Atomically precise gold nanocrystal molecules with surface plasmon resonance

Abstract

Since Faraday's pioneering work on gold colloids, tremendous scientific research on plasmonic gold nanoparticles has been carried out, but no atomically precise Au nanocrystals have been achieved. This work reports the first example of gold nanocrystal molecules. Mass spectrometry analysis has determined its formula to be Au 333 ðSRÞ 79 (R ¼ CH 2 CH 2 Ph). This magic sized nanocrystal molecule exhibits fcc-crystallinity and surface plasmon resonance at approximately 520 nm, hence, a metallic nanomolecule. Simulations have revealed that atomic shell closing largely contributes to the particular robustness of Au 333 ðSRÞ 79 , albeit the number of free electrons (i.e., 333 − 79 ¼ 254) is also consistent with electron shell closing based on calculations using a confined free electron model. Guided by the atomic shell closing growth mode, we have also found the next larger size of extraordinarily stability to be Au ∼530 ðSRÞ ∼100 after a size-focusing selection-which selects the robust size available in the starting polydisperse nanoparticles. This work clearly demonstrates that atomically precise nanocrystal molecules are achievable and that the factor of atomic shell closing contributes to their extraordinary stability compared to other sizes. Overall, this work opens up new opportunities for investigating many fundamental issues of nanocrystals, such as the formation of metallic state, and will have potential impact on condensed matter physics, nanochemistry, and catalysis as well.atomic precision | face-centered cubic | nanomolecule | plasmonic excitation N oble metal nanocrystals have attracted significant interest in both fundamental research and technological applications due primarily to their elegant surface plasmon resonance properties (1-6). Scientific studies on gold nanocrystals date back to Faraday's time in the nineteenth century (7). A classic procedure for the synthesis of gold nanocrystals is the citrate method, which produces quite uniform approximately 10-100 nm diameter nanocrystals with size tunable by controlling the ratio of sodium citrate to gold precursor (8, 9). Compared to the citrate-stabilized Au nanocrystals, thiolate-protected Au nanoparticles are more robust due to strong Au-SR bonds and have found important applications in biomedicine and many other fields (10-18). From the synthetic point of view, in all the previous synthetic works the obtained Au nanocrystals are more or less polydispersed, even the best quality Au nanocrystals achievable thus far-which still has a size dispersity of around 5-10%. Thus, it has long been a dream of nano-chemists to synthesize atomically precise, plasmonic nanocrystals for fundamental studies. Herein, we report the first example of atomically precise gold nanocrystals. Mass spectrometric analyses, in conjunction with other characterization, have determined its molecular formula to be Au 333 ðSRÞ 79 (where SR ¼ SCH 2 CH 2 Ph). This giant gold nanomolecule exhibits face-centered cubic (fcc) structure and surface plasmon resonance at approximately 520 ...

Monodisperse AuM (M=Pd, Rh, Pt) bimetallic nanocrystals for enhanced electrochemical detection of H2O2

“…Generally, metal nanomaterials were used to immobilize biomolecules due to their bio-conjugation ability, or used as catalysts to activate the electrochemical process. Many researches related to electrochemical sensors based on metal nanoparticles have mentioned that the metal loading, particle-size and stability had significant effects on the sensing performance [6][7][8][9].…”

Information on quantum states pervades the visible spectrum of the ubiquitous Au144(SR)60 gold nanocluster

“…This is particularly important at low energy where the intensity of the two small peaks at 1.36 and 1.50 eV, shown below to reflect the contribution of the 'staples' in the ligands, are overestimated in the calculation. An earlier report on the smaller Au 25 and Au 38 clusters 32 found that cooling causes an enormous increase in cross-section in the low-energy range (1.0-1.5 eV). Therefore, in addition to the emergence of the two peaks from the rather smooth spectrum at room temperature as demonstrated in our measurement (see Fig.…”

“…The prevalent view in recent decades has been that noble-metal clusters of intermediate size-that is, those with more than a few dozen but fewer than B10 3 metal atoms-necessarily have featureless optical absorption spectra of low information content in the near-IR, VIS and near-UV regions. At most, one expects a broad, smooth LSPR feature 25,26 . High information content is expected only in the mid-IR region 27 .…”

Nanotechnologies

“…Mass spectrometry analysis has determined the formula of gold nanocrystal molecules to be Au333(SR)79 (Qian et al 2012). This metallic nanocrystal molecule exhibits fcc-crystallinity and surface plasmon resonance (SPR) at ~7 to 720 nm.…”