Photofunctional Eu3+/Tb3+ hybrid material with inorganic silica covalently linking polymer chain through their double functionalization

Article abstract of DOI:10.1016/j.ica.2011.06.036

In the context, 2-thiosalicylic acid (TSA) is modified with two crosslinking reagents (3-chloropropyltrimethoxysilane (CTPMS), 3-(triethoxysilyl)-propyl isocyanate (TESPIC)) to achieve two kinds of sulfide bridges (abbreviated as TSA-CSi and TSA-TSi, respectively). And two organic polymers (poly acrylamide (PAM) and poly ethylene glycol (PEG)) are also functionalized with TESPIC to form their polymeric silane derivatives PAMSi and PEGSi. Then series of multi-component Eu³⁺/Tb³⁺ hybrid material have been assembled with inorganic silica covalently linking organic polymer through the sulfide bridges after co-hydrolysis and co-polycondensation with the above inorganic or organic alkoxyl compounds (TSA-CSi(TSi), PAMSi(PEGSi)) and tetraethoxysilane (TEOS). These hybrid material are characterized in details to compare with the binary hybrid material without organic polymer unit, whose results reveal that the photoluminescence properties of the hybrid system are improved with the introduction of the polymer unit.

Full text of DOI:10.1016/j.ica.2011.06.036

Inorganica Chimica Acta 376 (2011) 302–309
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Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Photofunctional Eu3+/Tb3+ hybrid material with inorganic silica covalently
linking polymer chain through their double functionalization
⇑
Bing Yan , Qian Kai, Xiao-Long Wang
Department of Chemistry, Tongji University, Siping Road 1239, Shanghai 200092, China
a r t i c l e i n f o
a b s t r a c t
Article history:
In the context, 2-thiosalicylic acid (TSA) is modified with two crosslinking reagents (3-chloropropyltri-
methoxysilane (CTPMS), 3-(triethoxysilyl)-propyl isocyanate (TESPIC)) to achieve two kinds of sulfide
bridges (abbreviated as TSA-CSi and TSA-TSi, respectively). And two organic polymers (poly acrylamide
(PAM) and poly ethylene glycol (PEG)) are also functionalized with TESPIC to form their polymeric silane
derivatives PAMSi and PEGSi. Then series of multi-component Eu3+/Tb3+ hybrid material have been
assembled with inorganic silica covalently linking organic polymer through the sulfide bridges after
co-hydrolysis and co-polycondensation with the above inorganic or organic alkoxyl compounds (TSA-
CSi(TSi), PAMSi(PEGSi)) and tetraethoxysilane (TEOS). These hybrid material are characterized in details
to compare with the binary hybrid material without organic polymer unit, whose results reveal that the
photoluminescence properties of the hybrid system are improved with the introduction of the polymer
unit.
Received 31 March 2011
Received in revised form 31 May 2011
Accepted 22 June 2011
Available online 30 June 2011
Keywords:
Photofunctional hybrid system
Sulfide linkage
Europium ion
Terbium ion
Photophysical property
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
the simply doping of luminescent Eu3+ or Tb3+ complexes in poly-
mers possess improved processing ability, chemical stability, and
Photofunctional Eu3+ and Tb3+ coordination compounds are
readily to achieve the ideal luminescence behavior such as narrow
emission bands to obtain high color purity, wide spectral and
lifetime range for extensive application, etc. [1–3]. In order to
improve the thermal or optical stabilities of Eu3+ and Tb3+ complex
systems, the common popular method is to incorporate them into
inorganic silica host gel or organic polymer matrix to construct
organic/inorganic hybrid material [4–10]. To presence, the study
are mainly focused on the chemically bonding assembly of compo-
nent unit to obtain the hybrid systems which can overcome the
inhomogeneity and leaching or clustering of the photoactive center
by conventional doping methods for these kinds of hybrid material
belong to the complicated molecular-scale network [4–10]. The
critical step to construct the chemically bonded hybrid material is
to design functional molecular bridge as covalent linkage both
coordinating to Eu3+ or Tb3+ and bonding with host. There are many
kinds of modifying routes of organic ligands to the building block to
assemble hybrid material, which are based on the functional group
of them [11–24]. Among most work are focused on the organically
modified silica hybrid material for that silane precursors are abun-
dant to be easily functionalized.
mechanical strength, due to the nature of polymer [28]. It has been
testified that if a rare-earth ion is chemically bonded to the chains
of polymer, the content of rare-earth ion, the type of chemical inter-
action between the rare-earth ion and polymer chain, and the distri-
bution of rare-earth ion along the polymer chains, etc. will strongly
influence the luminescent properties of the final materials [29–32].
