Characterization of the PCDD/F in the Province of Trento

Abstract This paper aims to improve the already existing literature data on air concentrations of polychlorinated dibenzo- p -dioxin and dibenzofurans (PCDD/Fs). Four monitoring campaigns were carried out between 2002 and 2010 near Trento, a town in the North of Italy. These campaigns showed relatively low PCDD/F concentrations, in line with the values found in other Italian urban and industrial sites. Typical values for agricultural regions were measured in rural areas, with an increase during winter, possibly due to biomass burning. No critical situations were detected along an important highway, in spite of the non-negligible emission factors for traffic reported in the literature

TiO2-coated pSi microparticles for nanomedicine

Porous silicon (pSi) is a sponge-like material that, due to quantum confinement effect, is photoluminescent when excited by UV light. We developed a process to obtain mesoporous silicon microparticles by electrochemical etching and we proved them to be optically stable in biological buffers once opportunely coated. This material is a promising system for nanomedicine application, first, because it is biodegradable, biocompatible and not activator of the immune response, then, since the porosity and the photoluminescence make them suitable for drug delivery and bioimaging. The microparticles were coated by ALD (atomic layer deposition) in a rotary reactor to avoid optical and structural degradation in aqueous media. A thin and uniform TiO2 layer was deposited on the pSi microparticles (pSi-TiO2 microparticles), without occluding the pores. In-vitro tests were performed to control the effect of pSi-TiO2 microparticles on human dendritic cells (DCs). We observed no decrease of cell viability after the internalization of the microparticles that maintained their PL, as can be seen in Figure 1, but an increase of the immune response (priming effect) in case of co-stimulation with an immune response activator. These preliminary results, recently published, are promising for the pSi-TiO2 microparticles application in nanomedicine, in particular, for drug delivery and bioimaging

Role of sonication pre-treatment and cation valence in the sol-gel transition of nano-cellulose suspensions

Abstract Sol-gel transition of carboxylated cellulose nanocrystals has been investigated using rheology, SAXS, NMR and optical spectroscopies to unveil the distinctive roles of ultrasound treatments and addition of various cations. Besides cellulose fiber fragmentation, sonication treatment induces fast gelling of the solution. The gelation is independent of the addition of cations, while the final rheological properties are highly influenced by the type, concentration and sequence of the operations since the cations must be added prior to sonication to produce stiff gels. The gel elastic modulus was found to increase proportionally to the ionic charge rather than the cationic size. In cases where ions were added after sonication, SAXS analysis of the Na+ hydrogel and Ca2+ hydrogel indicated the presence of structurally ordered domains in which water is confined, and 1H-NMR investigation showed the dynamics of water exchange within the hydrogels. Conversely, separated phases containing essentially free water were characteristic of the hydrogels obtained by sonication after Ca2+ addition, confirming that this ion induces irreversible fiber aggregation. The rheological properties of the hydrogels depend on the duration of the ultrasound treatments, enabling the design of programmed materials with tailored energy dissipation response

Water Diffusion Effectsat Gold-Graphene Interfaces Supporting Surface Plasmon Polaritons

We present a detailed investigation on the effects of water diffusion at the different interfaces of gold-graphene plasmonic sensors on the propagation of the supported surface plasmon polaritons (SPPs). The substrate/metal interfacial chemical reactions are investigated by monitoring the full width at half-maximum of the SPR reflectivity curve. Although protection by single-layer graphene (SLG) grown by chemical vapor deposition inhibits the chemical reactions happening at the metal-dielectric interfaces, SPR experimental results confirm that water diffusion paths through the borders of graphene domains are still present into the plasmonic sensors. Density functional theory calculations show that the doping level of SLG after the transfer on gold as well as interfacial charge transfer can be tuned in the presence of water molecules. On these bases, we propose a simplified effective medium approach for heterogeneous metal-carbon interfaces, where the interaction between the surface atomic layers of the gold thin film, water molecules, and the SLG induces the creation of an extended charge density difference region crossing the Au/H2O/SLG/H2O heterointerface. The latter is modeled as an ultrathin effective medium with a thickness and extraordinary optical susceptivity and conductivity that are different from those of the free-standing graphene. In this context, the extraordinary refractive index and thickness of the graphene-gold effective medium are measured in the near-infrared on the low-damping SPR platforms by applying the two-medium SPR method. The results are coherent with graphene n-doping in water environment, showing that the optically excited electrons along the extraordinary axis have a substantial bonding character and that the enhancement of the sensitivity of the gold-graphene plasmonic sensors is not related to a shift in the plasma frequency of the metal layer but to the changes in the extraordinary polarizability of graphene. The research highlights the importance of the SLG-substrate and SLG-environment interactions in graphene-protected plasmonics and optoelectronics