Navigation Links
Measurement technique probes surface structure of gold nanocrystals
Date:3/10/2008

CHAMPAIGN, Ill. In the hands of jewelers, gold can be fashioned into rings and pendants of long-lasting beauty. But, when reduced in size to nanocrystals containing a few thousand atoms, this noble metal is a surprisingly good catalyst.

Finding the key to golds chemical reactivity (or that of any metal nanocrystal) has been difficult, as few measurement techniques work at the nanoscale. Now, researchers at the University of Illinois have demonstrated a sensitive probe that can identify and characterize the atomic structure of gold and other nanocrystalline materials.

Without the necessary structural information, our understanding of nanocrystals has been limited to models that often treat the surface of a nanocrystal as an extension of a bulk crystalline surface, said Jian-Min (Jim) Zuo, a professor of materials science and engineering at the U. of I., and corresponding author of a paper to appear in the April issue of the journal Nature Materials, and posted on its Advanced Online Publication Web site.

The striking difference we found between the surfaces of gold nanocrystals and bulk crystalline surfaces shows we need to re-evaluate our preconceptions about the nature of structural dynamics and the level of complexity that nanocrystals can embrace, said Zuo, who also is a researcher at the Frederick Seitz Materials Research Laboratory on the U. of I. campus.

Because chemical reactions primarily take place on surfaces, scientists need to know how atoms are arranged on those surfaces. While scanning probe microscopy works for flat surfaces of bulk crystals, a different technique is required to study the surfaces of nanocrystals.

In their study, Zuo and colleagues used a technique they developed called nano-area coherent electron diffraction.

The technique works by illuminating a single gold nanocrystal (about 3 nanometers in diameter and containing close to 1,000 atoms) with a coherent electron beam about 40 nanometers in diameter.

The electron beam is scattered by the atoms in the nanocrystal, resulting in a complicated diffraction pattern made of speckles similar to what is seen when a laser beam is reflected by a surface. When deciphered, the diffraction pattern describes the structural arrangement and behavior of the atoms, and the number and lengths of chemical bonds in the nanocrystal.

Chemical force depends upon the number of chemical bonds present, so atoms on the surface, which dont have as many neighbors as those inside a crystal, experience a different force, Zuo said. Our study also shows bond lengths on the surface of a gold nanocrystal are very different from bond lengths inside a bulk crystal.

The differences come as a result of the surface atoms being contracted. The force behind the contraction is attributed to the smoothing of surface electron density and a resulting electrostatic force that pulls the surface ions toward the remaining bonds.

What is surprising, Zuo said, is that the contraction depends on the crystal facets. Atoms on facets with fewer bonds dominate, and lead to a much smaller contraction on other facets. This behavior is markedly different from bulk crystalline surfaces, and represents a new pattern of structural dynamics for nanocrystalline materials.

Characterizing small nanostructures and their surfaces is so essential for understanding the special properties of nanomaterials, Zuo said. Nano-area coherent electron diffraction makes it possible for us to probe the surfaces of individual nanocrystals and examine their structure and size-dependent catalytic activity.


'/>"/>

Contact: James E. Kloeppel
kloeppel@uiuc.edu
217-244-1073
University of Illinois at Urbana-Champaign
Source:Eurekalert

Related medicine news :

1. The Joint Commission Urges Development of a National Performance Measurement Data Strategy
2. AMA Commends Independent Health for Joining Industry Shift on Physician Performance Measurement
3. Brain measurements could lead to better devices to move injured or artificial limbs
4. Biopsy techniques have made PSA test less predictive
5. New stem cell technique improves genetic alteration
6. New technique takes a big step in examination of small structures
7. New steroid test uses oil exploration technique
8. UCF technique promises to aid doctors ability to identify, treat bacterial infections
9. UD researchers discover technique for repairing gene defect that causes spinal muscular atrophy
10. UD researchers discover promising technique for repairing gene that causes spinal muscular atrophy
11. New Technology and Improved Techniques Arm Dermatologists With Tools to Minimize Facial Scars From Skin Cancer Surgery
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:2/5/2016)... ... 05, 2016 , ... Steven Tonkinson, 36, of Coconut Grove, Florida, ran the ... started in 2003. This year, he ran all 26.2 miles with a green 25-pound ... the Miami Heat. , This Sunday, while many are watching the Superbowl, Steven Tonkinson ...
(Date:2/5/2016)... ... February 05, 2016 , ... The event is being held on April ... in Minneapolis, Minn. Triumph Over Parkinson’s will fund nearly $100,000 for research for the ... lives with Parkinson’s disease and is the architect of this informative event to raise ...
(Date:2/5/2016)... ... 05, 2016 , ... After years as an active staff surgeon and having ... surgeon Dr. Wayne Carman transitioned to chief of the Division of Plastic Surgery at ... term as chief and began a second three-year term in January of 2016. , ...
(Date:2/5/2016)... ... February 05, 2016 , ... Regular gym users know ... having to wait longer to access the treadmills. It’s a predictable trend. After the ... lose weight and get in shape by joining gyms, starting new walking or running ...
(Date:2/5/2016)... ... ... Dr. Justin Scott and Dr. Lydia Muccioli of Pure Dental Health ... in need. The event is scheduled to take place on February 27, 2016 from ... dental care to community members in need. Each patient will be given the opportunity ...
Breaking Medicine News(10 mins):
(Date:2/5/2016)... Feb. 5, 2016  ivWatch, a medical devices company, is ... Award granted by Governor Terry McAuliffe,s office. ivWatch ... February 25th at an event to be held at the ... award honors professionals and business that have made significant contributions ... Logo - http://photos.prnewswire.com/prnh/20160205/330117LOGO ...
(Date:2/5/2016)... Feb. 5, 2016  Patients in Alabama ... ultrasound (HIFU) therapy no longer have to travel out of ... partnership with Urology Centers of Alabama to provide ... procedure for qualifying patients. Alabama ... the treatment of prostate cancer using many different modalities. They ...
(Date:2/5/2016)... Feb. 5, 2016 ... of the "Global Musculoskeletal Partnering 2010-2016: ... profile to their offering. --> ... of the "Global Musculoskeletal Partnering 2010-2016: ... profile to their offering. --> ...
Breaking Medicine Technology: