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Rational design and fabrication of multicolor fluorescent sources represent one of the significant challenges in the development of high‐performance solid‐state lighting, tunable coherent lasing, and full‐color display technologies. However, generation of simultaneous multicolor emission, especially white light generation with a wide color gamut is usually beyond the ability of a single material. Heterogeneous structures made by combinations of red, green, and blue emission building blocks are bulky, inefficient, complicated, and costly. Here reported is a bottom‐up strategy to generate simultaneous multicolor emission with continuous tunability in a single monolithic material based on the "nanocrystals‐in‐glass composite" (NGC) architecture. In this approach, a self‐sustained low‐temperature solution combustion process enables homogeneous solvent dispersion and eventually stable immobilization of multiple nanocrystals in transparent matrix. With transparency of up to 80%, further demonstrated is drawing of fiber from the melt of these combustion‐processed NGC materials. The optical spectra of the as‐drawn glass fiber can be precisely tuned and clustering is effectively suppressed. Moreover, the NGC materials exhibit remarkable anti‐thermal quenching behavior at temperatures of up to 200 °C. The bottom‐up strategy for NGC provides a versatile platform for the fabrication of high‐performance multifunctional fiber‐based devices for advanced applications in lasers, illumination, displaying, and biophotonics. [ABSTRACT FROM AUTHOR]

Rare earth (RE) ions‐doped luminescent nanocrystals (NCs) with numerous unique advantages have attracted tremendous interest for the wide applications from science to engineering, yet suffering from the shortcoming of thermal quenching coming from surface organic ligands. We propose utilizing a facile acid‐base reaction to remove surface organic ligands introduced choosing carboxylic acids as stabilizing agent and weaken thermal quenching. The results showed that the acid‐base reaction displayed an outstanding cleaning effect. After acid‐treatment, most surface organic ligands were removed, and there was no influence on crystal structure and morphology of as‐prepared β‐NaYF4:Er3+ NCs. Meanwhile, with no surface organic ligands capping, β‐NaYF4:Er3+ NCs preferred brighter emission after thermal treatment, including up‐conversion (UC), near‐infrared (NIR), and mid‐infrared (MIR) emission. When calcined the acid‐treated β‐NaYF4:Er3+ NCs in different atmosphere, such as oxygen and reducing atmosphere (15%H2 + 85%N2), an unexpected enhancement of all emission bands in Er3+ was determined under phase transformation temperature, especially in oxygen atmosphere. Furthermore, all the fluorescence lifetimes of Er3+ also exhibited obvious extension. Our results supposed that the β‐NaYF4:Er3+ NCs have promising applications in safety ink, and the acid‐treatment by diluted hydrochloric acid is a general approach to remove deleterious organic ligands on NC surface further to weaken thermal quenching. [ABSTRACT FROM AUTHOR]

Abstract: It is well recognized that a widely wavelength‐tunable mid‐infrared (MIR) fiber laser plays an important role in the development of compact and efficient coherent sources in the MIR range. Herein, the optimizing Er/Ho ratio for enhancement of broadband tunable MIR emission covering 2.6‐2.95 μm in the Er3+/Ho3+‐codoped transparent borosilicate glass‐ceramic (GC) fibers containing NaYF4 nanocrystals under 980 nm excitation was investigated. Specifically, the obtained GC fibers with controllable crystallization and well fsd‐maintained structures were prepared by the novel melt‐in‐tube approach. Owing to the effective energy transfer between Er3+ and Ho3+ after crystallization, the 2.7 μm MIR emission was obviously enhanced and the emission region showed a notable extension from 2.6‐2.82 μm to 2.6‐2.95 μm after the addition of Ho3+. Importantly, we conducted a theoretical simulation and calculation related to the MIR laser performance, signifying that the GC fiber may be a promising candidate for MIR fiber laser. Furthermore, the melt‐in‐tube approach will provide a versatile strategy for the preparation of diverse optical functional GC fibers. [ABSTRACT FROM AUTHOR]

Applications of trivalent rare earth (RE3+)‐doped light sources in solid‐state laser technology, optical communications, biolabeling, and solar energy management have stimulated a growing demand for broadband emission with flexible tunability and high efficiency. Codoping is a conventional strategy for manipulating the photoluminescence of active RE3+ ions. However, energy transfer between sensitizers and activators usually induces nonradiative migration depletion that brings detrimental luminescent quenching. Here, a transparent framework is employed to assemble ordered RE3+‐doped emitters to extend the emission spectral range by extracting photons from a variety of RE3+ ions with sequential energy gradient. To block migration‐mediated depletion between different RE3+ ions, a nanoscopic heterogeneous architecture is constructed to spatially confine the RE3+ clusters via a "nanocrystals‐in‐glass composite" (NGC) structure. This bottom‐up strategy endows the obtained RE3+‐doped NGC with high emission intensity (nearly one order of magnitude enhancement) and broadband near‐infrared emission from 1300 to 1600 nm, which covers nearly the whole low‐loss optical communication window. Most crucially, NGC is a versatile approach to design tunable broadband emission for the potential applications in high‐performance photonic devices, which also provides new opportunities for engineering multifunctional materials by integration and manipulation of diverse functional building units in a nanoscopic region. A tunable broadband emission is demonstrated by assembly of ordered rare‐earth‐doped emitters with sequential energy gradient. Migration‐mediated energy quenching has been successfully suppressed by nanoscopic heterogeneous structures constructed in transparent nanocrystals‐in‐glass composites. This assembly strategy highlights the possibility to fabricate multifunctional materials by linking different building units with photonic, magnetic, and electronic properties in a transparent framework. [ABSTRACT FROM AUTHOR]

The confinement of CsPbX 3 (X = Cl, Br, and I) perovskite nanocrystals (NCs) in a stabilized inorganic glass matrix is a new strategy for improving their long-term stability and promoting their applications in the optoelectronic field. Here, in situ nanocrystallization strategy is developed to precipitate CsPbBr 3− x I x NCs with arbitrary I/Br ratio among an elaborately designed GeS 2 –Sb 2 S 3 -based chalcogenide glass matrix. Spherical CsPbBr 3− x I x NCs are homogeneously distributed in the glass matrix after thermal treatment. The photoluminescence (PL) spectra show that the emission peaks of CsPbBr 3− x I x NCs can be tuned from 570 nm to 722 nm with the replacement of Br by I. The fs transient absorption (TA) spectra reveal that there exists some structural defects in the NCs, leading to short PL decay life. This work would shed light on confining CsPbX 3 NCs into glassy matrices, facilitating their future applications in photoelectronic fields. [ABSTRACT FROM AUTHOR]