title: Surfactive stabilization of multi-walled carbon nanotube dispersions with dissolved humic substances.
abstract: Soil humic substances (HS) stabilize carbon nanotube (CNT) dispersions, a mechanism we hypothesized arose from the surfactive nature of HS. Experiments dispersing multi-walled CNT in solutions of dissolved Aldrich humic acid (HA) or water-extractable Catlin soil HS demonstrated enhanced stability at 150 and 300 mg L(-1) added Aldrich HA and Catlin HS, respectively, corresponding with decreased CNT mean particle diameter (MPD) and polydispersivity (PD) of 250 nm and 0.3 for Aldrich HA and 450 nm and 0.35 for Catlin HS. Analogous trends in MPD and PD were observed with addition of the surfactants Brij 35, Triton X-405, and SDS, corresponding to surfactant sorption maximum. NEXAFS characterization showed that Aldrich HA contained highly surfactive domains while Catlin soil possessed a mostly carbohydrate-based structure. This work demonstrates that the chemical structure of humic materials in natural waters is directly linked to their surfactive ability to disperse CNT released into the environment.
authors.affiliation: Environmental Laboratory, Engineering Research & Development Center, US Army Corps of Engineers, Vicksburg, MS 39180, USA. mark.a.chappell@usace.army.mil
authors.forename: Mark A
authors.initials: MA
authors.lastname: Chappell
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: George
authors.forename: Katerina M
authors.initials: KM
authors.lastname: Dontsova
authors.forename: Beth E
authors.initials: BE
authors.lastname: Porter
authors.forename: Cynthia L
authors.initials: CL
authors.lastname: Price
authors.forename: Pingheng
authors.initials: P
authors.lastname: Zhou
authors.forename: Eizi
authors.initials: E
authors.lastname: Morikawa
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Kennedy
authors.forename: Jeffery A
authors.initials: JA
authors.lastname: Steevens
mesh_terms: D000327:Adsorption; D004784:Environmental Monitoring / Q000295:instrumentation / Q000379:methods; D006812:Humic Substances; D008422:Materials Testing; D037742:Nanotubes, Carbon / Q000737:chemistry*; D010316:Particle Size; D013499:Surface Properties; D013501:Surface-Active Agents / Q000494:pharmacology; D014874:Water Pollutants, Chemical / Q000032:analysis
chemical_list: D006812:Humic Substances; D037742:Nanotubes, Carbon; D013501:Surface-Active Agents; D014874:Water Pollutants, Chemical