Emission Enhancement and Color Tuning for GdVO4:Ln3+ (Ln = Dy, Eu) by Surface Modification at Single Wavelength Excitation

Article abstract of DOI:10.1021/acs.inorgchem.6b02125

The surface modification can realize systematically the emission enhancement of GdVO₄:Ln³⁺ (Ln = Dy, Eu) microstructures and multicolor emission at single component. The structure, morphology, composition, and the surface ligands modification of as-prepared samples were studied in detail. It is found that the surface-modified ligands can act as sensitizer to improve the emission of the Eu³⁺ and Dy³⁺ ions via the energy transfer besides the VO₄^3--Eu³⁺/Dy³⁺ process. More importantly, under a single wavelength excitation, the emission color can be effectively tuned by manipulating the doping ratio of the Eu³⁺ ions in the internal crystal lattice and the Tb³⁺ ions in the external surface ligands, simultaneously. And further, multicolor emissions are obtained under single wavelength excitation due to the high overlapping between the VO₄^3- absorption and the π-π? electron transition of the ligands. These findings may open new avenues to design and develop new highly efficient luminescent materials.

Full text of DOI:10.1021/acs.inorgchem.6b02125

Article
pubs.acs.org/IC
3
+
Emission Enhancement and Color Tuning for GdVO :Ln (Ln = Dy,
4
Eu) by Surface Modification at Single Wavelength Excitation
Yan Song, Baiqi Shao, Yang Feng, Wei Lu, Jiansheng Huo, Shuang Zhao, Man Liu, Guixia Liu,*
̈
†
,‡
†
†
†
†
†
†
,‡
,†
and Hongpeng You*
†State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences,
Changchun 130022, P. R. China
‡
Key Laboratory of Applied Chemistry and Nanotechnology at Universities of Jilin Province, Changchun University of Science and
Technology, Changchun 130022, P. R. China
*
S Supporting Information
ABSTRACT: The surface modification can realize systematically the emission
3
+
enhancement of GdVO :Ln (Ln = Dy, Eu) microstructures and multicolor
4
emission at single component. The structure, morphology, composition, and the
surface ligands modification of as-prepared samples were studied in detail. It is
found that the surface-modified ligands can act as sensitizer to improve the
3
+
3+
3−
emission of the Eu and Dy ions via the energy transfer besides the VO4
−
3+
3+
Eu /Dy process. More importantly, under a single wavelength excitation, the
emission color can be effectively tuned by manipulating the doping ratio of the
3+
3+
Eu ions in the internal crystal lattice and the Tb ions in the external surface
ligands, simultaneously. And further, multicolor emissions are obtained unde−r
single wavelength excitation due to the high overlapping between the VO43
absorption and the π−π* electron transition of the ligands. These findings may
open new avenues to design and develop new highly efficient luminescent
materials.
1
. INTRODUCTION
considerable attention in terms of luminescent applications,
1
6−20
specifically, as ideal candidates for light phosphors.
Lanthanide-doped nanocrystalline materials exhibit fascinating
luminescence properties due to the intra 4fN electronic
transition, which offer sharp emission bands, long-lived excited
electronic states, higher photostability, long emission lifetimes,
etc. The luminescence materials have attracted recent interest
in applications of lighting, information display technologies,
solar cells, and especially in biological labeling and biomedical
The nano- and microstructures arouse novel physical
properties and potential applications for luminescent hosts.
Smaller size also results in much more defects and stronger
surface quenching effects due to their high surface-to-volume
1
,2
21,22
ratio.
Higher surface-to-volume ratio of nanomaterials
affects the distribution of phonon energies and increases
quenching sites, which will result in nonradiative transitions
3
−6
imaging technologies.
Particularly, lanthanide-doped nano-
23,24
and luminescence quenching.
In addition, a decrease of
crystalline materials can create a variety of colors by proper
selection of lanthanide dopants, which cover almost the entire
visible spectrum, and multicolor emission could be realized in a
single-phase host matrix,
by proper control of the lanthanide dopants based on variant
particle size leads to an increase in the concentration of dopant
on the outermost surface during the lanthanide ions doping
25−27
processes.
Consequently, there is a higher probability of
7
−10
which can be accurately regulated
the excitation energy loss for the surface dopant ions; for
example, it can cause excitation trap and phonon couple with
solvent molecules, passivating ligands, or surface impurities,
leading to nonradiative relaxation and emission quench-
11,12
characteristic emission bands of different lanthanide ions.
Nowadays, stringent demands for lighting technology require
highly efficient luminescent materials with small size and
various morphologies driven by the nanoscience and nano-
technology. Till now, researchers have successfully developed a
good deal of efficient nanophosphors. Among them, rare-earth
vanadate is a highly efficient luminescent material due to the
21,28,29
ing.
Therefore, we believe that surface activator sites
are important to improve the overall luminescent performance.
Recently, several good strategies have been developed to
promote luminescence intensity of nanoparticles. The construct
of core−shell structure is a convenient and effective strategy
through chemically modifying sensitizing agent on the surface
of luminescence particles or epitaxial growth of a shell layer to
3
4
−
strong absorption of ultraviolet radiation of VO groups and
the efficient energy transfer from VO4 to activator ions, and
3
−
they are widely used in phosphor lamps, polarizers, display
13−15
devices, laser hosts, and catalysts.
Especially, lanthanide
Received: September 6, 2016
activator doped vanadates of Y, La, Gd, and Lu have attracted
©
XXXX American Chemical Society
A
DOI: 10.1021/acs.inorgchem.6b02125
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
3
0−32
passivate the surface.
In addition, some reports have
were collected by centrifugation at 7000 rpm for 5 min and washed at
least twice with deionized water and ethanol. The precipitate was
redispersed in ethanol for further use.
focused on protecting the dopants against surface quenchers by
employing the surface modification, such as host crystalline
shell, amorphous shell, and sensitizer-encapsulated shells.
According to a previous report, ∼25−30% of the dopant ions
were expected to occupy lattice sites on the surface for a 5 nm
particle. To fully utilize the lanthanide-doped ions on the
surface of the nanoparticles and reduce luminescence
quenching, surface modification is a direct and efficacious
strategy to enhance the excitation efficiency for activator. It is
well-established that the organic ligands show strong energy
absorption in the ultraviolet region due to their rich π electrons,
which contribute to efficient charge transport and fast energy
3
+
33−35
2.3. Synthesis of GdVO :Eu /Tb(BA) Phen. In a typical
4
3
3+
synthesis process, the above-synthesized GdVO :Eu (0.5 mmol)
4
ethanol solution was diluted with ethanol to 20 mL, and their pH was
adjusted to 6.5. Then, sodium benzoate (1 mmol) and 1,10-
phenanthroline (3 mmol) was gradually added to the previous
solution under vigorous magnetic stirring. The different concentrations
of Tb(NO ) solution were dropwise added to previous solution to
2
5
3
3
form a homogeneous solution. The reaction mixture was heated at 60
C for 3 h. Subsequently, the solution was cooled to room temperature
°
and kept stirring for 12 h. Afterward, the resulting products were
washed with deionized water and ethanol in turn several times.
