A general acid vapor oxidation (AVO) strategy has been developed to grow highly oriented hierarchically structured rutile TiO(2) nanoarrays with tunable morphologies from titanium thin films. This is a simple one-pot synthesis approach involving the reaction of a titanium surface with the vapor generated from a hydrochloric acid solution in a Teflon lined autoclave. To the best of our knowledge, this is the first successful attempt to grow ordered tree-like titania nanoarrays. A possible formation mechanism for the interesting architectures has been proposed based on series of time-dependent experiments. By adjusting the initial HCl concentration, films of different rutile structures including nanotrees, dendritic nanobundles, and nanorods can be selectively obtained. Subsequently, the surface morphologies and wettability can be readily tuned.

No abstract

The development of pure organic magnets with high Curie temperatures remains a challenging task in material science. Introducing high‐density free radicals to strongly interacting organic molecules may be an effective method to this end. In this study, a solvothermal approach with excess hydrazine hydrate is used to concurrently reduce and dissolve rigid‐backbone perylene diimide (PDI) crystallites into the soluble dianion species with a remarkably high reduction potential. The as‐prepared PDI powders comprising radical anion aggregates are fabricated by a subsequent self‐assembly and spontaneous oxidation process. The results of magnetic measurements show that the PDI powders exhibit room‐temperature ferromagnetism and a Curie temperature higher than 400 K, with a vast saturation magnetization that reaches ≈1.2 emu g−1. Elemental analysis along with the diamagnetic signal of the ablated residue are used to rule out the possibility that the magnetism is due to metal contamination. The findings suggest that the long‐range ferromagnetic ordering can survive at room‐temperature in organic semiconductors, and offers a new optional way to create room‐temperature magnetic semiconductors.

By controlling the time to apply magnetic field to a Fe3O4 magnetic fluid with polymer acrylic resin and by evaporating the solvent, linear chain-like structures were obtained and fixed. Optical microscopy and transmission electronic microscopy (TEM) were used to observe the assembly structures of the fixed magnetic nanoparticles. We found that the chainlike structures with size even down to hundreds nanometers had smaller substructures. A picture of aggregation between linear chain-like substructures is proposed to understand the formation of the macrostructure in magnetic fluid induced by a magnetic field. Two basic aggregations, the coarsening and the connection of the substructures, were observed.

No abstract