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 CO2 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 DES-nanomaterial dispersions.
Highlights
Deep Eutectic Solvents (DESs) are mixtures of Brønsted or Lewis acids and bases that are emerging as a new class of solvents due to advantages in safety, simplicity, sustainability, cost, and applications that include synthesis and functionalization of nanomaterials (Abo-Hamad et al, 2015)
Hammond and co-workers observed that the nanostructure of a deep eutectic solvent was maintained in the presence of a remarkably high quantity of water (∼40 wt.%) (Hammond et al, 2017)
The dispersion of single-walled carbon nanotubes (SWNTs) in deep eutectic solvent has been observed through experiments and response surface methodology (RSM) models
Summary
Deep Eutectic Solvents (DESs) are mixtures of Brønsted or Lewis acids and bases that are emerging as a new class of solvents due to advantages in safety, simplicity, sustainability, cost, and applications that include synthesis and functionalization of nanomaterials (Abo-Hamad et al, 2015). (Morrison et al, 2009), biodiesel purification of glycerol (Abbott et al, 2007; Hayyan et al, 2010; Shahbaz et al, 2011; Zhang et al, 2012), organic synthesis (Ilgen and König, 2009), electrodeposition, metal processing (Smith et al, 2014), dyesensitized solar cells, catalysis of polymers and fuel additives, and nanomaterial dispersion, functionalization, and fabrication (Zhang et al, 2012) They are being adopted as a “greener alternative” to conventional solvents because they are generally considered biodegradable, non-toxic, and safe (Smith et al, 2014). Among the DESs, ChCl-Gly could be considered as a “green solvent.”
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