American scientists have developed an ultra-sensitive sensor that can use its enhanced Raman scattering to detect substances including cancer signals and explosives. Its sensitivity is 1 billion times greater than that of ordinary Raman scattering sensors.
Raman scattering refers to the frequency change of light caused by the interaction between incident light and molecular motion when light passes through the medium. It was discovered by Indian physicist Chandra Sekhara Raman in 1928. In Raman scattering, when a beam of monochromatic light strikes an object, its reflected light will contain light at two other frequencies, the frequencies of these two lights are only related to the molecular composition of the object, which potentially provides A method for effectively identifying substances. But because this extra light is too weak, it has been difficult for scientists to put Raman scattering into practice for decades.
In the 1970s, scientists developed surface-enhanced Raman scattering (SERS) technology, which can enhance the Raman signal by placing the identified substance on a rough metal surface or small gold and silver particles. But scientists later discovered that this enhanced Raman signal only appeared on a few random points on the surface of the sensor, and it was difficult to predict its specific location, which was still very weak.
The team led by Stephen Zhou, a professor of electrical engineering at Princeton University, abandoned the previous methods of designing and manufacturing Raman sensors and developed a new SERS structure: a chip is covered with rows of small pillars composed of metal and semiconductor.
The “secret weapon†that the new sensor won is the arrangement of these small columns: each column has a hollow part made of metal at the top and bottom; the wall of the column is covered with metal particles (plasma nano Point), there is a gap of about 2 nanometers between the metal particles. Metal particles and voids can significantly enhance the Raman signal; the hollow part can capture the light signal, allowing light to pass through the plasma nanodots multiple times instead of only once, which can also enhance the Raman signal. So far, the sensitivity of the chip is 1 billion times higher than the sensor developed without Raman enhancement, and its sensitivity is very stable, and it can be reliably used in sensing equipment.
In addition to the greatly increased sensitivity, with the help of nanoimprint technology and nanoparticle self-assembly technology, the new chip can achieve high-quality, large-scale manufacturing. Researchers have already fabricated these sensors on 4-foot wafers.
Scientists at the US Naval Research Laboratory are also conducting relevant experiments, hoping that the military can also use the technology to detect chemicals, biological reagents and explosives.
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