Controllable synthesis of a large TS-1 catalyst for clean epoxidation of a C=C double bond under mild conditions

Development of a titanium silicalite-1(TS-1)catalyst with good crystallinity and a four-coordinate Ti framework is critical for efficient catalytic oxidation reaction under mild conditions.Herein,a size-controlled TS-1 zeolite(TS-10.1ACh(acetylcholine))was synthesized via steam-assisted crystallization by introducing acetylcholine as a crystal growth modifier in the preparation process,and TS-10.1ACh was also employed in epoxidations of different substrates containing C=C double bonds.The crystalline sizes of the as-synthesized TS-10.1ACh catalysts were controlled with the acetylcholine content,and characterization results showed that the particle sizes of highly crystalline TS-10.1ACh zeolite reached 3.0μm with a good Ti framework.Throughout the synthetic process,the growth rate of the crystals was accelerated by electrostatic interactions between the connected hydroxyl groups of the acetylcholine modifier and the negatively charged skeleton of the pre-zeolites.Furthermore,the TS-10.1ACh catalyst demonstrated maximum catalytic activity,good selectivity and high stability during epoxidation of allyl chloride.Importantly,the TS-10.1ACh catalyst was also highly versatile and effective with different unsaturated substrates.These findings may provide novel,easily separable and large TS-1 catalysts for efficient and clean industrial epoxidations of C=C double bonds.

High Thermoelectric Performance of Cu-Doped PbSe-PbS System Enabled by High-Throughput Experimental Screening

Recent advances in high-throughput(HTP)computational power and machine learning have led to great achievements in exploration of new thermoelectric materials.However,experimental discovery and optimization of thermoelectric materials have long relied on the traditional Edisonian trial and error approach.Herein,we demonstrate that ultrahigh thermoelectric performance in a Cu-doped PbSe-PbS system can be realized by HTP experimental screening and precise property modulation.Combining the HTP experimental technique with transport model analysis,an optimal Se/S ratio showing high thermoelectric performance has been efficiently screened out.Subsequently,based on the screened Se/S ratio,the doping content of Cu has been subtly adjusted to reach the optimum carrier concentration.As a result,an outstanding peak zT~1:6 is achieved at 873 K for a 1.8 at%Cu-doped PbSe_(0.6)S_(0.4) sample,which is the superior value among the n-type Te-free lead chalcogenides.We anticipate that current work will stimulate large-scale unitization of the HTP experimental technique in the thermoelectric field,which can greatly accelerate the research and development of new high-performance thermoelectric materials.

A Note on Obata’s Rigidity Theorem

In this note we present various extensions of Obata’s rigidity theorem concerning the Hessian of a function on a Riemannian manifold.They include general rigidity theorems for the generalized Obata equation,and hyperbolic and Euclidean analogs of Obata’s theorem.Besides analyzing the full rigidity case,we also characterize the geometry and topology of the underlying manifold in more general situations.

High-performance Sb:SnO_2 Compact Thin Film Based on Surfactant-free and Binder-free Sb:Sn_3O_4 Suspension

Surfactant-free and binder-free antimony-doped tin oxide （ATO） transparent conducting thin films were fabricated through spin coating and rapid annealing processes, in which nanosheets were assembled into a compact structure via self-contracting high pressure. The mechanism of this compact thin film for- mation was further proposed and analyzed. The compact ATO thin film had a low root mean square （RMS） roughness of 5.03 nm. This surfactant-free and binder-free compact ATO thin film delivered low resistivity of 3.04 × 10^-2 Ω cm, stable resistivity which only increased 13% after exposing in 65% RH air for half a month, high transmittance of 92.70% at 550 nm, and high band gap energy of 4.07 eV. This effective strategy will provide new insight into the synthesis of low-cost and high-performance compact thin films.

Studying bona fide SARS-CoV-2 biology in a BSL-2 biosafety environment using a split-virus-genome system

Dear Editor,Severe acute respiratory syndrome coronavirus 2(SARSCoV-2)was identified as the pathogen causing the coronavirus disease(COVID-19),which sometimes resulted in fatal pneumonia(Hu et al.,2021).SARS-CoV-2 is a biosafety level 3(BSL-3)pathogen,and the requirement for high containment conditions is a bottleneck for basic research on viral biology.To help general researchers who wish to study SARS-CoV-2 but do not have access to a BSL-3 facility,a system that(1)can mimic the real life cycle of the virus;(2)allows easy genetic manipulation;and(3)shows high biosafety in BSL-2 laboratory is required.