New Nanomanufacturing Technique Advances Imaging, Biosensing Technology

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“It’s like the Three Bears story,” said Nealey. “We can put big ones on the big spots, but they won’t stick to the smaller spots; then put the next-sized one on the medium spot, but it won’t stick to the small spot. By this sequential manufacturing we’re able to arrive at these precise assemblies of three different-sized particles in close proximity to one another.”

Tiny separations

The spheres are separated by only a few nanometers. It is this tiny separation, coupled with the sequential ordering of the different-sized spheres, that produces the nanolensing effect.

“You get this concentration in the intensity of the light between the small- and the medium-sized nanoparticles,” said Nealey.

The scientists are already exploring using this “hot spot” for high-resolution sensing using spectroscopy. “If you put a molecule there, it will interact with the focused light,” said Liu. “The enhanced field at these hot spots will help you to get orders of magnitude stronger signals, and that gives us the opportunity to get ultra-sensitive sensing. Maybe ultimately we can detect single molecules.”

The researchers also foresee applying their manufacturing technique to nanoparticles of other shapes, such as rods and stars. “The physics of particles shaped differently than spheres enable even a wider spectrum of applications,” said Nealey.

“There’s a large range of properties that you could realize by putting particles with asymmetric shapes next to each other.” The method will have broad application for any process that requires precision placement of materials in proximity to the same or different types of materials. It will, Nealey predicts, “be part of the way that nanomanufacturing is done.”

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