Deep Eutectic Solvent Assisted Dispersion of Carbon Nanotubes in Water

Abstract

Deep Eutectic Solvents (DESs) are emerging as a promising medium for many chemical processes. They can be used to observe specific properties required for nanomaterials' applications. Controlled CO 2 adsorption requires disaggregation of carbon nanotubes into smaller bundles which can be accomplished by dispersing them in aqueous DES system. In this study, response surface methodology (RSM) was adopted to examine the impacts of three important factors on the dispersion of single walled carbon nanotubes (SWNTs) in Choline Chloride-Glycerol (ChCl-Gly) DES; (i) ChCl-Gly (mass% in water), (ii) sonication energy input (J/mL), and (iii) SWNTs' concentration (mg/L). The net negative surface charge of ChCl-Gly, a "green solvent," provided superior dispersion of inherently negatively charged SWNTs in water via electrostatic repulsion. The impacts of the dispersion factors were quantified by the average aggregate diameter (nm) and polydispersity (polydispersity index, PDI) of SWNTs in aqueous-DES systems. Models were developed, experimentally verified, and statistically validated to map the impacts of these factors and to obtain optimized dispersions. The optimized dispersions, characterized by the small (<100 nm) and uniform (<0.1 PDI) SWNTs' aggregates, were achieved at lower sonication energy costs which can have promising implications across many nano-manufacturing fields. The dispersion/aggregation mechanism was proposed using COSMO-RS (based on equilibrium thermodynamics and quantum chemistry) modeling of ChCl-Gly and zeta potential measurements of SWNTs. This understanding will help create optimally sustainable and economically feasible DESnanomaterial dispersions.

Characterization of Carbon Nanomaterials Dispersions: Can Metal Decoration of MWCNTs Improve Their Physicochemical Properties?

“…The electrolyte reaction media considered to entrap metallic NPs into the carbon matrix have also captured great attention due to their high impact on the chemical properties, mechanical stability and compatibility with enhanced surface area and electrical properties [ 19 ]. Non-aqueous solvents may present some advantages compared to aqueous solvents [ 19 , 20 , 21 ], when the dispersibility and the electrochemical stability is taken into consideration [ 22 ]. Ionic liquids (ILs) present high production and purification costs, making these dense non-aqueous fluids less competitive when compared with traditional solvents.…”

“…Alternatively, deep eutectic solvents (DES) have emerged as suitable and attractive “green” alternatives to ILs for many chemical processes and are often described as ILs analogues in the literature [ 20 ]. Due to their unique compositional flexibility, intermolecular interactions and physicochemical properties, DES are pointed as a good dispersion media for carbon materials, such as CNTs [ 21 ].…”

“…Following the works by Brandão et al [ 24 ] and Cojocaru et al [ 18 ], the electrochemical decoration of MWCNTs with Ag-NPs from choline chloride–glycerol eutectic mixture, using pulse reversed current in a two-electrode cell can be successfully achieved. Water-glyceline based DES binary systems have been successfully used in assisting and optimizing the dispersion efficiency of carbon nanotubes in water, allowing to predict the fate and transport of SWCNTs in aqueous DES systems [ 21 ].…”

“…Several studies have been carried out regarding the thermophysical properties of several ILs and DES [ 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ], and both have been proved to be good dispersant media for CNTs dispersion [ 21 , 34 , 35 , 36 , 37 , 38 , 39 ].…”

Rethinking the Applications of Ionic Liquids and Deep Eutectic Solvents in Innovative Nano-Sorbents

“…Therefore, they are employed as eco-friendly extractants and sorbents to replace the old ones (Sepulveda et al, 2020). Mainly, ionic liquids (ILs) and deep eutectic solvents (DESs) contribute greatly to separation science besides their use as an extraction medium (Marták and Schlosser, 2019); they can also assist adsorbents to improve separation performance by the disaggregation of nano-materials into smaller bundles (Zaib et al, 2020).…”