Dispersing single-walled carbon nanotubes using common phospholipids with a small amount of polyethylene glycol-phospholipid additives

Nearly 60% of the single-walled carbon nanotubes (SWCNTs) in a sample were rendered dispersible in water using common double-chain phospholipids, such as phosphatidylcholine, with a small amount of polyethylene glycol (PEG)-derivatized phospholipid. The dispersion isotherms were measured versus the PEG-phospholipid concentration in various host phospholipids. In every case, the isotherms followed a step-shaped curve characterized by the critical dispersion concentration (CDC) and the saturated dispersed amount (SDA). The CDC remains nearly constant (5 μmol/L) and independent of the type and concentration of the host phospholipid. The SDA increases as the alkyl chains of the host phosphatidylcholine decrease in length. The most efficient result is obtained with a glycerol-phospholipid at a 10 nmol/L CDC. The dispersion mechanism does not involve SWCNT encapsulation by the vesicles; instead, dispersion occurs by co-adsorbed phospholipids aggregating on the surface.