Luminescence Behavior of GdVO4: Tb Nanocrystals in Silica Glass-Ceramics

Glass ceramics with GdVO4: Tb nanocrystals impregnated in the highly transparent silica glass were prepared by the porous glass and sintering process and confirmed by XRD, Raman spectrum, and TEM. Spectral analysis shows that there are multifarious energy transfer processes in GdVO4: Tb nanocrystals, such as VO43− → Tb3+, Gd3+ → VO43−, Gd3+ → VO43− → Tb3+, and Gd3+ → Tb3+, and the main one is VO43− → Tb3+. In this process, 3T1,2 → 1A1 transition of VO43− transfers the energy to Tb3+ and generates 5D3 → 7F6,5,4,3,2 and 5D4 → 7F5 transitions of Tb3+. The energy transfer efficiency is 29.5%, and the excitation wavelength range of Tb3+ ions can be shifted from 230–260 nm to 280–365 nm. This shows that GdVO4 can effectively change the excitation wavelength of Tb3+, which is conducive to the application of Tb3+ ions excited by LED light sources.

High pressure induced local ordering and tunable luminescence of La2Hf2O7:Eu3+ nanoparticles

This work highlights the high-pressure induced site swapping and improved ordering of Eu³⁺ in La₂Hf₂O₇:Eu³⁺ nanocrystals which leads to red-orange-yellow tunable emission at low-moderate-high pressure regime and enhanced correlated color temperature.

Multifunctional Optical Sensors for Nanomanometry and Nanothermometry: High-Pressure and High-Temperature Upconversion Luminescence of Lanthanide-Doped Phosphates-LaPO4/YPO4:Yb3+-Tm3

Upconversion luminescence of nano-sized Yb³⁺ and Tm³⁺ codoped rare earth phosphates, that is, LaPO₄ and YPO₄, has been investigated under high-pressure (HP, up to ∼25 GPa) and high-temperature (293-773 K) conditions. The pressure-dependent luminescence properties of the nanocrystals, that is, energy red shift of the band centroids, changes of the band ratios, shortening of upconversion lifetimes, and so forth, make the studied nanomaterials suitable for optical pressure sensing in nanomanometry. Furthermore, thanks to the large energy difference (∼1800 cm^-1), the thermalized states of Tm³⁺ ions are spectrally well-separated, providing high-temperature resolution, required in optical nanothermometry. The temperature of the system containing such active nanomaterials can be determined on the basis of the thermally induced changes of the Tm³⁺ band ratio (³F_2,3 → ³H₆/³H₄ → ³H₆), observed in the emission spectra. The advantage of such upconverting optical sensors is the use of near-infrared light, which is highly penetrable for many materials. The investigated nanomanometers/nanothermometers have been successfully applied, as a proof-of-concept of a novel bimodal optical gauge, for the determination of the temperature of the heated system (473 K), which was simultaneously compressed under HP (1.5 and 5 GPa).

Luminescence property tuning of Yb3+-Er3+ doped oxysulfide using multiple-band co-excitation

Lanthanide ions have abundant excited-state channels which result in a radiation relaxation process generally accompanied by a non-radiation relaxation process. However, non-radiation relaxation processes will consume the activation energy and reduce the luminescence efficiency of the phosphor. Two lasers with an excitation energy which matched the ground state absorption and excited state absorption of ions were used to excite the phosphors to avoid the non-radiation relaxation process. This approach can achieve the purpose of populating specific states of the lanthanide ions, and furthermore effectively tunes the luminescence intensity and color output of the sample. Results show that the red emission intensity of the sample is significantly improved and this is caused by populating the ⁴F_9/2 level under simultaneous 1510 nm and 980 nm excitation. Then when the 1510 nm and 808 nm co-operate to excite the sample, the green emission obtained increased sharply because the ²H_11/2/⁴S_3/2 states were efficiently populated. As a proof-of-concept experiment, this new approach has potential in the applications of solar cells.

The emission intensity of the sample excited by dual-wavelength (980 and 1510 nm) is 3.2 times than the sum of UCL emission under the two single wavelength excitation.

Comparison of quenching mechanisms in Gd3Al5−xGaxO12:Ce3+ (x = 3 and 5) garnet phosphors by photocurrent excitation spectroscopy

In this work we investigate in detail the kinetics of luminescence quenching process in Gd₃(Al,Ga)₅O₁₂:Ce³⁺ garnets, using non-standard experimental techniques.