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Studying the mechanism of binder is important for improving the coating formation process of solid lubricants. Two-component polyurethane (PU), polyvinyl butyral (PVB), and styrene-butadiene styrene (SBS) copolymer were selected as binders for polytetrafluoroethylene (PTFE) solid lubricant. The influence of solid lubricant coating prepared with different binders on the stamping properties of 6061-T6 aluminum alloy was compared and analyzed using the cupping test. A lubrication model was developed based on the results. Due to the difference in the molecular structure of the binders, the prepared solid lubricants have different characteristics and affect the dispersion of lubricant coating and its performance. When the content of PTFE reaches 15 wt% and the coating thickness is 10 µm, the anodic aluminum alloy sheet with PVB coating has the smallest punch force. [ABSTRACT FROM AUTHOR]

In this work, the spectroscopic properties of surface functionalized nanodiamond particles are investigated via Fourier transform infrared spectroscopy. The functionalization of the nanodiamond surface was achieved chemically using strong acid treatment method. The size dependent C==O stretching frequency (between 1680 and 1820 cm-1) are studied for particle diameter sizes from the 5 to 500 nm range. The surface C==O stretching frequencies at ∼1820 cm-1, for large particle size (500 nm), down shifted to 1725 cm-1 (5 nm) with decreasing particle sizes. We attributed the shift as a result of hydrogen bond formation between the COOH groups in the carboxylated nanodiamond surfaces. Particle size was characterized with dynamic light scattering method and surface morphology of the particles was investigated with scanning electron microscopy. The influence of pH value on C==O stretching frequency is also analyzed. This finding affords useful information for the studying of surface functionalized nanodiamonds with implications for their interaction with biomolecules. [ABSTRACT FROM AUTHOR]

Recent developments in the technology of van der Waals heterostructures made from two-dimensional atomic crystals have already led to the observation of new physical phenomena, such as the metal-insulator transition and Coulomb drag, and to the realization of functional devices, such as tunnel diodes, tunnel transistors and photovoltaic sensors. An unprecedented degree of control of the electronic properties is available not only by means of the selection of materials in the stack, but also through the additional fine-tuning achievable by adjusting the built-in strain and relative orientation of the component layers. Here we demonstrate how careful alignment of the crystallographic orientation of two graphene electrodes separated by a layer of hexagonal boron nitride in a transistor device can achieve resonant tunnelling with conservation of electron energy, momentum and, potentially, chirality. We show how the resonance peak and negative differential conductance in the device characteristics induce a tunable radiofrequency oscillatory current that has potential for future high-frequency technology. [ABSTRACT FROM AUTHOR]

Self-similarity and fractals have fascinated researchers across various disciplines. In graphene placed on boron nitride and subjected to a magnetic field, self-similarity appears in the form of numerous replicas of the original Dirac spectrum, and their quantization gives rise to a fractal pattern of Landau levels, referred to as the Hofstadter butterfly. Here we employ capacitance spectroscopy to probe directly the density of states (DoS) and energy gaps in this spectrum. Without a magnetic field, replica spectra are seen as pronounced DoS minima surrounded by van Hove singularities. The Hofstadter butterfly shows up as recurring Landau fan diagrams in high fields. Electron-electron interactions add another twist to the self-similar behaviour. We observe suppression of quantum Hall ferromagnetism, a reverse Stoner transition at commensurable fluxes and additional ferromagnetism within replica spectra. The strength and variety of the interaction effects indicate a large playground to study many-body physics in fractal Dirac systems. [ABSTRACT FROM AUTHOR]

This letter presents direct observation of growth hormone receptor in one single cancer cell using nanodiamond-growth hormone complex as a specific probe. The interaction of surface growth hormone receptor of A549 human lung epithelial cells with growth hormone was observed using nanodiamond’s unique spectroscopic signal via confocal Raman mapping. The growth hormone molecules were covalent conjugated to 100 nm diameter carboxylated nanodiamonds, which can be recognized specifically by the growth hormone receptors of A549 cell. The Raman spectroscopic signal of diamond provides direct and in vitro observation of growth hormone receptors in physiology condition in a single cell level. [ABSTRACT FROM AUTHOR]

A correction to the article "Hierarchy of Hofstadter states and replica quantum Hall ferromagnetism in graphene superlattices," that was published in the June 1, 2014 issue is presented.

