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In this paper, BaY2O4:Yb3+/Er3+, a high efficient red upconversion (UC) material, is first utilized as an optical thermometer in the biological window, accomplished through the fluorescence intensity ratio (FIR) of thermally coupled Stark sublevels of 4F9/2 (FIR(654/663)). The maximum absolute sensitivity of FIR(654/663)) is 0.19% K-1 at 298 K, which is much higher than most previous reports about FIR-based temperature sensors located in the biological windows. More importantly, the groove of FIR(654/663) for thermometry is nicely located in the physiological temperature range, indicating its potential thermometry application value in biomedicine. Furthermore, a simply ex vivo experiment is implemented to evaluate the penetration depth of the red emission in biological tissues, revealing that a detection depth of 6 mm can be achieved without any effect on the FIR values of I654 to I663. Beyond that, the temperature sensing behaviors of the thermally coupled levels 2H11/2 and 4S3/2 (FIR(523/550)) are also investigated in detail. In the studied temperature range, the absolute sensitivity of FIR(523/550) monotonously increases with the rising temperature and reaches its maximum value 0.31% K-1 at 573 K. All the results imply that BaY2O4:Yb3+/Er3+ is a promising candidate for deep-tissue optical thermometry with high sensitivity.

The optical thermometry properties of LuVO4:Yb3+/Er3+@SiO2 nanoparticles (NPs) are studied in detail. In order to avoid the overheating effect for biological tissue caused by 980 nm radiation, 915 ...

In this paper, BaY

Six complexes {(3-bdppmapy)(AuCl)2}n (1–6; 3-bdppmapy = N,N′-bis(diphenylphosphanylmethyl)-3-aminopyridine and tht = tetrahydrothiophene) were simultaneously formed by the reaction of Au(tht)Cl and...

The red upconversion (UC) emission of Eu3+ ions in Lu2O3: Yb3+/Eu3+ powders was successfully enhanced by tridoping Ho3+ ions in the matrix, which is due to the bridging function of Ho3+ ions. The experiment data manifest that, in Yb3+/Eu3+/Ho3+ tridoped system, the Ho3+ ions are first populated to the green emitting level 5F4/5S2 through the energy transfer (ET) processes from the excited Yb3+ ions. Subsequently, the Ho3+ ions at 5F4/5S2 level can transfer their energy to the Eu3+ ions at the ground state, resulting in the population of Eu3+5D0 level. With the assistance of the bridging function of Ho3+ ion, this ET process is more efficient than the cooperative sensitization process between Yb3+ ion and Eu3+ ion. Compared with Lu2O3: 5 mol % Yb3+/1 mol % Eu3+, the UC intensity of Eu3+5D0→7F2 transition in Lu2O3: 5 mol % Yb3+/1 mol % Eu3+/0.5 mol % Ho3+ is increased by a factor of 8.

The monochromaticity improvement of green upconversion (UC) in Lu2O3:Yb3+/Ho3+ powders has been successfully realized by tridoping Eu3+. The integral area ratio of green emission to red emission of Ho3+ increases 4.3 times with increasing Eu3+ doping concentration from 0 to 20 mol %. The energy transfer (ET) mechanism in the Yb3+/Ho3+/Eu3+ tridoping system has been investigated carefully by visible and near-infrared (NIR) emission spectra along with the decay curves, revealing the existence of ET from the Ho3+ 5F4/5S2 level tothe Eu3+ 5D0 level and ET from the Ho3+ 5I6 level to the Eu3+ 7F6 level. In addition, the population routes of the red-emitting Ho3+ 5F5 level in the Yb3+/Ho3+ codoped system under 980 nm wavelength excitation have also been explored. The ET process from the Yb3+ 2F5/2 level to the Ho3+ 5I7 level and the cross-relaxation process between two nearby Ho3+ ions in the 5F4/5S2 level and 5I7 level, respectively, have been demonstrated to be the dominant approaches for populating the Ho3+ 5...

A high-temperature solid-state method was used to synthesize the Ho3+- and Yb3+-codoped cubic Lu2O3 powders. The crystal structures of the as-prepared powders were characterized by X-ray diffraction. The energy-transfer (ET) phenomenon between Ho3+ ions and Yb3+ ions was verified by the steady-state spectra including visible and near-infrared (NIR) regions. Beyond that, the decay curves were also measured to certify the existence of the ET process. The downconversion phenomena appeared when the samples were excited by 446 nm wavelength corresponding to the transition of Ho3+: 5I8→5G6/5F1. On the basis of the analysis of the relationship between the initial transfer rate of Ho3+: 5F3 level and the Yb3+ doping concentration, it indicates that the ET from 5F3 state of Ho3+ ions to 2F5/2 state of Yb3+ ions is mainly through a two-step ET process, not the long-accepted cooperative ET process. In addition, a 62% ET efficiency can be achieved in Lu2O3: 1% Ho3+/30% Yb3+. Unlike the common situations in which the ...

The optical thermometry properties of LuVO

A series of lanthanide organic complexes, namely, [Ln2PDC3(H2O)3]H2O (Ln = Eu, Tb, EuxTb2–x, H2PDC: pyridine-3,5-dicarboxylic acid), were synthesized via hydrothermal method. Eu-PDC was characteriz...

The red upconversion (UC) emission of Eu

The monochromaticity improvement of green upconversion (UC) in Lu

A high-temperature solid-state method was used to synthesize the Ho