Noble metals with strong plasmons have been widely used as enhancement substrates for molecule identification. However, cyanide, a toxic and important signaling molecule with a corrosive nature to noble metals, makes direct recognition challenging. Herein a novel superstable magnetic graphene-isolated AuCo nanocrystal (MACG) has been designed. Such graphene isolation enables superior stability without corrosion. Moreover, unexpectedly, although graphene isolated direct contact between Au and cyanide, their interaction was transferable and remained, which gifted MACGs direct cyanide capture capability with no specific ligands needed. Density functional theory calculations and natural bond orbital analysis indicated that the graphene isolation only slightly affected the charge transfer and that a relatively strong interaction was maintained between Au and cyanide. MACGs were utilized for efficient cyanide capture and clearance in various hydrologic environments and sensitive in vivo cyanide capture in C. elegans infected with P. aeruginosa, a pathogen with cyanide as the biomarker, indicating promise for various applications.