Mass production of ZnO nanowires, nanoribbons, and needle-like rods has been achieved by a simple method of thermal evaporation of ZnO powders mixed with graphite. Metallic catalysts, carrying gases, and vacuum conditions are not necessary. Temperature is the critical experimental parameter for the formation of different morphologies of ZnO nanostructures. Zn or Zn suboxide plays a crucial role for the nucleation of ZnO nanostructures. The as-prepared ZnO nanowires consist of single crystalline cores and thin amorphous shells. As determined by electron diffraction, the growth direction of ZnO nanowires is [001], which has no orientation relationship with the substrate. A strong room-temperature photoluminescence in ZnO nanostructures has been demonstrated.

Transmission electron microscopic observation showed that TiO2 nanotubes synthesized via a simple hydrothermal chemical process formed a crystalline structure with open-ended and multiwall morphologies. Unlike multiwalled carbon nanotubes, the TiO2 nanotube walls were not seamless. During alkali treatment, crystalline TiO2 raw material underwent delamination in the alkali solution to produce single-layer TiO2 sheets. TiO2 nanotubes were formed by rolling up the single-layer TiO2 sheets with a rolling-up vector of [001] and attracting other sheets to surround the tubes.

Encapsulation of biomolecules and cells in hydrogel capsules via emulsion templating frequently induces an irreversible loss of bioactivity, because of the use of nonaqueous solvents. Here, we introduce an all-aqueous electrospray (AAE) approach to generate aqueous two-phase emulsion droplets, and we use them as templates to fabricate microcapsules with preserved cell viability. The approach allows formation of monodisperse microparticles with tunable sizes, variable compositions, and interior architectures in a mild gelation process. This technique potentially benefits a variety of new biomedical applications, such as delivery of bioactive proteins, transplantation of living cells, and assembly of cell-mimicking structures.