Organic mediator-induced structural transformation in superlattices of monolayer-protected gold nanoparticles

N-acetylglutathione (NAG)-protected gold nanoparticles self-assemble into three-dimensional (3D) face-centered cubic (fcc)-type superlattices at an air/water interface under highly acidic conditions. To prepare the well-defined superlattices, 1 month’s incubation is at least necessary since the size growth of the as-prepared nanoparticles is essential. Addition of 4-pyridinecarboxyic acid (PyC), a bifunctional hydrogen-bonding mediator, promotes the formation of the superlattices, which are created for about 2 weeks’ storage. Interestingly, PyC-induced nanoparticle superlattices are in a body-centered tetragonal (bct) structure. The fcc-to-bct phase transformation would be due to stronger interaction between NAG and PyC than that between NAG molecules on the gold nanoparticle surfaces.

Graphical abstractThe superlattices of N-acetylglutathione-protected gold nanoparticles experience fcc-to-bcc structural transformation through the interparticle mediation by 4-pyridinecarboxyic acid.Figure optionsDownload full-size imageDownload high-quality image (86 K)Download as PowerPoint slideResearch highlights► N-acetylglutathione-protected gold nanoparticles self-assemble to form fcc-type superlattices. ► 4-Pyridinecarboxylic acid (PyC) mediator promotes the formation of the superlattices. ► The PyC-induced nanoparticle superlattices experience structural transformation into a bct phase. ► The transformation is explained by elongation or contraction of the lattice parameters under strain.