A Review of Analytical Techniques to Characterise Nanomaterial Associations with Minerals, Organic Matter and Organisms

Abstract

Nanomaterials (NMs) have unique properties and control processes relevant to the fate of contaminants in soils, air, and aquatic systems and within the carbon cycle. Many NMs often occur in association with larger mineral grains, organic matter, or living organisms such as microbes, plants and fungi. The preservation of the spatial, textural, chemical, and mineralogical relations between NMs and minerals, organic matter, and organism (NM-associations) is of fundamental importance as it provides information about the origin and formation mechanisms of NMs. Here we review analytical approaches and techniques to study NM-associations at the bulk-, micro-, nano- and atomic-scale. We will focus on (a) X-ray diffraction and mass-spectroscopy techniques; (2) automatisms within software packages that permit the search of features without operators; (3) preparation and analytical techniques such as the focused-ion beam technology, transmission electron microscopy and atom probe tomography; (4) nano-spectroscopic techniques such as tip-enhanced Raman spectroscopy, synchrotron infrared nanospectroscopy, and nano-X-ray fluorescence spectroscopy; (5) ptychographic X-ray computer tomography. This review paper concludes with selected new perspectives such as (a) the characterisation of NM-precursors, (b) the role of NM-associations in the stabilisation of soil organic matter and (c) the interaction of NM-associations in wildfire smoke with contaminants from other sources.