Synthesis of rattle-type Ag@Al2O3 nanostructure by laser-induced heating of Ag and Al nanoparticles

A simple and flexible method has been presented for the fabrication of rattle-type Ag@Al2O3 nanostructures in water and polyvinyl pyrrolidone polymer solution based on laser-induced heating of mixture of silver (Ag) and aluminium (Al) nanoparticles by 532-nm laser. Silver and aluminium nanoparticles were prepared by pulsed laser ablation in liquid using same laser wavelength. The transmission electron micrographs revealed morphological changes from sintered-/intermediate-type structure in water medium and jointed structure (heterostructures) in polymer solution to rattle-type structure with changing irradiation time. At longer irradiation time, the Kirkendall effect becomes dominant due to diffusion rate mismatch between the two metals at the interface and facilitates the formation of porous alumina shell over silver core. The morphology and chemical composition of the nanostructures were characterized by transmission electron micrograph, high-resolution transmission electron micrograph and energy-dispersive X-ray analysis. The melting response of alumina (Al2O3), aluminium and silver nanoparticles with 532-nm laser wavelength provides novel pathway for rattle-type formation.