Featured Research

from universities, journals, and other organizations

Engineers love triangles: Shaped catalysts spark longer, faster-growing, rule-breaking nanowires

Date:
June 6, 2012
Source:
Case Western Reserve University
Summary:
Engineers have found that gold catalysts shaped in the form of a cube, triangle, or other higher order structures grow nanowires about twice as fast and twice as long compared to wires grown with the more typical spherically-shaped catalysts. The wires, as small as one-5,000th the width of a human hair, could be used to build the next generation of "invisible" computer chips or sensors fast enough to identify signs of disease.

A research team at Case Western Reserve University has found that gold catalysts shaped in the form of a cube, triangle, or other higher order structures grow nanowires about twice as fast and twice as long compared to wires grown with the more typical spherically-shaped catalysts.

This finding could prove useful to other scientists who are growing nanowires to build sensors fast enough to detect changes in red and white blood cells. These sensors in turn could help identify various forms of cancer in the body. The wires are so small -- as small as one-5,000th the width of a human hair -- they could also be used to build the next generation of "invisible" computer chips.

Xuan Gao, assistant professor of physics, and R. Mohan Sankaran, associate professor of chemical engineering, describe their work in the paper, "Shape-Controlled Au Particles for InAs Nanowire Growth," published in the journal Nano Letters.

Their research team included Case Western Reserve graduate students Pin Ann Lin and Dong Liang and Hathaway Brown Upper School student Samantha Reeves.

The researchers tested growth using both the preferentially-shaped and spherical catalysts under identical conditions to rule out error in the comparisons.

They suggest that the long accepted model of vapor-liquid-solid, or VLS, growth is incomplete, and that more tests are needed in order to fully understand the process.

Here's why: the researchers found that that the nanowires grown with the triangular catalyst have a much thicker layer of the metal Indium than the VLS nanowire growth model predicts.

The finding suggests a correlation between Indium concentration and growth enhancement. The team made the discovery when they beamed electrons at the nanowires to release high energy x-rays, a process called energy-dispersive X-ray spectroscopy. The magnitude of these energy bursts were used to determine chemical properties of the nanowires.

To grow nanowires, the researchers combined elements such as indium and arsenic, from rows 4 and 5 of the periodic table of elements. Elements from these rows bond to the gold particle to create a semiconductor that neither allows great flow of electric current nor greatly prevents its flow. This is called the "bottom-up method" which Gao describes as truly like "growing a plant from a seed."

Nanowires can also be made "top-down" with precise cuts on a large piece of semiconducting material, reducing it to a tiny structure of wires.

The disadvantage to this, Sankaran explains, is that cutting wires smaller than around 45 nm, which is the current standard in computer chips, "is impossible if we are using a machine. But if we were to grow the wires from chemical compounds we could make them as small as 10 nm, meaning we could fit more wires in a smaller space for greater speed."

However the bottom-up method only produces wires in bunches as opposed to the large interwoven structures made from the top-down method of cutting. The challenge is combining chemically-grown wires in ways that they work in complex electronics such as computer chips or highly-sensitive sensors.

Both Gao and Sankaran describe their research efforts as truly collaborative. Sankaran makes catalysts of different shapes to grow the nanowires, and Gao tests the properties of these wires and connects them to possible uses in the field.

This duo plans to continue exploring the correlation between catalyst shape and other structural characteristics of the wires in order to further develop the VLS model, and move closer to implementing nanowires in new technology.


Story Source:

The above story is based on materials provided by Case Western Reserve University. The original article was written by Sean Linden. Note: Materials may be edited for content and length.


Journal Reference:

  1. Pin Ann Lin, Dong Liang, Samantha Reeves, Xuan P.A. Gao, R. Mohan Sankaran. Shape-Controlled Au Particles for InAs Nanowire Growth. Nano Letters, 2012; 12 (1): 315 DOI: 10.1021/nl2036035

Cite This Page:

Case Western Reserve University. "Engineers love triangles: Shaped catalysts spark longer, faster-growing, rule-breaking nanowires." ScienceDaily. ScienceDaily, 6 June 2012. <www.sciencedaily.com/releases/2012/06/120606102706.htm>.
Case Western Reserve University. (2012, June 6). Engineers love triangles: Shaped catalysts spark longer, faster-growing, rule-breaking nanowires. ScienceDaily. Retrieved April 24, 2014 from www.sciencedaily.com/releases/2012/06/120606102706.htm
Case Western Reserve University. "Engineers love triangles: Shaped catalysts spark longer, faster-growing, rule-breaking nanowires." ScienceDaily. www.sciencedaily.com/releases/2012/06/120606102706.htm (accessed April 24, 2014).

Share This



More Matter & Energy News

Thursday, April 24, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

UN Joint Mission Starts Removing Landmines in Cyprus

UN Joint Mission Starts Removing Landmines in Cyprus

AFP (Apr. 23, 2014) The UN mission in Cyprus (UNFICYP) led a mine clearance demonstration on Wednesday in the UN-controlled buffer zone where demining operations are being conducted near the Cypriot village of Mammari. Duration: 01:00 Video provided by AFP
Powered by NewsLook.com
Air Force: $4.2B Saved from Grounding A-10s

Air Force: $4.2B Saved from Grounding A-10s

AP (Apr. 23, 2014) Speaking about the future of the United States Air Force, Chief of Staff Gen. Mark Welsh says the choice to divest the A-10 fleet was logical and least impactful. (April 23) Video provided by AP
Powered by NewsLook.com
Jets Fuel Jump in Boeing's Revenue

Jets Fuel Jump in Boeing's Revenue

Reuters - Business Video Online (Apr. 23, 2014) A sharp rise in revenue for commercial jets offset a decline in Boeing's defense business. And a big increase in deliveries lifted profitability. Fred Katayama reports. Video provided by Reuters
Powered by NewsLook.com
Is North Korea Planning Nuclear Test #4?

Is North Korea Planning Nuclear Test #4?

Newsy (Apr. 22, 2014) South Korean officials say North Korea is preparing to conduct another nuclear test, but is Pyongyang just bluffing this time? Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins