Detection of dimers by 19F NMR in CdF2 doped with ErF3 and YbF3

Mustafa, M. R.; Jones, W. E.; McGarvey, Bruce R.; Greenblatt, Martha; Banks, E.

doi:10.1063/1.430855

Cited by 36 publications

(3 citation statements)

References 30 publications

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“…The S / N of the F1 resonance is considerably reduced, and the center of gravity shifts to −34 ppm (compared to −23.1 ppm in the spectrum of 2 ). The increased broadening of the powder patterns with higher sample doping arises predominantly from paramagnetic relaxation induced by unpaired electrons and possibly anisotropic broadening resulting from dipolar coupling with the unpaired spin density on the Yb atom. , The extreme broadening makes it impossible to accurately measure the isotropic chemical shift; however, the apparent negative shift may result from a pseudo-contact interaction with the unpaired electron . The most important feature of the 19 F NMR spectra of 3 and 4 is the absence of intense, unshifted, and unbroadened resonances, indicating that the Yb 3+ dopants are homogeneously distributed throughout the LaF 3 NP cores.…”

Section: Resultsmentioning

confidence: 99%

Multinuclear Solid-State NMR Spectroscopy of Doped Lanthanum Fluoride Nanoparticles

Sudarsan

Sivakumar

et al. 2007

J. Am. Chem. Soc.

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Multinuclear solid-state NMR spectroscopy and powder X-ray diffraction (XRD) experiments are applied to comprehensively characterize a series of pure and lanthanide-doped LaF3 nanoparticles (NPs) that are capped with di-n-octadectyldithiophosphate ligands (Ln3+ = diamagnetic Y3+ and Sc3+ and paramagnetic Yb3+ ions), as well as correlated bulk microcrystalline materials (LaF3, YF3, and ScF3). Solid-state 139La and 19F NMR spectroscopy of bulk LaF3 and the LaF3 NPs reveal that the inorganic core of the NP retains the LaF3 structure at the molecular level; however, inhomogeneous broadening of the NMR powder patterns arises from distributions of 139La and 19F NMR interactions, confirming a gradual change in the La and F site environments from the NP core to the surface. 139La and 19F NMR experiments also indicate that low levels (5 and 10 mol %) of Ln3+ doping do not significantly change the LaF3 structure in the NP core. Similar doping levels of paramagnetic Yb3+ ions severely broaden 19F resonances, but only marginally effect 139La powder patterns, suggesting that the dopant ions are uniformly distributed throughout the NP core and occupy vacant La sites. Measurements of 139La T1 and T2 relaxation constants are seen to vary between the bulk material and NPs and between samples with diamagnetic and paramagnetic dopants. 45Sc NMR experiments confirm that the dopants are integrated into the La sites of the LaF3 core. Solid-state 1H and 31P magic-angle spinning (MAS) NMR spectra aid in probing the nature of the capping ligands and their interactions at the NP surface. 31P cross-polarization (CP)/MAS NMR experiments identify not only the dithiophosphate head groups but also thiophosphate and phosphate species which may form during NP synthesis. Finally, 19F-31P CP/MAS and 1H MAS experiments confirm that ligands are coordinated to the NP surface.

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Section: Resultsmentioning

confidence: 99%

Multinuclear Solid-State NMR Spectroscopy of Doped Lanthanum Fluoride Nanoparticles

Sudarsan

Sivakumar

et al. 2007

J. Am. Chem. Soc.

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“…In addition to the main resonance from the bulk of the lattice fluorides, weaker anisotropic resonances for two types of fluoride ions were detected (12,13); one having axial symmetry about the [111] axes and the other one with its symmetry axis along the [100] axis. The [111] resonances were identified as the lattice fluorides adjacent to one rare earth ion.…”

Section: F Nmr In Cdf2:yb 3+mentioning

confidence: 97%

“…The rgF NMR measurement of CdF2 doped with Er a+ and Yb 3+ was undertaken in the hope of finding further evidence for the mechanism responsible for the unusual properties of CdF2 doped with rare earth ions. In addition to the main resonance from the bulk of the lattice fluorides, weaker anisotropic resonances for two types of fluoride ions were detected (12,13); one having axial symmetry about the [111] axes and the other one with its symmetry axis along the [100] axis. The [111] resonances were identified as the lattice fluorides adjacent to one rare earth ion.…”

