A combined electrochemical route to fabricate large-area and free-standing inverse opaline film

Abstract

A combined electrochemical route involving electrophoresis and electrodeposition is developed to fabricate a large-area unsupported nickel inverse opaline film with thickness less than 10 pm. A vertical electrophoresis allows for the packing of 495 nm polystyrene microspheres on an ITO-coated glass to form a colloidal crystal with significantly reduced defects. Subsequently, a nickel electrodeposition is employed to fill the interstitial voids among the close-packed polystyrene microspheres, followed by the removal of the colloidal template in a two-stage process, leaving a robust nickel skeleton with hexagonally arranged pores and interconnected pore channels. This nickel skeleton is then detached from the ITO-coated glass via a liquid nitrogen treatment, rendering a free-standing nickel inverse opaline film in 2 x 2 cm(2). Porometer measurements indicate a narrow pore size distribution consistent with images from scanning electron microscope. We determine that the intensity ratio of (111)/(100) diffraction peak is an indicator for the strength of the Ni inverse opals, and thus affects its structural integrity upon detachment from the ITO-coated glass. (C) 2016 Elsevier B.V. All rights reserved.