| Due to the escalating production and the reported toxicity of carbon nanotubes (CNTs), it is important to understand the fate and transport of CNTs, as well as the interaction between CNTs and biological cells, once they are released into the aquatic environment. In this dissertation, the influence of solution chemistry on the deposition and remobilization of multiwalled CNTs (MWNTs) on silica surfaces and model cell membranes were studied using a quartz crystal microbalance with dissipation monitoring (QCM-D).;The deposition kinetics of MWNTs on silica, a ubiquitous surface in the environment, are in qualitative agreement with Derjaguin--Landau--Verwey--Overbeek (DLVO) theory. Highly oxidized MWNTs (HO-MWNTs) are more stable to deposition than lowly oxidized MWNTs (LO-MWNTs) in NaCl since HO-MWNTs are more negatively charged than LO-MWNTs. However, both MWNTs have similar colloidal stability in CaCl2, which is attributed to Ca2+ cations having a higher affinity to form complexes with adjacent carboxyl groups on HO-MWNTs than with isolated carboxyl groups on LO-MWNTs.;The MWNTs that are initially deposited on silica surfaces can be released from the primary energy minimum when eluted with lower electrolyte concentrations if the energy barrier for release becomes sufficiently small. The incomplete release of MWNTs when eluded with low concentrations of CaCl2 is attributed to the heterogeneity of surface charge density of MWNTs. The kinetics of MWNT release are first order with respect to the mass of releasable MWNTs. Both the degree of MWNT release and the release rate coefficient of releasable MWNTs are important parameters for characterizing the release kinetics and both parameters are found to increase with decreasing electrolyte concentrations.;The interactions of MWNTs with supported lipid bilayers (SLBs) as model cell membranes were investigated. At high CaCl2 concentrations or acidic pH, the deposition of MWNTs on SLBs was favorable due to the charge reversal of SLBs and the resultant electrostatic attraction between MWNTs and SLBs. However, the deposition of MWNTs on SLBs is unfavorable even at 1 M NaCl, probably due to the repulsive hydration force. Although the deposition of MWNTs on SLBs is mostly irreversible, no significant damage of phospholipid bilayers was observed upon the attachment of MWNTs. |
