Solution preparation of alloy core–shell nanoparticles: The case of Ni–Cu@Au–Cu nanoparticles

• First synthesis of Ni–Cu@Au–Cu alloy core–shell nanoparticles via a solution method.
• Surface plasmon resonance absorption band at red light region was observed.
• Room-temperature ferromagnetic properties was identified.
• Alloy core–shell structure offers tunable optical and magnetic properties.

We report a solution method for the preparation of alloy core–shell nanoparticles which consist of Ni–Cu cores and Au–Cu shells. This method involves an injection-quenching step in which Au precursor is injected in and reduced to form alloy shells on pre-formed Ni–Cu cores. The as-prepared Ni–Cu@Au–Cu nanoparticles possess a spherical morphology, and have a typical size of ∼35 nm and shell thickness of 6–9 nm. The formed core–shell structure has been verified by high-resolution transmission electron microscopy and high-angle annular dark-field imaging along with the analyses of energy-dispersive X-ray spectroscopy. Broadened surface plasmon resonance (SPR) absorption band centering at red light region has been observed. Magnetic measurements reveal room-temperature ferromagnetic properties for the as-prepared Ni–Cu@Au–Cu nanoparticles. The formation of alloy core–shell structure offers tunable optical and magnetic properties for their multiple applications.

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