Scientists at the University of Cambridge have successfully powered insulating nanoparticles using molecular antennas, developing an extremely pure near-infrared LED. The results of this research, published in the November 19th issue of *Nature*, mark the creation of a new class of ultra-pure near-infrared LEDs with potential applications in medical diagnostics, optical communication systems, and sensing technologies. The research team at the Cavendish Laboratory at the University of Cambridge focuses on the study of nano-optoelectronic materials and devices.
The research team discovered that by attaching organic molecules, specifically 9-anthracenecarboxylic acid (9-ACA), to cerium-doped rare-earth nanoparticles (LnNPs), these molecules act as miniature antennas, effectively transferring electrical energy to these typically non-conductive particles. This innovative method allows these nanoparticles, which have long been incompatible with electronic components, to emit light for the first time.
The core of the research lies in cerium-doped nanoparticles (LnNPs), a class of materials known for producing extremely pure and stable light, particularly in the second near-infrared range, which can penetrate dense biological tissue. Despite these advantages, their lack of electrical conductivity has long prevented their use in electronic components such as LEDs.
The research team solved this problem by developing a hybrid material combining organic and inorganic components. They attached organic dyes containing functional anchoring groups to the outer surface of the LnNPs. In the constructed LED, the charge is guided into the 9-ACA molecules, which act as molecular antennas, rather than directly transferring the charge to the nanoparticles.
Once triggered, these molecules enter an excited triplet state. In many optical systems, this triplet state is typically considered a "dark state" and is not utilized; however, in this design, over 98% of the energy is transferred from the triplet state to the cerium ions within the insulating nanoparticles, resulting in bright and efficient light emission. This new method allows the team's LnLEDs to operate at a low voltage of approximately 5 volts and produce electroluminescence with an extremely narrow spectral width and a peak external quantum efficiency exceeding 0.6%, making them significantly superior to competing technologies such as quantum dots.
This discovery opens up a wide range of potential applications for future medical devices. Miniature, injectable, or wearable LnLEDs could be used for deep tissue imaging to detect diseases such as cancer, monitor organ function in real time, or precisely trigger photosensitive drugs. The purity and narrow spectral width of the emitted light also offer promise for faster and clearer optical communication systems, potentially leading to more efficient data transmission with less interference.