Shape-directional growth of Pt and Pd nanoparticles

Abstract

The design and synthesis of shape-directed nanoscale noble metal particles have attracted much attention due to their enhanced catalytic properties and the opportunities to study fundamental aspects of nanoscale systems. As such, numerous methods have been developed to synthesize crystals with tunable shapes, sizes, and facets by adding foreign species that promote or restrict growth on specific sites. Many hypotheses regarding how and why certain species direct growth have been put forward, however there has been no consensus on a unifying mechanism of nanocrystal growth. Herein, we develop and demonstrate the capabilities of a mathematical growth model for predicting metal nanoparticle shapes by studying a well known procedure that employs AgNO3 to produce {111} faceted Pt nanocrystals. The insight gained about the role of auxiliary species is then utilized to predict the shape of Pd nanocrystals and to corroborate other shape-directing syntheses reported in literature. The fundamental understanding obtained herein by combining modeling with experimentation is a step toward computationally guided syntheses and, in principle, applicable to predictive design of the growth of crystalline solids at all length scales (nano to bulk).

Metallic nanocrystals synthesized in solution: a brief review of crystal shape theory and crystallographic characterization

“…The models would have to capture the physics of growth, and in particular the behaviour of the different facets during growth. Recently, we have put forth such a model for Pt and Pd nanoparticles , which we review briefly here.…”

“…The interplay between different factors is intrinsically difficult to study, and the experimental information should ideally be cast into robust models, at least for cases where only one or several factors are involved. There are only a few reports of such kinetic models, recently put forth by some of us , as well as by other groups .…”

Advanced Large-Scale Nanofabrication Route for Ultrasensitive SERS Platforms Based on Precisely Shaped Gold Nanostructures

“…Nevertheless, the number and type of additives identified until now for shape control remain very limited, which suggests that chemical interactions are important. For MNPs, the interplay of halide ions (Br − , Cl − , and I − ) is critical and a general mechanism based on simple facet blocking does not explain many features of anisotropic particle growth [ 39 ]. On this basis, the formation of gold nanoprisms and nanohexagons that have octahedral morphologies can be attributed to the preferential adsorption of K + or H + on the {111} planes of Au nuclei that inhibit the growth rate along the {111} direction suitable to produce triangular and octahedral geometries.…”

“…H + may move faster with respect to the corresponding selective planes because it is smaller than K + , resulting in the rapid growth rate on {111}, which favors the formation of hexagons rather than triangles or prisms. It is well established that the surface energy of {100} plane is higher than that of {111} plane, in relation to the higher chemical reactivity [ 31 , 39 ]. Generally, chemisorption is favored for smaller atoms or molecules.…”

Silver Nanoparticles Loaded Thermoresponsive Hybrid Nanofibrous Hydrogel as a Recyclable Dip‐Catalyst with Temperature‐Tunable Catalytic Activity

“…As we know, silver nanoparticles (AgNPs) of less than 10 nm particle diameter have catalytic activity for many organic reactions, such as the reduction reactions of nitro compounds and organic dyes, ethylene epoxidation, and dehydrogenation reaction . In comparison with other metal nanoparticles with catalytic activity, such as Pt and Pd nanoparticles, AgNPs can be prepared more readily and inexpensively, so they have attractive application prospect in catalysis . However, like other colloidal metal nanoparticles, colloidal AgNPs dispersed in aqueous medium are prone to self‐aggregation and settling down owing to their high surface energy and great density, maybe concomitant with loss of their catalytic activity.…”