Francesca Ravera's research while affiliated with Italian National Research Council and other places

Publications (181)

Article
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The input of chemical and physical sciences to life sciences is increasingly important. Surface science as a complex multidisciplinary research area provides many relevant practical tools to support research in medicine. The tensiometry and surface rheology of human biological liquids as diagnostic tools have been very successfully applied. Additio...
Article
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The surface properties of saponin and saponin-chitosan mixtures were analysed as a function of their bulk mixing ratio using vibrational sum-frequency generation (SFG), surface tensiometry and dilational rheology measurements. Our experiments show that saponin-chitosan mixtures present some remarkable properties, such as a strong amphiphilicity of...
Article
Photocatalytic oxidation (PCO) could provide energy-efficient purification of water and air. Its efficacy is constrained mainly by limited photocatalytic activity and active surface. To address both, solid foams with hierarchic porous structures spanning multiple length-scales, stabilized by photocatalytic Zn-doped titania nanoparticles (NP) were s...
Article
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We studied silica suspensions with chitosan and biodegradable synthetic surfactant lau-royl ethyl arginate (LAE). Hydrophilic and negatively charged silica nanoparticles were neutralised due to the coating with chitosan. That presence of LAE led to the partial hydrophobisation of their surface, which favoured their attachment to the surface of a th...
Article
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Pickering emulsions stabilized by the interaction of palmitic acid (PA) and silica nanoparticles (SiNPs) at the water/oil interface have been studied using different alkane oil phases. The interaction of palmitic acid and SiNPs has a strong synergistic character in relation to the emulsion stabilization, leading to an enhanced emulsion stability in...
Article
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Carbonaceous particles are accounted among the most common environmental pollutants. This makes necessary a careful examination of their potential impact on the physico-chemical properties of different biological films, e.g. tear film, skin, or lung surfactant. This work analyzes the interaction of three different types of carbonaceous particles wi...
Article
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The interaction of hydrophobic silicon dioxide particles (fumed silicon dioxide), as model air pollutants, and Langmuir monolayers of a porcine lung surfactant extract has been studied in order to try to shed light on the physicochemical bases underlying the potential adverse effects associated with pollutant inhalation. The surface pressure−area i...
Article
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The dynamic and equilibrium properties of adsorption layers of poly (oxyethylene) alkyl ether (CnEOm) can be well described by the reorientation model. In its classical version, it assumes two adsorption states; however, there are obviously surfactants that can adsorb in more than two possible conformations. The experimental data for C14EO4 and C14...
Article
The pulmonary surfactant (PS) is a complex mixture of lipids and proteins dispersed in the aqueous lining layer of the alveolar surface. Such a layer plays a key role in maintaining the proper lung functionality. It acts as a barrier against inhaled particles and pathogens, including viruses, and may represent an important entry point for drugs del...
Article
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The adsorption behaviour of linear poly(oxyethylene) alkyl ether (CnEOm) is best described by a reorientation model. Based on a complete set of experimental data, including the adsorption kinetics, the equilibrium surface tension isotherm and the surface dilational visco-elasticity, the thermodynamic and kinetic adsorption parameters for some CnEOm...
Article
In this review, we highlight and discuss the effects of interfacial properties on the major mechanisms governing the aging of emulsions: flocculation, coalescence and Ostwald ripening. The process of emulsification is also addressed, as it is well recognized that the adsorption properties of emulsifiers play an important role on it. The consolidate...
Article
We report here an overview of current trends and a selection of recent results regarding the characterization of emulsions by Diffusing Wave Spectroscopy (DWS). We provide a synopsis of the state of the art of the DWS technique, and a critical discussion of experiments performed on samples in which Brownian and ballistic dynamics coexist. A novel a...
Article
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The present work is aimed at investigating the chemicophysical properties of the interface between silicone oils (SOs) used in vitreoretinal surgery and aqueous solutions, in the presence of surfactant biomolecules. Such molecules are thought to play an important role in the formation of SO emulsions in vitrectomised eyes, in which the natural vitr...
Article
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An increase in temperature typically leads to a decrease in the interfacial tension of a water/oil interface. The addition of surfactants to the system can complicate the situation significantly, i.e., the interfacial tension can increase or decrease with an increasing temperature. For most concentrations of the two studied surfactants, the cationi...
Article
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Lipid layers are considered among the first protective barriers of the human body against pollutants, e.g., skin, lung surfactant, or tear film. This makes it necessary to explore the physico-chemical bases underlying the interaction of pollutants and lipid layers. This work evaluates using a pool of surface-sensitive techniques, the impact of carb...
Article
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A comparative study is reported on the interfacial properties of a set of surfactants and is discussed in terms of the e�ects on the features of the corresponding oil-water emulsions. The surfactants are saponin, Tween 80 and citronellol glucoside (CG), while the oil is Miglyol 812N—A Medium Chain Triglyceride (MCT) oil. Due to their high biocompat...