With the same content of rare-earth complex, a dispersion of
smaller-sized particlesof thecomplex leads to a higher transparency
of the hybrid material and a larger interfacial region between the
dispersed complex particles and the polymer matrix, both of which
will improve the efficiency of excitation [33–36]. So the tendency for
rare earth hybrid materials is to assemble inorganic polymeric Si–O
network and organic polymeric chain into one hybrid system to
integrate their functions together effectively [37–40]. While these
hybrid materials are mainly based on the direct coordination be-
tween rare earth ions and the organic polymer chain unit [41,29,42].
Herein, we put forward another path to synthesize the rare
earth hybrid materials, whose organic chain unit is covalently
bonded with inorganic silica through Si–O network while not coor-
dinating to rare earth ions. 2-Thiosalicylic acid (TSA) can be func-
tionalized with crosslinking reagents to achieve two kinds of
sulfide bridges [17]. At the same time, organic polymers (poly
acrylamide (PAM) and poly ethylene glycol (PEG)) can also be mod-
ified to form alkoxyl groups along the polymer chain. So the hybrid
material of organically bonded silica/polymer can be prepared
through the cohydrolysis and copolycondensation reaction, and
Eu3+ or Tb3+ ions can be introduced within the hybrid system
In addition, luminescent Eu3+ or Tb3+ polymeric hybrid systems
also have been investigated for their potential applications in
luminescence and laser fields [25–27]. The hybrid material with
⇑
Corresponding author. Tel.: +86 21 65984663; fax: +86 21 65982287.
E-mail address: byan@tongji.edu.cn (B. Yan).
0020-1693/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2011.06.036

B. Yan et al. / Inorganica Chimica Acta 376 (2011) 302–309
303
through the coordination bonding to sulfide linkage. The physical
characterization and especially the photophysical property have
been compared to study in details.
0.78(2H, t), 1.88(2H, m), 3.16(2H, t), 3.58(9H, s), 7.15(1H, q),
7.32(1H, d), 7.78(1H, q), 8.08(1H, d), 11.2(1H, s).
2.2.2. TSA-TSi
TSA (0.231 g, 1.5 mmol) is first dissolved in 10 mL of pyridine
and then TESPIC (0.371 g, 1.5 mmol) is added by drops. The whole
solution is maintained at 80 °C for 3 h. The solvent is removed by
a rotary vacuum evaporator, and then the yellow oil-like products
are obtained. Yield: 81%. Anal. Calc. for C17H27O6NSSi: C, 50.85; H,
6.78; N, 3.49. Found: C, 50.61; H, 6.49; N, 3.30%. 1H NMR (CDC13,
400 MHz): d 0.64(2H, t), 1.25(9H, t), 1.56(2H, m), 3.23(2H, t),
3.78(6H, q), 7.33(1H, q), 7.43(1H, t), 7.72(1H, d), 7.90(1H, q),
8.76(1H, d), 11.1(1H, s).
2. Experimental
2.1. Materials
Europium and terbium nitrates are obtained by dissolving corre-
sponding oxides (Eu2O3, Tb4O7) in concentrated nitric acid. The si-
lane crosslinking reagents, 3-chloropropyltrimethoxysilane
(CPTMS) and 3-(triethoxysilyl)-propyl isocyanate (TESPIC) are pro-
vided by Alfa company and Lancaster Synthesis Ltd., respectively.
Tetraethoxysilane (TEOS) and 2-thiosalicylic acid (TSA) are supplied
by Aldrich. The normal solvents are purchased from China National
Medicine Group (A.P.). Other starting reagents are used as received.
