Abstract
The growth of nanoparticles along one or two directions leads to anisotropic nanoparticles, but the nucleation (i.e., the formation of small seeds of specific shape) has long been elusive. Here, we show the total structure of a seed-sized Au56 nanoprism, in which the side Au{100} facets are surrounded by bridging thiolates, whereas the top/bottom {111} facets are capped by phosphine ligands at the corners and Br− at the center. The bromide has been proved to be the key to effectively stabilize the Au{111} to fulfill a complete face-centered-cubic core. In femtosecond electron dynamics analysis, the non-evolution of transient absorption spectra of Au56 is similar to that of larger-sized gold nanoclusters (n > 100), which is ascribed to the completeness of the prismatic Au56 core and an effective electron relaxation pathway created by the stronger Au-Au bonds inside. This work provides some insights for the understanding of plasmonic nanoprism formation.
Highlights
IntroductionThe growth of nanoparticles along one or two directions leads to anisotropic nanoparticles, but the nucleation (i.e., the formation of small seeds of specific shape) has long been elusive
The growth of nanoparticles along one or two directions leads to anisotropic nanoparticles, but the nucleation has long been elusive
In a typical synthesis of Au56, 0.2 mmol HAuCl4·3H2O, 0.28 mmol tetraoctylammonium bromide (TOAB), 0.20 mmol phosphine ligand (any of P(Ph-4CF3)[3], P(Ph-4-Cl)[3], P(Ph-4-F)[3], or PPh3), and 200 μL tert-butylbenzenethiol were mixed in solvents of CH3CH2OH and CH2Cl2 (v:v = 1:9)
Summary
The growth of nanoparticles along one or two directions leads to anisotropic nanoparticles, but the nucleation (i.e., the formation of small seeds of specific shape) has long been elusive. Atomically precise metal nanoclusters (NCs) of 1–3 nm in diameter (e.g., stabilized by thiolates (SR) or other ligands) have emerged as a new class of nanomaterials, which can serve as models to relate the detailed structures to the assembly and various properties[21–28], but no relationship between the anisotropic NPs and NCs has been discussed in the literature. The advantage of pursuing anisotropic NCs with atomic precision lies in the possible determination of total structures (i.e., the metal core, and the surface bonding and arrangement of ligands)[29], providing atomic-level insights into the “seeds”. Au(111) facets of nanoprisms is critically needed but still unknown This motivated us to obtain atomically precise NCs of prismatic shape in hope of solving their atomic structure, as such information will offer a glimpse of the long sought-after seeds of nanoprisms and hopefully bridge up the two research domains[1–7,25,40,41]
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