal nanorods composed of gold and copper. These new materials readily catalyze the direct alkylation of an amine with an alcohol, rendering them useful in the fields of materials chemistry and nanotechnology.

"We successfully synthesized gold–copper pentagonal with controlled size and composition by a seed-mediated growth route," explains lead researcher Jackie Ying from the A*STAR Institute of Bioengineering and Nanotechnology. The 'seeds' are multiple crystals of elongated gold decahedrons, joined together by shared faces—an arrangement known as multiply-twinning.

To create the nanorods, the team placed the gold seeds in a solution containing a copper precursor and applied heat—a process that produced nearly uniform pentagonal nanorods (see image).

Ying's team showed that they could control the length of these nanorods by changing the amount of gold seeds added to the copper precursor. Adding a 1:1 ratio of gold to copper produced nanorods that grew approximately 15 nanometers in length while a 1:2 ratio produced nanorods approximately 19 nanometers long, and a 1:3 ratio produced nanorods approximately 24 nanometers long. The diameter of the nanorods remained the same, however, regardless of the ratio of metals used.

The ability to control the size and composition of the nanorods means it is easier to control the properties of the bimetallic gold–copper nanoparticles compared to nanoparticles made of just one metal, Yang explains.

Next, the team evaluated the catalytic activity of these gold–copper nanorods in a carbon–nitrogen-bond-forming reaction—the direct alkylation of an amine using an alcohol. "This hydrogen-borrowing strategy is an attractive synthetic method for the C–N bond formation as it is an environmentally friendly process which produces only water as a byproduct," says Ying.

The nanorods were examined as catalysts for this reaction using the model substrates p-toluene sulphonamide and benzyl alcohol. "Our heterogeneous catalyst showed higher toward the C–N coupling reaction and better recyclability compared to commercially available catalysts," Ying says.

Beyond catalysis, Ying predicts these could be useful in electronics, chemical sensing and even biomedicine. Her team now plans to use the nanorods as seeds themselves to synthesize nanoparticles comprised of a –copper core surrounded by a shell of another material, such as platinum, for energy applications.

Explore further: Mobile phones come alive with the sound of music, thanks to nanogenerators

More information: Yang, J., Chng, L. L., Yang, X., Chen X., Ying, J. Y., Multiply-twinned intermetallic AuCu pentagonal nanorods. Chemical Communications 50, 1141–1143 (2014). dx.doi.org/10.1039/c3cc47254j

Related Stories

Catalysis with Au-tipped CdSe nanorod clusters

May 07, 2014

Clusters of gold (Au)-tipped CdSe nanorods were synthesized by researchers in the Center for Nanoscale Materials Nanophotonics Group through nanorod polymerization driven by the controlled welding of the ...

Recommended for you

Tiny wires could provide a big energy boost

13 hours ago

Wearable electronic devices for health and fitness monitoring are a rapidly growing area of consumer electronics; one of their biggest limitations is the capacity of their tiny batteries to deliver enough ...

Graphene sheets enable ultrasound transmitters

14 hours ago

University of California, Berkeley, physicists have used graphene to build lightweight ultrasonic loudspeakers and microphones, enabling people to mimic bats or dolphins' ability to use sound to communicate ...

Project uses crowd computing to improve water filtration

Jul 06, 2015

Nearly 800 million people worldwide don't have access to safe drinking water, and some 2.5 billion people live in precariously unsanitary conditions, according to the Centers for Disease Control and Prevention. ...

Engineering the world's smallest nanocrystal

Jul 06, 2015

In the natural world, proteins use the process of biomineralization to incorporate metallic elements into tissues, using it to create diverse materials such as seashells, teeth, and bones. However, the way ...

A stretchy mesh heater for sore muscles

Jul 03, 2015

If you suffer from chronic muscle pain a doctor will likely recommend for you to apply heat to the injury. But how do you effectively wrap that heat around a joint? Korean Scientists at the Center for Nanoparticle ...

Polymer mold makes perfect silicon nanostructures

Jul 03, 2015

Using molds to shape things is as old as humanity. In the Bronze Age, the copper-tin alloy was melted and cast into weapons in ceramic molds. Today, injection and extrusion molding shape hot liquids into ...

User comments : 0

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.