2.3. Synthesis of the polymer functionalized silane (PAM-Si, PEG-Si)
2.3.1. PAM-Si
2.2. Synthesis of molecular bridge as covalent linkages [17]
Acrylamide (3 mmol, 0.213 g) is first dissolved in absolute alco-
hol, and then CP (3 mmol, 0.597 g) is added by drops. The whole
mixture is refluxing under nitrogen for 12 h. After removing the
solvent, a pale yellow solid is obtained (AM-Si). The resulting prod-
ucts are obtained the yield 92%. Anal. Calc. for C9H19O4NSi: C,
46.33; H, 8.21; N, 6.00. Found: C, 46.17; H, 8.04; N, 5.83%. 1H
NMR (DMSO-d6, 400 MHz): d 6.7(1H, t), 6.30(1H, t), 6.24(1H, t),
5.70(1H, t), 3.62(9H, t), 2.24(2H, m), 1.23(2H, m), 0.25(2H, t).
AM-Si is subsequently dissolved in 10 mL DMF, and the initiator
benzoyl peroxide (0.02 g) is added to the solution to proceed the
polymerization reaction under nitrogen. The temperature is
2.2.1. TSA-CSi
One millimole of TSA (0.231 g, 1.5 mmol) is first dissolved in
10 mL of N,N-dimethyl formamide (DMF). CPTMS (0.299 g,
1.5 mmol) is then added to the solution by drops while stirring.
K2CO3 (0.08 g) is added as catalyst. The whole mixture is refluxing
at 80 °C for 3 h. After cooling, the solvent is removed by using a
rotary vacuum evaporator, and then the yellow oil-like products
are obtained. Yield: 78%. Anal. Calc. for C13H20O5SSi: C, 49.34; H,
6.37. Found: C, 49.03; H, 6.10%. 1H NMR (CDC13, 400 MHz): d
Fig. 1. The selected scheme for the synthesis and predicted composition of ternary europium and terbium polymeric hybrid material (A) RE-TSA-CSi-PAM, (B) RE-TSA-TSi-
PAM, (C) RE-TSA-CSi-PEG, and (D) RE-TSA-TSi-PEG.

304
B. Yan et al. / Inorganica Chimica Acta 376 (2011) 302–309
maintained at 60 °C for 3 h. The solvent DMF is removed using a ro-
tary vacuum evaporator, and the crude product obtained is washed
with 20 mL of hexane. At last, the pure product PAM-Si is obtained
(see Fig. 1).
as an internal reference. The UV–Vis diffuse reflection spectra of
the powder samples are recorded by a BWS003 spectrophotome-
ter. X-ray powder diffraction patterns are recorded using a Rigaku
Dmax-rB diffractometer system equipped with a Cu anode in a 2h
range from 10° to 70°. The luminescence spectra are obtained on a
RF-5301 spectrofluorimeter equipped with a stable spec-xenon
lamp (450 W) as the light source. Luminescent lifetimes are re-
corded on an Edinburgh FLS 920 phosphorimeter, using a 450 W
2.3.2. PEG-Si
PEG400 (3 mmol) and TESPIC (6 mmol, 1.482 g) are added to
20 mL of DMF. After refluxing at 80 °C for 10 h, the whole solution
is concentratedto remove solventusing a rotary vacuumevaporator.
The residue is washed three times with hexane, and then the pure
xenon lamp as the excitation source (pulse width, 3 ls). The outer
luminescent quantum efficiency is determined using an integrat-
ing sphere (150 mm diameter, BaSO4 coating) from Edinburgh
FLS920 phosphorimeter. The quantum yield can be defined as the
integrated intensity of the luminescence signal divided by the inte-
grated intensity of the absorption signal. The absorption intensity
is calculated by subtracting the integrated intensity of the light
source with the sample in the integrating sphere from the inte-
grated intensity of the light source with a blank sample in the inte-
grating sphere. All above measurements are completed under
room temperature. The microstructures are checked by scanning
electronic microscopy (SEM, Philips XL-30).
yellow liquid is obtained. 1H NMR (DMSO-d6, 400 MHz):
d
0.64(4H, t), 1.28(18H, t), 1.66(4H, t), 3.18(4H, m), 3.56(12H, q),
3.78(20H, t), 3.86(4H, t), 3.93(4H, t), 4.08(4H, t), 4.39(4H, t),
7.32(2H, t) (see Fig. 1).
