Abstract
Abstract Both the electronic and surface structures of metal nanomaterials play critical roles in determining their chemical properties. However, the non-molecular nature of conventional nanoparticles makes it extremely challenging to understand the molecular mechanism behind many of their unique electronic and surface properties. In this work, we report the synthesis, molecular and electronic structures of an atomically precise nanoparticle, [Ag206L72]q (L = thiolate, halide; q = charge). With a four-shell Ag7@Ag32@Ag77@Ag90 Ino-decahedral structure having a nearly perfect D5h symmetry, the metal core of the nanoparticle is co-stabilized by 68 thiolate and 4 halide ligands. Both electrochemistry and plasmonic absorption reveal the metallic nature of the nanoparticles, which is explained by density functional theory calculations. Electronically, the nanoparticle can be considered as a superatom, just short of a major electron shell closing of 138 electrons (q = –4). More importantly, many of ligands capping on the nanoparticle are labile due to their low-coordination modes, leading to high surface reactivity for catalysing the synthesis of indoles from 2-ethynylaniline derivatives. The results exemplify the power of the atomic-precision nanocluster approach to catalysis in probing reaction mechanisms and in revealing the interplay of heterogeneous reactivities, electronic and surface structural dynamics, thereby providing ways for optimization.
Highlights
Metal nanoparticles have emerged as an important topic in materials research in view of their intriguing properties and wide-range applications in areas such as catalysis [1], electronics [2], bio-sensing [3] and nanomedicine [4], etc
Great advances have been made in the syntheses of metal nanoparticles with monodispersity, in particular, atomically precise nanoparticles with well-defined surface structures that bestows on them the potential to shed light on important issues in surface sciences [16,17,18,19,20,21,22,23,24,25,26,27,28,29]
In an attempt to gain insights with regards to the above-mentioned issues, we report the synthesis of a novel metal nanoparticle, formulated as [Ag206(SR)68F2Cl2]q (1, q = +2, +3, +4 and +5) where SR=cyclohexanethiol based on structure determination by single-crystal X-ray crystallography
Summary
Metal nanoparticles have emerged as an important topic in materials research in view of their intriguing properties and wide-range applications in areas such as catalysis [1], electronics [2], bio-sensing [3] and nanomedicine [4], etc. Conventional nanoparticles are usually intrinsically heterogeneous and it is challenging to define their surface structures down to atomic precision, even with advanced transmission electron microscopy (TEM) and scanning-probe microscopies, precluding studies of the precise correlation of particle structure and property [13,14,15]. Great advances have been made in the syntheses of metal nanoparticles with monodispersity, in particular, atomically precise nanoparticles with well-defined surface structures that bestows on them the potential to shed light on important issues in surface sciences [16,17,18,19,20,21,22,23,24,25,26,27,28,29]. Few works have focused on the surface reactivity caused by the lability of capping agents on catalysis down to atomic precision
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