Cryogenic transmission electron microscopy is simply transmission electron microscopy conducted on specimens that are cooled in the microscope. The target temperature of the specimen might range from just below ambient temperature to less than 4 K. In general, as the temperature decreases, cost increases, especially below –77°C when liquid He is required. We have two reasons for wanting to cool the specimen—improving stability of the material or observing a material whose properties change at lower temperatures. Both types of study have a long history. The cause of excitement in this field today is that we have a perfect storm of research activity—electron microscopes are almost stable with minimal drift (we can correct what drift there is), we can prepare specimens from the bulk or build them up, we have spherical-aberration-corrected lenses and monochromated beams, we have direct-electron-detector cameras, and computers are becoming powerful enough to handle all the data we produce.

Soft matter has historically been an unlikely candidate for investigation by electron microscopy techniques due to damage by the electron beam as well as inherent instability under a high vacuum environment. Characterization of soft matter has often relied on ensemble-scattering techniques. The recent development of cryogenic transmission electron microscopy (cryo-TEM) provides the soft matter community with an exciting opportunity to probe the structure of soft materials in real space. Cryo-TEM reduces beam damage and allows for characterization in a native, frozen-hydrated state, providing direct visual representation of soft structure. This article reviews cryo-TEM in soft materials characterization and illustrates how it has provided unique insights not possible by traditional ensemble techniques. Soft matter systems that have benefited from the use of cryo-TEM include biological-based “soft” nanoparticles (e.g., viruses and conjugates), synthetic polymers, supramolecular materials as well as the organic–inorganic interface of colloidal nanoparticles. Many challenges remain, such as combining structural and chemical analyses; however, the opportunity for soft matter research to leverage newly developed cryo-TEM techniques continues to excite.

The recent success of electron cryomicroscopy in biology has drawn the attention of the materials science community, which is starting to employ similar techniques for imaging a wide variety of nonbiological specimens. This article reviews the theory and practical implications of radiation damage in electron microscopy, and then considers how electron cryomicroscopy techniques may be applied to other radiation-sensitive specimens of interest to materials scientists. We also discuss aspects of radiation damage that warrant further study as instrumentation technology advances and consider new methods that might be useful in the future.

Until recently, mesoporous silica (MPS) particles have been successfully used in various biomedical applications including drug delivery. In the past decades, the research on MPS shifted sharply to gene delivery owing to its biocompatible, mesoporous structure that allows for loading oligonucleotides, shielding in the bloodstream, and delivering them to patient cells’ cytoplasm to stop cells’ genetic transcription. Until now, researchers faced several unique challenges and MPS, as oligonucleotide vectors, could not reach the clinical stage. In this study, material-related challenges were endeavored to overcome by a combined particle synthesis/oligo-loading strategy. DNA-encapsulated silica/polyethylene glycol (PEG) hybrid xerogels were synthesized at one step, via sol–gel technique. The xerogels were grinded into particles and characterized by X-ray diffraction, scanning electron microscopy, ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy, and gas adsorption analysis. The results demonstrated that uniform oligo-loaded silica/PEG hybrid xerogels could be synthesized without surface modification. Oligonucleotides were encapsulated inside the whole porous network, rather than attached only to particle surfaces as such in the conventional route. The results showed that PEG incorporation led to formation of monolithic xerogels, which could be grinded into spherical particles (557 ± 110 nm) with well-defined edges. Due to grinding, PEG chains were present both in the interior and on the surface of the particles. 10% PEG incorporation into silica precursor (tetraethyl orthosilicate) increased the resistance of DNA-encapsulated silica against protein degradation. In the overall sol–gel-derived silica/PEG hybrid materials were revealed as potential candidates for gene delivery applications such as RNA interference therapies.

Perovskite chalcogenides are gaining substantial interest as an emerging class of semiconductors for optoelectronic applications. High-quality samples are of vital importance to examine their inherent physical properties. We report the successful crystal growth of the model system, BaZrS3 and its Ruddlesden–Popper phase Ba3Zr2S7 by a flux method. X-ray diffraction analyses showed the space group of Pnma with lattice constants of a = 7.056(3) Å, b = 9.962(4) Å, and c = 6.996(3) Å for BaZrS3 and P42/mnm with a = 7.071(2) Å, b = 7.071(2) Å, and c = 25.418(5) Å for Ba3Zr2S7. Rocking curves with full width at half maximum of 0.011° for BaZrS3 and 0.027° for Ba3Zr2S7 were observed. Pole figure analysis, scanning transmission electron microscopy images, and electron diffraction patterns also establish the high quality of the grown crystals. The octahedral tilting in the corner-sharing octahedral network is analyzed by extracting the torsion angles.

A series of xLiMn0.5Fe0.5PO4–yLi3V2(PO4)3/C (x:y= 4:1, 3:1, 2:1, 1:1, 1:2, and 1:3) composite cathode materials for lithium-ion batteries are successfully prepared by the rheological phase reaction method. The structures, morphologies, and electrochemical properties of these composite materials are studied. The results indicate that xLiMn0.5Fe0.5PO4–yLi3V2(PO4)3/C composites are composed of LiMn0.5Fe0.5PO4 and Li3V2(PO4)3 phases and mutual doping exists. The initial discharge capacities, initial Coulombic efficiencies, and capacity retentions of composites increase but then decline with the increase of Li3V2(PO4)3 content. All the composites show higher capacity retentions than LiMn0.5Fe0.5PO4/C and Li3V2(PO4)3/C single phases except LMFP–3LVP/C. The composite material of x:y= 1:1 exhibits remarkably superior electrochemical performance than the single phases and other composites both in discharge capacity and cycle performance, delivering the initial discharge capacity of 148.2 mA h/g (2.0–4.5 V) and 170.1 mA h/g (2.0–4.8 V) at 0.1 C. And the corresponding capacity retentions are 98.0 and 90.4% after 100 cycles, respectively.

The phase evolution of reactive radio frequency (RF) magnetron sputtered Cr0.28Zr0.10O0.61 coatings has been studied by in situ synchrotron X-ray diffraction during annealing under air atmosphere and vacuum. The annealing in vacuum shows t-ZrO2 formation starting at ∼750–800 °C, followed by decomposition of the α-Cr2O3 structure in conjunction with bcc-Cr formation, starting at ∼950 °C. The resulting coating after annealing to 1140 °C is a mixture of t-ZrO2, m-ZrO2, and bcc-Cr. The air-annealed sample shows t-ZrO2 formation starting at ∼750 °C. The resulting coating after annealing to 975 °C is a mixture of t-ZrO2 and α-Cr2O3 (with dissolved Zr). The microstructure coarsened slightly during annealing, but the mechanical properties are maintained, with no detectable bcc-Cr formation. A larger t-ZrO2 fraction compared with α-Cr2O3 is observed in the vacuum-annealed coating compared with the air-annealed coating at 975 °C. The results indicate that the studied pseudo-binary oxide is more stable in air atmosphere than in vacuum.