Electroless Deposition on Three Substrates: Brass Washers, Cicada Exoskeletons, and Beetles

Abstract

This laboratory experiment showcases electroless deposition, an autocatalytic reduction process performed in aqueous solution containing a metal ion in the presence of a reducing agent yielding a coherent metal film. One set of experiments has been performed by second-semester general chemistry students in a 3 h lab session. After preparing an electroless nickel plating bath, they first plate a brass washer with nickel for 10 min at 85 °C. Using weight gain data for their brass washer along with its surface area, the thickness of the nickel coating is determined. The same electroless nickel plating bath is then used to plate a pretreated cicada exoskeleton with nickel. The three-step pretreatment procedure deposits Pd(s) nanoparticles on a nonconducting exoskeleton made of chitin, transforming it into a conducting substrate. A second set of experiments has been performed by upper-class chemistry majors. They (1) explore the reproducibility in weight gain when plating brass washers with nickel for 10, 20, 30, and 40 min time intervals, (2) plate beetles with nickel, and (3) plate cicada exoskeletons with copper using an electroless copper plating bath recipe they find in the literature. Weight gain data and photos of the plated cicada exoskeletons and beetles accompany this article. The nickel-plated brass washers and cicada exoskeletons were examined with XRF spectrometry. This analysis demonstrates that the nickel coating is not pure nickel but rather an alloy containing phosphorus.