2.4. Synthesis of the binary (ternary) Eu3+ and Tb3+ polymeric hybrid
materials
2.4.1. Binary hybrid material
The synthesis of binary hybrid material is for comparison with
the procedure as Ref. [17]. TSA-CSi/TSA-TSi is first dissolved in
DMF, then
a
stoichiometric amount of Eu(NO3)3ꢀ6H2O/
Tb(NO3)3ꢀ6H2O is added into the solution by drops. After stirring
for 5 h, a stoichiometric amount of TEOS and one drop of diluted
hydrochloric acid are added to the whole mixture to promote
hydrolysis. The molar ratio of Eu(NO3)3ꢀ6H2O/Tb(NO3)3ꢀ6H2O:TSA-
CSi/TSA-TSi:TEOS:H2O is 1:3:6:24. After the treatment of hydroly-
sis, an appropriate amount of hexamethylenetetramine is added
to adjust the pH 6–7. The mixture is agitated magnetically to
achieve a single phase, and then it is aged at 65 °C until the sample
is solidified.
3. Results and discussion
The Fourier transform infrared spectra of TSA and the two mod-
ified linkages are presented in Fig. 2(A). It can be clearly observed
that there exists absorption band centered at around 2950 and
2875 cmꢁ1 in the three precursors, corresponding to the asymmet-
ric stretching vibration and symmetric stretching vibration for the
methylene (–CH2–) of the coupling reagents. The vanishing of the
m
(S–H) at around 2520 cmꢁ1 suggests the modification of the cou-
pling reagent. The broad band at about 3440 cmꢁ1 and the low
absorption peak at 920 cmꢁ1 in the IR spectra of the three precur-
sors are ascribed to the stretching vibration and the out-of-plain
bending vibration of OH group. The disappearance of the stretch
2.4.2. Ternary hybrid material
The method is similar to that of the binary hybrid materials.
TSA-CSi/TSA-TSi is first dissolved in DMF, then a stoichiometric
amount of Eu(NO3)3ꢀ6H2O/Tb(NO3)3ꢀ6H2O is added into the solution
by drops. After stirring for 5 h, a stoichiometric amount of TEOS,
PEG-Si/PAM-Si and one drop of diluted hydrochloric acid are added
to the mixture. The molar ratio of Eu(NO3)3ꢀ6H2O/Tb(NO3)3ꢀ6H2O:
PEG-Si/PAM-Si:TSA-CSi/TSA-TSi:TEOS:H2O is 1:1:3:6:24. Then an
appropriate amount of hexamethylenetetramine is added to adjust
the pH 6–7. The mixture is agitated magnetically to achieve a single
phase, and then it is aged at 65 °C until the sample is solidified.
The final hybrid material samples are dissolved in nitric acid,
then titrated with EDTA solution, using a buffer (pH 5.8) and xyle-
vibration of the m
(C–Cl) at 800 cmꢁ1 for TSA-CSi and (N@C@O) at
2250–2275 cmꢁ1 for TSA-TSi indicates the coupling reagent is
grafted onto the TSA. Besides, the existence of stretching vibration
of Si–C, located at 1200 cmꢁ1 and the stretching vibration of Si–O
at 1100 and 1050 cmꢁ1 suggest the formation of the siloxane
bonds. Fig. 2(B) shows the UV absorption spectra of TSA and link-
ages (TSA-CSi and TSA-TSi). The absorption bands corresponding to
the
p ?
p⁄ electronic transition of aromatic carboxylic acids all lo-
cate at 253 and 265 nm. But the absorption peaks corresponded to
the n ? p⁄ electronic transition of sulfide group locate at different
wavelength. There is a red shift of the n ? p⁄ electronic transitions
(from 293 to 305 nm) by comparing the precursors to TSA. As well
there is a change of molar absorbance at around 300 nm. All these
facts indicate the modification of the sulfide linkage influence the
energy difference levels among electron transitions.
Fig. 3(A) and (B) shows the FT-IR spectra of the europium and
terbium hybrid materials through the TSA-CSi or TSA-TSi linkages,
both of which present the similar feature for the identical modified
TSA Si–O network and the introduction of polymer chain has no
apparent influence on the IR spectra. Because the large content of
Si–O network and polymer chain, the organic groups of the TSA-
CSi or TSA-TSi framework cannot be clearly to be distinguished
in their IR spectra. The absorption peaks at around 2925 cmꢁ1
can be ascribed to the –CH2 vibration and the broad absorption
bands at the range of 3000–3750 cmꢁ1 are corresponded to the
X–H groups (X = O, N, S). The stretching vibration of C@O group
at 1730 cmꢁ1 disappears after coordination with Eu3+ or Tb3+ ions
and new absorption band at 1680 and 1560 cmꢁ1 appears, which is
attributed to the symmetric vibration and asymmetric vibration of
the carbonyl groups belonging to the amide groups, respectively.
