Featured Research

from universities, journals, and other organizations

New structural information on functionalization of gold nanoparticles

Date:
August 2, 2012
Source:
Suomen Akatemia (Academy of Finland)
Summary:
Nanometer-scale gold particles are currently intensively investigated for possible applications as catalysts, sensors, biolabels, drug delivery devices, biological contrast agents and as components in photonics and molecular electronics. Researchers now report the first structural study on the atomistic processes of a ligand-exchange reaction of a well-defined gold nanoparticle that has 102 gold atoms and 44 ligand sites in the molecular overlayer.

Visualization of the atomic structure of the Au102(p-MBA)44 particle (left) and the partially ligand-exchanged Au102(p-MBA)40(p-BBT)4 (right). The exchanged ligand bromo benzene thiol (p-BBT) is schematically shown in the middle and the observed ligand exchange sites by red and blue on the right.
Credit: Image courtesy of Suomen Akatemia (Academy of Finland)

Nanometre-scale gold particles are currently intensively investigated for possible applications as catalysts, sensors, biolabels, drug delivery devices, biological contrast agents and as components in photonics and molecular electronics. The particles are prepared in a solution from gold salts and their reactive gold cores can be stabilized with various organic ligands. Particularly stable particles can be synthesized by using organothiol ligands that have a strong chemical interaction to gold, producing precise compositions in the size range of 1 to 3 nanometres.

Modification of the protecting molecular overlayer is a key step in almost all applications. A detailed structural atomistic understanding of the processes of the exchange reaction has been lacking.

Now, professors Chris Ackerson in the Colorado State University in Ft. Collins, USA, and Hannu Häkkinen at the Nanoscience Center of the University of Jyväskylä, Finland, report the first structural study on the atomistic processes of a ligand-exchange reaction of a well-defined gold nanoparticle that has 102 gold atoms and 44 ligand sites in the molecular overlayer. 

The studied particle has a chemical formula of Au102(p-MBA)44 and it was made by using a water-soluble thiol (para -- mercapto benzoic acid, p-MBA) as the stabilizing molecule. The X-ray crystal structure of this particle was first reported as the cover article of Science in 2007 by the group of Roger D. Kornberg from Stanford University [2]. Häkkinen led an international team of researchers that published a theoretical analysis of this and other thiol-stabilized gold nanoparticles in 2008 in the Proceedings of the National Academy of Sciences [3].

In the new study, Ackerson's group succeeded in making heterogeneous crystals of samples of Au102 particles that had undergone a ligand-exchange reaction where the p-MBA thiols in the molecular overlayer had been partially exchanged to a similar thiol containing a Bromine atom, the so-called para -- bromo benzene thiol (p-BBT), under a fast 5-minute reaction.

The analysis of the heterogeneous crystals showed which ligand sites in the overlayer are the most likely to be changed during the short reaction time, i.e., from which sites the exchange process starts. Surprisingly, only 4 sites out of the 44 possibilities showed occupation by the exchanged ligand (see image). Theoretical analysis performed by Häkkinen's group gave insight into the atomistic details of possible reaction mechanisms. Evidence from experiment and theory indicates that the Au102(p-MBA)44 nanoparticle has a thiol overlayer where almost every thiol ligand site has its own reaction rate due to a highly heterogeneous structure of the overlayer. "The Au102(p-MBA)44 nanoparticle has a structure reminiscent of a protein, with a rigid inorganic gold core analogous to the alpha-carbon backbone of a protein core and chemically modifiable functional groups in the low-symmetry molecular overlayer," says prof. Ackerson. "When ligand exchange reactions are better understood, we hope to fully control the surface functionalization of the Au102 and similar water-soluble gold nanoparticles. The implications in biology for a fully controllable synthetic surface the size of a protein are profound," says prof. Häkkinen.

The study was published in the Journal of the American Chemical Society. Prof. Häkkinen's work is funded by the Academy of Finland and prof. Ackerson's work is funded by the Colorado State University and the American Federation for Aging Research. The other researchers involved in the work are Christine Heinecke, Thomas Ni and Andrea Wong from Ft. Collins and Sami Malola and Ville Mäkinen from Jyväskylä. The massively parallel computations needed for interpretation of the experimental observations were made in the Louhi supercomputer at CSC -- the Finnish IT Center for Science in Espoo.


Story Source:

The above story is based on materials provided by Suomen Akatemia (Academy of Finland). Note: Materials may be edited for content and length.


Journal References:

  1. Christine L Heinecke, Thomas W. Ni, Sami A. Malola, Ville P. Mäkinen, O. Andrea Wong, Hannu J. Häkkinen, Christopher J. Ackerson. Structural and Theoretical Basis for Ligand Exchange on Thiolate Monolayer Protected Gold Nanoclusters. Journal of the American Chemical Society, 2012; 120721120602007 DOI: 10.1021/ja3032339
  2. P. D. Jadzinsky, G. Calero, C. J. Ackerson, D. A. Bushnell, R. D. Kornberg. Structure of a Thiol Monolayer-Protected Gold Nanoparticle at 1.1 A Resolution. Science, 2007; 318 (5849): 430 DOI: 10.1126/science.1148624
  3. M. Walter, J. Akola, O. Lopez-Acevedo, P. D. Jadzinsky, G. Calero, C. J. Ackerson, R. L. Whetten, H. Gronbeck, H. Hakkinen. A unified view of ligand-protected gold clusters as superatom complexes. Proceedings of the National Academy of Sciences, 2008; 105 (27): 9157 DOI: 10.1073/pnas.0801001105

Cite This Page:

Suomen Akatemia (Academy of Finland). "New structural information on functionalization of gold nanoparticles." ScienceDaily. ScienceDaily, 2 August 2012. <www.sciencedaily.com/releases/2012/08/120802073113.htm>.
Suomen Akatemia (Academy of Finland). (2012, August 2). New structural information on functionalization of gold nanoparticles. ScienceDaily. Retrieved July 31, 2014 from www.sciencedaily.com/releases/2012/08/120802073113.htm
Suomen Akatemia (Academy of Finland). "New structural information on functionalization of gold nanoparticles." ScienceDaily. www.sciencedaily.com/releases/2012/08/120802073113.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