2.4. Characterizations. X-ray powder diffraction (XRD) measure-
ments of as-synthesized samples were performed with a Bruker D8
FOCUS diffractometer operated at a voltage of 40 kV and a current of
36−39
transfer between organic ligands and lanthanide ions.
Thus, it is expected that organic ligands are ideal modifications
to efficiently sensitize the surface lanthanide ions and decrease
4
1
0 mA with Cu Kα radiation (λ = 0.154 18 nm) in the 2θ range from
0° to 70°. Scanning electron microscopy (SEM) images and energy-
4
0−43
surface quenching sites.
Furthermore, modifying agent can
act as a platform to induce other lanthanide activators to realize
multicolor emission in a single crystal lattice.
Herein, we developed an efficient strategy of surface
modification with organic ligands to simultaneously achieve
enhancement of the emission intensity and multicolor emission.
dispersive spectroscopy (EDS) were performed using a Hitachi S-4800
field emission scanning electron microscope (FE-SEM) equipped with
an energy-dispersive X-ray spectrometer operating at working voltage
of 10 or 20 kV, and the samples were prepared by dispersing the
samples in ethanol and drop-casting a drop of the suspension on a
smooth silicon wafer. Transmission electron microscope (TEM)
images, high-resolution transmission electron microscope (HRTEM)
images, and selected area electron diffraction (SAED) patterns were
recorded on a JEOL-2010 electron microscope operated at an
accelerating voltage of 200 kV. Samples for TEM were prepared by
dropping from ethanol suspensions onto TEM copper grids covered
with a thin holey carbon film. The elemental mapping analysis of the
samples was performed during TEM measurements to determine the
element distributions of the samples. Fourier transform infrared
spectra (FT-IR) measurements were performed using a Shimadzu
model 8400s FT-IR spectro-photometer in the range of 4000−400
The monodisperse and uniform REVO (RE = La, Y, Gd, Lu)
4
sub-microflowers were synthesized via a hydrothermal method.
REVO4 microstructures were further modified with the
benzoate (BA) and 1,10-phenanthroline (Phen) for effectively
sensitizing the dopant ions. Subsequently, another kind of
doping ions is introduced and coordinated with the surface-
modified ligands. Interestingly, under a single wavelength
excitation at near-ultraviolet region, we achieved an obvious
emission enhancement for the Eu and Dy ions in GdVO4
hosts. In addition, the emission color can be finely adjusted by
rational selection of the lanthanide ions in the building unit.
More importantly, this strategy can be extended to other rare-
earth ion-doped lanthanide vanadates (Y, La, Lu). Such novel
surface modification strategy may provide a new way to
improve the efficiency for luminescence nanocrystals and
extend their applications.
3
+
3+
−1
cm with KBr pellet technique (sample/KBr = 1:100). Thermogravi-
metric analyses (TGA) were performed on a SDT 2960 thermal
analysis instrument with temperature increased linearly by a heating
−1
−1
rate of 10 °C min in an air flow of 100 mL min from room
temperature to 800 °C. The photoluminescence excitation and
emission spectra were recorded at room temperature with Hitachi F-
7000 spectro-photometer equipped with a 150 W xenon lamp as the
excitation source with photomultiplier tube voltage of 700 V and the
instrument parameters of 2.5 nm for excitation emission slits. The
photoluminescence quantum efficiency was measured using an
absolute photoluminescence quantum yield measurement system
(C9920−02, Hamamatsu Photonics K. K., Japan).
2
. EXPERIMENTAL SECTION
2
.1. Materials. Gadolinium oxide (Gd O , 99.99%), yttrium oxide
2 3
(
(
(
Y O , 99.99%), lanthanum oxide (La O , 99.99%), lutetium oxide
2
3
2
3
Lu O , 99.99%), europium oxide (Eu O , 99.99%), terbium oxide
Tb O , 99.99%), and dysprosium oxide (Dy O , 99.99%) were
purchased from Shanghai Yuelong Non-Ferrous Metals Limited.
2
3
2
3
4
7
2
3
3
. RESULTS AND DISCUSSION
Ammonium metavanadate (NH VO ), sodium citrate, BA, and Phen
3.1. Structure, Morphology, and Composition of the
4
3
were purchased from Sinopharm Chemical Reagent Co., Ltd. All the
chemicals in this investigation were of analytical grade and used
without further purification.
Samples. The crystal structure and phase purity of the as-
prepared samples were first examined by XRD. The
corresponding XRD patterns of the as-prepared samples and
Rare-earth nitrate (RE(NO ) ) stock solutions were obtained by
3
3
standard card data of GdVO crystal were provided in Figure 1.
4
dissolving the corresponding rare-earth oxides in dilute HNO under
3
All of the diffraction peaks can be readily indexed to pure
heating with agitation followed by evaporating the solvent.
3+
3+
tetragonal phase of GdVO , and the locations and relative
2
.2. Synthesis of GdVO :Ln (Ln = Eu, Dy). The GdVO :Ln
4
4
4
(
Ln = Eu, Dy) sub-microflowers were synthesized via a hydrothermal
intensities of the diffraction peaks coincide well with the
standard card (PDF No. 17−0260) without any impurity phase.
For the surface-modified samples, an additional amorphous
phase can be observed on the baseline at the low-angle region,
which may be caused by the BA and Phen and formation of
3+
route. In the typical procedures of preparing GdVO :Ln sub-
microflowers, the stoichiometric amounts of the 1.0 mmol RE(NO )
4
3
3
3+
3+
solutions (molar ratio Gd :Ln = 95:5) was added into 30 mL of
deionized water at room temperature under vigorous magnetic stirring
to form a homogeneous solution. Subsequently, 1.0 mmol of sodium
citrate was introduced, and the solution was constantly vigorously
stirred for 30 min. After addition of 1.0 mmol of ammonium
metavanadate (NH VO ), the resulting solution was stirred and
transferred into a 50 mL Teflon bottle held in a stainless steel
autoclave. The autoclave was maintained at 180 °C for 10 h. As the
autoclave was cooled to room temperature naturally, the final products
amorphous complex on the surface of GdVO crystals. The
4
results indicate that the surface-modified ligands have no
obvious effect on the crystal phase structure of samples. The
4
3
3
+
XRD profiles of as-synthesized GdVO :Dy nanocrystals and
4
surface-modified GdVO
:Dy3+ sub-microflowers are shown in
4
Figure S1. The patterns of as-synthesized samples match well
B
DOI: 10.1021/acs.inorgchem.6b02125
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
dimensions. Figure 2d,e shows the morphology for the
3
+
GdVO :Eu with modification of Tb(BA) Phen complex.
