Size-Defined Cracked Vesicle Formation via Self-Assembly of Gold Nanoparticles Covered with Carboxylic Acid-Terminated Surface Ligands

Abstract

The self-assembly of gold nanoparticles (GNPs) into a defined structure, particularly hollow capsule structures, provides great potential for applications in materials science and medicine. However, the complexity of the parameters for the preparation of those structures through self-assembly has limited access to critical mechanistic questions. With this in mind, we have studied GNP vesicle (GNV) formation through self-assembly by the surface modification of GNPs with low-molecular-weight ligands. Here, we successfully prepared GNVs composed of GNPs with a diameter of 30 nm by surface modification with carboxylic acid-terminated fluorinated oligo(ethylene glycol) ligands (CFLs). As the carboxylic acid has two states (protonated and deprotonated), the balance of the attraction and repulsion between GNPs covered with CFLs is tunable. Sodium carboxylate-terminated fluorinated oligo(ethylene glycol) ligands (SCFLs) provided smaller GNVs than did CFLs at 0.8 × 10 NPs/mL. Time-course study revealed that CFL-covered GNPs quickly form small aggregates and gradually grow to larger GNVs (ca. 200 nm), but no gradual growth was observed for SCFL-covered GNPs. This result indicated that the electrostatic repulsion inhibits fusion of the small GNVs. The size of the GNVs formed with the aid of CFLs was independent of the initial GNP concentration, but the extinction spectra were concentration-dependent. Electron microscopy imaging and simulations supported the defect formation in the assemblies. These results provided new insights into the vesicle formation mechanism.

Micro-liquid enclosure array and its semi-automated assembling system for x-ray free-electron laser diffractive imaging of samples in solution

“…33 We measured self-assembled vesicles of GNPs in dioxane containing 4% water. 34 The sample has been developed aiming to utilize as a stimuli-responsive drug delivery carrier or an enhancer in surface-enhanced Raman scattering and was prepared via self-assembly of 30 nm-diameter GNPs with carboxylic acid-terminated fluorinated oligo(ethylene glycol) ligands. 34,35 worrying about clogging.…”

“…34 The sample has been developed aiming to utilize as a stimuli-responsive drug delivery carrier or an enhancer in surface-enhanced Raman scattering and was prepared via self-assembly of 30 nm-diameter GNPs with carboxylic acid-terminated fluorinated oligo(ethylene glycol) ligands. 34,35 worrying about clogging. In the measurement, a single-particle hit rate of 31% and a multiple-particle hit rate of 6% were achieved.…”

Vesicle Formation by the Self-Assembly of Gold Nanoparticles Covered with Fluorinated Oligo(ethylene glycol)-Terminated Ligands and Its Stability in Aqueous Solution

“…33,34 To further prove that the competing interactions including attraction and repulsion contributed to GNV formation, a carboxylic acidterminated fluorinated oligo(ethylene glycol) ligand (CFL) was designed to self-assemble with 30 nm GNPs into vesicles. 35 In the case of GFL-or CFL-related ligands, we focused on the direction of increasing attraction or introducing a charge on the surface ligands compared with that of SFLs; however, the GNVs in our previous report could be dispersed in an organic solvent but collapsed after transfer into water. 32 For biological applications, the development of new small surface ligands to fabricate stable GNVs in aqueous solution is an ongoing challenge.…”

“…In the case of the self-assembly for GNV formation based on small molecules, the balance between interparticle attraction and repulsion, which are principally contributed by the ligands on the surface of GNPs, is important. − Compared with multicomplex polymers, the self-assembly using the small surface ligands with low molecular weights and controllable interactions to cover GNPs for GNV formation are suitable for their mechanistic studies and are desirable for their plasmonic characteristics. − Therefore, the design of small organic ligands with unique surface features and controllable inter- or intramolecular interactions for GNV formation is an important fundamental research direction. Most previously reported small surface ligands for GNV formation are based on a solvophilic head linked with a solvophobic part. − A balance between the solvophilic and solvophobic parts of a ligand is important for GNV formation. Recently, we developed a nontemplated self-assembly approach to fabricate GNVs using a semifluorinated oligo­(ethylene glycol) ligand (SFL), a small organic molecule, tethered GNPs with sizes of 5, 10, and 20 nm based on the solvophobic effects .…”

Nanoscale uniformity in the active tuning of a plasmonic array by polymer gel volume change

“…[14][15][16] On the other hand, although it remains challenging, active tuning of the plasmonic nanostructures is thought to have greater potential due to the plasmon coupling effects, which are induced when the metal nanostructures are in close proximity, as a new plasmon resonance mode with large electromagnetic eld enhancements. 7,13,17,18 Plasmonic structures with tunable gap distances have been constructed by the integration of metal nanoparticles with some molecules or polymers that provide specic interactions for reversible assembly or possess stimuli-responsive conformational changes. 8,19 They are roughly classied into two approaches.…”