Rayleigh-instability-induced metal nanoparticle chains encapsulated in nanotubes produced by atomic layer deposition

Cu nanoparticle chains encapsulated in Al₂O₃ nanotubes were successfully generated in a controlled manner by reduction of CuO nanowires embedded in Al₂O₃ at a sufficiently high temperature. The Al₂O₃ coating was deposited by atomic layer deposition (ALD). The particles mainly show a rodlike shape and are regularly distributed. The particle diameters and chain lengths corresponding to the inner diameters and lengths of the tubes, respectively, are controlled by the size of the CuO nanowire templates. Rayleigh instability, assisted by the uniform volume shrinkage created by the reduction of oxide to metal, is proposed to induce the formation of the nanochains. This method may potentially be extended to the synthesis of nanochains of other metals by reducing corresponding oxide nanowires embedded in ALD shells.