Rare-Earth-Modified Titania Nanoparticles: Molecular Insight into Synthesis and Photochemical Properties.

A molecular precursor approach to titania (anatase) nanopowders modified with different amounts of rare-earth elements (REEs: Eu, Sm, and Y) was developed using the interaction of REE nitrates with titanium alkoxides by a two-step solvothermal-combustion method. The nature of an emerging intermetallic intermediate was revealed unexpectedly for the applied conditions via a single-crystal study of the isolated bimetallic isopropoxide nitrate complex [Ti2Y(iPrO)9(NO3)2], a nonoxo-substituted compound. Powders of the final reaction products were characterized by powder X-ray diffraction, scanning electron microscopy-energy-dispersive spectroscopy, Fourier transform infrared, X-ray photoelectron spectroscopy, Raman spectroscopy, and photoluminescence (PL). The addition of REEs stabilized the anatase phase up to ca. 700 °C before phase transformation into rutile became evident. The photocatalytic activity of titania modified with Eu3+ and Sm3+ was compared with that of Degussa P25 titania as the control. PL studies indicated the incorporation of Eu and Sm cations into titania (anatase) at lower annealing temperatures (500 °C), but an exclusion to the surface occurred when the annealing temperature was increased to 700 °C. The efficiency of the modified titania was inferior to the control titania while illuminated within narrow wavelength intervals (445-465 and 510-530 nm), but when subjected to a wide range of visible radiation, the Eu3+- and Sm3+-modified titania outperformed the control, which was attributed both to doping of the band structure of TiO2 with additional energy levels and to the surface chemistry of the REE-modified titania.

Binuclear Lanthanide-Radical Complexes Featuring Two Centers with Different Magnetic and Luminescence Properties.

Binuclear complexes with general formula [Ln2(hfac)6(H2O)2(dppnTEMPO)] (LnIII = Gd, Tb, and Dy) have been obtained using the paramagnetic ligand 1-piperidinyl-4-[(diphenylphosphinyl)amino]-2,2,6,6-tetramethyl (dppnTEMPO) as a bridge. One of the lanthanide ions is ferromagnetically coupled with the TEMPO moiety. Two of the complexes (Dy and Tb) show slow relaxation of the magnetization, and the non-magneto-equivalence of the two LnIII ions was clearly observed. The ab initio CASSCF calculations were employed to confirm this behavior, as well as to rationalize the Ln-Rad interaction. The simulations of the magnetic properties were allowed by the insights given by the calculations. The inequivalence of the TbIII ions was also proved by emission spectroscopy.

Defect induced tunable near infrared emission of Er-CeO2 by heterovalent co-dopants.

We investigate the effects of heterovalent co-dopants on the structural and emission properties of 1% Er-CeO2 nanoparticles. The CeO2 oxide host was selected on the basis of its fairly well-understood defect chemistry in either a pure or doped state. As a luminescent activator, Er is acknowledged as an interesting element due to its rich luminescence and excitation properties spanning the visible to near-infrared range. The optically inactive trivalent La and monovalent Li metal ions with a concentration of up to 20% were chosen to presumably generate a variable amount of defects in the Er-CeO2 lattice. It was found that La and Li co-dopants induced distinct changes related to the size, lattice constant, bandgap energy, lattice and surface defects of Er-CeO2. As a result of these changes, a strong modulation of the luminescence intensity and shape was measured using a suite of excitation conditions (charge-transfer absorption band of CeO2, direct/up-conversion into Er absorptions and X-ray excitation modes). The use of Eu as a luminescent probe offered additional information concerning the effects of La/Li co-doping on the local structure surrounding the luminescent activator. Remarkably high percentages of 90 and 98% of the total emission of Er measured between 500 and 1100 nm are measured in the near-infrared region at 980 nm under X-ray and up-conversion excitation at ∼1500 nm, respectively. The optical properties suggest that Li, Er co-doped CeO2 has good potential for therapy and biological imaging.

Pure and almost pure NIR emission of Tm and Tm,Yb-CeO2 under UV, X-ray and NIR up-conversion excitation: key roles of level selective antenna sensitization and charge-compensation.

