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Glass ceramics (GCs) containing PbS quantum dots (QDs) are prepared for temperature sensing. Broadband emissions are detected in the GCs when PbS QDs are precipitated from the glasses, and emissions centers are modulated from 1250 nm to 1960 nm via heat treatments. The emission centers of GCs exhibit blue-shifts when environment temperatures increase from room temperature to 210 °C. Importantly, the shift values of emission centers increase linearly with the test temperature, which is beneficial for applications in temperature sensing. A temperature sensor based on PbS QDs GC is heat-treated at 500 °C for 10 h, possesses the highest sensitivity of 0.378 nm/°C, and exhibits excellent stability and repeatability at high temperatures (up to 210 °C). Moreover, GC fibers are fabricated by using the GCs as the fiber core. The sensitivity of the temperature-sensing sensor of the GC fibers is also demonstrated and the sensitivity is as high as 0.558 nm/°C. The designed PbS QDs GCs provide a significant materials base for the manufacturing of fluorescent temperature sensors and the GC fibers offer significant opportunities for temperature detection in complex, integrated and compact devices.
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Oxyfluoride transparent glass-ceramics (GC) are widely used as the matrix for rare-earth (RE) ions due to their unique properties such as low phonon energy, high transmittance, and high solubility for RE ions. Tb3+ doped oxyfluoride glasses exhibit a large absorption cross section for ultraviolet (UV) excitation, high stability, high photoluminescence quantum efficiency, and sensitive spectral conversion characteristics, making them promising candidate materials for use as the spectral converter in UV photodetectors. Herein, a Tb3+ doped oxyfluoride GC is developed by using the melt-quenching method, and the microstructure and optical properties of the GC sample are carefully investigated. By combining with a Si-based photo-resistor,a solar-blind UV detector is fabricated, which exhibits a significant photoelectric response with a broad detection range from 188 to 400 nm. The results indicate that the designed UV photodetector is of great significance for the development of solar-blind UV detectors.
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In this work, a glass ceramics (GC) containing KTb2F7 nanocrystals was fabricated by controlled crystallization of an fluorosilicate glass via heat-treatment. The microstructure, luminescence, and photoelectric properties of the GCs are systematically studied by X-ray diffraction, transmission electron microscopy, spectral analysis, and current-voltage (I-V) curves. The results show that the GC containing KTb2F7 nanocrystals exhibit intense visible emission due to the 4f transition of Tb3+: 5Di (i = 3, 4) â 7Fj (j = 0-6) upon excitation of ultraviolet (UV) light. In addition, a UV detector device based on the GC was fabricated, which has a large dynamic linear response range, fast response speed and high sensitivity. This study not only provides a new material for UV detector that can simplify the process of UV detection, but also highlight a new strategy for UV detection.
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Laser-driven liquid crystal displays (LCDs) comprising metal halide perovskites (MHPs) as the blue-to-green/red color converters are at the forefront of ongoing intense research on the development and improvement of display devices. However, the inferior high photoluminescence quantum yield (PLQY) of MHPs under the excitation of high-power blue light and photoluminescence deterioration at high temperatures remain major concerns. Herein, we design a kind of octylamine-modified MHP via binding energy engineering, and the synthesized materials show PLQY of 97.6% under the excitation of a blue laser at 450 nm. Meanwhile, this design endows a structural self-healing ability to achieve a high PLQY and luminescence stability under high temperature (90 °C) and high flux excitation (386 mW cm-2). The blue light-excitable MHPs with a near unity PLQY, strong stability, and low PLQY deterioration are further encapsulated into a laser-driven LCD device. This prototype demonstrates excellent color gamut (132% NTSC, 98% Rec. 2020), illuminance intensity (>10 000 lux), and energy consumption (47.5% of commercial consumption), and hence is expected to be beneficial for the reduction of energy consumption in backlight display devices, particularly in large-screen outdoor displays.
