Direct-Imaging Cryo-SEM of Nanostructure Evolution in Didodecyldimethylammonium Bromide-Based Microemulsions

Ben‐Barak, Ido; Talmon, Yeshayahu

doi:10.1524/zpch.2012.0294

Cited by 14 publications

(17 citation statements)

References 34 publications

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“…A very clear example is imaging by cryo-SEM of the long-studied system of isooctane-DDAB-water. 173 DDAB (didodecyldimethylammonium bromide) is a double-tailed quaternary ammonium surfactant. Figure 19 shows on the left the continuous network of the water-swollen inverse threadlike micelles.…”

Section: Information From Direct Imaging By Electronmentioning

confidence: 99%

Using Microemulsions: Formulation Based on Knowledge of Their Mesostructure

et al. 2021

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Microemulsions, as thermodynamically stable mixtures of oil, water, and surfactant, are known and have been studied for more than 70 years. However, even today there are still quite a number of unclear aspects, and more recent research work has modified and extended our picture. This review gives a short overview of how the understanding of microemulsions has developed, the current view on their properties and structural features, and in particular, how they are related to applications. We also discuss more recent developments regarding nonclassical microemulsions such as surfactant-free (ultraflexible) microemulsions or ones containing uncommon solvents or amphiphiles (like antagonistic salts). These new findings challenge to some extent our previous understanding of microemulsions, which therefore has to be extended to look at the different types of microemulsions in a unified way. In particular, the flexibility of the amphiphilic film is the key property to classify different microemulsion types and their properties in this review. Such a classification of microemulsions requires a thorough determination of their structural properties, and therefore, the experimental methods to determine microemulsion structure and dynamics are reviewed briefly, with a particular emphasis on recent developments in the field of direct imaging by means of electron microscopy. Based on this classification of microemulsions, we then discuss their applications, where the application demands have to be met by the properties of the microemulsion, which in turn are controlled by the flexibility of their amphiphilic interface. Another frequently important aspect for applications is the control of the rheological properties. Normally, microemulsions are low viscous and therefore enhancing viscosity has to be achieved by either having high concentrations (often not wished for) or additives, which do not significantly interfere with the microemulsion. Accordingly, this review gives a comprehensive account of the properties of microemulsions, including most recent developments and bringing them together from a united viewpoint, with an emphasis on how this affects the way of formulating microemulsions for a given application with desired properties.

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Section: Information From Direct Imaging By Electronmentioning

confidence: 99%

Using Microemulsions: Formulation Based on Knowledge of Their Mesostructure

et al. 2021

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“…The methodology can be applied for either aqueous or nonaqueous systems’ cryo-SEM preparation. 18 When preparing cryo-SEM specimens of acid-based specimens, the CEVS is inserted into a collapsible glovebox and flushed with dry nitrogen to minimize contact between the acid and water vapor. 3 …”

Section: Specimen Preparationmentioning

confidence: 99%

“… 15 − 17 That includes oil-in-water, water-in-oil, and bicontinuous microemulsions; in the latter, both oil and water are continuous. 18 , 19 In some cases of practical importance the solvents are strong acids. Even in those extreme cases it has been possible to perform cryo-TEM and cryo-SEM, after the physics and chemistry of these systems during specimen preparation, vitrification and imaging have been studied and the methodologies have been modified to accommodate the special nature of those material systems.…”

Section: Introductionmentioning

confidence: 99%

Extending Cryo-EM to Nonaqueous Liquid Systems

Ya’akobi

Talmon

2021

Acc. Chem. Res.

