Dual-Modal Photon Upconverting and Downshifting Emissions from Ultra-stable CsPbBr3 Perovskite Nanocrystals Triggered by Co-Growth of Tm:NaYbF4 Nanocrystals in Glass

Design and assembly of AIE-active fluorescent organic nanoparticles for anti-counterfeiting fluorescent hydrogels and inks

Two kinds of AIE-active fluorescent organic nanoparticles were designed and constructed as anti-counterfeiting photoresponsive materials. One is fluorescent organic nanoparticles (TPELs) based on a self-assembly strategy, which were self-assembled from novel amphiphilic tetraphenylethylene (TPE) molecules decorated with a lactose moiety and different photoresponsive tags. The other is polymeric fluorescent organic nanoparticles (F-TPEs) derived from the nanoprecipitation strategy, which utilized pluronic copolymer F127 to encapsulate hydrophobic TPEs without lactosyl modifications. Upon UV light irradiation, these AIE-active materials exhibit different photooxidation behaviors in an aqueous solution to give cyan, orange and green fluorescence emissions, and they were successfully used as an anti-counterfeiting fluorescent hydrogel and ink.

Advanced composite glasses with metallic, perovskite, and two-dimensional nanocrystals for optoelectronic and photonic applications

This article reviews the tremendous advancement of the optoelectronic and photonic properties of inorganic oxide glasses upon the incorporation of metallic, perovskite, and two-dimensional nanocrystals within their matrix. In the first part, we present the exploitation of typical inorganic oxide glasses as hosting platforms for the incorporation of metallic nanoparticles. Such a method offers tremendous advantages in terms of inducing plasmonic features that enable the tunability of the photonic properties of the embedded materials. Along similar lines, due to their exceptional photoluminescence properties all inorganic lead halide perovskites show enormous potential for next generation light-emitting, optoelectronic and photonic devices. To date, however, their usage is limited significantly by their poor chemical stability upon exposure to moisture, and lead toxicity issues. A recent and highly promising approach for overcoming these important challenges is the encapsulation of perovskite nanocrystals within inorganic oxide glasses. Based on this, in the second section we focus on the recent advancements in perovskite glasses in terms of the developed fabrication procedures and the resulting optoelectronic features, while considering the production limitations. In the last part, we consider the development of composite two-dimensional materials glass architectures in terms of the available synthesis routes and the novelty of their optical and emission features. Finally, future perspectives on the described composite glass systems in terms of potential applications are summarized.

Effect of Glass Composition on Luminescence and Structure of CsPbBr3 Quantum Dots in an Amorphous Matrix

Glass matrix embedding is an efficient way to improve the chemical and thermal stability of the halide perovskite QDs. However, CsPbX₃ QDs exhibit distinct optical properties in different glass matrixes, including photoluminescence (PL) peak position, PL peak width, and optical band gap. In this work, the temperature-dependent PL spectra, absorption spectra, high-energy X-ray structure factor S(Q), and pair distribution function (PDF) were integrated to analyze the structural evolution of CsPbBr₃ QDs in different glass matrixes. The results show that the lattice parameters and atomic spacing of CsPbBr₃ QDs are affected by the glass composition in which they are embedded. The most possibility can be attributed to the thermal expansion mismatch between CsPbBr₃ QDs and the glass matrix. The results may provide a new way to understand the effect of the glass composition on the optical properties of CsPbBr₃ QDs in a glass matrix.

Upconversion Perovskite Nanocrystal Heterostructures with Enhanced Luminescence and Stability by Lattice Matching

Lead halide perovskite quantum dots (PQDs) exhibit excellent photoelectric and optical properties, but their poor stability and low multiphoton absorption efficiency greatly limit their biological applications. Efforts have been made to combine upconversion nanoparticles (UCNPs) with PQDs to produce a composite material that is NIR-excitable, upconverting, and emission-tunable due to the unique optical properties of UCNPs, which converts tissue-penetrating near-infrared light into visible light based on an upconversion multiphoton excitation process. However, it is challenging to make such a nanocrystal heterostructure and maintain good optical properties and stability of both UCNPs and PQDs because they have different crystal structures. Here, we report the synthesis of heterostructured UCNP-PQD nanocrystals to bring hexagonal-phase NaYF₄ UCNPs and cubic-phase CsPbBr₁X₂ PQDs in close proximity in a single nanocrystal, leading to efficient Förster resonance energy transfer (FRET) from the UCNP to the PQD under NIR excitation, as compared to their counterparts in solution. Moreover, by further improving the lattice matching between the UCNP and PQD using Gd to replace Y, heterostructured CsPbBr₃-NaGdF₄:Yb,Tm nanocrystals are successfully synthesized, with much enhanced luminescence and stability at high temperatures or in polar solvents or under continuous ultraviolet light excitation as compared to those of the CsPbBr₃-NaYF₄:Yb,Tm nanocrystals and pure PQDs.

