Navigation Links
Measurement technique probes surface structure of gold nanocrystals

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
University of Illinois at Urbana-Champaign

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:
(Date:6/25/2016)... ... June 25, 2016 , ... ... issues and applications at AcademyHealth’s Annual Research Meeting June 26-28, 2016, at the ... several important health care topics including advance care planning, healthcare costs and patient ...
(Date:6/25/2016)... Viejo, California (PRWEB) , ... June 25, 2016 , ... ... to fit their specific project," said Christina Austin - CEO of Pixel Film Studios. ... fully customizable and all within Final Cut Pro X . Simply select a ...
(Date:6/25/2016)... City, Oklahoma (PRWEB) , ... June 25, 2016 ... ... helping both athletes and non-athletes recover from injury. Recently, he has implemented orthobiologic ... the Oklahoma City area —Johnson is one of the first doctors to perform ...
(Date:6/24/2016)... Los Angeles, CA (PRWEB) , ... June 24, 2016 , ... ... plastic surgery procedures that most people are unfamiliar with. The article goes on to ... known procedures, but also many of these less common operations such as calf and ...
(Date:6/24/2016)... ... ... a crisis. Her son James, eight, was out of control. Prone to extreme mood shifts ... upset him, he couldn’t control his emotions,” remembers Marcy. “If there was a knife ... and say he was going to kill them. If we were driving on the ...
Breaking Medicine News(10 mins):
(Date:6/23/2016)... , June 23, 2016 , ... on Thursday, July 7, 2016 , , , , LOCATION: ... , , , , EXPERT PANELISTS:  , , , ... Senior Industry Analyst, Christi Bird; Senior Industry Analyst, Divyaa Ravishankar and ... The global pharmaceutical industry is witnessing an exceptional era. ...
(Date:6/23/2016)... BOGOTA, Colombia , June 23, 2016  Astellas today announced the establishment of Astellas Farma Colombia ... the company,s second affiliate in Latin America . ... ... Farma Colombia ... ...
(Date:6/23/2016)... , June 23, 2016  Guerbet announced today ... Inc.,s Supplier Horizon Award . One ... Guerbet was recognized for its support of Premier members ... through clinical excellence, and commitment to lower costs. ... receive this recognition of our outstanding customer service from ...
Breaking Medicine Technology: