Tailored synthesis of hydrogel media for chirality separation of single walled carbon nanotubes

Abstract

An alternative approach toward understanding and advancing hydrogel-based single walled carbon nanotube (SWNT) purification is described and employed. Experimental and atomistic modeling analysis of the leading hydrogel for SWNT purification, Sephacryl S200, affords creation of gels that mimic its behavior in terms of dependent SWNT interaction and SWNT purification properties. This achievement introduces a generalized approach toward optimization of SWNT purification media with respect to the components of Sephacryl. Here, the role of the radical initiator ammonium persulfate (APS) in hydrogel-based SWNT purification is explored through synthesis and characterization of gels containing varied APS concentration, and thus, varied amounts of covalently embedded charged organosulfate groups (R–SO4-). The presence of these moieties plays a significant role in SWNT-gel interactions: at decreasing APS concentration SWNT uptake is increased, the chiral profiles of purified SWNT are altered, and a greater fraction of adsorbed material is recovered. Tailored hydrogels containing minimal APS exhibit improved SWNT adsorption vs. Sephacryl. These findings warrant proposition of a four-step qualitative model that deconvolutes electrostatic and steric effects within SWNT/surfactant/hydrogel systems. Collectively, this work demonstrates enhanced methodology for hydrogel-based SWNT purification and lays the foundation for further optimization of the gel medium.