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Digestive ripening (DR) is a synthetic method where a polydisperse colloid of metal nanoparticles upon refluxing with a free ligand in a high boiling point solvent gives monodisperse nanoparticles. Brust synthesis is known to form atomically monodisperse thiolate protected gold nanoparticles also known as gold nanomolecules (Au NMs). Unlike the Brust method which gives smaller (1–3 nm) atomically precise nanomolecules, DR has been used only for the synthesis of large nanoparticles (>5 nm) with good monodispersity. In thiolate protected gold nanoparticle Brust synthesis, the yellow colored phase transferred Au( iii ) solution is converted to a colorless Au( i ) mixture after the addition of thiol by forming Au–SR, which is then reduced to form black colored Au NMs. However, in DR, by using the same primary chemicals, the two steps were reversed: the mixture was reduced before the addition of thiol. Here we show that in DR, adding thiol after 2 minutes of reduction gives larger particles (5 nm) as reported, whereas adding thiol 30 seconds after reduction results in smaller particles (<2 nm). In this work, for the first time, DR yields atomically precise Au 25 (SR) 18 and Au 144 (SR) 60 NMs. This is reported using two aliphatic thiols – hexanethiol and dodecanethiol – as the protecting ligands. DR was also repeated using an aromatic thiol, 4- tert -butyl benzene thiol (TBBT), which yields Au 279 (SR) 84 NMs consistent with the Brust method, thereby establishing that both DR and Brust methods lead to the formation of atomically precise Au NMs, regardless of the order of thiol addition and reduction steps.
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Electrospray Gold Standards of Molecular Mass 32- to 52-kDa: Charging Patterns of the Ubiquitous Virus-like Clusters, I - 197Au144-5(SR)60, R = 8 Variants, in Native [HPLC]-ESI-MS
Faradays legendary Molecules of Gold have stimulated intense interest (over 165 years) but have only recently begun to yield their secrets to modern methods of chemical analysis. Here(in), we demonstrate how striking charging patterns emerge directly from native electrospray of large, gold-rich molecules that were generated by reduction of various (8) small gold(I)thiolate complexes [-RS-Au(I)-SR-], followed by extensive thermochemical processing to enrich the most robust forms. In each case (R), electrospray ionization of a picomolar solution yields a characteristic series of abundant, highly resolved peaks at related (m/z)-ratios, that can be used to deduce charges {z e+} and hence a distinct molecular mass, {MR}. A plot of {MR} versus thiolate-mass {mL} yields a straight line with slope 60.0 (the ligand count) and an intercept of 28,364-Da, the mass of 144 Au-atoms. i.e., a unique molecular composition {197Au144(SR)60}. This formula agrees with the unique chiral-icosahedral structure-model, c@12@42@60@(30,60), the Pd145(CO)60-structure, that features a massively-compact globular Au114-core (~1.6-nm) and an intrinsically chiral (I) outer shell (~2.0-nm) with 12 distinct ligand types of 5-fold equivalence], denoted by Martin et al. as virus-like on the basis of its resemblance of icosahedral-virus capsids.
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- Award ID(s):
- 2108044
- PAR ID:
- 10418112
- Date Published:
- Journal Name:
- ChemRxiv
- ISSN:
- 2573-2293
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Since their discovery, thiolate-protected gold nanoclusters (Au n (SR) m ) have garnered a lot of interest due to their fascinating properties and “magic-number” stability. However, models describing the thermodynamic stability and electronic properties of these nanostructures as a function of their size are missing in the literature. Herein, we employ first principles calculations to rationalize the stability of fifteen experimentally determined gold nanoclusters in conjunction with a recently developed thermodynamic stability theory on small Au nanoclusters (≤102 Au atoms). Our results demonstrate that the thermodynamic stability theory can capture the stability of large, atomically precise nanoclusters, Au 279 (SR) 84 , Au 246 (SR) 80 , and Au 146 (SR) 57 , suggesting its applicability over larger cluster size regimes than its original development. Importantly, we develop structure–property relationships on Au nanoclusters, connecting their ionization potential and electron affinity to the number of gold atoms within the nanocluster. Altogether, a computational scheme is described that can aid experimental efforts towards a property-specific, targeted synthesis of gold nanoclusters.more » « less
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.26434/chemrxiv-2023-sbhsk
