Size‐Dependent Phase Transformation of Noble Metal Nanomaterials

Abstract

As an important aspect of crystal phase engineering, controlled crystal phase transformation of noble metal nanomaterials has emerged as an effective strategy to explore novel crystal phases of nanomaterials. In particular, it is of significant importance to observe the transformation pathway and reveal the transformation mechanism in situ. Here, the phase transformation behavior of face‐centered cubic (fcc) Au nanoparticles (fcc‐AuNPs), adhering to the surface of 4H nanodomains in 4H/fcc Au nanorods, referred to as 4H‐AuNDs, during in situ transmission electron microscopy imaging is systematically studied. It is found that the phase transformation is dependent on the ratio of the size of the monocrystalline nanoparticle (NP) to the diameter of 4H‐AuND. Furthermore, molecular dynamics simulation and theoretical modeling are used to explain the experimental results, giving a size‐dependent phase transformation diagram which provides a general guidance to predict the phase transformation pathway between fcc and 4H Au nanomaterials. Impressively, this method is general, which is used to study the phase transformation of other metal NPs, such as Pd, Ag, and PtPdAg, adhering to 4H‐AuNDs. The work opens an avenue for selective phase engineering of nanomaterials which may possess unique physicochemical properties and promising applications.

Phase engineering of nanomaterials

“…However, such kind of phase transformation cannot be realized when the size of fcc-Au nanoparticle increases to 12 nm 70 . Besides the crystal phase transformation, electron beam irradiation can also initiate the crystallization of metal nanomaterials from their amorphous phase (for example, in the case of Bi nanoparticles 71 ), providing another efficient way to uncover the nucleation and growth mechanism of nanomaterials.…”

“…Panel e is adapted from REF. 70 , Wiley-VCH. phosphosulfide nanodots from layered bulk Pd3P2S8 crystals using the electrochemical lithiation method (left panel) and the high resolution TEM image of the as-obtained amorphous nanodots (right panel).…”

Unconventional-Phase Crystalline Materials Constructed from Multiscale Building Blocks

“…118 Furthermore, when monocrystalline fcc Au nanoparticles, which adhered to the surface of the 4H phase nanodomains in 4H/fcc Au nanorods, were irradiated with electron beam under in situ transmission electron microscopy (TEM), size-dependent phase transformation behaviors have been observed. 119 Specifically, when the size of the fcc Au nanoparticles (6.8 nm) is significantly smaller than the diameter of the 4H phase nanodomains (15.0 nm), the fcc Au nanoparticles would be transformed into 4H phase (Figure 4c,d). When their sizes are comparable, e.g., fcc Au nanoparticles with size of 12.0 nm and 4H phase nanodomains with diameter of 15.0 nm, the 4H phase nanodomains in 4H/fcc Au nanorods would be partially converted into fcc phase (Figure 4e,f).…”

Heterostructures Built through Site‐Selective Deposition on Anisotropic Plasmonic Metal Nanocrystals and Their Applications

“…nanoparticle dimers, have been successfully synthesized. [63][64][65][66][67] These heterostructures exhibit improved properties due to the coupling effects. For instance, Ag-Cu nanodimers exhibit a 3.4 times enhancement in the Faradaic efficiency for C 2 H 4 and a twofold enhancement in the partial current density for the CO 2 reduction reaction, compared with the pure Cu nanoparticle counterpart.…”