Visible Discrimination of Broadband Infrared Light by Dye-Enhanced Upconversion in Lanthanide-Doped Nanocrystals

Abstract

Optical upconversion of near infrared light to visible light is an attractive way to capture the optical energy or optical information contained in low-energy photons that is otherwise lost to the human eye or to certain photodetectors and solar cells. Until the recent application of broadband absorbing optical antennas, upconversion efficiency in lanthanide-doped nanocrystals was limited by the weak, narrow atomic absorption of a handful of sensitizer elements. In this work, we extend the role of the optical antenna to provide false-color, visible discrimination between bands of infrared radiation. By pairing different optical antenna dyes to specific nanoparticle compositions, unique visible emission is associated with different bands of infrared excitation. In one material set, the peak emission was increased 10-fold, and the width of the spectral response was increased more than 10-fold.

Ligand-Sensitized Lanthanide Nanocrystals: Merging Solid-State Photophysics and Molecular Solution Chemistry

“…Our current understanding of the periodic table’s f block marks the result of decades of research pursued by scientists of various stripes: from chemists to materials scientists, physicists, and biologists. As a consequence, the modern scientific catalog of understood phenomena arising either directly or indirectly from lanthanide chemistry and electronic structure is expansive, ranging from multiphoton up- and downconversion processes − to ligand–lanthanide chelation thermodynamics in solution − to lanthanide binding and efflux mechanisms in biological systems. − In particular, it has become both widely accepted and abundantly clear that the diversity in the f-orbital electronic structures of the lanthanide elements makes them prime candidates for various possible applications in optoelectronic devices, deep-tissue imaging, and luminescence sensing. ,− ,,, Interest in these applications provides much of the motivation driving both applied and fundamental research in lanthanide photochemistry.…”

“…Translating the advances made by researchers in these two camps into projects combining the best aspects of these disparate approaches seems to be an intuitive direction in which to take research in lanthanide photophysics. However, the amount of literature on the subject of utilizing ligand sensitization in solid-state lanthanide structures remains relatively small. ,,,,,,,− The most prominent work produced in this vein includes the first-ever report of lanthanide nanocrystal sensitization in the IR using tropolonate ligands and a 2012 finding by Zou et. al demonstrating the first example of two-photon upconversion luminescence in β-NaYF 4 :Er:Yb nanocrystals, with initial IR light absorption through an organic ligand .…”