The absorption peak at around 1370 cmꢁ1 is attributed to the
nol-orange as indicator. The contents of rare earth ions (Eu3+, Tb3+
)
in the hybrid material are determined by complexometric titrations.
For Eu3+, 7.40% (Eu-TSA-CSi), 7.25% (Eu-TSA-TSi), 7.02%(Eu-TSA-CSi-
PAM); 6.82% (Eu-TSA-TSi-PAM), 6.92% (Eu-TSA-CSi-PEG), 6.76%
(Eu-TSA-TSi-PEG). For Tb3+, 7.27% (Tb-TSA-CSi), 7.30% (Tb-TSA-
TSi), 6.79% (Tb-TSA-CSi-PAM); 6.90% (Tb-TSA-TSi-PAM), 6.88%
TSA-CSi-PEG), 7.01% (Tb-TSA-TSi-PEG). In fact, the sol–gel reaction
cannot be guaranteed to be completely [43,44] and so it is difficult
to determine the exact composition of the TSA-CSi(TSi)-PAM(PEG)
networks within the complicated hybrid system not like small
molecule complex.
2.5. Physical measurements
All measurements are performed at room temperature. Infrared
spectra are recorded on a Nexus 912 AO439 FT-IR spectrophotom-
eter. We mixed the compound with the dried potassium bromide
(KBr) and then pressed into pellets. The spectra are collected over
the range 4000–400 cmꢁ1 by averaging 32 scans at a maximum
resolution of 8 cmꢁ1 1H NMR spectra are recorded in CDCl3 on a
.
Bruker AVANCE-500 spectrometer with tetramethylsilane (TMS)

B. Yan et al. / Inorganica Chimica Acta 376 (2011) 302–309
305
Fig. 2. The FT-IR spectra (A) and ultraviolet absorption spectra (B) of the TSA, TSA-CSi, TSA-TSi.
Fig. 3. The FT-IR spectra of the binary and ternary europium and terbium polymeric hybrid material with TSA-CSi bridge (A) and TSA-TSi bridge (B).
nitrate group in the hybrid system. In addition, the weak absorp-
tion at about 440 cmꢁ1 is ascribed to the RE–O vibration. The broad
morphology on the surface. The similar features are shown in the
SEM images for the binary and ternary europium hybrid material
with TSA-TSi linkage series. These results verify that the organic
polymer chain plays an important role in the formation of the ulti-
mate complicated hybrid system (Fig. 4(B), (C), (E), and (F)). Com-
paring the SEM images of the two binary europium hybrid material
with two different linkages (Fig. 4(A) and (D)), it can be found they
are very different texture microstructure. And the ternary hybrid
material with the polymer chain units show the similar micro-
structure (Fig. 4(B), (C), (E), and (F)), suggesting the similar effect
from the same polymer chain PAM or PEG. These interesting mor-
phologies can be explained from the formation process of the bin-
ary and ternary hybrid system. It is considered that the
coordination reaction and hydrolysis–condensation process are
the critical factor on ultimate morphology of the hybrid material.
For binary hybrid material, europium ions are chelated by small
bridge molecule TSA-CSi(TSi) in the initial stage to generate the
luminescent center. When TEOS is added, the cohydrolysis and
copolycondensation reactions occur between the terminal silanol
groups of TSA-CSi(TSi) and OH groups of hydrolyzed TEOS. At the
beginning of the reaction, the individual hydrolysis of TSA-CSi(TSi)
and TEOS are predominant. Then the condensation reaction is per-
formed between hydroxyl groups of both TSA-CSi(TSi) and TEOS.
This cohydrolysis and copolycondensation process are carried out
by encircling the luminescent center without directivity because
of the structure of the luminescent center is non-rigid and easily
changed in the surrounding micro-environment, which lead to
the forming disordered and irregular micromorphology. Furtherly,
the coordination reaction between Eu3+ and TSA-CSi(TSi) unit
group also have influence on the morphology of the final hybrid
material, which is related to the ligand group of TSA-CSi and
TSA-TSi. TSA-TSi is provided with one new C@O of amide group
absorption bands at 1200–1100 cmꢁ1
(mSi–O–Si(R)) indicate the for-
mation of siloxane bonds. The containing of the organic groups
by the silicate inorganic host which occurred in the hydrolysis
and condensation process caused the decrease of other peaks’
intensities. The infrared spectroscopy can also prove the coordina-
tion of RE3+ ions by the ligands. The
m
(COOꢁ) vibrations is shifted to
m
= 40–70 cmꢁ1) after coordination to the
lower frequencies (
D
metallic ion with the oxygen atom of the carbonyl group.
