Solution-Controlled Self-Assembly of ZnO Nanorods into Hollow Microspheres

Abstract

A novel solution-controlled self-assembly process has been developed to fabricate nanorod assembled ZnO hollow spheres without adding any structure-directing agents and templates, and as-prepared hollow samples with size about 5 μm are constructed by the radially oriented single-crystalline nanorods with length and diameter of about 1.5 μm and 80 nm, respectively. The investigation on the evolution formation reveals that water was critical to control the assembly of the fresh formed nanocrystallites, and hollowing formation was proved to be the Ostwald ripening process by tracking the structures of the products at different reaction stages. Scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and high-resolution transmission electron microscopy were used to characterize the structure of synthesized products, and gas-sensing properties investigation shows that the nanorod-assembled hollow spheres exhibit high gas response to formaldehyde at the optimum working temperature of 400 °C.