[Show abstract][Hide abstract] ABSTRACT: A simple and fast microwave-assisted
hydrothermal method is proposed for the synthesis
of magnetite nanoparticles. The addition of different
surfactants (polyvinylpyrrolidone, oleic acid, or trisodium
citrate) was studied to investigate the effect on
size distribution, morphology, and functionalization of
the magnetite nanoparticles. Microwave irradiation at
150 �C for 2 h of aqueous ferrous chloride and
hydrazine without additives resulted in hexagonal
magnetite nanoplatelets with a facet-to-facet distance
of 116 nm and a thickness of 40 nm having a
saturation magnetization of *65 Am2 kg-1. The use
of polyvinylpyrrolidone led to hexagonal nanoparticles
with a facet-to-facet distance of 120 nm and a
thickness of 53 nm with a saturation magnetization of
*54 Am2 kg-1. Additives such as oleic acid and
trisodium citrate yielded quasi-spherical nanoparticles
of 25 nm in size with a saturation magnetization of
*70 Am2 kg-1 and spheroidal nanoparticles of 60 nm
in size with a saturation magnetization up to
*82 Am2 kg-1, respectively. A kinetic control of the
crystal growth is believed to be responsible for the
hexagonal habit of the nanoparticles obtained without
additive. Conversely, a thermodynamic control of the
crystal growth, leading to spheroidal nanoparticles, seems
to occur when additives which strongly interact with the
nanoparticle surface are used. A thorough characterization
of the materials was performed. Magnetic properties
were investigated by Superconducting Quantum Interference
Device and Vibrating Sample magnetometers.
Based on the observed magnetic properties, themagnetite
obtained using citrate appears to be a promising support
for magnetically transportable catalysts
Journal of Nanoparticle Research 10/2015; 17(10):408. DOI:10.1007/s11051-015-3213-0 · 2.18 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Multiwalled carbon nanotube (MWCNT)-based gas sensors were decorated by an electrophoretic deposition of electrochemically preformed gold nanoparticles (Au NPs) with controlled size and loading, for the detection of gaseous pollutants at sub-ppm concentrations and operating temperature in the range of 100–200°C. The effects of the tailored Au content on the sensitivity and selectivity of MWCNT-based gas sensors were evaluated towards the NO2 monitoring, and also towards some interfering reducing gases, such as NH3 and H2S. Gas sensing measurement revealed the highest NO2 response up to sub-ppm level by using MWCNTs functionalized by the lowest Au content; instead, the worse NO2 response was obtained by modified MWNTs containing the highest Au loading. Moreover, the control of the deposited gold loading has allowed to control the MWCNT sensing response; specifically the increase of gold content on MWCNT has reduced the selectivity and sensitivity towards NO2 gas, and, on the contrary, at the same time it has improved those towards H2S and NH3 interfering gases. Finally, binary gas mixtures (NO2/H2S and NO2/NH3)
were performed to evaluate the detection of the targeted NO2 gas, simulating possible real-world conditions.
Sensors and Actuators B Chemical 09/2015; 223:414. DOI:10.1016/j.snb.2015.09.112 · 4.10 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Silicon nanowires prepared by wet etching and decorated by metal nanoparticles enable interference-free laser desorption-ionization mass spectrometry of low-molecular-weight analytes.
[Show abstract][Hide abstract] ABSTRACT: Metal oxides (MOx) and noble metal modified MOx are a well-known sensing material for the detection of pollutants of automotive and environmental interest such as nitrogen oxides (NOx). [1-3] ZnO is considered a promising and versatile sensing material for solid-state semiconductor gas sensors because of the excellent sensitivity and selectivity figures of merit. In this contribution, nanostructured ZnO powders, synthesized by sol-gel method and properly desiccated, were electro-decorated by Au and Pd nanoparticles (NPs) using an in-situ process. Metal NPs/MOx nanocomposites were then thermally annealed and subjected to a morphological and chemical characterization using transmission and scanning electron microscopies (TEM, SEM), as well as X-ray photon electron spectroscopy (XPS). Upon annealing, electro-decorated NP/ZnO powders were converted into ZnO nanorods whose surface was decorated by nanoscale gold or palladium retaining its spheroidal morphology. Surface chemical speciation of the catalytic nanophases was assessed by XPS and outlined the presence of elemental states even after the thermal treatment. The resulting nanocomposites could be finally used as active layers in chemiresistive gas sensors showing promising selectivity towards NOx species.
