ORNL's nanoprobe, which is based on a light scattering technique, can detect and analyze chemicals, explosives, drugs and more at a theoretical single-molecule level. This capability makes it far more selective and accurate than conventional competing technologies.
The probe is an optical fiber tapered to a tip measuring 100 nanometers with an extremely thin coating of nanoparticles of silver, which induces the surface-enhanced Raman scattering (SERS) effect. Normally, when a sample is illuminated by a laser beam, there is a small reflection of light, known as Raman scattering. The light shows vibration energies, which are unique to each compound, and that information allows scientists to identify the substance.
With the SERS nanoprobe, the laser light creates rapid oscillations of the electrons in the silver nanoparticles, which produce an enormous electromagnetic field that contributes to increase the Raman scattering signal. The ORNL nanoprobe works with any surface to induce the SERS effect.
"The significance of this work is that we are now able to perform direct analysis of samples -- even dry samples -- with no preparation of the surface," said ORNL's Tuan Vo-Dinh, who leads a team that developed the nanoprobe. "Also, the small scale of the nanoprobe demonstrates the potential for detection in nanoscale environments, such as at the intracellular level."
Ordinarily, surface-enhanced Raman scattering analysis of samples on a surface requires modification or treatment of the sample. This may consist of physically removing the sample and diluting it in a liquid containing silver nanoparticles; however, this practice is unnecessary with the ORNL nanoprobe.