Visual Detection of Copper(II) by Azide‐ and Alkyne‐Functionalized Gold Nanoparticles Using Click Chemistry

Just one click, and the color's gone: In the presence of Cu2+ with sodium ascorbate as a reductant, gold nanoparticles that have azide- and alkyne-terminated groups undergo aggregation as the result of CuI-catalyzed click chemistry. This process can be monitored by eye without the aid of instruments (NPs=nanoparticles).