Selective formation of Ag domains on MnO nanooctapods for potential dual imaging probes

Abstract

In the present study, the growth of Ag domains on the surface of MnO octapods yielded a uniform MnO octapod–Ag heterodimer structure by a phase-transfer protocol in toluene. The Ag domains were selectively formed on one of the high index surfaces of the MnO octapods. The resulting MnO–Ag heterodimers have basically two independent domains. On this basis, multiple functions are expected, including plasmon light scattering from the Ag domains and magnetic resonance from the MnO domains. Notably, the heterodimers strongly scattered visible light at 420 nm, and even a single particle signal could be detected in a dark-field spectroscopy image. The scattering peak was extended to the near-IR range by the formation of MnO octapod–AgAu hollow heterodimers via a galvanic replacement reaction. The heterodimers also showed weak ferromagnetism at low temperature, and exhibited a positive T1 signal in magnetic resonance imaging. These properties demonstrate that the MnO–Ag heterodimers can potentially serve as dual imaging probes for biological systems.