Ag-graphene composite nanosheets (AGCN) with adjustable size and well-controlled densities of Ag nanoparticles (Ag NPs) using Poly(N-vinyl-2-pyrrolidone) (PVP) as a reductant and stabilizer are reported. The obtained AGCN substrate is extremely suitable for surface-enhanced Raman spectroscopy (SERS).

Protein micro-/nanoarrays are becoming increasingly important in systematic approaches for the exploration of protein-protein interactions and dynamic protein networks, so there is a high demand for specific, generic, stable, uniform, and locally addressable protein immobilization on solid supports. Here we present multivalent metal-chelating thiols that are suitable for stable binding of histidine-tagged proteins on biocompatible self-assembled monolayers (SAMs). The architectures and physicochemical properties of these SAMs have been probed by various surface-sensitive techniques such as contact angle goniometry, ellipsometry, and infrared reflection-absorption spectroscopy. The specific molecular organization of proteins and protein complexes was demonstrated by surface plasmon resonance, confocal laser scanning, and atomic force microscopy. In contrast to the mono-NTA/His6 tag interaction, which has major drawbacks because of its low affinity and fast dissociation, drastically improved stability of protein binding by these multivalent chelator surfaces was observed. The immobilized histidine-tagged proteins are uniformly oriented and retain their function. At the same time, proteins can be removed from the chip surface under mild conditions (switchability). This new platform for switchable and oriented immobilization should assist proteome-wide wide analyses of protein-protein interactions as well as structural and single-molecule studies.

Designing and developing active, cost-effective and stable electrocatalysts for hydrogen evolution reaction (HER) are still an ongoing challenge. Herein, we report the synthesis of binary transition metal phosphide (CoxFe1-xP) nanocubes with different Co and Fe ratios through a phosphidation process using metal-organic frameworks (MOFs) as templates. MOF templates contribute well-defined nanocube architectural features after phosphidation, while a suitable phosphidation temperature could allow formation of a crystal structure and maintain the well-defined structure. The incorporation of a binary transition metal results in redistribution of the valence electrons in CoxFe1-xP. The changes imply anionic states of the P and Fe atoms, which act as active sites and thus have stronger electron-donating ability. When CoxFe1-xP nanocubes are employed as electrocatalysts, these characteristic features facilitate the performance of HER. Remarkably, Co0.59Fe0.41P nanocubes prepared at 450 °C afford a current density of 10 mA cm(-2) at a low overpotential of 72 mV in acidic conditions and 92 mV in alkaline conditions. Co0.59Fe0.41P nanocubes also exhibit a small Tafel slope of 52 mV decade(-1) in acidic conditions and 72 mV decade(-1) in alkaline conditions. Moreover, Co0.59Fe0.41P nanocubes show good stability in both acidic and alkaline conditions. Our method produces the highly active HER catalyst based on binary transition metal MOF templates, providing a new avenue for designing excellent electrocatalysts.

A synthetic route to FeP-GS hybrid sheets that show good stability and high electrocatalytic activity for hydrogen evolution reaction is reported. The materials are prepared via thermal phosphidation of pre-synthesized Fe3O4-GS hybrid sheets.

