Yi Xia,Jie Shi,Qian Sun,Dan Wang,Xiao-Fei Zeng,Jie-Xin Wang,Jian-Feng Chen
Colloidal nanocrystals can offer exquisite control of physical and chemical properties for technological applications by tuning their sizes, shapes and crystal forms. Herein, a convenient phase-transfer route was presented to controllably prepare transparent dispersions of monodispersed ZrO 2 nanocrystals in an aqueous-organic two-phase medium. By adjusting the surfactants, solvents and basicity, the controllability of crystal forms from monoclinic to tetragonal phases, the particle length from 5 to 20 nm, and the different shapes including spindle, cobblestone, sphere, branch, rod and cube can be achieved. The as-prepared ZrO 2 nanocrystals can be readily dispersed in nonpolar solvents, thereby forming the ultra-highly concentrated (60 wt%), highly stable (>18 months) and highly transparent nanodispersions. Density functional theory (DFT) calculations were further used to elucidate the root causes of underpinning growth mechanisms. This work not merely enriches the methodology of controllable fabrication of monodispersed sub-10 nm ZrO 2 nanocrystals, but also enables a platform to synthesize rare-earth-doped nanophosphors using ZrO 2 as the host matrix. The fluorescent ZrO 2 :Yb 3+ /Er 3+ nanocrystals, which can be easily monodispersed in organic solvents, were also prepared with visible luminescene properties under near-infrared irradiation.
Nowadays, there is enthusiastic effort to develop luminescent thermometers used for remote and high-sensitivity temperature readout over a wide sensing range. Herein, Pr3+ and Gd3+ co-doped ZrO2 nanocrystals are designed, prepared and investigated by XRD, Raman spectroscopy, XPS, TEM, EDS, DRS, PLE and PL spectroscopy. Upon 275 nm irradiation, the PL spectrum of ZrO2:Pr3+,Gd3+ is found to be composed of a narrow emission peak at 314 nm (Gd3+ 6P7/2–8S7/2), a broad defect-related emission band at 400 nm, and several emission peaks in the wavelength region of 585–700 nm (Pr3+ 1D2–3H4, 3P0–3H6, and 3P0–3F2), which exhibit different thermal responses owing to the effects of the various non-radiative relaxation processes and trap energy levels. Accordingly, the luminescence intensity ratio (LIR) between the Pr3+ 1D2–3H4 and Gd3+ 6P7/2–8S7/2 transitions demonstrates excellent relative sensing sensitivity values ((2.32 ± 0.01)% K−1–(8.32 ± 0.05)% K−1) and low temperature uncertainties (0.08 K–0.28 K) over a wide temperature sensing range of 303 K to 573 K, which are remarkably better than those of many other luminescence thermometers. What is discussed in the present study may be conducive to broadening the research region of RE3+ doped luminescence thermometric phosphors, especially for materials with rich 4f–4f transition lines and defect-related luminescence.
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