126 research outputs found
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
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
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
One-step growth and shaping by a dual plasma reactor of diamond nanocones arrays for the assembling of stable cold cathodes
Arrays of conical-shaped nanodiamond structures are formed on silicon substrate by a single-step CVD process from CH4/H-2 mixtures. The formation of these nanocones has been found to depend on interplay between growing and etching during the CVD process carried out in a dual-mode MW/RF plasma reactor. Morphology and structure of the conical-like systems can be controlled by varying the process parameters, and have been investigated by scanning electron microscopy (SEM), reflection high energy electron diffraction (RHEED) and micro-Raman spectroscopy. The Field Emission (FE) properties of different diamond nanocones arrays have been investigated and compared with those of analogous systems in order to assess the feasibility of the present nano-materials as electron emitters for cold cathodes. The FE behavior is discussed taking into account the structure of the different diamond nanocones
Nanocarbon surfaces for biomedicine
The distinctive physicochemical, mechanical and electrical
properties of carbon nanostructures are currently gaining
the interest of researchers working in bioengineering and
biomedical fields. Carbon nanotubes, carbon dendrimers, graphenic
platelets and nanodiamonds are deeply studied aiming
at their application in several areas of biology and medicine.
Here we provide a summary of the carbon nanomaterials
prepared in our labs and of the fabrication techniques used to
produce several biomedical utilities, from scaffolds for tissue
growth to cargos for drug delivery and to biosensors
CVD-based techniques for the synthesis of nanographites and nanodiamonds
We report about some Chemical Vapor Deposition approaches used
to produce a variety of C-sp2 and C-sp3 crystalline nanostructures. The methodologies
developed in our laboratories provide custom-made solutions for the fabrication
of specific carbon nanomaterials with properties tailored for applications in the field
of nanotechnology
An innovative and viable routre for the realization of ultra-thin supercapacitor electrodes assembled with carbon nanotubes
Electrochemical Double Layer Capacitors (EDLC), also known as supercapacitors, have been fabricated
using Single Walled Carbon Nanotubes (SWCNTs) as active material for electrode assembling.
In particular a new way of fabrication of ultra-thin electrodes (≤25 m) directly formed on the
separator has been proposed, and a prototype of EDLC has been realized and tested. For such
devices the specific capacitance is in the range 40–45 F/g and the internal resistances in the range
6–8 ·cm2, at current density of 2 mA·cm−2.
Keywords: Carbon Nanotube, Supercapacito
Detonation nanodiamonds tailor the structural oeder of PEDOT chains in conductive coating layers of hybrid nanoparticles
Solid layers of PEDOT–detonation nanodiamond based nanoparticles with an exceptional structural order
were produced by means of a template-free polymerization technique. As an efficient multifunctional filler,
the nanocrystalline diamond has been shown to possess a high catalytic activity on the monomer
polymerization rate as well as to play a fundamental role as a 3D arrangement-directing agent of the
PEDOT chains at the micro- and nano-scale. SEM, TEM and TED analyses highlighted the mutual
organization between PEDOT oligomers and nanodiamond grains, and the produced hierarchical effects
on the arrangement of the backbones of the final polymer. Optical and Raman spectroscopy, used
together with XRD diffraction to study the molecular structure and crystallographic features of the hybrid
materials, pointed out that the adopted synthetic strategy enables highly conjugated and doped hybrid
systems to be generated. The spatial distribution of the filler inside the polymeric matrix and the mutual
connectivity of nanodiamond crystals and PEDOT segments are found to strongly improve the functional
properties of the host polymer. Mechanical characterizations by advanced AFM-based techniques
revealed that both indentation modulus and hardness of PEDOT/nanodiamond materials are 3 times
higher than the pure PEDOT polymer, while electrical characterizations by a 4-probe method gave sheet
resistance values of 1 106 U sq 1 for the nanocomposite particle
Macroscopic self standing SWCNT fibers as efficient electron emitters with very high emission current for robust cold cathodes
A novel of self-standing nanotube-based cold cathode is described. The electron emitter is
a single macroscopic fibre spun from neat single wall carbon nanotubes and consists of an
ensemble of nanotube bundles held together by van der Waals forces. Field emission measurements
carried out using two different types of apparatus demonstrated the long working
life of the realised cathode. The system is able to emit at very high current densities, up
to 13 A/cm2, and shows very low values of both turn on and threshold field, 0.12 V/lm and
0.21 V/lm, respectively. Such easy to handle self-standing electron sources assure good
performances and represent an enabling technology for a scalable production of cold
cathodes.
2012 Elsevier Ltd. All rights reserved.
1. Introduction
Due to a unique combination of properties, including high
electrical and thermal conductivity, and high mechanical/
chemical/thermal stability, carbon nanotubes (CNTs) have
been recognised as ideal candidate materials for application
in microelectronics [1]. Moreover, the high aspect ratio characterising
this intriguing material makes possible to significantly
strengthen electric fields into the vicinity of
nanotubes tips
- …