Ethanol-Precipitable, Silica-Passivated Perovskite Nanocrystals Incorporated into Polystyrene Microspheres for Long-Term Storage and Reusage

CsPbBr3 perovskite quantum dots-based Janus membrane with multifunction of luminescence, magnetism and aeolotropic electroconductivity

Lead halide perovskite quantum dots (QDs) are promising semiconductors for next-generation photoelectric devices. However, the development of perovskite QDs-based multifunctional materials still needs to be addressed in order to further advance the application of perovskite QDs. Herein, a successful synthesis of Janus microfibers array Janus membrane (JMAJM) with up-down structure and multifunction of luminescence, magnetism and electroconductivity is firstly achieved based on CsPbBr3 QDs through a parallel electrospinning. JMAJM comprises up-down two layers tightly bonded together. The up-layer of JMAJM is luminescence/magnetism Janus microfibers array (L/M-JMAJM) constructed by [CsPbBr3/polymethyl methacrylate (PMMA)]//[CoFe2O4/PMMA] Janus microfibers as building elements. The down-layer of JMAJM is luminescence/electroconductivity Janus microfibers array (L/E-JMAJM) fabricated by [CsPbBr3/PMMA]//[polyaniline (PANI)/PMMA] Janus microfibers as building elements. Two independent microcosmic regions are designed and realized in a Janus microfiber, confining luminescence with magnetic or conductive substances into their respective regions, thus minimizing adverse effects of other dark-colored functional substances on the fluorescence of CsPbBr3 QDs. This peculiar Janus microfiber enables the effective separation and high integration of CsPbBr3 QDs with other functional substances. The up-down structure of JMAJM ensures a high integration of luminescence, magnetism and conductivity. Meanwhile, JMAJM addresses the environmental instability of CsPbBr3 QDs while simultaneously endows perovskite QDs-based materials with additional functions to realize multifunction. Under ultraviolet excitation, fluorescence characteristics of the CsPbBr3 QDs in JMAJM are maintained, exhibiting a vibrant green emission at 517 nm. Meanwhile, JMAJM achieves a maximum saturation magnetization of 20.32 emu·g-1, high conductance of 10-2 S and aeolotropic electroconductivity degree of 107. The combination of micro-partition with macro-partition in JMAJM receives superior concurrent luminescence-magnetic-conductive multifunction. This work provides a novel idea and strategy for advancing perovskite QDs-based multifunctional materials.

Green-route manufacturing towards future industrialization of metal halide perovskite nanocrystals

Perovskite nanocrystals (PeNCs) with excellent optical properties have attracted tremendous research interests and have been considered as promising candidates for new-generation optoelectronic devices. Over the past few years, numerous efforts have been made to overcome the challenges in terms of sustainable manufacturing of PeNCs and related devices and systems, including the solvents used in precursor preparation, antisolvents and perovskite materials for the fabrication of devices and systems, and remarkable progress has been made. However, the usage of toxic, organic solvents in the synthesis of PeNCs poses a threat to the ecosystem and human health, which has hindered the progress in the commercialization and industrialization of PeNCs. This has promoted the development of green solvents for the sustainable manufacturing of PeNCs. In this Feature Article, a state-of-the-art green method for the synthesis of PeNCs is presented, in which the solvents of low toxicities are underlined in contrast to the reported Reviews which focus on toxic solvents for the preparation of precursor solutions. We then focus on green, aqueous methods for the preparation of PeNCs, including conventional perovskite and double PeNCs, by summarizing our previous research efforts and studies. In particular, pure water as the greenest solvent is introduced for the preparation of PeNCs, and the parameters affecting the size and optical characteristics of PeNCs, such as sonication time and ligands for post-treatment, are discussed. The strategies of using a passivation layer to improve the aqueous stability of PeNCs are reviewed, which are grouped into organic polymers and inorganic semiconductors. We highlight the challenges and possible solutions in the green manufacturing and applications of PeNCs. The green routes discussed in this article for the synthesis of PeNCs are expected to be a major step forward for the commercialization and industrialization of the fabrication of PeNCs. It is anticipated that green manufacturing will continue to be the mainstream in the synthesis and fabrication of PeNCs.

CsPbBr3 Perovskite Nanoparticles causes Colitis-Like Symptom via Promoting Intestinal Barrier Damage and Gut Microbiota Dysbiosis

Lead-based perovskite nanoparticles (Pb-PNPs) with superior optoelectronic properties are promising alternatives for the next generation of photovoltaics materials. This raises a great concern about their potential exposure toxicity in biological systems. However, little is known about their adverse effects on the gastrointestinal tract system so far. Here, the aim is to investigate the biodistribution, biotransformation, potential gastrointestinal tract toxicity, and effect on the gut microbiota after oral exposure to the CsPbBr3 perovskite nanoparticles (CPB PNPs). The advanced synchrotron radiation based microscopic X-ray fluorescence scanning and X-ray absorption near-edge spectroscopy demonstrate that high doses of CPB (CPB-H) PNPs can gradually transform into different lead-based compounds, subsequently accumulating in the gastrointestinal tract, especially the colon. Meanwhile, the pathological changes of stomach, small intestine, and colon reveal that CPB-H PNPs have higher gastrointestinal tract toxicity than Pb(Ac)2 , consequently leading to colitis-like symptoms. More importantly, 16S rRNA gene sequencing analysis discloses that CPB-H PNPs cause more significant alterations in the richness and diversity of the gut microbiota related to inflammation, intestinal barrier, and immune function than Pb(Ac)2 . The findings may contribute to shedding light on understanding the adverse effects on gastrointestinal tract and gut microbiota of Pb-PNPs.

