Entrapping of Fullerenes, Nanotubes, and Inorganic Nanoparticles by a DNA–Chitosan Complex: A Method for Nanomaterials Removal

Abstract

We report a protocol for entrapping of various water-dispersed nanomaterials: fullerenes, multiwall carbon nanotubes, quantum dots (semiconductor nanoparticles), and gold nanorods, into a DNA-chitosan complex. In contrast to small-size nanomaterial particles, the bulky DNA-chitosan interpolyelectrolyte complex incorporating the dispersed nanomaterials can be easily separated from aqueous media by centrifugation, filtration, or decantation. While the removal of nanoparticles by centrifugation is equally efficient for every type of nanoparticles and reaches 100%, the higher efficiency of the nanomaterials removal by other two methods is favored by larger size of nanoparticles. The application of this entrapping protocol for removal of nanomaterials from water is discussed.

Separation of Nano‐scaled Particles by Flocculation

“…Electrostatic‐induced flocculation perhaps is the most widespread application of the flocculation mechanism. The working principle is rather straightforward, which involves the flocculation of particles by an oppositely charged polymer flocculant, e.g., flocculation of anionic particles by cationic polymers 22, 25–27 and vice versa 28. Here, the strong electrostatic attraction serves as the primary driving force for the particle‐polymer interaction 22, 28.…”

“…The idea of implementing a dual‐polymer approach is to increase the flocculation efficiency and universality. A work published by Zinchenko et al 25 illustrated the advantage of using dual polymers as compared to single polymer in the separation of nanoparticles. The dual polymers employed in their work were chitosan and DNA while the to‐be‐separated nanoparticles were different cationic (e.g., multiwall carbon nanotubes (MWCNTs), gold nanorods) and anionic (e.g., Qdot, hydroxyfullerenes) nanoparticles.…”

“…Flocculation of anionic nanoparticles by DNA‐chitosan complex. Reprinted with permission from 25. Copyright 2013, American Chemical Society.…”

Entrapment and Removal of Carbon Nanotubes and Fullerenes by Coprecipitation with Calcium Carbonate Beads

“…The entrapment efficiency of the fullerenes is noteworthy because it is advantageous in comparison to the earlier proposed method of nanomaterials removal by a pair of polyelectrolytes, which was not efficient for the entrapping of fullerene without ultracentrifugation. 20 To address the effect of the surface groups of nanomaterials, the uptake efficiency of carbon nanotubes with carboxylic surface groups (MWCNT-COOH) was studied under the same conditions as MWCNT-OH ( Figure 5E). The uptake of MWCNT-COOH by CaCO 3 beads was very similar to that of MWCNT-OH, indicating that the proposed method works equally well in spite of the different nature of functional groups on the nanotube surface.…”

“…Recently, we proposed a method for entrapment of various ENM using a pair of oppositely charged polyelectrolytes that assemble into a three-component water-insoluble precipitate. 20 However, the method had a number of practical limitations, such as poor performance toward small (<10 nm) ENM (quantum dots, fullerenes) and relatively high cost.…”