Simple and rapid preparation of vertically aligned gold nanoparticle arrays and fused nanorods in pores of alumina membrane based on positive dielectrophoresis

Arrays of gold nanoparticles and gold nanorods have been fabricated in the spatially localized pores of a porous alumina membrane using positive dielectrophoresis (p-DEP). The porous alumina membrane with a pore size of 200 nm and a thickness of 60 μm was sandwiched between the lower microarray electrode and the upper bare ITO electrode. Then, a 100-nm-diameter gold nanoparticle suspension (0.6–1.0 × 1012 particles ml−1) in pure water was introduced in the space between the alumina membrane and the upper ITO substrate. The application of an AC voltage (typically 30 Vpp, 50–100 kHz) for p-DEP to the lower and upper electrodes forced the nanoparticle to move into the straight pores of the membrane above the ITO microarray electrode, forming arrays of nanoparticles inside the membrane. When the distances between the adjacent gold nanoparticles were close, the particles fused together to form rod-like structures with a well-defined diameter. The present procedure for fabrication of ordered nanocomposites in nanopores can be applied to electrical and optical devices and sensors.