According to the "Nature" magazine website and the "Daily Science" website, for more than a decade, due to the phenomenon of optical flicker, scientists have failed to make a sustainable source of light in a single molecule. Now, scientists at the University of Rochester have solved the basic physical principles behind this phenomenon and have worked with researchers at Kodak, the US Naval Laboratory, and Cornell University to develop a nanocrystal that can continuously emit light. Nanocrystals having various compositions have been synthesized. The discovery is likely to open the door to the development of cheaper and more versatile lasers and brighter LED lighting.
Many molecules, as well as crystals that are only one billionth of a metre in size, absorb and emit photons. Unlike the outward radiation of photons, during the random period in which they absorb photons, energy is converted into heat, resulting in a loss of energy. These "dark" periods alternate with the normal periods of radiation photons, causing "flickering" of molecules and crystals.
Leading the study was Todd Kraus, an associate professor of chemistry at the University of Rochester. The researchers did not find the expected flicker after examining the synthesized new nanocrystals one by one. Even after 4 hours of continuous monitoring, there is still no flicker, which is an unheard of phenomenon, because conventional crystals will flicker within a few milliseconds to a few minutes. Studies have shown that the special structure of the new nanocrystals is an important reason why the "flickering" phenomenon no longer occurs. The core of conventional nanocrystals is composed of a semiconductor material, and the outer protective shell is composed of another material with a clear boundary between the two materials. The core of the new nanocrystals is composed of cadmium and selenium, and the protective shell is composed of zinc and selenium. There is a uniform transition structure between the two, which can effectively prevent the absorption of photons by the nanocrystals, so that the photon flux of the radiation is The absorbed photon flow remains stable.
Klaus said that the current lasers of different colors are still based on different materials and processes, and the new nanocrystals can be made into lasers of different colors in a single manufacturing process, that is, only by changing the size of the nanocrystals. Changing the color of light is easy. The new nanocrystals enable a higher level of biomarker tracking and lay the foundation for the manufacture of inexpensive and flexible lasers and higher brightness LED lighting, and are expected to replace existing OLED lighting systems. In the future, by painting nanocrystals of different sizes on a flat surface, you can create a paper-thin display or a wall that illuminates the room in any color.
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