Two-Dimensional DNA-Programmable Assembly of Nanoparticles at Liquid Interfaces

Abstract

DNA-driven assembly of nanoscale objects has emerged as a powerful platform for the creation of materials by design via self-assembly. Recent years have seen much progress in the experimental realization of this approach for three-dimensional systems. In contrast, two-dimensional (2D) programmable nanoparticle (NP) systems are not well explored, in part due to the difficulties in creating such systems. Here we demonstrate the use of charged liquid interfaces for the assembly and reorganization of 2D systems of DNA-coated NPs. The absorption of DNA-coated NPs to the surface is controlled by the interaction between a positively charged lipid layer and the negatively charged DNA shells of particles. At the same time, interparticle interactions are switchable, from electrostatic repulsion between DNA shells to attraction driven by DNA complementarity, by increasing ionic strength. Using in situ surface X-ray scattering methods and ex situ electron microscopy, we reveal the corresponding structural transformation of the NP monolayer, from a hexagonally ordered 2D lattice to string-like clusters and finally to a weakly ordered network of DNA cross-linked particles. Moreover, we demonstrate that the ability to regulate 2D morphology yields control of the interfacial rheological properties of the NP membrane: from viscous to elastic. Theoretical modeling suggests that the structural adaptivity of interparticle DNA linkages plays a crucial role in the observed 2D transformation of DNA-NP systems at liquid interfaces.

Ionic depletion at the crystalline Gibbs layer of PEG-capped gold nanoparticle brushes at aqueous surfaces

“…At the same time, assembling NPs into two-dimensional (2D) crystalline and noncrystalline structures have also been developed. In one approach, charged Langmuir monolayers have been used as templates that attract and crystallize capped nanoparticles from solutions [5][6][7]. In a different approach, it has been found that by manipulating salt concentrations in NPs suspensions, a Gibbs-like monolayer can be spontaneously formed and crystallized [8][9][10].…”

“…In a different approach, it has been found that by manipulating salt concentrations in NPs suspensions, a Gibbs-like monolayer can be spontaneously formed and crystallized [8][9][10]. It should be emphasized that for all these assemblies, 2D or 3D, salts play a decisive role in tweaking the charge of the DNA strands and facilitate specific 3D assembly of NPs or migration of NPs to the liquid interface [5][6][7][8][9][10]. In fact, a recent study suggests that the underlying mechanism that drives DNA-capped AuNPs to the surface and to crystallization has to do with the role of salt in tweaking the hydrophobic-hydrophilic character of the DNA-capped AuNPs [10].…”

Tuning Morphologies of Langmuir Polymer Films Through Controlled Relaxations of Non-Equilibrium States

“…The behavior of LPFs has been intensively studied in the context of controlled self-assembly of homo-and block copolymers, 1−3 rheology of monolayers, 3−5 glass transition behavior of polymeric systems in 2D-or quasi 2D-confinement, 6,7 and structure formation in biological systems. 8,9 Monroy and coworkers made pioneering contributions to investigate the dynamic behavior of Langmuir films of flexible polymers prepared by subsequent material deposition to increase the surface density. 10−12 They showed that the air−water interface represents good solvent conditions for their chosen polymers [poly(vinyl-acetate) and poly(tert-butyl acrylate)].…”

High Strength, Molecularly Thin Nanoparticle Membranes

“…Experimentally, single NP membranes have been formed in a variety of ways, including using evaporation induced ordering [3,7] and DNA-programmable NPs [8]. In the case of evaporation induced ordering, NPs are driven by evaporation to the liquid/vapor interface [7].…”