New tech to detect diseases, fraudulent art, chemical weapons

Scientists have developed a new sensing technology that uses Raman spectroscopy to improve the ability to rapidly detect diseases, fraudulent art, chemical weapons and environmental contaminants.
Surface-enhanced Raman spectroscopy (SERS) is a sensing technique prized for its ability to identify chemical and biological molecules in a wide range of fields.
It has been commercialised, but not widely, because the materials required to perform the sensing are consumed upon use, relatively expensive and complicated to fabricate.
Now, an international research team led by University at Buffalo engineers has developed nanotechnology that promises to make SERS simpler and more affordable.
The advancement aims to improve our ability to detect trace amounts of molecules in diseases, chemical warfare agents, fraudulent paintings, environmental contaminants and more.

"The technology we're developing - a universal substrate for SERS - is a unique and, potentially, revolutionary feature. It allows us to rapidly identify and measure chemical and biological molecules using a broadband nanostructure that traps wide range of light," said Qiaoqiang Gan, the study's lead author.

When a powerful laser interacts chemical and biological molecules, the process can excite vibrational modes of these molecules and produce inelastic scattering, also called Raman scattering, of light.
As the beam hits these molecules, it can produce photons that have a different frequency from the laser light. While rich in details, the signal from scattering is weak and difficult to read without a very powerful laser.

SERS addresses the problem by utilising a nanopatterned substrate that significantly enhances the light field at the surface and, therefore, the Raman scattering intensity.
Unfortunately, traditional substrates are typically designed for only a very narrow range of wavelengths.
This is problematic because different substrates are needed if scientists want to use a different laser to test the same molecules.
In turn, this requires more chemical molecules and substrates, increasing costs and time to perform the test.
The universal substrate solves the problem because it can trap a wide range of wavelengths and squeeze them into very small gaps to create a strongly enhanced light field.

The technology consists of a thin film of silver or aluminium that acts as a mirror, and a dielectric layer of silica or alumina.
The dielectric separates the mirror with tiny metal nanoparticles randomly spaced at the top of the substrate.
"It acts similar to a skeleton key. Instead of needing all these different substrates to measure Raman signals excited by different wavelengths, you'll eventually need just one," Zhang added.
The research was published in the journal Advanced Materials Interfaces.