The solid, hollow, and tube-in-tube porous nanofiber structures of TiO₂ are synthesized successfully by a simple non-coaxial electrospinning method without using a complicated coaxial jet head, combined with adjusting the concentration of the TiO₂ precursor and the pinhole diameter of the jet head and by final calcination. The formation mechanisms of different structured TiO₂ fibers are discussed in detail. This method is facile and effective, and easy to scale up. Furthermore, it is a versatile method for constructing tube-in-tube fibers of other metal oxides such as ZrO₂, SiO₂, SnO₂, and In₂O₃. The photocatalytic activity of tubular TiO₂ nanofibers for the degradation of 2-chlorophenol and 2,4-dichlorophenol under UV or visible-light irradiation is better than the one of commercial available TiO₂ powder, rutile, and anatase TiO₂ fibers.

This work reports a simple and effective method to prepare polyaniline (PANI) nanotubes with rectangular or circular cross section and hollow microspheres by using basic amino acids L-lysine or L-arginine as dopants and pH buffer agents, respectively. The research reveals that the pH value of the reaction solution at the beginning stage is a crucial factor to form PANI microstructures. The L-lysine and L-arginine have isoelectric point 9.74 and 10.76, which can maintain reaction solution at high pH value at the beginning reaction and assist aniline to couple in ortho-position forming phenazine unit in the oligomer chain. The oligomer produces rectangular nanorods or microspheres by interaction. These oligomer microstructures act as templates for further polymerization to form PANI rectangular nanotubes and hollow microspheres. Decreasing the concentration of the basic amino acid or using acidic amino acid, the round nanotubes are formed. This method provides a simple route to prepare PANI microstructures with different morphologies without any foreign template or surfactant, and raises a new view on the polymerization process. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

A facile and robust route for the pre-synthesized Fe₃O₄ nanoparticles (NPs) exclusively assembled on both sides of reduced graphene oxide (RGO) sheets with tunable density forming two-dimensional NPs composite membranes is developed in solution. The assembly is driven by electrostatic attraction, and the nanocomposite sheets display considerable mechanical robustness, such as it can sustain supersonic and solvothermal treatments without NPs falling off, also, can freely float in solution and curl into a tube. The obtained two-dimensional composite grain membranes exhibit superparamagnetic behavior at room temperature but responds astutely to an external magnetic field. In addition, these magnetic composite membranes show an enhanced absorption capability for microwaves. The grain sheets are attractive for biomedical, sensors, environmental applications and electric-magnetic devices benefited from large surfaces, high magnetization moment, and superparamagnetic properties. The effective integration of oxide nanocrystals on RGO sheets provides a new way to design semiconductor–carbon nanocomposites for nanodevices or catalytic applications.