Latest ArticlesPressure-related sensing materials in mechanochromic luminescent materials have received wide attention. However, at present, most piezochromic luminescence (PCL) materials have problems such as aggregation-caused quenching (ACQ) effect due to the presence of powder form, complicated preparation methods and fluorescence quenching effect under high pressure. To solve these problems, we employ three components containing carbon dots (CDs), layered double hydroxides (LDHs) and polyvinyl alcohol (PVA) to construct the CDs-LDHs/PVA film. The LDHs can provide a rigid environment for CDs and improve the luminescent efficiency of CDs. The film shows high sensitivity, stability and reversibility. Moreover, the compressed film can recover to its original state by heating. Therefore, the PCL film with dual emission (fluorescence and phosphorescence) characteristic is constructed, which boosts the sensitivity of pressure-sensing.
Gold nanoparticles (Au NPs) are nanoscale sources of light and electrons, which are highly relevant for their extensive applications in the field of photocatalysis. Although a number of research works have been carried out on chemical reactions accelerated by the energetic hot electrons/holes, the possibility of reaction pathway change on the plasmonic Au surfaces has not been reported so far. In this proof-of-concept study, we find that Au NPs change the reaction pathway in photooxidation of alkyne under visible light irradiation. This reaction produces benzil (-CO-CO-) without the presence of Au NPs. In contrast, as indicated by surface-enhanced Raman spectroscopic (SERS) results, the C-C triple bonds (-C≡C-) adsorbed on Au NPs are converted into carboxyl (-COOH) and acyl chloride (-COCl) groups. The plasmonic Au NPs not only provide energetic charge carriers but also activate the reactant molecules as conventional heterogeneous catalysts. This study discloses the second role of plasmonic NPs in photocatalysis and bridges the gap between plasmon-driven and conventional heterogeneous catalysis.
We report herein a palladium-catalyzed diarylative dearomatization of indole by employing thioester and arylboronic acid as the aryl electrophiles. The reaction involved a decarbonylation/migratory insertion/terminal Suzuki coupling procedure. Substrates bearing various functional groups are well tolerated in the reaction, affording the diarylated indoline skeletons in moderate to good yields.
Density functional theory calculations have been performed to investigate the dipeptide phosphine-catalyzed hydroamination of enones with pyridazinones. The computations reveal that a number of the NH···O hydrogen-bonding interactions with the pyridazinone moiety and the C-H···O hydrogen-bonding interactions with the enone moiety are present in the enantioselectivity-determining Michael addition transition states. The experimentally-observed catalyst-controlled enantiodivergence is mainly attributed to the significant impact of the substituent of the amide moiety of the dipeptide phosphine on the relative strength of the NH···O hydrogen-bonding interactions, which was found to affect the Si face attack transition state, enabling the enantioselectivity switch upon change of chiral dipeptide phosphine catalyst.
To achieve an efficient photocatalytic for clean energy production and environmental remediation, the highly active Fe-doped and terephthalaldehyde-modified carbon nitride (Fe-CN/NTE) isotypic heterojunction photocatalyst is constructed via a simple annealing method for degradation of organic pollutants with simultaneous resource recovery. The Fe-CN/NTE catalyst exhibits a 93% removal rate of p-nitrophenol (4-NP) and a 1.72 mmol/g H2 evolution rate in 2 h simultaneously under visible light irradiation, which are higher than those of pristine CN, Fe-CN, and NTE, respectively. Photoelectrochemical tests show that the excellent photocatalytic performance of Fe-CN/NTE comes from the improved migration, transportation, and separation of photoinduced charge carriers and expanded light-harvesting range. Moreover, hydroxyl radical (OH), electron (e−), and hole (h+) are the main active species and the rational mechanism of 4-NP photodegradation was proposed based on scavenger measurements and liquid chromatography-mass spectrometry (LC-MS), respectively. Isotypic heterojunction Fe-CN/NTE photocatalyst possesses excellent stability in the H2 evolution and 4-NP degradation during five-run cycle tests, posing as a promising candidate in practical works for organic pollution and energy challenges.
We report a Pd-catalyzed halocyclization of unactivated 1, 6-diynes with N-bromosuccinimide (NBS). This approach produces stereo-defined dibromo substituted dihydropyrans, tetrahydropyridines, and 3-methylene cyclohexenes with exocyclic double bond appendages in mostly good yields. Copper salt was found to be a useful Lewis acid in this reaction. Mechanistically, a formal anti-carbopalladation and a bromide radical promoted PdII-PdIII-PdI-PdII catalytic cycles were proposed to be involved in the formation of the dibromo-substituted products. Further functionalization of the dihydropyran derivatives underwent B(C6F5)3-catalyzed ring opening, and reduction afforded dibrominated 1, 3-dienes with excellent stereoselectivity.
