Rechargeable potassium-oxygen (K-O ) batteries promise to provide higher round-trip efficiency and cycle life than other alkali-oxygen batteries with satisfactory gravimetric energy density (935 Wh kg ). Exploiting a strong electron-donating solvent, for example, dimethyl sulfoxide (DMSO) strongly stabilizes the discharge product (KO ), resulting in significant improvement in electrode kinetics and chemical/electrochemical reversibility. The first DMSO-based K-O battery demonstrates a much higher energy efficiency and stability than the glyme-based electrolyte. A universal KO growth model is developed and it is demonstrated that the ideal solvent for K-O batteries should strongly stabilize superoxide (strong donor ability) to obtain high electrode kinetics and reversibility while providing fast oxygen diffusion to achieve high discharge capacity. This work elucidates key electrolyte properties that control the efficiency and reversibility of K-O batteries.

We present a novel approach to the in situ deposition of size-controlled platinum nanoparticles on the exterior walls of carbon nanotubes (CNTs). The reduction of metal ions in ethylene glycol (EG), by the addition of a salt such as sodium dodecyl sulfate (SDS), p-CH3C6H4SO3Na, LiCF3SO3, or LiClO4, results in high dispersions and high loadings of platinum nanoparticles on CNTs without aggregation. We have performed controlled experiments to elucidate the mechanism. By exploiting the salt effect, our method effectively depresses homogeneous nucleation, leading to selective heterogeneous metal nucleation and growth, even on unmodified CNTs. In the 2.3-9.6 nm size range, the size of platinum nanoparticles, at 50% loading, can be controlled by changing the concentration of metal ions, the reaction temperature, the reducing reagent or the means by which reactive solutions are added. Our method provides a flexible route towards the preparation of novel one-dimensional hybrid materials, for which a number of promising applications in a variety of fields can be envisioned.

Injectable hydrogels have served as biomimic scaffolds that provide a three-dimensional (3D) structure for tissue engineering or carriers for cell encapsulation in the biomedical field. In this study, the injectable electroactive hydrogels (IEHs) were prepared by introducing electrical properties into the injectable materials. Carboxyl-capped tetraaniline (CTA) as functional group was coupled with enantiomeric polylactide-poly(ethylene glycol)-polylactide (PLA-PEG-PLA), and the electroactive hydrogels were obtained by mixing the enantiomeric copolymers of CTA-PLLA-PEG-PLLA-CTA and CTA-PDLA-PEG-PDLA-CTA aqueous solutions. ultraviolet-visible spectroscopy (UV-vis) and cyclic voltammetry (CV) of the complex solution showed good electroactive properties. The gelation mechanism and intermolecular multi-interactions such as stereocomplextion, hydrogen bonding, and π-π stacking were studied by Fourier transform infrared spectroscopy (FT-IR), UV-vis, and wide-angle X-ray diffraction (WAXD). Gelation properties of the complexes were also studied by rheometer. The encapsulated cells remained highly viable in the gel matrices, suggesting that the hydrogels have excellent cytocompatibility. After subcutaneous injection, the gels were formed in situ in the subcutaneous layer, and hematoxylin-eosin (H&E) staining suggested acceptable biocompatibility of our materials in vivo. Moreover, these injectable materials, when treated with pulsed electrical stimuli, were shown to be functionally active and to accelerate the proliferation of encapsulated fibroblasts, cardiomyocytes, and osteoblasts. Hence, the IEHs possessing these excellent properties would be potentially used as in vivo materials for tissue engineering scaffold.

Frustules, the silica shells of diatoms, have unique porous architectures with good mechanical strength. In recent years, biologists have learned more about the mechanism of biosilica shells formation; meanwhile, physicists have revealed their optical and microfluidic properties, and chemists have identified ways to modify them into various materials while maintaining their hierarchical structures. These efforts have provided more opportunities to use biosilica structures in microsystems and other commercial products. This review focuses on the preparation of biosilica structures and their applications, especially in the development of microdevices. We discuss existing methods of extracting biosilica from diatomite and diatoms, introduce methods of separating biosilica structures by shape and sizes, and summarize recent studies on diatom-based devices used for biosensing, drug delivery, and energy applications. In addition, we introduce some new findings on diatoms, such as the elastic deformable characteristics of biosilica structures, and offer perspectives on planting diatom biosilica in microsystems.