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One-Pot Solvothermal Synthesis of Highly Emissive, Sodium-Codoped, LaF? and BaLaF? Core-Shell Upconverting Nanocrystals.

ABSTRACT: We report a one-pot solvothermal synthesis of sub-10 nm, dominant ultraviolet (UV) emissive upconverting nanocrystals (UCNCs), based on sodium-codoped LaF? and BaLaF? (0.5%Tm; 20%Yb) and their corresponding core@shell derivatives. Elemental analysis shows a Na-codopant in these crystal systems of ~20% the total cation content; X-ray diffraction (XRD) data indicate a shift in unit cell dimensions consistent with these small codopant ions. Similarly, X-ray photoelectron spectroscopic (XPS) analysis reveals primarily substitution of Na? for La3+ ions (97% of total Na? codopant) in the crystal system, and interstitial Na? (3% of detected Na?) and La3+ (3% of detected La3+) present in (Na)LaF? and only direct substitution of Na? for Ba2+ in Ba(Na)LaF?. In each case, XPS analysis of La 3d lines show a decrease in binding energy (0.08-0.25 eV) indicating a reduction in local crystal field symmetry surrounding rare earth (R.E.3+) ions, permitting otherwise disallowed R.E. UC transitions to be enhanced. Studies that examine the impact of laser excitation power upon luminescence intensity were conducted over 2.5-100 W/cm² range to elucidate UC mechanisms that populate dominant UV emitting states. Low power saturation of Tm3+ ³F? and ³H? states was observed and noted as a key initial condition for effective population of the ¹D? and ¹I? UV emitting states, via Tm-Tm cross-relaxation.

SUBMITTER: Stecher JT

PROVIDER: S-EPMC5304608 | biostudies-literature | 2014 Jan

REPOSITORIES: biostudies-literature

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One-Pot Solvothermal Synthesis of Highly Emissive, Sodium-Codoped, LaF₃ and BaLaF₅ Core-Shell Upconverting Nanocrystals.

Stecher Joshua T JT Rohlfing Anne B AB Therien Michael J MJ

Nanomaterials (Basel, Switzerland) 20140108 1

We report a one-pot solvothermal synthesis of sub-10 nm, dominant ultraviolet (UV) emissive upconverting nanocrystals (UCNCs), based on sodium-codoped LaF₃ and BaLaF₅ (0.5%Tm; 20%Yb) and their corresponding core@shell derivatives. Elemental analysis shows a Na-codopant in these crystal systems of ~20% the total cation content; X-ray diffraction (XRD) data indicate a shift in unit cell dimensions consistent with these small codopant ions. Similarly, X-ray photoelectron spectroscopic (XPS) analysi ...[more]

PMID: 28348286

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Project description:Recently, the functionalization of nanoparticles, either within themselves or on the outer surface and its application in medicine, turned out to be the ultimate goal of nanotechnology. By providing these nanoparticles with chemical functional groups, one can force the nanoparticles to target the markers of the particular diseases or to measure the quantity and distribution of various intracellular species. In this paper, we report our development of a pH-responsive nanocomposite based on lanthanide-doped upconverting nanoparticles (UCNPs). Through multiphoton absorption and energy migration between spatially separated Nd3+, Yb3+, and Tm3+ in a three-layered NaYF4 host coated with FITC (fluorescein-5-isothiocyanate), this nanocomposite can measure the pH with high sensitivity. The fundamental acidity measurement is based on the pH-dependent equilibrium of the bright and dark states of FITC. The tremendous advantages of this system, regarding the pH measurement, come from the fact that the versatility of UCNP-imaging can fully be exploited. This includes the fact that (a) the optical wavelengths for the sensitization (980 nm and/or 808 nm) and the emission bands (UV, visible) are well separated, (b) the spectral overlap between FITC (absorption) and Tm3+ (emission) is substantially high, (c) there is no background signal due to the near-infrared laser, and (d) the signals are consistent regardless of the fluctuations by monitoring the ratio of blue band with respect to the unaffected self-reference (red and near-infrared bands). Moreover, the double shell structure is obviously superior to the core-shell structure in that it enhances the spectral separation between the sensitizer and the emitter in the upconversion process, inhibiting any unnecessary contamination in the spectra. Finally, it is noteworthy that Yb3+ plays crucial roles as a sensitizer at 980 nm excitation and a bridge above which 808 nm excitation migrates from Nd3+ to Tm3+ via the Yb3+ excited state.

Dataset Information

One-Pot Solvothermal Synthesis of Highly Emissive, Sodium-Codoped, LaF? and BaLaF? Core-Shell Upconverting Nanocrystals.

Publications

One-Pot Solvothermal Synthesis of Highly Emissive, Sodium-Codoped, LaF₃ and BaLaF₅ Core-Shell Upconverting Nanocrystals.

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