Abstract: Nano-scale materials with attached biomolecules on the surface can be used as bioprobes in cell and tissue analysis. The conjugation of these nanoparticles with biomolecules is one of the key steps in the development of bioprobes. In this work nanometer-sized diamonds (5 and 100 nm) are functionalized and conjugated with protein lysozyme via physical adsorption. The process of creating functional groups on the nanodiamond surface is studied using Fourier Transform Infrared-spectroscopy (FTIR). The conjugation of nanodiamonds with biomolecules and nanodiamond–biomolecule interaction are analyzed with UV/VIS and FTIR spectroscopy. [Copyright &y& Elsevier]

Functionalisation of two-dimensional (2-D) materials via low energy ion implantation could open possibilities for fabrication of devices based on such materials. Nanoscale patterning and/or electronically doping can thus be achieved, compatible with large scale integrated semiconductor technologies. Using atomic resolution High Angle Annular Dark Field (HAADF) scanning transmission electron microscopy supported by image simulation, we show that sites and chemical nature of individual implants/ dopants in graphene, as well as impurities in hBN, can uniquely and directly be identified on grounds of their position and their image intensity in accordance with predictions from Z-contrast theories. Dopants in graphene (e.g., N) are predominantly substitutional. In other 2-Ds, e.g. dichalcogenides, the situation is more complicated since implants can be embedded in different layers and substitute for different elements. Possible configurations of Se-implants in MoS 2 are discussed and image contrast calculations performed. Implants substituting for S in the top or bottom layer can undoubtedly be identified. We show, for the first time, using HAADF contrast measurement that successful Se-integration into MoS 2 can be achieved via ion implantation, and we demonstrate the possibility of HAADF image contrast measurements for identifying impurities and dopants introduced into in 2-Ds. [ABSTRACT FROM AUTHOR]

Abstract: The surface properties of nanodiamonds play a decisive role in many nanodiamond applications, particularly in bio- and medical applications. The surface functional groups largely determine the interactions and conjugations between nanodiamonds and biomolecules. In this work, the spectroscopic properties of surface-carboxylated nanodiamonds with an average diameter of 100 nm are investigated, focusing on the temperature dependence of the surface Cing frequency. The Cing frequency was found to be sensitive to temperature. Observed water molecules from temperature desorption confirmed that the Cing frequency shifts were associated with the formation of hydrogen bonds. Other molecules were also observed during the temperature treatments, associated with desorption of loosely bonded surface atoms. This work provides useful information on the surface group interactions for nanodiamond applications in nanobiotechnology. [Copyright &y& Elsevier]

Hexagonal boron nitride is the only substrate that has so far allowed graphene devices exhibiting micrometer-scale ballistic transport. Can other atomically flat crystals be used as substrates for making quality graphene heterostructures? Here we report on our search for alternative substrates. The devices fabricated by encapsulating graphene with molybdenum or tungsten disulfides and hBN are found to exhibit consistently high carrier mobilities of about 60 000 cm(2) V(-1) s(-1). In contrast, encapsulation with atomically flat layered oxides such as mica, bismuth strontium calcium copper oxide, and vanadium pentoxide results in exceptionally low quality of graphene devices with mobilities of ∼1000 cm(2) V(-1) s(-1). We attribute the difference mainly to self-cleansing that takes place at interfaces between graphene, hBN, and transition metal dichalcogenides. Surface contamination assembles into large pockets allowing the rest of the interface to become atomically clean. The cleansing process does not occur for graphene on atomically flat oxide substrates.