Heating-induced evolution of thiolate-encapsulated gold nanoparticles: A strategy for size and shape manipulations

A heating treatment strategy for inducing size and shape change of composit e nanoparticles in solutions is described. The composite nanoparticles are similar to 2 nn gold cores encapsulated with alkanethiolate monolayers. The development of abilities in size and shape controls constitutes the motiva tion of this work. We demonstrated a remarkable evolution of the preformed particles in solutions toward monodispersed larger core sizes with well-def ined and highly faceted morphologies. The particles thus evolved were encap sulated with the thiolate shells, and exhibited striking propensities of fo rming long-range ordered arrays. The morphological and structural evolution s were characterized using transmission electron microscopy, X-ray diffract ion, UV-vis and infrared spectroscopies. Although temperature-driven crysta l growth is known for nonencapsulated particles, the evolution of the thiol ate-encapsulated nanoparticles in solutions into well-defined morphologies represents an intriguing example of temperature manipulations in size monod ispersity and shape control.