Carbon dots (CDs) have opened up a new field of carbon nanomaterials and successively attracted increasing attention since their discovery in 2004. Owing to their ultrasmall size, tunable surface functional groups, excellent dispersibility, attractive stability, low toxicity, environmental friendliness, facile synthesis and low-cost precursors, CDs have been developed as green and promising friction-reducing and anti-wear materials in lubrication science, applied to energy conservation and extension of mechanical service life in recent years. However, there are few reviews focusing on the application of CDs in the important field of lubrication. In this review, we comprehensively summarize the development of CDs in lubrication for the first time. Firstly, three strategies for structural engineering design of CDs to improve their tribological characteristics are fully analyzed, in terms of size and shape control, surface modification and heteroatom doping. Secondly, the advance in lubrication application of CDs, including CDs as additives for lubricants, greases, gel and magnetorheological fluids as well as CDs as lubricating coatings, is systematically highlighted. Thirdly, the lubricating mechanisms of CDs as additives are introduced in detail. Furthermore, the remaining major challenges and opportunities for CDs in lubrication field are discussed and outlined.
The silicon-based materials are promising candidates for lithium-ion batteries owing to their high energy density. However, achieving long lifespan under realistic conditions remains a challenge because of the volume expansion and low conductivity. In this work, the highly elastic cobweb-like composite materials consisted by SiO and nanofibers are designed and fabricated for high-efficient lithium storage by ball-milling & ; electrostatic spinning method. The reconstructed heterostructure and highly elastic nanofibers can simultaneously increase the conductivity and inhibit the "expansion effect" of silicon-based materials. The constructed electrode of n-SiO/CNF delivers an initial capacity of 1700 mAh/g, and maintains the capacities over 1000 mAh/g after 100 cycles at the current density of 500 mA/g. Meanwhile, this electrode can give an initial coulombic efficiency over 85% and maintains at 98% in the following charge/discharge processes. Furthermore, it exhibits efficient long-term electrochemical performance, maintaining the capacity at about 1000 mAh/g at a high current density of 1000 mA/g after 1000 cycles. This work could provide a promising strategy for enhancing the performance of silicon-based composite materials for practical application in lithium-ion batteries.
We report the fabrication of highly ordered Nb2O5 nanochannel film (Nb2O5-NCF) onto niobium foil by an anodization method. After thermal treatment, the obtained Nb2O5-NCF with rich oxygen vacancies exhibits electrochemical N2 reduction reaction (NRR) activity with an NH3 yield rate of 2.52×10−10 mol cm-2 s-1 and a faradaic efficiency of 9.81% at −0.4 V (vs. RHE) in 0.1 mol/L Na2SO4 electrolyte (pH 3.2). During electrocatalytic NRR, the Nb2O5-NCF takes place electrochromism (EC), along with a crystalline phase transformation from pseudo hexagonal phase to hexagonal phase owing to H+ insertion. This results in the reduced NRR activity due to the decrease of oxygen vacancies of hexagonal phase Nb2O5, which can be readily regenerated by low-temperature thermal treatment or applying an anodic potential, showing superior recycling reproducibility.
Supramolecular assemblies constructed through the encapsulation of conductive polymers (CPs) by macrocyclic molecules have attracted increasing interest in the fields of supramolecular chemistry and electrochemistry. In this work, an effective strategy was reported to improve the stability and conductivity of CPs by electrochemically constructing different supramolecular assemblies composed of macrocycles and CPs. Typically, we uploaded zinc-based MOF (ZIF-8) onto carbon nanotube film (CNTF) and further electrically deposited macrocycles and CPs to gain the flexible conductive electrodes. Herein, five different supramolecular macrocycles, including α-cyclodextrin (α-CD), sulfato-β-cyclodextrin (SCD), sulfonatocalix[4]arene (SC[4]), cucurbit[6]uril (CB[6]) and cucurbit[7]uril (CB[7]) were utilized and the electrochemical performances of the assembly electrodes increased in an order of α-CD < SCD < SC[4] < CB[6] < CB[7], significantly improving the areal capacitance up to 1533 mF/cm2. This strategy may provide a new way for the application of macrocyclic supramolecules in electrochemical systems.
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