The X-ray diffraction (from 10° to 70°) spectra of the hybrid
materials show they are amorphous. All the materials exhibit the
similar XRD patterns with a broad peak centered at around 23°
which is the characteristic diffraction of amorphous siliceous back-
bone material [45,46]. Moreover, there is no new diffraction peaks
for the ternary hybrid material with the introduction of polymer
chain, which reveals that the polymer chain in the hybrid system
has not changed the disordered silicon skeleton. Fig. 4 shows the
micrographs of the selected europium hybrid materials: A, B, C
for the hybrid material with TSA-CSi linkage and D, E, F for those
with TSA-TSi linkage. It can be seen from the images of all hybrid
material that homogeneous, molecular based system is formed
without any phase separation phenomenon, which demonstrate
that covalent bonds are constructed between the organic and inor-
ganic phases with functional bridge molecule as covalent linkage.
Comparing the SEM images of the binary and the ternary europium
hybrid materials through TSA-CSi linkage, it can be found that
there exist apparent differences of their micromorphology. For
the binary hybrid material Eu-TSA-CSi, it forms the uniform tissue
network microstructure. While for the ternary hybrid material
Eu-TSA-CSi-PAM(PEG), the stripe microstructure are shown and
especially Eu-TSA-CSi-PEG shows the dendrite with ordered

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B. Yan et al. / Inorganica Chimica Acta 376 (2011) 302–309
Fig. 4. The selected SEM images of binary and ternary europium polymeric hybrid material (A) Eu-TSA-CSi, (B) Eu-TSA-CSi-PAM, (C) Eu-TSA-CSi-PEG, (D) Eu-TSA-TSi, (E) Eu-
TSA-TSi-PAM, and (F) Eu-TSA-TSi-PEG.
besides the COO group of TSA molecules, so it is easily to form the
bidentate chelation to Eu3+ and oxygen atoms of hydroxyl group
are left to produce the bridging effect for the formation of the chain
or strip structure, resulting in the long stripe morphology for Eu-
TSA-TSi hybrid material (Fig. 4(D)). While TSA-CSi linkage has
not the C@O group and only the COO group of TSA unit take part
in the coordination to Eu3+ and easily to form the chelated struc-
ture for the formation of tissue morphology. For ternary hybrid
material, the polymer chain (PAM or PEG) of PAMSi or PEGSi are
introduced into the sol–gel process for the modification of siliane
and so the cohydrolysis and copolycondensation processes are
engaged among three components (TEOS, TSA-CSi(TSi) and PAM-
Si(PEGSi)) and become more complicated than the binary hybrid
material. Therefore, it is worthy pointing out that the polymer
chain of PAM or PEG has the macromolecular template effect to in-
duce the whole hybrid system to be more stripe microstructure.
Moreover, the apparent distinction of the morphology of ternary
hybrid material depends on the different polymer chain unit of
PAM or PEG, which may be due to the composition of them. PEGSi
provides double ester group and two amide groups while the PAM-
Si only possesses the amide groups, so the template effect of PEG
may be more complicated than PAM, which results in the long den-
dritic or stripe-shaped morphology of Eu-TSA-CSi(TSi)-PEG hybrid
material. Therefore, it can be drawn a conclusion that the more or-
dered and regular microstructure is achieved with the introduction
of the polymer.
Fig. 5 exhibits the UV–Vis diffuse reflection absorption spectros-
copy of the selected hybrid materials: the hybrid material of TSA-
CSi linkage for A and the hybrid material of TSA-TSi linkage for B,
respectively. There is a large broad absorption band in each hybrid
which is attributed to the
p–
p⁄ electronic transition of the aro-
matic ring in the hybrid system. Among the ternary europium
and terbium hybrid material with PAM chain present the more half
band width and longer absorption side than other hybrid systems,
revealing that the introduction of PAM polymer unit is favorable
for the energy absorption of the whole hybrid systems. This can
be verified from the luminescent spectra of europium and terbium
hybrid material in Figs. 6 and 7.
