Abundant heterointerfaces in MOF-derived hollow CoS_(2)-MoS_(2) nanosheet array electrocatalysts for overall water splitting

Rational coupling of hydrogen evolution reaction(HER) and oxygen evolution reaction(OER) catalysts is extremely important for practical overall water splitting,but it is still challenging to construct such bifunctional heterostructures.Herein,we present a metal-organic framework(MOF)-etching strategy to design free-standing and hierarchical hollow CoS_(2)-MoS_(2) heteronanosheet arrays for both HER and OER.Resulting from the controllable etching of MOF by MoO_(4)^(2-) and in-situ sulfuration,the obtained CoS_(2)-MoS_(2) possesses abundant heterointerfaces with modulated local charge distribution,which promote water dissociation and rapid electrocatalytic kinetics.Moreover,the two-dimensional hollow array architecture can not only afford rich surface-active sites,but also facilitate the penetration of electrolytes and the release of evolved H_(2)/O_(2) bubbles.Consequently,the engineered CoS_(2)-MoS_(2) heterostructure exhibits small overpotentials of 82 mV for HER and 266 mV for OER at 10 mA cm^(-2).The corresponding alkaline electrolyzer affords a cell voltage of 1.56 V at 10 mA cm^(-2) to boost overall water splitting,along with robust durability over 24 h, even surpassing the benchmark electrode couple composed of IrO_(2) and Pt/C The present work may provide valuable insights for developing MOF-derived heterogeneous electrocatalysts with tailored interface/surface structure for widespread application in catalysis and other energyrelated areas.

Modeling the gene delivery process of the needle array-based tissue nanotransfection

Hollow needle array-based tissue nanotransfection(TNT)presents an in vivo transfection approach that directly translocate exogeneous genes to target tissues by using electric pulses.In this work,the gene delivery process of TNT was simulated and experimentally validated.We adopted the asymptotic method and cell-array-based model to investigate the electroporation behaviors of cells within the skin structure.The distribution of nonuniform electric field across the skin results in various electroporation behavior for each cell.Cells underneath the hollow microchannels of the needle exhibited the highest total pore numbers compared to others due to the stronger localized electric field.The percentage of electroporated cells within the skin structure,with pore radius over 10 nm,increases from 25%to 82%as the applied voltage increases from 100 to 150 V/mm.Furthermore,the gene delivery behavior across the skin tissue was investigated through the multilayer-stack-based model.The delivery distance increased nonlinearly as the applied voltage and pulse number increased,which mainly depends on the diffusion characteristics and electric conductivity of each layer.It was also found that the skin is required to be exfoliated prior to the TNT procedure to enhance the delivery depth.This work provides the foundation for transition from the study of murine skin to translation use in large animals and human settings.

Supramolecular Bonding Competition Enabled Nanostructure Evolution and Mechanical Reinforcement

In this work,competition between different supramolecular interactions is investigated based on a fibrous crystal composed of hydrogen-bonded cyanuric acid(CA)and amidinothiourea(ADT).Melamine(M)is found to prevail over ADT and bond to CA due to its stronger triple H-bonding affiliation,forming hollow microtubes assembled by oriented CAM crystalline arrays,as guided by the directionality of peripheral hydrogen bonds.Furthermore,competitive interaction between hydrogen bonding and ionic/covalent bonding is demonstrated by mixing Ag+ions with the CA-ADT fibers,where sulfur atoms are abstracted from ADT molecules to produce Ag_(2)S ligaments.The in situ-formed Ag_(2)S serves as a binding glue to generate CA-ADT/Ag_(2)S composites with significantly enhanced mechanical strength compared to the pristine CA-ADT fiber pellet.