Gold Nanoparticles as Monoanion Sensors through Modified Electrophilicity

Derived from malachite green, new triaryl-carbonium-ion-functionalized gold nanoparticles have been synthesized for detecting anions. The detection process, and concomitant colour change, is based on charge compensation on the surface of nanoparticles, which triggers their aggregation, resulting in a bathochromic shift of the plasmon resonance band. The difference in electrophilicity of the malachite green triaryl ions in solution or on gold nanoparticles makes it possible to distinguish different anions related to their nucleophilic character.