Researchers at UMass Chan School of Medicine and North Carolina State University have developed ultra-fluorescent crystalline nanoparticles that use near-infrared light, a wavelength of light beyond what humans can see, to safely produce laser-quality light at room temperature. This discovery was published in Nature Photonicshas the potential to provide an easy-to-operate nano-light source for laser-based biomedical applications.
“Our efforts contribute to the next generation of light source technology for biomedical applications,” said Gang Han, PhD, professor of biochemistry and molecular biotechnology. We believe that these superfluorescent nanoparticles provide a revolutionary solution for bio-imaging and phototherapies that await a clean, intense light source. The ultra-fluorescence emission is an ideal alternative to lasers, as it is sharp and bright.”
Superluminescence is a special quantum optical phenomenon in which individual light emitters work together to coalesce into a giant quantum dipole. When aligned correctly, it is able to produce short bursts of light called superluminescence. However, its production is not easy.
“The huge size and extremely low temperature required for superfluorescence have made practical applications very challenging in biomedicine,” said Dr. Han.
To address these limitations, Han and Chuang Fang Lim, Ph.D., assistant professor of physics at North Carolina State University, have developed a unique way to achieve room-temperature superfluorescence.
It is difficult to achieve superfluorescence at room temperature because it is difficult for the atoms to be emitted together without being ‘knocked out’ of alignment by the surrounding environment. However, in Han and Dr. Lim’s particles, the light comes from electron orbitals “buried” under the other electrons, which act as a shield or insulator, allowing superfluorine even at room temperature.
“In addition, we doped a high concentration of ions in the crystal, which made the emitters very close and much easier to synchronize with each other,” Han said. “The transmitter distance in our system is only 0.35 nanometers, which is 27 times shorter than the transmitter distance in the previously reported ultrafluorescence medium.”
“When we excited the material with different laser intensities, we found that it emits three pulses of superfluorescence at regular intervals for each excitation,” said Dr. Lim, co-author of the research. “And the pulses don’t decay—each pulse is nanoseconds in length. So the higher-conversion nanoparticles not only exhibit superfluorescence at room temperatures, but do so in a controlled manner.”
Han also noted that based on the design of smart materials, the team showed that transformed superfluoridation can occur both in the assembly of nanocrystals and in a single nanocrystal, the latter of which was the smallest superfluoridation medium ever. They were able to produce a very sharp ultra-sharp emission peak with a full width with a narrow maximum of 2 nm in the plane of a single nanocrystal. In addition, the converted superluminescence has a lifetime of only 46 ns, which is more than 10,000-fold compared to conventional conversion luminescence.
“Superfluorescence from a single nanocrystal is very encouraging,” Han said. As the medium size is less than 500 nm, this makes our system an unprecedented alternative to lasers as a light source for biomedical applications. Since the superfluorescence of our system does not rely on any complex cavity or laser intermediate preparations, the synthesized nanocrystal is ready to use and produces a monochromatic, bright and rapid burst of light at room temperature. In this case, we envision that our product will provide a revolutionary, nano-sized, easy-to-operate light source for a number of laser-based biomedical applications. “
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