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Title: Probing the Crystal Structure and Formation Mechanism of Lanthanide-Doped Upconverting Nanocrystals

Journal Article · · Chemistry of Materials
 [1];  [2];  [2];  [2];  [3]
  1. Brown Univ., Providence, RI (United States); Karlsruhe Inst. of Technology (KIT), Eggenstein-Leopoldshafen (Germany)
  2. Brookhaven National Lab. (BNL), Upton, NY (United States)
  3. Brown Univ., Providence, RI (United States); Brookhaven National Lab. (BNL), Upton, NY (United States)
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Lanthanide (Ln)-doped upconverting nanocrystals (UCNCs), such as NaLnF4 (with Ln = lanthanide), constitute an important class of nanoscale materials due to their capacity to convert near-infrared photons into near-ultraviolet or visible light. Although under intense investigation for more than a decade, UCNCs have been relatively underexplored especially regarding their crystal structure and mechanisms of formation in organic media. The former is needed to explain the relationship between atomic scale structure and upconversion (UC) properties of UCNCs (i.e., local symmetry for 4f–4f transition probability, Ln3+ distances for energy migration), while the latter is essential to finely tune the size, morphology, chemical composition, and architecture of well-defined upconverting nanostructures, which constitute the experimental levers to modify the optical properties. In this contribution, we use synchrotron-based diffraction experiments coupled to Rietveld and pair distribution function (PDF) analyses to understand the formation of NaGdF4:Yb:Er UCNCs in organic media and to investigate their crystal structure. Our results reveal a complex mechanism of the formation of NaGdF4:Yb:Er UCNCs based on chemical reactions involving molecular clusters and in situ-generated, crystalline sodium fluoride at high temperature. Additionally, a detailed crystallographic investigation of NaGdF4:Yb:Er UCNCs is presented. Our Rietveld and PDF analyses show that the space group P$$\bar{6}$$ is the one that best describes the crystal structure of NaGdF4:Yb:Er UCNCs contrary to what has been recently proposed. Further, our Rietveld and PDF data reveal the formation of bulk-like crystal structure down to 10 nm with limited distortions. Finally, the results presented in this paper constitute an important step toward the comprehensive understanding of the underlying picture that governs UC properties of lanthanide-doped nanostructures.

Research Organization:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
Grant/Contract Number:
SC00112704
OSTI ID:
1376118
Report Number(s):
BNL-114005-2017-JA
Journal Information:
Chemistry of Materials, Vol. 28, Issue 23; ISSN 0897-4756
Publisher:
American Chemical Society (ACS)Copyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 23 works
Citation information provided by
Web of Science

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Cited By (6)

NaYF4 Microstructure, beyond Their Well-Shaped Morphology journal November 2019
Photoinduced dynamics to photoluminescence in Ln 3+ (Ln = Ce, Pr) doped β-NaYF 4 nanocrystals computed in basis of non-collinear spin DFT with spin-orbit coupling journal December 2017
Tuning of photoluminescence intensity of europium doped sodium yttrium fluorides synthesized via hydrothermal route journal July 2019
Magnetic and cryogenic magnetocaloric properties of NaGdF 4 nanocrystals journal October 2019
Recent insights into upconverting nanoparticles: spectroscopy, modeling, and routes to improved luminescence journal January 2019
Interface disorder in large single- and multi-shell upconverting nanocrystals journal January 2019

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