Intertechnique comparisons for nanoparticle size measurements and shape distribution

Abstract

There are a number of techniques for measuring and characterization of nanoparticle (NP) size. One of the main problems in the field of NP analysis is in producing reliable and reproducible characterization data for nanomaterials (NMs). There is no one technique or method that is best suited for every situation, therefore the chosen methodologies improve results from a given sample matrix to produce the needed information in the shortest time and most cost-efficient way. A straightforward monitoring method may simply detect the presence of NMs; others may quantify the size distribution, surface area, or the number of the NPs. The interest in the development of wastewater treatment procedures is growing, therefore several clean-up technologies are being proposed in wastewater treatment that apply NMs as nanosorbents and photocatalysts. This review briefly introduces and compares the fundamental principles of routinely used NP size distribution measurements using both single particle (electron and scanning probe microscopy) and particle population methods, such as dynamic light scattering (DLS), nanoparticle tracking analysis (NTA), and small angle X-ray scattering (SAXS) and outlines the latest applications of NMs, such as nano Ag, TiO2, ZnO, and iron oxide in wastewater treatment and gaps hindering their large-scale use. The outlook for potential applications as well as further challenges is discussed. Currently, DLS is not suitable for analysis of manufactured silver nanoparticles (AgNPs) in environmental samples, whereas the faster and easier to start with is NTA for TiO2 and ZnO nanomaterials in liquid matrices. Finally, an intercomparison of results between methods shows how different measurements are interpreted to give consistent results.