Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Gold shines through properties of nano biosensors

17.08.2017

Researchers discover that fluorescence in ligand-protected gold nanoclusters is an intrinsic property of the gold particles themselves

With their remarkable electrical and optical properties, along with biocompatibility, photostability and chemical stability, gold nanoclusters are gaining a foothold in a number of research areas, particularly in biosensing and biolabeling.


The researchers used Au20, gold nanoparticles with a tetrahedral structure, to show that fluorescence in ligand-protected gold clusters is an intrinsic property of the gold nanoparticles themselves.

Credit: Brune

These gold nanoclusters are chemically protected by ligands, which also steer the binding to biological target molecules. There is still much that researchers don't know about the luminescent properties of ligand-protected gold nanoclusters, including the origin of their fluorescence.

An international research team from Switzerland, Italy, the United States and Germany has now shown that the fluorescence is an intrinsic property of the gold nanoparticles themselves. The researchers used Au20, gold nanoparticles with a tetrahedral structure. Their findings were reported this week in the Journal of Chemical Physics, from AIP Publishing.

"We present the first optical absorption, excitation and fluorescence spectra of bare Au20," said Harald Brune, head of the Institute of Physics at the École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland and corresponding author of the paper. "Our results strongly suggest that the metal core in the ligand-protected clusters used for biosensing and biolabeling is at the origin of their fluorescence."

The researchers created a beam of bare Au20 clusters by combining a cluster aggregation source with a custom-designed ion optic and mass selection process. It is difficult to probe the optical properties of these clusters in the gas phase, given the poor signal-to-noise ratio. To address this issue, the researchers embedded them into a solid neon matrix. This was achieved by depositing the cluster beam with a neon background gas that condensed onto a cold surface held at 6 kelvins (about -267 degrees Celsius) while the clusters were landing there.

Neon, a noble gas, provides a weak interacting medium. As the first-principles calculations accompanying the experiment show, in neon the intrinsic structural and optical cluster properties are preserved.

"Therefore, the presented experimental results are the best possible approximation to the optical properties of free Au20 clusters," Brune said.

The Au20 absorption data was obtained by subtracting an Ne matrix reference spectrum from one of the Au20/Ne matrices. The fluorescence spectra were produced by laser excitation. The researchers found that excitation within the entire UV-to-visible range leads to intense and sharp fluorescence at a wavelength of 739.2 nanometers.

"[B]are Au20 strongly fluoresces, making it very likely that the origin of fluorescence in Au-based biomarkers comes from the Au core itself rather than from its interaction with the organic ligands," said Wolfgang Harbich, senior scientist at the EPFL and co-author of the paper.

The discovery could enable the design of new gold-based biomarkers, and the experiment serves as benchmark for the elaborate, time-dependent density functional theory calculations of optical cluster properties -- a topic gaining interest in fundamental chemistry and physics fields.

"The agreement between experiment and theory in the present case of Au20 is encouraging," Brune said, "and will enable a deeper understanding of theory-supported biomarker research."

###

The article, "Intense fluorescence of Au20," is authored by Chongqi Yu, Wolfgang Harbich, Luca Sementa, Luca Ghiringhelli, Edoardo Aprá, Mauro Stener, Alessandro Fortunelli and Harald Brune. The article appeared in the Journal of Chemical Physics August 15, 2017 [DOI: 10.1063/1.4996687] and can be accessed at http://aip.scitation.org/doi/full/10.1063/1.4996687.

ABOUT THE JOURNAL

The Journal of Chemical Physics publishes concise and definitive reports of significant research in the methods and applications of chemical physics. See http://jcp.aip.org.

Media Contact

Julia Majors
media@aip.org
301-209-3090

 @AIPPhysicsNews

http://www.aip.org 

Julia Majors | EurekAlert!

More articles from Physics and Astronomy:

nachricht Tiny lasers from a gallery of whispers
20.09.2017 | American Institute of Physics

nachricht New quantum phenomena in graphene superlattices
19.09.2017 | Graphene Flagship

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

Im Focus: Quantum Sensors Decipher Magnetic Ordering in a New Semiconducting Material

For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.

Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...

Im Focus: Fast, convenient & standardized: New lab innovation for automated tissue engineering & drug

MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems Holding GmbH about commercial use of a multi-well tissue plate for automated and reliable tissue engineering & drug testing.

MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems...

Im Focus: Silencing bacteria

HZI researchers pave the way for new agents that render hospital pathogens mute

Pathogenic bacteria are becoming resistant to common antibiotics to an ever increasing degree. One of the most difficult germs is Pseudomonas aeruginosa, a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Molecular Force Sensors

20.09.2017 | Life Sciences

Producing electricity during flight

20.09.2017 | Power and Electrical Engineering

Tiny lasers from a gallery of whispers

20.09.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>