Sensitization of LnIII (Ln = Eu, Tb, Tm) Ion Luminescence by Functionalized Polycarbonate-Based Materials and White Light Generation

Article abstract of DOI:10.1002/ejic.201700655

We prepared pyridine-2,6-bis(ethyl)ester [BEP] and pyridine-2,6-bis(diethylamide) [BDP] polymers with polycarbonate backbones by ring-opening polymerization of the pyridine-bis(ethyl)ester and pyridine-bis(diethylamide) units appended to a cyclic carbonat

Full text of DOI:10.1002/ejic.201700655

DOI: 10.1002/ejic.201700655
Full Paper
Sensitization of Ln Emission | Very Important Paper |
Sensitization of LnIII (Ln = Eu, Tb, Tm) Ion Luminescence by
Functionalized Polycarbonate-Based Materials and White Light
Generation
Rodney A. Tigaa,[a] Xuekelaiti Aerken,[b] Alan Fuchs,[b] and Ana de Bettencourt-Dias*[a]
Abstract: We prepared pyridine-2,6-bis(ethyl)ester [BEP] and polymer was shifted from –13 °C to –9 and –10 °C after coordi-
pyridine-2,6-bis(diethylamide) [BDP] polymers with polycarbon- nation of EuIII and TbIII ions, respectively. Both polymers sensi-
ate backbones by ring-opening polymerization of the pyridine- tized LnIII-centered emission; the BEP polymer was the most
bis(ethyl)ester and pyridine-bis(diethylamide) units appended efficient at sensitizing LnIII-centered luminescence with an emis-
to a cyclic carbonate via a glycol chain. The polymers were sion efficiency of 30 and 31 % for the EuIII and TbIII systems,
characterized by FTIR, NMR, UV/Vis absorption and fluorescence respectively, compared to the 2 % determined for both the EuIII
spectroscopy, as well as SEC, powder XRD, DSC, and TGA. The and TbIII BDP systems. Blue emission was observed when TmIII
measured glass transition temperature (Tg) of the BEP polymer was used, and a system with the composition BEP1Eu1.8Tb28 led
was shifted from –32 °C to –7 and –8 °C after coordination of to a material with CIE coordinates (0.31, 0.33), typical of white
the EuIII and TbIII ions, respectively. Similarly, the Tg of the BDP light.
Introduction
this process, often referred to as the antenna effect, the ligand
absorbs energy, generating a singlet (1S) excited state. Aided
Current displays based on organic light-emitting diodes use or-
ganic compounds,[1] metal complexes,[2] polymeric materials[1]
and semiconductor materials[3] as the emissive layers. However,
these emitting materials have reduced color purity due to vibra-
tional broadening of their emission spectra, low emission effi-
ciencies, difficulty in controlling the phase purity and size of
the semiconducting materials, and a lack of long-term stability
caused by photo-bleaching. Efforts to solve these practical chal-
lenges have led to the incorporation of transition metals to
the main or side chains of the polymers to construct electro-
phosphorescent polymers. However, their emission bands are
still broadened (FWHM = 100 nm), therefore also showing poor
color purity.[4]
Lanthanide, LnIII, ions are emissive with high color purity due
to narrow emission bands (FWHM = 5–10 nm), a result of the
core nature of the 4f orbitals, which are shielded from the li-
gand environment by the filled 5s and 5p orbitals.[5–7] The long
luminescence lifetimes (μs to ms) of the LnIII ions are a result of
the parity forbidden nature of the f–f transitions.[8] The forbid-
den nature of these transitions results in inefficient direct exci-
tation of the metal ion-centered emission.[6] Thus organic li-
gands are often used as optical antennae or sensitizers to trans-
fer energy to the emissive excited states of the LnIII ion.[6,8] In
1
by the heavy atom effect, the S state undergoes intersystem
crossing to populate an excited triplet (3T) state, which then
transfers energy to the LnIII ion; the latter subsequently lumi-
nesces.[5]
Due to their unique optical properties, LnIII ions can be incor-
porated into polymers that possess mechanical properties
desirable for the design of hybrid luminescent materials for
imaging applications.[6,7,9] One such polymer is polymethyl-
methacrylate (PMMA), as reported by Bonzanini[10,11] and
Wang[12] and co-workers. However, brittleness and high water
absorption are practical disadvantages of using PMMA as a ma-
trix for doping LnIII ions.[10] These challenges can be addressed
by using polycarbonate (PC) as an alternative matrix. PCs are
biodegradable, transparent, have low water absorption and
possess high glass transition temperatures (Tg = 140–155 °C)
that make PCs useful in the preparation of versatile materi-
als.[11,13,14] PC-based materials are studied due to their promis-
ing applications ranging from inkjet printing,[15] antimicrobial