Figs. 6 and 7 show the excitation and emission spectra of euro-
pium and terbium hybrid materials. For the excitation spectra of
europium hybrid material (Fig. 6), two kinds of excitation bands
can be observed. Firstly, a series of sharp lines appear at the range
of 300–450 nm, which can be ascribed to f–f transitions of Eu3+ ion
(326 nm, 7F0 ? 5H6; 375 nm, 7F0 ? 5D4; 383 nm, 7F0 ? 5G2;
394 nm, 7F0 ? 5L6, strongest; 417 nm, 7F0 ? 5D3) [47]. Secondly,
broad bands ranging from 280 to 350 nm arise from the
p–
p⁄

B. Yan et al. / Inorganica Chimica Acta 376 (2011) 302–309
307
Fig. 5. The UV–Vis diffuse reflectance spectra of the binary and ternary europium and terbium polymeric hybrid material with TSA-CSi bridge (A) and TSA-TSi bridge (B).
Fig. 6. The excitation and emission spectra of binary and ternary europium hybrid material with TSA-CSi bridge (A) and TSA-TSi bridge (B).
Fig. 7. The excitation and emission spectra of binary and ternary terbium hybrid material with TSA-CSi bridge (A) and TSA-TSi bridge (B).
transition of the TSA organically modified Si–O network, whose
wide bands are overlapped with some f–f transition peaks. As a re-
sult, the sharp emission peaks assigned to the 5D0 ? 7FJ (J = 0, 1, 2,
3, 4) transitions can be seen at about 579, 591, 615, 653 and
697 nm, respectively for europium ions, indicating that conjugated
systems have formed between the TSA group of organically
modified Si–O network and europium ions and energy transfer
have occurred in these hybrid materials. While the emission lines
assigned to 5D0 ? 7F2 transitions are the most intense for the euro-
pium hybrid materials, indicating that the europium ion occupies a
site without inversion symmetry [48]. Comparing the emission
intensities of the europium hybrid materials of TSA-CSi (A) and
TSA-TSi (B) linkages, it is observed that the relative emission inten-
sities of the ternary hybrid material with PAM/PEG polymer chain
are obviously stronger than those of the binary hybrid material
without polymer chain. This indicates that the introduction of
PAM or PEG is benefit for the photoluminescence of the hybrid
material, which may be due to the fact that the polymer chain unit
can affect the microstructure of the whole hybrid systems to im-
prove the luminescence.
Fig. 7 shows the excitation spectra of terbium hybrid material,
which consist of the broad band appears at the ultraviolet region
of 300–350 nm, corresponding to the absorption of TSA group of
the organically bonded silica. The f–f transitions of Tb3+ 4f8 config-
uration in the longer ultraviolet region are too weak to be checked.
The corresponding emission spectra are measured of the terbium
hybrid materials present the sharp emission peaks assigned to
the transitions 5D4 ? 7FJ (J = 6, 5, 4, 3) can be seen at 490, 545,
582 and 620 nm, respectively for terbium ions, indicating that con-
jugated systems have formed between the TSA group of organically

308
B. Yan et al. / Inorganica Chimica Acta 376 (2011) 302–309
Table 1
large, the quantum efficiency must be high. As can be seen clearly
from Table 1, the quantum efficiencies of the europium hybrid
materials are determined in the order: Eu-TSA-CSi-PAM ꢂ Eu-
TSA-CSi-PEG > Eu-TSA-CSi for the hybrid material with TSA-CSi
linkage and Eu-TSA-TSi-PAM > Eu-TSA-TSi-PAM > Eu-TSA-TSi for
the hybrid material with TSA-TSi one. Besides, the calculated value
of luminescent quantum efficiencies for the europium hybrids are
lower than the experimental measured value. This may be due to
the fact there exist some errors in the measurement and calcula-
tion of spectral and lifetimes. For europium hybrid materials, the
introduction of polymer chain are favorable for the luminescence
of the whole system, while for terbium hybrid materials, the
results become complicated. The introduction of PEG chain still
improve the luminescent lifetimes and quantum efficiencies while
it is contrary to the introduction of PAM chain. The results reveal
that the introduction of the polymer chain is only the one factor
influencing on the luminescence properties of the overall hybrid
system. In addition, we compare the photoluminescent properties
of them to the different hybrid materials with single sulfide
without polymer unit and the hybrid materials without interaction
between organically modified silica and polymer chain in our
previous work [17,54]. It is found that these hybrid materials can
display the matchable luminescent quantum efficiency with the
other kinds of hybrid materials reported in [17,54], suggesting that
the assembly path in the present work is a candidate technology to
prepare the hybrid materials.
