Rapid, High-Temperature, In Situ Microwave Synthesis of Bulk Nanocatalysts.

Carbon-black-supported nanoparticles (CNPs) have attracted considerable attention for their intriguing catalytic properties and promising applications. The traditional liquid synthesis of CNPs commonly involves demanding operation conditions and complex pre- or post-treatments, which are time consuming and energy inefficient. Herein, a rapid, scalable, and universal strategy is reported to synthesize highly dispersed metal nanoparticles embedded in a carbon matrix via microwave irradiation of carbon black with preloaded precursors. By optimizing the amount of carbon black, the microwave absorption is dramatically improved while the thermal dissipation is effectively controlled, leading to a rapid temperature increase in carbon black, ramping to 1270 K in just 6 s. The whole synthesis process requires no capping agents or surfactants, nor tedious pre- or post-treatments of carbon black, showing tremendous potential for mass production. As a proof of concept, the synthesis of ultrafine Ru nanoparticles (≈2.57 nm) uniformly embedded in carbon black using this microwave heating technique is demonstrated, which displays remarkable electrocatalytic performance when used as the cathode in a Li-O2 battery. This microwave heating method can be extended to the synthesis of other nanoparticles, thereby providing a general methodology for the mass production of carbon-supported catalytic nanoparticles.

Hierarchical nanoporous glass with antireflectivity and superhydrophilicity by one-pot etching.

We have developed a hierarchical nanoporous layer (HNL) on silicate glass by a simple one-pot etching method. The HNL has a three-dimensionally continuous spongelike structure with a pore size of a few tens of nanometers on its apparent surface. The pore size gradually decreases from the apparent surface to the HNL-bulk interface. This HNL bestows significant properties to glass: low optical reflectivity that reflects 7% less visible light than nontreated glass and long-persistence superhydrophilicity that keeps its water contact angle at about 5° for more than 1 year. The superhydrophilicity also realizes antifogging and antifouling functionalities.

A cryo-TSEM with temperature cycling capability allows deep sublimation of ice to uncover fine structures in thick cells.

The scanning electron microscope (SEM) has been reassembled into a new type of cryo-electron microscope (cryo-TSEM) by installing a new cryo-transfer holder and anti-contamination trap, which allowed simultaneous acquisition of both transmission images (STEM images) and surface images (SEM images) in the frozen state. The ultimate temperatures of the holder and the trap reached - 190 °C and - 210 °C, respectively, by applying a liquid nitrogen slush. The STEM images at 30 kV were comparable to, or superior to, the images acquired with conventional transmission electron microscope (100 kV TEM) in contrast and sharpness. The unroofing method was used to observe membrane cytoskeletons instead of the frozen section and the FIB methods. Deep sublimation of ice surrounding unroofed cells by regulating temperature enabled to emerge intracellular fine structures in thick frozen cells. Hence, fine structures in the vicinity of the cell membrane such as the cytoskeleton, polyribosome chains and endoplasmic reticulum (ER) became visible. The ER was distributed as a wide, flat structure beneath the cell membrane, forming a large spatial network with tubular ER.

Voltage contrast imaging with energy filtered signal in a field-emission scanning electron microscope.

A new band-pass energy filter (BPF) technique of secondary electron (SE) detection using scanning electron microscope (SEM) was developed to enhance voltage contrast (VC) in SEM images. The energy filtering condition was optimized to enhance VC of dopant distribution using Si p-n structure. The relation between VC and SE energy was investigated by BPF as well as a conventional high-pass filter (HPF). Whereas the p-type regions were always brighter than the n-type region in the case of HPF, the contrast reversal between p region and n region occurred at the low SE energy range in the case of BPF. The variation of signal intensity of BPF against specimen bias voltage can be considered as SE spectrum analysis, and the peak split of the spectra between n-type and p-type regions was obtained. The peak split can be explained with a model with metal-semiconductor contact. This peak split causes the contrast reversal.

Lattice imaging at an accelerating voltage of 30kV using an in-lens type cold field-emission scanning electron microscope.

We reported investigation of lattice resolution imaging using a Hitachi SU9000 conventional in-lens type cold field emission scanning electron microscope without an aberration corrector at an accelerating voltage of 30kV and discuss the electron optics and optimization of observation conditions for obtaining lattice resolution. It is possible to visualize lattice spacings that are much smaller than the diameter of the incident electron beam through the influence of the superior coherent performance of the cold field emission electron source. The defocus difference between STEM imaging and lattice imaging is found to increase with spherical aberration but it is possible to reduce the spherical aberration by reducing the focal length (f) of the objective lens combined with an experimental sample stage enabling a shorter distance between the objective lens pre-field and the sample. We demonstrate that it is possible to observe the STEM image and crystalline lattice simultaneously. STEM and Fourier transform images are detected for Si{222} lattice fringes and reflection spots, corresponding to 0.157nm. These results reveal the potential and possibility for a measuring technique with excellent precision as a theoretically exact dimension and established the ability to perform high precision measurements of crystal lattices for the structural characterization of semiconductor materials with minimal radiation beam damage.