Fluorescent carbon dots (C-dots) are prepared directly via a simple hydrothermal method using bovine serum albumin (BSA) as a carbon source in the presence of surface passivation reagents. The obtained C-dots have low cytotoxicity and good biocompatibility, demonstrating that their features are good for application in cell imaging.Fluorescent semiconductor quantum dots (QDs) have attracted much attention over the past two decades for a variety of purposes and applications, especially in optical imaging agents, electronics, biotechnology, sensors and catalysis due to their high quantum yield and size-tunable fluorescence color. [1][2][3][4][5][6][7] Unfortunately, QDs are commonly synthesized using toxic heavy metals (e.g., cadmium, lead), 8 which limit their widespread use and in vivo biological applications because of potential environmental hazards and long term toxicity concerns. Therefore, considerable efforts have been made to search for environmentally-friendly and low toxicity fluorescent nanomaterials.Recently, fluorescent carbon dots (C-dots) have emerged as the most alternative fluorescent probes to replace traditional QDs. Compared with QDs, C-dots are highly attractive for bioimaging, 9,10 photocatalysis, 11 and light emitting devices 12 because of their chemical stability, biocompatibility, low toxicity and reasonable photoluminescence. 13,14 The C-dots are generally small oxygenous carbon nanoparticles of near spherical geometry with sizes below 10 nm, and they inherently fluoresce in visible upon light excitation. Since they were discovered by Xu et al. while purifying single-walled carbon nanotubes derived from arcdischarge soot, C-dots have been produced via various methods. So far, C-dots can be prepared by two main approaches: top-down and bottom-up routes. 15 Top-down methods consist of laser ablation or electrochemical oxidation of graphite, 16,17 electrochemical treatment of multiwalled carbon nanotubes, 18,19 and chemical oxidation of commercially activated carbon etc. 20 Bottom-up methods consist of microwave pyrolysis of saccharides, 21,22 combustion soot of candles, 23 supported synthetic methods, 24,25 chemical or thermal oxidation of suitable precursors, 26,27 and RSC Advances

Binding of antibodies to their cognate antigens is fundamental for adaptive immunity. Molecular engineering of antibodies for therapeutic and diagnostic purposes emerges to be one of the major technologies in combating many human diseases. Despite its importance, a detailed description of the nanomechanical process of antibody-antigen binding and dissociation on the molecular level is lacking. Here we utilize high-speed atomic force microscopy to examine the dynamics of antibody recognition and uncover a principle; antibodies do not remain stationary on surfaces of regularly spaced epitopes; they rather exhibit 'bipedal' stochastic walking. As monovalent Fab fragments do not move, steric strain is identified as the origin of short-lived bivalent binding. Walking antibodies gather in transient clusters that might serve as docking sites for the complement system and/or phagocytes. Our findings could inspire the rational design of antibodies and multivalent receptors to exploit/inhibit steric strain-induced dynamic effects.

A facile method is proposed for the synthesis of reduced graphene oxide nanosheets (RGONS) and Au nanoparticle-reduced graphene oxide nanosheet (Au-RGONS) hybrid materials, using graphene oxide (GO) as precursor and sodium citrate as reductant and stabilizer. The resulting RGONS and Au-RGONS hybrid materials were characterized by UV-vis spectroscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, atomic force microscopy, transmission electron microscopy, and X-ray diffraction. It was found that the RGONS and Au-RGONS hybrid materials formed stable colloidal dispersions through hydrogen bonds between the residual oxygen-containing functionalities on the surface of RGONS and the hydroxyl/carboxyl groups of sodium citrate. The electrochemical responses of RGONS and Au-RGONS hybrid material-modified glassy carbon electrodes (GCE) to three kinds of biomolecules were investigated, and all of them showed a remarkable increase in electrochemical performance relative to a bare GCE.

Stacking order has strong influence on the coupling between the two layers of twisted bilayer graphene (BLG), which in turn determines its physical properties. Here, we report the investigation of the interlayer coupling of the epitaxially grown singlecrystal 30° twisted BLG on Cu(111) at the atomic scale. The stacking order and morphology of BLG is controlled by a rationally designed two-step growth process, that is, the thermodynamically controlled nucleation and kinetically controlled growth. The crystal structure of the 30°-twisted bilayer graphene (30°-tBLG) is determined to have the quasicrystal like symmetry. The electronic properties and interlayer coupling of the 30-tBLG is investigated using scanning tunneling microscopy (STM) and spectroscopy (STS). The energy-dependent local density of states (DOS) with in-situ electrostatic doping shows that the electronic states in two graphene layers are decoupled near the Dirac point. A linear dispersion originated from the constituent graphene monolayers is discovered with doubled degeneracy.This study contributes to controlled growth of twist-angle-defined BLG, and provides insights of the electronic properties and interlayer coupling in this intriguing system.