Colloidal Suprastructures Self-Organized from Oppositely Charged All-Inorganic Nanoparticles

Abstract

The self-organization of colloidal nanoparticles into programmed suprastructures is an important research area in various disciplines of nano, colloid, and polymer sciences. However, despite the recent advances in their fundamental understanding and practical applications, the selforganization of organic-free inorganic nanoparticles remains unexplored. Herein, we present the controlled organization of oppositely charged allinorganic nanoparticles through the electrostatic interaction and the colloidal behaviors of organized suprastructures. Depending on the charge states of the assembled suprastructures, three different phases, including patchy, patchy bridged, and fully coated particles, are identified, enabling the construction of the phase diagram with nanoparticle concentrations. Especially, the fully coated particles exhibit unexpected colloidal stability through the action of nanoparticles as surface stabilizers to induce the overcharged surface state; thus, we propose the concept of "nanoligands". It is demonstrated that this concept can be extended to a wide range of material combinations, including semiconducting, metallic, and oxide nanoparticles. The currently developed approach will enable the chemical designing of self-organized nanostructures.

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“…Assuming homogeneous doping, for the 1.5% doped PbTe, the surface density of the dopant exposed to the surface is 7.19 × 10 16 atom m –2 , resulting in a calculated surface charge density of 1.15 × 10 –2 C m –2 , similar to those of other stable colloidal particles, such as polystyrene–latex (PSL), [ 24 ] graphene oxide (GO), reduced GO (rGO), [ 25 ] and nanoparticles. [ 26 ] Several studies have reported similar phenomena for doped particles, for example, Sahu et al. reported that electronic doping of TiO 2 nanoparticles with Cu 2+ caused an increase in the ζ‐potential owing to the charge imbalance between Ti 4+ and Cu 2+ and became stable electrostatically in dispersion.…”

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“…LBL assembly results in the formation of multilayer structures whose thicknesses are proportional to the operational number of polycation/polyanion bilayers. 52,138,228 In an example, SbS 4…”

“…Different from the EPD method that relies on external electric field, layer-by-layer (LBL) assembly takes advantage of electrostatic forces by alternating adsorption of positively and negatively charged species from their corresponding solutions. LBL assembly results in the formation of multilayer structures whose thicknesses are proportional to the operational number of polycation/polyanion bilayers. ,, In an example, SbS 4 3– -capped CdSe NCs were assembled into NC multilayer films by sequentially depositing CdSe NCs and Cd 2+ from their solutions (Figure c) . In this case, the capped SbS 4 3– ligands exhibited a strong interaction with Cd 2+ and such intermolecular electrostatic forces acted as the driving forces for the assembly of adjacent NC layers.…”