Flow-directed synthesis of spatially variant arrays of branched zinc oxide mesostructures.

The use of fluid flow to control crystal morphology during the liquid-phase synthesis of inorganic nanomaterials is a relatively under explored approach. Synthetic strategies that take advantage of flow effects present the opportunity to tune several parameters (e.g., flow velocity and direction) in addition to conventional growth parameters (e.g., time, temperature, chemistry, and concentration), and thus enable additional levels of control in the bottom-up synthesis of nanomaterials. The current work reports the application of microfluidics to the rational synthesis of spatially variant arrays of branched zinc oxide (ZnO) nanorods with predictable morphological and compositional characteristics. Specifically, the dislocation driven growth rates of branches within ZnO nanorod arrays was rationally controlled using dynamic, high-velocity precursor flow, yielding ZnO mesostructures with morphology that depended on the location within the arrays. This approach compliments current synthetic strategies and is generally applicable to a range of materials with a diverse set of functional properties (e.g., optical, magnetic, electronic) and applications.