1,721,004 research outputs found
Tailoring solid foam structures for high-efficiency photocatalytic filtration of air and water
No full textABSTRACT
Solid foams are increasingly recognized for their potential in advanced functional applications, particularly in
photocatalytic air and water purification systems. Enhancing their efficiency however requires foams that
simultaneously exhibit high permeability and robust mechanical properties—both dictated by the foam’s
microstructural morphology, notably the connectivity and distribution of open pores. In direct foaming methods,
these characteristics are imparted via a two-step fabrication process involving the formation of a polymeric
precursor loaded with inorganic nanoparticles (green body), followed by thermal calcination. Since the final
inorganic structure replicates the morphology of the green body, optimizing the precursor is critical. In this work,
we investigate the tunability of green body foam architecture by varying key synthesis parameters, including air
volumetric fraction and crosslinker concentration. We demonstrate that careful modulation of these variables
yields solid foams with tailored porosity and enhanced permeability, while preserving good mechanical properties. These findings offer valuable insights into structure–property relationships in porous solids and support
the development of foam-based systems for catalytic and environmental technologies
Diffusing wave spectroscopy for the study of emulsions on-ground and in microgravity
No full textWe review the approaches, both experimental and modelling, and the main results obtained recently in the investigation of emulsions by diffusing wave spectroscopy (DWS). DWS is a correlation spectroscopy based on the analysis of the time structure of the scattered light emerging from a laser illuminated opaque sample. Such a non-invasive technique is well suited to the investigation of drop size distribution and drop dynamic in emulsions. This dynamic determines the evolution, and finally the fate, of emulsions. Results obtained in laboratory are complemented by very recent results obtained in microgravity (the condition of absence of weight obtained in orbit) onboard the International Space Station ISS: mastering emulsions in such exotic conditions, not only offers new insight into the basic physical phenomena but may also provide new enabling technologies to ensure comfortable living environments and safe foods to the astronauts engaged in long space flights
Two-Dimensional DPPC Based Emulsion-like Structures Stabilized by Silica Nanoparticles
No full textWe studied the mechanical and structural properties of mixed surface layers composed by 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and silica nanoparticles (NPs). These layers are obtained by spreading a DPPC Langmuir monolayer on a colloidal silica dispersion. The transfer/incorporation of NPs into the DPPC monolayer, driven by electrostatic interactions, alters the molecular orientation, the mechanisms of domain formation, and consequently the phase behavior of the surface layer during compression. The investigation of these systems by means of complementary techniques (Langmuir trough, fluorescence microscopy, ellipsometry, and scanning electron microscopy (SEM)) shows that the incorporated NPs preferentially distribute along the liquid expanded phase of DPPC. The layer assumes the stable and homogeneous bidimensional structure of a two-dimensional (2D) analogue of a Pickering emulsion. In fact, the presence of particles provides a circular shape to the DPPC domains and stabilizes them against growth and coalescence during the monolayer compression
Particle sizing in non-dilute dispersions using diffusing wave spectroscopy with multiple optical path lengths
Full text linkNon-dilute dispersed phase systems, such as foams, emulsions, and suspensions, are an important class of final formulations and chemical process intermediates in a variety of industries. The utility of these systems hinges on their stability over the lifetime of use, and therefore an accurate assessment of chemical and physical dynamics, asformulated, is required. We describe a unified treatment of diffusing wave spectroscopy (DWS) data using a range of optical path length with a goniometric instrument. DWS correlation data from multiple angles and robust Monte Carlo simulations are used to determine accurate values of the photon transport mean free path length. The variance on each correlation function is used to determine the physical time range that the mean squared displacement can be analyzed. Using standard solid particle suspensions of polystyrene and SiO2, we determine the average particle size with accuracy comparable to dynamic light scattering
Heterogeneous and anisotropic dynamics of a 2D gel
No full textWe report x-ray photon correlation spectroscopy (XPCS) results on bidimensional (2D) gels formed by a Langmuir monolayer of gold nanoparticles. The system allows an experimental determination of the fourth order time correlation function, which is compared to the usual second order correlation function and to the mechanical response measured on macroscopic scale. The observed dynamics is anisotropic, heterogeneous and superdiffusive on the nanoscale. Different time scales, associated with fast heterogeneous dynamics inside 2D cages and slower motion of larger parts of the film, can be identified from the correlation functions. The XPCS results are discussed in view of other experimental results and models of three-dimensional gel dynamics
On the relation between hierarchical morphology and mechanical properties of a colloidal 2D gel system
No full textWe study a bidimensional gel system formed by a Langmuir film of gold nanoparticles. Its morphology is thoroughly characterized by AFM, SEM, and ellipsometric imaging techniques and shows a complex structure with features on a hierarchy of different sizes following a Levy distribution. The mechanical response arising after the gel point is investigated by Interfacial Shear Rheometry. The film is found to be mainly elastic, with the mechanical moduli scaling as a power law of the reduced concentration, in the same way as the fluctuation time which was measured in a recent X-ray Photon Correlation Spectroscopy experiment. The frequency dependence of the moduli is well described in the framework of the Soft Glass Rheology model (SGR) [Sollich et al. Phys Rev Lett 78, 2020 (1997)]. In this theory a power law distribution of relaxation times is postulated, whose exponent is experimentally determined for the present case. Such a distribution may reflect – in the dynamics – the hierarchical nature of the morphology of the film evidenced by microscopy. A mastercurve can be built, extending time–temperature to a time–concentration superposition principle as in [Cicuta et al. Phys Rev Lett 90, 116103(2003)]. This allows to describe the mechanical response over a frequency range slightly larger than that experimentally accessible. Besides the SGR component, a viscous term is always present, whose origin is investigated also taking into account samples with different preparation histories
Equilibrium and out-of-equilibrium dynamics in a molecular layer of azopolymer floating on water studied by Interfacial Shear Rheology
No full textScintillating and magnetic stimuli-responsive nanostructures as adjuvants in cancer therapy
No full textWe present an overview of recent advances in stimuli-responsive nanostructures for medicine and drug delivery aiming at improving the efficacy and minimizing side effects of cancer therapies. We focus on two complementary system: Self-Lighted Photodynamic Therapy (SLPDT), and magnetic systems for hyperthermia and for controlled drug release. SPLDT, also known as X-ray triggered PDT, bases on hybrid nanostructures such as functionalized SiC/SiOx nanowires and CeF3/ZnO nanostructures. We emphasize the importance of discriminating the various Reactive Oxygen Species (ROS) produced, i.e., singlet oxygen, peroxide, superoxide, and hydroxyl radicals, which have different effects on cells and different therapeutic efficacy. Singlet oxygen is quantified by an ad hoc NIR fluorimeter. SLPDT can be usefully complemented by smart systems responsive to magnetic fields. As examples, we discuss the use of superparamagnetic iron oxide nanoparticles for magnetic hyperthermia and magnetic nanocapsules for triggered drug release. Finally, we highlight promising directions for future developments
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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