A General Approach to the Synthesis of M@Au/Ag (M = Au, Pd, and Pt) Nanorattles with Ultrathin Shells Less Than 2.5 nm Thick

Abstract

This article reports a general approach to the facile synthesis of M@Au/Ag (M = Au, Pd, and Pt) nanorattles. The synthesis involves three major steps: (i) formation of M@Ag nanocubes via seed-mediated growth, (ii) conformal deposition of ultrathin Au shells on the M@Ag nanocubes by reducing HAuCl4 with ascorbic acid under an alkaline condition, and (iii) formation of M@Au/Ag nanorattles through a galvanic replacement reaction between the Ag shells and aqueous HAuCl4. The deposition of an ultrathin Au shell prior to the galvanic replacement reaction is crucial to a successful synthesis as this shell can enhance the mechanical strength of the resultant nanorattles by preventing the Au/Ag alloy shell from fragmentation during the galvanic replacement process. The localized surface plasmon resonance peak of the nanorattles is determined by the thickness of the Au/Ag alloy shell. For Au@Au/Ag nanorattles with an edge length of 15 nm, they could be tuned to have near-infrared absorption and excellent photothermal conversion capability for their use as transducers in the effective destruction of cancer cells through laser irradiation.