Like a Hogwarts student practicing the Wand-Lighting Charm “Lumos” spell, it keeps the light at the end of a silver nanowire and uses it to show previously unseen details, such as colors.

Scientists have created new materials for next-generation electronics that are so small that they are not only unidentifiable when closely packed, but they also don’t reflect enough light for even the most powerful optical microscopes to show minute features like colors.

Carbon nanotubes, for example, appear grayish under an optical microscope. Scientists find it difficult to investigate nanoparticles’ unique features and find ways to improve them for industrial application because they can’t differentiate fine details and differences between individual pieces.

In a new study published today in Nature Communications, researchers from UC Riverside describe a groundbreaking imaging technique that compresses lamp light into a nanometer-sized area in a new article published in Nature Communications. Like a Hogwarts student practicing the “Lumos” spell, it keeps the light at the end of a silver nanowire and uses it to show previously unseen details, such as colors.

The breakthrough, which improves color-imaging resolution to an unprecedented 6 nanometer level, will allow scientists to examine nanomaterials in sufficient detail to make them more useful in electronics and other applications.

Ming Liu and Ruoxue Yan, associate professors in the Marlan and Rosemary Bourns College of Engineering at UC Riverside, created this one-of-a-kind instrument utilizing a superfocusing technique invented by the team. Previously, the approach was utilized to examine the vibration of molecular bonds at 1-nanometer spatial resolution without the use of a focusing lens.

Liu and Yan improved the method in the new report to measure signals spanning the entire visible wavelength range, which may be used to display the color and depict the electrical band structures of the item rather than just molecular vibrations. The tool compresses light from a tungsten lamp into a silver nanowire with near-zero scattering or reflection, where light is conveyed by an oscillation wave of free electrons at the silver surface.

The condensed light travels in a conical route from the silver nanowire tip, which has a radius of just 5 nanometers, similar to a flashlight’s light beam. The influence of an object on the beam shape and color is detected and recorded as the tip passes over it.

“It is like using your thumb to control the water spray from a hose,” says Liu, “You know how to get the desired spraying pattern by changing the thumb position, and likewise, in the experiment, we read the light pattern to retrieve the details of the object blocking the 5 nm-sized light nozzle.” 

The light is then concentrated into a spectrometer, where it takes the shape of a small ring. The researchers can colorize absorption and scattering images by scanning the probe across an area and recording two spectra for each pixel. The previously grayish carbon nanotubes are photographed in color for the first time, and each carbon nanotube can now display its own distinct hue.

“The atomically smooth sharp-tip silver nanowire and its nearly scatterless optical coupling and focusing is critical for the imaging,” said Yan. “Otherwise there would be intense stray light in the background that ruins the whole effort. “

The researchers believe the new approach will be useful in assisting the semiconductor sector in producing uniform nanomaterials with consistent characteristics for use in electronic devices. The new full-color nano-imaging approach should help researchers learn more about catalysis, quantum optics, and nanoelectronics.

Source: 10.1038/s41467-021-27216-5

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