Synthesis of double-helical snip nanowires for visible-light-driven photocatalytic degradation of dyes

As the first carbon-free double helical semiconductor at an atomic scale,tin phosphide iodide(SnIP)has garnered growing interest due to its high structural flexibility,band gap in the visible spectrum range,and non-toxicity.Herein,we report the chemical vapor transport synthesis of SnIP nanowires(NWs).The photocatalytic activity of SnIP NWs was evaluated through the degradation of two representative toxic dyes,methylene blue(MB)and malachite green(MG),under visible light irradiation(λ>400 nm).These NWs exhibited notable photocatalytic efficiency,achieving degradation rates over 97%for MB and 95%for MG within 100 min of visible light exposure.The degradation data align well with a pseudo-first-order reaction kinetics model for both dyes,with rate constants of 0.0347 and 0.0295 min^(−1).Furthermore,the synthesized catalyst demonstrated exceptional stability and recyclability,maintaining its efficient performance till six duplicate operations cycles.Scavenger testing indicated that holes and OH radicals were the main active species driving the dye’s photodegradation.The unusual photocatalytic efficiency can be attributed to their favorable band gap within the visible spectrum range and unique onedimensional structure.The results demonstrate that the SnIP NWs offer a promising choice for eco-friendly dye photodegradation.

Adaptive-optical 3D microscopy for microfluidic multiphase flows

Measurements based on optical microscopy can be severely impaired if the access exhibits variations of the refractive index.In the case of fluctuating liquid-gas boundaries,refraction introduces dynamical aberrations that increase the measurement uncertainty.This is prevalent at multiphase flows(e.g.droplets,film flows)that occur in many technical applications as for example in coating and cleaning processes and the water management in fuel cells.In this paper,we present a novel approach based on adaptive optics for correcting the dynamical aberrations in real time and thus reducing the measurement uncertainty.The shape of the fluctuating water-air interface is sampled with a reflecting light beam(Fresnel Guide Star)and a Hartmann-Shack sensor which makes it possible to correct its influence with a deformable mirror in a closed loop.Three-dimensional flow measurements are achieved by using a double-helix point spread function.We measure the flow inside a sessile,oscillating 50-μl droplet on an opaque gas diffusion layer for fuel cells and show that the temporally varying refraction at the droplet surface causes a systematic underestimation of the flow field magnitude corresponding to the first droplet eigenmode which plays a major role in their detachment mechanism.We demonstrate that the adaptive optics correction is able to reduce this systematic error.Hence,the adaptive optics system can pave the way to a deeper understanding of water droplet formation and detachment which can help to improve the efficiency of fuels cells.

Investigation into the Formation, Structure, and Evolution of an EF4 Tornado in East China Using a High-Resolution Numerical Simulation

Devastating tornadoes in China have received growing attention in recent years, but little is known about their formation, structure, and evolution on the tornadic scale. Most of these tornadoes develop within the East Asian monsoon regime, in an environment quite different from tornadoes in the U.S. In this study, we used an idealized, highresolution（25-m grid spacing） numerical simulation to investigate the deadly EF4（Enhanced Fujita scale category 4）tornado that occurred on 23 June 2016 and claimed 99 lives in Yancheng, Jiangsu Province. A tornadic supercell developed in the simulation that had striking similarities to radar observations. The violent tornado in Funing County was reproduced, exceeding EF4（74 ms–1）, consistent with the on-site damage survey. It was accompanied by a funnel cloud that extended to the surface, and exhibited a double-helix vorticity structure. The signal of tornado genesis was found first at the cloud base in the pressure perturbation field, and then developed both upward and downward in terms of maximum vertical velocity overlapping with the intense vertical vorticity centers. The tornado＇s demise was found to accompany strong downdrafts overlapping with the intense vorticity centers. One of the interesting findings of this work is that a violent surface vortex was able to be generated and maintained, even though the simulation employed a free-slip lower boundary condition. The success of this simulation, despite using an idealized numerical approach, provides a means to investigate more historical tornadoes in China.

In situ synthesis of FeS/Carbon fibers for the effective removal of Cr(Ⅵ)in aqueous solution

Iron sulfide(FeS)nanoparticles(termed FSNs)have attracted much attention for the removal of pollutants due to their high efficiency and low cost,and because they are environmentally friendly.However,issues of agglomeration,transformation,and the loss of active components limit their application.Therefore,this study investigates in situ synthesized FeS/carbon fibers with an Fecarrageenan biomass as a precursor and nontoxic sulfur source to ascertain the removal efficiency of the fibers.The enrichment of sulfate groups as well as the double-helix structure in i-carrageenan-Fe could effectively avoid the aggregation and loss of FSNs in practical applications.The obtained FeS/carbon fibers were used to control a Cr(Ⅵ)polluted solution,and exhibited a relatively high removal capacity(81.62 mg/g).T he main mechanisms included the reduction of FeS,electrostatic adsorption of carbon fibers,and Cr(Ⅲ)-Fe(Ⅲ)complexation reaction.The pseudo-second-order kinetic model and Langmuir adsorption model both provided a good fit of the reaction process;hence,the removal process was mainly controlled by chemical adsorption,specifically monolayer adsorption on a uniform surface.Furthermore,co-existing anions,column,and regeneration experiments indicated that the FeS/carbon fibers are a promising remediation material for practical application.