Metal fingerprinting and chemothermal isolation methods to quantify natural and engineered carbon nanoparticles

Duke University, Durham NC

Investigators

Abstract

CBET - 1336794 Overview: The PIs seek to develop methodology to quantify, fingerprint, and distinguish natural and engineered carbonaceous nanoparticles using thermal separation techniques and metal content signatures. Building on well-established thermal methods to quantify black carbon (BC) soot, the PIs propose a technique that distinguishes non-nanoparticulate natural organic matter, single-walled carbon nanotubes (SWCNTs), and BC (the most ubiquitous, natural carbonaceous nanoparticle) based on their distinct thermal stabilities. Preliminary results suggest that natural organic matter, SWCNTs, and BC have unique oxidation ranges and could be distinguished and quantified following sequential oxidations coupled with elemental analysis. Here, we aim to demonstrate that these thermal stabilities are preserved in complex mixtures of air, water, sediments, and soil, and as a result, can be used to quantitatively delineate the nanoparticles (e.g., natural vs. engineering) in environmental matrices. Furthermore, bulk metal contents determined via complete acid digestion and mass spectrometry should provide a route toward source apportionment. Advantages of this approach include the low cost, accessibility, high-throughput capabilities, and minimal sample processing (e.g., extraction) required for this method, which reduces the potential for analyte loss and transformation during analysis. Intellectual Merit : The National Research Council 2012 EHS Nanotechnology Research Strategy report listed analytical techniques as the first research priority. Current approaches for measuring carbonaceous nanoparticles (CNPs) in the work place (and atmosphere) primarily rely on light-scattering particle sizers, which provide a bulk measure of nano-sized particles. However, as synthetic approaches to form engineered carbonaceous nanoparticles (i.e, carbon nanotubes and graphene) are known to co-produce natural nanoparticles (i.e., soot), current results are reporting natural plus engineered nanoparticle exposure. Thus, it is not possible to quantitatively determine occupational exposure to engineered nanoparticles. In addition, there are no methods to assess release of engineered nanoparticles to the atmosphere, which is a likely vector for CNP transport to the environment. This has severe consequences for ongoing nanoparticle research: (1) fate models lack validated source data, (2) occupational exposure can be neither assessed nor enforced, and (3) environmental release can not be mitigated where necessary. Upon project completion, quantitatively differentiation of natural and engineered carbonaceous nanoparticles (NPs) will be possible for the first time, allowing accurate assessment of exposure to engineered NPs, which have unique properties, morphologies, and toxicities compared to natural NPs. These goals are within the team?s reach and rely on affordable, accessible technologies. Broader Impacts : The PIs and their research groups are actively involved in the outreach efforts hosted by the Center for the Environmental Implications of Nano-technology (CEINT) at Duke University, as well as other science enrichment activities there, including Females Excelling More in Math Engineering and Science (FEMMES) (100% females from underrepresented groups) volunteer science workshops. As part of the proposed work, the PIs will establish a nano-analytical K-12 education module (Is CSI for real? Rapid Nano-forensics?), and this will be taught as part of NanoDays, FEMMES, and later distributed to the CEINT network of K-12 educators. Additionally, the program will be modified for a more advanced audience (e.g., public library and senior center), delivered live, and videotaped for web distribution.