4
3
3+
Compared with the morphology of GdVO :Eu , the surfaces
of the modified GdVO :Eu sub-microflowers are coated with
4
3+
4
amorphous complex, corresponding to the Tb(BA) Phen.
3
Furthermore, Figure 2c,f represents the EDX spectra of
3
+
3+
GdVO :Eu and GdVO :Eu /Tb(BA) Phen samples. In the
4
4
3
3+
EDX spectrum of GdVO :Eu (Figure 2c), the peaks of Gd, V,
4
O, and Eu elements can be detected. After modified with BA
and Phen ligands, the EDX spectrum (Figure 2f) shows the
presence of C, N, and Tb besides the elements of Gd, V, O, and
Eu elements, suggesting the successful modification.
Figure 3 shows the TEM images, SAED pattern, and EDX
3+
3+
elemental mappings of the GdVO :Eu and GdVO :Eu /
4
4
Tb(BA) Phen samples. The TEM image confirms the
3
3
+
monodispersity and relatively uniform size and morphology.
High-magnification TEM image taken in the Figure 3b shows
that the microflower consists of many layers of nano sheetlike
structure and that it has a well-defined crystalline structure with
a lattice plane spacing of 0.36 nm, which is consistent with the
Figure 1. XRD patterns of GdVO :Eu sub-microflowers (a),
4
3+
3+
GdVO :Eu modified with BA and Phen (b), and GdVO :Eu /
Tb(BA) Phen (c) samples. The standard card of GdVO (PDF No.
4
4
3
4
1
7−0260) was given as reference.
(
200) facet of GdVO . The corresponding SAED pattern
with the tetragonal phase of GdVO crystal, and no extra
4
4
displays discontinuous rings and the lattice plane spacing that
match well with the d-spacing values of the (200), (211), (220),
and (103) planes of GdVO , revealing that the samples consist
of polycrystals with an oriented crystallographic axis. To verify
the successful modification of complex on the surface of
GdVO :Eu
GdVO :Eu /Tb(BA) Phen samples was studied with EDX
elemental mappings (Figure 3e). The elemental mappings show
that C, N, Tb, Gd, V, O, and Eu element are detected and C, N,
Tb distributed throughout particle, suggesting that Tb-
(BA)
GdVO
LuVO
BA and Phen were also characterized under the same condition
by SEM. The results show that they have a homologous shape
with an average size of ∼400 nm and that the BA and Phen
ligands are modified successfully, as displayed in Figures S3−S5
(Supporting Information).
diffraction peak is observed after Eu(BA) Phen modification on
3
3+
the GdVO :Dy crystals. In addition, the crystal phases of as-
synthesized LnVO :Eu (Ln = Y, La, Lu) sub-microflowers
4
3
+
4
4
with and without surface modification also were detected by
XRD. As shown in Figure S2, all of the diffraction peaks can be
readily indexed to a tetragonal structure YVO , LaVO , and
3
+
sample, the distribution of elements of
4
4
4
3+
LuVO according to the International Centre for Diffraction
4
3
4
Data (ICDD) powder diffraction file PDF cards 72−0274, 70−
5
226, and 17−0880, respectively.
The morphologies, size, and structure of the as-synthesized
3+
GdVO :Eu samples with or without modification of BA and
3
Phen is successfully modified on the surface of
4
3
+
3+
3+
Phen ligands were characterized by SEM, TEM, and EDX
measurements, as displayed in Figures 2 and 3. The as-
4
:Eu samples. The YVO
4 4
:Eu , LaVO :Eu , and
:Eu3+ sub-micrometer structures with surface-modified
4
3
+
synthesized GdVO :Eu (Figure 2a) consists of highly
4
monodisperse and uniform sub-microflowers with size in the
range of 400−500 nm. The high-magnification SEM image
(
Figure 2b) shows that the sub-microflower is composed of
compact nanoplatelets packed aligned regularly in three
Figure 2. SEM images of GdVO :Eu3 (a, b) and GdVO :Eu /Tb(BA) Phen (d, e). EDX spectrum of GdVO :Eu (c) and GdVO :Eu /
+
3+
3+
3+
4
4
3
4
4
Tb(BA) Phen (f) sub-microflowers.
3
C
DOI: 10.1021/acs.inorgchem.6b02125
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
3+
Figure 3. TEM image, HRTEM image, and SAED pattern of GdVO :Eu (a−c), TEM image (d), and EDX elemental mappings (e) of
4
3+
GdVO :Eu /Tb(BA) Phen sub-microflowers.
4
3
FT-IR spectroscopy was performed to demonstrate the
is ascribed to the V−O bond stretching vibration from the
3−
successful modification of BA and Phen ligands on the surface
VO group. Moreover, the two bands centered at ∼1410 and
4
3+
−1
of GdVO :Eu samples. Figure 4 shows the typical FT-IR
1521 cm correspond to the symmetrical (v ) and asym-
4
s
metrical (v ) vibration modes of carboxyl (−COO−) groups,
as
respectively. We could also observe a clear change at 1072,
−
1
8
50.3, and 718.9 cm , which corresponds to stretching
frequency of the carbon−nitrogen double bond (CN) in
the Phen ligand and the N−CH scissoring mode. In addition,
3
−1
the broad band centered at 3400 cm can be attributed to the
characteristic hydroxyl group (O−H) stretching vibration of
H O molecule.
2
To further determine the successful modification and
investigate the thermal stability after modification, TGA is
performed from room temperature to 800 °C with a heating
rate of 10 °C min− in air. Figure 5 illustrates the TGA curves
1
3+
Figure 4. FT-IR spectral profiles for the GdVO :Eu (a) and
4
3+
GdVO :Eu /Tb(BA) Phen (b).
4
3
3
+
3+
spectra of as-formed GdVO :Eu samples and GdVO :Eu /
4
4
Tb(BA) Phen samples, respectively. The FT-IR spectrum of
3
3
+
the GdVO :Eu sample (Figure 4a) displays a strong
absorption band at 820 cm and a weak peak at 450 cm ,
4
−1
−1
which are attributed to the vibration of the V−O bond and the
3
+
Gd−O (Eu−O) bond from the Eu ion-doped GdVO crystal
4
structure, respectively. In addition, the broad absorption band
3+
3+
around 3400 cm− and the peak centered at ∼1600 cm are
1
−1
4
3
4
Figure 5. TGA data of GdVO :Eu , Tb(BA) Phen, and GdVO :Eu /
Tb(BA) Phen.
ascribed to the stretching and bending vibrations of the
3
hydroxyl groups (O−H) from surface absorbent H O molecule.