agents,[16–18] gas separation membranes,[19] antifouling
agents,[18,20] in drug and gene delivery[21,22] and electro-op-
tics[23] to their use in display applications such as polymer light-
emitting diodes.[24] Recently, Xu, Li, Cai, and co-workers[17]
synthesized amine-functionalized amphiphilic PCs that were
shown to selectively disrupt the bacterial membranes of gram-
positive bacteria. Yang and co-workers[21] prepared a biode-
[a] Department of Chemistry, University of Nevada,
Reno, NV 89557-216, USA
E-mail: abd@unr.edu
[b] Department of Chemical and Materials Engineering, University of Nevada,
Reno, NV 89557-388, USA
gradable vitamin
D-functionalized PC/polyethylene glycol-
based supramolecular hydrogel capable of co-delivering antivi-
ral and antifungal agents. PC-based materials offer a low-cost
and large-scale fabrication of display devices due to their high
solution processability.[4,25] In addition, functionalized PCs can
Supporting information and ORCID(s) from the author(s) for this article are
available on the WWW under https://doi.org/10.1002/ejic.201700655.
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be easily synthesized via ring opening polymerization (ROP) of tography (SEC), powder X-ray diffraction (XRD), thermogravi-
cyclic carbonate derivatives using organometallic or organic metric analysis (TGA) and differential scanning calorimetry
catalysts.[26] Organic catalysts such as thiourea/amine deriva- (DSC).
tives, are highly selective and lead to polymers of narrow poly-
dispersity indices (PDIs).[26] Most often, studies on LnIII lumines-
cent PC materials involve the doping of the PC materials with
Results and Discussion
EuIII ions.[10,11,27] Rubira and co-workers[11] showed that EuIII sen-
sitization can be achieved by doping a blend of PC/PMMA with
a EuIII acetylacetonate complex. However, this fast route to lumi-
nescent materials often leads to inhomogeneous distribution
of the LnIII ions within the matrix.[28] Alternatively, Lu and co-
workers[14] prepared multifunctional PC films with PrIII ions co-
ordinated through the carbonyl oxygen atoms; these materials
showed sensitized PrIII-centered emission. Despite the intrinsic
properties of these materials, which make them interesting for
a variety of applications, reports of luminescent PC materials
with covalently attached LnIII chelating antennae remain scarce.
The new monomers 4 and 5 were synthesized using common
synthetic procedures[30] by reacting the cyclic carbonate mono-
mer 1 with a newly synthesized glycol-appended chelator 2 or
3 as shown in Scheme 1 (details in the Supporting Information).
1
They were characterized by H and 13C NMR spectroscopy (Fig-
ures S1–S8, Supporting Information). The polymers were pre-
pared by adopting a one-pot strategy used by Waymouth and
co-workers[29] to copolymerize cyclic carbonates containing a
pendant dithiolane and PEG; a DBU/TU co-catalyst system was
used to initiate ROP of trimethylene carbonate/dithiolane from
Here, we describe the synthesis of new luminescent poly- telechelic PEG diols. The formation of the polymers was con-
1
mers with PC backbones for the coordination of LnIII ions and firmed by H NMR spectroscopy (Figures S9–S10), SEC (Figures
sensitization of their luminescence. We isolated and character- S11a–b), FTIR spectroscopy (Figure 1) and mass spectrometry
ized a pyridine-bis(ethyl)ester (BEP) and a pyridine-bis(diethyl- (Figures S12–S13). The 1H NMR spectra showed proton resonan-
amide) (BDP) with appended cyclic carbonates via glycol chain ces corresponding to the copolymerized PEG and carbonate-
monomers to enhance their solubility. The monomers were functionalized BEP and BDP chelators (Figures S9–S10). The
then co-polymerized with 2 kDa polyethylene glycol (PEG) to mass spectra of the polymers showed broad peaks centered at
generate the desired polymers via ROP, as outlined by Way- 9107 m/z (BEP) and 9086 m/z (BDP) that correspond to the
mouth and co-workers[29] and shown in Scheme 1. The photo- polymeric materials (Figures S12–S13). Using SEC the average
physical properties of the polymers in the presence and ab- molecular weight (Mw), number average molecular weight (Mn)
sence of LnIII ions were evaluated to determine their ability to and the PDIs of the polymers were determined and are summa-
sensitize LnIII-centered emission. All materials were character- rized in Table 1. Mw and Mn are 7551 and 7331 Da for BEP and
1
ized by H NMR and FTIR spectroscopy, size-exclusion chroma- 8005 and 7797 Da for BDP, and correspond to PDI values close
Scheme 1. Synthesis of the BEP and BDP polymers with m = 6 and 7, respectively.
