Lee, Minji | Search NASA

DOE OSTI2023

A Generalized Approach to Photon Avalanche Upconversion in Luminescent Nanocrystals

Photon avalanching nanoparticles (ANPs) exhibit extremely nonlinear upconverted emission valuable for subdiffraction imaging, nanoscale sensing, and optical computing. Avalanching has been demonstrated with Tm 3+ -, Pr 3+ -, or Nd 3+ -doped nanocrystals, but their emission is limited to a few wavelengths and materials. Here, we utilize Gd 3+ -assisted energy migration to tune the emission wavelengths of Tm 3+ -sensitized ANPs and generate highly nonlinear emission from Eu 3+ , Tb 3+ , Ho 3+ , and Er 3+ ions. The upconversion intensities of these spectrally discrete ANPs scale with nonlinearity factor s = 10-17 under 1064 nm excitation at power densities as low as 7 kW cm -2 . This strategy for imprinting avalanche behavior on remote emitters can be extended to fluorophores adjacent to ANPs, as here we demonstrate with CdS/CdSe/CdS core/shell/shell quantum dots. ANPs with rationally designed energy transfer networks provide the means to transform conventional linear emitters into a highly nonlinear ones, expanding the use of photon avalanching in biological, chemical, and photonic applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2022

Dynamically tunable multicolor emissions from zero-dimensional Cs 3 LnCl 6 (Ln: europium and terbium) nanocrystals with wide color gamut

This study demonstrates dynamically tunable multicolor emissions from a single component, zero-dimensional (0-D) cesium europium chloride (Cs 3 EuCl 6 ) and cesium terbium chloride (Cs 3 TbCl 6 ) nanocrystals (NCs). Highly uniform colloidal Cs 3 EuCl 6 and Cs 3 TbCl 6 NCs are synthesized via the heating-up method. Excitation-wavelength-dependent multicolor emissions from Cs 3 EuCl 6 and Cs 3 TbCl 6 NCs are observed. Under excitation of 330–400 nm, both NCs exhibit blue photoluminescence (PL). Under wavelengths shorter than 330 nm, characteristic red and green emissions are observed from Cs 3 EuCl 6 and Cs 3 TbCl 6 , respectively, owing to the atomic emissions from the f-orbitals in trivalent europium (Eu 3+ ) and terbium (Tb 3+ ) ions. Cs 3 EuCl 6 and Cs 3 TbCl 6 NCs exhibit broadband excitation spectra and enhanced absorption properties. Particularly, Cs 3 EuCl 6 NCs exhibit a very narrow full-width at half-maximum in both blue and red PL and no overlap between the two spectra. Further, the photophysical properties of these NCs are further investigated to understand the multicolor PL origins by time-resolved and temperature-dependent PL measurements. Finally, the potential applications of Cs 3 EuCl 6 and Cs 3 TbCl 6 NCs as anti-counterfeiting inks for high-level security are demonstrated. Given their broadband excitation with enhanced absorption properties and dynamically tunable colors with a wide color gamut, Cs 3 EuCl 6 and Cs 3 TbCl 6 NCs have great potential as novel multicolor NC emitters for many emerging applications.

77 NANOSCIENCE AND NANOTECHNOLOGY↗