2
3
+
In the FT-IR spectrum of Tb(BA) Phen (Figure S6, Supporting
of the pure GdVO :Eu , Tb(BA) Phen complex, and
4 3
3
3+
Information), the characteristic vibration modes, corresponding
GdVO :Eu /Tb(BA) Phen samples. There is no obvious
4 3
to N−CH , − COO−, CC, and C−H group stretching
weight loss from the room temperature to 800 °C except for
3
vibrations from benzene ring, originate from the complex. After
the volatilization of water in the TGA curve for the
3+
3+
the Tb(BA) Phen are modified on the surface of GdVO :Eu ,
GdVO :Eu samples. However, three distinct stages of weight
3
4
4
3
+
the FT-IR spectrum of GdVO :Eu /Tb(BA) Phen samples
exhibit that the strong absorption band centered at ∼820 cm
loss are observed for the Tb(BA) Phen complex. The first
4
3
3
−1
weight loss is shown in the temperature range of 30−110 °C
D
DOI: 10.1021/acs.inorgchem.6b02125
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
due to the loss of absorbed water. In addition, the second
weight loss starting at ∼250 °C can be attributed to almost
complete decomposition of Phen ligands in the complex. The
subsequent process is observed at 560 °C, which can be
wavelength, which will achieve tunable emitting colors through
controlling the concentration of activator. The photolumines-
3
+
cence excitation and emission spectra of the GdVO :Dy sub-
4
microflowers and Eu(BA) Phen complex are given in Figure 7.
3
assigned to the pyrolysis of the Tb(BA) complex and the loss
3
of benzoate ligands. After introduction of complex in the
3
+
GdVO , the GdVO :Eu /Tb(BA) Phen composites have the
4
4
3
high thermal stability without loss of weight below 300 °C.
When the temperature is headed up to 300 °C and above 500
°
C, the obvious weight losses are around 6.9% and 14.3%,
which are assigned to the pyrolysis of Phen ligands and
benzoate ligands, respectively. As a result, it further indicates
that the complexes are successfully modified on the surface of
3+
GdVO :Eu samples.
4
3
.2. Photoluminescence Properties of the Samples.
Figure 6 gives the photoluminescence excitation and emission
Figure 7. Excitation and emission spectra of the Eu(BA) Phen
3
3+
complex (a) and GdVO :Dy (b).
4
The excitation spectrum (Figure 7b) consists of a strong broad
absorption from 200 to 350 nm. This broad absorption is
ascribed to the charge transfer from the oxygen ligands to the
central vanadium ions inside the VO43 groups. In the Figure
−
7
a, the broad band from π−π* electron transition of the
Eu(BA) Phen complex is located in close proximity with that of
3
VO43 groups. As is expected, after modified with Eu-
−
(
BA) Phen complex, the composites will display color emission
3
3+
3+
of the Dy and Eu ions excited under a single wavelength.
Figure 6. Excitation and emission spectra of the Tb(BA) Phen
3
Figure 8a shows the photoluminescence excitation spectra of
3+
complex (a) and GdVO :Eu (b).
3+
4
the GdVO :Eu samples with or without modified BA and
4
Phen ligands at the room temperature. By contrast, a significant
enhancement was observed for the surface modification
samples. Moreover, monitored the characteristic emission of
the Eu3+ ions at 619 nm, the excitation spectrum of the
3
+
spectra of GdVO :Eu sub-microflower and Tb(BA) Phen
4
3
complex recorded at room temperature. One can notice that
the Tb(BA) Phen complex displays the characteristic green
3
3
+
3+
3+
emission from the Tb ions and that the GdVO :Eu displays
GdVO :Eu /(BA) Phen samples contains a broader excitation
4
4
3
3
+
the sharp red emission of the Eu ions. Monitored at the
respective characteristic emission peaks of the Tb and Eu
ions, the excitation spectra of Tb(BA) Phen complex and
GdVO :Eu materials were achieved, respectively. For Tb-
BA) Phen complex, the excitation spectrum exhibits a broad
band from 200 to 400 nm, which is attribution to the π−π*
electron transition of greater π bond conjugated system from
the benzene ring and the n−π* electron transitions of the N
atom in the azomethine group from the ligand of Phen. The
excitation spectrum of GdVO :Eu consists of a strong
absorption band ranging from 200 to 350 nm with a maximum
peak at 290 nm due to the charge transfer from the oxygen
band ranging from 200 to 375 nm. The phenomena indicate
3
+
3+
3+
that the energy of activator (Eu ) derives from the GdVO
4
matrix and the surface modified BA and Phen ligands. The
respective emission spectra were obtained under the excitation
of 290 nm, and they present identical profiles except for the
intensity. Thus, the introducing of ligands can effectively
3
3+
4
(
3
3+
improve the emission of GdVO :Eu samples. Figure 8b shows
4
the photoluminescence excitation and emission spectra of the
3
+
3+
GdVO :Dy and GdVO :Dy /(BA) Phen samples. Moni-
4
4
3
3
+
3+
tored the emission of the Dy ions at 574 nm, a broader
excitation band is also observed, associated with the VO4
4
3
−
groups absorption and the π−π* electron transition of the
3
−
3+
ligands to the central vanadium ions inside the VO4 groups.
By comparative investigation of the excitation spectra for both−
samples, there is a distinct overlap between the VO43
absorption band and the π−π* electron transition of the
ligands. Meanwhile, the emission intensity of the Dy ions
obviously enhances due to sensitization effect of the surface
modification ligands. In addition, the same situation can be
observed for doped YVO , LaVO , and LuVO samples, as
4
4
4
3
+
complex. Therefore, the samples GdVO :Eu with surface
shown in Figures S7−S9. Similar results reveal that
modification ligands can effectively improve the emission
intensity.
4
modified with Tb(BA) Phen complex can achieve excitation
3
energy through double ways upon excitation at 290 nm due to
3
−
the absorption of VO4 groups and the ligands, which may
On the basis of the above research, we also expect that the
effectively enhance the emission of active lanthanide ion (Eu3
+
combination of the GdVO :Eu and Tb(BA) Phen will
3+
4
3
ions) from the GdVO matrix. More importantly, we expect
generate tunable color emission. Figure 9 shows the variation
of photoluminescence emission spectra of and emission
4
that the composite exhibits the characteristic emission of the
3+
3+
3+
3+
Eu and Tb ions simultaneously at the excitation of single
intensity of the Tb ions in the GdVO :Eu /Tb(BA) Phen
4 3
E
DOI: 10.1021/acs.inorgchem.6b02125
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
5
5
7
5
7
5
7
5
7
5
7
D → F , D → F , D → F , D → F , D → F , and
1
1
1
2
0
1
0
2
0
3
7
3+
D → F radiation transitions of the Eu ions, respectively.