Section: F Nmr In Cdf2:yb 3+mentioning

confidence: 99%

CdF2 : YbF3 : ErF3—An Efficient Infrared to Visible Upconverting System

Greenblatt¹,

Banks²

1977

J. Electrochem. Soc.

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Single crystals of CdF2 doubly doped with ~FE and ErF3 efficiently convert infrared radiation (~0.93 ~m) from a Si: GaAs diode to red and green light. By varying the Yb concentration, phosphors have been made which produce a red or green visual response. For the series of crystal samples of CdF2:1% ErFs: 1-10% u studied: at YbF3 concentrations below 3%, only red Er 3+ emission peaks were observed (6450-6800A); at 3% YbF3, red and green spectra (5300-5700A) were observed, the green bands being much less intense; the most intense phosphor contained 10 mole l~ercent (m/o) Yb ~+, and the green intensity was an order of magnitude higher than the red. Charge compensation by NaF of the rare earth ions in CdF2:I% ErFs:10% YbF3 greatly reduces the intensity of emission bands, as well as the intensity of the absorption band at 976 nm, in agreement with previous studies of the absorption spectra properties of the YbFE: Cd.F~ system (1). Recent results of 19F NMR of single crystals of CdF2 containing high concentrations of YbF8 and ErFs, respectively, indicate that most of the rare earth ions and their associated interstitial fluorides are found in (M~+-F-)~ dimers in the crystal (2). The intense absorption band observed at 976 nm in Yb~+-doped CdF2 can be assigned to this dimer, which is destroyed by the use of Na + as a charge compensator in place of interstitial fluoride, the native charge compensating defect. Similarly, as the accepted mechanism of the infrared-to-visible conversion in the Yb ~+ sensitized Er ~+ activated systems involves the transfer of two infrared photons from Yb E+ to ErS+, phosphor emission by diode excitation will decrease when the (M3+-F-)2 complex is destroyed by NaF substitution. The 976 nm strong absorption band was also observed in samples (10% Yb, 1% Er) prepared with 1-50 m/o of CaF2 substituted for CdF2 without appreciable decrease in the intensity; however the emission intensities of both green and red bands were significantly enhanced for all of the samples codoped with CaF2. There appears to be a plateau for the compositions 1.5-3% CaF2 and a decrease in the 4.5 and 10% CaF2, samples. Of all the materials investigated to date, YFE and BaYF5 codoped with Yb 3+ and Er 8+ are reported to be the most efficient upconverting systems with a quantum efficiency between 10-4 and 10--3 ( h = 0.97 ~m). The quantum efficiency of CdF2:10% YbFE: 1% ErF3 is found to be 0.23% and that of CdF2: 10% YbFE: 1% ErF3: 2.5% CaF2, 0.70%. These values were obtained under intense excitation with a GaAs diode. Lower values might be found at lower excitation densities.Infrared excited visible fluorescence has attracted considerable attention in recent years (1-5). In combination with GaAs:Si diodes emitting in the near infrared (0.91-1 ~m), phosphor materials capable of converting infrared to visible light are potential display or infrared detecting devices.All the known phosphors of this class use trivalent rare earth ions. The systems which produce the brightest visible light use Yb E+ as the sensitizer with Er a+...

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Anwendung von SEPIL auf die Festkörper‐Defektchemie von Fluoriten und die extreme anorganische Spurenanalyse

et al. 1979

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Obwohl seit vielen Jahren bekannt ist, daB die Spektren der Lanthanoid-Ionen (Ionen der Seltenerdmetalle) AufschluB uber Phanomene im Nahbereich dieser Ionen in Festkorpern geben konnen, wurde die Spektroskopie von Lanthanoiden nicht sehr haufig zum Studium komplexer Materialien angewendet, da die Klassifizierung der resultierenden Spektren problematisch ist. Die Einfiihrung abstimmbarer Laser hat dieses Problem gelost. Durch selektive Lumineszenzanregung der als Sonde dienenden Ionen (SEPIL = selectively exciting probe ion Zuminescence) ist es moglich, Fluoreszenz-und Anregungsspektren von Ionen zu erhalten, die in einer einzigen Art von kristallographischer Umgebung vorliegen. In diesem Aufsatz werden zwei Anwendungen der Methode besprochen. Die erste ist das Studium der Defektchemie von Fluoriten (Verbindungen mit CaF2-Gitter). Die Methode ergibt einzigartige Informationen uber die Festkorperchemie, so daB vie1 vom unerklarten Verhalten dieser wichtigen Stoffklasse verstandlich wird. Die zweite Anwendung ist die extreme Spurenanalyse. Dazu wird das Assoziat aus dem zu analysierenden Ion und dem als Sonde fungierenden Ion untersucht. In diesem Assoziat lassen sich die spezifischen Kristallfeld-Niveaus der Sonde selektiv anregen, so da8 Spuren des zu analysierenden Ions mit hoher Selektivitat und Empfindlichkeit nachgewiesen werden konnen. EinfuhrungDie optische Spektroskopie von lanthanoid-dotierten Stoffen wird seit vielen Jahren untersucht['l. Die ersten Arbeiten wurden unternommen, um die physikalischen Ursachen der charakteristischen, scharflinigen Spektren und der starken Fluoreszenz der Lanthanoide (Sel tenerdmetalle) verstehen zu l e r n e~~[~.~I .Die Entdeckung, daB viele Lanthanoidverbin-[*]Prof.

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Detection of dimers by 19F NMR in CdF2 doped with ErF3 and YbF3

Cited by 36 publications

References 30 publications

Multinuclear Solid-State NMR Spectroscopy of Doped Lanthanum Fluoride Nanoparticles

Multinuclear Solid-State NMR Spectroscopy of Doped Lanthanum Fluoride Nanoparticles

CdF2 : YbF3 : ErF3—An Efficient Infrared to Visible Upconverting System

Anwendung von SEPIL auf die Festkörper‐Defektchemie von Fluoriten und die extreme anorganische Spurenanalyse

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