The production of alkyl levulinates from furfuryl alcohol (FAL) in alcohol media was investigated at moderate temperature in the presence of Brønsted acidic ionic liquids. The reaction was examined and optimized under batch conditions, where it was found that furfuryl alcohol was rapidly and almost quantitatively converted into intermediate products including 2-alkoxymethylfuran and 4,5,5-trialkoxypentan-2-one, and high alkyl levulinates yield of 95% can be achieved after reaching a steady state in 2 h. An advantage of this catalyst system is that undesired dialkyl ether (DEE) formed by a side reaction of the dehydration of alcohol is negligible. The Hammett method was used to determine the acidities of these ionic liquids, which indicated that the acidity and the molecular structure have strong effects on the catalytic activity of ionic liquids. Based on the experimental results, a possible mechanism for the alcoholysis of FAL is proposed.
PNIPA/clay nanocompoiste gels with co-cross-linked networks were synthesized by in-situ, freeradical polymerization of NIPA (N-isopropylacrylmaide) in the presence of two types of cross-linker, an inorganic cross-linker (clay: hectorite) and an organic cross-linker (N,N′-methylenebis(acrylamide): BIS), with concentrations n and m, respectively, in aqueous media. The optical properties and the tensile and compressive mechanical properties of the resulting hydrogels (NCn-ORm gels) were investigated and are discussed herein in terms of co-cross-linked PNIPA network structures. NCn-ORm gels were all uniform, but their transparencies changed considerably according to n and m and were generally different from the sum of the transparencies of corresponding NCn and ORm gels. NCn-ORm gels generally exhibited pronounced weakness and brittleness in tensile tests, like ORm gels. In contrast, in compressive mechanical tests, large improvements were achieved at high n and low m values (m e 1: e.g., NC5-OR0.3). Furthermore, abnormal increases in modulus were observed in both mechanical tests. All of these results are explained by the formation of a "microcomplex structure" consisting of exfoliated clay platelets and PNIPA chains with enhanced chemical cross-linking. The mechanism of forming the proposed microcomplex structure is discussed and is based on a preferential distribution of BIS to clay in the reaction solution and the formation of clay-brush particles during synthesis.
Transition metal sulfides are deemed as attractive anode materials for potassium-ion batteries (KIBs) due to their high theoretical capacities based on conversion and alloying reaction. However, the main challenges are the low electronic conductivity, huge volume expansion, and consequent formation of unstable solid electrolyte interphase (SEI) upon potassiation/depotassiation. Herein, zinc sulfide dendrites deeply nested in the tertiary hierarchical structure through a solvothermalpyrolysis process are designed as an anode material for KIBs. The tertiary hierarchical structure is composed of the primary ultrafine ZnS nanorods, the secondary carbon nanosphere, and the tertiary carbon-encapsulated ZnS subunits nanosphere structure. The architectural design of this material provides a stable diffusion path and enhances effective conductivity from the interior to exterior for both K + ions and electrons, buffers the volume expansion, and constructs a stable SEI during cycling. A stable specific capacity of 330 mAh g −1 is achieved after 100 cycles at the current density of 50 mA g −1 and 208 mAh g −1 at 500 mA g −1 over 300 cycles. Using density functional theory calculations, we discover the interactions between ZnS and carbon interface can effectively decrease the K + ions diffusion barrier and therefore promote the reversibility of K + ions storage.
Figure 5. Performance of LED devices of Q-2D perovskite. a) Cross-section scanning electron microscopy (SEM) image of the device; scale bar: 500 nm. b,c) Current-efficiency-voltage (CE-V) curves of the Q-2D perovskite LED devices with different alkali-metal ions incorporated (b) and different amounts of KBr incorporated (c). d) J-V-L-EQE curves of the champion device with 0.5KBr added. e) Histogram of maximum EQE measured from 50 devices with 0.5KBr added. f) Stability of the perovskite LED measured at a constant current density of 0.25 mA cm -2 , with an initial luminance around 140 cd m -2 .
high-performance LEDs due to high photoluminescence (PL) quantum efficiency, narrow emission linewidth (i.e., high color purity), and low density of sub-gap electronic trap states.  Significant breakthroughs have been achieved in perovskite LEDs (PeLEDs) in the past 5 years, with the external quantum efficiency (EQE) boosted from 0.76% in 2014 to over 21% recently, [1,10,11] comparable to the stateof-the-art performance of organic LEDs (OLEDs).  Nevertheless, despite rapid development of electroluminescence (EL) efficiency, the commercialization of PeLEDs is still challenging due to the poor device stability,  which mainly stems from degradation of perovskite materials upon air exposure or electrical bias. As demonstrated in perovskite-based photovoltaic (PV) devices, migration of mobile ions under electrical bias stress causes destruction of the perovskite lattices and infiltration of mobile ions into adjacent layers. [14,15] In PeLEDs, a higher electricfield is present and may aggravate the ion migration issue. In particular, in contrast to the thick perovskite absorber layer in PV devices, the perovskite light-emitting layer in PeLEDs is much thinner (typically a few tens of nanometers) as required for spatial confinement of charge carriers and efficient radiative recombination.  Therefore, mobile ions in the thin perovskite layer would be
The poor stability of perovskite light-emitting diodes (PeLEDs) is a key bottleneck that hinders commercialization of this technology. Here, the degradation process of formamidinium lead iodide (FAPbI 3 )-based PeLEDs is carefully investigated and the device stability is improved through binary-alkalication incorporation. Using time-of-flight secondary-ion mass spectrometry, it is found that the degradation of FAPbI 3 -based PeLEDs during operation is directly associated with ion migration, and incorporation of binary alkali cations, i.e., Cs+ and Rb + , in FAPbI 3 can suppress ion migration and significantly enhance the lifetime of PeLEDs. Combining experimental and theoretical approaches, it is further revealed that Cs + and Rb + ions stabilize the perovskite films by locating at different lattice positions, with Cs + ions present relatively uniformly throughout the bulk perovskite, while Rb + ions are found preferentially on the surface and grain boundaries. Further chemical bonding analysis shows that both Cs + and Rb + ions raise the net atomic charge of the surrounding I anions, leading to stronger Coulomb interactions between the cations and the inorganic framework. As a result, the Cs + -Rb + -incorporated PeLEDs exhibit an external quantum efficiency of 15.84%, the highest among alkali cation-incorporated FAPbI 3 devices. More importantly, the PeLEDs show significantly enhanced operation stability, achieving a half-lifetime over 3600 min.In recent years, solution-processed metal halide perovskites have attracted tremendous interests in the scientific community including the field of light-emitting diodes (LEDs).  Besides low fab...
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