Role of local coordination in bimetallic sites for oxygen reduction: A theoretical analysis

Understanding of the oxygen reduction reaction(ORR)mechanism for single atom catalysts is pivotal for the rational design of non-precious metal cathode materials and the commercialization of fuel cells.Herein,a series of non-precious metal electrocatalysts based on nitrogen-doped bimetallic(Fe and Co)carbide were modeled by density functional theory calculations to predict the corresponding reaction pathways.The study elucidated prior oxygen adsorption on the Fe atom in the dual site and the modifier role of Co atoms to tune the electronic structures of Fe.The reaction activity was highly correlated with the bimetallic center and the coordination environment of the adjacent nitrogen.Interestingly,the preadsorption of*OH resulted in the apparent change of metal atoms'electronic states with the d-band center shifting toward the Fermi level,thereby boosting reaction activity.The result should help promote the fundamental understanding of active sites in ORR catalysts and provide an effective approach to the design of highly efficient ORR catalysts on an atomic scale.

The recent development of soft x-ray interference lithography in SSRF

This paper introduces the recent progress in methodologies and their related applications based on the soft x-ray interference lithography beamline in the Shanghai synchrotron radiation facility.Dual-beam,multibeam interference lithography and Talbot lithography have been adopted as basic methods in the beamline.To improve the experimental performance,a precise real-time vibration evaluation system has been established;and the lithography stability has been greatly improved.In order to meet the demands for higher resolution and practical application,novel experimental methods have been developed,such as high-order diffraction interference exposure,high-aspect-ratio and large-area stitching exposure,and parallel direct writing achromatic Talbot lithography.As of now,a 25 nm half-pitch pattern has been obtained;and a cm2 exposure area has been achieved in practical samples.The above methods have been applied to extreme ultraviolet photoresist evaluation,photonic crystal and surface plasmonic effect research,and so on.

Identifying the convergent reaction path from predesigned assembled structures: Dissymmetrical dehalogenation of Br_(2)Py on Ag(111)

On-surface Ullmann coupling has been intensely utilized for the tailor-made fabrication of conjugated frameworks towards molecular electronics, however, reaction mechanisms are still limitedly understood. Herein, we provide a comprehensive elucidation of the surface Ullmann coupling of 2,7-dibromopyrene (Br2Py) on Ag(111) by scanning tunnelling microscopy (STM), X-ray photoelectron spectroscopy (XPS) and density function theory (DFT), and reveal that the Ullmann reaction path is unique regardless of predesigned assembled structures. By manipulating deposition conditions, diverse assembled architectures have been constructed for Br2Py on Ag(111), including the ladder phase, parallel arrangement, hexagonal patterns from monomers or Kagome lattices based on organometallic (OM) dimers. Intriguingly, stepwise annealing leads to an identical reaction diagram for the surface Ullmann coupling from individual assembled structures convergent into the brick-wall-pattern OM dimers first, which is deemed to be a stable phase, and then into elongated OM chains in order and eventually long-range polymers with direct C-C coupling. While the reaction mechanism is demonstrated to be dominated by the metal coordinated and halogen bonding motifs, interestingly, it has also been revealed that surface adatoms and dissociated Br atoms play a crucial role in coupling reactions. In contrast to previous reports demonstrating the manipulation of Ullmann reactions by preassembled strategy, herein, weak intermolecular interaction in assembled nanostructures is immediately suppressed by strong covalent bonding during reactions. Importantly, our report proposes essential insights on fundamental understanding of surface Ullmann coupling towards high-yield surface synthesis.

In-Situ HP-STM and Operando EC-STM Studies of Heterogeneous Catalysis at Interfaces

Heterogeneous catalysis taking place at solid interfaces plays a crucial role not only in industrial chemical production, energy conversion but also in fundamental research. The dynamic evolution of surface morphology and composition requires full understanding especially under realistic reaction conditions. To this end, conventional scanning tunneling microscopy(STM) has been integrated with high pressure cell and electrochemical cell, forming high pressure(HP) STM and electrochemical(EC) STM for the in-situ/operando characterization at solid-gas and solid-liquid interfaces with atomic resolution, respectively. In this review, we attempt to give a brief introduction to the development and working principle of these two techniques and subsequently summarize several representative progresses in recent days. The dynamic changes in active sites, surface reconstruction, absorbates alteration and products formation are directly characterized in a combination with other surface sensitive technologies. The correlation between surface structures and catalytic performance as well as the underlying mechanism can thus be unraveled, which provides insights into the rational design and optimization of catalysts.

Exosomes in bladder cancer:novel biomarkers and targets

Exosomes are nanometer-sized vesicles that contain various types of biologically active components,including proteins,nucleic acids,carbohydrates,and lipids,which vary with the type and physiological state of the cell.In recent years,several studies have showed that exosomes can provide new non-invasive diagnostic and prognostic biomarkers in patients affected by cancers,including bladder cancer(BC),and the lipid bilayer membrane structure makes exosomes as promising delivery vehicles for therapeutic applications.Exosomes have the characteristics of high abundance,high stability,tissue specificity,and wide distribution in body fluids,and are secreted as various types by cells in different states,thereby possessing great potential as biomarkers for BC.Herein,we briefly summarize the functions and roles of exosomes in the occurrence and development of BC and the current progress of research on exosomes in BC,while focusing on potential clinical applications of the diagnosis,treatment,and prognosis of BC.