Article
The theoretical description of the adsorption of surfactants at interfaces between aqueous solutions and oil was based over a very long time on models derived for the solution/air interface. Thus, most of the experimentally observed peculiarities could not be specifically considered but were merely interpreted in terms of a penetration of oil molec...
Article
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In this communication, the single element version of the fractional Maxwell model (single-FMM or Scott–Blair model) is adopted to quantify the observed behavior of the linear interfacial dilational viscoelasticity. This mathematical tool is applied to the results obtained by capillary pressure experiments under low-gravity conditions aboard the Int...
Article
Diffusing Wave Spectroscopy (DWS) is a technique used to characterize microscopic structure and rheological properties of turbid samples. This is achieved by analyzing the time evolution of coherence speckles of light that has been multiply scattered within the sample. One attractive feature of DWS is that it is non-invasive, and robust. For this r...
Article
We employ Diffusing Wave Spectroscopy (DWS) to characterize microscopic structure, internal dynamics and rheological properties of a paradigmatic emulsion formed by water and dodecane stabilized by the anionic surfactant Sodium Dodecyl Sulfate (SDS). We focus on ageing and stability in the regime of low surfactant concentration, well below the Crit...
Article
This work focuses on the surface properties of binary dispersions of nanoparticles, namely Titania (TiO 2 )and amorphous silica (SiO 2 ), associated to a short chain ionic surfactant (CTAB)which has the role of modifying their amphiphilicity, inducing the segregation of particle-surfactant complexes at the liquid interface. The foams produced by th...
Article
In this work we investigate the surface properties and foamability of saponin and mixed saponin-chitosan solutions. These natural compounds are widely used in various cosmetic, pharmaceutical and food technologies because of their efficiency as bio-active components and their biodegradability. These compounds and their mixture were investigated ver...
Article
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Capillary pressure experiments are performed in microgravity conditions on board the International Space Station to quantify the dynamic interfacial behavior of mixed adsorption layers of TTAB and C13DMPO at the water/hexane interface. While the non-ionic surfactant C13DMPO is soluble in both bulk phases, water and hexane, the cationic surfactant T...
Article
Carbon monolithic adsorbents exhibiting a hierarchical pore structure are produced via a synthesis route based on the stabilization of liquid foams followed by a carbonization step. The macro-microporous structure is achieved by the incorporation of microporous, biomass-derived activated carbon particles in the liquid foam enclosed by a cationic su...
Conference Paper
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The formation and stability of emulsions in vitrectomized eyes is linked to the properties of the silicone oil-aqueous humor interface, in particular the surface tension. In the presence of natural surfactants, such as serum and plasma, the value of the surface tension is likely to change, but little quantitative information is presently available....
Article
The control of the behavior of oil in water emulsions requires deepen investigations on the adsorption properties of the emulsion stabilizers at interfaces, being these fundamental to explain the (de)stabilization mechanisms. In this work, we present an extensive study on oil-in-water emulsions stabilized by Sodium Dodecyl Sulfate (SDS) below its c...
Article
A new approach to the analysis of nonlinear surface dilational rheological properties was developed with the aim to enlarge the accessible range of surface pressures. The dilational surface elasticity of spread monolayers of DPPC, cholesterol, DMEA and their mixtures was determined in the region of low surface tensions (less than 10 mN/m) correspon...
Article
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The effect of the incorporation of hydrophilic titanium dioxide (TiO2) nanoparticles on the interfacial properties of Langmuir monolayers of 1,2-Dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC) has been evaluated combining interfacial thermodynamic studies, dilatational rheology and Brewster Angle Microscopy (BAM). The results show that the TiO2 nan...
Article
Measurements by capillary pressure tensiometry, under microgravity conditions aboard the International Space Station, supplied a consistent set of reliable results for the dynamic interfacial tension and for the interfacial dilational viscoelastic modulus, quantitatively characterizing the dynamics of Span-80 adsorbed layers at the paraffin-oil/wat...
Article
The adsorption kinetics of ionic surfactant decanoic acid was examined. Dynamic and equilibrium surface tensions (ST) were measured using a video-enhanced pendant bubble tensiometer. The equilibrium ST data and the complete ST relaxation profiles were compared with theoretical profiles predicted by both non-ionic and ionic models. The quasi-equilib...
Article
The adsorption kinetics of ionic surfactant decanoic acid was examined. Dynamic and equilibrium surface tensions (ST) were measured using a video-enhanced pendant bubble tensiometer. The equilibrium ST data and the complete ST relaxation profiles were compared with theoretical profiles predicted by both non-ionic and ionic models. The quasi-equilib...
