2,437 research outputs found
Exploiting optothermal conversion for nanofabrication: site-selective generation of Au/TiO2 inverse opals
No full textWater use in three Sedum species under drought condition in green roof substrates and their role green roof performances
No full textTemplate controlled synthesis of monometallic zerovalent metal nanoclusters inside cross-linked polymer frameworks: the effect of a single matrix on the size of different metal nanoparticles
No full textStarting from the gel-type, cross-linked copolymer co-poly-{(N,N-dimethethylacrylamide/4-vinylpyridine/N,N'-methylenebisacrylamide} (DV44) we prepared nanoclusters of several noble metals (Ru, Rh, Pd, Pt, Ag, Au) inside its polymer framework through the so-called "template-controlled synthesis'' approach. This procedure involves the immobilization of the relevant metal centers inside the polymer framework, followed by their reduction to M(0) nanoclusters (in our case, uptake from solutions of suitable precursors and reduction with aqueous solutions of NaBH(4), respectively). In this way, a set of monometallic polymer supported nanoclusters (M/DV44, M = Ru, Rh, Pd, Pt, Ag, Au) were obtained. The experimental conditions were set so as to generally obtain a homogeneous radial distribution of the metal throughout the particles of the materials. The latter were characterized by means of transmission electron microscopy for the assessment of the metal nanocluster sizes. The diameter of the nanoclusters generated by reduction inside water-swollen DV44 were compared with the size of the nanopores of the water-swollen polymer framework that had previously been determined by means of inverse steric exclusion chromatography. The diameter of the prevailing pore fractions in water-swollen DV44 was 3.2-4.3 nm and the largest available pores observed had a diameter of 8.1 nm. Nanoclusters with diameters larger than this value were observed in no cases, and in all cases the average diameter of the nanoclusters never exceeded the diameter of the prevailing pore fraction. For Pd/DV44, Ag/DV44 and Au/DV44, the average nanocluster diameter compared very well with the diameter of the prevailing pore fraction
In situ plasmon-heating-induced generation of Au/TiO2 hot spots on colloidal crystals
No full textGold nanoparticles have been extensively investigated due their chemical and physical properties, which make them suitable for catalysis, optoelectronics and sensing. In particular, sensing and biodiagnostics take advantage of the affinity exhibited by gold nanoparticles towards thiols to form Au-(bio)-conjugates through a simple surface chemistry. Moreover, the chance to excite gold surface plasmons upon interaction with an electromagnetic field gave rise to ultra-sensitive diagnostic techniques such as surface plasmon resonance (SPR) and surface-enhanced vibrational spectroscopies (SEVSs). We report the in situ generation of Au/TiO2 micrometric spots on polymeric colloidal crystals. These spots resulted from the local crystallization of amorphous TiO2 (a-TiO2), which was induced by interaction between a low-power CW laser and closely aggregated gold nanoparticles, and promoted by the polymeric support.
