Gold Nanoparticle Assemblies on Surfaces: Reactivity Tuning through Capping-Layer and Cross-Linker Design

• Published in: Chemistry : a European journal 2016-01, Vol.22 (5), p.1728-1734
• Main Authors: Shankar, Sreejith, Orbach, Meital, Kaminker, Revital, Lahav, Michal, van der Boom, Milko E.
• Format: Article
• Language: English
• Subjects: Aggregates; aggregation; Assemblies; Capping; capping layer; Chemistry; coordination modes; cross-linkers; Crosslinking; Design; Gold; Hydrophilicity; Hydrophobicity; Immobilization; Islands; Metals; Nanoparticles; Networks; Structural stability; Surface stability; surfaces; Tuning
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201503297

The immobilization of metal nanoparticles (NPs) with molecular control over their organization is challenging. Herein, we report the formation of molecularly cross‐linked AuNP assemblies using a layer‐by‐layer approach. We observed four types of assemblies: 1) small aggregates of individual AuNPs, 2) large aggregates of individual AuNPs, 3) networks of fused AuNPs, and 4) gold islands. Interestingly, these assemblies with the different cross‐linkers and capping layers represent different stages in the complete fusion of AuNPs to afford islands of continuous gold. We demonstrate that the stability toward fusion of the nanoparticles of the on‐surface structures can be controlled by the reactivity of the cross‐linkers and the hydrophilicity/hydrophobicity of the nanoparticles. NPs@surfaces: Molecular cross‐linkers direct the immobilization of two different gold nanoparticles (AuNPs) on different substrates. Aggregates and island‐like films were obtained by using two electronically different cross‐linkers and two types of AuNPs with hydrophilic or hydrophobic capping layers (see figure; Cit=citrate, TOAB=tetraoctylammonium bromide).