Bulky Adamantanethiolate and Cyclohexanethiolate Ligands Favor Smaller Gold Nanoparticles with Altered Discrete Sizes

Abstract

Use of bulky ligands (BLs) in the synthesis of metal nanoparticles (NPs) gives smaller core sizes, sharpens the size distribution, and alters the discrete sizes. For BLs, the highly curved surface of small NPs may facilitate growth, but as the size increases and the surface flattens, NP growth may terminate when the ligand monolayer blocks BLs from transporting metal atoms to the NP core. Batches of thiolate-stabilized Au NPs were synthesized using equimolar amounts of 1-adamantanethiol (AdSH), cyclohexanethiol (CySH), or n-hexanethiol (C6SH). The bulky CyS- and AdS-stabilized NPs have smaller, more monodisperse sizes than the C6S-stabilized NPs. As the bulkiness increases, the near-infrared luminescence intensity increases, which is characteristic of small Au NPs. Four new discrete sizes were measured by MALDI-TOF mass spectrometry, Au(30)(SAd)(18), Au(39)(SAd)(23), Au(65)(SCy)(30), and Au(67)(SCy)(30). No Au(25)(SAd)(18) was observed, which suggests that this structure would be too sterically crowded. Use of BLs may also lead to the discovery of new discrete sizes in other systems.

Modulating the Physicochemical and Structural Properties of Gold-Functionalized Protein Nanotubes through Thiol Surface Modification

“…They explained that during NP synthesis, steric overlapping of the voluminous ligands avoids the incorporation of more metal ions to the active surfaces of growing clusters, blocking the growth process and resulting in smaller NP sizes. 45 It is possible to infer from our results that a similar phenomenon occurred to the metal clusters attached to the protein nanotubes when GlcC 5 SH was used as coating compound.…”

“…It has also been demonstrated that bulkier ligands prevent the growth of gold clusters, limiting their size. 45 To test whether this phenomenon occurred in our system employing viral scaffolds in combination with thiols, the synthesis of Au NP was performed in the presence of β-D-glucopyranoside 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 10 (GlcC 5 SH), which has a larger size than MPS (Figure 3). This glyco-ligand can confer biocompatibility to gold nanocomplexes while avoiding their aggregation.…”

Controlled metal nanostructures: Fertile ground for coordination chemists

“…Bulky ones, e.g. bearing an adamantane or carbohydrate backbone, are more efficient stabilizers and help stabilize MNPs of small sizes [85], [86]. .…”

N-Heterocyclic Carbene Ligands for Au Nanocrystal Stabilization and Three-Dimensional Self-Assembly

“…This is consistent with previous studies showing that bulky thiol ligands resulted in smaller core sizes by comparison with nonbulky ligands. 66 It is likely that the C14 alkyl chains of L3 – L5 increase the volume of the NHC ligand close to the surface of the metallic core. This is particularly significant for L3 in which the intramolecular steric interactions between the long alkyl chains may lead to the largest ligand size (Figure 13).…”