Spherical SiO2 particles with different sizes (30, 80, 120, and 180 nm) have been coated with Gd2O3:Yb3+/Er3+ layers by a heterogeneous precipitation method, leading to the formation of core-shell structural Gd2O3:Yb3+/Er3+@SiO2 particles. The samples were characterized by using X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, upconversion (UC) emission spectra, and fluorescent dynamical analysis. The obtained core-shell particles have perfect spherical shape with narrow size distribution. Under the excitation of 980 nm diode laser, the core-shell samples showed size-dependent upconversion luminescence (UCL) properties. The inner SiO2 cores in core-shell samples were proved to have limited effect on the total UCL intensities of Er3+ ions. The UCL intensities of core-shell particles were demonstrated much higher than the values obtained in pure Gd2O3:Yb3+/Er3+ with the same phosphor volume. The dependence of the specific area of a UCL shell on the size of its inner SiO2 particle was calculated and analyzed for the first time. It was confirmed that the surface effect came from the outer surfaces of emitting shells is dominant in influencing the UCL property in the core-shell samples. Three-photon UC processes for the green emissions were observed in the samples with small sizes of SiO2 cores. The results of dynamical analysis illustrated that more nonradiative relaxation occurred in the core-shell samples with smaller SiO2 core sizes.

2.
Y.
Lu
,
Y.
Yin
,
Z.
Li
, and
Y.
Xia
,
Nano Lett.
2
,
785
(
2002
).
3.
P.
Schuetzand
and
F.
Caruso
,
Chem. Mater.
14
,
4509
(
2002
).
4.
V.
Suryanarayanan
,
A. S.
Nair
, and
R. T.
Tom
,
J. Mater. Chem.
14
,
2661
(
2004
).
5.
Z.
Li
,
Y.
Zhang
, and
S.
Jiang
,
Adv. Mater.
20
,
4765
(
2008
).
6.
Y.
Liu
,
D.
Tu
,
H.
Zhu
,
R.
Li
,
W.
Luo
, and
X.
Chen
,
Adv. Mater.
22
,
3266
(
2010
).
7.
F.
Zhang
,
G. B.
Braun
,
Y.
Shi
,
Y.
Zhang
,
X.
Sun
,
N. O.
Reich
,
D.
Zhao
, and
G.
Stucky
,
J. Am. Chem. Soc.
132
,
2850
(
2010
).
8.
W. L.
Wilson
,
P. F.
Szajowski
, and
L. E.
Brus
,
Science
262
,
1242
(
1993
).
9.
I.
Haq
,
E.
Matijević
, and
K.
Akhtar
,
Chem. Mater.
9
,
2659
(
1997
).
10.
X.
Peng
,
M. C.
Schlamp
,
A. V.
Kadavanich
, and
A. P.
Alivisatos
,
J. Am. Chem. Soc.
119
,
7019
(
1997
).
11.
V. V.
Hardikar
and
E.
Matijević
,
J. Colloid Interface Sci.
221
,
133
(
2000
).
12.
F.
Caruso
,
Adv. Mater.
11
,
13
(
2001
).
13.
Y.
Lei
and
W.
Chim
,
J. Am. Chem. Soc.
127
,
1487
(
2005
).
14.
G.
Liu
and
G.
Hong
,
J. Solid State Chem.
178
,
1647
(
2005
).
15.
F.
Caruso
,
A. S.
Susha
,
M.
Giersig
, and
H.
Möhwald
,
Adv. Mater.
11
,
950
(
1999
).
16.
S. H.
Im
,
T.
Herricks
,
Y. T.
Lee
, and
Y.
Xia
,
Chem. Phys. Lett.
401
,
19
(
2005
).
17.
A.
Dokoutchaev
,
J. T.
James
,
S. C.
Koene
,
S.
Pathak
,
G. K. S.
Prakash
, and
M. E.
Thompson
,
Chem. Mater.
11
,
2389
(
1999
).
18.
