Non-contact thermometry operating at the sub-micrometer level based on self-referencing upconversion (UC) micro-nanomaterial is an attractive pursuit for optical thermometers. Here, a novel accordion-like Y 2 O 3 :Er 3+ nanothermometer with green/red UC luminescence is obtained from the solvent-free grinding and the following temperature-programmed calcination of the Er 3+ -doped Y-containing metal-organic framework (MOF) precursor. Upon 980 nm laser irradiation, the as-prepared Y 2 O 3 :Er 3+ exhibits dual-emitting green and red emissions originating from Er 3+ ions with a two-photon UC process, and the intensities are strongly dependent on temperature. The optical thermometry behaviours of Y 2 O 3 :Er 3+ nanothermometer using the fluorescence intensity ratio (FIR) technique are studied in the temperature range of 298–393 K within the physiological temperature, in which the thermally coupled levels of two green emissions and another pair of coupled levels with red and green emissions are comparatively investigated. A relative large calculated energy gap Δ E (951 cm −1 ) for the thermally couple levels of 2 H 11/2 and 4 S 3/2 and a maximum absolute sensitivity ( S a ) of 0.0027 K −1 at 393 K are determined, respectively. This novel accordion-like Y 2 O 3 :Er 3+ nanothermometer exhibits excellent optical sensing stability and high temperature resolution, demonstrating its great potential as reliable and promising optical thermometers.
The co-doping effect of Zr 4+ ions on upconversion (UC) luminescent properties in visible region of Y 2 O 3 : Er 3+ and Y 2 O 3 : Er 3+ , Yb 3+ sub-microcrystals prepared by urea precipitation method has been investigated under 980 nm excitation. Compared with the original Y 2 O 3 : Er 3+ and Y 2 O 3 : Er 3+ , Yb 3+ sub-microcrystals, the UC luminescence of sub-microcrystals with similar size was enhanced after Zr 4+ ions co-doping. The UC luminescent properties have been discussed in detail via luminescence spectra, decay curve analysis and a suitable energy level diagram. The enhancement mechanism of UC luminescence in the two series of Zr 4+ ions doped sub-microcrystals was attributed to the complex crystal field around Er 3+ ions caused by Zr 4+ ions co-doping. After Zr 4+ ions substituted Y 3+ ions and entered the crystal lattice, the charge mismatch and lattice distortion made the crystal field more complex. This research contributes to the understanding of UC luminescent properties of lanthanide (Ln 3+ ) ions doped UC materials and their technological applications in fields such as bioimaging, drug delivery, and optical temperature sensors.
Monodisperse Y 2 O 3 : Er 3+ /Yb 3+ /Tm 3+ nanoparticles with various dopant concentrations have been synthesized successfully by a homogeneous precipitation method. Their phase structures and surface morphologies have been characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The diversities of upconversion luminescence spectra and CIE coordinates of prepared samples are investigated in detail at room temperature under 980 nm excitation. Through adjusting the concentrations of Yb 3+ , Tm 3+ and Er 3+ ions, three upconversion emission bands in red, green and blue region could be tunable to achieve the color of interest and near white light emission can be obtained in the tri-doped Y 2 O 3 nanoparticles for a variety of application.
Highly efficient saturation up-conversion (UC) luminescent Y2O3:Er3+ microspheres have been successfully prepared via a hydrothermal-homogeneous precipitation method. Bright visible luminescence can be clearly seen with a 1.55 μm laser diode excitation power as low as ∼0.03 W cm−2. The up-conversion (UC) emission spectra indicate that the strongest red emission with a peak situated at ∼660 nm originated from the 4I9/2 → 4I15/2 transition of Er3+. The peaks situated at ∼520 and 550 nm can be assigned to the transition from 2H11/2/4S3/2 state to the ground state of Er3+. The high efficient saturation up-conversion emission is related to the highly crystalline structure. These results indicate a new way to enhance UC radiation in rare-earth ion-doped materials prepared using a hydrothermal-homogeneous precipitation method.
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