Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Molecular nanoprobe for nanoantenna optical near-fields

29.07.2013
Researchers at the University of Stuttgart measure for the first time near-fields of three-dimensional optical nanoantennas.

Researchers at the University of Stuttgart measured for the first time optical near-field intensities of three-dimensional nanoantennas. The team of Prof. Harald Giessen at the 4th Physics Institute achieved those results with a novel scheme of nanospectroscopy and published their paper in the journal “Nature Communications”.*)


Molecules (blue) are positioned with nanometer accuracy next to three-dimensional optical nanoantennas. Vibrations in the molecules are excited. The oscillation strength depends on the near-field distribution (red) and can be measured in the far-field.

(University of Stuttgart)

Their method gives new insight into light-matter coupling at the nanoscale and allows precise measurement of enhanced optical near-field intensities generated by optical antennas. This technique can facilitate the engineering of future sensing platforms with extremely high sensitivity.

Molecules exhibit vibrational resonances in the mid-infrared and terahertz regions which is called the molecular fingerprint since it is unique for each substance. With far-field spectroscopy techniques, molecules can be detected and unambiguously identified. Nevertheless, huge quantities of molecules are needed since the excitation of the vibrational resonances is very inefficient. Metallic optical nanoantennas are resonant to incident radiation and generate high near-fields in their direct vicinity. These intensive fields can be used to make small amounts of molecules or even single molecules visible. This plays an important role in early disease diagnostics and in the detection of harmful substances or explosive gas mixtures, such as hydrogen in air.

The Stuttgart group was able to position a few molecules next to gold nanoantennas. Using electron-beam lithography they achieved an accuracy as small as a few nanometers. Due to the high near-field intensities the excitation of the molecular vibrations was orders of magnitude more efficient and was measurable with far-field spectroscopy techniques. By positioning the molecules at different locations with respect to the optical gold nanoantenna the underlying physical process of the vibrational excitation was identified for the first time. In particular, the team of researchers found that the efficiency of the vibrational excitation scales linearly with the near-field intensity generated by the optical antennas.

With this insight the researchers developed a new method to measure quantitatively near-field intensities of optical nanoantennas. The resolution limit of conventional microscopy was overcome since the detection volume using the molecules was much smaller than the wavelength cubed. Compared to state-of-the-art optical near-field microscopy, the method of the Stuttgart group exhibits the unique advantage of measuring near-field distributions of three-dimensional nanoantenna structures. Daniel Dregely was able to incorporate molecules at specific locations during the fabrication process of the antenna structure. He could then detect the vibrational excitation and thus measure the near-field intensity. Such complex nanostructures add another degree of freedom to enhance the interaction of light with single molecules at the nanoscale. The design of future sensing devices will benefit from this new tool of assessing near-field intensities of three-dimensional optical antennas.

*) Reference: D. Dregely, F. Neubrech, H. Duan, R. Vogelgesang, and H. Giessen, “Vibrational near-field mapping of planar and buried three-dimensional plasmonic nanostructures”, Nature Communications (2013). http://www.nature.com/naturecommunications

Contact:
Prof. Harald Giessen, University of Stuttgart, 4th Physics Institute,
Tel. +49 711 68565111, e-mail: giessen (at) physik.uni-stuttgart.de
or
Dipl.-Phys. Daniel Dregely, University of Stuttgart, 4th Physics Institute, Tel. +49 711 68564961, e-mail: d.dregely (at) physik.uni-stuttgart.de

Andrea Mayer-Grenu | idw
Further information:
http://www.uni-stuttgart.de
http://www.nature.com/naturecommunications

More articles from Physics and Astronomy:

nachricht Tangled magnetic fields power cosmic particle accelerators
14.12.2018 | DOE/SLAC National Accelerator Laboratory

nachricht In search of missing worlds, Hubble finds a fast evaporating exoplanet
14.12.2018 | NASA/Goddard Space Flight Center

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: Data use draining your battery? Tiny device to speed up memory while also saving power

The more objects we make "smart," from watches to entire buildings, the greater the need for these devices to store and retrieve massive amounts of data quickly without consuming too much power.

Millions of new memory cells could be part of a computer chip and provide that speed and energy savings, thanks to the discovery of a previously unobserved...

Im Focus: An energy-efficient way to stay warm: Sew high-tech heating patches to your clothes

Personal patches could reduce energy waste in buildings, Rutgers-led study says

What if, instead of turning up the thermostat, you could warm up with high-tech, flexible patches sewn into your clothes - while significantly reducing your...

Im Focus: Lethal combination: Drug cocktail turns off the juice to cancer cells

A widely used diabetes medication combined with an antihypertensive drug specifically inhibits tumor growth – this was discovered by researchers from the University of Basel’s Biozentrum two years ago. In a follow-up study, recently published in “Cell Reports”, the scientists report that this drug cocktail induces cancer cell death by switching off their energy supply.

The widely used anti-diabetes drug metformin not only reduces blood sugar but also has an anti-cancer effect. However, the metformin dose commonly used in the...

Im Focus: New Foldable Drone Flies through Narrow Holes in Rescue Missions

A research team from the University of Zurich has developed a new drone that can retract its propeller arms in flight and make itself small to fit through narrow gaps and holes. This is particularly useful when searching for victims of natural disasters.

Inspecting a damaged building after an earthquake or during a fire is exactly the kind of job that human rescuers would like drones to do for them. A flying...

Im Focus: Topological material switched off and on for the first time

Key advance for future topological transistors

Over the last decade, there has been much excitement about the discovery, recognised by the Nobel Prize in Physics only two years ago, that there are two types...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

ICTM Conference 2019: Digitization emerges as an engineering trend for turbomachinery construction

12.12.2018 | Event News

New Plastics Economy Investor Forum - Meeting Point for Innovations

10.12.2018 | Event News

EGU 2019 meeting: Media registration now open

06.12.2018 | Event News

 
Latest News

Data use draining your battery? Tiny device to speed up memory while also saving power

14.12.2018 | Power and Electrical Engineering

Tangled magnetic fields power cosmic particle accelerators

14.12.2018 | Physics and Astronomy

In search of missing worlds, Hubble finds a fast evaporating exoplanet

14.12.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>