@article{152dde1990764e33a3f4b39a8cbbdb71,
title = "An investigation of the thermal sensitivity and stability of the β-NaYF4:Yb,Er upconversion nanophosphors",
abstract = "The upconversion luminescence (UCL) of the hexagonal (β)-phase NaYF4:Yb,Er nanophosphors as a function of temperature (300-450 K) was examined under 978 nm light excitation. The thermal sensitivity was evaluated based on the UCL intensity ratio between 2H 11/2-4I15/2 and 4S 3/2-4I15/2 transitions (RHS). Excitation power, particle sizes (37, 65, and 140 nm), ion doping concentrations, and with and without silica coating were studied. It was found that RHS is only dependent on temperature at the low excitation power, and has no direct relation with the particle size and surface effects. Silica coating was found to enhance the thermal stability significantly without altering the thermal sensitivity.",
author = "Jingning Shan and Wenjun Kong and Robert Wei and Nan Yao and Yiguang Ju",
note = "Funding Information: This work was supported by the National Science Foundation MRSEC Program through the Princeton Center for Complex Materials (Grant No. DMR-0819860) and AFSOR. We thank Professor Austin for commenting the work. Scheme 1. Energy-level diagram of Yb 3 + / Er 3 + -codoped UCNPs and UC processes under 978 nm excitation. Dotted and twisting arrows indicate nonradiative relaxation. Scheme 2. Heating system for measuring temperature-dependent UCL. FIG. 1. TEM images of the OA-TOP coated UCNPs [(a)–(c)] and silica coated UCNPs (d). FIG. 2. (a) UCL intensity and (b) corresponding R HS ratios vs excitation power of three UCNPs in different sizes. FIG. 3. (a) UCL spectra of the 37 nm UCNPs collected at different temperature and (b) Ln ( R HS ) vs intensity vs temperature (1/T). FIG. 4. R HS ratios vs heating temperature. Changing of Yb% (a) and Er% (b). FIG. 5. Thermal stability and R HS comparison between hydrophobically ligated and SiO 2 coated UCNPs. ",
year = "2010",
doi = "10.1063/1.3298905",
language = "English (US)",
volume = "107",
journal = "Journal of Applied Physics",
issn = "0021-8979",
publisher = "American Institute of Physics Publising LLC",
number = "5",
}