Preparation of a Nickel Ion Containing Langmuir–Blodgett Multilayer and an Ultra-Thin Nickel Film Deposited on an Interpenetrating Polymer Network Substrate

Abstract

The nickel ion containing Langmuir-Blodgett (LB) multilayer was prepared by transferring nickel acetate, spread on the surface of a sub-phase of ultra-pure water and stearic acid-chloroform mixture, onto an interpenetrating polymer network (IPN) substrate. The substrate was prepared by dip-pulling a hydrophilic silicon wafer or a glass plate into precursors, followed by solidification at room temperature, in order to create an ultra-thin and uniform surface for metal deposition. The multilayer was then converted into an ultra-thin nickel film after chemical reduction by 0.01 mol/l sodium borohydride. The surface pressure of the monolayer and dipping speed of substrate were determined by measuring the transfer coefficient. Fourier transform infrared spectroscopy (FT-IR) was used to investigate the interactions of the nickel ions with the IPN during the multilayer deposition on substrate, and the metal transformations of nickel ion in the ultrathin film. The shifted peak location for -C=O verified the interactions between the IPN and the nickel ion and the transformation of the nickel ion by reduction. Further reduction caused the organic phase to dissolve, resulting in most of it being removed from the multilayer. The surface morphologies of the LB multilayer were detected by atomic force microscopy (AFM). Compared with the IPN, which formed a uniform and flat film, within a range of nanometers, the Ni/IPN multilayer and Ni ultra-thin film both showed some surface fluctuations, although these were still within nanometer range. The roughness of the nickel ion containing multilayer and the ultra-thin nickel film was 1.123 nm and 0.773 nm with a maximum height of 12.451 nm and 14.933 nm, respectively, which were larger than that of pure IPN substrate of 0.593 nm with the max height of 6.795 nm.