Finding a Single-Molecule

Researchers from Penn State have discovered a method that allows the detection of numerous biological and chemical species, and it can be done using gas, liquid, or solid samples. However, the truly notably thing is that the detection can be made using just a single molecule.

The invention is dubbed SLIPSERS, an acronym that combines “Slippery Liquid Infused Porous Surfaces” (SLIPS) and “Surface Enhanced Raman Scattering” (SERS).

SLAC National Accelerator Laboratory

“Being able to identify a single molecule is already very difficult. Being able to detect those molecules in all three phases [air, liquid, or bound to a solid] — that is really challenging,” said Tak-Sing Wong, assistant professor of mechanical engineering and the Wormley Family Early Career Professor in Engineering, in the press release.

The study has been published in Proceedings of the National Academy of Sciences (PNAS) and was funded by the National Science Foundation.

The New Future

In the abstract, the team notes the significance of their work: "Many analytes in real-life samples, such as body fluids, soil contaminants, and explosives, are dispersed in liquid, solid, or air phases. However, it remains a challenge to create a platform to detect these analytes in all of these phases with high sensitivity and specificity. Here, we demonstrate a universal platform."

Wong clarifies, "The problem is that trying to find a few molecules in a liquid medium is like trying to find a needle in a haystack. But if we can develop a process to gradually shrink the size of this liquid volume, we can get a better signal. To do that we need a surface that allows the liquid to evaporate uniformly until it gets to the micro or nanoscale. Other surfaces can’t do that, and that is where SLIPS comes in."

If a droplet of liquid is placed on any normal surface, it will begin to shrink from the top down. When the liquid evaporates, the target molecules are left in random configurations with weak signals. But if all the molecules can be clustered among the gold nanoparticles, they will produce a very strong Raman signal.

While there are multiple methods that allow scientists to concentrate molecules on a surface, the techniques typically require water as a medium. This latest method can be applied using organic liquids, which makes the discovery very useful for studying soil samples, which could lead to a host of applications related to environmental research.

In addition, researchers are now studying how the method can detect biomarkers in blood, which can lend itself to effective disease diagnosis in its early stages.

Also of note, although the SLIPS technology is patented and licensed, the team has not sought patent protection on their SLIPSER work. “We believe that offering this technology to the public will get it developed at a much faster pace,” said Professor Wong. “This is a powerful platform that we think many people will benefit from.”


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