Hydrogen Bonding Directed Colloidal Self‐Assembly of Nanoparticles into 2D Crystals, Capsids, and Supracolloidal Assemblies

Abstract

Self-assembly of colloidal building blocks, like metal nanoparticles, is a rapidly progressing research area toward new functional materials. However, in-depth control of the colloidal self-assembly and especially hierarchical self-assembly is difficult due to challenges in controlling the size dispersities, shape/morphology, directionalities, and aggregation tendencies. Using either polydispersed or narrow-size dispersed nanoparticles, considerable progress has been achieved over the past few years. However, absolutely monodisperse nanoparticles could allow new options for rational designs of selfassemblies. Therein, atomically precise monolayer protected nanoclusters (d < 3 nm) have recently been synthesized with well-defined metal cores and surface ligands. Their dispersion behavior is commonly tuned by surfactantlike ligands. Beyond that, this study deals with approaches based on liganddriven supramolecular interactions and colloidal monodispersity until atomic precision to tune the colloidal self-assembly and hierarchy from nanoscale to mesoscopic scale. Therein colloidal packing to self-assembled 2D crystals and closed virus capsid-inspired shells provide relevant research goals due to ever increasing potential of 2D materials and encapsulation. This study addresses the hydrogen bonding (H-bonding) directed self-assembly of atomically precise gold and silver nanoparticles and narrow size dispersed cobalt nanoparticles to free-standing 2D colloidal nanosheets, nanowire assemblies, capsid-like colloidal closed shells, as well as higher order structures.

Atomically Precise Nanocluster Assemblies Encapsulating Plasmonic Gold Nanorods

“…Figure d (Supporting Information, Video S4) show the TEM tomography reconstruction of GNR@Au 250 (Figure e shows the graphical representation of the same). Absence of any specific morphology in this case, even on completion of the reaction, can be due to the fact that Au 250 has to be partially deprotonated to facilitate water dispersibility . As a result, not all of the ligands are involved in H‐bonding, which decreases the packing density.…”

“…Recent reports of inter‐nanocluster reactions and isomorphous transformations have expanded the scope of their science. Moreover, it has been recently shown that by tuning the inter‐nanocluster H‐bonding, free‐standing 2D nanosheets and capsids with monolayer thick shells can be achieved using p MBA‐protected gold nanoclusters . On the other hand, noble metal nanoparticles, especially gold nanorods (GNRs), owing to their anisotropic surface plasmonic excitations and extreme sensitivity to chemical environments have been one of the most intensely researched nanosystems.…”

Atomically Precise Nanocluster Assemblies Encapsulating Plasmonic Gold Nanorods

“…Absence of any specific morphology in this case, even on completion of the reaction, can be due to the fact that Au 250 has to be partially deprotonated to facilitate water dispersibility. [6,7] As aresult, not all of the ligands are involved in H-bonding, which decreases the packing density.S imilar structures have been obtained on treating GNRs with Au 102 (Supporting Information, Figure S10). Thus,i rrespective of the solvent this approach can be useful to condense any noble metal nanocluster,p rotected by hydrogen-bond-forming ligand on GNRs,which act as the nucleating sites.…”

“…Figure 3d (Supporting Information, Video S4) show the TEM tomography reconstruction of GNR@Au 250 (Figure 3e shows the graphical representation of the same). [6,7] As aresult, not all of the ligands are involved in H-bonding, which decreases the packing density.S imilar structures have been obtained on treating GNRs with Au 102 (Supporting Information, Figure S10). [6,7] As aresult, not all of the ligands are involved in H-bonding, which decreases the packing density.S imilar structures have been obtained on treating GNRs with Au 102 (Supporting Information, Figure S10).…”

“…Atomically precise monolayer-protected nanoclusters of noble metals [1][2][3] such as Au 25 (SR) 18 ,A g 25 (SR) 18 ,A g 44 (SR) 30 , and Au 102 (SR) 44 owing to their small size and quantum confinement of electrons lead to discrete energy levels, making their optical absorption spectra reminiscent of dye molecules.N ear-infrared emission and unusual catalysis are some of the fascinating properties of such clusters.O ver the past one decade,t here has been tremendous progress in the synthesis,c haracterization, and studies of their diverse properties.R ecent reports of inter-nanocluster reactions [4] and isomorphous transformations [5] have expanded the scope of their science.M oreover,i th as been recently shown that by tuning the inter-nanocluster H-bonding,free-standing 2D nanosheets and capsids with monolayer thick shells can be achieved using pMBA-protected gold nanoclusters. [6,7] On the other hand, noble metal nanoparticles,e specially gold nanorods (GNRs), [8,9] owing to their anisotropic surface plasmonic excitations and extreme sensitivity to chemical environments have been one of the most intensely researched nanosystems. Theu nique plasmonic properties of gold nanoparticles have been exploited recently to achieve plasmon-molecular resonance coupling using small organic dye molecules [10] as well as quantum dots.…”