Synthesis and characterization of Gd2O3: Er3+, Yb3+doped with Mg2+, Li+ions-effect on the photoluminescence and biological applications

Enhancement of photoacoustic and upconversion emission in Mg2+/Zn2+ codoped Gd2O3: Er3+/Yb3+ phosphor using 980 nm excitation

In this work, Er³⁺/Yb³⁺ doped Gd₂O₃ phosphor samples were synthesized through a combustion method and then characterized through X-ray diffraction and FE-SEM techniques. The sample was studied for photoacoustic spectroscopy (PAS) and upconversion (UC) emission spectroscopy techniques using a frequency modulated 980 nm excitation source. A correlation between PA signal (produced due to non-radiative transitions) and UC emission intensity (produced due to radiative transition) is made in order to optimize the sample for both these properties. The phosphor was codoped with Mg²⁺ and Zn²⁺ ions to see enhancement in upconversion emission intensity and these ions have enhanced the upconversion emission. Studies show that the present phosphor is appropriate for producing strong upconversion emission intensity along with a strong photoacoustic signal which is beneficial for upconversion-imaging as well as photothermal therapy. The present sample has also shown its potential for detection of fingerprints.

Upconversion NaYF4:Yb3+/Er3+@silica-TPGS Bio-Nano Complexes: Synthesis, Characterization, and In Vitro Tests for Labeling Cancer Cells

Fluorescence imaging is an important technique used for early diagnosis and effective treatment of some incurable diseases including cancer. Herein, we report novel NaYF₄:Yb³⁺/Er³⁺@silica-TPGS bio-nano complexes for labeling cancer cells. The NaYF₄:Yb³⁺/Er³⁺ nanoparticles have been successfully synthesized via a hydrothermal route, further coated with a silica shell, and functionalized with d-α-tocopheryl polyethylene glycol 1000 succinate (TPGS). The experimental results indicate that NaYF₄:Yb³⁺/Er³⁺@silica-TPGS emits stronger upconversion luminescence than NaYF₄:Yb³⁺/Er³⁺ under an excitation of 980 nm. More significantly, the NaYF₄:Yb³⁺/Er³⁺@silica-TPGS bio-nano complexes could strongly label MCF-7 breast cancer cells for in vitro experiments detected by a fluorescence microscope. On the other hand, the complex could not typically probe healthy cells, which are HEK-293A human embryonic kidney cells, under the same experimental conditions. Because of their strong upconversion luminescence, good dispersibility, and biocompatibility, NaYF₄:Yb³⁺/Er³⁺@silica-TPGS bio-nano complexes can be a promising candidate/probe for biomedical labeling and diagnostics.

Fluorescence regulation derived from Eu3+in miscible-order fluoride-phosphate blocky phosphor

Miscible-order fluoride-phosphate blocky phosphor (FBP), composed with ordered-phase of NaYF₄crystals and unordered phase of tin-fluorophosphate glass, is prepared by a two-step process and luminescent properties of FBPs embedded with different particle sizes of NaYF₄crystals are presented. High-frequency fluorescence from higher metastable⁵D_J(J = 1, 2 and 3) energy levels are effectively released in Eu³⁺doped fluoride crystals. Taking the blue emission of Sn²⁺as the framework, multi-peak emissions from metastable energy levels are controlled to adjust the color coordinates of the FBP to the white-light region, which the color rendering index (CRI) reaches 89. Tunable color FBP with high CRI retains splendid luminescence property of fluoride, providing a potential candidate for the development of white LED.