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Sensor Amplifies Molecule Signatures

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A new spectroscopy technique can accurately identify the structure and composition of individual molecules.

Researchers from the Rice University Laboratory for Nanophotonics (LANP) developed the device, which they said has the ability to amplify single molecules’ optical signatures by about 100 billion times. It is designed to study individual molecules that contain fewer than 20 atoms.

“The ideal single-molecule sensor would be able to identify an unknown molecule — even a very small one — without any prior information about that molecule’s structure or composition,” said lead researcher and LANP Director Dr. Naomi Halas. “That’s not possible with current technology, but this new technique has that potential.”


The SECARS molecular sensor contains an optical amplifier made of gold discs. The new technique can amplify a molecule’s optical signature as much as 100 billion times. Courtesy of Rice University.


The sensor uses coherent anti-Stokes Raman spectroscopy (CARS) in conjunction with an optical quadrumer amplifier made from gold nanodiscs. The LANP researchers call the new method surface-enhanced CARS (SECARS).

“Amplification is important for sensing small molecules because the smaller the molecule, the weaker the optical signature,” Halas said. “This amplification method is the most powerful yet demonstrated, and it could prove useful in experiments where existing techniques can’t provide reliable data.”

The optical amplifier contains four nanodiscs in a diamond-shaped arrangement. Optical signatures of molecules are caught in a 15-nm-wide gap in the center, and can be amplified through the efficient light-harvesting and signal-scattering properties of the four-disc structure.

Potential applications that could benefit from SECARS include chemical and biological sensing, as well as metamaterials research.

The work was funded by the U.S. Department of Defense, the Defense Threat Reduction Agency and the Robert A. Welch Foundation. The research was published in Nature Communications (doi: 10.1038/ncomms5424). 

For more information, visit www.rice.edu.
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Published: July 2014
Glossary
nano
An SI prefix meaning one billionth (10-9). Nano can also be used to indicate the study of atoms, molecules and other structures and particles on the nanometer scale. Nano-optics (also referred to as nanophotonics), for example, is the study of how light and light-matter interactions behave on the nanometer scale. See nanophotonics.
raman spectroscopy
Raman spectroscopy is a technique used in analytical chemistry and physics to study vibrational, rotational, and other low-frequency modes in a system. Named after the Indian physicist Sir C.V. Raman who discovered the phenomenon in 1928, Raman spectroscopy provides information about molecular vibrations by measuring the inelastic scattering of monochromatic light. Here is a breakdown of the process: Incident light: A monochromatic (single wavelength) light, usually from a laser, is...
nanophotonics
Nanophotonics is a branch of science and technology that explores the behavior of light on the nanometer scale, typically at dimensions smaller than the wavelength of light. It involves the study and manipulation of light using nanoscale structures and materials, often at dimensions comparable to or smaller than the wavelength of the light being manipulated. Aspects and applications of nanophotonics include: Nanoscale optical components: Nanophotonics involves the design and fabrication of...
AmericasatomsBasic ScienceCARScoherent anti-Stokes Raman spectroscopydefenseDefense Threat Reduction AgencyLaboratory for NanophotonicsLANPMaterialsmoleculesnanoNaomi Halasoptical signatureOpticsRaman spectroscopyResearch & TechnologyRice UniversityRobert A. Welch FoundationSensors & DetectorsTexasnanophotonicsquadrumer amplifiernanodiscssurface-enhanced CARSSECARSYu ZhangU.S. Department of Defense

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