Spontaneous Self-Assembly of Silver Nanoparticles into Lamellar Structured Silver Nanoleaves

Uniform lamellar silver nanoleaves (AgNLs) were spontaneously assembled from 4 nm silver nanoparticles (AgNPs) with p-aminothiophenol (PATP) as mediator under mild shaking at room temperature. The compositions of the AgNLs were verified to be 1 nm Ag25 nanoclusters and PATP molecules in quinonoid model. The underlying assembly mechanism was systematically investigated and a two-step reaction process was proposed. First, the 4 nm AgNPs were quickly etched to 1 nm Ag25 nanoclusters by PATP in the form of [Ag25(PATP)n]n+ (n < 12), which were then further electrostatically or covalently interconnected by PATP to form the repeated unit cells of [Ag25(PATP)n−1](n−1)+–PATP–[Ag25(PATP)n−1](n−1)+ (abbreviated as Ag25–PATP–Ag25). Second, these Ag25–PATP–Ag25 complexes were employed as building blocks to construct lamellar AgNLs under the directions of the strong dipole–dipole interaction and the π–π stacking force between the neighboring benzene rings of PATP. Different reaction parameters including the types and concentrations of ligands, solvents, reaction temperature, ionic strength, and pH, etc., were carefully studied to confirm this mechanism. Finally, the preliminary investigations of the applications for AgNLs as “molecular junctions” and SERS properties were demonstrated. We expect that this convenient and simple method can be in principle extended to other systems, or even mixture system with different types of NPs, and will provide an important avenue for designing metamaterials and exploring their physicochemical properties.

Has been reported a convenient and simple approach to spontaneously assemble AgNPs into uniformly lamellar AgNLs with PATP molecule as mediator. The self-assembly mechanism has been experimentally elucidated as (1) the formation of uniform 1 nm Ag25 nanoclusters obtained from the etching of 4 nm AgNPs by PATP; (2) the formation of the quinonoid model of PATP with the electrostatical/covalent interaction between −HS/–NH2 and AgNP resulting in the Ag25–PATP–Ag25 complex as a building block; (3) the strong dipole–dipole interaction and the π–π stacking force between the neighboring rigid benzene skeleton of PATP induced the ordered organization of Ag25–PATP–Ag25 complexes into lamellar AgNLs. They expect that this methodology will provide an important avenue for designing new metamaterials and exploring their novel physicochemical properties.

Reference
Spontaneous Self-Assembly of Silver Nanoparticles into Lamellar Structured Silver Nanoleaves
Lun Li and Qiangbin Wang
ACS Nano Article ASAP