Deep Eutectic Solvent Assisted Dispersion of Carbon Nanotubes in Water
FRONTIERS IN CHEMISTRY
Authors: Zaib, Qammer; Adeyemi, Idowu; Warsinger, David M.; AlNashef, Inas M.
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 DES-nanomaterial dispersions.
Macrocycle Co-Crystals Showing Vapochromism to Haloalkanes
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
Authors: Li, Bin; Cui, Lei; Li, Chunju
Abstract
Organic co-crystal engineering is a promising method to make multifunctional materials. Here, the marriage of macrocyclic chemistry and co-crystal engineering provides a smart strategy to build vapochromic materials. The macrocycle co-crystals (MCCs) were constructed from pi-electron rich pillar[5]arene (P5) and an electron-deficient pyromellitic diimide derivative (PDI) on a 10 g scale. MCCs of P5-PDI are in red owing to the formation of a charge-transfer (CT) complex. After solvent removal, a white crystalline solid with a new structure (P5-PDI alpha) is yielded, which exhibits selective vapochromic responses to volatile organic compounds (VOCs) of haloalkanes, accompanied by color changes from white to red or orange. Powder and single-crystal X-ray diffraction analyses reveal that the color changes are attributed to the vapor-triggered solid-state structural transformation to form CT co-crystals. Coating films of P5 and PDI on glass showed a visible vapochromic behavior with good reversibility.