Ratiometric fluorescence sensing of temperature based on perovskite nanocrystals and rhodamine B doped electrospun fibers

Sensing temperature (T) has gained great attention since T is the most important parameter in daily life, scientific research and industry. A ratiometric fluorescence T sensor is fabricated by doping MAPbBr3 perovskite nanocrystals (PNCs) and rhodamine B (RhB) into a polyacrylonitrile (PAN) matrix and the composite materials are electrospun into optical fibers. The fibers show characteristic emissions at 521 and 587 nm under UV irradiation (λ ex = 365 nm). Both emission intensities gradually increased with elevating T, accompanied with a fluorescence color change from green to yellow. There is a linear relationship between fluorescence intensity ratio (I 521/I 587) and T in the range of 30-45 °C. The T response sensitivity is as high as 4.38% °C-1 at 45 °C.

Cesium lead iodide electrospun fibrous membranes for white light-emitting diodes

Inorganic perovskite cesium lead iodide nanocrystals (CsPbI3NCs) are good candidates for optoelectronic devices because of their excellent properties of remarkable luminous performance (high luminous efficiency, narrow luminous spectral line), and high photoelectric conversion efficiency by using simple preparation method. But their inherent poor stability greatly limits its practical applications. In this paper, electrospinning is used to grow fibrous membranes with embedded cesium lead iodide perovskite nanocrystals (PNCs) formedin situin a one-step process. It was found that cubicα-CsPbI3PNCs were formed in polymer fibers, showing bright and uniform fluorescence signals. Furthermore, the water wetting angles were increased by the fibrous structure enhancing the hydrophobicity and the stability of the fibrous membranes in water. The electrospun fibrous membrane containing CsPbI3was combined with another membrane containing CsPbBr3under a blue light-emitting diode (LED) to create a white LED (WLED) in air successfully with CIE coordinates (0.3020, 0.3029), and a correlated color temperature of 7527 °K, indicating high purity of WLED. Our approach provides a new way to create highly stable, photoluminescent water-resistant perovskite nanocrystalline films.

Synthesis of Chemically Stable Ultrathin SiO2-Coated Core-Shell Perovskite QDs via Modulation of Ligand Binding Energy for All-Solution-Processed Light-Emitting Diodes

Recently, perovskite quantum dots (QDs) have attracted intensive interest due to their outstanding optical properties, but their extremely poor chemical stability hinders the development of the high-performance perovskite QD-based light-emitting diodes (PeLEDs). In this study, chemically stable SiO₂-coated core-shell perovskite QDs are prepared to fabricate all-solution-processed PeLEDs. When the SiO₂ shell thickness increases, the chemical stability of perovskite QDs is dramatically improved, while the charge injection efficiency is significantly decreased, which becomes the biggest obstacle for PeLED applications. Thus, controlling the SiO₂ thickness is essential to obtain core-shell perovskite QDs optimal for PeLEDs in an aspect of chemical and optoelectrical properties. The 3-aminopropyl-triethoxysilane (APTES)/oleylamine (OAm) volume ratio is found to be a critical factor for obtaining an ultrathin SiO₂ shell. Optimization of the APTES/OAm ratio affords A-site-doped CsPbBr₃ QDs with an ultrathin SiO₂ shell (A-CsPbBr₃@SiO₂ QDs) that exhibit longer radiative lifetimes and smaller shallow trap fraction than those without A-site doping, resulting in a higher photoluminescence quantum yield. A-CsPbBr₃@SiO₂ QDs also demonstrate long-term superior chemical stability in polar solvents without loss of optical properties due to passivation by the SiO₂ shell and less defects via A-site doping. Consequently, all-solution-processed PeLED is successfully fabricated under ambient conditions, facilitating perovskite QD utilization in low-cost, large-area, flexible next-generation displays.

Metal Halide Perovskite/2D Material Heterostructures: Syntheses and Applications

The past decade has witnessed the great success achieved by metal halide perovskites (MHPs) in photovoltaic and related fields. However, challenges still remain in further improving their performance, as well as, settling the stability issue for future commercialization. Recently, MHP/2D material heterostructures that combining MHPs with the low-cost and solution-processable 2D materials have demonstrated unprecedented improvement in both performance and stability due to the distinctive features at hetero-interface. The diverse fabrication techniques of MHPs and 2D materials allow them to be assembled as heterostructures with different configurations in a variety of ways. Moreover, the large families of MHPs and 2D materials provide the opportunity for the rational design and modification on compositions and functionalities of MHP/2D materials heterostructures. Herein, a comprehensive review of MHP/2D material heterostructures from syntheses to applications is presented. First, various fabrication techniques for MHP/2D material heterostructures are introduced by classifying them into solid-state methods and solution-processed methods. Then the applications of MHP/2D heterostructures in various fields including photodetectors, solar cells, and photocatalysis are summarized in detail. Finally, current challenges for the development of MHP/2D material heterostructures are highlighted, and future opportunities for the advancements in this research field are also provided.

