Raman spectroscopy to unravel the magnetic properties of iron oxide nanocrystals for bio-related applications

Abstract

Raman spectroscopy is a very valuable and fast-performance tool to gain insight first into the different iron oxide phases present in nanoparticles, to correlate then the magnetic properties with potential bio-related applications.

Raman spectra tell us so much more: Raman features and saturation magnetization for efficient analysis of manganese zinc ferrite nanoparticles

“…The bands are labelled in blue font in Figure a and named according to nomenclature scheme used by Shebanova and Lazor and Thota et al: the A 1g band, the E g band, and three T 2g bands ( g denotes the symmetry with respect to the centre of inversion). It is usual that spinel iron oxides and ferrites have a low scattering efficiency and give rise to wide bands (full width half maximum > 40 cm −1 ) . The spectrum of magnetite, which contains only iron cations and no cation vacancies, features a single contribution for each of the five bands ( R 2 = .995), whereas spinel ferrites with additional order/disorder features contained multiple contributions within the five main bands.…”

“…Despite the abundance of studies and reviews comparing Raman spectra of different spinel‐type iron oxides and ferrites containing various metal dopants, there is no in‐depth knowledge of the relationship of Raman spectra with physical and chemical properties of NPs. Another uncertainty is the origin of Raman bands: certain experimental results suggest that bands in the 600–750 cm −1 spectral region arise from tetrahedral (A‐site) systems and those in the 100–600 cm −1 region from octahedral (B‐site) systems, whereas the other line of experimental and theoretical considerations lead to the conclusion that all active Raman bands arise from A‐sites …”

Recent Advances in Nano‐ and Micromotors

“…Accordingly, magnetic nano/micromotors exposed to such a magnetic field gradient will have their magnetic moments aligned in the same direction, such that dipolar interactions will emerge between them, creating groups of nano/micromotors, and thus forming aggregates or chains . The velocity reached by the nano/micromotors once propelled is determined by the so‐called magneto‐phoretic mobility, which depends on both the characteristics of the nano/micromotors (size and magnetic properties) and the medium (viscosity) . The magnetophoretic mobility determines therefore the efficiency of the magnetic manipulation, which can be additionally tuned by modulating the magnetic field …”

Partial FeO–Fe3O4 Phase Transition Along the <111> Direction of the Cubic Crystalline Structure in Iron Oxide Nanocrystals

“…Iron oxide‐based multicomponent nanocrystals offer a huge platform of magnetic properties, stemming from values of coercivity, saturation magnetization, magnetic susceptibility, and/or exchange bias, of which the multiple possible combinations help expanding their nanomagnetism and applications, for instance in the biomedical field . In this regard, a fundamental motivation for studying these nanocrystals relates to controlling their effective magnetic anisotropy, on which size, shape, and interfaces between different magnetic orders, because of the multicomponent situation, have a huge impact .…”

“…In this regard, a fundamental motivation for studying these nanocrystals relates to controlling their effective magnetic anisotropy, on which size, shape, and interfaces between different magnetic orders, because of the multicomponent situation, have a huge impact . Furthermore, we should emphasize the important role the surface energy exerts in iron oxide nanoscale materials, in order to stabilize and favor the formation of crystalline phases which can be thermodynamically unstable in bulk, but that can be key in adjusting the final magnetic behavior, and ultimately, at delineating the appropriate applications …”