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Medical protective masks with both high antibacterial activity and filtration efficiency have gained wide interest due to sporadic respiratory disease outbreaks. Previous studies have focused on improving a single function (antibacterial activity or filtration) of the mask performance. Herein, we developed silver nanoparticles-decorated PVDF membranes (AgNPs/PVDF) with both high antibacterial activity and filtration efficiency. Our results show that AgNPs/PVDF membranes have antibacterial efficiency of 99.98% and 99.86% against E. coli and S. aureus , respectively. The bacterial filtration efficiency is higher than 95%. PM0.26 filtration efficiency can be maintained above 95% after continuous filtration for 144 min. Adding AgNPs also promotes distinct hierarchical structure formation, which could improveme the filtration efficiency. This study provides a new methodology to fabricate antibacterial membranes doped with metal nanoparticles with promising applications in personal protective equipment development. [ABSTRACT FROM AUTHOR]

The influence of the supporting electrolyte concentration on the steady-state voltammetric behavior of a 12.5-[[micro]meter]radius rotating Pt disk electrode (angular velocity, [Omega] = 0-378 rad/s) has been investigated for several electrochemical reactions in acetonitrile solutions. The results demonstrate that the voltammetric response is a strong function of the ratio of the supporting electrolyte and redox concentrations ([C.sub.elec]/[C.sub.redox]) as well as the charge of the reactant (z). For the oxidation or reduction of monovalent and divalent species (e.g., [(trimethylammonio)methyl]-ferrocene (z = +1) and methyiviologen (z = +2)), the observed voltammetric limiting currents are found to increase linearly with [[Omega].sup.1/2], independent of [C.sub.elec]/[C.sub.redox]. Voltammetric currents corresponding to the oxidation or reduction of neutral reactants (e.g., ferrocene and ni-trobenzene (z = 0)) show a more complex dependence on [C.sub.elec]/[C.sub.redox]. In solutions containing an appreciable quantity of supporting electrolyte, [C.sub.elec]/[C.sub.redox] > 0.1, mass transport limited currents are found to increase linearly with [[Omega].sub.1/2]. However, for [C.sub.elec]/[C.sub.redox] < 0.1, the voltam-metric currents decrease with increasing [Omega]. The unusual behavior observed for neutral species in low ionic strength solution is interpreted in terms of the rate of migration of charge-balancing electrolyte ions to the electrode surface, relative to the rate of removal of the same ions by forced convection. In low ionic strength solutions, electrolyte ions are removed by forced convection more rapidly than they are replenished by migration, resulting in a decrease in the electrical driving force for electron transfer.

Steady-state voltammetric currents for Fe[[(CN).sub.6].sup.4-] oxidation and Fe[[(CN).sub.6].sup.3-] reduction in 0.2 M KCl solutions are shown to be a function of the orientation of Au and Pt microdisk electrodes (radius = 6.4-25 [[micro]meter]) with respect to the gravitational field. The observed angular dependencies for the Fe[[(CN).sub.6].sup.3-/4-] couple are in agreement with theoretical expectations based on electrochemically generated fluid density gradients within the depletion layer. The results demonstrate that steady-state voltammetric currents measured at microelectrodes result from both diffusional and natural convection mass transfer fluxes. At 25-[[micro]meter]-radius microdisks, natural convection accounts for between 2 and 15% of the total current for redox concentrations between 10 and 500 mM, respectively. The contribution of mass transfer due to natural convection is shown to decrease rapidly with decreasing electrode size.

A study was done on redox-induced molecular transformations using atomic-resolution scanning tunneling microscopy. Results have shown three distinct interfacial states of zerovalent iodine. These consist of the adlayers formed below the iodide oxidation potential, the polyiodide strings propagating along the surface and the multilayer iodine/polyiodide films. Au(111) plays a central role in the substrate symmetry of the three adlayers.

Arranging atoms in an orderly manner at the atomic scale to create stable polyatomic structures is a very challenging task. In this study, we have developed three-dimensional confinement areas on the two-dimensional surface by creating regional defects. These areas are composed of vertically stacked graphene layers, where Ni and Fe atoms are anchored concentrically to form axial dual atomic sites in high yield. These sites can be used to produce tunable syngas through the electroreduction of CO 2 . Theoretical calculations indicate that the Ni sites vertically regulate the charge distribution of the adjacent Fe sites in the layer below, resulting in a lower d-band center. This, in turn, weakens the adsorption of the *CO intermediate and inhibits the production of H 2 at the Fe site. Our research presents a novel approach for concentrated creation of dual atomic sites by building a confinement-selective surface.

The spin state of antibonding orbital (e g ) occupancy in LaCoO 3 is recognized as a descriptor for its oxygen electrocatalysis. However, the Co(III) cation in typical LaCoO 3 (LCO) favors low spin state, which is mediocre for absorbing oxygen-containing groups involved in oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), thus hindering its further development in electrocatalysis. Herein, both experimental and theoretical results reveal the enhancement of bifunctional electrocatalytic activity in LaCoO 3 by N doping. More specifically, electron energy loss spectroscopy and superconducting quantum interference devices magnetic analysis demonstrate that the Co(III) cation in N-doped LaCoO 3 (LCON) achieves a moderate e g occupancy (≈1) compared with its low spin state in LaCO 3 . First-principle calculation results reveal that N dopants play a bifunctional role of tuning the spin-state transition of Co(III) cations and increasing the electrical conductivity of LCO. Thus, the optimized LCON exhibits an OER overpotential of 1.69 V at the current density of 50 mA/cm 2 (1.94 V for pristine LCO) and yields an ORR limiting current density of 5.78 mA/cm 2 (4.01 mA/cm 2 for pristine LCO), which offers a new strategy to simultaneously modulate the magnetic and electronic structures of LCO to further enhance its electrocatalytic activity.

The melt-blowing process uses high-speed and high-temperature airflow from the die head to draw polymer melt into micron-sized fibers. In this work, to reduce the diameter of the melt-blowing fibers, three new slot dies have been designed based on the common slot die. With computational fluid dynamics technology, the two-dimensional flow fields from these new types of slot dies were numerically calculated. To verify the validity of the calculation, the simulation data was compared with the experimental data. The numerical result shows that the internal flow stabilizers could increase the velocity peak and the pressure peak on the centerline of the flow field and could reduce the reverse velocity, temperature decay, and maximum value of turbulence intensity near the die head. Compared with the common slot die, the slot dies with cuboid bosses could increase the air velocity and temperature on the spinning line in most areas and reduce the air pressure within 1.5 cm below the die. The slot dies with internal flow stabilizers and cuboid bosses have the optimal flow field performance and would be beneficial to the production of thinner fibers., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)