1,721,240 research outputs found
A Special Issue on Plasma Processing of Nanomaterials
No full textPlasma technologies play an important role in the
manufacturing and treatment of materials. Beside the microelectronic industry, where plasma processing is well established for the fabrication of integrated circuits, plasma application is indeed rapidly emerging in many other advanced technological fields ranging from medicine to
waste treatment, from textiles to protective coatings.
This Special Issue focuses on various key aspects
of plasma processing of nanomaterials. Joining together experimental and theoretical viewpoints, the authors’ contributions clearly highlight how unique plasma-related properties are translated into specific material characteristics (electrical, mechanical, magnetic, optical, thermal and
chemical). Taken together, the papers included in this Special Issue demonstrate the potential of the plasma environment to develop a library of assorted nanomaterials with exciting functional performances and technological utilizations
CVD Cu2O and CuO nanosystems characterized by XPS
No full textIn the present investigation, X-ray photoelectron and X-ray excited Auger electron spectroscopy
analyses of the principal core levels (O 1s, Cu 2p, and Cu LMM) of Cu2O and CuO nanosystems
are proposed. The samples were obtained by chemical vapor deposition starting from a novel
second-generation copper(II) precursor, Cu(hfa)2·TMEDA (hfa1,1,1,5,5,5-hexafluoro-
2,4-pentanedionate; TMEDA=N,N,N’,N’- tetramethylethylenediamine), under a dry O2
atmosphere. The obtained route led to pure, homogeneous and single-phase Cu(I) and Cu(II) oxide
nanosystems at temperatures of 300 and 500 °C, respectively, whose chemical nature could be
conveniently distinguished by analyzing the Cu 2p band shape and position, as well as by evaluating
the Auger parameters. The samples were characterized by O/Cu atomic ratios greater than the
expected stoichiometric values, due to marked interactions with the outer atmosphere attributed to
their high surface-to-volume ratio
Dalla ruggine ai materiali funzionali avanzati: la nanoscienza per la salute e l’ambiente
No full textDal punto di vista dello sviluppo di una "chimica verde", la sostituzione
di materie prime rare e costose, con altre più economiche e a basso
impatto ambientale rappresenta una scelta preferenziale per la
salvaguardia dell'ambiente e della salute umana
Gold nanotubes by template-directed synthesis
No full textGold nanotubes were prepared by radiofrequency-sputtering through a template-directed synthesis
in porous alumina substrates. The resulting composite material was subsequently treated in acidic
or alkaline aqueous solutions in order to selectively remove the membrane, thus resulting in the
obtainment of self-supporting Au nanotubules. The adopted strategy allows the preparation of both
composites and free-standing metal nanostructures with an aspect ratio tunable as a function of
the synthesis conditions and the membrane pore size
Special Issue on 'CVD and Hydrogen'
No full textThis Special Issue has
tried to cover various key aspects in the
field of ‘CVD and hydrogen’, drawing
together both experimental and theoretical
viewpoints. The present research
activities are likely to fuel further
advances in hydrogen production, utilization,
and detection by using supported
films and nanomaterials with
specific features. In addition, it is hoped
that these articles will also pave the way
to further advanced applications of
CVD-related techniques in ‘CVD and
hydrogen’ fields, regarding, in particular,
low-temperature growth in plasmaassisted
routes, still scarcely present in
the depicted scenario
Ag/ZnO Nanocomposites Studied by X-ray Photoelectron Spectroscopy
No full textAg/ZnO nanocomposites were prepared on Si(100) substrates by an innovative approach consisting of the deposition of ZnO host matrices by Plasma Enhanced-Chemical Vapor Deposition (PE-CVD) and the subsequent dispersion of Ag guest particles by Radio Frequency (RF)-sputtering. In particular, ZnO nanostructures were synthesised from Ar-O2 plasmas using a Zn(II) bis(ketoiminate) precursor at 300 °C and 1.0 mbar, with an RF-power of 20 W.
