A carbon sandwich environmental cell for wet specimens

Fiber-optic sample illuminator design for the observation of light induced phenomena with transmission electron microscopy in situ: Antimicrobial photodynamic therapy

Antibacterial photodynamic therapy is a promising treatment for problematic infections caused by bacteria and fungi. Despite its undoubted effectiveness, the ultrastructural mechanism of microbial death remains not fully described and distinct organisms respond to the treatment with different efficacy. For this reason, it was decided to try imaging the process using the in situ transmission electron microscopy method. To conduct an observational experiment, the microscope was significantly modified. Liquid cell methods were used, electron doses and their influence on the sample were estimated, and a fiber-optic sample illuminator was designed and built. The modifications allowed for the light-induced characterization of photosensitizer-bacteria interaction. Microscope modification is a promising platform for further studies of light-induced phenomena in both life and material science.

Investigation of hydrated smectite microstructure through wet environmental transmission electron microscopy

Water is an essential constituent of all biological materials as well as many non-biological materials. Not only the removal of water may result in undesirable morphological and structure change, the inability to sustain the hydrated conditions in the microscope also prevents the study of reactions which take place in aqueous environment. In order to overcome these problems we used wet environmental-cell transmission electron microscopy TEM (WETEM). Conventional TEM of dry smectite showed well-defined particle outlines (but without a specific shape) and typical smectite aggregates. Selected area electron diffraction (SAD) of dry particles showed stacking of smectite particles (i.e., aggregate) in very clear dot and ring patterns. In contrast, WETEM depicted well-dispersed clay particles showing a variety of different particle shapes. Analysis of SAD patterns obtained from dry and hydrated states illustrated a lattice change in different environments. The small lattice expansion in (h k 0) resulted from the expansion of the (0 0 l) plane resulting from the addition of water molecules in the crystal along the c-axis.

Contrast enhancement of nanomaterials using phase plate STEM

Visualizing materials composed of light elements is difficult, and the development of an imaging method that enhances the phase contrast of such materials has been of much interest. In this study, we demonstrate phase-plate scanning transmission electron microscopy (P-STEM), which we developed recently, and its application to nanomaterials. An amorphous carbon film with a small hole in its center was used to control the phase of incident electron waves, and the phase-contrast transfer function (PCTF) was modified from sine-type to cosine-type. The modification of the PCTF enhances image contrast with a spatial frequency below 1 nm^-1. The PCTF for P-STEM with a spatial frequency below 1 nm^-1 is about three times stronger than that of bright field STEM. The ratio obtained using power spectra is consistent with the result obtained from images of quantum dots. The image contrast of biological materials was also enhanced by P-STEM.

Nanocuvette: A Functional Ultrathin Liquid Container for Transmission Electron Microscopy

Advances in TEM techniques have spurred a renewed interest in a wide variety of research fields. A rather recent track within these endeavors is the use of TEM for in situ imaging in liquids. In this article, we show the fabrication of a liquid cell for TEM observations which we call the nanocuvette. The structure consists of a nanohole film sandwiched by carbon films, sealing liquid in the holes. The hole film can be produced using a variety of materials, tailored for the desired application. Since the fabrication is based on self-assembly, it is both cheap and straightforward. Compared to previously reported liquid cells, this structure allows for thinner liquid layers with better controlled cell structures, making it possible to achieve a high resolution even at lower acceleration voltages and electron doses. We demonstrate a resolution corresponding to an information transfer up to ∼2 nm at 100 kV for molecular imaging. Apart from the advantages arising from the thin liquid layer, the nanocuvette also enables the possibility to study liquid-solid interfaces at the side walls of the nanoholes. We illustrate the possibilities of the nanocuvette by studying several model systems: electron beam induced growth dynamics of silver nanoparticles in salt solution, polymer deposition from solution, and imaging of nonstained antibodies in solution. Finally, we show how the inclusion of a plasmonically active gold layer in the nanocuvette structure enables optical confirmation of successful liquid encapsulation prior to TEM studies. The nanocuvette provides an easily fabricated and flexible platform which can help further the understanding of reactions, processes, and conformation of molecules and atoms in liquid environments.