Abstract:Water is a critical component for both function and structure of soft matter and it is what bestows the adjective soft. Imaging samples in liquid state is thus paramount to gathering structural and dynamical information of any soft materials. Herein we propose the use of liquid phase electron microscopy to expand ultrastructural analysis into dynamical investigations. We imaged two soft matter examples: a polymer micelle and a protein in liquid phase using transmission electron microscopy and demonstrate that … Show more
“…As it follows from Table 2 presenting the in situ TEM solutions from Protochips and DENSsolutions the scope of the conditions for in situ TEM observations is very wide. Thus, employing the liquid or gas TEM holders allows the detailed investigation of wet samples or even the samples in liquid (e.g., water or buffer solution with a given pH) and gas media [174][175][176][177][178][179][180]. For example, in situ TEM could be used to image bacteria and the process of their tellurite reduction with no significant damage neither from the sealing nor from the electron beam [181].…”
Section: Advantages and Limitations Of Electron Microscopymentioning
Halloysite is a tubular clay nanomaterial of the kaolin group with a characteristic feature of oppositely charged outer and inner surfaces, allowing its selective spatial modification. The natural origin and specific properties of halloysite make it a potent material for inclusion in biopolymer composites with polysaccharides, nucleic acids and proteins. The applications of halloysite/biopolymer composites range from drug delivery and tissue engineering to food packaging and the creation of stable enzyme-based catalysts. Another important application field for the halloysite complexes with biopolymers is surface coatings resistant to formation of microbial biofilms (elaborated communities of various microorganisms attached to biotic or abiotic surfaces and embedded in an extracellular polymeric matrix). Within biofilms, the microorganisms are protected from the action of antibiotics, engendering the problem of hard-to-treat recurrent infectious diseases. The clay/biopolymer composites can be characterized by a number of methods, including dynamic light scattering, thermo gravimetric analysis, Fourier-transform infrared spectroscopy as well as a range of microscopic techniques. However, most of the above methods provide general information about a bulk sample. In contrast, the combination of electron microscopy with energy-dispersive X-ray spectroscopy allows assessment of the appearance and composition of biopolymeric coatings on individual nanotubes or the distribution of the nanotubes in biopolymeric matrices. In this review, recent contributions of electron microscopy to the studies of halloysite/biopolymer composites are reviewed along with the challenges and perspectives in the field.
“…As it follows from Table 2 presenting the in situ TEM solutions from Protochips and DENSsolutions the scope of the conditions for in situ TEM observations is very wide. Thus, employing the liquid or gas TEM holders allows the detailed investigation of wet samples or even the samples in liquid (e.g., water or buffer solution with a given pH) and gas media [174][175][176][177][178][179][180]. For example, in situ TEM could be used to image bacteria and the process of their tellurite reduction with no significant damage neither from the sealing nor from the electron beam [181].…”
Section: Advantages and Limitations Of Electron Microscopymentioning
Halloysite is a tubular clay nanomaterial of the kaolin group with a characteristic feature of oppositely charged outer and inner surfaces, allowing its selective spatial modification. The natural origin and specific properties of halloysite make it a potent material for inclusion in biopolymer composites with polysaccharides, nucleic acids and proteins. The applications of halloysite/biopolymer composites range from drug delivery and tissue engineering to food packaging and the creation of stable enzyme-based catalysts. Another important application field for the halloysite complexes with biopolymers is surface coatings resistant to formation of microbial biofilms (elaborated communities of various microorganisms attached to biotic or abiotic surfaces and embedded in an extracellular polymeric matrix). Within biofilms, the microorganisms are protected from the action of antibiotics, engendering the problem of hard-to-treat recurrent infectious diseases. The clay/biopolymer composites can be characterized by a number of methods, including dynamic light scattering, thermo gravimetric analysis, Fourier-transform infrared spectroscopy as well as a range of microscopic techniques. However, most of the above methods provide general information about a bulk sample. In contrast, the combination of electron microscopy with energy-dispersive X-ray spectroscopy allows assessment of the appearance and composition of biopolymeric coatings on individual nanotubes or the distribution of the nanotubes in biopolymeric matrices. In this review, recent contributions of electron microscopy to the studies of halloysite/biopolymer composites are reviewed along with the challenges and perspectives in the field.
