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Two types of zeolite catalysts, namely, nanosized Beta-N and micrometer-sized Beta-M, were used to crack low-density polyethylene (LDPE) with three different molecular weights: 4000, 200,000, and 3,000,000. The structural and acidic properties were analyzed by N 2 physisorption, transmission electron microscopy, X-ray diffraction, temperature-programmed desorption of isopropylamine (IPA-TPD), and pyridine-adsorbed FTIR. The catalytic activity was tested at 623 K and 3.5 N 2 MPa in an autoclave batch reactor for PE cracking. High Mw PE required higher decomposition activation energy due to transfer limitation. Beta-N showed better activity in PE cracking than Beta-M, with PE conversion of 82.7 and 62.0% for Beta-N and Beta-M, respectively. In addition, the nanosized Beta-N exhibited quite lower activation energy of catalytic PE decomposition than Beta-M, obtained by the Kissinger method in TGA measurement. The characterization results demonstrated that the Beta-N has abundant interparticulate mesopores to provide better dispersion for the catalysts into PE melt and the proximity of the cracking active sites. These results revealed that the Beta-N catalyst shows superior activity for the cracking of polyolefins., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Self-assembly of CuX 2 (X - = BF 4 - , PF 6 - , and SbF 6 - ) with a pair of chiral bidentate ligands, (1 R, 2 S )-(+)- and (1 S, 2 R )-(-)-1-(nicotinamido)-2,3-dihydro-1 H -inden-2-yl-nicotinate ( r,s -L or s,r -L), in a mixture solvent including ethanol in a glass vessel gives rise to SiF 6 2- -encapsulated Cu 2 L 4 chiral cage products. The SiF 6 2- anion from the reaction of X - with SiO 2 of the glass-vessel surface acts as a cage template or cage bridge. One of the products, [SiF 6 @Cu 2 (SiF 6 )( s,r -L) 4 ]·3CHCl 3 ·4EtOH, is one of the most effective heterogeneous catalysts for the oxidation of 3,5-di- tert -butylcatechol. Furthermore, an l -DOPA/ d -DOPA pair is recognizable by the cyclic voltammetry (CV) signals of its combination with chiral cages [SiF 6 @Cu 2 (BF 4 ) 2 ( s,r - or r , s -L) 4 ]·4CHCl 3 ·2EtOH pair and [SiF 6 @Cu 2 (SiF 6 )( s,r - or r,s -L) 4 ]·3CHCl 3 ·4EtOH pair., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Although the particle phase state is an important property, there is scant information on it, especially, for real-world aerosols. To explore the phase state of fine mode aerosols (PM 2.5 ) in two megacities, Seoul and Beijing, we collected PM 2.5 filter samples daily from Dec 2020 to Jan 2021. Using optical microscopy combined with the poke-and-flow technique, the phase states of the bulk of PM 2.5 as a function of relative humidity (RH) were determined and compared to the ambient RH ranges in the two cities. PM 2.5 was found to be liquid to semisolid in Seoul but mostly semisolid to solid in Beijing. The liquid state was dominant on polluted days, while a semisolid state was dominant on clean days in Seoul. These findings can be explained by the aerosol liquid water content related to the chemical compositions of the aerosols at ambient RH; the water content of PM 2.5 was much higher in Seoul than in Beijing. Furthermore, the overall phase states of PM 2.5 observed in Seoul and Beijing were interrelated with the particle size distribution. The results of this study aid in a better understanding of the fundamental physical properties of aerosols and in examining how these are linked to PM 2.5 in polluted urban atmospheres.

Ever since the discovery of carbon nanotubes (CNTs), it has long been a challenging goal to create macroscopically ordered assemblies, or crystals, of CNTs that preserve the one-dimensional quantum properties of individual CNTs on a macroscopic scale. Recently, a simple and well-controlled method was reported for producing wafer-scale crystalline films of highly aligned and densely packed CNTs through spontaneous global alignment that occurs during vacuum filtration ( Nat. Nanotechnol . 2016 , 11 , 633). However, a full understanding of the mechanism of such global alignment has not been achieved. Here, we report results of a series of systematic experiments that demonstrate that the CNT alignment direction can be controlled by the surface morphology of the filter membrane used in the vacuum filtration process. More specifically, we found that the direction of parallel grooves pre-existing on the surface of the filter membrane dictates the direction of the resulting CNT alignment. Furthermore, we intentionally imprinted periodically spaced parallel grooves on a filter membrane using a diffraction grating, which successfully defined the direction of the global alignment of CNTs in a precise and reproducible manner. These results are promising not only for developing novel devices based on macroscopically aligned CNTs but also for understanding the microscopic physical mechanism of the alignment process.