We report that non-contact self-referencing temperature sensors can be realized with the use of core-shell nanostructures. These lanthanide-based nanothermometers (NaGdF4:Yb(3+)/Tm(3+)@Tb(3+)/Eu(3+)) exhibit higher sensitivity in a wide range from 125 to 300 K based on two emissions of Tb(3+) at 545 nm and Eu(3+) at 615 nm under near-infrared laser excitation.
BaCuSi 4 O 10 (Han blue), CaCuSi 4 O 10 (Egyptian blue), and SrCuSi 4 O 10 are pigments found in many ancient artifacts all over the world. Behind their brilliant color, we demonstrate here that these ancient pigments are strong candidates for photonic materials due to their bright Stokes and anti-Stokes emissions. These pigments give near-infrared emissions (NIR) from Cu 2+ centered at around 930 nm under excitation of 440-800 nm light. This NIR emission can also be produced by pumping using a NIR laser diode. With the rise of pumping density, the emission bandwidth increases notably and stretches to the visible region, giving rise to bright, and broadband photon upconversion (UC). This photon UC process is interpreted in terms of laser-driven blackbody radiation from the ancient pigments.
Core–shell NaYF4:Yb3+, Tm3+@NaYF4:Yb3+, Nd3+ nanosystem for temperature sensing with a minimized heating effect, which demonstrates a high sensitivity of up to 1.55% K−1 at a temperature range between 313 and 553 K.
The effect of heat-treatment on the near-infrared (NIR) luminescence properties was studied in Bi-doped borate glasses. The luminescence intensity generally decreases with the increase of temperature, and the thermal stability can be improved by nearly 4.5 times with addition of 5 mol% La2O3. Collaborative studies by using steady photoluminescence (PL) and photoluminescence excitation (PLE) spectra, luminescence decay curve, differential thermal analysis (DTA), Raman spectra and X-ray diffraction (XRD) indicate that the luminescence decrement is associated with the agglomeration of Bi active centers during heat-treatment. The improvement of the thermal stability of NIR luminescence with the addition of La2O3 is benefited from the enhancement of structure rigidity due to the strong cationic field strength of La3+. The results not only provide valuable guidance for suppressing performance degradation of Bi-doped glass during fiber drawing process, but also present an effective way to control the luminescence properties of main group elements in glasses from the perspective of glass structure.
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