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Conspectus Cryogenic-temperature transmission electron microscopy (cryo-TEM) of aqueous systems has become a widely used methodology, especially in the study of biological systems and synthetic aqueous systems, such as amphiphile and polymer solutions. Cryogenic-temperature scanning electron microscopy (cryo-SEM), while not as widely used as cryo-TEM, is also found in many laboratories of basic and applied research. The application of these methodologies, referred to collectively as cryogenic-temperature electron microscopy (cryo-EM) for direct nanostructural studies of nonaqueous liquid systems is much more limited, although such systems are important in basic research and are found in a very large spectrum of commercial applications. The study of nonaqueous liquid systems by cryo-EM poses many technical challenges. Specimen preparation under controlled conditions of air saturation around the specimen cannot be performed by the currently available commercial system, and the most effective cryogen, freezing ethane, cannot be used for most such liquid systems. Imaging is often complicated by low micrograph contrast and high sensitivity of the specimens to the electron beam. At the beginning of this Account, we describe the basic principles of cryo-EM, emphasizing factors that are essential for successful direct imaging by cryo-TEM and cryo-SEM. We discuss the peculiarities of nonaqueous liquid nanostructured systems when studied with these methodologies and how the technical difficulties in imaging nonaqueous systems, from oil-based to strong acid-based liquids, have been overcome, and the applicability of cryo-TEM and cryo-SEM has been expanded in recent years. Modern cryo-EM has been advanced by a number of instrumental developments, which we describe. In the TEM, these include improved electron field emission guns (FEGs) and microscope optics, the Volta phase plate to enhance image contrast by converting phase differences to amplitude differences without the loss of resolution by an objective lens strong underfocus, and highly sensitive image cameras that allow the recording of TEM images with minimal electron exposure. In the SEM, we take advantage of improved FEGs that allow imaging at a low (around 1 kV) electron acceleration voltage that is essential for high-resolution imaging and for avoiding specimen charging of uncoated nonconductive specimens, better optics, and a variety of sensitive detectors that have considerably improved resolution and, under the proper conditions, give excellent contrast even between elements quite close on the periodic table of the elements, such as the most important oxygen and carbon atoms. Finally we present and analyze several examples from our recent studies, which illustrate the issues presented above, including the remarkable progress made in recent years in this field and the strength and applicability of cryo-EM methodologies.

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“…% n -propanol, exhibiting about four times of the lignin solubility in comparison to that inn -propanol. In order to give an intuitionistic understanding about the droplets and micro-structures of microemulsions in the SFME system, cryogenic scanning electron microscopy (Cryo-SEM) was performed according to previous reports, 39,40 and conducted on the above microemulsion systems (points c, k and j in Figure 3) dissolving with or without lignin from different subregions. It is clear to see the existence of the discrete spherical droplets in the O/W microemulsion system containing lignin (point c in Figure 3), where the average diameter of the droplets is about 67 nm (Figure 5A and Figure S3A).…”

Section: Solubility Of Lignin In Microemulsion Systemmentioning

confidence: 99%

Oxidation of Organosolv Lignin in a Novel Surfactant-free Microemulsion Reactor

Kong¹,

Li²,

Luo³

et al. 2020

Preprint

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Lignin is considered as a promising substitute for fossil resources, but the efficient conversion of the lignin remains a huge challenge due to its structural complexity and immiscibility with typical solvents. Herein, a series of surfactant-free microemulsion reactors comprised of octane, water and n-propanol were designed and their corresponding phase behaviors alongside their ability to intensify oxidative depolymerization of lignin was explored. Experimental results show that the phenolic monomer yield improves substantially (40-500 wt.%) when the novel microemulsion systems are employed by comparison with processes performed in a single solvent. Detailed characterizations also suggest that the above intensification is rationalized by the solubilization effect of the microemulsion system, which arise as a consequence of directional aggregation of lignin at the microemulsion interface.

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Direct-Imaging Cryo-SEM of Nanostructure Evolution in Didodecyldimethylammonium Bromide-Based Microemulsions

Cited by 14 publications

References 34 publications

Using Microemulsions: Formulation Based on Knowledge of Their Mesostructure

Using Microemulsions: Formulation Based on Knowledge of Their Mesostructure

Extending Cryo-EM to Nonaqueous Liquid Systems

Oxidation of Organosolv Lignin in a Novel Surfactant-free Microemulsion Reactor

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