Colloidal synthesis of nanoparticles is a complex process, which is subject to both thermodynamic and kinetic restrictions. Understanding and controlling these thermodynamic and kinetic parameters are critical for the reproducible and reliable synthesis of nanoparticles. A common thermodynamic parameter is the reduction potential of the reactants, whose role in nano-synthesis is not yet well understood. Here we show that different types of penta-twinned NPs (spheroid, bipyramid, and decahedron) with adjustable size can be prepared in one system with high purity by simply varying the initial pH of the growth solution. The effect of pH was mainly attributed to the regulation of the reduction potential of reductants (RPRs), which determines the atomic deposition preference on the penta-twinned seed surface due to the lattice strain energy at the twin boundary, and then the way it grows into the final products. To explore the quantitative relationship between reduction potential and synthetic products, a series of phenol derivatives with similar structure (4-R-phenol) but different standard reduction potential was chosen as reductants, where R is chlorine, hydrogen, methyl, and methyl oxide, respectively. For each phenol derivative we tested, it was found that there is an appropriate pH range, in which GBPs of high quality were synthesized and their longitudinal LSPR peak red shifted with the increase of the initial pH value. This pH range is related to the substituent on phenol, those with electron-withdrawing groups are higher while those with electron-donating groups are lower. Although these phenol derivatives have different working pH ranges, the plots of the longitudinal LSPR peak of their resultant products versus the pH are quite similar. When pH was substituted by the corresponding reduction potential calculated from the Nernst equation, these plots coincide together, meaning that the influence of reduction potential on the formation of GBPs is independent of the specific phenol derivatives (reductants), so the reduction potential is a fundamental parameter in the synthesis of GBPs. This role of reduction potential is expected to be general in the synthesis of other types of nanoparticles, which is important not only for understanding the mechanism of nano-synthesis but for improving the reproducibility and reliability of nano-synthesis.

The essential role of reduction potential in the seed-mediated synthesis of penta-twinned gold nanoparticles

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.