Nanotech sensing to detect disease fake art and chemical weapons

A team of researchers in the US has developed a nanotechnology technique that improves the ability to detect specific molecules in diseases, chemical warfare agents or fake paintings.

The international team of researchers, led by University at Buffalo engineers, said they have made surface-enhanced Raman spectroscopy (SERS) simpler and more affordable.

SERS is a sensing technique known for its ability to identify chemical and biological molecules in a wide range of fields.

However, it has been relatively expensive to manufacture until now, as the materials required to perform the sensing are consumed upon use.

“The technology we're developing – a universal substrate for SERS – is a unique and potentially revolutionary feature,” said Qiaoqiang Gan, lead author of the study.

“It allows us to rapidly identify and measure chemical and biological molecules using a broadband nanostructure that traps a wide range of light,” he said.

The technology relies on 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. Just like a skeleton key that opens many doors,” Nan Zhang, the research co-author, said.

When a powerful laser affects chemical and biological molecules, the process can excite vibrational modes of these molecules and produce inelastic scattering - aka 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 utilizing a nano-patterned substrate that significantly enhances the light field at the surface and, therefore, the Raman scattering intensity.

Traditional substrates are typically designed for only a very narrow range of wavelengths, which makes it 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 the costs and time needed to perform the test.

The universal substrate that the engineers have been working on 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 applications of such a device are far-reaching,” said Kai Liu, co-author.

“The ability to detect even smaller amounts of chemical and biological molecules could be helpful with biosensors that are used to detect cancer, Malaria, HIV and other illnesses.”

Their technology could help identify chemicals in certain types of paint to detect forged art, improve the ability to detect amounts of toxins in the air or water or the detection of chemical weapons according to the researchers.

The paper was published on Tuesday in the journal Advanced Materials Interfaces.

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