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to 1, indicating homogeneous distribution of the polymer
weights (Table 1). The 2 kDa PEG has a repeating unit number
of 42, while the chelating units of the polymers have sequences,
m, of 7 and 6 for the BDP and BEP polymers, respectively, as
determined from their Mw values.
Figure 1. FTIR spectra of the BEP (blue) and BDP (red) polymers and PEG
(black) with vibrational assignments.
Table 1. The weight average molecular weight (Mw), number average molec-
ular weight (Mn) and polydispersity indices (PDIs) of the polymers BEP and
BDP and their LnIII systems.
Sample
Mw [Da]
Mn [Da]
PDI
BEP
7462
7667
7487
8798
8897
8804
7245
7443
7199
8625
8723
8631
1.03
1.03
1.04
1.02
1.02
1.02
EuIII-BEP
TbIII-BEP
BDP
EuIII-BDP
TbIII-BDP
Figure 2. Powder XRD diffractograms of the (a) BDP and (b) BEP polymers
(black) and their EuIII (red) and TbIII (green) systems.
The FTIR spectra show the pyridyl C=O stretching vibrations
at 1747 and 1719 cm–1 for the BDP and BEP polymers, respec-
tively. The C=O stretching vibration of the lactone unit appears
at 1591 cm–1 for both polymers (Figure 1). The C–O stretching
vibrations are at 1266 and 1256 cm–1 for BDP and BEP, respec-
tively, as shown in Figure 1, in analogy to what is seen for other
PCs.[14,31] The absence of the pyridyl and lactone C=O stretches
in the FTIR spectrum of the PEG indicates successful synthesis
of the PC-based materials (Figure 1).
the polymers are –32 °C for BEP and –13 °C for BDP, as deter-
mined from DSC measurements (Figure 4a–b), and are compa-
rable to values reported for PCs derived from cyclic carbon-
ates.[25,34]
Powder XRD analyses of the BEP and BDP polymers show
broad amorphous peaks centered at 20° and 18° of 2θ, respec-
tively (Figure 2), consistent with the structure of pure PC.[32]
The absence of crystalline PEG peaks between 10–40° in the
diffractograms also indicates the successful synthesis of the PC-
based materials.[33]
The thermal properties of the new polymers were evaluated.
The TGA curves for both polymers show an initial weight loss
at 100 °C due to evaporation of water and/or loss of small or-
ganic groups (Figure 3). Pyrolysis of the derivatives begins at
200 °C, seen by the loss of the bulk weight that can be attrib-
uted to the cleavage of carbonate groups, while residual chars
of the derivatives remain at 350 °C.[31] Compared to pure PEG,
the polymers are less thermostable as pyrolysis of the former
does not begin until after 300 °C (Figure 3). The Tg values of
Figure 3. TGA curves of 2 kDa PEG (black), BDP (red), and BEP (blue).
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emission in the range 300–500 nm with maxima at 346 nm and
365 nm for BDP and BEP polymers, respectively (Figure 5).
LnIII-containing systems of the polymers were prepared by
stirring optimum ratio amounts of polymer to LnIII ions in aceto-
nitrile overnight (details of determination of the optimum ratio
and synthesis in Supporting Information) and were used as pre-
pared. The systems were characterized by SEC (Figures S11),
powder XRD (Figure 2), TGA (Figures S14a–b), DSC (Figure 4),
1H NMR spectroscopy of the analogous LaIII polymers (Figures
S15a–b) and FTIR spectroscopy (Figure 6a–b). The optimum ra-
tio of polymer to LnIII ions obtained from titration experiments
indicates that every two chelator units bind a single LnIII ion
(Figures S16a–b). The coordination of the LnIII ions by the poly-
mers is supported by 1H NMR spectroscopy, as the proton reso-
nances of the ethyl groups of both BEP and BDP were shifted
following coordination of the diamagnetic LaIII ions (Figures
S15a–b). This is further corroborated by the shift of the pyridyl
C=O stretching vibrations of the BDP and BEP polymers from
1747 and 1719 cm–1 to 1732 and 1738 cm–1, respectively (Fig-
ure 6a–b).
