Ilaria Armentano

PVA bio-nanocomposites: A new take-off using cellulose nanocrystals and PLGA nanoparticles

The formation of a new generation of hybrid bio-nanocomposites is reported: these are intended at modulating the mechanical, thermal and biocompatibility properties of the poly(vinyl alcohol) (PVA) by the combination of cellulose nanocrystals (CNC) and poly (D,L-lactide-co-glycolide) (PLGA) nanoparticles (NPs) loaded with bovine serum albumin fluorescein isothiocynate conjugate (FITC-BSA). CNC were synthesized from microcrystalline cellulose by hydrolysis, while PLGA nanoparticles were produced by a double emulsion with subsequent solvent evaporation. Firstly, binary bio-nanocomposites with different CNC amounts were developed in order to select the right content of CNC. Next, ternary PVA/CNC/NPs bio-nanocomposites were developed. The addition of CNC increased the elongation properties without compromising the other mechanical responses. Thermal analysis underlined the nucleation effect of the synergic presence of cellulose and nanoparticles. Remarkably, bio-nanocomposite films are suitable to vehiculate biopolymeric nanoparticles to adult bone marrow mesenchymal stem cells successfully, thus representing a new tool for drug delivery strategies.

Investigation of the NO2 sensitivity properties of multiwalled carbon nanotubes prepared by plasma enhanced chemical vapor deposition

In the present work, multiwalled carbon nanotube (MWNT) thin films deposited by plasma enhanced chemical vapor deposition have been investigated as resistive gas sensors towards NO2. The sensor design is a platinum interdigitate electrode, fabricated by photolithography upon Si3N4 deposited on silicon, over which the MWNTs are deposited. Microstructural features as determined by scanning electron, transmission electron, and Raman spectroscopies have highlighted the growth of tubular carbon structures of 20–30 nm diameter and 150–200 nm length. Carbon nanotubes have shown a decreasing of their resistance upon exposure to NO2 gas (10–100 ppb) and the highest sensitivity at 165 °C working temperature. The time evolution of the electrical resistance at 165 °C as the sample was cycled through 500 ppm of NH3, 100 ppm of C6H6, water vapor, and 500 ppm of ethanol gases and dry air has been also reported. The variation of conductance in the presence of oxidizing or reducing gases is explained on the basis of charg...

Ozone adsorption on carbon nanotubes: Ab initio calculations and experiments

The electrical response to O3 of 150-nm-thick carbon nanotube (CNT) thin films prepared by radio frequency-plasma enhanced chemical vapor deposition has been investigated at different operating temperatures starting from the room temperature. The interaction between ozone molecules and a carbon nanotube film is studied by means of first-principles calculations. Experiments show that CNT films are responsive to O3 with a decrease of the resistance similar to that observed for NO2. Our theoretical results suggest the interaction to be pretty strong, as shown by a relatively short equilibrium molecule-tube distance, as well as by an appreciable binding energy and charge transfer from the tube to the adsorbed molecule. The analysis of the density of states shows that a peak in proximity of the nanotube Fermi level is induced by the ozone adsorption. This effect enhances the p-type character of the nanotube and, therefore, the conductivity of the whole film increases, in excellent consistency with the experime...

Enhancement of Photoelectrical Properties in Polymer Nanocomposites Containing Modified Single-walled Carbon Nanotubes by Conducting Dendrimer

We report the photoinduced conductivity changes measured on a system composed of single-wall carbon nanotubes (SWNTs) modified by a semiconducting poly(amidoamine) dendrimer (PAMAMC) characterized by highly aromatic end groups. Under illumination hole injection into SWNTs prevails over the photoinjection of electrons from PAMAMC to SWNT holes, and film photoconductivity is observed. This system was incorporated as an electroactive component within a conducting polymer [poly(3-octylthiophene)], providing improvements in the photoelectrical properties of the composite. Such supramolecular structures consisting of dendrimer-functionalized carbon nanotubes provide the means for an approach toward the preparation of photoactive materials of high current interest.

Functional Properties of Plasticized Bio-Based Poly(Lactic Acid)_Poly(Hydroxybutyrate) (PLA_PHB) Films for Active Food Packaging

Fully bio-based and biodegradable active films based on poly(lactic acid) (PLA) blended with poly(3-hydroxybutyrate) (PHB) and incorporating lactic acid oligomers (OLA) as plasticizers and carvacrol as active agent were extruded and fully characterized in their functional properties for antimicrobial active packaging. PLA_PHB films showed good barrier to water vapor, while the resistance to oxygen diffusion decreased with the addition of OLA and carvacrol. Their overall migration in aqueous food simulant was determined and no significant changes were observed by the addition of carvacrol and OLA to the PLA_PHB formulations. However, the effect of both additives in fatty food simulant can be considered a positive feature for the potential protection of foodstuff with high fat content. Moreover, the antioxidant and antimicrobial activities of the proposed formulations increased by the presence of carvacrol, with enhanced activity against Staphylococcus aureus if compared to Escherichia coli at short and long incubation times. These results underlined the specific antimicrobial properties of these bio-films suggesting their applicability in active food packaging.

