Controlling the Growth of Charged‐Nanoparticle Chains through Interparticle Electrostatic Repulsion

Abstract

Nanoparticles (NPs) are envisaged as both building blocks to form advanced materials [1][2][3] and appropriate models to gain insight into condensed-matter physics; [4][5][6][7] this is because of their unique dimensions and the innovative physical properties derived thereof. All these promising applications of the NPs are primarily dependent on the capability of controlling their spatial coupling. Self-assembly of NPs is driven by various forces, such as van der Waals interactions, which lead to either dense and close-packed clusters or extended crystals.[8] The assembled structures are a result of a thermodynamic balance between these interactions. By capping the NPs with molecular ligands to minimize the van der Waals attractions and induce dipolar interactions, it was recently possible to tune the anisotropic interactions that dominate the course of the self-assembly process, thus leading to anisotropic self-assembly of the NPs into one-dimensional (1D) chains, [9][10][11] two-dimensional (2D) freestanding films, [12] or quasi-2D fractal chain networks.[13] However, the control of the anisotropic self-assembly of NPs (for example, the chain length) has been scarcely studied, which makes the thermodynamic picture revealed in the self-assembly studies hard to extend to other self-assembled systems, such as crystallization or phase transition-this is particularly true in the case of aqueous media where the electrostatic interactions are not at all negligible.Electrostatic interactions are long-range interactions which ubiquitously exit in aqueous systems. Electrostatic repulsive and attractive interactions between charged particles are usually regarded as isotropic, thus driving the selfassembly of the particles in an isotropic crystallization fashion. Recently, Lilly et al. successfully regulated the electrostatic interactions between aqueous CdTe NPs by using dimethyl sulfoxide, thus controlling the transformation of the NPs into nanowires. [14] This result suggests an interesting but usually ignored effect of the electrostatic interactions on the anisotropic self-assembly of charged NPs in aqueous media. Here, we demonstrate the profound anisotropic character of electrostatic repulsions during the self-assembly of charged NPs in the presence of a short-range anisotropic dipolar interaction, thus endorsing the anisotropic selfassembly of charged NPs into chains. Of particular importance is the fact that tuning the electrostatic repulsion between gold NPs by using the ionic strength, and especially the polarity, of the colloidal suspensions led to a fine control of the length of the gold-NP chains, that is, the number of NPs in them.We chose negatively charged gold NPs (with a size of 14 nm and stabilized by citrate) as the model system because the transverse configuration of their plasmon resonance is highly sensitive to the electronic coupling between particles, [15] thus enabling us to monitor the particle-chain growth in situ by using spectroscopic methods. The colloidal stability of charged particles in an...

F–Bi4TaO8Cl flower-like hierarchical structures: controlled preparation, formation mechanism and visible photocatalytic hydrogen production

“…It has been widely investigated that self-assembly is controlled by attractive forces such as van der Waals force, hydrogen bonding and repulsive forces such as steric repulsion and electrostatic repulsion. [40][41][42] When the reaction was performed for 1 h, the resulting products are self-assembled underdeveloped aggregated nanoplates with an average diameter of 1 mm, as shown in Fig. 4a, while the inset displays the high magnication FESEM image of a single nanoplate.…”

Dedoped Fe3O4/PPy nanocomposite with high anti-interfering ability for effective separation of Ag(I) from mixed metal-ion solution

“…For the magnetic nanocomposite to be used as [20]. The worm-like morphology of the nanocomposite is due to the arrangement of magnetic component driven by electrostatic repulsion, van der Waals attraction, dipolar interaction, and charge-dipolar interaction [39,40], according to the Derjaguin-La ndau-Verwey-Overbeek (DLVO) theory [39]. Table 1.…”

Molecular Mimetic Self‐Assembly of Colloidal Particles

“…12B). [156,157] The role of electrostatic repulsion highlighted in Wang's work is twofold: firstly, although being isotropic, the electrostatic repulsion favors anisotropic rather than isotropic self-assembly of charged particles; secondly, it defines the sizes of the particle assemblies. Wang et al have also observed the rearrangement of the electric double layer of the charged nanoparticles to new uniform layer surrounding the whole nanoparticle chains.…”

“…Wang et al have also observed the rearrangement of the electric double layer of the charged nanoparticles to new uniform layer surrounding the whole nanoparticle chains. [156] Förster and co-workers have succeeded in directing self-assembly of CdSe/CdS core-shell nanoparticles, coated with a homogenous corona of hydrophilic polyethylene oxide brushes, into chains, branched network, and hollow spheres (colloidosomes) by simply lowering the grafting density of the polymer chains on the particles (Fig. 12C).…”

“…The corresponding high magnification TEM images are shown in the insets. Reproduced with permission from Reference [156], copyright 2008 Wiley-VCH. C) Local arrangement of nanoparticles within string-like aggregates.…”