Nanodiamonds for Field Emission: State of the Art

The aim of this review is to highlight the recent advances and the main remaining challenges related to the issue of electron field emission (FE) from nanodiamonds. The roadmap for FE vacuum microelectronic devices envisages that nanodiamonds could become very important in a short time. The intrinsic properties of the nanodiamond materials indeed meet many of the requirements of cutting-edge technologies and further benefits can be obtained by tailored improvements of processing methodologies. The current strategies used to modulate the morphological and structural features of diamond to produce highly performing emitting systems are reported and discussed. The focus is on the current understanding of the FE process from nanodiamond-based materials and on the major concepts used to improve their performance. A short survey of non-conventional microsized cold cathodes based on nanodiamonds is also reported

Nanotechnologies for cultural heritage: nanodiamond for conservation of papers and parchments

In this paper we report some tests regarding the feasibility of nanodiamond to act as a cleaning/consolidation agent of papers and parchments. We carried out a series of treatments aiming to develop innovative approaches for de-acidification, cleaning and consolidation. Dispersions of nanodiamond have been used as de-acidification agents of ancient papers showing the ability to sensibly reduce the acidity of the paper without using any alkaline base. Similar dispersions have been used for cleaning processes and nanodiamond demonstrated an outstanding capability to clean ancient papers and parchments avoiding the use of any solvent and surfactant. Moreover interesting results were obtained by using nanodiamond as consolidation agent. In particular, artificial aging by UV exposition was appreciably contrasted when samples were preliminarily submitted to a treatment by nanodiamond. This outcome was demonstrated in papers and parchments by Raman spectroscopy analyses that evidenced the property of nanodiamond to be an excellent UV-scavenge

Si/C hybrid nanostructures for Li-ion anodes : am overview

This review article summarizes recent and increasing efforts in the development of novel Li ion cell anode nanomaterials based on the coupling of C with Si. The rationale behind such efforts is based on the fact that the SieC coupling realizes a favourable combination of the two materials properties, such as the high lithiation capacity of Si and the mechanical and conductive properties of C, making Si/C hybrid nanomaterials the ideal candidates for innovative and improved Li-ion anodes. Together with an overview of the methodologies proposed in the last decade for material preparation, a discussion on relationship between organization at the nanoscale of the hybrid Si/C systems and battery performances is given. An emerging indication is that the enhancement of the batteries efficiency in terms of mass capacity, energy density and cycling stability, resides in the ability to arrange Si/C bi-component nanostructures in pre-defined architectures. Starting from the results obtained so far, this paper aims to indicate some emerging directions and to inspire promising routes to optimize fabrication of Si/C nanomaterials and engineering of Li-ion anodes structures. The use of Si/C hybrid nanostructures could represents a viable and effective solution to the foreseen limits of present lithium ion technology. 2013 Published by Elsevier

Effects of Au nanoparticles on photoluminescence emission from Si-vacancy in diamond

We studied the coupling of diamond Si color centers with size-controlled Au nanoparticles obtained by chemical routes. The diamond samples, synthesized by Chemical Vapor Deposition, were polycrystalline films or isolated grains. The plasmonic responses of the Au nanoparticles were found to couple with the Ar+ laser frequency or with the frequency of the Si-defects photoluminescence (PL). When the PL of Si optical centers is resonant with the maximum of the Au extinction spectrum, a threshold behavior and a decrease of the PL band FWHM with increasing laser energy is detected, suggesting the transition from spontaneous to stimulated emission

Characterization of polyaniline-detonation nanodiamond nanocomposite fibers by atomic force microscopy based technique

Polyaniline (PANI) fibers were synthesized in presence of detonantion nanodiamond (DND) particles by precipitation polymerization technique. Morphological, electrical and mechanical characterizations of the obtained PANI/DND nanocomposited have been performed by different either standard or advanced atomic force microscopy (AFM) based techniques. Morphological characterization by tapping mode AFM supplied information about the structure of fibers and ribbons forming the PANI/DND network. An AFM based technique that takes advantage of an experimental configuration specifically devised for the purpose was used to assess the electrical properties of the fibers, in particular to verify their conductivity. Finally, mechanical characterization was carried out synergically using two different and recently proposed AFM based techniques, one based on AFM tapping mode and the other requiring AFM contact mode, which probed the nanocomposited nature of PANI/DND fiber sample down to different depths. © 2013 Elsevier Ltd. All rights reserved