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A fluorosilicate (FS) nano-crystallized glass ceramic (NGC) is one of the most commonly used gain materials for applications in optical devices due to its excellent thermal stability as well as high-efficiency luminescence. However, FS glass can hardly be used to prepare NGC fibers due to its high preparation temperature. Here, a series of low-temperature fluoro-borosilicate (FBS) glasses were designed for the fabrication of active NGC fibers. By modulating B2O3, the preparation temperature of FBS glass was reduced to 1050 °C, and the crystallization in FBS NGCs was more controllable than in FS NGC. The crystallization of the impure phase was inhibited, and single-phase rare earth (RE)-fluoride nanocrystals were controllably precipitated in the FBS NGCs. The 40Si-20B FBS NGC not only exhibited a higher optical transmittance, but the luminescence efficiency was also much higher than traditional FS NGCs. More importantly, NGC fibers were successfully fabricated by using the designed FBS glass as core glass. Nanocrystals were controllably precipitated and greatly enhanced, and upconversion luminescence was observed in NGC fibers. The designed FBS NGCs provided high-quality optical gain materials and offered opportunities for fabricating a wide range of NGC fibers for multiple future applications, including fiber lasers and sensors.
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Fiber-based inorganic thermoelectric (TE) devices, owing to the small size, light-weight, flexibility, and high TE performance, are promising for applications in flexible thermoelectrics. Unfortunately, current inorganic TE fibers are strictly constrained by limited mechanical freedom because of the undesirable tensile strain, typically limited to a value of 1.5%, posing a strong obstacle for further application in large-scale wearable systems. Here, a superflexible Ag2 Te0.6 S0.4 inorganic TE fiber is demonstrated that provides a record tensile strain of 21.2%, such that it enables various complex deformations. Importantly, the TE performance of the fiber shows high stability after ≈1000 cycles of bending and releasing processes with a small bending radius of 5 mm. This allows for the integration of the inorganic TE fiber into 3D wearable fabric, yielding a normalized power density of 0.4 µW m-1 K-2 under the temperature difference of 20 K, which is approaching the high-performance Bi2 Te3 -based inorganic TE fabric and is nearly two orders of magnitude higher than the organic TE fabrics. These results highlight that the inorganic TE fiber with both superior shape-conformable ability and high TE performance may find potential applications in wearable electronics.
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Efficient white upconversion (UC) luminescence is obtained in Yb3+/Eu3+ doubly-doped optical glass ceramic (GC) for the first time. KYb3F10 nanocrystals are controllably precipitated from the amorphous networks via the inducing of Yb3+. Yb3+ ions are spontaneously confined within the compact fluoride crystal structures to produce efficient blue UC emissions of Yb3+-Yb3+ pairs. Eu3+ ions are easily incorporated into the KYb3F10 crystal lattices. Owing to the extremely short interionic distance in the crystal structures, intense green UC emissions apart from the red emissions of Eu3+ are observed, which are not obtained by the traditional Yb3+/Eu3+ doubly-doped GCs. As a result, white UC emissions are synthesized based on the three-primary-color principle and the emission intensities of GCs are dramatically enhanced as compared to glass. The designed GCs provide novel optical gain materials for the promising applications in three-dimensional display, solid-state lighting and tunable fiber lasers.
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Transparent glass-ceramic composites embedded with Ln-fluoride nanocrystals are prepared in this work to enhance the upconversion luminescence of Tm3+. The crystalline phases, microstructures, and photoluminescence properties of samples are carefully investigated. KYb3F10 nanocrystals are proved to controllably precipitate in the glass-ceramics via the inducing of Yb3+ when the doping concentration varies from 0.5 to 1.5 mol%. Pure near-infrared upconversion emissions are observed and the emission intensities are enhanced in the glass-ceramics as compared to in the precursor glass due to the incorporation of Tm3+ into the KYb3F10 crystal structures via substitutions for Yb3+. Furthermore, KYb2F7 crystals are also nano-crystallized in the glass-ceramics when the Yb3+ concentration exceeds 2.0 mol%. The upconversion emission intensity of Tm3+ is further enhanced by seven times as Tm3+ enters the lattice sites of pure KYb2F7 nanocrystals. The designed glass ceramics provide efficient gain materials for optical applications in the biological transmission window. Moreover, the controllable nano-crystallization strategy induced by Yb3+ opens a new way for engineering a wide range of functional nanomaterials with effective incorporation of Ln3+ ions into fluoride crystal structures.