Article
Particle stabilized liquid foams are used as templates to obtain carbon-based porous materials with open cell structure, high specific area and hierarchical porosity. This route relies on gel casting to strengthen the structure of the liquid foams, followed by high temperature treatment to eliminate organic components and obtain solid foams. The li...
Article
Silica nanoparticles (SiNP) can be incorporated in phospholipid layers to form hybrid organic-inorganic bidimensional mesostructures. Controlling the dynamics in these mesostructures paves the way to high-performance drug-delivery systems. Depending on the different hydrophobicity/hydrophilicity of SiNP, recent X-ray reflectivity experiments have d...
Article
Highly hydro and oleophobic materials applied to needs of the marine environment represent a relatively young field achieving growing interest as innovative solution, where technological and ecological aspects allow to be merged, taking into account the limitations imposed by international laws in terms of environmental protection.In this work a su...
Article
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We investigate the interfacial dynamics of a 2D self-organized mixed layer made of silica nanoparticles interacting with phospholipid (DPPC) monolayers at the air/water interface. This system has biological relevance, allowing investigation of toxicological effects of nanoparticles on model membranes and lung surfactants. It might also provide bio-...
Article
The interaction of carbon black particles (CB) with 1,2-Dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC) at the water/air interface has been investigated by means of a pool of surface sensitive techniques, in order to analyze the thermodynamic and rheological aspects of these mixed systems. The incorporation of carbonaceous particles to the lipid mo...
Article
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The incorporation of Silica nanoparticles (NPs) from the subphase into Langmuir lipid monolayers formed by three components, 1,2-Dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC), 1,2-Dioleoyl-sn-glycero-3-phosphocholine (DOPC) and Cholesterol (Chol), modifies the thermodynamic and rheological behaviour, as well as the structure of the pristine lipid...
Article
tHighly water repellent coatings known as superhydrophobic (SH) are related to surfaces with contactangles above 150º and a very small hysteresis. Among many practical needs to which this property can be devoted, a very interesting field where theSH coating technology can be employed is represented by the protection of hulls in seawater environ-men...
Article
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The combination of interfacial thermodynamic, dilational rheology and Brewster Angle Microscopy (BAM) has allowed the evaluation of the effect of hydrophobic fumed silica nanoparticles on the interfacial properties of Langmuir monolayers of 1,2-Dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC). Fumed silica particles modify the surface pressure-area...
Article
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We report here a review of particle-laden interfaces. We discuss the importance of the particle’s wettability, accounted for by the definition of a contact angle, on the attachment of particles to the fluid interface and how the contact angle is strongly affected by several physicochemical parameters. The different mechanisms of interfacial assembl...
Article
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An experimental study is here presented on the properties of aqueous dispersions containing carbon nanoparticles and different ionic surfactants which can modify the degree of hydrophobicity/philicity of particles favoring their transfer from the dispersion bulk to the interfacial layer. Aim of this work is to understand the particle-surfactant and...
Article
In this work, a method is proposed for the production of carbon porous materials based on the foaming of a carbon colloidal dispersion in the presence of a short chain ionic surfactant (CTAB) and Poly(vinyl alcohol) followed by the in situ polymerization by cross-linking with 2,5-dimethoxy-2,5-dihydrofuran (DHF). The particle stabilized wet foams a...
Article
We 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 dispersions. The transfer/incorporation of NPs into the DPPC monolayer, driven by electrosta...
Article
The interfacial tension response to dilational deformation of interfacial area exhibits a (more or less) nonlinear behavior, depending on the amplitude of the deformation. Studies of such observable interfacial properties in the nonlinear domain suggest valuable information about the two-dimensional microstructure of the interfacial layer, as well...
Article
This short review is devoted to recent achievements in studies of the dilational surface rheological properties of the systems containing complexes of silica nanoparticles with conventional surfactants. It is shown that there is a surfactant concentration range where the dynamic surface elasticity reaches extremely high values up to 1000 mN/m. This...
Article
An experimental study is here presented focused on the problem of tailoring of solid foams with controlled structural and chemical features produced by drying and/or sintering of liquid foams stabilized by nanosized materials. The aim of this study is a better understanding of the relation between the interfacial properties of mixed systems contain...
Article
Human whole saliva (HWS) is a physiological secretion that performs a number of essential functions including protection of oral health, lubrication of mouth tissues and food pre-digestion. The complexity of the saliva proteome reflects the unique physiochemical functionality of this biofluid. In addition, saliva influences the transduction of arom...
Article
In the second part of this communication we screen a few tea polyphenols for their ability to interact with pre-adsorbed salivary proteins at the air-liquid interface. Using interfacial dilational rheology characterisation, we measure the variation in surface elasticity of a pre-adsorbed salivary film after exposure to tea polyphenols solutions in...
