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The Atmosphere and the Chemistry of Air
Published in Armen S. Casparian, Gergely Sirokman, Ann O. Omollo, Rapid Review of Chemistry for the Life Sciences and Engineering, 2021
Armen S. Casparian, Gergely Sirokman, Ann O. Omollo
An aerosol is a gas–liquid or gas–solid colloid. Colloids (discussed in Chapter 3) are materials that form a stable system, but the particle sizes of the solute are large in comparison to the solvent molecules. Aerosols are very finely dispersed liquid or solid particles that hang in suspension in air. They are usually 100 microns or less in diameter, e.g., as produced in a human sneeze or a cough. Those that are larger than 300 microns are usually droplets. Ash released by power plants, referred to as fly ash, is one example of a gas–solid colloid. The paint sprayed from a spray paint gun can also form an aerosol while in the air. There is a fine distinction between colloids and suspensions. A colloid is a stable system that does not require periodic mixing. Milk and blood are examples of colloids, also referred to colloidal dispersions. A colloidal suspension, on the other hand, requires periodic stirring to approach uniformity. Paints and many cough medicines, which require stirring or shaking, are examples of suspensions.
Nanostructures in Nanoionics and Colloidal Chemistry: Overview and Problems
Published in Junko Habasaki, Molecular Dynamics of Nanostructures and Nanoionics, 2020
Besides the enhancement of ion dynamics, spontaneous formation of the gel from the nanocolloidal solutions and its complex structures are the main problems treated in this book. Hereafter, the situation of the complicated structures of aggregates and gels known in experimental works will be summarized. Among nanoscale structures, colloidal systems play important roles in many fields, including the pharmaceutical and biotechnology fields. Both obtaining the well-dispersed colloidal solutions and controlling the development of aggregates and gels are targets of challenges in colloid chemistry. This is also important in industry and environmental chemistry. Specifically, extracting heavy metals from water coagulation using colloidal silica or sodium silicate is a useful technique. Therefore, it is an important task to learn the mechanism of coagulation. In this section, several examples of studies of the formation of gels found in the history of colloidal chemistry will be shown.
Recent Advances in Glycolipid Biosurfactants at a Glance: Biosynthesis, Fractionation, Purification, and Distinctive Applications
Published in Vineet Kumar, Praveen Guleria, Nandita Dasgupta, Shivendu Ranjan, Functionalized Nanomaterials I, 2020
The diversification of nanotechnology into the biomedical realm has enormously widened the scope of targeting a diverse array of drugs and bioactives in comparison to conventional drug delivery systems. The advancement in the development of nanocarriers such as micelles, vesicles, niosomes, liposomes, microemulsions, nanoemulsions, polymeric nanoparticles, lipid nanoparticles, etc. has also escalated the demand to quash the commercialization conundrum [1]. In colloidal assemblies, the surfactant generally plays a crucial role in the stabilization of the fabricated structures; e.g., in nanoemulsions, the surfactant assists in reducing the interfacial tension and facilitates its formation [2]. Moreover, during storage, the aggregation of the droplets is prevented as repulsive interactions are facilitated between them [3,4]. Consequently, it has become a prerequisite to exploit environment friendly surfactants, commonly known as “biosurfactants”, to stabilize the nanostructures, and to commercially benefit of the fabricated products [5–7].
Polymer dispersed liquid crystals doped with low concentration γ-Fe2O3 nanoparticles
Published in Liquid Crystals, 2021
Xiangshen Meng, Jian Li, Yueqiang Lin, Xiaodong Liu, Ningning Liu, Wenjiang Ye, Decai Li, Zhenghong He
Liquid crystals (LCs) are a typical soft matter, consisting of highly anisotropic and weakly coupled molecules [1]. Colloids are also a kind of soft matter, in which one substance of microscopic particles is suspended throughout another substance. LC colloids are formed by microscopically dispersing insoluble or soluble particles into LCs [2–5]. LC colloids were attracted considerable attention in the material field, because the interaction among the nanoparticles can induce significant changes in the LC hosts, including LC alignment, electro-optical properties, and stabilisation of the LC phase, etc [6]. The existing LC can be considered ‘pure enough’ for many applications used nowadays, however, the uncontrolled ionic contamination during the manufacturing process is still a problem. For example, free ions in LCs can cause slow response, image sticking, etc. The known investigations have shown that the use of nanotechnology can resolve the difficulties stemming from the LC contamination [7]. Nanoparticles can be incorporated into some materials because of their small particle sizes, and it was shown that nanoparticles with low concentration didn’t disturb the LC ordering, but changed its physical properties [8–10].
Study the electro-viscous effect on stability and rheological behavior of surfactant-stabilized emulsions
Published in Journal of Dispersion Science and Technology, 2018
P. Kundu, V. Kumar, I. M. Mishra
The colloids are of many classes, such as emulsion, flocculated dispersion, aggregated suspension, micelles, gels, etc., which are ubiquitous in practical applications. The rheological behavior of such colloidal suspensions becomes complex. The presence of a surfactant significantly influences the rheological behavior of colloidal suspensions. Surfactant molecules can form various layered structures. Surfactant mono-layers are also adsorbed at the oil–water interface of emulsion droplets.[1] The presence of different components are known to strongly affect the physical properties of the interfaces: stability, shape, tension, and viscoelastic behavior.[2,3] Under appropriate conditions, two surfactant layers can spontaneously experience strong attraction and adhere to each other. The adsorption and surface interactions among surfactant layers are expected to play an important role. The oil-in-water (o/w) emulsions or colloidal dispersions, which are stabilized by ionic surfactants, exhibit strong adhesion. These phenomena lead to adhesive colloidal aggregation composed of small emulsion droplets, which make it potentially useful for applications involving emulsion gels and colloidal coatings.[4] Study of the rheological behavior of such colloidal suspensions (adhesive/flocculated-aggregated suspensions) is limited and currently holds a great deal of interest.
Investigation the impact of additives on the displacement of the onset point of asphaltene precipitation using interfacial tension measurement
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2019
Amir Hosein Saeedi Dehaghani, Bahareh Keshavarz, Seyed Ali Mousavi Dehghani
In examining this phenomenon from another perspective, we look at the effect of surfactant critical micelle concentration. According to the studies conducted on surfactants, surface active molecules have a tendency towards forming colloidal associations in the solution. When a surfactant is used at a very low concentration, its dissolved molecules are dispersed within the solution in the form of monomers. Conversely, increasing the concentration drives molecules to association. However, if the surfactant concentration in the solution exceeds an amount called critical micelle concentration (CMC), adding more surfactant will cause micelle formation. At concentrations higher than CMC, the concentration of surfactant monomer does not necessarily change. In other words, the added volume at concentrations higher than CMC leads to the formation of excessive micelles; nevertheless, only a relatively slight change will occur to monomer concentration (Petrenko et al. 2010). Stabilization via dispersants known for their prevention of asphaltene precipitation and flocculation occurs at concentrations lower than CMC. Going beyond CMC restricts the number of monomer dispersant molecules and, instead of causing more changes in the characteristics of colloidal asphaltenes, stops the stabilization process, as it was observed in the experiments. This is so because critical micelle concentration of DBSA occurred at 4700 ppm, and the opposite effect of DBSA was found at 5000 ppm, i.e. a concentration greater than surfactant CMC (Hashmi and Firoozabadi 2011). Given that critical micelle concentration of CDEA is 5000 ppm, it is expected – based on the above discussion – that prior to this concentration, adding more of the substance can enhance the related preventive power, as proved in the experiments.