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A transparent glass ceramic (GC) is designed via the controllable precipitation of KYb3F10 nanocrystals. It is shown that the crystallization in GC deeply depends on the doping of Yb3+. Yb3+ ions are spontaneously distributed in the fluoride crystal environments without the ionic substitution process of traditional GC. As a result, high-efficiency upconversion (UC) luminescence is achieved in GC. The UC quantum yield value of the Yb3+-Er3+-codoped GC is as high as 1.44±0.02%, which is more than 20 times higher than the traditional GC containing NaYF4 crystals. The designed GC offers opportunities for the promising development of active optical devices, and the crystallization strategy of this GC provides a powerful solution to conquer the bottleneck in luminescence efficiency of the traditional GCs.
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Amorphous glass is a significant luminescence matrix for various applications, such as fiber lasers, lighting and 3D data storage. However, the efficiency of luminescence, especially upconversion (UC) luminescence, in glass is usually low. The UC emission of transition metal ions is hardly observed in amorphous glass. Here, a strategy is proposed to modulate the distribution of activators based on phase-separated glass for achieving high-efficiency UC luminescence. It is demonstrated that high-efficiency UC luminescence of Yb3+-Yb3+ pairs and Mn2+-Yb3+ dimers are observed in the amorphous glass due to the excellent confinement of phase-separated networks to activators. The UC emission intensity of the phase-separated glass is even higher than that of all-fluoride glass. Furthermore, KZnF3 and KYb3F10 crystals are controllably precipitated from the glass matrix regulated by phase-separated networks. This perfectly confines activators in crystal environments, greatly enhances the UC luminescence and controllably tailors the luminescence color. This glass possesses large potential for promising application in tunable fiber lasers, multicolor displays and multiphoton excitation-based 3D optical data storage. Most importantly, the modulation strategy based on phase-separated networks paves a new way for manufacturing a wide range of optical gain materials featuring efficient and wavelength-tunable luminescence.
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Transparent Er3+ doped glass-ceramics containing KEr3F10:Er3+ nanocrystals were prepared via the traditional melt-quenching technique. The micro-structures, optical properties and up-conversion luminescence behaviors of the Er3+ doped glass-ceramics were systemically studied using X-ray diffraction, absorption and up-conversion luminescence spectra. Under the excitation of a laser at 980 nm, the intensity of red emission of the glass-ceramics increases more than 70 times after heat treatment compared with that of the precursor glass ceramic. Moreover, the fluorescence intensity ratio of the thermally coupled energy levels (2H11/2 and 4S3/2) shows a good linear relationship with temperature and maintains relatively high sensitivities of 0.398% per K at 303-573 K, which indicates that the glass ceramics have promising applications in temperature detection.
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[This corrects the article DOI: 10.1039/C9RA01945F.].
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A novel temperature sensor based on a Teflon capillary encapsulated 2 × 2 optical microfiber coupler (OMC) filled with refractive index matching liquids is described. The sealed capillary and the filling liquid are demonstrated to enhance the temperature sensing performance, achieving a high temperature sensitivity of 5.3 nm/°C. To the best of our knowledge, the temperature sensor described in this article exhibits the highest sensitivity among the OMC structure based fiber optic temperature sensors. Experimental results also show that it has good repeatability along with a fast response time of 243 ms.
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All solid-state PbS quantum dot (QD)-doped glass precursor fibers avoiding crystallization during fiber-drawing process are successfully fabricated by melt-in-tube technique. By subsequent heat treatment schedule, controllable crystallization of PbS QDs can be obtained in the glass precursor fibers, contributing to broad near-infrared emissions from PbS QD-doped glass fibers. Nevertheless, we find that element-migration and volatilization of sulfur simultaneously happen during the whole fiber-drawing process, because of the huge difference between the melting temperature of core glass and the fiber-drawing temperature. Element-migration pathways along the fiber length were revealed. Such PbS QD-doped glass fiber with broadband emissions will be a potential application as gain medium of broadband fiber amplifiers and fiber lasers.