Room-Temperature In Situ Synthesis of a Highly Efficient CsPbBr3/SiO2 Sol Entirely in Ethanol Solvent by Constructing Amine-Functionalized Silica Micelles

Cesium lead halide perovskite nanocrystals (CLHP NCs) have drawn considerable attention because of their promising optoelectrical properties. However, owing to the extreme vulnerability of CLHP NCs to water and polar alcohols, until now most synthesis approaches inevitably adopted ecounfriendly solvents. It is still a challenge to employ green polar alcohol (ethanol) as a solvent to synthesize CLHP NCs. In this work, we realized the room-temperature in situ synthesis of CsPbBr₃/SiO₂ sol entirely in ethanol by innovatively constructing amine-functionalized silica micelles, which originated from the synergistic effect of 3-aminopropyltriethoxysilane and tetraethylorthosilicate (TEOS) during an acid-catalyzed sol-gel process. The sol exhibited high stability and an absolute photoluminescence quantum yield of 61.9% in ethanol without a further modification process. The light-emitting intensity of the sol preserved for 34 days merely declined to 62.1%. This work sheds light on the less common strategy of directly synthesizing CsPbBr₃ NCs and long-term stable preservation in a strongly polar solvent.

Surface functionalization on nanoparticles via atomic layer deposition

As an ultrathin film preparation method, atomic layer deposition (ALD) has recently found versatile applications in fields beyond semiconductors, such as energy, environment, catalysis and so on. The design, preparation and characterization of thin film applied in the emerging fields have attracted great interests. The development of ALD technique on particles opens up a broad horizon in the advanced nanofabrication. Pioneering applications are exploring conformal coating, porous coating and selective surface modification of nanoparticles. Conformal encapsulation of particles is a major application to protect materials with ultrathin films from being eroded by the external environment while keeping the original properties of the primary particles. Porous coating has been developed to simultaneously expose the particles' surface and provide nanopores, which is another important method that demonstrates its advantages in modification of electrode materials, catalysis and energy applications, etc. Selective ALD takes the method forward in order to precisely control the directionality of decoration sites on the particles and selectively passivate undesired facets, sites, or defects. Such methods provide practical strategies for atomic scale and precise surface functionalization on particles and greatly expand its potential applications.

Room-Temperature in Situ Synthesis of Highly Efficient CsPbBr3/SiO2 Sol in Entirely Ethanol Solvent by Constructing Amine-Functionalized Silica Micelles

Cesium lead halide perovskite nanocrystals (CLHP NCs) have drawn considerable attention because of their promising optoelectrical properties. However, owing to extreme vulnerability of CLHP NCs to water and polar alcohols, up to date, most of the synthesis approaches have inevitably adopted eco-unfriendly solvents. It is still a big challenge to employ green polar alcohol (ethanol) as a solvent to synthesize CLHP NCs. In this work, we realized a room-temperature in situ synthesis of CsPbBr₃/SiO₂ sol entirely in ethanol by innovatively constructing amine-functionalized silica micelles, which is originated from the synergistic effect of 3-aminopropyltriethoxysilane and tetraethyl orthosilicate (TEOS) during an acid-catalyzed sol-gel process. The sol exhibited high stability and an absolute photoluminescence quantum yield of 61.9% in ethanol without a further modification process. The light emitting intensity of the sol preserved for 34 days merely declined to 62.1%. This work sheds light on the less common strategy of directly synthesizing CsPbBr₃ NCs and long-term stable preservation in a strong polar solvent.

Stable Perovskite Quantum Dots Coated with Superhydrophobic Organosilica Shells for White Light-Emitting Diodes

Metalammonium lead perovskite (MAPbX₃ , MA=CH₃ NH₃ ⁺ ; X=Cl, Br, I) quantum dots (QDs) have attracted tremendous attention due to their outstanding optical properties. However, they usually suffer from poor stability towards water or moisture, which seriously limits their practical applications. Here, we report a simple and effective approach to improve the stability of MAPbBr₃ QDs by encapsulating them with superhydrophobic fluorinated organosilica (FSiO₂ ) shells. The water-resistant stability of the superhydrophobic MAPbBr₃ QDs/FSiO₂ is significantly enhanced and they display strong fluorescence even after immersion in water for 12 hours. This method is readily extended to prepare superhydrophobic MAPbBr_2.4 Cl_0.6 QDs/FSiO₂ and MAPbI₃ QDs/FSiO₂ powders. These superhydrophobic MAPbX₃ QDs/FSiO₂ can be further used to fabricate white light-emitting diodes (LEDs) with comparable color to pure white emission.