Herein, we report on the pure and almost pure near-infrared (NIR) emission at around 807 nm observed for Tm(Yb) (co)-doped CeO2 nanoparticles (NPs) under UV, X-ray and NIR up-conversion excitation. The optical responses are attributed to the low-lying charge-transfer of CeO2 that acts as a selective antenna sensitizer of the Tm (3)H4 emission and Yb doping that lowers the local symmetry at Tm sites and introduces additional phonon modes. Selective antenna sensitization is also observed for Er/Ho (Yb) (co)-doped CeO2 NPs. To the best of our knowledge, this is a first study which correlates the down- and up-conversion emission properties of lanthanide(s)-(co) dopants with the CeO2 structure highlighting also the outstanding potential of these NPs in high-penetration tissue imaging and therapy.

Cyanomethylene-bis(phosphonate)-based lanthanide complexes: structural, photophysical, and magnetic investigations.

The syntheses, structural investigations, magnetic and photophysical properties of a series of 10 lanthanide mononuclear complexes, containing the heteroditopic ligand cyanomethylene-bis(5,5-dimethyl-2-oxo-1,3,2λ(5)-dioxa-phosphorinane) (L), are described. The crystallographic analyses indicate two structural types: in the first one, [Ln(III)(L)3(H2O)2]·H2O (Ln = La, Pr, Nd), the metal ions are eight-coordinated within a square antiprism geometry, while the second one, [Ln(III)(L)3(H2O)]·8H2O (Ln = Sm, Eu, Gd, Tb, Dy, Ho, Er), contains seven-coordinated Ln(III) ions within distorted monocapped trigonal prisms. Intermolecular hydrogen bonding between nitrogen atoms of the cyano groups, crystallization, and coordination water molecules leads to the formation of extended supramolecular networks. Solid-state photophysical investigations demonstrate that Eu(III) and Tb(III) complexes possess intense luminescence with relatively long excited-state lifetimes of 530 and 1370 µs, respectively, while Pr(III), Dy(III), and Ho(III) complexes have weak intensity luminescence characterized by short lifetimes ranging between a few nanoseconds to microseconds. The magnetic properties for Pr(III), Gd(III), Tb(III), Dy(III), and Ho(III) complexes are in agreement with isolated Ln(III) ions in the solid state, as suggested by the single-crystal X-ray analyses. Alternating current (ac) susceptibility measurements up to 10 kHz reveal that only the Ho(III) complex shows a frequency-dependent ac response, with a relaxation mode clearly observed at 1.85 K around 4500 Hz.

Structural, down- and phase selective up-conversion emission properties of mixed valent Pr doped into oxides with tetravalent cations.

We report on structure-property relationships in Pr-doped CeO2 and ZrO2 using X-ray diffraction (XRD), Raman, UV to Vis Diffuse Reflectance (DR-UV/Vis), X-ray Photoelectron (XPS), and luminescence (PL) spectroscopies. Both 3+ and 4+ valence states of Pr are evidenced, irrespective of the host and calcination temperature, T (T = 500 and 1000 °C) with consequences on absorption, surface, vibrational and luminescence properties. Only zirconia represents a suitable host for Pr(3+) luminescence. The distinct trivalent Pr centers and their excitation mechanism are identified in relation to the tetragonal and monoclinic phases of ZrO2. A near-infrared to visible up-conversion (UPC) emission of Pr(3+) is observed upon excitation at 959 nm which occurs, most probably, via a two-photon excited state process. By using a multi-wavelength, time-gated excitation, the UPC process is established as phase selective, i.e. only Pr(3+) located in the monoclinic sites of the mixed phase, monoclinic and tetragonal ZrO2 (T = 1000 °C) contribute to the UPC emission. We believe that, besides the local symmetry, a key role in phase selective UPC is played by the presence of Pr(3+) low-lying 4f 5d levels. To the best of our knowledge, this is the first report of phase selective up-conversion emission in a lanthanide doped multi-phase host.

Local structure and nanoscale homogeneity of CeO2-ZrO2: differences and similarities to parent oxides revealed by luminescence with temporal and spectral resolution.

