Surface micro/nanostructure evolution of Au-Ag alloy nanoplates： Synthesis, simulation, plasmonic photothermal and surface-enhanced Raman scattering applications

This study reports the controllable surface roughening of Au-Ag alloy nanoplates via the galvanic replacement reaction between single-crystalline triangular Ag nanoplates and HAuC14 in an aqueous medium. With a combination of experimental evidence and finite element method （FEM） simulations, improved electromagnetic field （E-field） enhancement around the surface-roughened Au- Ag nanoplates and tunable light absorption in the near-infrared （NIR） region （-800-1,400 nm） are achieved by the synergistic effects of the localized surface plasmon resonance （LSPR） from the maintained triangular shape, the controllable Au-Ag alloy composition, and the increased surface roughness. The NIR light extinction enables an active photothermal effect as well as a high photothermal conversion efficiency （78.5%）. The well-maintained triangular shape, surface- roughened evolutions of both micro- and nanostructures, and tunable NIR surface plasmon resonance effect enable potential applications of the Au-Ag alloy nanoplates in surface-enhanced Raman spectroscopic detection of biomolecules through 785-nm laser excitation.

Core@shell sub-ten-nanometer noble metal nanoparticles with a controllable thin Pt shell and their catalytic activity towards oxygen reduction

Reducing Pt loading, while improving electrocatalytic activity and the stability of Pt-based nanostructured materials, is currently a key challenge in green energy technology. Herein, we report the controllable synthesis of tri-metallic （Au@Ag@Pt） and bimetallic （Ag@Pt） particles consisting of a controllable thin Pt shell, via interface-mediated galvanic displacement. Through oil-ethanol-H2O interface mediation, the controllable ＂out to in＂ displacement of Ag atoms to Pt enables the formation of a thin Pt shell on monodisperse sub-ten-nanometer Au@Ag and Ag nanocrystals. The synthesized nanoparticles with a thin Pt shell exhibited potential catalytic activity towards the oxygen reduction reaction （ORR） due to the high exposure of Pt atoms.

A study of the initial adhesive force of cells on silk fibroin-based materials using micropipette aspiration

With the development of biomaterials,more attention is paid to the adhesion characteristics between cells and materials.It is necessary to study the adhesive force with a suitable method.Silk fibroin(SF)is widely investigated in biomedical application due to its novel biocompatibility and mechanical properties.In this article,the micropipette aspiration method and measurement pattern of uniform cells in round shape(UCR)was used to study the initial adhesive force of three types of cells on pure silk fibroin films(SFFs).We also compared the adhesive forces of modified SFFs with that of pure SFFs.The results of adhesive force in the initial adhesive stage were in concordance with the results of MTT assay andmicroscope observation,which were confirmed by the above three cell lines and four kinds of SFFs.The results indicated UCR was an efficient and quantitative measurement pattern in initial adhesion stage.This article also provides a useful method in identifying initial cell-materials interactions.

Hierarchical charge distribution controls self-assembly process of silk in vitro

Silk materials with different nanostructures have been developed without the understanding of the inherent transformation mechanism. Here we attempt to reveal the conversion road of the various nanostructures and determine the critical regulating factors. The regulating conversion processes influenced by a hierarchical charge distribution were investigated, showing different transformations between molecules, nanoparticles and nanofibers. Various repulsion and compressive forces existed among silk fibroin molecules and aggregates due to the exterior and interior distribution of charge, which further controlled their aggregating and deaggregating behaviors and finally formed nanofibers with different sizes. Synergistic action derived from molecular mobility and concentrations could also tune the assembly process and final nanostructures, it is suggested that the complicated silk fibroin assembly processes comply a same rule based on charge distribution, offering a promising way to develop silk-based materials with designed nanostructures.