For example, in a multilayer film, XMCD is used to detect the electronic state and magnetic moment of the ferromagnetic layers and buried interfaces underneath the surface protective and electrode layers. In addition, X-rays have a penetrating power that is much greater than that of electrons, so that bulk-sensitive measurements are feasible. This is one of the major advantages over electron beam-based techniques. XAS and XMCD are photon-based probe techniques, which are suitable for measurements under external fields such as strong magnetic and electric fields. The principle and applications of XMCD are reviewed in the next subchapter. This technique, called XMCD, is widely used to study the microscopic mechanism of magnetism. In addition, information about the magnetism can be obtained by using circularly polarized XAS measurements. This technique is based on the optical transition from the atomic core level to the unoccupied states in the valence band, and thus provides element-specific information on the electronic structure and chemical states. XAS using SR is a powerful technique to study the electronic and chemical states of materials. Vaz, in Nanomagnetic Materials, 2021 4.3.1 Introduction The necessity to use separate matrix modifiers for different samples to prevent chemical interference further limits the applicability of GF-AAS.Ĭarlos A.F. Additionally, the duplicate runs required in GF-AAS take longer analysis time. To analyze multiple elements is time-consuming, therefore AAS measurement is typically limited to analysis of single element at a time. The GF-AAS is sensitive and requires small sample volumes (μL), but is suitable for single element analysis in one run. The chances of contamination are higher for solid samples because they require more sample preparation steps. Particularly, the nonaqueous samples have to be largely diluted to maintain the appropriate viscosity for the flame-AAS nebulizer. The sample digestion steps and the relatively high sample volume (2–5 mL) required for flame-AAS analysis adversely affect the detection limits for NM samples. The NMs are not assessed in their original form, rather the metal content within the NM is measured, limiting true representation. However, a significant limitation of these AAS studies in measuring NM mass concentration is the use of digested metallic form of the sample. 34 Compared to GF-AAS, a flame-AAS is more commonly used, with poorer limits of detection. The GF-AAS was used to determine Ag NM-based metal signals from dissolved Ag in complex biological samples (fish) based on a higher thermal energy requirement for atomizing Ag NMs compared to Ag ions. cloud point extraction or flow field flow fractionation) and selective additives are required to distinguish NM-based metal signals from dissolved ions in these measurements. In all cases, prior separation processes (e.g. 33 Particularly, the electrothermal/graphite furnace (GF)-AAS could detect metal signal from Au NMs as low as 0.005 μg L −1 with a NOM tolerance of up to 10 4 μg L −1. Recently, it has been widely used to measure cellular uptake of Au and Ag NMs at trace levels. AAS is well-known for the reliability in detecting a broad range of metal concentrations. 32 Quantitative measurements in AAS are based on Beer's law (the concentration is proportional to absorbance, C = KA). Lead, in Frontiers of Nanoscience, 2015 3.1 Atomic Absorption SpectroscopyĪAS provides a robust analytical route to assess mass concentrations, potentially in the presence of NOM or heavy surfactant coverage.

Absorbance spectra