Polyvinylpyrrolidone-directed crystallization of ZnO with tunable morphology and bandgap

A novel polyvinylpyrrolidone (PVP)-directed crystallization route is successfully developed for the shape-selective synthesis of ZnO particles with distinctive shapes, including monolayer, bilayer, and multilayer structures, gears, capped pots, hemispheres, and bowls, at temperatures as low as 32 degrees C. This route is based on exploiting a new water/PVP/n-pentanol system. In the system, PVP can greatly promote ZnO nucleation by binding water and direct ZnO growth by selectively capping the specific ZnO facets, which is confirmed by IR absorption spectra. The bandgap of the ZnO particles is readily tuned by modifying the product morphology by adjusting the PVP chain length, PVP amount, water volume, and reaction temperature. The remarkable ZnO structures and the biomimetic method demonstrated here not only expand the structures and applications of ZnO but also provide a new approach to explore the unusual structures for novel physicochemical properties and technological applications. Furthermore, the novel ZnO/Au/ZnO sandwich structure is successfully fabricated by inserting a Au plate into the bilayer ZnO structure.