General synthesis of 2D ordered hollow sphere arrays based on nonshadow deposition dominated colloidal lithography

A general strategy, nonshadow deposition dominated colloidal lithography (NSCL), was proposed for the synthesis of two-dimensional (2D) ordered hollow sphere arrays of conductive materials. Gold, polypyrrole, CdS, and ZnO were taken as model materials to demonstrate the NSCL strategy, and built as 2D hollow sphere arrays successfully. In this strategy, a thin gold coating is first introduced on a polystyrene sphere (PS) colloidal monolayer via ion-sputtering deposition, and a hollow sphere array can thus be obtained by further electrochemical deposition on such a monolayer and by subsequent removal of PSs. The proposed strategy is flexible and facile to control the microstructure and size of the hollow sphere array, and the features are as follows: (i) controllable shell of the hollow sphere from single-layer to multilayer with single or multiple compositions, (ii) tunable morphology from simple structure to hierarchical micro/nanostructure, and (iii) changeable arrangement of hollow spheres from close-packing to non-close-packing. Besides these, the hollow sphere size and the shell thickness can also be controlled by changing the colloidal sphere and deposition time, respectively. Further investigation indicates that the success of NSCL should be owed to a key step, that is, an ion-sputtering induced nonshadow deposition surrounding the whole surfaces of colloidal spheres. This allows an equipotential face and thus homogeneous deposition surrounding the surfaces of PSs in an electrochemical deposition process, and final formation of hollow sphere structure. The 2D ordered hollow sphere arrays with controllable microstructure and size could exhibit importance both in fundamental research and in practical applications.