The utility of electronically conductive metal–organic frameworks (EC‐MOFs) in high‐performance devices has been limited to date by a lack of high‐quality thin film. The controllable thin‐film ...fabrication of an EC‐MOF, Cu3(HHTP)2, (HHTP=2,3,6,7,10,11‐hexahydroxytriphenylene), by a spray layer‐by‐layer liquid‐phase epitaxial method is reported. The Cu3(HHTP)2 thin film can not only be precisely prepared with thickness increment of about 2 nm per growing cycle, but also shows a smooth surface, good crystallinity, and high orientation. The chemiresistor gas sensor based on this high‐quality thin film is one of the best room‐temperature sensors for NH3 among all reported sensors based on various materials.
A wafer‐thin sensor: The preparation of a crystalline, highly‐oriented, and thickness‐controlled thin film with an electronically conductive MOF is reported. Chemiresistive sensors based on these thin films show a high response, excellent selectivity, fast response speed, and good long‐term stability towards NH3 gas at room temperature.
Administration of exosomes derived from mesenchymal stromal cells (MSCs) could improve some neurologic conditions by transferring functional biomolecules to recipient cells. Furthermore, exosomes ...from hypoxic progenitor cells exerted better therapeutic effects in organ injury through specific cargoes. However, there are no related reports about whether exosomes derived from MSCs or hypoxia‐preconditioned MSCs (PC‐MSCs) could prevent memory deficits in Alzheimer disease (AD). In this study, the exosomes derived from MSCs or PC‐MSCs were systemically administered to transgenic APP/PS1 mice. The expression of miR‐21 in MSCs was significantly increased after hypoxic treatment. Injection of exosomes from normoxic MSCs could rescue cognition and memory impairment according to results of the Morris water maze test, reduced plaque deposition, and Aβ levels in the brain; could decrease the activation of astrocytes and microglia; could down‐regulate proinflammatory cytokines (TNF‐α and IL‐1β); and could up‐regulate anti‐inflammatory cytokines (IL‐4 and ‐10) in AD mice, as well as reduce the activation of signal transducer and activator of transcription 3 (STAT3) and NF‐κB. Compared to the group administered exosomes from normoxic MSCs, in the group administered exosomes from PC‐MSCs, learning and memory capabilities were significantly improved; the plaque deposition and Aβ levels were lower, and expression of growth‐associated protein 43, synapsin 1, and IL‐10 was increased; and the levels of glial fibrillary acidic protein, ionized calcium‐binding adaptor molecule 1, TNF‐α, IL‐1β, and activation of STAT3 and NF‐κB were sharply decreased. More importantly, exosomes from PC‐MSCs effectively increased the level of miR‐21 in the brain of AD mice. Additionally, replenishment of miR‐21 restored the cognitive deficits in APP/PS1 mice and prevented pathologic features. Taken together, these findings suggest that exosomes from PC‐MSCs could improve the learning and memory capabilities of APP/PS1 mice, and that the underlying mechanism may lie in the restoration of synaptic dysfunction and regulation of inflammatory responses through regulation of miR‐21.—Cui, G.‐H., Wu, J., Mou, F.‐F., Xie, W.‐H., Wang, F.‐B., Wang, Q.‐L., Fang, J., Xu, Y.‐W., Dong, Y.‐R., Liu, J.‐R., Guo, H.‐D. Exosomes derived from hypoxia‐preconditioned mesenchymal stromal cells ameliorate cognitive decline by rescuing synaptic dysfunction and regulating inflammatory responses in APP/PS1 mice. FASEB J. 32, 654–668 (2018). www.fasebj.org
Fly ash is the fine solid particulate residue driven out of the boiler with the flue gases in coal-fired power plants. Now it can be used for making geopolymer which acts as a cement-like product. ...The geopolymer technology provides an alternative good solution to the utilization of fly ash with little negative impact on environment. This review summarizes and examines the scientific advances in the preparation, properties and applications of fly ash-based geopolymer. The production of fly ash-based geopolymer is mainly based on alkali activated geopolymerization which can occur under mild conditions and is considered as a cleaner process due to much lower CO2 emission than that from the production of cement. The geopolymerization can trap and fix the trace toxic metal elements from fly ash or external sources. The Si/Al ratios, the type and the amount of the alkali solution, the temperature, the curing conditions, and the additives are critical factors in a geopolymerization process. The mechanical performances of the fly ash-based geopolymer, including compressive strength, flexural and splitting tensile strength, and durability such as the resistance to chloride, sulfate, acid, thermal, freeze-thaw and efflorescence, are the primary concerns. These properties of fly ash-based geopolymer are inherently dependent upon the chemical composition and chemical bonding and the porosity. The mechanical properties and durability can be improved by fine tuning Si/Al ratios, alkali solutions, curing conditions, and adding slag, fiber, rice husk-bark ash and red mud. Fly ash-based geopolymer is expected to be used as a kind of novel green cement. Fly ash-based geopolymer can be used as a class of materials to adsorb and immobilize toxic or radioactive metals. The factors affecting the performances of fly ash-based geopolymer concrete, in particular aggregate, are discussed. For future studies on fly ash-based geopolymer, further enhancing mechanical performance, scaling up production and exploring new applications are suggested.
