Ordered Networks of Gold Nanoparticles Crosslinked by Dithiol‐Oligomers

Abstract

Controlled aggregation of nanoparticles into superlattices is a grand challenge in material science, where ligand based self‐assembly is the dominant route. Here, the self‐assembly of gold nanoparticles (AuNPs) that are crosslinked by water soluble oligo‐(ethylene glycol)‐dithiol (oEG‐dithiol) is reported and their 3D structure by small angle X‐ray scattering is determined. Surprisingly, a narrow region is found in the parameter space of dithiol linker‐length and nanoparticle size for which the crosslinked networks form short‐ranged FCC crystals. Using geometrical considerations and numerical simulations, the stability of the formed lattices is evaluated as a function of dithiol length and the number of connected nearest‐neighbors, and a phase diagram of superlattice formation is provided. Identifying the narrow parameter space that allows crystallization facilitates focused exploration of linker chemical composition and medium conditions such as thermal annealing, pH, and added solutes that may lead to superior and more robust crystals.

Interpolymer Complexation as a Strategy for Nanoparticle Assembly and Crystallization

“…To analyze the diffraction pattern, we use a model structure factor 22 as used in an earlier work on cross-linked AuNP assemblies using dithiol chains. 10 The best fit model to the diffraction pattern both in terms of peak positions and intensities is a face-centered-cubic (FCC) lattice with a primary peak at q 0 ≃ 0.038 Å −1 and a lattice constant a ≃ 286 Å. The nearest-neighbor (NN) distance is thus…”

“…Assembling nanoparticles into ordered structures is essential for applications in photonics, magnetic storage, spintronics, and other applications. − Thus, self-assembly of nanoparticles into ordered lattices (superlattices), where large scale ordered structures can be realized, has been the focus of research across multiple disciplines. , Specifically, self-assembly of metallic nanoparticles and quantum dots has been explored to obtain tunable optical properties. , A few approaches to achieving ordered structures have been developed, including solvent evaporation, DNA base-pairing, biphasic separation of water-soluble polymers, , and covalent cross-linking with small molecules . Among these, two of the illustrative approaches for 3D assembly of nanoparticles into superlattices are (1) solvent evaporation-induced assembly and (2) DNA-mediated assembly.…”

“…5,6 A few approaches to achieving ordered structures have been developed, including solvent evaporation, 1 DNA base-pairing, 7 biphasic separation of watersoluble polymers, 8,9 and covalent cross-linking with small molecules. 10 Among these, two of the illustrative approaches for 3D assembly of nanoparticles into superlattices are (1) solvent evaporation-induced assembly and (2) DNA-mediated assembly. Both methods have led to the formation of exquisite superlattices by engineering the core sizes, shapes, and ligand structure.…”

“…Clear diffraction rings in the 2D pattern with distinct peaks in the structure factor emerge, indicating a crystalline structure. To analyze the diffraction pattern, we use a model structure factor22 as used in an earlier work on crosslinked AuNP assemblies using dithiol chains 10. The best fit model to the diffraction pattern both in terms of peak positions and intensities is a face-centered-cubic (FCC) lattice with a primary peak at q 0 0.038 Å −1 , and a lattice constant a 286 Å.…”

D-shaped plastic optical fibre aptasensor for fast thrombin detection in nanomolar range

“…PEG and PEG-mixed SAMs have been reported to enable the determination of the biological markers straight from complex matrixes, such as blood, plasma or serum 19–22 . Furthermore, PEG-mix SAMs have been exploited for their ability to work in aqueous conditions 23–27 , thus being ideal for protein biomarker determinations, such as the case of THR. In the literature, both long 17,28 and short PEG-SAM chains 29–31 are reported.…”