Abstract
This report details spectroscopic characterizations of rare-earth, core-shell nanoparticles decorated with the f-element chelator 3,4,3-LI(1,2-HOPO). Evidence of photon downconversion is corroborated through detailed power dependence measurements, which suggest two-photon decay paths are active in these materials, albeit only representing a minority contribution of the sum luminescence, with emission being dominated by normal, Stokes' shifted fluorescence. Specifically, ultraviolet ligand photosensitization of Nd3+ ions in a NaGdF4 host shell results in energy transfer to a Nd3+/Yb3+-doped NaGdF4 nanoparticle core. The population and subsequent decay of core, Yb3+ 2F5/2 states result in a spectral shift of 620 nm, manifested in a NIR emission displaying luminescence profiles diagnostic of Yb3+ and Nd3+ excited state decays. Emphasis is placed on the generality of this material architecture for realizing ligand-pumped, multi-photon downconversion, with the Nd3+/Yb3+ system presented here functioning as a working prototype for a design principle that may be readily extended to other lanthanide pairs.
Highlights
Broadening the spectral bandwidth of conventional photovoltaics remains one of the chief avenues for generating photocurrent at the detailed-balance limit described by Shockley and Queisser (1961)
Methods previously explored include the relaxation of Laporte selection rules through the embedding of Ln ions in low-symmetry crystal hosts, and the photosensitization of f -states through the Downconverting Ligand-Sensitized Lanthanide Nanocrystals use of either ligand-to-metal charge transfer transitions in transition metal ions, or inter-band (d-f ) charge transfer in Ln such as Ce3+ or Eu2+ (Sun et al, 2017)
Successful synthesis was inferred from the results of transmission electron microscopy (TEM) and powder x-ray diffraction (XRD)
Summary
Broadening the spectral bandwidth of conventional photovoltaics remains one of the chief avenues for generating photocurrent at the detailed-balance limit described by Shockley and Queisser (1961). Recent work by Meijerink et al described a dye-sensitized NP system showing successful Pr3+/Yb3+ energy transfer, but excluded explicit proof of two-photon production through power dependence or quantum yield determinations (Wang and Meijerink, 2018).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