K. W.
Chang
and
J. J.
Wu
,
Adv. Mater.
17
,
241
(
2005
).
20.
T.
Hebert
,
R.
Wannemacher
,
W.
Lenth
, and
R.
Macfarlane
,
Appl. Phys. Lett.
57
,
1727
(
1990
).
21.
F.
Wang
,
Y.
Han
,
C. S.
Lim
,
Y.
Lu
,
J.
Wang
,
J.
Xu
,
H.
Chen
,
C.
Zhang
,
M.
Hong
, and
X.
Liu
,
Nature
463
,
1061
(
2010
).
22.
M.
Haase
and
H.
Schäfer
,
Angew. Chem., Int. Ed.
50
,
5808
(
2011
).
23.
K.
Zheng
,
D.
Zhang
,
D.
Zhao
,
N.
Liu
, and
W.
Qin
,
J. Fluorine Chem.
132
,
5
(
2011
).
24.
H.
Guo
,
N.
Dong
,
M.
Yin
,
W. P.
Zhang
,
L. R.
Lou
, and
S. D.
Xia
,
J. Phys. Chem. B
108
,
19205
(
2004
).
25.
H.
Song
,
B.
Sun
,
T.
Wang
,
S.
Lu
,
L.
Yang
,
B.
Chen
,
X.
Wang
, and
X.
Kong
,
Solid State Commun.
132
,
409
(
2004
).
26.
K.
Zheng
,
L.
Wang
,
D.
Zhang
,
D.
Zhao
, and
W.
Qin
,
Opt. Express
18
,
2934
(
2010
).
27.
X.
Bai
,
H.
Song
,
G.
Pan
,
Y.
Lei
,
T.
Wang
,
X.
Ren
,
S.
Lu
,
B.
Dong
,
Q.
Dai
, and
L.
Fan
,
J. Phys. Chem. C
111
,
13611
(
2007
).
28.
G.
Liu
,
H.
Zhuang
, and
X.
Chen
,
Nano Lett.
2
,
535
(
2002
).
29.
X.
Chen
,
H.
Zhuang
,
G.
Liu
,
S.
Li
, and
R. S.
Niedbala
,
J. Appl. Phys.
94
,
5559
(
2003
).
30.
W.
Stöber
,
A.
Fink
, and
E.
Bohn
,
J. Colloid Interface Sci.
26
,
62
(
1968
).
31.
M.
Yu
,
H.
Wang
,
C.
Lin
,
G.
Li
, and
J.
Lin
,
Nanotechnology
17
,
3245
(
2006
).
32.
G.
Li
,
Z.
Wang
,
Z.
Quan
,
C.
Li
, and
J.
Lin
,
Cryst. Growth Des.
7
,
1797
(
2007
).
33.
M.
Yu
,
J.
Lin
, and
J.
Fang
,
Chem. Mater.
17
,
1783
(
2005
).
34.
P.
Jia
,
X.
Liu
,
G.
Li
,
M.
Yu
,
J.
Fang
, and
J.
Lin
,
Nanotechnology
17
,
734
(
2006
).
35.
H.
Wang
,
M.
Yu
,
C.
Lin
,
X.
Liu
, and
J.
Lin
,
J. Phys. Chem. C
111
,
11223
(
2007
).
36.
Y. V.
Yermolayeva
,
A. V.
Tolmachev
,
T. I.
Korshikova
,
R. P.
Yavetskiy
,
M. V.
Dobrotvorskaya
,
N. I.
Danylenko
, and
D. S.
Sofronov
,
Nanotechnology
20
,
325601
(
2009
).
37.
S.
Tan
,
P.
Yang
,
N.
Niu
,
S.
Gai
,
J.
Wang
,
X.
Jing
, and
J.
Lin
,
J. Alloy Compd.
490
,
684
(
2010
).
38.
K.
Zheng
,
D.
Zhang
,
D.
Zhao
,
N.
Liu
, and
W.
Qin
,
Phys. Chem. Chem. Phys.
12
,
7620
(
2010
).
39.
M.
Pollnau
,
D. R.
Gamelin
,
S. R.
Lüthi
,
H. U.
Güdel
, and
M. P.
Hehlen
,
Phys. Rev. B
61
,
3337
(
2000
).
40.
W. T.
Carnall
,
P. R.
Fields
, and
K.
Rajnak
,
J. Chem. Phys.
49
,
4424
(
1968
).
41.
A.
Patra
,
C.
Friend
,
R.
Kapoor
, and
P.
Prasad
,
J. Phys. Chem. B
106
,
1909
(
2002
).
42.
J. A.
Capobianco
,
F.
Vetrone
,
T.
D'Alesio
,
G.
Tessari
,
A.
Speghini
, and
M.
Bettinelli
,
Phys. Chem. Chem. Phys.
2
,
3203
(
2000
).
43.
See supplementary material at http://dx.doi.org/10.1063/1.4830009 for the method of synthesis of solid Gd2O3:Yb3+/Er3+ nanocrystals and the variation relationship of SiO2 core sizes and the specific areas of UCL shells in GYES samples (both the outer and inner surfaces of UCL shells are considered in here) (Fig. S1).

Supplementary Material

You do not currently have access to this content.