Determining the effects of various surface coatings on carbon nanotubes (CNTs) is critical given the numerous expected applications of CNTs and their inevitable release into ecosystems. To explore the potential ecotoxicological effects of CNT surface modifications, we modified multi-walled carbon nanotubes (MWNTs) with polyethyleneimine (PEI) grafting, which endow the nanotubes with enhanced aqueous stability and, after additional chemical modifications, positive, negative, or neutral surface charges. Uptake and elimination experiments for PEI-MWNTs with various surface charges spiked to soils revealed the same limited earthworm accumulation and ready elimination as purified MWNTs. Interestingly, PEI-MWNTs and regular MWNTs revealed significantly different sorption and desorption behaviours in soils, which contrasts with their similar, limited bioaccumulation. Conversely, Daphnia magna, an aquatic organism, accumulated substantial concentrations of PEI MWNTs and was only able to excrete them with algae feeding. This suggests that the availability of food in ecosystems will substantially affect the long-term fate of nanotubes ingested by daphnia. Significant differences were observed among the various types of nanotubes suggesting that surface coatings may strongly influence the potential ecotoxicological effects of carbon nanotubes in the environment.
Journal: TechConnect Briefs
Volume: 3, Nanotechnology 2012: Bio Sensors, Instruments, Medical, Environment and Energy (Volume 3)
Published: June 18, 2012
Pages: 307 - 310
Industry sectors: Advanced Materials & Manufacturing | Energy & Sustainability
Topics: Environmental Health & Safety of Nanomaterials