0
4
3+
After introduction of Tb ions by Tb(BA) Phen on the
3
surface, the sharp characteristic emission peaks are displayed
and centered at 492, 547, and 589 nm, which are attributed to
5
7
3+
the D → F (J = 6, 5, 4) radiation transitions of the Tb ions,
4
J
3+
3+
respectively. When the samples contain Tb and Eu ions, the
emission spectra of all samples involve the characteristic
3+
3+
emission peaks of the Tb and Eu ions. The emission spectra
of all samples have similar emission wavelengths but different
relative emission intensities depending on the relative content
of Tb3+ and Eu ions. With an increase in the Tb
3+
3+
3+
concentration, the emission intensity of the Tb ions increases
3
+
systematically, while the emission intensity of the Eu ions
shows no relative change. The results indicate that the tunable
emission colors can be realized by adjusting different amounts
3+
of the green color emission from the Tb and red color
emission from the Eu3+ in the GdVO :Eu /Tb(BA) Phen
3+
4
3
samples. As an important parameter for phosphors, the
quantum efficiency was also measured. The measured quantum
3
+
efficiencies of GdVO :Eu /Tb(BA) Phen samples with the
4
3
increase of Tb3+ content are determined to be 10.6%, 17.3%,
8.5%, 35.9%, 42.5%, 50.7%, and 62.9% at 290 nm excitation.
2
3
+
To elucidate the energy transfer mechanism of the Eu and
Tb3 photoluminescence emission, the excitation spectra of the
+
3+
GdVO :Eu /Tb(BA) Phen sample (A6 sample) were studied,
4
3
as displayed in Figure 10. The excitation spectrum of the
3
+
Figure 8. Excitation and emission spectra of the GdVO :Eu (a) and
4
3+
GdVO :Dy (b) with or without surface modification of BA and
4
Phen.
3+
Figure 10. Excitation spectra of the GdVO :Eu /Tb(BA) Phen by
4
3
monitoring the wavelength at 619 and 545 nm.
3
+
GdVO :Eu /Tb(BA) Phen samples monitored at the
4
3
5
7
D → F transition (at 619 nm) consists of strong and broad
0
2
excitation band ranging from 200 to 375 nm, which contains
the VO43 absorption and the π−π* electron transition of the
−
3+
ligands. This result suggests that the Eu ions are excited
through the energy transfer from the GdVO host and the
4
5
7
surface-modified ligands. While monitored at the D → F
4
5
transition of the Tb3+ ions (at 545 nm), the excitation
spectrum exhibits a broad band ranging from 200 to 400 nm
with centers at 292 nm. The excitation band is similar to the
3+
Figure 9. Emission spectra of the GdVO :Eu /Tb(BA) Phen with
4
3
various Tb3 content under 290 nm excitation.
+
photoluminescence excitation spectrum of the Tb(BA) Phen
3
complex (Figure 6a), which is attributed to the π−π* electron
transition of the benzene ring and the n−π* electron
transitions of the Phen ligands. These results clearly indicate
that the Tb ions are excited just through the energy transfer
from the surface-modified ligands.
samples with the variation of Tb3+ content (0, 0.1, 0.2, 0.4, 0.6,
.8, and 1.0 mmol), respectively. Upon excitation at 290 nm,
0
3
+
3+
the characteristic emission peaks of the Eu ions at 538, 559,
92, 619, 652, and 700 nm are detectable, corresponding to the
5
F
DOI: 10.1021/acs.inorgchem.6b02125
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
To achieve a gradual color change from blue-green toward
3
+
yellow, we regulated the Eu ion content (0, 0.1, 0.2, 0.4, 0.6,
.8, and 1.0 mmol) in the fabrication process of the
0
3+
GdVO :Dy /Eu(BA) Phen sample. Figure 11 provides the
4
3
3
+
Figure 12. Photoluminescence excitation spectra of the GdVO :Dy /
4
Eu(BA) Phen by monitoring the wavelength at 619 and 574 nm.
3
illustrated in Figure S10. Upon excitation at 290 nm, the
1
electrons are excited to the excited-state T level and then
2
1
relaxed to the T level. After that, the energy transfer occurs
1
1
3−
5
3+
from the T level of VO to the H excited level of the Eu
1
4
J
3+
3+
ion. For the GdVO :Dy /Eu(BA) Phen, the energy transfer
4 3
Figure 11. Emission spectra of the GdVO :Dy /Eu(BA) Phen with
4
3
1
3−
4
various Eu3 content under 290 nm excitation.
+
occurs from the T level of VO to the I excited level of
1 4 9/2
the Dy3+ ion, while the S −S transition first occurred in the
0
1
outer complex and then populated to T1 by intersystem
crossing. Subsequently, the energy transfers from the T level of
variation of photoluminescence spectra and emission intensity
of Eu3 in the GdVO :Dy /Eu(BA) Phen sample with the
+
3+
1
4
3
5
3+
5
3+
the ligands to the D excited level of the Tb ions and D
increase of Eu content from 0 to 1.0 mmol. Obviously, the
4
2
3+
excited level of the Eu ions, respectively. Finally, the electrons
fall back to lower energy levels and cause different emissions.
According to the photoluminescence emission spectra of the
samples, the color tuning can be realized through simply
changing the active lanthanide ion ratios in the single particle.
In the following, we investigate the chromaticity coordinates
and optical color of all samples. Figure 13 shows the emission
colors optical photographs and the chromaticity coordinates in
sharp characteristic peaks located at ∼482 and 574 nm are
4
6
ascribed to the magnetic dipole transition ( F → H ) and
9
/2
15/2
4
6
the hypersensitive electric dipole transition ( F → H13/2) for
9
/2
the Dy3 ions. The sharp peaks centered at 592 and 619 nm
+
5
7
5
7
originate from the D → F and D → F transitions of the
0
1
0
2
3+
3+
Eu ions, respectively. With increasing Eu content, the
3
+
emission intensity of the Eu raises monotonically leading to
the gradual change in emission color. In addition, upon
3+
excitation at 290 nm, the quantum efficiencies of GdVO :Dy /
4
3
+
Eu(BA) Phen samples with the increase of Eu content were
3
determined to be 8.2%, 12.7%, 19.5%, 28.5%, 35.6%, 42.7%,
and 49.2%, respectively.
Similarly, we investigate the energy transfer between
3
+
activator and sensitizer in the GdVO :Dy /Eu(BA) Phen
4
3
samples. Figure 12 shows the photoluminescence excitation
3
+
3+
spectra though monitoring the Dy and Eu characteristic
emission at 574 and 619 nm, respectively. The excitation
3
+
spectrum of GdVO :Dy /Eu(BA) Phen samples monitored at
4
3
5
74 nm consists of strong and broad excitation band ranging
3
−
from 200 to 350 nm, which are attributed to the VO4
absorption and the π−π* electron transition of the ligands.