Scanning probe microscopy techniques for mechanical characterization at nanoscale

Three atomic force microscopy (AFM)-based techniques are reviewed that allow one to conduct accurate measurements of mechanical properties of either stiff or compliant materials at a nanometer scale. Atomic force acoustic microscopy, AFM-based depth sensing indentation, and torsional harmonic AFM are briefly described. Examples and results of quantitative characterization of stiff (an ultrathin SeSn film), soft polymeric (polyaniline fibers doped with detonation nanodiamond) and biological (collagen fibers) materials are reported

Exploring the bulk of the BL Lac object population:1. parsec-scale radio structures

Context. The advent of Fermi is changing our understanding on the radio and gamma-ray emission in Active Galactic Nuclei. Contrary to pre-Fermi ideas, BL Lac objects are found to be the most abundant emitters in the gamma-ray band. However, since they are relatively weak radio sources, most of their parsec-scale structure and their multi-frequency properties are poorly understood and/or have not been investigated in a systematically fashion. Aims. Our main goal is to analyze the radio and gamma-ray emission properties of a sample of 42 BL Lacs selected, for the first time in the literature, with no constraint on their radio and gamma-ray flux densities/emission. Methods. Thanks to new Very Long Baseline Array observations at 8 and 15 GHz for the whole sample, we present here fundamental parameters such as radio flux densities, spectral index information, and parsec-scale structure. Moreover, we search for gamma-ray counterparts using data reported in the Second Catalog of Fermi Gamma-ray sources. Results. Parsec-scale radio emission is observed in the majority of the sources at both frequencies. Gamma-ray counterparts are found for 14/42 sources. Conclusions. The comparison between our results in radio and gamma-ray bands points out the presence of a large number of faint BL Lacs showing "non classical" properties such as low source compactness, core dominance, no gamma-ray emission and steep radio spectral indexes. A deeper multiwavelength analysis will be needed.Comment: 19 pages, 6 figures, 6 tables, accepted for publication in A&

Gold nanoparticles on nanodiamond for nanophotonic applications

We present here some recent results of a research focused on the prepn. of detonation nanodiamond/Au nanoparticles hybrid materials. Two different exptl. routes are followed for the decoration of diamond nanoparticles by Au nanoparticles, that are in turn prepd. by an innovative electroless approach. Structure and morphol. at the nanoscale level of the Au-on-nanodiamond deposits have been deeply investigated by electron microscopy (FE-SEM, HR-TEM) and diffraction (XRD) techniques. Optical properties of these systems have been detd. by performing scattering and UV-Vis absorption measurements, and by comparing the exptl. data with simulated extinction spectra. The results highlighted very interesting plasmonic and scattering behaviors, mainly related to the high refractive index of diamond

Scaling relations of cluster elliptical galaxies at z~1.3. Distinguishing luminosity and structural evolution

[Abridged] We studied the size-surface brightness and the size-mass relations of a sample of 16 cluster elliptical galaxies in the mass range 10^{10}-2x10^{11} M_sun which were morphologically selected in the cluster RDCS J0848+4453 at z=1.27. Our aim is to assess whether they have completed their mass growth at their redshift or significant mass and/or size growth can or must take place until z=0 in order to understand whether elliptical galaxies of clusters follow the observed size evolution of passive galaxies. To compare our data with the local universe we considered the Kormendy relation derived from the early-type galaxies of a local Coma Cluster reference sample and the WINGS survey sample. The comparison with the local Kormendy relation shows that the luminosity evolution due to the aging of the stellar content already assembled at z=1.27 brings them on the local relation. Moreover, this stellar content places them on the size-mass relation of the local cluster ellipticals. These results imply that for a given mass, the stellar mass at z~1.3 is distributed within these ellipticals according to the same stellar mass profile of local ellipticals. We find that a pure size evolution, even mild, is ruled out for our galaxies since it would lead them away from both the Kormendy and the size-mass relation. If an evolution of the effective radius takes place, this must be compensated by an increase in the luminosity, hence of the stellar mass of the galaxies, to keep them on the local relations. We show that to follow the Kormendy relation, the stellar mass must increase as the effective radius. However, this mass growth is not sufficient to keep the galaxies on the size-mass relation for the same variation in effective radius. Thus, if we want to preserve the Kormendy relation, we fail to satisfy the size-mass relation and vice versa.Comment: Accepted for publication in A&A, updated to match final journal versio