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•Fly ash is activated by alkali to form geopolymer and such a process is cleaner.•Slag, rice husk-bark ash, fiber and red mud are added to improve the performance of fly ash-based geopolymer.•Mechanical properties and durability of fly ash-based geopolymer are main concerns.•Fly ash-based geopolymer is used as cement and as fixation materials for toxic metals.•Improving performance, scaling-up production and finding new applications are proposed for future.
Low‐dimensional lead halide perovskite materials recently have drawn much attention owing to the intriguing broadband emissions; however, the toxicity of lead will hinder their future development. ...Now, a lead‐free (C4H14N2)2In2Br10 single crystal with a unique zero‐dimensional (0D) structure constituted by InBr63− octahedral and InBr4− tetrahedral units is described. The single crystal exhibits broadband photoluminescence (PL) that spans almost the whole visible spectrum with a lifetime of 3.2 μs. Computational and experimental studies unveil that an excited‐state structural distortion in InBr63− octahedral units enables the formation of intrinsic self‐trapped excitons (STEs) and thus contributing the broad emission. Furthermore, femtosecond transient absorption (fs‐TA) measurement reveals that the ultrafast STEs formation together with an efficient intersystem crossing has made a significant contribution to the long‐lived and broad STE‐based emission behavior.
A lead‐free indium‐based (C4H14N2)2In2Br10 single crystal was synthesized and characterized; it has a unique 0D crystal structure. An intrinsic self‐trapped exciton‐based ultra‐broad photoluminescence has been observed as a result of an excited‐state structural distortion in InBr63− octahedrons.
Low‐dimensional luminescent lead halide perovskites have attracted tremendous attention for their fascinating optoelectronic properties, while the toxicity of lead is still considered a drawback. ...Herein, we report a novel lead‐free zero‐dimensional (0D) indium‐based perovskite (Cs2InBr5⋅H2O) single crystal that is red‐luminescent with a high photoluminescence quantum yield (PLQY) of 33 %. Experimental and computational studies reveal that the strong PL emission might originate from self‐trapping excitons (STEs) that result from an excited‐state structural deformation. More importantly, the in situ transformation between hydrated Cs2InBr5⋅H2O and the dehydrated form is accompanied with a switchable dual emission, which enables it to act as a PL water‐sensor in humidity detection or the detection of traces of water in organic solvents.
Unleaded and unleashed: A highly emissive lead‐free indium‐based perovskite single crystal, Cs2InBr5⋅H2O, was successfully prepared. The versatile material is the first reversible metal halide perovskite photoluminescence water sensor and paves the way for the application of metal halide perovskites in water detection.
All‐inorganic bismuth‐halide perovskites are promising alternatives for lead halide perovskites due to their admirable chemical stability and optoelectronic properties; however, these materials ...deliver inferior photoluminescence (PL) properties, severely hindering their prospects in lighting applications. Here, a novel air‐stable but non‐emissive perovskite Rb3BiCl6 is synthesized, and the material is used as a prototype to uncover origin of the poor optical performance in bismuth‐halide perovskite. It is found that the extremely strong exciton–phonon interactions with a large coupling constant up to 693 meV leads to the seriously nonradiative recombination, which, however, can be effectively suppressed to 347 meV by introducing Sb3+ ions. As a result, Sb3+‐doped Rb3BiCl6 exhibits a stable yellow emission with unprecedented PL quantum yield up to 33.6% from self‐trapped excitons. Systematic spectroscopic characterizations and theoretical calculations are carried out to unveil the intriguing photophysical mechanisms. This work reveals the effect of exciton–phonon interaction, that is often underemphasized, on a material's photophysical properties.
All‐inorganic lead‐free bismuth‐halide perovskite with excellent structural stability shows inferior photoluminescence performance due to the extremely strong exciton–phonon interaction, which however can be effectively suppressed by an ion doping strategy. This work provides a new avenue for the development of high‐performance luminous perovskites (or metal halides) by manipulating the exciton–phonon interaction.
A hybrid photocatalytic assembly with Ni poly‐pyridine polymers binding on CdS quantum dots was developed via thiophene immobilization. The fabricated hybrid assembly facilitated efficient charge ...separation, and each component endowed great synergy. As a result, a high syngas production rate was achieved over 5500 μmol gcat−1 h−1 from photocatalytic CO2 reduction under visible‐light irradiation, accompanied by an adjustable H2/CO ratio ranging from 4 : 1 to 1 : 3. A novel hybrid assembly was described for syngas synthesis with boosted activity and controlled selectivity, which provides a profile to ingeniously understand molecular‐level design for photocatalysts.
CO2 to syngas: A hybrid photocatalyst is assembled by a Ni poly‐pyridine polymer binding on CdS substrate via vinyl‐thiophene towards photo‐reducing CO2 into syngas with tunable H2/CO ratio. Each component in the fabricated hybrid endows great synergy. It shows a robust activity, which is superior to reported results on semiconductor‐based photocatalysts.
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