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Transmission electron microscopy (TEM) provides direct structural information on nano‐structured materials and is popular as a characterization tool in soft matter and supramolecular chemistry. However, technical aspects of sample preparation are overlooked and erroneous image interpretations are regularly encountered in the literature. There are three most commonly used TEM methods as we derived from literature: drying, staining and cryo‐TEM, which are explained here with respect to their application, limitations and interpretation. Since soft matter chemistry relies on a lot of indirect evidence, the role of TEM for the correct evaluation of the nature of an assembly is very large. Mistakes in application and interpretation can therefore have enormous impact on the quality of present and future studies. We provide helpful background information of these three techniques, the information that can and cannot be derived from them and provide assistance in selecting the right technique for soft matter imaging. This essay warns against the use of drying and explains why. In general cryo‐TEM is by far the best suited method and many mistakes and over‐interpretations can be avoided by the use of this technique. The most popular electron microscopy methods for soft and supramolecular systems are reviewed with respect to their possibilities and limitations. Drying is highly discouraged, because it causes unpredictable structures and artefacts. Staining preserves the structure better, but inner details are obscured. Although one should be aware of artefacts such as ice contamination, cryo‐electron microscopy is the method of choice.

Intercalation provides to the host materials a means for controlled variation of many physical/chemical properties and dominates the reactions in metal‐ion batteries. Of particular interest is the graphite intercalation compounds with intriguing staging structures, which however are still unclear, especially in their nanostructure and dynamic transition mechanism. Herein, the nature of the staging structure and evolution of the lithium (Li)‐intercalated graphite was revealed by cryogenic‐transmission electron microscopy and other methods at the nanoscale. The intercalated Li‐ions distribute unevenly, generating local stress and dislocations in the graphitic structure. Each staging compound is found macroscopically ordered but microscopically inhomogeneous, exhibiting a localized‐domains structural model. Our findings uncover the correlation between the long‐range ordered structure and short‐range domains, refresh the insights on the staging structure and transition of Li‐intercalated/deintercalated graphite, and provide effective ways to enhance the reaction kinetic in rechargeable batteries by defect engineering. The microstructure of Li+‐graphite intercalation compounds (GIC) was directly visualized by cryo‐transmission electron microscopy with minimized artifacts. Each macroscopical staging compound is a mixture of different staging phases and dislocations. It is long‐range order, medium‐range disorder, and short‐range order, which is much different from the previously proposed Rüdorff‐Hofmann and Daumas‐Hérold models. Localized‐domains model is proposed to describe the real structural nature of the Li+‐GIC.

HighlightsThe microstructure of graphite upon rapid Li+ intercalation is a mixture of differently staging structures in the macroscopic and microscopic scales due to the incomplete and inhomogeneous intercalation reactions hindered by the sluggish reaction kinetics.The Li+ interface diffusion dominates the reaction kinetics at high rates in thin graphite electrode, while Li+ diffusion through the electrode cannot to be neglected for thick graphite electrode.Fast-charging lithium-ion batteries are highly required, especially in reducing the mileage anxiety of the widespread electric vehicles. One of the biggest bottlenecks lies in the sluggish kinetics of the Li+ intercalation into the graphite anode; slow intercalation will lead to lithium metal plating, severe side reactions, and safety concerns. The premise to solve these problems is to fully understand the reaction pathways and rate-determining steps of graphite during fast Li+ intercalation. Herein, we compare the Li+ diffusion through the graphite particle, interface, and electrode, uncover the structure of the lithiated graphite at high current densities, and correlate them with the reaction kinetics and electrochemical performances. It is found that the rate-determining steps are highly dependent on the particle size, interphase property, and electrode configuration. Insufficient Li+ diffusion leads to high polarization, incomplete intercalation, and the coexistence of several staging structures. Interfacial Li+ diffusion and electrode transportation are the main rate-determining steps if the particle size is less than 10 μm. The former is highly dependent on the electrolyte chemistry and can be enhanced by constructing a fluorinated interphase. Our findings enrich the understanding of the graphite structural evolution during rapid Li+ intercalation, decipher the bottleneck for the sluggish reaction kinetics, and provide strategic guidelines to boost the fast-charging performance of graphite anode.

Cryogenic transmission electron microscopy (cryo‐TEM) has impacted biology and materials science profoundly due to its power in studying aqueous specimens. However, it remains challenging to extend this technique to organic solvent systems as organic solvents are often difficult to vitrify and are unstable under electron beams. Here, we studied the response of the 23 most commonly used organic solvents to vitrification and electron exposure in cryo‐TEM experiments. Optimized vitrification method was determined for each of the solvents, and the electron tolerances of the solvents were thoroughly measured using high‐resolution imaging. Generic rules underlying the different performances of the solvents were discussed. Based on the rules, methods were developed to enhance the electron exposure stability of the organic solvents. Our results provide guidance for optimizing cryo‐TEM experiments on organic solvent specimens. To better perform cryo‐TEM experiments on organic solvent systems, this work studied the response of 23 common organic solvents to vitrification and electron exposure, listed optimized sample preparation conditions, and developed methods to enhance the electron tolerance of the samples.