The photoluminescent lifetimes and quantum efficiencies data of rare earth hybrid
materials.
Hybrids
I02/I01
Arad (sꢁ1
)
s
(
l
s)a,b
g
(%)c
Eu-TSA-CSi
3.0
3.3
3.3
218
232
235
365
456
454
875
428
617
376
466
385
745
492
804
2.3 (7.9)
3.4 (10.6)
3.7 (10.7)
7.1
3.5
5.3
2.4 (8.0)
3.5 (11.1)
2.7 (9.5)
6.2
3.6
6.5
Eu-TSA-CSi-PAM
Eu-TSA-CSi-PEG
Tb-TSA-CSi
Tb-TSA-CSi-PAM
Tb-TSA-CSi-PEG
Eu-TSA-TSi
Eu-TSA-TSi-PAM
Eu-TSA-TSi-PEG
Tb-TSA-TSi
Tb-TSA-TSi-PAM
Tb-TSA-TSi-PEG
2.9
3.4
3.6
214
239
246
a
b
c
5D0
5D4
?
?
7F2 transition of Eu3+
7F5 transition of Tb3+
.
.
Calculated value in bracket from spectra and lifetime.
modified Si–O network and europium or terbium ions and energy
transfer have occurred in these hybrid materials. For the terbium
hybrid materials, the green emission assigned to the 5D4 ? 7F5
transitions is the most striking.
The decay curves of all the europium and terbium hybrid mate-
rials are measured at room temperature, all of which can be de-
scribed as
a
single exponential (ln[S(t)/S0] = ꢁk1t = ꢁt/
s). The
resulting luminescent lifetimes of europium hybrid material are
detailed in Table 1. Furthermore, we selectively determined the
emission quantum efficiency of 5D0 Eu3+ excited state for europium
containing hybrid material on the basis of emission spectra and
lifetimes of 5D0 emitting level. Assuming that only nonradiative
and radiative processes are essentially involved in the depopula-
4. Conclusions
In summary, series ternary Eu3+/Tb3+ hybrid materials have
been assembled with sulfide functionalized silica network (TSA-
CSi(TSi)) covalently linking polymer chain (PAM(PEG)), whose
physical characterization, microstructure and especially photo-
physical property are studied comparing with binary hybrid mate-
rial without polymer chain. The results reveal that the ternary
hybrid materials present more regular morphology, stronger lumi-
nescence intensity, longer lifetimes and higher quantum efficiency
than the binary hybrid material, indicating that the introduction of
the polymer can induce the occurrence of the self-assemble pro-
cess of the microstructure and sensitize the luminescence of the
hybrid materials.
tion of the 5D0 state,
g can be defined as follows [49–53]:
g
¼ Ar=ðAr þ AnrÞ
ð1Þ
Here, Ar and Anr represent radiative and nonradiative transition
rates, respectively. Ar can be obtained by summing over the radia-
tive rates A0J for each 5D0 ? 7FJ (J = 0–4) transitions of Eu3+
.
X
Ar ¼
A0J ¼ A00 þ A01 þ A02 þ A03 þ A04
ð2Þ
The branching ratio for the 5D0 ? 7F5,6 transitions can be neglected
as they are not detected experimentally, whose influence can be
ignored in the depopulation of the 5D0 excited state. Since
5D0 ? 7F1 is an isolated magnetic dipole transition, it is practically
independent of the chemical environments around the Eu3+ ion as
an internal reference for the whole spectra, the experimental coef-
ficients of spontaneous emission, A0J can be calculated according to
the equation [49–53].
Acknowledgments
This work is supported by the National Natural Science Founda-
tion of China (20971100) and Program for New Century Excellent
Talents in University (NCET-08-0398) and the Developing Science
Funds of Tongji University.
A0J ¼ A01ðI0J=I01Þðm01
=m0J
Þ
ð3Þ
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50 sꢁ1 approximately (A01 = n3A01(vac)) [49–53]. I01 and I0J are the
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