These results suggest that the excited energy can be transferred
from the GdVO host and the surface-modified ligands to the
4
3+
3+
Dy ions. When monitored at 619 nm of the Eu ions, the
excitation spectra of the GdVO :Dy /Eu(BA) Phen shows a
3
+
4
3
broad band around 300 nm and a sharp peak at 394 nm, which
are related to the electron transition of the ligands and the f−f
7
5
3+
transition ( F → L ) of the Eu ions, respectively. It indicates
0
6
that the Eu3 ions are essentially excited through the energy
+
transfer from the surface-modified ligands.
On the basis of the excitation and emission spectra, the
3
+
schematic of the energy transfers in GdVO :Eu /Tb-
Figure 13. CIE chromaticity coordinates and digital camera image for
luminescence of a series of samples of CIE chromaticity diagram.
4
3
+
(
BA) Phen and GdVO :Dy /Eu(BA) Phen samples are
3
4
3
G
DOI: 10.1021/acs.inorgchem.6b02125
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
the 1931 Commission Internationale de L’Eclairage (CIE)
diagram. It can be seen that the emitting color of the phosphors
can be easily modulated from red to yellow by simply varying
the content of Tb3+ from 0.1 to 1.0 mmol. As expected, the
emitting color of the samples can be easily modulated from
orange-red region to yellow-green region with the increase of
4. CONCLUSIONS
In summary, we have developed a novel strategy to efficiently
enhance the emission intensity and tune the emission color for
3+
3+
a series of lanthanide ion (Eu , Dy )-doped vanadate
REVO , RE = Y, La, Gd and Lu) sub-microflowers via a
(
4
surface modification process. The BA and Phen ligands are
modified to the surface of vanadate sub-microflowers, and the
different doping ions then are bonded with the surface ligands.
The surface-modified ligands could act as sensitizer to enhance
3+
3+
Tb ions in the GdVO :Eu /Tb(BA) Phen system. Moreover,
4
3
similar results about color tuning can be accomplished when
3
+
3+
the Eu and Dy ions serve as activator. The CIE chromaticity
3
+
coordinates of all GdVO :Dy /Eu(BA) Phen samples show a
3+
3+
4
3
the emission of the Eu and Dy ions via the energy transfer
distinct shift of color position from bluish-green region to
3−
3+
3+
besides the VO4 −Eu /Dy process. Moreover, the emission
color can be adjusted from blue and bluish-green to green and
yellow region by manipulating the doping ratio at single
wavelength excitation. The tunable photoluminescent proper-
ties of samples show their great potential application in
multicolor luminescence devices.
3
+
yellow region with the increase of Eu content. The CIE
chromaticity coordinates of all samples are listed in Table 1.
Table 1. CIE Chromaticity Coordinates of Samples
sample
CIE coordinates (x, y)
sample
CIE coordinates (x, y)
A1
A2
A3
A4
A5
A6
A7
(0.599, 0.336)
(0.560, 0.365)
(0.532, 0.395)
(0.483, 0.424)
(0.454, 0.457)
(0.423, 0.472)
(0.396, 0.487)
B1
B2
B3
B4
B5
B6
B7
(0.355, 0.385)
(0.324, 0.367)
(0.329, 0.362)
(0.371, 0.368)
(0.395, 0.375)
(0.437, 0.370)
(0.468, 0.368)
ASSOCIATED CONTENT
Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.inorg-
chem.6b02125.
■
*
S
3+
Listings of XRD patterns of GdVO :Dy with or without
4
modification complex; FT-IR spectrum of pure Tb-
The related tunable colors are visibly demonstrated by the
digital camera images of all samples under ultraviolet light
exposure, which vividly reflect the color modulation. To verify
the photoluminescence stability, the dependence of emission
intensity on irradiation time was studied for the A7 and B7
samples. Figure 14 displays the dependence of the normalized
(BA) Phen; XRD patterns, SEM images, excitation and
3
3+
3+
emission spectra of the REVO :Eu and REVO :Dy
4
4
(RE = Y, La, Lu) with or without modification
(BA) Phen complex; schematic of energy transfer
3
3
+
mechanism in GdVO :Eu /Tb(BA) Phen and
GdVO :Dy /Eu(BA) Phen samples (PDF)
4
3
3+
4
3
AUTHOR INFORMATION
Corresponding Authors
E-mail: liuguixia22@163.com.
E-mail: hpyou@ciac.ac.cn.
■
*
*
ORCID
Hongpeng You: 0000-0003-2683-6896
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
This work was financially supported by the National Natural
Science Foundation of China (Grant Nos. 21271167 and
■
5
1472236) and the Fund for Creative Research Groups (Grant
No. 21521092), the National Basic Research Program of China
973 Program, Grant No. 2014CB643803), and Key Program
of the Frontier Science of the Chinese Academy of Sciences
Figure 14. Dependence of the normalized emission intensity of the
(
5
7
3+
5
7
3+
D → F (Eu ) and D → F (Tb ) transition on irradiation time for
0
2
4
5
3+
3+
GdVO :Eu /Tb(BA) Phen and GdVO :Eu /Tb(BA) Phen samples.
4
3
4
3
(
Grant No. YZDY-SSW-JSC018).
REFERENCES
■
5
7
3+
5
7
3+
(1) Gai, S.; Li, C.; Yang, P.; Lin, J. Recent Progress in Rare Earth
emission intensity of the D → F (Tb ) and D → F (Eu )
4
5
0
2
Micro/Nanocrystals: Soft Chemical Synthesis, Luminescent Proper-
ties, and Biomedical Applications. Chem. Rev. 2014, 114, 2343−2389.
(2) Liu, Y.; Tu, D.; Zhu, H.; Chen, X. Lanthanide-doped luminescent
nanoprobes: controlled synthesis, optical spectroscopy, and bioappli-
cations. Chem. Soc. Rev. 2013, 42, 6924−6958.
3) Bunzli, J.-C. G. Lanthanide Luminescence for Biomedical
̈
Analyses and Imaging. Chem. Rev. 2010, 110, 2729−2755.
4) Dong, H.; Du, S.-R.; Zheng, X.-Y.; Lyu, G.-M.; Sun, L.-D.; Li, L.-
3
+
transitions on irradiation time for GdVO :Eu /Tb(BA) Phen
and GdVO :Eu /Tb(BA) Phen samples, respectively. It is
4
3
3+
4
3
interesting to observe that the emission intensity gradually
increases in the incipient stage of exposure time and then
maintains constant. The intensity enhancement with exposure
time can be attributed to optical modification of the surface
defects. These results show that the samples have good
photostability, which is a favorable performance for application
in display devices.
