Tailoring Amino‐Functionalized Graphitic Carbon‐Encapsulated Gold Core/Shell Nanostructures for the Sensitive and Selective Detection of Copper Ions

The effective transfer of strong electromagnetic field from the gold core through the coating shell represents the most significant challenge for the applications of plasmonic nanoparticles. This study applies a one‐step arc discharge method to synthesize graphitic carbon‐encapsulated gold nanoparticles (Au@G NPs) functionalized with amino groups uniformly via adding NH 3 into He background gas. By tailoring the coating shell into few‐layered graphene, a strong localized surface plasmon resonance (LSPR) absorption band is achieved. The NH 3 introduces H radicals to strengthen the LSPR characteristic by etching the coating graphitic shell, as well as provides dissociated NH or NH 2 species to functionalize the surfaces with amino groups. With an LSPR‐based colorimetric method, it is demonstrated that trace Cu 2+ ions can be detected rapidly with excellent sensitivity (as low as 10 × 10 ‐9 m linearly) and selectivity against other metal ions (Na + , K + , Mg 2+ , Ca 2+ , Co 2+ , Fe 2+ , Cd 2+ , Pb 2+ , and Hg 2+ ions) by amino‐functionalized Au@G NPs in water samples.