Figure 4. DSC curves of (a) BDP and (b) BEP polymers (black) and their EuIII
(red) and TbIII (green) systems with glass transition temperature, Tg.
The UV/Vis absorption spectra of both polymers lack a well-
defined band, while the excitation spectra of the BEP and BDP
polymers show bands at 289 and 314 nm, respectively (Fig-
ure 5). Excitation of the polymers at these wavelengths leads to
Figure 6. FTIR spectra of the (a) BDP and (b) BEP polymers (black) and their
EuIII (red) and TbIII (green) systems with assignments of the pyridyl and lact-
one C=O group vibrational frequencies.
Analysis of the metal ion-containing polymers by SEC shows
that the coordination of LnIII ions does not induce aggregation
in the polymer samples, as the retention times are the same as
those of the free polymers (Table 1). This results in similar
Figure 5. UV/Vis absorption (dashed), excitation (solid), and emission (dot-
dashed) spectra of the BDP (black) and BEP (red) polymers in acetonitrile at
298 K.
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Mw, Mn, and PDI values of the free polymers and their LnIII- sensitizer of LnIII-centered emission than the BDP polymer; this
containing systems (Table 1). Addition of the LnIII salts to the lower efficiency of sensitized emission is further corroborated
polymers leads to a shift of the diffraction peaks from 20° to by the presence of f–f transitions in the excitation spectrum of
15° for the BEP polymer (Figure 2), as a result of a change in the EuIII system of BDP (Figure 7).
the structural packing of the polymers, most likely caused by
coordination of LnIII to the chelating units of the polymers.[35]
However, no significant shift is observed in the diffractograms
of the BDP polymer indicating that no structural changes of the
BDP polymer occur following LnIII coordination (Figure 2).[35]
The thermal properties of the polymers and their LnIII sys-
tems were investigated by TGA and DSC. The 50 % weight loss
(T–50) of the BDP polymer shifts from 230 °C to 226 and 224 °C
for the EuIII and TbIII systems, respectively (Figure S14a). Simi-
larly, the T–50 of the BEP polymer shifts from 203 °C to 192 and
187 °C for the EuIII and TbIII systems, respectively (Figure S14b).
The Tg of the BEP polymer shifts to higher temperatures after
LnIII salts were incorporated into the polymer. The Tg values of
the EuIII and TbIII systems of BDP polymer shift to –9 and –10 °C,
respectively, from –13 °C (Figure 4a). Similarly, the Tg values of
the EuIII and TbIII systems of the BEP polymer shift to –7 and
Figure 7. Excitation (dot-dashed) and emission (solid) spectra of the EuIII (red)
and TbIII (green) systems of the BDP polymer in acetonitrile at 298 K with
assignment of the emission bands.
–8 °C, respectively, from –32 °C (Figure 4b). By contrast, Lu and
co-workers[14] observed a decrease in the Tg values of the PC
films following coordination of PrIII ions, while Forster and co-
workers[36] observed a decrease in the Tg values of PC films
doped with a [Eu(tta)3(H2O)2] complex. We have attribute the
decrease in the Tg values observed in our polymers to the LnIII
complexes acting as a plasticizer, as seen also by Lu, Forster
and co-workers.[14,36]
We isolated the analogous GdIII-polymer systems, which were
1
3
used to determine the location of the S and T excited states
(Table 2 and Figures S17a–b and S18a–b), through low temper-
ature fluorescence and phosphorescence spectroscopy.[37] The
polymers have similar 1S (ca. 28000 cm–1 for BEP and ca.