Although homogeneity at the atomic level of CeO2-ZrO2 with a Ce/Zr atomic ratio close to unity is considered to be one of the main causes for the increased total oxygen storage capacity (OSC), the characterization approaches of homogeneity remain a major challenge. We propose a simple, yet effective method, to assess both structural and compositional homogeneity of CeO2-ZrO2 by using Eu(3+) luminescence measured with time and dual spectral resolution (emission and excitation). For Eu(3+)-CeO2-ZrO2 calcined at 750 °C, the X-ray diffraction, Raman and High-Resolution Transmission Electron Microscopy data converge to a single pseudo-cubic phase. However, the evolution of Eu(3+)-delayed luminescence from cubic ceria-like to tetragonal zirconia-like emission reveals the formation of CeO2- and ZrO2-rich nanodomains and provides evidence for early phase separation. For Eu(3+)-CeO2-ZrO2 calcined at 1000 °C, the emission of Eu(3+) reveals both structural and compositional inhomogeneity. Our study identifies the differences between the local structure properties of CeO2 and ZrO2 parent oxides and CeO2-ZrO2 mixed oxide, also confirming the special chemical environment of the oxygen atoms in the mixed oxide as reported earlier by Extended X-ray Absorption Fine Structure investigations.

Mesoporous anatase TiO2 nanorods as thermally robust anode materials for Li-ion batteries: detailed insight into the formation mechanism.

Uniformly mesoporous and thermally robust anatase nanorods were produced with quantitative yield by a simple and efficient one-step approach. The mechanism of this process was revealed by insertion of Eu(3+) cations from the reaction medium as luminescent probes. The obtained structure displays an unusually high porosity, an active surface area of about 300 m(2) g(-1) and a specific capacity of 167 mA h g(-1) at a C/3 rate, making it attractive as an anode electrode for Li-ion batteries. An additional attractive feature is its remarkable thermal stability; heating to 400 °C results in a decrease in the active surface area to a still relatively high value of 110 m(2) g(-1) with conservation of open mesoporosity. Thermal treatment at 800 °C or higher, however, causes transformation into a non-porous rutile monolith, as commonly observed with nanoscale titania.

Up-conversion emission in transition metal and lanthanide co-doped systems: dimer sensitization revisited.

Lanthanide (Ln) co-doped transition metal (TM) upconversion (UC) co-doped systems are being intensively investigated for their exciting applications in photonics, bioimaging, and luminescence thermometry. The presence of TM, such as Mo6 + /W6 +, Mn2 +, or Fe3 + determines significant changes in Ln UC emission, such as intensity enhancement, colour modulation, and even the alteration of the photon order. The current mechanism assumes a ground-state absorption/excited-state absorption (ESA/GSA) in TM-Yb dimer followed by direct energy transfer to Er/Tm excited states. We revisit this mechanism by addressing two issues that remain ignored: a dynamical approach to the investigation of the upconversion mechanism and the intrinsic chemical complexity of co-doped TM, Ln systems. To this aim, we employ a pulsed, excitation variable laser across a complete set of UC measurements, such as the emission and excitation spectra and emission decays and analyze multiple grains with transmission electron microscopy (TEM). In the Mo co-doped garnet, the results sustain the co-existence of Mo-free garnet and Mo oxide impurity. In this Mo oxide, the Er upconversion emission properties are fully explained by a relatively efficient sequential Yb to Er upconversion process, with no contribution from Yb-Mo dimer sensitization.

Order and disorder effects in nano-ZrO2 investigated by micro-Raman and spectrally and temporarily resolved photoluminescence.

Pure and europium (Eu(3+)) doped ZrO(2) synthesized by an oil-in-water microemulsion reaction method were investigated by in situ and ex situ X-ray diffraction (XRD), ex situ Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), steady state and time-resolved photoluminescence (PL) spectroscopies. Based on the Raman spectra excited at three different wavelengths i.e. 488, 514 and 633 nm and measured in the spectral range of 150-4000 cm(-1) the correlation between the phonon spectra of ZrO(2) and luminescence of europium is clearly evidenced. The PL investigations span a variety of steady-state and time resolved measurements recorded either after direct excitation of the Eu(3+) f-f transitions or indirect excitation into UV charge-transfer bands. After annealing at 500 °C, the overall Eu(3+) emission is dominated by Eu(3+) located in tetragonal symmetry lattice sites with a crystal-field splitting of the (5)D(0)-(7)F(1) emission of 20 cm(-1). Annealing of ZrO(2) at 1000 °C leads to a superposition of Eu(3+) emissions from tetragonal and monoclinic lattice sites with monoclinic crystal-field splitting of 200 cm(-1) for the (5)D(0)-(7)F(1) transition. At all temperatures, a non-negligible amorphous/disordered content is also measured and determined to be of monoclinic nature. It was found that the evolutions with calcination temperature of the average PL lifetimes corresponding to europium emission in the tetragonal and monoclinic sites and the monoclinic phase content of the Eu(3+) doped ZrO(2) samples follow a similar trend. By use of specific excitation conditions, the distribution of europium on the amorphous/disordered surface or ordered/crystalline sites can be identified and related to the phase content of zirconia. The role of zirconia host as a sensitizer for the europium PL is also discussed in both tetragonal and monoclinic phases.

