Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Researchers demonstrate single molecule absorption spectroscopy

21.12.2005


A powerful new tool for probing molecular structure on surfaces has been developed by researchers at the University of Illinois at Urbana-Champaign. Single molecule absorption spectroscopy can enhance molecular analysis, surface manipulation and studies of molecular energy and reactivity at the atomic level.



"This new measurement method combines the chemical selectivity of optical absorption spectroscopy with the atomic-scale resolution of scanning tunneling microscopy," said Martin Gruebele, a professor of chemistry, physics and biophysics and corresponding author of a paper accepted for publication in the journal Nano Letters, and posted on its Web site. "The method literally feels how a molecule changes shape when it absorbs energy."

Unlike single molecule fluorescence spectroscopy, which is now a commonly used measurement technique, single molecule absorption spectroscopy has been an elusive goal.


"Single molecules don’t absorb much light, making detection difficult to begin with," said Gruebele, who also is a researcher at the university’s Beckman Institute for Advanced Science and Technology. "An even bigger problem, however, is that light-induced heating in the sample and in the microscope tip can produce so much noise that the signal is lost."

To reduce the noise, the researchers combined several special techniques -- each insufficient by itself -- into a method that allows them to detect single molecule absorption under laser illumination by scanning tunneling microscopy.

"First, the sample molecule is placed on a transparent silicon substrate," said Joseph Lyding, a professor of electrical and computer engineering and a researcher at the Beckman Institute. "Laser light will either be absorbed by the sample or will pass through the substrate with little or no heating effect. Second, the tip-sample junction is illuminated through the rear face of the substrate, significantly reducing tip heating."

Modulating the laser light with a mechanical chopper further reduces heating, Lyding said. A lock-in amplifier, which switches on and off at the same rate as the laser, filters out mechanical and electronic noise. As a result, the absorbed energy causes a change of shape in the electron density of the sample molecule, and the scanning tunneling microscope then measures that change of shape.

"Single molecule absorption spectroscopy is an extremely sensitive technique for analytical chemistry, for measuring electrical properties of molecules, and for studying energy transfer on surfaces," Gruebele said. "While most molecules don’t fluoresce -- limiting the usefulness of single molecule fluorescence spectroscopy -- all molecules absorb, making single molecule absorption spectroscopy a much more general approach."

James E. Kloeppel | EurekAlert!
Further information:
http://www.uiuc.edu

More articles from Physics and Astronomy:

nachricht DGIST develops 20 times faster biosensor
24.04.2017 | DGIST (Daegu Gyeongbuk Institute of Science and Technology)

nachricht New quantum liquid crystals may play role in future of computers
21.04.2017 | California Institute of Technology

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: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

DGIST develops 20 times faster biosensor

24.04.2017 | Physics and Astronomy

Nanoimprinted hyperlens array: Paving the way for practical super-resolution imaging

24.04.2017 | Materials Sciences

Atomic-level motion may drive bacteria's ability to evade immune system defenses

24.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>