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Synthesis of 10 nm β‐NaYF 4 :Yb,Er/NaYF 4 Core/Shell Upconversion Nanocrystals with 5 nm Particle Cores
Author(s) -
Rinkel Thorben,
Raj Athira Naduviledathu,
Dühnen Simon,
Haase Markus
Publication year - 2016
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201508838
Subject(s) - nucleation , materials science , photon upconversion , nanocrystal , particle (ecology) , chemical engineering , nanoparticle , ion , particle size , phase (matter) , shell (structure) , nanotechnology , inorganic chemistry , luminescence , chemistry , composite material , optoelectronics , organic chemistry , oceanography , geology , engineering
A new method is presented for preparing gram amounts of very small core/shell upconversion nanocrystals without additional codoping of the particles. First, ca. 5 nm β‐NaYF 4 :Yb,Er core particles are formed by the reaction of sodium oleate, rare‐earth oleate, and ammonium fluoride, thereby making use of the fact that a high ratio of sodium to rare‐earth ions promotes the nucleation of a large number of β‐phase seeds. Thereafter, a 2 nm thick NaYF 4 shell is formed by using 3–4 nm particles of α‐NaYF 4 as a single‐source precursor for the β‐phase shell material. In contrast to the core particles, however, these α‐phase particles are prepared with a low ratio of sodium to rare‐earth ions, which efficiently suppresses an undesired nucleation of β‐NaYF 4 particles during shell growth.