 Q. Xiang, G. Meng, Y. Zhang, J. Xu, P. Xu, Q. Pan, W. Yu, Sens. Act. B 143 (2010) 635-640
 A. Afzal, N. Cioffi, L. Sabbatini, L. Torsi, Sens. Act. B 171-172 (2012) 25-42.
 M. Penza, C. Martucci, G. Cassano, Sens. Act. B 50 (1998) 52-59.
 A. Afzal, C. Di Franco, E. Mesto, N. Ditaranto, N. Cioffi, F. Scordari, G. Scamarcio, L. Torsi, Mater. Express 5 (2015) 171-179.
XXV Congresso Nazionale di Chimica Analitica, Trieste; 09/2015
[Show abstract][Hide abstract] ABSTRACT: Abstract
Ternary CuxSnySz thin films with different Cu/Sn atomic ratios and thicknesses have been electrochemically deposited on the (111) face of a silver single crystal. The surface morphology and chemical composition of these chalcogenides, which have attracted considerable worldwide interest as low cost high conversion efficiency photovoltaic devices, have been characterized by means of SEM, parallel angle resolved (PAR-XPS) and TOF-SIMS depth profiling in order to gain insight into the morphology and element distribution within the layer and their effect on the band gap.
This study constitutes the first in-depth chemical study on CuxSnySz thin films, providing evidence of notable discrepancies between the expected and real composition, especially regarding the Cu/Sn ratio. The samples were found to be chemically homogeneous through the whole deposit even though strongly tin depleted regardless their thickness or deposition sequence. Finally, the literature band gap data were discussed on the basis of these findings.
Solar Energy Materials and Solar Cells 07/2015; 138:9-16. DOI:10.1016/j.solmat.2015.02.029 · 5.34 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: ZnO nanoparticles have been prepared via a green electrochemical synthesis method in the presence of a polymeric anionic stabilizer (poly-sodium-4-styrenesulfonate, PSS), and then applied as inorganic component in poly-3-hexyl-thiophene thin-film transistor active layers. Different parameters (i.e. current density, electrolytic media, PSS concentration, and temperature) influencing nanoparticle synthesis have been studied. The resulting nanomaterials have been investigated by transmission electron microscopy (TEM) and spectroscopic techniques (UV-Vis, infrared, and x-ray photoelectron spectroscopies), assessing the most suitable conditions for the synthesis and thermal annealing of nanostructured ZnO. The proposed ZnO nanoparticles have been successfully coupled with a poly-3-hexyl-thiophene thin-film resulting in thin-film transistors with improved performance.
[Show abstract][Hide abstract] ABSTRACT: A SEM, DRS and XAS study was carried out on ultra-thin films with chemical composition belonging to the Cu-Zn-S ternary system, related to the kesterite-type materials, in the light of their potential application to thin film photovoltaic technology. The films, realized through the layer-by-layer E-ALD electrochemical technique, reveal variable phase composition as a function of the applied E-ALD sequence. In particular, by increasing the Zn cycles per Cu cycle from 1:1 to 9:1, the number of detected phases changes from 3 to 2. In all samples, Cu mainly crystallize in a Cu 2 S type phase, whereas Zn occurs as ZnS. In the 1:1 sample, additional ZnO is detected. The variable phase composition parallels apparent changes in the sample morphology. In all samples, a sulphide thin film is covered by a net of elongated nanostructures, the length of which decreases with increasing the number of Zn cycles per Cu cycle. All these evidences are interpreted as due to the operating electrochemical route during the synthesis and confirm the lack of miscibility between Cu 2 S and ZnS, thermodynamically relevant after the E-ALD has stopped. The band gap values exhibited by the three films, modulated by changing the copper:zinc ratio, progressively approach a value useful for solar energy conversion, thus strongly proposing these new sulfide nanomaterials for photovoltaics and photochemical applications.