3
30000 cm–1 for BDP) and T (ca. 26000 cm–1 for both BEP and
BDP) energies; the 3T energies are adequately positioned to
transfer energy to both EuIII and TbIII (Table 2). Upon excitation
of the LnIII-polymer systems of BEP and BDP at 271 and 276 nm,
5
5
respectively, the typical D0→7FJ(J = 0–4) Eu and D4→7FJ(J = 6–1)
Tb transitions are observed, as seen in Figures 7 and 8. The red
and green emission of EuIII and TbIII are also easily observed
when the LnIII-containing polymers are irradiated at 254 and
365 nm with a handheld UV-lamp, as shown by the photos in
Figure 9a–b. Along with the fact that the absorption and excita-
tion spectra overlap, this indicates that energy is being trans-
ferred from the PC materials to the LnIII ions (Figure 5, Figure 7
and Figure 8). Emission efficiencies are 30 and 31 % for the EuIII
Figure 8. Excitation (dot-dashed) and emission (solid) spectra of the EuIII (red),
TbIII (green), and TmIII (blue) systems of the BEP polymer in acetonitrile at
298 K with assignment of the emission bands.
The emission lifetime decay curves of the LnIII-polymer sys-
and TbIII systems of BEP and 2 % for both the EuIII and TbIII tems were best fitted to first-order exponentials, indicating the
systems for BDP (Table 2). The BEP polymer is thus a better presence of only one LnIII coordination environment (Table 2
Table 2. Singlet, 1S, and triplet, 3T, excited state energies, as well as the emission lifetimes, τ, and quantum yields of emission, Φ, of the LnIII-polymer systems,
determined in acetonitrile at 25.0 ( 0.1) °C.
System
1S [cm–1 [a]
]
3T [cm–1 [a]
]
τ [ms]
Φ [%]
EuIII-BEP
TbIII-BEP
EuIII-BDP
TbIII-BDP
28200 300
29800 50
26000 50
0.797 0.088
1.080 0.003
1.432 0.002
1.621 0.001
30.2 2.7
30.6 2.4
2.3 0.5
2.3 0.4
26000 100
[a] Measured as the GdIII system.[37]
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(0.31, 0.33) typical of pure white light (Figure 10).[41] However,
the CIE coordinates obtained for the BDP polymer that were
closest to pure white light were (0.38, 0.32) for the composition
BDP1Eu184Tb106 (Figure 10). The corresponding emission spectra
of the tricolor systems (Figure 11) show the combined emission
spectra of the polymer, EuIII-centered and TbIII-centered emis-
sions, with the broad band of the BDP and BEP polymers from
5
375 to 450 nm, as well as the typical D0→7FJ(J = 0–4) EuIII and
5D4→7FJ(J = 6–1) TbIII transitions.
Figure 9. Photographs of the LnIII systems of the (a) BEP and (b) BDP polymers
on a glass slide under UV-lamp irradiation showing the plain polymer on
top and the red EuIII, and green TbIII emissive polymers, respectively, at the
bottom.
and Figures S19a–b and S20a–b). In addition, the emission life-
times of the LnIII-BDP polymer systems are higher than those
of the LnIII-BEP polymer systems, showing that quenching of
the emission by high energy oscillators (O–H, C–H or N–H) is
more competitive in the LnIII-BEP systems than in the case of
Figure 10. CIE chromaticity diagram (1931 CIE standard) of the LnIII systems
of the BEP1Eu1.8Tb28 and BDP1Eu184Tb106 systems in acetonitrile. The inset
shows the photographs of acetonitrile solutions of these systems, BEP (left)
and BDP (right), under 254 nm UV irradiation.
3
the LnIII-BDP systems.[6] Despite similar T energies of the poly-
mers, only the BEP polymer is capable of sensitizing blue TmIII-
centered emission, as can be seen from the band at 475 nm in
1
Figure 8, corresponding to the G4→1H6 transition.[38] Recently,
our group reported the first example of a metallopolymer with
norbornene-based backbone and pyridine-2,6-bis(oxazoline)
pendants that sensitized blue TmIII-centered emission in the
solid-state.[39] Thus, the BEP polymer is another rare example of
a polymer capable of sensitizing blue TmIII-centered emission.
However, since the energy transfer is inefficient, the emission
lifetime and quantum yield could not be determined reliably.
The ability of these systems to emit different colors
prompted us to investigate the ability of a combined material
for white light emission. The EuIII and TbIII-based systems were
used as the red and green components, while the non-metal-
containing polymers were used as the blue-emitting compo-
nent in the tricolor system.[1,40] BEP polymer and its EuIII and
TbIII systems with the composition BEP1Eu1.8Tb28, where the
subscripts indicate the proportion of each component, result in
a tuning of the color to yield a material with CIE coordinates
Figure 11. Emission spectra of the BEP1Eu1.8Tb28 (bottom) and BDP1Eu184Tb106
(top) LnIII systems in acetonitrile used to determine the CIE coordinates.