One- and two-photon induced emission in heterobimetallic Zn(II)-Sm(III) and Zn(II)-Tb(III) complexes with a side-off compartmental ligand.

Heterobimetallic [Zn(II)Ln(III)] complexes have been obtained using a compartmental Schiff-base ligand, H(2)valdmpn, resulting from the 2:1 condensation between o-vanillin and 2,2-dimethyl-propilenediamine: [Zn(H(2)O)(valdmpn)Sm(O(2)NO)(3)] 1, [Zn(H(2)O)(valdmpn)Tb(O(2)NO)(3)] 2a, [Zn(H(2)O)(valdmpn)Tb(O(2)NO)(3)]·H(2)O 2b, and [Zn(H(2)O)(valdmpn)Gd(O(2)NO)(3)]·H(2)O 3. The crystal structures of 1, 2b, and 3 have been solved. Compounds 1 and 2a crystallize in a non-centrosymmetric space group (P2(1)2(1)2(1)), being isomorphous. Crystals 2b and 3 are also isomorphous (space group P1[combining macron]). The complex entities in the four crystals are similar and their structures consist of binuclear species with the pentacoordinated zinc(II) ion hosted into the N(2)O(2) compartment and the lanthanide(III) ion in the large, open compartment, with a coordination number of 10. The photophysical properties of the four compounds have been investigated. Strong visible excited (excitation tails extend up to 420-430 nm) one photon antenna sensitization was obtained with the samarium(III) and terbium(III) derivatives. Following femtosecond Ti:Sapphire laser at λ(ex) = 775 nm, both second-harmonic generation at λ(em) = 775/2 nm and two-photon induced emission in the VIS range were obtained, extending thus the excitation range of these complexes from the VIS to the NIR spectral range. The two-photon induced emission and second harmonic generation effect for a samarium(III) complex are reported for the first time.

Study of the luminescent and magnetic properties of a series of heterodinuclear [Zn(II)Ln(III)] complexes.

Herein, we report the synthesis, structural investigation, and magnetic and photophysical properties of a series of 13 [Zn(II)Ln(III)] heterodinuclear complexes, which have been obtained employing a Schiff-base compartmental ligand derived from o-vanillin [H(2)valpn = 1,3-propanediylbis(2-iminomethylene-6-methoxy-phenol)]. The complexes have been synthesized starting from the [Zn(valpn)(H(2)O)] mononuclear compound and the corresponding lanthanide nitrates. The crystallographic investigation indicated two structural types: the first one, [Zn(H(2)O)(valpn)Ln(III)(O(2)NO)(3)], contains 10-coordinated Ln(III) ions, while in the second one, [Zn(ONO(2))(valpn)Ln(III)(H(2)O)(O(2)NO)(2)]·2H(2)O, the rare earth ions are nine-coordinated. The Zn(II) ions always display a square-pyramidal geometry. The first structural type encompasses the larger Ln ions (4f(0)-4f(9)), while the second is found for the smaller ions (4f(8)-4f(11)). The dysprosium derivative crystallizes in both forms. Luminescence studies for the heterodinuclear compounds containing Nd(III), Sm(III), Tb(III), Dy(III), and Yb(III) revealed that the [Zn(valpn)(H(2)O)] moiety acts as an antenna. The magnetic properties for the paramagnetic [Zn(II)Ln(III)] complexes have been investigated.

Surface versus volume effects in luminescent ceria nanocrystals synthesized by an oil-in-water microemulsion method.

