Current state-of-the-art techniques have clear limitations when it comes to imaging the smallest nanoparticles, making it difficult for researchers to study viruses and other structures at the molecular level.
University of Houston and Texas MD Anderson Cancer Center scientists have reported Nature communication A new optical imaging technique for nanoscopic objects, relying on unrelated light to detect nanoparticles as small as 25 nanometers in diameter. The technique, known as a panorama, uses a glass slide covered with gold nanodiscs, allowing scientists to monitor changes in the transmission of light and determine the characteristics of the target.
Plasmonic nano-aperture takes its name from label-free imaging (plasmonic nano-aperture elabel-free iMAging), indicating the key features of panorama technology. Panoramas can be used to detect, count, and determine the size of individual dielectric nanoparticles.
VH-Chuan Shih, professor of electrical and computer engineering at UH and the same author for the paper, said that the smallest transparent object can be a standard microscope image between 100 nanometers and 200 nanometers. This is mainly because — apart from being so small — they do not reflect, absorb, or “scatter” enough light, which may allow imaging systems to detect their presence.
Labeling is another commonly used technique; This requires researchers to know something about the particle they are studying — a virus contains a spike protein, for example — and engineer a way to tag that particle. To detect particles easily is with fluorescent dye or any other method.
“Otherwise, it would appear invisible under the microscope as a small dust particle, because it is too small to detect,” Shih said.
Another shortcoming? Labeling is only useful when researchers already want to know at least something about the particle they want to study.
Shih said, “With Panorama, you don’t have to do labeling.” “You can see this directly because the panorama does not rely on detecting scattered light from the nanoparticle.”
Instead, the system allows observers to detect a transparent target as small as 25 nanometers by monitoring light transmission through a gold nanodisc-covered glass slide. By monitoring changes in light, they are able to detect nearby nanoparticles. The optical imaging system is a standard bright field microscope commonly found in any laboratory. Lasers or interferometers are not required which are required in many other label-free imaging technologies.
Shih said, “According to the data, the size limit has not been reached. We discontinued 25 nm nanoparticles only because it is the smallest polystyrene nanoparticle on the market.”
High-resolution imaging of living, moving cells using plasmonic metasurfs
Nareg Ohnesian et al. Plasmonic nano-aperture label-free imaging (panorama), Nature communication (2020). DOI: 10.1038 / s41467-020-19678-w
Provided by University of Houston
Quotes: New technology allowing more accurate viewing of the smallest nanoparticles (2020, 16 November) from 17 November 2020 at https://phys.org/news/2020-11-technology-precise-view-smallest-nanopart.html She gives.
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