Ion exchange in nanoporous clay-rich media plays an integral role in water, nutrient, and contaminant storage and transport. In montmorillonite (MMT), a common clay mineral in soils, sediments, and muds, the swelling and collapse of clay particles through the addition or removal of discrete molecular layers of water alters cation exchange selectivities in a poorly understood way. Here, we show that ion exchange is coupled to the dynamic delamination and restacking of clay layers, which creates a feedback between the hydration state of the exchanging cation and the composition of the clay interlayer. Particles with different hydration states are distinct phases with unique binding selectivities. Surprisingly, equilibrium achieved through thermal fluctuations in cation concentration and hydration state leads to the exchange of both ions and individual MMT layers between particles, a process we image directly with high-resolution transmission electron microscopy at cryogenic conditions (cryo-TEM). We introduce an exchange model that accounts for the binding selectivities of different phases, which is likely applicable to many charged colloidal or macromolecular systems in which the structural conformation is correlated with the activities of water and counterions within spatially confined compartments.

Rational design of supramolecular nanomaterials fundamentally depends upon an atomic-level understanding of their structure and how it responds to chemical modifications. Here we studied a series of crystalline diblock copolypeptoids by a combination of sequence-controlled synthesis, cryogenic transmission electron microscopy, and molecular dynamics simulation. This family of amphiphilic polypeptoids formed free-floating 2-dimensional monolayer nanosheets, in which individual polymer chains and their relative orientations could be directly observed. Furthermore, bromine atom side-chain substituents in nanosheets were directly visualized by cryogenic transmission electron microscopy, revealing atomic details in position space inaccessible by conventional scattering techniques. While the polypeptoid backbone conformation was conserved across the set of molecules, the nanosheets exhibited different lattice packing geometries dependent on the aromatic side chain para substitutions. Peptoids are inherently achiral, yet we showed that sequences containing an asymmetric aromatic substitution pattern pack with alternating rows adopting opposite backbone chiralities. These atomic-level insights into peptoid nanosheet crystal structure provide guidance for the future design of bioinspired nanomaterials with more precisely controlled structures and properties.

The declining birth rates and fertility challenges in Europe have intensified global concerns over rising infertility, particularly among women. This study decisively investigates follicular fluid‐related extracellular vesicles (FF‐EVs) from infertile patients with polycystic ovary syndrome (PCOS) or diminished ovarian reserve (DOR) undergoing in vitro fertilization (IVF), comparing them to a healthy control group. We have identified significant variations in protein content and polydispersity in crude follicular fluid using UV‐Vis absorption and dynamic light scattering (DLS) techniques. Furthermore, the morphology of the extracellular vesicles (EVs) and the patterns of non‐coding RNA content, including miRNAs, reveal distinct differences in infertile patients. These findings offer critical insights into the molecular signatures associated with these conditions. This study plays a vital role in advancing reproductive healthcare by pinpointing potential targets that can enhance diagnosis and deepen our understanding of ovarian disorders.

Ion exchange in nanoporous clay-rich media plays an integral role in water, nutrient, and contaminant storage and transport. In montmorillonite (MMT), a common clay mineral in soils, sediments, and muds, the swelling and collapse of clay particles through the addition or removal of discrete molecular layers of water alters cation exchange selectivities in a poorly understood way. Here, we show that ion exchange is coupled to the dynamic delamination and restacking of clay layers, which creates a feedback between the hydration state of the exchanging cation and the composition of the clay interlayer. Particles with different hydration states are distinct phases with unique binding selectivities. Surprisingly, equilibrium achieved through thermal fluctuations in cation concentration and hydration state leads to the exchange of both ions and individual MMT layers between particles, a process we image directly with high-resolution transmission electron microscopy at cryogenic conditions (cryo-TEM). Finally, we introduce an exchange model that accounts for the binding selectivities of different phases, which is likely applicable to many charged colloidal or macromolecular systems in which the structural conformation is correlated with the activities of water and counterions within spatially confined compartments.

The field of energy storage and conversion materials has witnessed transformative advancements owing to the integration of advanced in situ characterization techniques. Among them, numerous real-time characterization techniques, especially in situ transmission electron microscopy (TEM)/scanning TEM (STEM) have tremendously increased the atomic-level understanding of the minute transition states in energy materials during electrochemical processes. Advanced forms of in situ/operando TEM and STEM microscopic techniques also provide incredible insights into material phenomena at the finest scale and aid to monitor phase transformations and degradation mechanisms in lithium-ion batteries. Notably, the solid–electrolyte interface (SEI) is one the most significant factors that associated with the performance of rechargeable batteries. The SEI critically controls the electrochemical reactions occur at the electrode–electrolyte interface. Intricate chemical reactions in energy materials interfaces can be effectively monitored using temperature-sensitive in situ STEM techniques, deciphering the reaction mechanisms prevailing in the degradation pathways of energy materials with nano- to micrometer-scale spatial resolution. Further, the advent of cryogenic (Cryo)-TEM has enhanced these studies by preserving the native state of sensitive materials. Cryo-TEM also allows the observation of metastable phases and reaction intermediates that are otherwise challenging to capture. Along with these sophisticated techniques, Focused ion beam (FIB) induction has also been instrumental in preparing site-specific cross-sectional samples, facilitating the high-resolution analysis of interfaces and layers within energy devices. The holistic integration of these advanced characterization techniques provides a comprehensive understanding of the dynamic changes in energy materials. This review highlights the recent progress in employing state-of-the-art characterization techniques such as in situ TEM, STEM, Cryo-TEM, and FIB for detailed investigation into the structural and chemical dynamics of energy storage and conversion materials.