Pure and europium (Eu(3+)) doped cerium dioxide (CeO(2)) nanocrystals have been synthesized by a novel oil-in-water microemulsion reaction method under soft conditions. In-situ X-ray diffraction and RAMAN spectroscopy, high-resolution transmission electron microscopy, UV/Vis diffuse-reflectance and Fourier transform infrared spectroscopy as well as time-resolved photoluminescence spectroscopy were used to characterize the nanaocrystals. The as-synthesized powders are nanocrystalline and have a narrow size distribution centered on 3 nm and high surface area of ~250 m(2) g(-1). Only a small fraction of the europium ions substitutes for the bulk, cubic Ce(4+) sites in the europium-doped ceria nanocrystals. Upon calcination up to 1000 °C, a remarkable high surface area of ~120 m(2) g(-1) is preserved whereas an enrichment of the surface Ce(4+) relative to Ce(3+) ions and relative strong europium emission with a lifetime of ~1.8 ms and FWHM as narrow as 10 cm(-1) are measured. Under excitation into the UV and visible spectral range, the europium doped ceria nanocrystals display a variable emission spanning the orange-red wavelengths. The tunable emission is explained by the heterogeneous distribution of the europium dopants within the ceria nanocrystals coupled with the progressive diffusion of the europium ions from the surface to the inner ceria sites and the selective participation of the ceria host to the emission sensitization. Effects of the bulk-doping and impregnation with europium on the ceria host structure and optical properties are also discussed.

Luminescence thermometry based on one-dimensional benzoato-bridged coordination polymers containing lanthanide ions.

Three 1D coordination polymers with benzoate bridges have been assembled in the presence of 18-crown-6-ether (18C6): 1∞[Tb(PhCOO)3(H2O)(EtOH)]·0.5(18C6) 1, 1∞[Eu(PhCOO)3(H2O)2]·0.5(18C6) 2, 1∞[Nd(PhCOO)3(H2O)2]·0.5(18C6) 3. Compounds 2 and 3 are isomorphous. The crown ether molecules co-crystallize with the resulting 1D coordination polymers and play an important role in the supramolecular architecture of the crystals. A molecular alloy was prepared in a similar way to compound 1 using TbCl3·6H2O and EuCl3·6H2O in a molar ratio of 95 : 5. The EuIII ions have statistically substituted the TbIII ions in the host lattice The luminescence thermometry performance of the Tb0.95Eu0.05 system was investigated using pulsed excitation into TbIII absorption at 352 nm. The maximum Sr value is 1.88% K-1 at 80 K which is slightly reduced at 1.60% K-1 at 313 K. Time-gated emission spectroscopy, employed here for the first time, allows us to reduce the spectral overlap of Tb and Eu emissions in the 610 to 625 nm range by 100% at 80 K, from 18 to 9%. Compound 1 as well as the molecular alloy, Tb0.95Eu0.05, show X-ray induced luminescence.

Temperature switch of LMCT role: from quenching to sensitization of europium emission in a Zn(II)-Eu(III) binuclear complex.

The synthesis, structural investigation, and photophysical properties of a new heterobinuclear complex, [Zn(H(2)O)(valpn)Eu(NO(3))(3)], are reported [H(2)valpn = 1,3-propanediylbis(2-iminomethylene-6-metoxy-phenol)]. In the absence of the antenna-type sensitization of europium emission at room temperature, the strongest metal-centered emission was obtained following excitation into the (7)F(0)-(5)D(2) transition at 535 nm. In contrast, at 80 K, the strongest emission of europium was obtained by exciting into the maximum of a high-intensity, low-lying ligand-to-metal charge-transfer band (LMCT) located at approximately 425 nm. The overall temperature-induced changes of the photophysical properties of europium were assigned to the relative location of the LMCT and (3)pi pi* ligand states to the europium excited levels. The results may explain the lack of the antenna effects reported for some of the europium complexes with this type of ligand.

Polymer-microporous host interactions probed by photoluminescence spectroscopy.

Zeolites NaY and ZSM-5 were used as hosts for styrene polymerization after ion-exchange with europium ions. The parent and hybrid, polystyrene coated Eu-NaY (Eu-NaY/PS) and Eu-ZSM-5 (Eu-ZSM-5/PS) zeolites were investigated by using thermal analysis, SEM, PXRD, FT-IR, DR-UV/Vis, steady state and time-resolved photoluminescence spectroscopy. FT-IR spectra evidenced for the interaction between the zeolitic hosts and polystyrene while the PXRD spectra supported for the presence of the polymer inside the channels/pores of Eu-NaY/PS and Eu-ZSM-5/PS materials. The optical properties of Eu-NaY/PS and Eu-ZSM-5/PS were significantly changed relative to those of the parent zeolites, giving further evidence for the presence of polymer inside zeolites. An interesting case is presented by NaY zeolite: following styrene polymerization, the polymer interacted selectively with one of the two main species co-existing inside zeolite while for ZSM-5 a similar effect was not observed.

