Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Photonics: Sensing with holes

19.07.2012
Molecular sensors based on nanoholes in metallic films are shown to be ideal for medical diagnosis

The detection of small quantities of molecules is important for a myriad of applications, ranging from gas sensing to biomedical diagnostics. The majority of these applications require the sensors to be cheap and disposable, yet sensitive enough to detect molecules down to the single-molecule level.


SPP sensing. Nanohole films can be used in two different configurations to sense molecules in a water solution. In the reflection mode (top), light is directed at the sample from the water side. In the transmission mode (bottom), light is directed at the sample from the back, leading to different SPP properties. The SPP field intensity is represented by the color plot. The optical fields on the top and bottom are calculated for different resonance frequencies. © 2012 IEEE

Ping Bai and co-workers at the A*STAR Institute of High Performance Computing and the Institute of Materials Research and Engineering have now studied the properties of thin metallic films with holes in them that are particularly promising for molecular sensing.

Metallic thin films with nanometer-sized holes in them are known to transmit light of particular wavelengths very efficiently. The efficiency arises from surface plasmon polaritons (SPPs) — the collective movements of electrons on the metal surface — which are able to focus light into tiny spots much smaller than the wavelength of light used (see image).

These SPPs can be used to detect the molecules through the fluorescence of tracer molecules attached to them. This fluorescence is also strongly enhanced by the SPP and can easily be detected by a microscope even for small quantities of molecules. “The whole setup is ultra-compact to support a point-of-care sensing system,” explains Bai.

Bai and his colleagues studied two sensing arrangements. In the first arrangement, light is directed at a film with nanoholes at an oblique angle from the same side as the sample. In the second arrangement, the film is illuminated from the back so that light is travelling through the holes first. The researchers found that each scheme has its own advantages.

In the ‘reflection’ scheme, the SPP effect is stronger as the light is directly aimed at the sample and does not have to cross the metal film. However, a thicker film is needed so that the light does not pass through. In the ‘transmission’ scheme, the intensity of the light emitted by the molecules is weaker, but the advantage there is that filters and other sensors can possibly be included with the metal film, and the film thickness can be much thinner.

“There is therefore no clear advantage for either sensing modes of such films,” says Bai. “One thing that is clear from the study, however, is the clear benefits of using metal films with nanoholes as a molecular sensing platform,” says Bai.

“This is merely a snapshot of our whole project. Ultimately, our sensing technology will be utilized in hospitals and test centers, for example, in prostate cancer screening, or even used at home just like glucose test kits,” adds Bai.

The A*STAR-affiliated researchers contributing to this research are from the Institute of High Performance Computing and the Institute of Materials Research and Engineering

References:

Wu, L., Bai, P., Zhou, X. & Li, E. P. Reflection and transmission modes in nanohole-array-based plasmonic sensors. IEEE Photonics Journal 4, 26–33 (2012).

A*STAR Research | Research asia research news
Further information:
http://www.research.a-star.edu.sg/
http://www.researchsea.com

More articles from Materials Sciences:

nachricht Physics, photosynthesis and solar cells
01.12.2016 | University of California - Riverside

nachricht New process produces hydrogen at much lower temperature
01.12.2016 | Waseda University

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

Im Focus: Fraunhofer ISE Develops Highly Compact, High Frequency DC/DC Converter for Aviation

The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.

Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

UTSA study describes new minimally invasive device to treat cancer and other illnesses

02.12.2016 | Medical Engineering

Plasma-zapping process could yield trans fat-free soybean oil product

02.12.2016 | Agricultural and Forestry Science

What do Netflix, Google and planetary systems have in common?

02.12.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>