(
(
D.; Zhang, P.-Z.; Zhang, C.; Yan, C.-H. Lanthanide Nanoparticles:
From Design toward Bioimaging and Therapy. Chem. Rev. 2015, 115,
10725−10815.
H
DOI: 10.1021/acs.inorgchem.6b02125
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
(
5) Zheng, W.; Huang, P.; Tu, D.; Ma, E.; Zhu, H.; Chen, X.
upconversion nanocrystals through lanthanide doping. Nature 2010,
463, 1061−1065.
Lanthanide-doped upconversion nano-bioprobes: electronic structures,
optical properties, and biodetection. Chem. Soc. Rev. 2015, 44, 1379−
(23) Xue, M.; Zhu, X.; Qiu, X.; Gu, Y.; Feng, W.; Li, F. Highly
Enhanced Cooperative Upconversion Luminescence through Energy
Transfer Optimization and Quenching Protection. ACS Appl. Mater.
Interfaces 2016, 8, 17894−17901.
1
415.
(
6) Zhang, X.; Yu, J.; Wang, J.; Zhu, C.; Zhang, J.; Zou, R.; Lei, B.;
Liu, Y.; Wu, M. Facile Preparation and Ultrastable Performance of
Single-Component White-Light-Emitting Phosphor-in-Glass used for
High-Power Warm White LEDs. ACS Appl. Mater. Interfaces 2015, 7,
(24) Stouwdam, J. W.; van Veggel, F. C. J. M. Improvement in the
Luminescence Properties and Processability of LaF /Ln and LaPO /
3
4
2
(
8122−28127.
Ln Nanoparticles by Surface Modification. Langmuir 2004, 20,
1763−11771.
25) Lehmann, O.; Ko
7) Dai, P.-P.; Li, C.; Zhang, X.-T.; Xu, J.; Chen, X.; Wang, X.-L.; Jia,
1
(
2+
Y.; Wang, X.; Liu, Y.-C. A single Eu -activated high-color-rendering
oxychloride white-light phosphor for white-light-emitting diodes.
Light: Sci. Appl. 2016, 5, e16024.
3+
̈
mpe, K.; Haase, M. Synthesis of Eu -Doped
Core and Core/Shell Nanoparticles and Direct Spectroscopic
Identification of Dopant Sites at the Surface and in the Interior of
the Particles. J. Am. Chem. Soc. 2004, 126, 14935−14942.
(
8) Liu, Y.; Liu, G.; Wang, J.; Dong, X.; Yu, W. Single-Component
3+
3+
3+
and Warm-White-Emitting Phosphor NaGd(WO ) :Tm , Dy , Eu :
4
2
(26) Wang, F.; Wang, J.; Liu, X. Direct Evidence of a Surface
Synthesis, Luminescence, Energy Transfer, and Tunable Color. Inorg.
Chem. 2014, 53, 11457−11466.
Quenching Effect on Size-Dependent Luminescence of Upconversion
Nanoparticles. Angew. Chem., Int. Ed. 2010, 49, 7456−7460.
(
̈
9) Shao, B.; Feng, Y.; Song, Y.; Jiao, M.; Lu, W.; You, H. Topotactic
(27) Wang, F.; Liu, X. Multicolor Tuning of Lanthanide-Doped
3+
Transformation Route to Monodisperse β-NaYF :Ln Microcrystals
4
Nanoparticles by Single Wavelength Excitation. Acc. Chem. Res. 2014,
7, 1378−1385.
28) Su, Q.; Han, S.; Xie, X.; Zhu, H.; Chen, H.; Chen, C.-K.; Liu, R.-
with Luminescence Properties. Inorg. Chem. 2016, 55, 1912−1919.
(
Multicolor Barcoding in a Single Upconversion Crystal. J. Am. Chem.
Soc. 2014, 136, 4893−4896.
(
Synthesis, Optical-Magnetic Properties, and Applications. Acc. Chem.
Res. 2011, 44, 322−332.
(
Linear Dependence of Photoluminescence in Mixed Ln-MOFs for
Color Tunability and Barcode Application. Inorg. Chem. 2015, 54,
4
(
10) Zhang, Y.; Zhang, L.; Deng, R.; Tian, J.; Zong, Y.; Jin, D.; Liu, X.
S.; Chen, X.; Wang, F.; Liu, X. The Effect of Surface Coating on
Energy Migration-Mediated Upconversion. J. Am. Chem. Soc. 2012,
11) Wang, G.; Peng, Q.; Li, Y. Lanthanide-Doped Nanocrystals:
1
(
34, 20849−20857.
29) Huang, B.; Dong, H.; Wong, K.-L.; Sun, L.-D.; Yan, C.-H.
Fundamental View of Electronic Structures of β-NaYF , β-NaGdF ,
12) Yang, Q.-Y.; Pan, M.; Wei, S.-C.; Li, K.; Du, B.-B.; Su, C.-Y.
4
4
and β-NaLuF . J. Phys. Chem. C 2016, 120, 18858−18870.
4
(
30) Luwang, M. N.; Ningthoujam, R. S.; Srivastava, S. K.; Vatsa, R.
3+
K. Preparation of white light emitting YVO : Ln and silica-coated
YVO
5
(
707−5716.
13) Abdesselem, M.; Schoeffel, M.; Maurin, I.; Ramodiharilafy, R.;
Autret, G.; Clement, O.; Tharaux, P.-L.; Boilot, J.-P.; Gacoin, T.;
4
:Ln3 (Ln = Eu , Dy , Tm ) nanoparticles by CTAB/n-
+
3+
3+
3+
3+
4
́
butanol/hexane/water microemulsion route: Energy transfer and site
symmetry studies. J. Mater. Chem. 2011, 21, 5326−5337.
(31) Wang, L.; Li, Q.; Wang, H.-Y.; Huang, J.-C.; Zhang, R.; Chen,
Q.-D.; Xu, H.-L.; Han, W.; Shao, Z.-Z.; Sun, H.-B. Ultrafast optical
spectroscopy of surface-modified silicon quantum dots: unraveling the
underlying mechanism of the ultrabright and color-tunable photo-
luminescence. Light: Sci. Appl. 2015, 4, e245.
Bouzigues, C.; Alexandrou, A. Multifunctional Rare-Earth Vanadate
Nanoparticles: Luminescent Labels, Oxidant Sensors, and MRI
Contrast Agents. ACS Nano 2014, 8, 11126−11137.
(
14) Hou, Z.; Yang, P.; Li, C.; Wang, L.; Lian, H.; Quan, Z.; Lin, J.