Time-resolved photoluminescence spectra, lifetime distributions and decay-associated spectra of lanthanide's exchanged microporous-mesoporous materials.

Time-resolved luminescence spectra of europium in parent and silylated microporous-mesoporous materials were analyzed by using the maximum entropy method and global multi-exponential fitting, providing lifetime distributions and decay-associated spectra. Silylation was used as a method for the hydrophobization of the materials surface in order to inhibit the moisture intrusion at the lanthanide's sites. Due to the well-known sensitivity of the europium photoluminescence properties to the local environment, our approach can simplify the description of the complex structure-photoluminescence relationships in terms of the individual europium species that contribute to the total emission of the system.

Optical properties of Nd3+ doped ionic liquid immobilized on mesoporous silica support.

The synthesis of a new material based on Nd3+ ions doped into an imidazolium-type ionic liquid with further immobilization on a mesoporous silica support is reported. The material was investigated by DR-UV/VIS, FT-IR, thermogravimetric analysis, N2 adsorption measurements and time-resolved photoluminescence spectroscopy. The intensity of the near-infrared emission of Nd3+ was weak and the lifetime measured at about 910 nm was 7 micros.

A sensitive near infrared to near-infrared luminescence nanothermometer based on triple doped Ln -Y2O3.

In recent years, luminescence nanothermometers with near infrared light (NIR) emission excited in the NIR range have attracted much attention due to their potential in bio applications. Here, we propose a new nanothermometer based on triple doped 1%Ho, 1%Er, 1%Yb - Y2O3 that operates in the second and third biological windows around 1200 and 1530 nm under pulsed excitation at 905 nm. The NIR emissions were analysed in the temperature range of 298-473 K in terms of intensity, shape and dynamics. The nanothermometer performances were described using the luminescent intensity ratio (LIR) corresponding to the 5I6-5I8 and 4I13/2-4I15/2 emissions transitions of Ho and Er, respectively. A maximum relative sensitivity of 1.5% K-1 was achieved at 309 K, which is among the highest five values reported so far for the NIR to NIR downconversion nanothermometers. The thermometer performance for biological application was assessed in terms of nanothermometer reliability and stability as well as emission shape changes induced by water and custom designed optical phantoms. Combination between use of pulsed excitation and identification of Ln doping configuration offering both excitation and emission in the biological windows represent a solid approach that can be easily translated to other hosts to develop a new class of near infrared nanothermometers.

Imaging dopant distribution across complete phase transformation by TEM and upconversion emission.

Correlating dopant distribution to its optical response represents a complex challenge for nanomaterials science. Differentiating the "true" clustering nature from dopant pairs formed in statistical distribution complicates even more the elucidation of doping-functionality relationship. The present study associates lanthanide dopant distribution, including all significant events (enrichment, depletion and surface segregation), to its optical response in upconversion (UPC) at the ensemble and single-nanoparticle level. A small deviation from the Er nominal concentration of a few percent is able to induce clear differences in Er UPC emission color, intensity, excited-state dynamics and ultimately, UPC mechanisms, across tetragonal to monoclinic phase transformation in rationally designed Er doped ZrO2 nanoparticles. Rare evidence of a heterogeneous dopant distribution leading to the coexistence of two polymorphs in a single nanoparticle is revealed by Z- and phase contrast transmission electron microscopy (TEM). Despite their spatial proximity, Er in the two polymorphs are spectroscopically isolated, i.e. they do not communicate by energy transfer. Segregated Er, which is well imaged in TEM, is absent in UPC, while the minor phase content overlooked by X-ray diffraction and TEM is revealed by UPC. The outstanding sensitivity of combined TEM and UPC emission to subtle deviations from uniform doping in the diluted concentration regime renders such an approach relevant for various functional oxides supporting lanthanide dopants as emitters.