Hong Wang,Boyuan Zhang,Jiaqi Zhao,Mingming Xing,Ying Tian,Yao Fu
Thermally enhanced upconversion luminescence (UCL) materials have obvious advantages in the various fields of optical temperature sensing, anti-counterfeiting, and display. Here, we report a novel thermal enhancement UCL phosphor of Ca 2 Gd 8 Si 6 O 26 :Yb 3+ ,Er 3+ (CGSO:Yb 3+ ,Er 3+ ). Benefiting from the thermally enhanced phonon-assisted effect, anti-Stokes sideband excitation of Yb 3+ , energy transfer from Yb 3+ to Er 3+ , and thermal population from selective energy levels of Er 3+ are promoted with increasing temperature, which contributes to the thermal enhancement UCL of 4 F 7/2 → 4 I 15/2 , 2 H 11/2 → 4 I 15/2 , and 4 I 9/2 → 4 I 15/2 radiation transitions of Er 3+ ions. In addition, the rarely thermal enhancement of near infrared emission at 870 nm observed may be attributed to the Yb 3+ -induced effect. Furthermore, thermal quenching occurs for 4 S 3/2 → 4 I 15/2 and 4 F 9/2 → 4 I 15/2 transitions due to thermally enhanced multiphonon relaxation and thermal population. The combination of thermal enhancement and thermal quenching effect, the ratiometric optical thermometer is constructed in the wide temperature range 303–723 K by leveraging of the thermally coupled energy levels 2 H 11/2 and 4 S 3/2 of Er 3+ . This optical thermometer shows excellent temperature measurement performances with a maximum relative sensitivity of 1.1 × 10 −2 K −1 at 303 K and high repeatability of 99 %. These findings indicate that CGSO:Yb 3+ ,Er 3+ phosphors with thermally enhanced UCL have great potential application for temperature sensing.
This paper reports a new type of PbTiO 3 :Yb 3+ /Er 3+ (PTO:Yb 3+ /Er 3+ ) phosphor synthesized by sol-gel method. Under 980 nm excitation, PTO:Yb 3+ /Er 3+ phosphors exhibited green emission bands centered at 524/549 nm ( 2 H 11/2 / 4 S 3/2 → 4 I 15/2 ) and red emissions 661 nm ( 4 F 9/2 → 4 I 15/2 ). Concentration-dependent upconversion (UC) luminescence spectra showed that the optimal luminescence was observed at 6at%Yb 3+ /2at%Er 3+ -codoping concentration. A possible UC mechanism for PTO:Yb 3+ /Er 3+ phosphor is discussed by the pump power-dependent UC luminescence spectra. The temperature-dependence (298–548 K) of the fluorescence intensity ratios (FIR) for the two green UC emission bands peaked at 524 and 549 nm was studied under a 980 nm laser excitation and the maximum relative sensitivity was approximately 12.25 × 10 −3 K −1 at 298 K. The thermal quenching activation energy of near-infrared (NIR) luminescence was studied. It can be found that the phosphor has a small thermal quenching possibility and excellent thermal stability. The value of repeatability (R) more than 98% has obtained via four cycles of cooling and heating, which prove that the phosphor has a good cycling stability. These results indicate that PTO:Yb 3+ /Er 3+ phosphor is a promising candidate for optical temperature sensors with high sensitivity and good repeatability.
Zhurong Mo,Yanping Huo,Haoyi Wu,Brij Mohan,Hongli Wen,Li Luo,Deshmukh Abdul Hakeem
We report the synthesis and the effect of synthesis temperature on the crystal structure and dual mode (DC/UC) luminescence properties of the NASE-1000–1300. Two different polymorphs, i.e., nepheline and carnegieite of the NASE have been prepared just by changing the annealing temperature. Multi wavelength excitation can be used to obtain different emissions in visible and NIR regions. Under 380 and 980 nm excitation, the NASE-1000–1300 produces 1535 nm NIR emission, whereas green and red visible emissions are observed with 980 and 808 nm laser excitations. Under 980 nm laser excitation, the synthesis temperature dependent nepheline and carnegieite polymorphs emit intense red and green emission, respectively. Two-photon process is responsible for the green and red UC emissions of the NASE-1300. The NASE-1000-1300 produces intense red emission under 808 nm laser excitation. We believe that the NASE-1000–1300 could be a promising candidate for the photonic as well as biological applications.
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