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Ordered submicron ferromagnetic Co–B arrays were obtained through a biomimetic process at ambient temperature. When Co2+ ions complexed to soluble starch were reduced by potassium borohydride in a magnetic field, the magnetic force allowed the nanoparticles of Co–B alloys to array along the field lines and deposit on a solid support. This process is inspired by the migration mechanism of magnetotactic bacteria in a geomagnetic field and this convenient strategy should be helpful for the production of ordered arrays of other magnetic materials. After Co–B alloys are assembled into ordered chains, they exhibit strong ferromagnetic signals in the variable temperature ferromagnetic resonance spectra in the temperature range of 100–420 K.

Growth and alignment of nanofibers via single-step strategies are appealing goals in nanoscience studies and nanofiber-based device integration. We are inspired by the proficiency of the silkworm in manipulating one continuous thread in the space confined by the cocoon frame, and thus propose the guided growth and alignment of millimetre-long titanate nanofibers to macroscopic networks in solution by taking advantage of the unique surface properties of the periodical grooves patterned on the inner wall of a Teflon-lined autoclave. The textures of the networks can be controlled to be concentric rings or grids by tuning the geometry of the grooves. The growth mechanism of the networks is discussed on the basis of interfacial interactions. Furthermore, well-ordered networks consisting of millimetre-long heterostructured TiO2 nanofibers with an anatase backbone and monoclinic sheaths can be readily derived via the protonation and thermal annealing treatment of the titanate networks. Electrical measurements demonstrate that the heterostructured TiO2 nanofibers exhibit unique rectifying behaviours and long-range transport properties. The present bio-inspired methodology that solves the problem of growing and aligning nanofibers in solution should be applicable to other material systems. Moreover, the as-prepared titanate and TiO2 nanofiber networks may have potential applications in host–guest chemistry, thin-film based electronic and optoelectronic devices, and highly efficient photocatalysts.

Herein, we report the direct production of free-standing titanate and TiO2 nanofiber membranes with selective permeability and cleaning performance. The membrane was prepared through the hydrothermal reactions among tetra-n-butyl titanate, graphene oxide and NaOH. Tetra-n-butyl titanate reacted with NaOH to form high-quality nanofibers with lateral dimensions below 100 nm and longitudinal dimensions of several tens of micrometres. Graphene oxide was condensed with the nanofibers and enabled the nanofibers to organize into a free-standing membrane with a diameter of 1 cm. Interestingly, the interlayer of the as-prepared membrane stood parallel and as closely packed nanofibers, totally different from the disorders of those prepared by the filtration method. Benefiting from the distinctive structure, the nanofiber membrane showed a selective permeability: water could cross it easily while organic dyes and bacteria were trapped for a long time (120 h for methylene blue and methyl orange and 24 h for rhodamine B and Bacillus coli). Furthermore, the membrane showed a high efficiency in the photodecomposition of the trapped dyes because it combined the photocatalytic activity, the porosity, and the capability of separating photogenerated electrons and holes. Consequently, the membrane possesses both the separation function and cleaning function and should find potential applications in membrane-based water purification.

A strategy of co-reaction of Fe and TiO2 with concentrated NaOH was designed to prepare Na2Ti3O7 nanosheets grown epitaxially by Fe3O4 crystallites, for the purpose of modifying interlayer structures and ion exchange properties of the layered compound Na2Ti3O7. TiO2 could react with NaOH to form lamellar intermediates while Fe could be converted into Fe3O4 to deposit on the surface of the intermediates. Eventually, free-standing Fe3O4@Na2Ti3O7 nanosheets were successfully synthesized in an extremely high yield (∼95% efficiency). Fluorescein and its derivatives utilized as probes to study the ion exchange property of Fe3O4@Na2Ti3O7 nanosheets, which could provide visual observations of the degree of ion exchange. The results indicate that the as-prepared Fe3O4@Na2Ti3O7 nanosheets possess much more sensitive Na+ exchange performance than isolated Na2Ti3O7 nanostructures, and hence they should have potential application in the extraction of trace active components, such as cationic amino acid and peptides in biology. Furthermore, the present strategy is also helpful in the design synthesis of other layered compounds grown epitaxially by magnetic clusters to achieve enhanced physicochemical properties.