Nanometrology for examining nanomaterials released from products undergoing weathering

Wednesday, April 12, 2017

Presenter

James Ranville

Professor, Department of Chemistry
Colorado School of Mines

Abstract: As the use of nano-enabled products rises, the potential for engineered nanoparticles (ENPs) release to the environment increases. One process involves product exposure to precipitation and sunlight. New nanometrology that quantifies and characterizes (size, composition, physical form) ENPs are needed. A methodology using a combination of single particle ICP-MS (spICP-MS) and field flow fractionation (FFF) was developed to facilitate the investigation of ENP release during weathering. The spICP-MS method provides the inorganic NP size and particle number concentration based on elemental mass.  Two FFF techniques, asymmetric flow field-flow fractionation (AF4) and centrifugal field-flow fractionation (CFFF), separate and size particles based on their hydrodynamic size and buoyant mass, respectively.  Combing these methods leads to insights into the form of the released nanomaterials.
 
The release of single-wall carbon nanotubes (SWCNTs) from a carbon nanotube polymer nanocomposite (CNT-PNCs) provides an example of the need for improved methods for characterizing released ENPs. Figure 1 shows the pulses (generally < 50 counts) in 89Y that each result from the detection of SWCNTs in a suspension. Figure 2 shows the results of an sp-ICP-MS analysis of a suspension generated by 10 days of UV irradiation of a CNT-PNC.  Larger pulses (averaging 100-200 counts) demonstrate that SWCNTs are released as multiples/bundles embedded within photolyzed polymer fragments.  The environmental fate and impact of SWCNTs are likely highly influenced by their form. The talk will highlight the details of combining sp-ICP-MS and FFF to fully characterize ENPs and to address the issue of background nanoparticles, which create a challenge to ENP quantification. Other studies to be reported on include the release of TiO2 from concretes and sunscreens.  Further refinements of the nanometrology will lead to improvements in the life cycle assessment of nanomaterials, particularly in the use and end of life phases.