Scientific Achievement
Discovery of visible/NIR-emitting upconverting nanoparticles (UCNPs) that upconvert SWIR light (1700-2000 nm).
Significance and Impact
These UCNPs can upconvert light that is up to 400 nm longer than previous designs. The 1740 nm excitation wavelength maximizes its transmission through tissue & low atmosphere, opening the possibility of ultra-deep-tissue imaging, more efficient solar harvesting, night vision technologies, and SWIR detector design.
Research Details
- The researchers developed high-throughput modeling to calculate over >200,000 spectra of different lanthanide dopant combinations.
- The team developed a method to experimentally measure upconverted 2D emission-excitation maps, confirming that Tm-doped UCNPs upconvert 1740 nm light to 800 nm, while Tm/Ho-codoped UCNPs upconvert 1740 or 1950 nm to 650 nm light.
Qi, X., Lee, C., Usprung, B., Skripka, A., Schuck, P.J., Chan, E.M., Cohen, B. J. Am. Chem. Soc. 2024, 146, 43, 29292–29296. DOI: 10.1021/jacs.4c11181
Research Summary
Optical technologies enable real-time, noninvasive analysis of complex systems but are limited to discrete regions of the optical spectrum. While wavelengths in the short-wave infrared (SWIR) window (typically, 1700–3000 nm) should enable deep subsurface penetration and reduced photodamage, there are few luminescent probes that can be excited in this region. Here, we report the discovery of lanthanide-based upconverting nanoparticles (UCNPs) that efficiently convert 1740 or 1950 nm excitation to wavelengths compatible with conventional silicon detectors.
Experimental upconverted photoluminescence excitation (U-PLE) spectra find that 10% Tm3+-doped NaYF4 core/shell UCNPs have the strongest 800 nm emission from SWIR wavelengths, while UCNPs with an added 2% or 10% Ho3+ show the strongest red emission when excited at 1740 or 1950 nm. Mechanistic modeling shows that addition of a low percentage of Ho3+ to Tm3+-doped UCNPs shifts their emission from 800 to 652 nm by acting as a hub of efficient SWIR energy acceptance and redistribution up to visible emission manifolds. Parallel experimental and computational analysis shows rate equation models are able to predict compositions for specific wavelengths of both excitation and emission. These SWIR-responsive probes open a new IR bioimaging window, and are responsive at wavelengths important for vision technologies.
