Fluorescent nanothermometers for remote temperature measurement at the micro/nanoscale have stimulated growing efforts in developing efficient temperature-responsive materials and detection procedures. However, the efficient collection and transmission of optical signals have been a tremendous challenge for practical applications of these nanothermometers. Herein, we design an all-fiberized thermometry based on a fiber-coupled microsphere cavity coated with thermo-sensitive NaYF4:20%Yb3+,2%Er3+@NaYF4 nanocrystals (NCs), allowing for spatial temperature sensing with resolution down to the few-micrometer scale. In our design, the microsphere efficiently excites the NCs and collects their upconversion emissions, and the use of a fiber splitter coupled with the microsphere allows for lossless routing of excitation and emitted light. We demonstrate the use of this all-fiber temperature sensor in diverse environments, especially in strongly acidic and alkaline conditions. Leveraging the high flexibility of commercial silica fiber, this all-fiber temperature sensor was employed for stable fixed-point real-time temperature measurement and multipurpose temperature recording/mapping in opaque environments, microscale areas, various solutions, and complicated bent structures. Thus, the demonstrated design could have strong implications for the practical use of nanothermometers in various possible scenarios, especially monitoring temperatures in diverse physiological settings.
High-power lasers operating at the E- and S-bands that overlaps with the strong absorption band of water molecules have been exploited for applications such as medical diagnoses, laser therapy and lipolysis. This type of lasers can be realized with a MOPA (master oscillator power amplifier) configuration, consisting of a seed laser and a fiber amplifier, which allows one to achieve easily boosting the output power. However, the efficient fiber amplifiers operating in the E- and Sbands using most rare-earth-doped silica fibers is inaccessible. In contrary, the optical fibers doped with bismuth (Bi) capable of providing broadband amplification from 1100 to 1800 nm can be utilized to build a desired fiber amplifier. In this work, we demonstrated the output characteristics of developed amplifiers based on a Bi-doped 5GeO2 − 95SiO2 fiber (BGSF) drawn from a preform fabricated by the modified chemical vapour deposition (MCVD) technique. The corepumped fiber amplifiers are characterized by a small-signal gain of >20 dB at a wavelength of ~1440 to 1450 nm and the noise figure of ~4.5 to 6 dB. In addition, the fiber amplifier was employed to amplify a signal from a tunable continuous wave laser from 1390 to 1510 nm. This work presents the significance of Bi-doped fibers to build a fiber amplifier across E- and S-bands which could be attractive for medical diagnoses and laser therapy applications.
Lead halide perovskite materials exhibit excellent scintillation performance, which, however, suffer from serious stability and toxicity problems. In contrast, the heavy metal-free anti-perovskite materials [ MX4 ] XA3 (A = alkali metal; M = transition metal; X = Cl, Br, I), a class of electron-inverted perovskite derivatives, exhibit robust structural and photophysical stability. Here, we design and prepare a lead-free [ MnBr4 ] BrCs3 anti-perovskite nanocrystal (NC)-embedded glass for efficient X-ray-excited luminescence with high-resolution X-ray imaging with a spatial resolution of 19.1 lp mm − 1. Due to the unique crystal structure and the protection of the glass matrix, the Cs3MnBr5 NC-embedded glass exhibits excellent X-ray irradiation stability, thermal stability, and water resistance. These merits enable the demonstration of real-time and durable X-ray radiography based on the developed glassy composite. This work could stimulate the research and development of novel metal halide anti-perovskite materials and open a new path for future development in the field of high-resolution and ultrastable X-ray imaging.
Luminescent materials often suffer from thermal quenching (TQ), limiting the continuation of their applications under high temperatures up to 473 K. The formation of defect levels could suppress TQ, but rational synthesis and deep understanding of multiple defects-regulated luminescent materials working in such a wide temperature range still remain challenging. Here, we prepare a negative thermal quenching (NTQ) phosphor LiTaO3 : Tb3 + by introducing gradient defects VTa5−, TbLi2+, and ( VTaTbLi)3 − as identified by advanced experimental and theoretical studies. Its photoluminescence significantly becomes intense with rising temperatures and then slowly increases at 373 to 473 K. The mechanism studies reveal that gradient defects with varied trapping depths could act as energy buffer layers to effectively capture the carriers. Under thermal disturbance, the stored carriers could successively migrate to the activators in consecutive and wide temperature zones, compensating for TQ to enhance luminescence emission. This study initiates the synthesis of multi-defect NTQ phosphors for temperature-dependent applications.
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