Highly doped NaErF_(4)-based nanocrystals for multi-tasking application

How to engineer single nanocrystal to achieve multiple functions is still a huge challenge.In this work,a novel highly doped rare earth nanocrystal NaErF_(4)@NaGdF_(4)@NaDyF_(4)(Er@Gd@Dy)was designed and fabricated,which exhibits various performances by itself,including the longitudinal(T1)and transverse relaxation time(T2)double-mode magnetic resonance imaging(MRI),upconversion luminescence and down-shifting luminescence.Upon irradiation of 808 nm near-infrared(NIR)light,the upconverted red light can indirectly activate the photo sensitizer Ce6 conjugated on the surface of nanocrystals for photodynamic therapy(PDT).In vivo experiments demonstrate that the nano materials can eradicate notably primary tumors without obvious systematic toxicity.In addition,the longitudinal and transverse relaxation rates of Er@Gd@Dy are 24.83 and 319.86(mmol/L)^(-1)/s,respectively,which are superior to those of the nanocrystals reported previously.Simultaneously,the nanocrystals have the ability to generate NIR-Ⅱlight located at 1530 nm,favorable in bioimaging in deeper tissues.As a consequence,this new nanoplatform will advance the improvement of multimodal imaging guided tumor diagnosis and treatment.

Synergistic effect of crystal structure and concentration quenching on photoluminescence of Er^(3+) doped upconversion nanocrystals

YbF（2.357, YbF3, Ba2 YbF7, and Ba 2 upconversion nanocrystals doped with emitter Er^3＋ ion were synthesized in the same solvent system just with changing the molar ratio of Ba^2＋ to Yb^3＋ in the precursor, which corresponed to the crystal phases of rhombohedral, orthorhombic, tetragonal, and cubic, respectively. All the samples emitted both 660 nm red light and 543/523 nm green light which originated from Er^3＋-4f^n electronic transitions ~4F（9/2-~4I（15/2 and ~4S（3/2/~2H（11/2-~4I（15/2, respectively. It was worth mentioning that YbF 3：Er^3＋, Ba2 YbF7：Er^3＋, and BaF2：Er^3＋ could emit dazzlingly bright light even under the excitation of a 980 nm CW laser with output power of 0.1 W. Upconversion emission mechanism analysis indicated that the intensity ratio of red to green light highly depended on the synergistic effect of crystal structure, concentration quenching, and particle size, but were not sensitive to crystallinity as previously reported for NaL nF4（Ln=lanthanide.

Optical properties and Judd-Ofelt analysis of Nd2O3 nanocrystals embedded in polymethyl methacrylate

PMMA matrices were doped with nano-crystalline neodymium oxides synthesized by thermal decomposition process. X-ray diffraction and high-resolution transmission electron microscopy measurements were carried out to investigate the structure, phase, and the morphology of the Nd_2O_3 nanocrystals and those embedded in the PMMA matrix. The average grain sizes were estimated 35 ± 6 nm and 46 ± 4 nm for non-annealed and annealed Nd_2O_3 particles, respectively. The grain size distributions（GSD） were calculated from the diffraction peaks of the annealed and non-annealed Nd_2O_3 powders and doped PMMA samples. The mass density, refractive index. UV-Visible absorption spectra were measured and the data were analyzed using the Judd-Ofelt approach to determine the oscillator strengths, the spontaneous emission probabilities and the branching ratios as a function of the nano-crystalline Nd_2O_3 content in the range of 0.1 wt.%-20 wt.% of MMA. Luminescence spectra upon 808 nm diode laser excitation were carried out in the wavelength range of 850-1550 nm at room temperature. The photoluminescence study has shown that the reasonably sharp emission peaks were observed upon heat treatment at 800 ℃ for 24 h for all concentrations of Nd_2O_3 nanopowders in PMMA. The infrared laser transition of Nd^（3＋） ions at about 1.06 μm due to the ~4F_（3/2）→~4I_（11/2） transition was analyzed and discussed in Nd_2O_3 system for their possible applications in the photonic technology.