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at 104 counts with 11 ms range. The polymer excited 1S and 3T
state energies were obtained from the fluorescence and phosphor-
escence spectra of the GdIII-containing systems at 77 K[37] after de-
convolution of the spectra into their Franck–Condon progression.
Conclusions
We have synthesized two new polycarbonate-based materials
capable of chelating LnIII ions and sensitizing LnIII-centered
emission. Of the two materials, the BEP polymer is a better The LnIII emission efficiencies, Φ, of the polymers were determined
sensitizer with emission efficiencies of 30 and 31 % for EuIII and
using Equation (1).
TbIII emission, respectively. The BEP polymer is also capable of
2
m
mST
nx
Φ = ΦST( x )( 2) (1)
sensitizing blue TmIII-centered emission. The LnIII-centered sen-
sitization ability of the polymers was further explored for white-
color generation; the BEP1Eu1.8Tb28 system displays CIE coordi-
nates (0.31, 0.33) and is thus a good white light emitter.
These two new materials, and most notably the BEP-based
material, have the potential to be used in multicolor displays as
red, green, and blue emitting LnIII-polymers, or in combination
for white light generation.
nST
In Equation (1), m is the slope and n is the refractive index of the
solvent. The subscripts ST and x denote the standard and polymer
samples, respectively. Cs3[Eu(dpa)3] and Cs3[Tb(dpa)3] in 0.1
M buff-
ered Tris/HCl (pH ≈ 7.4) aqueous solutions were used as standards.
The emission efficiency was 0.24 for the EuIII and 0.22 for the TbIII
standard.[42] The samples and standards were excited at 282 nm.
Acknowledgments
Experimental Section
NMR Spectroscopy: H and 13C NMR spectra were recorded using
a Varian NMR instrument operating at 400 or 500 MHz, and the
samples referenced against tetramethylsilane [Si(CH3)4]. All chemi-
cal shifts, δ, are reported in ppm.
The National Science Foundation (NSF-CHE 1363325 to Ana
de Bettencourt-Dias and NSF-CHE 1429768 for acquisition of
the powder diffractometer) is gratefully acknowledged for sup-
porting this work.
1
FTIR Spectroscopy: Infrared spectra were acquired using a Nicolet
6700 FTIR instrument in ATR mode. The spectra were collected in
the 4000–600 cm–1 range at 4 cm–1 resolution and 64 scans per
spectrum. The instrument was corrected for CO2 and H2O before
data acquisition.
Keywords: Lanthanides · Polycarbonates · Luminescence ·
White light · Sensitizers
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SEC Data: The data were collected on an instrument composed
of a CTO-20AC Prominence column oven and RID-10A Shimadzu
refractive index detector at a flow rate of 1.0 mL/min and 40 °C
oven temperature. The calibration was done using polystyrene stan-
dards in THF.
Mass Spectrometry: The electrospray ionization mass spectrome-
try (ESI-MS) data of the compounds were acquired with a Waters
Micromass ZQ quadrupole in positive ion mode at low resolution.
The polymer data was acquired on a Bruker Microflex system in
linear positive mode. For MALDI-TOF, the polymer samples (1 mg/
mL) and a universal matrix (3 mg/mL) were mixed in acetonitrile
and applied on the target plate. After drying, a NaCl solution (2 mg/
mL) was applied to the same area on the target plate and dried.
TGA and DSC Data: The TGA data were acquired on a Q50 TA
instrument operating at 5 °C/min in the range 20–500 °C, while the
DSC data were acquired on a Q20 TA instrument operating at
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Received: June 4, 2017
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Sensitization of Ln Emission
Functionalized polycarbonates sensi-
tize red, green, and blue emission from
EuIII, TbIII, and TmIII, respectively.
R. A. Tigaa, X. Aerken, A. Fuchs,
A. de Bettencourt-Dias* ................... 1–9
Sensitization of LnIII (Ln = Eu, Tb,
Tm) Ion Luminescence by Function-
alized Polycarbonate-Based Materi-
als and White Light Generation
DOI: 10.1002/ejic.201700655
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