Electro-assisted deposition of silica nanotubes and nanopillars arrays using track-etch membranes and plasma etching

Abstract Arrays of supported silica nanotubes and nanopillars are formed by coupling gold-coated polycarbonate track-etch membranes with a pore diameter of 200 nm with electro-assisted silica deposition followed by oxygen plasma etching. The electro-assisted deposition provides control over the generation of the condensation catalyst and subsequent deposition of colloidal silica nanoparticles in the channels of the track etch membranes. Both silica nanotubes and nanopillars can be formed. Using an oxygen plasma to selectively remove the polycarbonate membrane, the vertical length of the supported silica nanostructure arrays can be tailored and the mechanism for deposition more clearly understood. The two most important variables are the speed at which the sol is stirred during electrodeposition and the electrodeposition time. By dispersing the electrogenerated hydroxide ion into the bulk of the deposition solution through stirring at a sufficient speed, the electrodeposited silica does not overcoat the surface of the membrane, thus allowing the nanotubes/pillars to be exposed. Adjusting the deposition time allows for either tubes or pillar-like nanostructures to be formed. Scanning electron microscopy (SEM) images acquired on the top surface of the membrane exposed to the deposition solution and the bottom electrode surface allowed for the mechanism for electrodeposition to be formulated. The materials thus produced can be tailored accordingly and have promising applications in chemical sensing. Graphical Abstract