title: Change in Chirality of Semiconducting Single-Walled Carbon Nanotubes Can Overcome Anionic Surfactant Stabilization: A Systematic Study of Aggregation Kinetics.
abstract: Single-walled carbon nanotubes' (SWNT) effectiveness in applications is enhanced by debundling or stabilization. Anionic surfactants are known to effectively stabilize SWNTs. However, the role of specific chirality on surfactant-stabilized SWNT aggregation has not been studied to date. The aggregation behavior of chirally enriched (6,5) and (7,6) semiconducting SWNTs, functionalized with three anionic surfactants-sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS), and sodium deoxycholate (SDOCO)-was evaluated with time-resolved dynamic light scattering. A wide range of mono- (NaCl) and di-valent (CaCl2) electrolytes as well as a 2.5 mg TOC/L Suwannee River humic acid (SRHA) were used as background chemistry. Overall, SDBS showed the most effectiveness in SWNT stability, followed by SDOCO and SDS. However, the relatively larger diameter (7,6) chiral tubes compromised the surfactant stability, compared to (6,5) chiral enrichment, due to enhanced van der Waals interaction. The presence of di-valent electrolytes overshadowed the chirality effects and resulted in similar aggregation behavior for both the SWNT samples. Molecular modeling results enumerated key differences in surfactant conformation on SWNT surfaces and identified interaction energy changes between the two chiralities to delineate aggregation mechanisms. The stability of SWNTs increased in the presence of SRHA under 10 mM monovalent and mixed electrolyte conditions. The results suggest that change in chirality can overcome surfactant stabilization of semiconducting SWNTs. SWNT stability can also be strongly influenced by the anionic surfactant structure.
authors: Department of Chemical Engineering, University of Rhode Island, Kingston, RI 02881, USA.
authors: Iftheker A
authors: IA
authors: Khan
authors: Department of Civil and Environmental Engineering, University of South Carolina, Columbia, SC 29208, USA.
authors: Joseph R V
authors: JR
authors: Flora
authors: Department of Civil, Architectural, and Environmental Engineering, University of Texas, Austin, TX 78712, USA.
authors: A R M
authors: AR
authors: Nabiul Afrooz
authors: Department of Civil, Architectural, and Environmental Engineering, University of Texas, Austin, TX 78712, USA.
authors: Nirupam
authors: N
authors: Aich
authors: Department of Civil, Architectural, and Environmental Engineering, University of Texas, Austin, TX 78712, USA.
authors: P Ariette
authors: PA
authors: Schierz
authors: Department of Civil and Environmental Engineering, Duke University, Durham, NC 27708, USA.
authors: P Lee
authors: PL
authors: Ferguson
authors: Department of Environmental and Global Health, University of Florida, Gainesville, FL 32610, USA.
authors: Tara
authors: T
authors: Sabo-Attwood
authors: Department of Civil, Architectural, and Environmental Engineering, University of Texas, Austin, TX 78712, USA.
authors: Navid B
authors: NB
authors: Saleh
keywords: Chirality; aggregation kinetics; anionic surfactants; molecular dynamic simulation; single-walled carbon nanotube; stability