Processing and characterization of nanocomposite based on poly(butylene/triethylene succinate) copolymers and cellulose nanocrystals

A new class of biodegradable materials developed by a combination of random eco-friendly copolyesters containing butylene succinate (BS) and triethylene succinate (TES) sequences with cellulose nanocrystals (CNC), is proposed and studied. Polymers and nanocomposite films were prepared by an optimized extrusion process to improve the processability and mechanical response for flexible film manufacturing. Poly(butylene succinate) (PBS) homopolymer and two random copolyesters containing different amounts of TES co-units, P(BS85TES15) and P(BS70TES30), were synthesized by melt polycondensation. The effect of TES and CNC presence and content on the microstructure, tensile properties, thermal characteristics and disintegration under composting conditions, as well as on the toughening mechanism of the blends was investigated. Material properties were modulated by varying the chemical composition. CNC were used as reinforcement additive and their effect is modulated by the interaction with the three polymeric matrices. The extruded films displayed tunable degradation rates, mechanical properties and wettability, and showed promising results for different industrial applications.

Effect of thermal annealing on the electronic properties of nitrogen doped amorphous carbon/p-type crystalline silicon heterojunction diodes

Heterojunction diodes with hydrogenated amorphous carbon (a-C:H) and nitrogen doped amorphous carbon (a-C:H:N) films on p-type silicon were prepared by means of plasma enhanced chemical vapor deposition. The electronic and structural properties of the films are analyzed as a function of nitrogen doping as well as thermal treatment after deposition. X-ray photoelectron spectroscopy valence band spectra reveal that the electronic structure of the prepared a-C:H:N films depends on thermal annealing. The nature of the heterojunction is confirmed by the rectifying current–voltage characteristic of the carbonaceous deposit/p-Si junction with a heterojunction structure showing a behavior dependent on the amount of both nitrogen concentration and thermal annealing. In particular, the photovoltaic effect is observed only from annealed a-C:H:N heterojunction structures. Raman spectroscopy performed on heterojunction diodes after thermal treatment indicates that this behavior is most likely due to an extended graphi...

An innovative approach to gas sensing using carbon nanotubes thin films: sensitivity, selectivity and stability response analysis

We report that carbon nanotubes (CNTs) thin films have been successfully prepared as new NO/sub 2/ and H/sub 2/ gas sensors in the NO/sub 2/ concentration range 7 ppb - 7 ppm and H2 8.5ppm - 850 ppm respectively. 150 nm thick CNTs thin films, have been prepared by rf-PECVD on Si/Si/sub 3/N/sub 4/ substrates, provided with Pt interdigital sputtered electrodes, and post-annealed under controlled conditions. The electrical response has been investigated at different operating temperatures and gases over a period of 6 months. Sensitivity response analysis has demonstrated that CNTs are more responsive to NO/sub 2/ than H/sub 2/. By selecting suitable annealing conditions, the microstructure significantly changes enabling: to adjust the base line resistance of the film (i.e. the resistance in dry air) from 100 Ohms to several mega-Ohms, and to improve gas sensitivity. Selectivity test have highlighted negligible cross sensitivity effects to the detection of NO/sub 2/, when H/sub 2/ is the interfering gas. Long term stability test have shown a neglegible increase of the base line resistance and an improvement of the NO/sub 2/ sensitivity.

Ozone reactivity with carbon nanotubes: experimental and theoretical studies

Carbon nanotubes (CNTs) thin films have been investigated as new O/sub 3/ gas sensors in the concentration range 75 - 200 ppb. 150 nm thick CNTs thin films, have been prepared by rf-PECVD on Si/Si/sub 3/N/sub 4/ substrates, provided with Pt interdigital electrodes, and post-annealed under controlled conditions. The electrical response to O/sub 3/ has been investigated at different operating temperatures starting from the room temperature. Sensitivity response analysis has demonstrated that CNTs are responsive to O/sub 3/ with a decrease of the baseline resistance similar to that observed for NO/sub 3/. In order to obtain a theoretical validation of the experimental results, the equilibrium position, charge transfer and density of states have been calculated from first principles for the CNT+O/sub 3/ system.

Fluorinated amorphous carbon films prepared by plasma enhanced chemical vapor deposition for solar cell applications

Heterojunction diodes fabricated by plasma enhanced chemical vapor deposition of hydrogenated amorphous carbon (a-C:H) and fluorine doped amorphous carbons (a-C:H:F) on p-type silicon are analyzed in terms of their electronic and photovoltaic properties. Their structural and optical properties were identified by Raman spectroscopy, x-ray photoelectron spectroscopy, ellipsometry, and UV–VIS trasmittance. The nature of the heterojunction is confirmed by the rectifying current–voltage characteristic of the carbonaceous deposits/p-Si junction. The diodes show a behavior dependent on the amount of the fluorine content. The photovoltaic behavior of the junction is investigated as a function of both fluorine incorporation and thermal treatment of the a-C:H:F films after the deposition. Better photovoltaic effects were observed from annealed a-C:H:F heterojunction structures. The optical and structural characterization performed on films after the thermal treatment indicates that this behavior is most likely due ...