General Methodology of Using Oil-in-Water and Water-in-Oil Emulsions for Coiling Nanofilaments

Abstract

Hydrophobic carbon nanotubes (CNTs) and hydrophilic nanofilaments such as oxidized CNTs, Pd nanowires (NWs), and MnO(2) NWs are transformed from wires to rings by a general methodology. We show that both oil-in-water and water-in-oil emulsions, so long as their droplet size is sufficiently small, can exert significant force to the entrapped nanostructures, causing their deformation. This effect can be easily achieved by simply mixing a few solutions in correct ratios. Even preformed oil droplets can take in CNTs from the aqueous solution converting them into rings, indicating the important role of thermodynamics: The question here is not if the droplets can exert sufficient force to bend the nanofilaments, because their random vibration may be already doing it. As long as the difference in solvation energy is large enough for a nanofilament, it would "want" to move away from the bulk solution and fit inside tiny droplets, even at the cost of induced strain energy. That said, the specific interactions between a droplet and a filament are also of importance. For example, when an oil droplet rapidly shrinks in size, it can compress the entrapped CNTs in multiple stages into structures with higher curvatures (thus higher strain) than that of a circular ring, which has minimal induced strain inside a spherical droplet.

Gold Nanoparticle Coated Carbon Nanotube Ring with Enhanced Raman Scattering and Photothermal Conversion Property for Theranostic Applications

“…Here we introduce a modified oil-in-water double emulsion method to prepare a CNTR with high yield (Figure 1 and Figure S1). 30 Briefly, the hydrophobic single-walled CNT (0.5–2 μ m) (Figure S1) was first dispersed in dimethylformamide (DMF) containing 1% toluene by volume, followed by the addition of water, forming the toluene droplet containing CNTs. With the diffusion of DMF into water, the volume of the DMF/toluene droplet was continuously decreased, inducing the coiling of CNTs.…”

Synthesis of Micronsized Gold Nanoplates at Low Precursor Concentration Using Ionic Liquid as Novel Subphase Solvent

“…Dichloromethane was removed by using a rotary evaporator under reduced pressure, leaving a white waxy solid. The product was further purified by recrystallization from ethyl acetate at least four times and dried under vacuum for 24 h. The purity of the product was ascertained by an 1HNMR spectrum in CDCl 3 . EAN was synthesized as described by Zhao et al [16].…”

The Sub‐Nanometer Scale as a New Focus in Nanoscience

“…Later, they applied this strategy to induce the coiling of carbon nanotubes, and the positive results support the idea that weak interactions at the sub‐nanometer scale can dominate the interactions between wires with small diameters. In addition to polymer encapsulations, oil‐in‐water or water‐in‐oil emulsions with proper ratios of solvents were also able to induce the coiling of hydrophobic or hydrophilic nanowires through a Pickering emulsion . Tuning the strength of ligand–solvent interactions is vital to the behavior of wires.…”