RESUMEN
Interfaces can be called Smart and Green (S&G) when tailored such that the required technologies can be implemented with high efficiency, adaptability and selectivity. At the same time they also have to be eco-friendly, i.e. products must be biodegradable, reusable or simply more durable. Bubble and drop interfaces are in many of these smart technologies the fundamental entities and help develop smart products of the everyday life. Significant improvements of these processes and products can be achieved by implementing and manipulating specific properties of these interfaces in a simple and smart way, in order to accomplish specific tasks. The severe environmental issues require in addition attributing eco-friendly features to these interfaces, by incorporating innovative, or, sometimes, recycle materials and conceiving new production processes which minimize the use of natural resources and energy. Such concept can be extended to include important societal challenges related to support a sustainable development and a healthy population. The achievement of such ambitious targets requires the technology research to be supported by a robust development of theoretical and experimental tools, needed to understand in more details the behavior of complex interfaces. A wide but not exhaustive review of recent work concerned with green and smart interfaces is presented, addressing different scientific and technological fields. The presented approaches reveal a huge potential in relation to various technological fields, such as nanotechnologies, biotechnologies, medical diagnostics, and new or improved materials.
Asunto(s)
Tecnología Química Verde/métodos , Nanotecnología/métodos , Adsorción , Aerosoles , Contaminantes Atmosféricos , Coloides/química , Microscopía por Crioelectrón , Electrólitos , Emulsiones , Diseño de Equipo , Gases/química , Humanos , Hidrogeles/química , Pulmón/efectos de los fármacos , Ensayo de Materiales , Microscopía Electrónica de Rastreo , Nanopartículas/química , Nanoestructuras/química , Óptica y Fotónica , Respiración , Propiedades de Superficie , Agua/química , HumectabilidadRESUMEN
Bulk properties of transparent and dilute water in paraffin oil emulsions stabilized with sodium dodecyl sulfate (SDS) are analyzed by optical scanning tomography. Each scanning shot of the considered emulsions has a precision of 1 µm. The influence of aluminum oxide nanoparticles in the structure of the water droplets is investigated. Depending on concentrations of SDS and nanoparticles, a transition occurs in their shape that changes from spherical to polymorphous. This transition is controlled by the SDS/alumina nanoparticles mixing ratio and is described using an identification procedure of the topology of the gray level contours extracted from each images. The transition occurs for a critical mixing ratio of Rcrit ≈ 0.05 which does not significantly depend on temperature and electrolyte concentration. This structural change seems to be a general feature when emulsifying dispersions and most probably involves both interfacial and bulk phenomena.
Asunto(s)
Emulsiones/química , Aceites/química , Parafina/química , Agua/química , Nanopartículas/química , Dodecil Sulfato de Sodio/químicaRESUMEN
Interest in wetting dynamics processes has immensely increased during the past 10-15 years. In many industrial and medical applications, some strategies to control drop spreading on solid surfaces are being developed. One possibility is that a surfactant, a surface-active polymer, a polyelectrolyte or their mixture are added to a liquid (usually water). The main idea of the paper is to give an overview on some dynamic wetting and spreading phenomena in the presence of surfactants in the case of smooth or porous substrates, which can be either moderately or highly hydrophobic surfaces based on the literature data and the authors own investigations. Instability problems associated with spreading over dry or pre-wetted hydrophilic surfaces as well as over thin aqueous layers are briefly discussed. Toward a better understanding of the superspreading phenomenon, unusual wetting properties of trisiloxanes on hydrophobic surfaces are also discussed.
Asunto(s)
Tensoactivos/química , Interacciones Hidrofóbicas e Hidrofílicas , Cinética , Siloxanos/química , Soluciones/química , Propiedades de Superficie , Agua , HumectabilidadRESUMEN
A novel and simple method for the determination of the contact angle of nano- and microparticles at the liquid/air interface is proposed. The principle is based on the consideration of differences between the pressure/area isotherms of a 2D single-component system of a surfactant and those of binary systems comprised of the same surfactant and the particles to be studied. The theoretical analysis of the contact-angle behavior in this system upon compression allows the prediction of direction of the particles' squeezing out of the surface layer and therefore the distinction between the particles with high contact angle (Theta(p) > 90 degrees) and low (Theta(p) < 90 degrees) hydrophobicity. The application of this method to microparticles of two different hydrophobicities demonstrates good agreement between the obtained contact angles and the corresponding degrees of hydrophobicity given by the particle provider.