Petal-like Structured Cu²⁺-Doped MnO₂ Nanoflowers as Nanozymes for Colorimetric Detection of Ag⁺

This study addresses the pressing need for sensitive and selective detection of silver ions (Ag+) due to their harmful environmental and health impacts. Traditional detection methods, such as inductively coupled plasma mass spectrometry (ICP-MS), are often expensive and complex, limiting their practical applicability. In this research, we developed a novel colorimetric sensing method utilizing Cu-doped manganese dioxide nanoflowers (Cu-MnO2 NFs) synthesized via a hydrothermal process. The catalytic performance of these nanoflowers was optimized for the oxidation of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to its blue oxidized form (oxTMB). The introduction of glutathione (GSH) allowed for a competitive reduction process, where Ag+ ions formed complexes with GSH, leading to a measurable color change that correlates with Ag+ concentration. Our method demonstrated a linear detection range of 2–26 μM and a minimum detection limit of 700 nM for Ag+. Through a thorough examination of selectivity against other metal ions, this colorimetric approach proves to be effective in pollutant detection within aquatic ecosystems, contributing valuable insights into environmental monitoring.