A general method for precise chain assembly of noble metal nanoparticles

Salt-induced aggregation is a convenient method for obtaining chains of Au nanoparticles, but it only applies to small nanoparticles (<15 nm) and often with branched and globular aggregates as the by-products. By mechanistic investigation and rational design of reaction conditions, we show that the modulation of ligand concentration and solvent polarity are more effective for chain aggregation, which is also consistent with the DLVO theory. Our method gives precise chain aggregates (error ratio similar to 4%), which were verified via silica encapsulation. It can be broadly applied to noble metal nanoparticles of various sizes and a wide variety of ligands, including surface-enhanced Raman scattering (SERS)-active ones.

Automated summary

Salt-induced aggregation is a convenient method for obtaining chains of small Au nanoparticles (<15 nm), but often leads to branched and globular aggregates as by-products. By investigating the mechanism and designing reaction conditions, we found that modulating ligand concentration and solvent polarity are more effective for precise chain aggregation, consistent with DLVO theory. Our method can be applied to noble metal nanoparticles of various sizes with different ligands, including SERS-active ones, producing chain aggregates with low error ratio (around 4%).