Colloquium: Spontaneous ordering at nanoscale level : superlattice formation in transition metal nanocubes

Date: October 07, 2016
Time: 3:00 pm – 4:15 pm

Location: Exploratory Hall L111 (Google map)

Featured Speaker:
Alina Bruma
NIST

Abstract:
Controlling the morphology of bimetallic nanoscale systems at the atomic level is of utmost importance in fields such as nanocatalysis or optics. Recently, bimetallic Gold−Palladium (AuPd) nanocubes have been synthesized using a variety of chemical synthesis routes [1] for applications in nanocatalysis since coupling the two metals not only enhances selectivity toward a much broader range of nanocatalysis reactions, but it also increases the tolerance toward “poisoning” for which monometallic systems are highly susceptible. In recent years, a significant effort has been put in carefully controlling the synthesis of bimetallic nanocubes systems with sizes of the order of tens of nanometers, which sit at the threshold between nanoscale and bulk matter. In this study we emphasize the spontaneous superlattice formation in AuPd nanocubes of the order of 30 nm synthesized by a seed-mediated growth method. Although a significant effort has been currently put into the controlled synthesis of small seed-mediated AuPd nanocubes, where Au is used for the formation of cuboctahedral cores with high indexed facets onto which Pd is deposited, there still exists a significant effort in understanding morphological features of these nanocubes [2, 3] and what triggers their enhanced performance in catalysis. Here we employ the Aberration-corrected High Angle Annular Dark Field Scanning Transmission Electron Microscopy (Cs- corrected HAADF-STEM) for explaining a mechanism for spontaneous superlattice formation in these systems and emphasize important physical properties which can potentially enhance a wide range of catalysis reactions.

Refreshments will be served.