[Show abstract][Hide abstract] ABSTRACT: Ultrasensitive biosensors based on bottom gate organic field-effect transistors can be developed by depositing a functional biological (protein) interlayer directly on the silicon oxide gate dielectric and underneath the organic semiconductor film. However, the deposition methods for assembling the protein biological recognition layer can affect the biosensor analytical performances for the target analyte detection. Here, spin-coating and layer-by-layer techniques were considered as different approaches for streptavidin protein deposition. X-ray photoelectron spectroscopy (XPS) was systematically used in the non-destructive parallel angle resolved mode to characterize the multilayer device at each step of its assembly to gain information on elemental depth profiles. Scanning electron and scanning Helium ion microscopies gave information about stacked layer structure and morphology corroborating XPS results.
[Show abstract][Hide abstract] ABSTRACT: Copper(II) chloride catalyses the oxidative carbonylation of aminols, amine and alcohols to give 2-oxazolidinones, ureas and carbamates. Reaction proceeds smoothly in water under homogeneous conditions (Ptot= 4 MPa; PO2 = 0.6 MPa, PCO), at 100 °C in relatively short reaction times (4 h) and without using bases or any other additives. This methodology represents an economic and environmentally benign non-phosgene alternative for the preparation of these three important N-containing carbonyl compounds.
Journal of Molecular Catalysis A Chemical 06/2015; DOI:10.1016/j.molcata.2015.06.007 · 3.62 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: ZnO based thin-film transistors are very promising to be used as electronic biosensors due to their very good electronic performances and inherent biocompatibility. Herein, we report on the use of a solution processed ZnO water gated thin-film transistor (WG-TFT) whose channel surface is bio-functionalized with a streptavidin protein layer. This is a very critical process as it endows the device with bio-recognition capabilities. The bio-functionalization process is carried out by attaching an organosilane self-assembled monolayer to the ZnO surface that is coupled to the biomolecule afterwards. A systematic X-Ray Photoelectron Spectroscopy surface characterization allows assessing that the immobilization of the streptavidin proteins on the ZnO surface has been successfully accomplished. Upon deposition of the protein layer, a decrease in the ZnO WG-TFT source-drain current is observed. Such an occurrence is ascribable to the electrostatic effect of the negatively charged protein molecules lying on the ZnO semiconductor layer in contact with the transistor 2D-channel. The deposited streptavidin layer can be prospectively further used for the immobilization and orientation of biotinylated recognition elements in view of the use of ZnO TFTs as electronic biosensors for real-life applications.
Advances in Sensors and Interfaces (IWASI), 2015 6th IEEE International Workshop on; 06/2015
[Show abstract][Hide abstract] ABSTRACT: Automobile exhaust gas emissions are causing serious damage to urban air quality in and around major cities of the world, which demands continuous monitoring of exhaust emissions. The chief components of automobile exhaust include carbon monoxide (CO), nitrogen oxides (NOx), and hydrocarbons. Indium zirconate (InZrOx) and gold/indium zirconate (Au/InZrOx) composite nanopowders are believed to be interesting materials to detect these substances. To this end, characterization and gas sensing properties of InZrOx and Au/InZrOx composite nanopowders are discussed. InZrOx nanoparticles with In/Zr atomic ratio of 1.00 (±0.05) are synthesized via pH-controlled co-precipitation of In and Zr salts in aqueous ammonia. Gold (Au) nanoparticles are subsequently deposited on InZrOx using an in situ sacrificial Au electrolysis procedure. The products are characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The gas sensing performance of Au/InZrOx composite nanopowder is studied by depositing a thick powder film on interdigitated electrode structures patterned on SiC substrate to facilitate high temperature operation. The resistivity of the Au/InZrOx layer is the sensor signal, and the sensors could be operated at 500-600 °C, which is a suitable temperature range for engine exhaust measurements. The control sensing measurements reveal that Au/InZrOx composite nanopowder exhibits higher response towards 2-20 % O2 gas as compared to pristine InZrOx nanoparticles. Further studies show that when applied to exhaust gases such as CO and nitric oxide (NO), the response of Au/InZrOx sensors is significantly higher towards NO in this temperature range. Thus, sensor performance characteristics of Au/InZrOx composite nanopowder are promising in terms of their applications in automobile exhaust emission control.
