Kinetic Study on the Self-Assembly of Au(I)–Thiolate Lamellar Sheets: Preassembled Precursor vs Molecular Precursor

Abstract

Molecular self-assembly has played an important role in nanofabrication. Due to the weak driving forces of noncovalent bonds, developing molecular nanoassemblies that have both robust preparation conditions and stable structure is a challenge. In our previous work, we have developed a reversible self-assembly system of Au(I)-thiolate coordination polymer (ATCP) to form colloidal lamellar sheets and demonstrated the high tailorability and stability of their structures, as well as their promising applications in gold nanocluster/nanoparticle fabrication and UV light shielding. Here, we first reported our progress in exploring a robust and green assembly protocol toward ATCP colloidal lamellar sheets in water by allowing the molecular precursors of HAuCl and the thiol ligand to form ATCP preassembled intermediates. In this way, colloidal ATCP lamellar sheets can be prepared in a wide range of synthetic concentrations ([Au] ≥ 2 × 10 M) and at broad assembly temperatures (80-100 °C) with similar high yields (>80%). The assembly kinetics at different conditions are also studied in detail to help understand the robust assembly process. The robust and green synthetic protocols will pave a way for their real applications.

Reactions Coupled Self‐ and Co‐Assembly: A Highly Dynamic Process and the Resultant Spatially Inhomogeneous Structure

“…The synthesis of Au I ‐thiolate is through the reaction of Au III ions and thiol ligands in aqueous phase at boiling temperature . Au III ions were first reduced by thiol ligands to Au I and then coordinated with the residual thiol ligands to form linear coordination polymer chains instantly [equation (1)].…”

Self‐Templated Assembly of AuI/AgI‐Thiolate Sheets with Central Holes

“…The absorptionf or the Au I -thiolate-Sheets at 380 nm appeared immediatelyu pon mixingo ft he two at room temperature (Figure3a, 3b), while it is hard forA u I -thiolate-Strings themselves to transform to Au I -thiolate-Sheets at room temperature. [34] XPS data reveal about 51 %o ft he Au I -thiolate-Strings covers on the cores at this stage. For pure Au I -thiolate-Sheets, the first absorption peak will shift from % 380 nm to 390 nm as their size increases from tens of nanometre to hundreds of nanometre.…”

“…With the help of Ag I ‐thiolate‐Nanoparticles as seeds, the crystallization of Au I ‐thiolate‐Strings is faster than that without the seeds (Figure S7, S10). The absorption for the Au I ‐thiolate‐Sheets at 380 nm appeared immediately upon mixing of the two at room temperature (Figure 3 a, b), while it is hard for Au I ‐thiolate‐Strings themselves to transform to Au I ‐thiolate‐Sheets at room temperature . XPS data reveal about 51 % of the Au I ‐thiolate‐Strings covers on the cores at this stage.…”

“…Component of Au I ‐thiolate was synthesized by reaction of HAuCl 4 with excess MPA‐Na (4 equivalents) in water at room temperature. Two equivalents of thiols first reduce Au III to Au I and then the remaining thiols coordinate with Au I to form Au I ‐thiolate . In contrast to the Ag I ‐thiolate, Au I ‐thiolate monomers/oligomers (Au I ‐thiolate‐Mono‐/Oligomer) forms amorphous string‐like intermediates which are very small and nearly invisible in TEM images (Au I ‐thiolate‐Strings, yield by dialysis: ≈100 %, Figure S2 a,f).…”

“…Twoe quivalents of thiols first reduce Au III to Au I and then the remaining thiols coordinatew ith Au I to form Au Ithiolate. [30][31][32][33][34][35] In contrastt ot he Ag I -thiolate, Au I -thiolate monomers/oligomers (Au I -thiolate-Mono-/Oligomer) forms amorphous string-like intermediates which are very small andn early invisible in TEM images [34] (Au I -thiolate-Strings, yield by dialysis: % 100 %, Figure S2 a,f). Au I -thiolate-Strings further grow longer, aggregate and crystallize to form sheetsatboilingtemperature (Au I -thiolate-Sheets, separation yield by centrifugation: % 80 %, Figure 1h,S 2b-f).…”