Carbon Dots-in-EuAPO-5 Zeolite: Triple-Emission for Multilevel Luminescence Anti-Counterfeiting

Multilevel luminescence materials have aroused wide attention for their advanced anti-counterfeiting abilities. However, various complicated stimuli factors involved in multilevel luminescence anti-counterfeiting (MlLA) limit the practical applications of such materials. Herein, carbon dots (CDs) are in situ introduced into Eu-substituted AlPO₄ -5 zeolite (named CDs@EuAPO-5) via a solvent-free thermal crystallization method, which exhibits triple emissions including pink fluorescence mainly associated with Eu³⁺ in the zeolite framework, blue fluorescence and green room temperature phosphorescence (RTP) associated with CDs. CDs are uniformly embedded in the EuAPO-5 zeolite matrix. Such composite displays excellent photo-, thermo-, and solvent resistance, as well as long-term storage-stability. Moreover, the triple emissions of the composite only need two kinds of common excitation lights to trigger, without involving other complicated stimuli. A triple-level luminescence anti-counterfeiting (TlLA) label has been built, realizing facile, quick, and advanced luminescence anti-counterfeiting that is hard to copy.

Pure green emission self-crystallization CsPbBr3 quantum dot glass with Ag+ doping for stable light-emitting devices

Recently, cesium lead bromide perovskite glass has been recognized as a potential material to fabricate green light emission devices because of their high stability and excellent optical performance. However, the low photoluminescence efficiency and poor color purity ($\lt\! 525\,\,{\rm nm}$) of ${{\rm CsPbBr}_3}$ quantum dot (QD) glass restricts its practical application. In this work, self-crystallization ${{\rm CsPbBr}_3}$ QD glasses are successfully prepared via the melt quenching method, and the photoluminescence efficiency increases 10-fold compared with regular thermal treatment ${{\rm CsPbBr}_3}$ QD glass without ${\rm Ag}^+$ doping. The green light-emitting devices based on bulk self-crystallization ${{\rm CsPbBr}_3}$ QD glass with 0.4 mol.% ${\rm Ag}^+$ doping achieves a luminescence efficiency of 20.85 lm/W with a CIE (0.2084, 0.6026) under a 20 mA driving current. The present results provide new, to the best of our knowledge, insight into the application of ${{\rm CsPbBr}_3}$ QD glass in the optoelectronic field.

Nano-Crystallization of Ln-Fluoride Crystals in Glass-Ceramics via Inducing of Yb3+ for Efficient Near-Infrared Upconversion Luminescence of Tm3

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.

Stable and Efficient Upconversion Single Red Emission from CsPbI3 Perovskite Quantum Dots Triggered by Upconversion Nanoparticles

Here, composites including highly efficient inert shell-modified NaYF₄:Yb/Tm@NaYF₄ upconversion nanoparticles (UCNPs) and CsPbI₃ perovskite quantum dots (PQDs) have been successfully synthesized by the assistance of (3-aminopropyl)triethoxysilane (APTES) as a precursor for a SiO₂ matrix. UCNPs and CsPbI₃ PQDs in this composite structure show excellent stability in ambient conditions. Importantly, the efficient UC emission of CsPbI₃ PQDs was realized, which means that the single red emission of inert shell-modified UCNPs can be easily obtained by depending on these composite structures. Furthermore, the single red emission wavelength can be easily regulated from 705 to 625 nm by introducing appropriate proportion of Br^- ions, which is very difficult to achieve for traditional UCNPs. Moreover, benefiting from the efficient downshifting (DS) red emission of CsPbI₃ PQDs, the composites possess the dual-wavelength excitation characteristics. So, the excellent dual-mode anticounterfeiting application has been demonstrated. This work will provide a new idea for the development of perovskite-based multifunctional materials.

Highly luminescent and ultrastable cesium lead bromide perovskite patterns generated in phosphate glass matrices

Owing to their exceptional optoelectronic properties, all-inorganic lead halide perovskites offer enormous potential for next generation photonic, light-emitting, and optoelectronic devices. However, their usage is significantly limited by their poor stability upon moisture exposure and lead toxicity issues. Moreover, many of the aforementioned applications rely on the development of confined perovskite patterns of various shapes and periodicities. Here we report a simple and low-temperature method enabling the controlled incorporation of photoluminescent all-inorganic metal halide PNCs into a silver phosphate glass (AgPO3) matrix which is transparent in most of the visible range. The developed fabrication protocol is based on a simple melting encapsulation process in which pre-synthesized perovskite crystals are inserted in the glass matrix, following the initial glass quenching. Using this novel approach, two types of composite perovskite glasses are prepared, one that hosts perovskite isles and the second in which a thin perovskite layer is embedded beneath the glass surface. Both types of composite glasses exhibit remarkable photoluminescence stability when compared to the ambient air-exposed perovskite crystals. More importantly, by means of a simple and fast cw-laser processing technique, we demonstrate the development of encapsulated dotted perovskite micropatterns within the composite perovskite glass. The ability of the proposed system to resolve stability and lead toxicity issues, coupled with the facile formation of highly luminescent perovskite patterns pave the way towards the broad exploitation of perovskite crystals in photonic applications.