Natural and synthetic nanoparticles composed of fivefold twinned crystal domains have distinct properties. The formation mechanism of these fivefold twinned nanoparticles is poorly understood. We used in situ high-resolution transmission electron microscopy combined with molecular dynamics simulations to demonstrate that fivefold twinning occurs through repeated oriented attachment of ~3-nanometer gold, platinum, and palladium nanoparticles. We discovered two different mechanisms for forming fivefold twinned nanoparticles that are driven by the accumulation and elimination of strain. This was accompanied by decomposition of grain boundaries and the formation of a special class of twins with a net strain of zero. These observations allowed us to develop a quantitative picture of the twinning process. The mechanisms provide guidance for controlling twin structures and morphologies across a wide range of materials.

The precise and highly efficient drug delivery of nanomedicines into lesions remains a critical challenge in clinical translational research. Here, an autocatalytic morphology transformation platform is presented for improving the tumor-specific accumulation of drugs by kinetic control. The in situ reorganization of prodrug from nanoparticle to β-sheet fibrous structures for targeted accumulation is based on nucleation-based growth kinetics. During multiple administrations, the autocatalytic morphology transformation can be realized for skipping slow nucleating process and constructing the bulky nanoassembly instantaneously, which has been demonstrated to induce the cumulative effect of prodrug. Furthermore, the sustained drug release from fibrous prodrug depot in the tumor site inhibits the tumor growth efficiently. The autocatalytic morphology transformation strategy in vivo offers a novel perspective for targeted delivery strategy by introducing chemical kinetics and shows great potential in disease theranostics.

Large areas of centimeters-long SiC nanowires have been prepared by pyrolysis of a polymer precursor with ferrocene as the catalyst by a CVD route. The nanowires, with lengths of several centimeters and diameters of 100−200 nm, were composed of single-crystal β-SiC along the ⟨111⟩ direction and were grown on ceramic substrates in areas of 11 cm × 4 cm. At high temperature, the silane fragments derived from decomposition of the polymer precursor, liquid polysilacarbosilane (l-PS), provided both the Si and C sources for the growth of the nanowires. The nanowires grew in a base-growth mode, which was governed by the Vapor−Liquid−Solid mechanism. The SiC nanowires showed good intense-current emitting properties when a pulsed high-voltage electric field was imposed.