Sharp Transition from Nonmetallic Au₂₄₆ to Metallic Au₂₇₉ with Nascent Surface Plasmon Resonance

Abstract

The optical properties of metal nanoparticles have attracted wide interest. Recent progress in controlling nanoparticles with atomic precision (often called nanoclusters) provide new opportunities for investigating many fundamental questions, such as the transition from excitonic to plasmonic state, which is a central question in metal nanoparticle research because it provides insights into the origin of surface plasmon resonance (SPR) as well as the formation of metallic bond. However, this question still remains elusive because of the extreme difficulty in preparing atomically precise nanoparticles larger than 2 nm. Here we report the synthesis and optical properties of an atomically precise Au(SR) nanocluster. Femtosecond transient absorption spectroscopic analysis reveals that the Au nanocluster shows a laser power dependence in its excited state lifetime, indicating metallic state of the particle, in contrast with the nonmetallic electronic structure of the Au(SR) nanocluster. Steady-state absorption spectra reveal that the nascent plasmon band of Au at 506 nm shows no peak shift even down to 60 K, consistent with plasmon behavior. The sharp transition from nonmetallic Au to metallic Au is surprising and will stimulate future theoretical work on the transition and many other relevant issues.

Electrospray Ionization Mass Spectrometry: A Powerful Platform for Noble‐Metal Nanocluster Analysis

“…[13] It will result in multiple sets of peaks in the mass spectra of noble-metal NCs, forming as eries of peaks with similar patterns but different charges (different spacing between two consecutive isotope peaks). At the same time,m ultiple-charged ions extend the molecular-weight range of analytes that can be analyzed by ESI-MS,making the analysis of large NCs and even small NPs with surface-plasmon-resonance properties possible (for example,A g 146 Br 2 (TIBT) 80 [14] and Au 279 (TBBT) 84 , [15] where TIBT and TBBT denote 4-isopropylbenzenethiolate and 4tert-butylbenzenethiol, respectively). Furthermore,E SI may also produce quasimolecular ions (ions formed from protonation/deprotonation or ion addition of molecular ions) which are not exactly the same as the analyte molecule.…”

Systematically Tuning the Electronic Structure of Gold Nanoclusters through Ligand Derivatization

“…Atomically-precise gold nanoparticles are valued for their potential as photocatalysts,p hotovoltaics,c hemical sensors, non-linear optical media, etc.,a nd our fundamental understanding of the chemical/physical properties relevant to such applications has undergone ar enaissance over the past decade due to advances in synthetic protocols selective for their isolation and crystallization. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] Crystallographic characterization of ligand-protected gold nanoparticles has revealed high-symmetry core structures protected by the socalled "staple motif" for thiols or, in the case of phosphines, halides,orh ydrocarbons,direct metal core-ligand binding. [14] Such detailed geometric characterization has been pursued due to its potential to establish structure/function relationships in the synthesis of "designer" nanomaterials.…”

Systematically Tuning the Electronic Structure of Gold Nanoclusters through Ligand Derivatization

“…Atomically‐precise gold nanoparticles are valued for their potential as photocatalysts, photovoltaics, chemical sensors, non‐linear optical media, etc., and our fundamental understanding of the chemical/physical properties relevant to such applications has undergone a renaissance over the past decade due to advances in synthetic protocols selective for their isolation and crystallization . Crystallographic characterization of ligand‐protected gold nanoparticles has revealed high‐symmetry core structures protected by the so‐called “staple motif” for thiols or, in the case of phosphines, halides, or hydrocarbons, direct metal core‐ligand binding .…”