Alumina-membrane-based growth of functional PbO₂ and Pb(Zr,Ti)O₃ metal-oxide nanowires by spin coating

We report alumina-membrane-based growth of functional PbO₂ and Pb(Zr,Ti)O₃ metal-oxide nanowires by combination of sol-gel processing and spin coating. Nanowires with a uniform diameter throughout the entire length and a relatively smooth surface are synthesized by the method. Fabricated PbO₂ nanowires show a single crystalline structure with diameter of about 40 nm and length of tens of micrometers. PZT nanowires exhibit a high aspectratio (up to 400) with diameter of about 50 nm and length of about 20 μm. Our experimental results and calculations show that a vortex motion by spin coating plays an important role for the sols to enter the pores of the membrane in order to achieve nanowires. One main driving force for the drawing of sol nanoparticles into the membrane pores is a vortical force along the direction of the swirl, which is, roughly speaking, vertical to the membrane.