Selectively enhanced red upconversion luminescence and phase/size manipulation via Fe(3+) doping in NaYF4:Yb,Er nanocrystals.
Red upconversion luminescence (UCL) is selectively enhanced by about 7 times via Fe(3+) codoping into a NaYF4:Yb,Er nanocrystalline lattice. The maximum red-to-green ratio (R/G) as well as the overall integrated UCL intensity features at an Fe(3+) content of 20 mol%. The size and phase of nanocrystals are simultaneously manipulated via Fe(3+) doping with various concentrations by a facile hydrothermal method. Contrary to the literature, the pure hexagonal phase appears when Fe(3+) concentrations are from 5 to 20 mol%, meanwhile, the size of NaYF4:Yb,Er nanocrystals reaches its maximum at 10 mol%. The intensified visible UCL especially the dominant red emission is mainly ascribed to the energy transfer (ET) from |(2)F7/2, (4)T1g > (Yb(3+)-Fe(3+) dimer) to (4)F9/2 (Er(3+)) states as well as the distortion of the crystalline field symmetry upon Fe(3+) codoping. Dynamic investigation of (4)S3/2 and (4)F9/2 states under the pulsed laser excitation of 980 nm along with the diffuse reflectance data further supports the proposed mechanism of UC processes. The results show the remarkable promise of Fe(3+)-codoped NaYF4:Yb,Er nanocrystals as upconverting nanoprobes with high sensitivity and penetrability in deeper tissue for multimodal biomedical imaging.
School of Basic Sciences & Advanced Institute of Materials Science, Changchun University of Technology, 2055 Yan'an Street, Changchun, Jilin 130012, P.R. China. chenli@ccut.edu.cn.
Jing
J
Tang
Li
L
Chen
Jing
J
Li
Zhe
Z
Wang
Jiahua
J
Zhang
Ligong
L
Zhang
Yongshi
Y
Luo
Xiaojun
X
Wang
D004871:Erbium / Q000737:chemistry*; D005459:Fluorides / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D008163:Luminescent Measurements; D053758:Nanoparticles / Q000737:chemistry*; D015019:Yttrium / Q000737:chemistry*
C525362:sodium yttriumtetrafluoride; D015019:Yttrium; D004871:Erbium; D007501:Iron; D005459:Fluorides