A Highly Sensitive and Selective Colorimetric Hg²⁺ Ion Probe Using Gold Nanoparticles Functionalized with Polyethyleneimine

Scheme 1

Schematic illustration of the AuNPs capped with PEI, and the aggregation of PEI-AuNPs reacted with Hg²⁺ ion, accompanied by a color change, and the predicted coordination bond between Hg²⁺ ions and PEI-AuNPs.