Journal of Solid State Electrochemistry 06/2015; 19(9). DOI:10.1007/s10008-015-2900-1 · 2.45 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Gold nanoparticles stabilized on metal oxide supports have found a wide range of applications especially in heterogeneous catalysis and gas sensing. A facile methodology for the in situ electrodecoration of gold nanoparticles on metal oxide supports is presented herein. Metal oxides such as indium oxide (In2O3) and zirconia (ZrO2) nanoparticles are first prepared via the sol–gel route. Subsequently, gold nanoparticles are electrodeposited in situ on the surface of these metal oxides using a modified sacrificial Au-anode electrolysis procedure. Both pristine as well as electrodecorated metal oxides are characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning and transmission electron microscopies (SEM, TEM). SEM images of electrodecorated metal oxides reveal successful deposition of gold nanoparticles on metal oxide supports. XPS shows that nano-sized gold is significantly available on the materials' surface and it is in the elemental oxidation state. Moreover, it is found that the electrodecoration of gold nanoparticles on metal oxide surfaces proceeds as a function of the concentration of hydroxyl groups on the surface of metal oxide supports.
[Show abstract][Hide abstract] ABSTRACT: Designing bioactive materials, with controlled metal ion release, exerting significant bioactivity and associated low toxicity for humans, is nowadays one of the most important challenges for the scientific community. In this work, we propose a new material combining the well-known antimicrobial properties of copper nanoparticles (CuNPs) with those of bioactive chitosan (CS), a cheap natural polymer widely exploited for its biodegradability and nontoxicity. Here, we used ultrafast femtosecond laser pulses to finely fragment, via laser ablation, a Cu solid target immersed into aqueous CS solutions. Homogeneously dispersed copper-chitosan (Cu-CS) colloids were obtained by tuning the Cu/CS molar ratios, according to the initial chitosan concentration, as well as other experimental parameters. Cu-CS colloids were characterized by several techniques, like UV-Vis and X-ray Photoelectron spectroscopies (XPS). Transmission Electron Microscopy (TEM) was used to morphologically characterize the novel nanocomposites.
[Show abstract][Hide abstract] ABSTRACT: Controlled amounts of colloidal Au nanoparticles (NPs), electrochemically pre-synthesized, were directly deposited on MWCNTs sensor devices by electrophoresis. Pristine and Au-functionalized MWCNT networked films were tested as active layers in resistive gas sensors for detection of pollutant gases. Au-modified CNT-chemiresistor demonstrated higher sensitivity to NO
detecting up to sub-ppm level compared to pristine one. The investigation of the cross-sensitivity towards other pollutant gases revealed the decrease of the sensitivity to NO
with the increase of Au content, and, on the other side, the increase of that to H
S; therefore the fine tune of the metal loading on CNTs has allowed to control not only the gas sensitivity but also the selectivity towards a specific gaseous analyte. Finally, the sensing properties of Au-decorated CNT sensor seem to be promising in environmental and automotive gas sensing applications, based on low power consumption and moderate operating temperature.