Featured Research

from universities, journals, and other organizations

Using Packed Silver Nanowires As Sensitive Explosives Detector

Date:
September 15, 2003
Source:
University Of California, Berkeley
Summary:
Minuscule wires a few nanometers across are proving to be versatile electronic components, as demonstrated recently by University of California, Berkeley, chemists who used silver nanowires as key elements of a sensitive explosives detector.

Minuscule wires a few nanometers across are proving to be versatile electronic components, as demonstrated recently by University of California, Berkeley, chemists who used silver nanowires as key elements of a sensitive explosives detector.

The researchers, led by Peidong Yang, ChevronTexaco assistant professor of chemistry at UC Berkeley and a chemist with the Materials Sciences Division of Lawrence Berkeley National Laboratory, made about a trillion silver nanowires - essentially nanocopic needles - and packed them tightly together in a thin layer, all needles pointing in the same direction, like rafted logs on a river.

The layer of ordered nanowires made an ideal site for chemicals to bind for detection by a very sensitive technique called surface-enhanced Raman spectroscopy.

This nanowire-based sensing scheme could have "significant implications in chemical and biological warfare detection, national and global security, as well as medical detection applications," Yang and UC Berkeley colleagues report in a paper that appears in the Sept. 10 issue of Nano Letters, a publication of the American Chemical Society.

"Raman spectroscopy is an extremely sensitive and specific technique that basically gives you a chemical signature, a fingerprint," Yang said. "A monolayer of silver nanowires makes a very sensitive substrate on which to detect molecules like DNT (dinitrotoluene, a cousin to TNT), which is used in making essentially all explosives, including land mines. Those explosives have DNT vapor coming out, allowing us to do airborne detection."

Yang said that the packed silver nanowires are a better surface for enhanced Raman spectroscopy than a thin layer of silver because the nanowire surface is more ordered and gives a more clearly defined signal, making interpretation of the Raman vibrational spectrum easier. The packed silver nanowires are uniform, reproducible and suitable for use in air or in liquid.

He is hoping to miniaturize the laser and other components required by Raman spectroscopy to create a microscopic sensor on a chip, allowing very sensitive and specific detection of chemicals like explosives.

Yang's co-authors include Lawrence Berkeley National Laboratory post-doctoral chemist Christian Hess and UC Berkeley graduate students Andrea Tao and Franklin Kim. Other collaborators are graduate students Joshua Goldberger and Rongrui He of UC Berkeley's Department of Chemistry, and chemists Yugang Sun and Younan Xia of the University of Washington, Seattle.

The nanowire layers have other potential uses, too. Yang said that the monolayers can be transferred to any surface, including silicon, glass or flexible plastic polymers, to provide a large area on which to do chemistry. He and his team were able to make flexible sheets of packed nanowires more than three square inches in area (20 square centimeters).

"You could fabricate these in large areas, providing a flexible monolayer that would be a key component in a number of devices, such as flexible solar cells and light emitting diodes" Yang said.

His lab has created similar flexible layers of packed semiconducting nanowires made of silicon that would also be useful in flexible electronic devices. A group at Harvard University reports a similar development with silicon nanowires in the same issue of Nano Letters.

"These are probably the first two examples of techniques that can do large scale assembly of nanostructures, enabling macroscopic manipulation of lots of them simultaneously," said Yang. "You need this ability to manipulate nanowires or nanotubes if they are to become practical electronic components."

Two years ago Yang proved that optical materials like zinc oxide can form nanowires that act as lasers, and he has succeeded in mating nanowires of different materials to create one-dimensional junctions akin to transistor junctions.

This latest triumph employed a technique whereby nanowires are floated on top of a liquid and then compressed to make the nanowires align and clump together tightly. This old technique, called Langmuir-Blodgett assembly, succeeded in creating monolayers measuring 20 square centimeters in area, which Yang could slip onto a flexible surface such as a plastic polymer. Each silver nanowire is about 50 nanometers across - about the diameter of the polio virus - and 2-3 microns long, with a pentagonal cross section and pyramidal tip.

Monolayers can be layered into stacks of alternating semiconductor (silicon) and conductor (silver) to produce other types of devices, he said.

"With monolayers of metal and monolayers of semiconductor, we can do multilayer transfers and stack up these flexible devices to make flexible composites," he said. "The large-scale assembly process we developed to assemble nanowires over a large area will have a significant impact in the nanoscience/technology field."

The work is funded by the Camille and Henry Dreyfus Foundation, ACS-Petroleum Research Fund, Alfred P. Sloan Foundation, Beckman Foundation, David and Lucile Packard Foundation, U.S. Department of Energy, National Science Foundation and Multidisciplinary University Research Initiative of the Air Force Office of Scientific Research (AFOSR-MURI).


Story Source:

The above story is based on materials provided by University Of California, Berkeley. Note: Materials may be edited for content and length.


Cite This Page:

University Of California, Berkeley. "Using Packed Silver Nanowires As Sensitive Explosives Detector." ScienceDaily. ScienceDaily, 15 September 2003. <www.sciencedaily.com/releases/2003/09/030915074129.htm>.
University Of California, Berkeley. (2003, September 15). Using Packed Silver Nanowires As Sensitive Explosives Detector. ScienceDaily. Retrieved July 31, 2014 from www.sciencedaily.com/releases/2003/09/030915074129.htm
University Of California, Berkeley. "Using Packed Silver Nanowires As Sensitive Explosives Detector." ScienceDaily. www.sciencedaily.com/releases/2003/09/030915074129.htm (accessed July 31, 2014).

Share This




More Matter & Energy News

Thursday, July 31, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Britain Testing Driverless Cars on Roadways

Britain Testing Driverless Cars on Roadways

AP (July 30, 2014) British officials said on Wednesday that driverless cars will be tested on roads in as many as three cities in a trial program set to begin in January. Officials said the tests will last up to three years. (July 30) Video provided by AP
Powered by NewsLook.com
7 Ways to Use Toothpaste: Howdini Hacks

7 Ways to Use Toothpaste: Howdini Hacks

Howdini (July 30, 2014) Fresh breath and clean teeth are great, but have you ever thought, "my toothpaste could be doing more". Well, it can! Lots of things! Howdini has 7 new uses for this household staple. Video provided by Howdini
Powered by NewsLook.com
Amid Drought, UCLA Sees Only Water

Amid Drought, UCLA Sees Only Water

AP (July 30, 2014) A ruptured 93-year-old water main left the UCLA campus awash in 8 million gallons of water in the middle of California's worst drought in decades. (July 30) Video provided by AP
Powered by NewsLook.com
Smartphone Powered Paper Plane Debuts at Airshow

Smartphone Powered Paper Plane Debuts at Airshow

AP (July 30, 2014) Smartphone powered paper airplane that was popular on crowdfunding website KickStarter makes its debut at Wisconsin airshow (July 30) Video provided by AP
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