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 A better way to weigh millions of solitary stars
15.12.2017 | Vanderbilt University

nachricht A chip for environmental and health monitoring
15.12.2017 | Friedrich-Alexander-Universität Erlangen-Nürnberg

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: First-of-its-kind chemical oscillator offers new level of molecular control

DNA molecules that follow specific instructions could offer more precise molecular control of synthetic chemical systems, a discovery that opens the door for engineers to create molecular machines with new and complex behaviors.

Researchers have created chemical amplifiers and a chemical oscillator using a systematic method that has the potential to embed sophisticated circuit...

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

Engineers program tiny robots to move, think like insects

15.12.2017 | Power and Electrical Engineering

One in 5 materials chemistry papers may be wrong, study suggests

15.12.2017 | Materials Sciences

New antbird species discovered in Peru by LSU ornithologists

15.12.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>