Large-Scale Synthesis of Metal Nanocrystals in Aqueous Suspensions

Fundamental studies and practical use of metal nanoparticles (NPs) frequently depend on the ability to reproducibly synthesize large quantities of shape-specific NPs. For this reason, facile synthetic procedures are desired that will lead to large quantities of uniformly sized metal NPs exhibiting specific shapes. Here, we report a general approach to the large-scale synthesis of noble metal nanocrystals having well-defined shapes and a narrow size distribution. This method utilizes seed-mediated NP growth in aqueous suspensions of cationic surfactants and metal salts. It leads to a ∼60-fold increase in NP volumetric production capacity, compared to the most widely used solution-based synthetic methods. In addition, it uses up to 100 times less cationic surfactant than conventional solution-based methods. The applicability of the method is demonstrated in the synthesis of Pd nanocubes, rhombic dodecahedra, and polyhedrons with low index facets; branched Pd nanocrystals; alloy Pt/Pd nanocubes; Ag nanocubes. The advantages and limitations of the approach are discussed, including accessible shapes, growth kinetics, and the capability to scale up the synthetic procedure.