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Selective doping of Ni2+ in octahedral sites provided by nanocrystals embedded in glass-ceramics (GCs) is crucial to the enhancement of broadband near-infrared (NIR) emission. In this work, a NIR emission with a full-width-at-half-maximum (FWHM) of 288 nm is first reported from ZnGa2O4: Ni2+ nano-spinels embedded GCs with excellent transparency. A comparison is made of the NIR luminescence properties of Ni2+ doped GCs containing ZnGa2O4, germanium-substituted ZnGa2O4 nano-spinels (Zn1+x Ga2-2x Ge x O4), and Zn2GeO4/Li2Ge4O9 composite nanocrystals that are free of Ga3+. The results show that ZnGa2O4: Ni2+ GCs exhibit a significantly enhanced NIR emission. The incorporation of the nucleating agent TiO2 is favored in terms of the increased luminescence intensity and prolonged lifetime. The possible causes for the enhancement effect are identified from the crystal structure/defects viewpoint. The newly developed GCs incorporate good reproducibility to allow for a tolerance of thermal treatment temperature and hence hold great potential of fiberization via the recently proposed "melt-in-tube" method. They can be considered as promising candidates for broadband fiber amplifiers.
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A glass-ceramic optical fiber containing Ba2TiSi2O8 nanocrystals fabricated using a novel combination of the melt-in-tube method and successive heat treatment is reported for the first time. For the melt-in-tube method, fibers act as a precursor at the drawing temperature for which the cladding glass is softened while the core glass is melted. It is demonstrated experimentally that following heat treatment, Ba2TiSi2O8 nanocrystals with diameters below 10 nm are evenly distributed throughout the fiber core. Comparing to the conventional rod-in-tube method, the melt-in-tube method is superior in terms of controllability of crystallization to allow for the fabrication of low loss glass-ceramic fibers. When irradiated using a 1030 nm femtosecond laser, an enhanced green emission at a wavelength of 515 nm is observed in the glass-ceramic fiber, which demonstrates second harmonic generation of a laser action in the fabricated glass-ceramic fibers. Therefore, this new glass-ceramic fiber not only provides a highly promising development for frequency conversion of lasers in all optical fiber based networks, but the melt-in-tube fabrication method also offers excellent opportunities for fabricating a wide range of novel glass-ceramic optical fibers for multiple future applications including fiber telecommunications and lasers.
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Functional nanocrystal-containing materials have been a hot topic in recent years. However, few researches have focused on functional nanocrystals contained in optical glass fibers. In this research, transparent CaF2 glass-ceramic was prepared by a melt-quenching method. Greatly enhanced upconversion luminescence was observed after heat treatment. By applying a novel method called melt-in-tube, precursor fiber free of crystals was fabricated at the drawing temperature where the clad was softened while the core was melted. Glass-ceramic fiber with fiber core containing Yb(3+)-Er(3+) codoped CaF2 nanocrystals was obtained after heat treatment at a relatively low temperature. Electron probe micro-analyzer measurement shows no obvious element diffusion between the core and clad. Greatly enhanced upconversion emission was detected in the glass-ceramic fiber excited by a 980 nm laser, suggesting the developed glass-ceramic fiber is a promising material for upconversion laser.
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Glass ceramic fibers containing Ni(2+) doped LiGa(5)O(8) nanocrystals were fabricated by a melt-in-tube method and successive heat treatment. Fiber precursors were prepared by drawing at high temperature where fiber core glass was melted while fiber clad glass was softened. After heat treatment, LiGa(5)O(8) nanocrystals were precipitated in the fiber core. Excited by 980 nm laser, efficient broadband near-infrared emission was observed in the glass ceramic fiber compared to that of precursor fiber. The melt-in-tube method can realize controllable crystallization and is suitable for fabrication of novel glass ceramic fibers. The Ni(2+)-doped glass ceramic fiber is promising for broadband optical amplification.