Claudia Altavilla

Multiwalled carbon nanotube films as small-sized temperature sensors

We present the fabrication of thick and dense carbon nanotube networks in the form of freestanding films (CNTFs) and the study of their electric resistance as a function of the temperature, from 4 to 420 K. A nonmetallic behavior with a monotonic R(T) and a temperature coefficient of resistance around −7×10−4 K−1 is generally observed. A behavioral accordance of the CNTF conductance with the temperature measured by a solid-state thermistor (ZnNO, Si, or Pt) is demonstrated, suggesting the possibility of using CNTFs as temperature small-sized (freely scalable) sensors, besides being confirmed by a wide range of sensitivity, fast response, and good stability and durability. Concerning electric behavior, we also underline that a transition from nonmetal to metal slightly below 273 K has been rarely observed. A model involving regions of highly anisotropic metallic conduction separated by tunneling barrier regions can explain the nonmetallic to metallic crossover based on the competing mechanisms of the metal...

New 'chimie douce' approach to the synthesis of hybrid nanosheets of MoS2 on CNT and their anti-friction and anti-wear properties.

Hybrid organic-inorganic oleylamine@MoS2-CNT nanocomposites with different compositions were obtained by thermal decomposition of tetrathiomolybdate in the presence of oleylamine and high quality multiwalled carbon nanotubes (CNTs) previously prepared by the CCVD technique. The nanocomposite samples were characterized by the TEM, SEM TG-MS, Raman and XRD techniques and successfully tested as anti-friction and anti-wear additives for grease lubricants.

Effect of sequential grafting of magnetic nanoparticles onto metallic and semiconducting carbon-nanotube devices: towards self-assembled multi-dots

We demonstrate that van der Waals interactions can be used to self-assemble a small, controlled number of magnetic nanoparticles onto metallic and semiconducting carbon nanotubes. We study the effect of the sequential grafting on the room temperature transport properties of carbon-nanotube electronic devices containing metallic or semiconducting carbon nanotubes. The results show that the grafting of the nano-objects has different effects on metallic and semiconducting CNTs, with an appreciable effect for single nanoparticle grafting only on field effect transistors. The results indicate that these grafting techniques are suited for the production of multi-quantum dot systems usable at low temperatures. Magnetization measurements of single nano-objects using carbon nanotube-based magnetic sensors, like nano-SQUID devices, also become feasible.

Light irradiation tuning of surface wettability, optical, and electric properties of graphene oxide thin films

In this work the preparation of flexible polymeric films with controlled electrical conductivity, light transmission and surface wettability is reported. A drop casted graphene oxide thin film is photo-reduced at different levels by UV light or laser irradiation. Optical microscopy, IR spectroscopy, electrical characterization, Raman spectroscopy and static water contact angle measurements are used in order to characterize the effects of the various reduction methods. Correlations between the optical, electrical and structural properties are reported and compared to previous literature results. These correlations provide a useful tool for independently tuning the properties of these films for specific applications.

Preliminary investigation of polystyrene/MoS2-Oleylamine polymer composite for potential application as low-dielectric material in microelectronics

Insulating materials play a vital role in the design and performance of electrical systems for both steady and transient state conditions. Among the other properties, also in this field, polymer nanocomposites promise to offer exciting improvements. Many studies in the last decade has witnessed significant developments in the area of nano-dielectric materials and significant effects of nano-scale fillers on electric, thermal and mechanical properties of polymeric materials have been observed. However, the developments of new and advanced materials to be used the miniaturization of electronic devices fabrication require extensive studies on electrical insulation characteristics of these materials before they can be used in commercial systems. In this work, Polystyrene (PS) composites were prepared by the blend solution method using MoS2@Oleylamine nanosheets as filler. The dielectric properties of the resulting comoposite have been investigated at 300K and in the frequency range between 1000 Hz and 1 MHz. ...

Real time radiation dosimeters based on vertically aligned multiwall carbon nanotubes and graphene

Measurements of the absorbed dose and quality assurance programs play an important role in radiotherapy. Ionization chambers (CIs) are considered the most important dosimeters for their high accuracy, practicality and reliability, allowing absolute dose measurements. However, they have a relative large physical size, which limits their spatial resolution, and require a high bias voltage to achieve an acceptable collection of charges, excluding their use for in vivo dosimetry. In this paper, we propose new real time radiation detectors with electrodes based on graphene or vertically aligned multiwall carbon nanotubes (MWCNTs). We have investigated their charge collection efficiency and compared their performance with electrodes made of a conventional material. Moreover, in order to highlight the effect of nanocarbons, reference radiation detectors were also tested. The proposed dosimeters display an excellent linear response to dose and collect more charge than reference ones at a standard bias voltage, permitting the construction of miniaturized CIs. Moreover, an MWCNT based CI gives the best charge collection efficiency and it enables working also to lower bias voltages and zero volts, allowing in vivo applications. Graphene based CIs show better performance with respect to reference dosimeters at a standard bias voltage. However, at decreasing bias voltage the charge collection efficiency becomes worse if compared to a reference detector, likely due to graphenes semiconducting behavior.

Polystyrene/MoS2@oleylamine nanocomposites

The effects of adding different concentrations of MoS2@oleylamine nano particles on the thermal and mechanical properties of polystyrene (PS) nanocomposites have been investigated. X-ray diffraction and optical microscopy were used to characterize the morphology of the resulting nanocomposites. The thermal stability of the nanocomposites has been characterized by thermogravimetric analysis. It has been found that the MoS2@oleylamine nanoparticles have a good compatibility with the PS matrix forming homogeneous dispersion even at high concentrations. The PS/MoS2@oleylamine nanocomposites showed enhanced thermal stability in comparison with neat polystyrene.