Subsequently, Ag was sputtered on the obtained systems under mild conditions (Ar, total pressure=0.3 mbar; substrate temperature=60 °C; RF-power=5 W). The structural,
morphological and compositional features of the obtained nanosystems were analysed by Glancing
Incidence X-ray Diffraction (GIXRD), Field Emission-Scanning Electron Microscopy (FE-SEM)
and Energy Dispersive X-ray Spectroscopy (EDXS). To attain a detailed insight into the chemical
characteristics of the Ag/ZnO nanocomposites, this contribution is devoted to the investigation of a
representative specimen by X-ray Photoelectron (XPS) and X-ray Excited Auger Electron (XEAES)
Spectroscopies. In particular, the attention is focused on the analysis of the O 1s, Zn 2p3/2, Zn
3p and Ag 3d core levels, as well as zinc and silver Auger signals. The results highlight an
appreciable silver surface oxidation and an electronic interplay between Ag/Ag2O and ZnO phases
Multi-component oxide nanosystems by Chemical Vapor Deposition and related routes: challenges and perspectives
No full textMulti-component oxide-based nanosystems are of primary technological importance for various applications of current interest, spanning from optoelectronics to catalysis, from chemical sensing to energy conversion and storage. Such a broad range of functional utilizations results from the joint features of nano-organized systems and the synergistic combination of constituent properties, which, in turn, can be tailored by means of flexible and scalable preparative strategies. An amenable synthetic option potentially meeting these standards is Chemical Vapor Deposition (CVD), either as such or in combination with other fabrication routes. To this regard, the present highlight provides an overview on the CVD-based growth and applicative potential of oxide-based nanocomposite systems. Special attention is devoted to three different categories, i.e. metal/oxide, oxide/oxide and carbon/oxide nanomaterials. For each of them, selected results on synthesis/applications of composite architectures with tailored morphology are presented, trying to address actual challenges and future trends in the field
CVD of nanosized ZnS and CdS thin films from single-source precursors
No full textA chemical vapor deposition (CVD) route to nanosized ZnS and CdS thin films was developed. The layers were deposited on SiO2 substrates in a N2 atmosphere at temperatures between 473 and 723 K using M(O-iPrXan)2 [M =Zn,Cd; O-iPrXan = S2COCH(CH3)2] as single-source precursors. Thermal decomposition and fragmentation of M(O-iPrXan)2 compounds were investigated by thermal analyses and mass spectrometry. The sulfide films were thoroughly characterized in their composition, nanostructure, and morphology by means of several analytical techniques. Surface and in-depth chemical composition was studied
by X-ray photoelectron spectroscopy, X-ray excited Auger electron spectroscopy, and secondary ion mass spectrometry. Film
nanostructure and surface topography were investigated as a function of the synthesis conditions by glancing incidence X-ray diffraction and atomic force microscopy, respectively. Optical absorption properties were also studied. Nanophasic and contaminant-free ZnS and CdS thin films with an average crystallite size lower than 25 nm were obtained. The layers mainly contained the hexagonal (alpha) sulfide phase and displayed a smooth and regular surface morphology. In the present work, the influence of synthesis conditions on film characteristics is analyzed and discussed
Silica-supported Ag-Au bimetallic nanosystems by XPS
No full textBimetallic Ag-Au/SiO2 nanosystems were synthesized by sequential deposition of Au and Ag on
silica substrates via rf-sputtering. Sample preparation was accomplished at 60 °C from Ar plasmas,
using a constant sputtering time for gold (10 min), followed by silver deposition at different times
(5-20 min) in order to vary the Ag/Au ratio as well as the total metal content. A proper choice of the
synthesis conditions allowed us to obtain a controlled dispersion of silica-supported bimetallic
nanoparticles with tailored size and shape, as evidenced by X-ray Photoelectron Spectroscopy
(XPS), X-ray Excited Auger Electron Spectroscopy (XE-AES), Transmission Electron Microscopy
(TEM), Selected Area Electron Diffraction (SAED), and optical absorption spectroscopy. This work
is devoted to the XPS and XE-AES characterization of a representative Ag-Au/SiO2 specimen with
an average nanoparticle size of 9 +/- 5 nm. In particular, detailed scans for the C 1s, O 1s, Si 2s,
Au 4 f, Ag 3d, and Ag MNN regions and related data are presented and discussed
Silica-sandwiched Au nanoparticle arrays by a soft PE-CVD/RF-sputtering approach
No full textThis work is focused on the development of an innovative synthetic route to SiO2-sandwiched
Au nanoparticle arrays. The adopted strategy consists of: (i) the radio frequency sputtering of
gold on thermally oxidized Si(100) and silica substrates from Ar plasmas; (ii) the plasma
enhanced chemical vapor deposition of a SiO2 overlayer using tetramethoxysilane as precursor
from Ar–O2 plasmas. A common feature of both preparative stages is the use of very soft
processing conditions at temperatures close to room temperature, in order to tailor the Au
nanoparticle morphology and to preserve it upon SiO2 coverage. In situ monitoring of gold
deposition was accomplished by means of laser reflection interferometry. Valuable information
on the system morphology before and after SiO2 coverage was provided by field
emission-scanning electron microscopy for samples with different Au content. Additional
important information on the system chemical composition, structure and optical response was
gained by the combined use of x-ray photoelectron spectroscopy, glancing incidence x-ray
diffraction and UV–visible absorption spectroscopy. The results obtained highlight the
formation of high-purity SiO2/Au/SiO2-sandwiched stacks, in which the gold content and
distribution, as well as the nanoparticle morphology, could be tailored by the sole variation of
the sputtering time, without any further ex situ treatment
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