“…Dynamic processes such as nanoparticle growth [89], crystallization [90,91] and some biological processes [92] have been captured by this technology. Recently, the so-called four-dimensional liquid cell TEM has been shown to enable single particle reconstruction of the three-dimensional morphology of the iron storage protein ferritin in water [93] and even the structure of water itself has been probed by (vibrational) EELS of water encapsulated between two sheets of boron nitride [94]. Figure 8Schematic of typical liquid phase TEM holder ( a ) and cell ( b ).…”
We review the use of transmission electron microscopy (TEM) and associated techniques for the analysis of beam-sensitive materials and complex, multiphase systems
in-situ
or close to their native state. We focus on materials prone to damage by radiolysis and explain that this process cannot be eliminated or switched off, requiring TEM analysis to be done within a dose budget to achieve an optimum dose-limited resolution. We highlight the importance of determining the damage sensitivity of a particular system in terms of characteristic changes that occur on irradiation under both an electron fluence and flux by presenting results from a series of molecular crystals. We discuss the choice of electron beam accelerating voltage and detectors for optimizing resolution and outline the different strategies employed for low-dose microscopy in relation to the damage processes in operation. In particular, we discuss the use of scanning TEM (STEM) techniques for maximizing information content from high-resolution imaging and spectroscopy of minerals and molecular crystals. We suggest how this understanding can then be carried forward for
in-situ
analysis of samples interacting with liquids and gases, provided any electron beam-induced alteration of a specimen is controlled or used to drive a chosen reaction. Finally, we demonstrate that cryo-TEM of nanoparticle samples snap-frozen in vitreous ice can play a significant role in benchmarking dynamic processes at higher resolution.
This article is part of a discussion meeting issue ‘Dynamic
in situ
microscopy relating structure and function’.
“…Such direct observation of emulsification via the ouzo effect has never been achieved before on the nanoscale and is only possible through liquid phase transmission electron microscopy (LPTEM) techniques. LPTEM is a nascent in situ microscopy technique which hermetically encapsulates picoliters of liquid sample against the vacuum environment of the microscope, allowing direct observation of solvated samples without fixation at unprecedented spatiotemporal resolutions. − Notable advances in the understanding of nucleation and growth pathways, ,,− crystallization, − nanoparticle behavior, − self-assembly processes, − thermoresponsive materials, , and liquid–liquid phase separation − have been achieved via LPTEM since its inception. One of the unique benefits of LPTEM for the study of liquid systems is that the contrast is directly proportional to the densities of the materials being studied.…”
Herein, we present the direct observation via liquidphase transmission electron microscopy (LPTEM) of the nucleation and growth pathways of structures formed by the so-called "ouzo effect", which is a classic example of surfactant-free, spontaneous emulsification. Such liquid−liquid phase separation occurs in ternary systems with an appropriate cosolvent such that the addition of the third component extracts the cosolvent and makes the other component insoluble. Such droplets are homogeneously sized, stable, and require minimal energy to disperse compared to conventional emulsification methods. Thus, ouzo precipitation processes are an attractive, straightforward, and energy-efficient technique for preparing dispersions, especially those made on an industrial scale. While this process and the resulting emulsions have been studied by numerous indirect techniques (e.g., X-ray and light scattering), direct observation of such structures and their formation at the nanoscale has remained elusive. Here, we employed the nascent technique of LPTEM to simultaneously evaluate droplet growth and nanostructure. Observation of such emulsification and its rate dependence is a promising indication that similar LPTEM methodologies may be used to investigate emulsion formation and kinetics.
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