Influence of Gd3+ doping concentration on the properties of Na(Y,Gd)F4:Yb3+, Tm3+ upconverting nanoparticles and their long-term aging behavior

Abstract

We present a systematic study on the properties of Na(Y,Gd)F4-based upconverting nanoparticles (UCNP) doped with 18% Yb3+, 2% Tm3+, and the influence of Gd3+ (10–50 mol% Gd3+). UCNP were synthesized via the solvothermal method and had a range of diameters within 13 and 50 nm. Structural and photophysical changes were monitored for the UCNP samples after a 24-month incubation period in dry phase and further redispersion. Structural characterization was performed by means of X-ray diffraction (XRD), transmission electron microscopy (TEM) as well as dynamic light scattering (DLS), and the upconversion luminescence (UCL) studies were executed at various temperatures (from 4 to 295 K) using time-resolved and steady-state spectroscopy. An increase in the hexagonal lattice phase with the increase of Gd3+ content was found, although the cubic phase was prevalent in most samples. The Tm3+-luminescence intensity as well as the Tm3+-luminescence decay times peaked at the Gd3+ concentration of 30 mol%. Although the general upconverting luminescence properties of the nanoparticles were preserved, the 24-month incubation period lead to irreversible agglomeration of the UCNP and changes in luminescence band ratios and lifetimes.

Upconversion Emission and Dual-Mode Sensing Characteristics of NaYF4:Yb3+/Er3+ Microcrystals at High and Ultralow Temperatures

“…However, research on the temperature characteristics of red emission peaks in Yb 3+ /Er 3+ dual-doped crystal systems at low temperatures remains scarce [21,22]. To fill this gap, in the present work, our study encompasses a wide range of temperatures, specifically from the high-temperature range of 353-453 K to the low/ultralow temperature range of 55-230 K. In this extended range, we investigated the correlation between temperature and the frequencyand time-domain upconversion luminescence spectra for a dual-doped NaYF 4 system.…”

New Strategy for Improving the Sensitivity of Optical Nanothermometers Based on NaYF4:Yb3+/Er3+/Nd3+/Gd3+ Nanorods

“…The nanomaterials prepared with oleic acid and ethanol appear phase separation. Since the hexagonal phase NaYF 4 doped with RE ions has higher UC efficiency than the tetragonal phase NaYF 4 , − Gd 3+ is added to facilitate the transformation of NaYF 4 from the tetragonal phase to hexagonal phase. − When the concentration of Gd 3+ reaches 40 mmol%, a pure hexagonal phase structure is formed. , The luminescence intensity of Er 3+ decreases, while that of the Nd 3+ increases with temperature. Meanwhile, the 4 S 3/2 → 4 I 15/2 (Er 3+ ) transition decreases the most, and the 4 F 3/2 → 4 I 9/2 (Nd 3+ ) transition increases the most.…”