Article
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The adsorption films of silica nanoparticles modified by a cationic surfactant (cetyltrimethylammonium bromide, CTAB) at the air–water interface were investigated by the dilational surface rheology and optical methods. Special attention was paid to the slow changes of surface properties with the surface age. The surface tension and dynamic dilation...
Article
Langmuir monolayers of Cholesterol (Chol) and a mixture of Chol with 1,2-Dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC), at a ratio of 17:83 in weight, spread on pure water and on silica nanoparticle dispersions, have been investigated measuring the compression isotherms as well as the surface pressure response to harmonic area variation of the mo...
Article
Langmuir monolayers of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and mixtures of DOPC with 1,2-dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC), at a ratio of 37:63 in weight, spread on pure water and on silica nanoparticle dispersions, have been investigated using a combination of thermodynamic, surface theology, BAM and AFM diagnostics. The...
Article
The effect of silica nanoparticles on the thermodynamic and structural properties of monolayers of 1,2-dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC), palmitic acid (PA) and a mixture of them, has been investigated using a combination of Langmuir trough technique and Brewster Angle Microscopy (BAM). This study shows that the presence of nanopartic...
Article
A new methodology, based on fundamental optical principles relevant to the evanescent wave properties, is developed to evaluate the thinning behavior and the local thickness in different positions for curved aqueous emulsion films, generated in a hydrocarbon matrix. This methodology is applied to test data obtained by a specially-designed bread-boa...
Article
This work is focused on the physico-chemical characterization of carbonaceous nanometric particulate produced from controlled combustion sources and on its effects on dynamic interfacial tension and surface dilational rheology of aqueous interfaces and on foamability. Since large quantities of surfactants are introduced into waste waters and water...
Article
The effect of silica nanoparticles on the dynamic behavior of monolayers composed by 1,2-Dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and a mixture of DPPC with Palmitic acid (PA), has been investigated by comparing the dilational rheological response of these lipid layers, spread on water and on a silica nanoparticle dispersion. To this aim, the...
Article
The formation and properties of composite layers of silica nanoparticles and an oil-soluble (fatty) amine surfactant at the oil–water interface have been studied using interfacial tensiometry, rheology, and contact angle measurements to characterize the synergy between the particles and surfactant. The initially hydrophilic particles interact with...
Article
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The hydrophobicity of a particle surface can be tuned by the addition of surfactants that change the surface free energy for their attachment to a liquid interface. In this work, we report an experimental study where the wettability properties of silica nanoparticles are modified by the adsorption of alkyltrimethylammonium surfactants (C(n)TAB, n =...
Article
The aim of the present study is to clarify how the surfactant adsorption layer properties are related to the course of the drainage parameters of microscopic foam films in the special case of aqueous solutions of the non-ionic amphiphile tetraethyleneglycol monododecyl ether (C12E4), containing premicellar nanostructures. The scope of the research...
Article
The properties and structure of different types of interfacial layers obtained from aqueous dispersions of nanometric silica and palmitic acid (PA) have been studied and characterized by different diagnostics and measurements. The investigations concern PA monolayers spread on the silica dispersions, dispersions in contact with PA solutions in oil...
Article
The study of the interaction between Langmuir monolayers of 1,2-dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC), as the major component of lung surfactant (LS), and nanoparticles of different nature, hydrophilic silica (SiO2) and hydrophobic carbon black (CB), has been carried out by measuring the compression Π–A isotherms and the response of the s...
Article
The interfacial properties of aqueous dispersions are strictly connected to the transfer/accumulation of particles into the surface layer, driven by the particle hydrophobicity. The addition of surfactants adsorbing on the particles and tuning their hydrophobicity represents therefore an attractive route to control the properties of these liquid in...
Article
This study is focused on understanding how the combination of silica nanoparticles with a cationic surfactant (CTAB) may lead to the formation of different solid-like structures at the water/air interface. In fact, the adsorption of CTAB onto the solid particles’ surface changes their hydrophilic/lipophilic state which becomes more hydrophobic with...
Chapter
Measurements of equilibrium and dynamic interfacial tension of liquid interfaces are of great importance for many practical applications. Many technological processes, e.g. involving liquid-liquid extraction, foams and emulsions, liquid metals and alloys, multiphase flows and many others, strongly depend on interfacial tension [1]. Interfacial tens...
Chapter
The general way of characterising the stability of foams or bubbles is the registration of some integral properties, such as the volume of a foam [1] or the creaming in an emulsion [2]. For liquid film studies, however, no direct correlation between film properties and adsorption layer characteristics on one side, or foam/emulsion stability on the...
Chapter
A. Introduction The Drop/Bubble Profile Analysis Tensiometry (PAT) is a well-established technique for determining static and dynamic properties of liquid-gas and liquid-liquid interfacial systems. Specifically, for the determination of interfacial tension, PAT is an accurate measurement method being metrologically based on a fundamental physical p...