RESUMO
A molecular cage encapsulating gold nanoparticles is presented. Six benzylic thioethers are pointing into its cavity, stabilizing the particles in a 1 : 1 ligand-to-particle-ratio in excellent yields. They are bench-stable for several months and can withstand unprecedented thermal stress of up to 130 °C, documenting the advantages of the cage-type stabilization over open-chain analogues.
RESUMO
The design and synthesis of a novel linear thioether-based ligand subunit with a tetraphenylmethane core used in the stabilisation of gold nanoparticles (AuNPs) are presented. Mono-, tri, penta- and heptamers of the ligand have been synthesised and used to stabilise AuNPs by enwrapping. With the exception of the monomer, all ligands provide reliable long-term stability and redispersibility for the coated nanoparticles in common organic solvents. Despite variation of the oligomer length, all stable particles were of the same size within error tolerance (1.16±0.32â nm for the trimer, 1.15±0.30â nm for the pentamer, 1.17±0.34â nm for the heptamer), as investigated by transmission electron microscopy (TEM). These findings suggest that not only the number of sulfur atoms in the ligand, but also its bulkiness play a crucial role in stabilising the AuNPs. These findings are supported by thermogravimetric analysis (TGA), showing that AuNPs stabilised by the penta- or heptamer are passivated by a single ligand. Thermal stability measurements suggest a correlation between ligand coverage and thermal stability, further supporting these findings.