Early-Stage Detection of Copper Ion Release from Bronze Corrosion Using UV/Vis Spectroscopy and Hydrogel Sensing

Detecting copper(I) (Cu⁺) release at early corrosion stages is important for preserving bronze heritage materials. This study investigated the use of neocuproine (NC), a Cu⁺-specific ligand, for simple and selective colorimetric detection of Cu⁺ in solution. NC reacts with Cu⁺ to form a Cu(NC)₂ complex, which produces a distinct orange-red color with peak absorbance at 455 nm. Solutions were prepared with varying concentrations of Cu⁺ generated by reducing Cu²⁺ with excess ascorbic acid. Ultraviolet/Visible (UV/Vis) spectroscopy was used to quantify absorbance changes. The absorbance at 455 nm increased linearly across the tested Cu⁺ concentration range (6.25–200 µM) with an R² value above 0.98. Neocuproine enabled reliable, sensitive detection of Cu⁺ in solution via a visible color change and quantifiable spectrophotometric response. This method offers a simple, selective approach for monitoring early Cu⁺ release from corroding bronze materials, with potential applications in conservation diagnostics.