Strong and Elastic Membranes via Hydrogen Bonding Directed Self‐Assembly of Atomically Precise Nanoclusters

Abstract

They are classically prepared using exfoliation, exploiting promoted intralayer bonding over weak interlayer interactions of their 3D counterparts. [4] The exfoliation of graphene [1] has triggered searches for other covalently interconnected atomically thin 2D nanomaterials, such as transition metal dichalcogenides, [5] Mxenes, [6] boron nitrides, [7] and clays, [8] based on exfoliation and delamination, [9] molecular beam epitaxy, [10] and advanced synthesis. [11] In ultrathin 2D nanomaterials, the quantum confinement of electrons in two dimensions opens novel applications, e.g., in flexible optoelectronic devices. [4,12,13] Beyond atomic and molecular-level networks, a less studied approach deals with the selfassembly of metal nanoparticles (NPs) to form 2D monolayer membranes, i.e., of nanometric thickness. That this could be relevant, is suggested by the tunable optoelectronic and mechanical properties of self-assembled 2D materials of narrow size dispersed plasmonic NPs. [14][15][16][17] However, metal NPs classically suffer from uncontrolled aggregation tendency, polydispersity, and lack of directional interactions. [18][19][20][21] Additionally, nonspecific bindings and slow diffusion of colloidal-level 2D nanomaterials have provided an extraordinary palette of mechanical, electrical, optical, and catalytic properties. Ultrathin 2D nanomaterials are classically produced via exfoliation, delamination, deposition, or advanced synthesis methods using a handful of starting materials. Thus, there is a need to explore more generic avenues to expand the feasibility to the next generation 2D materials beyond atomic and molecular-level covalent networks. In this context, self-assembly of atomically precise noble nanoclusters can, in principle, suggest modular approaches for new generation 2D materials, provided that the ligand engineering allows symmetry breaking and directional internanoparticle interactions. Here the self-assembly of silver nanoclusters (NCs) capped with p-mercaptobenzoic acid ligands (Na 4 Ag 44 -pMBA 30 ) into large-area freestanding membranes by trapping the NCs in a transient solvent layer at air-solvent interfaces is demonstrated. The patchy distribution of ligand bundles facilitates symmetry breaking and preferential intralayer hydrogen bondings resulting in strong and elastic membranes. The membranes with Young's modulus of 14.5 ± 0.2 GPa can readily be transferred to different substrates. The assemblies allow detection of Raman active antibiotic molecules with high reproducibility without any need for substrate pretreatment.

Vertically Aligned Nanoplates of Atomically Precise Co6S8 Cluster for Practical Arsenic Sensing

“…We note that the oriented assembly of nanoclusters leading to specific morphology, such as nanosheets, fibers, etc. , was observed earlier. − …”

Dissociative reactions of [Au25(SR)18]− at copper oxide nanoparticles and formation of aggregated nanostructures

“…Recently, NCs have been used as attractive nanoscale building blocks to fabricate 3D superstructures via colloidal self-assembly. 9,53,54 Exploring selfassemblies of NPs has been a hot topic in nanotechnology for the past few years and it remains relevant due to the tunable collective properties as well as the remarkable applications of the superstructures in a wide range of fields. The inter-nanocluster interactions play a vital role in the novel properties of metal nanoparticle assemblies.…”

“…55 Multidimensional close-packed nanocluster-based molecular aggregates have been achieved using evaporationinduced assembly, interfacial assembly, binary solventinduced assembly, the antisolvent approach, dip coating, and the Langmuir-Blodgett method. [56][57][58] Still, achieving a combination of precision and reproducibility of self-assembled largearea NP superstructures remains a grand challenge. Metal NPs too exhibit polydispersity, a tendency toward uncontrolled aggregation, and a lack of directional inter-nanoparticle interactions.…”

Precision Nanocluster‐Based Toroidal and Supertoroidal Frameworks Using Photocycloaddition‐Assisted Dynamic Covalent Chemistry

“…[ 6 ] These directional forces have the potential to arrange NCs into supramolecular superstructures including 2D crystals, [ 7 ] colloidal capsids, [ 7 ] frameworks, [ 8 ] and macroscopic elastic membranes. [ 9 ] Such structures have potential applications in gas sensing or storage, [ 10 ] green catalysis, [ 11 ] light‐emitting devices, [ 12 ] and theranostics. [ 13 ] NC self‐assembly has also been demonstrated using light‐responsive surface ligands.…”