Preparation and Luminescence Properties of YVO :Ln and Y(V,
4
3+
3+
3+
P)O :Ln (Ln = Eu , Sm , Dy ) Nanofibers and Microbelts by Sol−
4
Gel/Electrospinning Process. Chem. Mater. 2008, 20, 6686−6696.
(32) Prorok, K.; Pawlyta, M.; Stręk, W.; Bednarkiewicz, A. Energy
Migration Up-conversion of Tb3 in Yb and Nd Codoped Active-
Core/Active-Shell Colloidal Nanoparticles. Chem. Mater. 2016, 28,
2295−2300.
+
3+
3+
(
15) Zheng, Y.; You, H.; Jia, G.; Liu, K.; Song, Y.; Yang, M.; Zhang,
H. Facile Hydrothermal Synthesis and Luminescent Properties of
Large-Scale GdVO :Eu Nanowires. Cryst. Growth Des. 2009, 9,
3+
4
5
(
101−5107.
16) Szczeszak, A.; Grzyb, T.; Sniadecki, Z.; Andrzejewska, N.; Lis, S.;
Matczak, M.; Nowaczyk, G.; Jurga, S.; Idzikowski, B. Structural,
(
33) Yuan, P.; Lee, Y. H.; Gnanasammandhan, M. K.; Guan, Z.;
́
Zhang, Y.; Xu, Q.-H. Plasmon enhanced upconversion luminescence
of NaYF :Yb,Er@SiO @Ag core-shell nanocomposites for cell
4
2
3
+
Spectroscopic, and Magnetic Properties of Eu -Doped GdVO
4
imaging. Nanoscale 2012, 4, 5132−5137.
Nanocrystals Synthesized by a Hydrothermal Method. Inorg. Chem.
014, 53, 12243−12252.
17) Yu, C.; Yu, M.; Li, C.; Zhang, C.; Yang, P.; Lin, J. Spindle-like
(
34) Zhang, Y.; Liu, X.; Lang, Y.; Yuan, Z.; Zhao, D.; Qin, G.; Qin,
2
(
3+
3+
3+
W. Synthesis of ultra-small BaLuF :Yb ,Er @BaLuF :Yb active-
5
5
core-active-shell nanoparticles with enhanced up-conversion and
down-conversion luminescence by a layer-by-layer strategy. J. Mater.
Chem. C 2015, 3, 2045−2053.
Lanthanide Orthovanadate Nanoparticles: Facile Synthesis by Ultra-
sonic Irradiation, Characterization, and Luminescent Properties. Cryst.
Growth Des. 2009, 9, 783−791.
(35) Ray, M.; Basu, T. S.; Bandyopadhyay, N. R.; Klie, R. F.; Ghosh,
(
18) Kang, F.; Zhang, H.; Wondraczek, L.; Yang, X.; Zhang, Y.; Lei,
3+
S.; Raja, S. O.; Dasgupta, A. K. Highly lattice-mismatched semi-
conductor-metal hybrid nanostructures: gold nanoparticle encapsu-
lated luminescent silicon quantum dots. Nanoscale 2014, 6, 2201−
D. Y.; Peng, M. Band-Gap Modulation in Single Bi -Doped Yttrium−
Scandium−Niobium Vanadates for Color Tuning over the Whole
Visible Spectrum. Chem. Mater. 2016, 28, 2692−2703.
2
210.
(
19) Van Deun, R.; D’Hooge, M.; Savic, A.; Van Driessche, I.; Van
3+
3+
3+
(36) Song, L.; Wang, Q.; Tang, D.; Liu, X.; Zhen, Z. Crystal structure
and near-infrared luminescence properties of novel binuclear erbium
and erbium-ytterbium cocrystalline complexes. New J. Chem. 2007, 31,
Hecke, K.; Kaczmarek, A. M. Influence of Y , Gd , and Lu co-
doping on the phase and luminescence properties of monoclinic
Eu:LaVO particles. Dalton Trans. 2015, 44, 18418−18426.
4
5
(
06−511.
37) Feng, J.; Zhang, H. Hybrid materials based on lanthanide
organic complexes: a review. Chem. Soc. Rev. 2013, 42, 387−410.
38) Chen, H.; Lang, Y.; Zhang, Y.; Zhao, D.; Qin, G.; Wu, C.;
(
20) Xu, Z.; Feng, B.; Gao, Y.; Zhao, Q.; Sun, D.; Gao, X.; Li, K.;
Ding, F.; Sun, Y. Uniform and well-dispersed GdVO hierarchical
architectures: hydrothermal synthesis, morphology evolution, and
4
(
luminescence properties. CrystEngComm 2012, 14, 5530−5538.
(
21) Han, S.; Deng, R.; Xie, X.; Liu, X. Enhancing Luminescence in
Zheng, K.; Qin, W. Dual mode emission of core-shell rare earth
nanoparticles for fluorescence encoding. J. Mater. Chem. C 2015, 3,
6314−6321.
(39) Toyota, S. Rotational Isomerism Involving Acetylene Carbon.
Chem. Rev. 2010, 110, 5398−5424.
Lanthanide-Doped Upconversion Nanoparticles. Angew. Chem., Int.
Ed. 2014, 53, 11702−11715.
(
22) Wang, F.; Han, Y.; Lim, C. S.; Lu, Y.; Wang, J.; Xu, J.; Chen, H.;
Zhang, C.; Hong, M.; Liu, X. Simultaneous phase and size control of
I
DOI: 10.1021/acs.inorgchem.6b02125
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
(
40) Song, Y.; Shao, B.; Feng, Y.; Lu, W.; Liu, G.; You, H. A novel
3+
strategy to enhance the luminescence performance of NaGdF :Ln
4
nanocrystals. Dalton Trans. 2016, 45, 9468−9476.
(
41) Li, S.; Zhang, X.; Hou, Z.; Cheng, Z.; Ma, P.; Lin, J. Enhanced
3+
emission of ultra-small-sized LaF :RE (RE = Eu, Tb) nanoparticles
3
through 1,2,4,5-benzenetetracarboxylic acid sensitization. Nanoscale
2
(
012, 4, 5619−5626.
42) Chen, J.; Meng, Q.; May, P. S.; Berry, M. T.; Lin, C.
3+
Sensitization of Eu Luminescence in Eu:YPO Nanocrystals. J. Phys.
4
Chem. C 2013, 117, 5953−5962.
(
43) Irfanullah, M.; Sharma, D. K.; Chulliyil, R.; Chowdhury, A.
Europium-doped LaF nanocrystals with organic 9-oxidophenalenone
3
capping ligands that display visible light excitable steady-state blue and
time-delayed red emission. Dalton Trans. 2015, 44, 3082−3091.
J
DOI: 10.1021/acs.inorgchem.6b02125
Inorg. Chem. XXXX, XXX, XXX−XXX