Graphene Oxide‐Hyperbranched Polyethyleneimine Fabricated and Stabilized AuNPs Nanocomposites for Colorimetric Detection of Silver Ions Based on a Non‐Aggregation Mechanism

Abstract Highly water‐soluble GO‐HPEI was prepared by modifying graphene oxide (GO) with hyperbranched polyethylenimine (HPEI) containing a large number of amines to solve the problem of poor water‐solubility of GO. Using GO‐HPEI as reducing agent and stabilizer, Au nanoparticles (AuNPs) based colorimetric probe (GO‐HPEI/AuNPs) with thermal stability up to 130 °C and high salt resistance was prepared in situ. The morphology and structure of GO‐HPEI/AuNPs were characterized by XPS, FTIR, TEM, DLS and Zeta potential. The GO‐HPEI/AuNPs can detect silver ions (Ag⁺) through the formation of non‐aggregated and stabilized Au−Ag core‐shell nanoparticles. The unusual sensing mechanism endowed this sensor with unique color variation and high selectivity. The GO‐HPEI/AuNPs sensor exhibited an obvious color change from red to ochre yellow and high sensitivity (LOD=54.9 nM) with a good linear relationship in the range of 0–65.7 μM (R²=0.9903). Furthermore, this colorimetric sensor was successfully applied to detect Ag⁺ in real water samples. Therefore, the GO‐HPEI/AuNPs sensor based on the formation of new nanomaterials has great potential for detecting Ag⁺ and analytical applications.