Ultrasensitive Na+ exchanging performance of free-standing Fe3O4@Na2Ti3O7 nanosheets indicated by fluorescein

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.