The enhancement of the electromagnetic field due to the presence of gold nanoparticles allowed the in situ SERS characterization of the anatase thin film. Finally, we showed that these spots can be used as model sites to investigate some reaction occurring at the metal oxide surface. This is an important benefit in some research fields, such as photocatalysis in nanoscaled devices, as it allows some parameters, like the thickness of the photocatalyst or the concentration of the catalytic substrate to be optimized. Moreover, these substrates could be conveniently employed as plasmonic photocatalysts, enabling a number of important reactions to occur with high efficiency and minimal light exposure. In perspective, this approach could easily be extended to other classes of compounds, opening new frontiers for plasmon heating-driven processes
Ecological Performances of Plant Species of Halophilous Hydromorphic Ecosystems
No full textCoastal wetlands are very special environments, characterized by soils permanently or seasonally saturated by salt or brackish water. They host microorganisms and plants able to adapt to anoxic conditions. This paper proposes a review of recent scientific papers dealing with the study of coastal wetlands from different points of view. Some studies examine the species composition and the pattern of the spatial distribution of plant communities, depending on the depth of the salt water table, as well as on other related factors. A significant number of studies analyse instead the coastal wetlands in their ability for the phytoremediation (phytostabilisation and/or phytoextraction) and highlight the importance of interactions between the rhizosphere of the halophytes and the physical environment. Finally, more recent studies consider the plant species of the coastal wetlands as a source of useful products (food, feed, oils) and expose the results of promising researches on their cultivation
Plasmon-Assisted, Spatially Resolved Laser Generation of Transition Metal Oxides from Liquid Precursors
No full textPlasmonic heating-triggered laser generation of nanocrystalline oxides on colloidal crystal substrates has been so far limited by deposition of the oxide precursors, which relies on chemical vapor methods. A novel approach, based on infiltration of liquid precursors and characterized by a good control of spatial localization, was reported in this paper. Patterning of titanium oxide spots and microchannels was successfully performed. Additional advantages were highlighted by extending this procedure to oxides, such as ZnO and CeO(2), which are otherwise difficult to generate on these substrates by traditional approaches. Raman microspectroscopy evidenced the highly defective, nanocrystalline nature of the oxides. Scanning electron microscopy provided further microstructural information that allowed us to gain more insight into the mechanisms that govern the formation of these oxide spots and channels
Performance-aware load shedding for monitoring events in container based environments
No full textRuntime monitoring tools have become fundamental to assess the correct operation of complex systems and applications. Unfortunately, the more precise is the monitoring (sampling rate, information granularity, and so on), the higher is the overhead introduced in the system itself. In this paper, we propose a new load shedding framework that enables runtime adaptation of monitoring agents under heavy system load, exploiting an heuristic Load Manager to control the agent status and a runtime support for domain-specific policies. We implemented the proposed methodology on Sysdig, with an average control error improvement of 3.51x (12.25x at most), w.r.t. previous solutions
Modelling of dust resuspension in Tokamak devices during an air inflow event
No full textIn a Tokamak-fusion reactor, the plasma interacts with the first wall generating dust of different materials. Dust can play an important, if not primary, role in determining safety and economic performance of this type of fusion machines, due to potential accident and maintenance requirements. In this paper, after a brief introduction, a description of dust explosion mechanism is reported with reference to several experiments used to create or validate theories and models. The safety concerns about dust are based on the assumption that, in case of air inflow events, this particulate can be resuspended in the vacuum vessel leading to a potential explosive cloud. In the paper the main literature models used to deal with dust transport and resuspension are reported: the VZFG model, the Rock n’ Roll model and the ECART model. Differences, pros and cons of each models are described to obtain a comparison between energy-based and force-based balance models. Finally, the numerical approach for the resuspension phenomenon is discussed and an application is shown. The simulation has been carried out with reference to a laboratory scale facility-like in 3D geometry. The simulated event is an air flow intake, as from a Loss of Vacuum Accident, and the results show the distribution of dust in the geometry after the first instants of intake, the mass concentration of particulate on the surfaces and the path lines of the flow field. The simulated geometry is only partially referred to an existing experimental facility, and the methodology could be useful to replicate the same conditions to obtain a validation of the results. More and finer simulations are foreseen to reproduce more accurately experimental data and real scenarios, with the aim to evaluate the risk of explosion by means of an accurate prediction of dust distribution inside a vacuum volume during resuspension due to air inflow
Plasmonic Heating-Assisted Transformation of SiO2/Au Core/Shell Nanospheres (Au Nanoshells): Caveats and Opportunities for SERS and Direct Laser Writing
No full textThe selective modification of silica/gold nanospheres (gold nanoshells) driven by plasmonic heating is demonstrated. Direct laser writing and reshaping of nanoshell assemblies can be easily controlled and exploited for nanofabrication purposes. The modified nanoshells exhibit improved surface enhanced Raman scattering, allowing to settle most of the issues related to nanoshell stability under working condition
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