No abstract

Further increase in energy density of lithium batteries is needed for zero emission vehicles. However, energy density is restricted by unavoidable theoretical limits for positive electrodes used in commercial applications. One possibility towards energy densities exceeding these limits is to utilize anion (oxide ion) redox, instead of classical transition metal redox. Nevertheless, origin of activation of the oxide ion and its stabilization mechanism are not fully understood. Here we demonstrate that the suppression of formation of superoxide-like species on lithium extraction results in reversible redox for oxide ions, which is stabilized by the presence of relatively less covalent character of Mn4+ with oxide ions without the sacrifice of electronic conductivity. On the basis of these findings, we report an electrode material, whose metallic constituents consist only of 3d transition metal elements. The material delivers a reversible capacity of 300 mAh g−1 based on solid-state redox reaction of oxide ions.

In situ synthesis of noble metal (Ag, Au, Pt, Pd) nanoparticles was carried out under ambient conditions in porous cellulose fibers as nanoreactors. Particles of less than 10 nm were readily prepared using the described approach, and monodisperse nanoparticles were obtained under an optimized concentration of the metal precursor solution. The nanoporous structure and the high oxygen (ether and hydroxyl) density of the cellulose fiber constitute an effective nanoreactor for in situ synthesis of metal nanoparticles. The nanopore is essential for incorporation of metal ion and reductant into cellulose fibers as well as for removal of unnecessary byproducts from fibers. This was endorsed by negligible adsorption of metal ion onto nonporous films of poly(vinyl alcohol) and starch. The ether oxygen and the hydroxyl group not only anchor metal ions tightly in cellulose fibers via ion-dipole interactions, but they also stabilize metal nanoparticles by strong bonding interaction with their surface atoms. The preparative procedure is facile and versatile, and provides a simple route to manufacturing of useful noble metal nanoparticles.

Hybrid sol-gel materials have been a subject of intensive research during the past decades because these nanocomposites combine the versatility of organic polymers with the superior physical properties of glass. Here, we report the synthesis, by spin coating, of hybrid interpenetrating networks in the form of free-standing nanomembrane (around 35-nm thick) with unprecedented macroscopic size and characteristics. The quasi-2D interpenetration of the organic and inorganic networks brings to these materials a unique combination of properties that are not usually compatible within the same film: macroscopic robustness and homogeneity, nanoscale thickness, mechanical strength, high flexibility and optical transparency. Interestingly, such free-standing nanofilms of macroscopic size can seal large openings, are strong enough to hold amounts of liquid 70,000 times heavier than their own weight, and are flexible enough to reversibly pass through holes 30,000 times smaller than their own size.

A platform for capture and release of circulating tumor cells is demonstrated by utilizing polymer grafted silicon nanowires. In this platform, integration of ligand‐receptor recognition, nanostructure amplification, and thermal responsive polymers enables a highly efficient and selective capture of cancer cells. Subsequently, these captured cells are released upon a physical stimulation with outstanding cell viability.