Molecular composition of iron oxide nanoparticles, precursors for magnetic drug targeting, as characterized by confocal Raman microspectroscopy

Abstract

The chemical and structural properties of ferrite-based nanoparticles, precursors for magnetic drug targeting, have been studied by Raman confocal multispectral imaging. The nanoparticles were synthesised as aqueous magnetic fluids by co-precipitation of ferrous and ferric salts. Dehydrated particles corresponding to co-precipitation (CP) and oxidation (OX) steps of the magnetic fluid preparation have been compared in order to establish oxidation-related Raman features. These are discussed in correlation with the spectra of bulk iron oxides (magnetite, maghemite and hematite) recorded under the same experimental conditions. Considering a risk of laser-induced conversion of magnetite into hematite, this reaction was studied as a function of laser power and exposure to oxygen. Under hematite-free conditions, the Raman data indicated that nanoparticles consisted of magnetite and maghemite, and no oxyhydroxide species were detected. The relative maghemite/magnetite spectral contributions were quantified via fitting of their characteristic bands with Lorentzian profiles. Another quality parameter, contamination of the samples with carbon-related species, was assessed via a broad Raman band at 1580 cm(-1). The optimised Raman parameters permitted assessment of the homogeneity and stability of the solid phase of prepared magnetic fluids using chemical imaging by Raman multispectral mapping. These data were statistically averaged over each image and over six independently prepared lots of each of the CP and OX nanoparticles. The reproducibility of oxidation rates of the particles was satisfactory: the maghemite spectral fraction varied from 27.8 +/- 3.6% for the CP to 43.5 +/- 5.6% for the OX samples. These values were used to speculate about the layered structure of isolated particles. Our data were in agreement with a model with maghemite core and magnetite nucleus. The overall oxidation state of the particles remained nearly unchanged for at least one month.

Synthesis of Carbon Nanomaterials from Rice Husk via Microwave Oven

“…Although radial breathing modes (RBM) are the peaks found at the lower wavenumber between 120 cm −1 and 350 cm −1 which depend directly on the nanotubes diameter indicating the presence of SWCNTs the presence of catalyst particles should not be neglected. On one hand these peaks do not appear in MWCNTs which suggest the presence of SWCNTs; on the other hand these peaks positions are similar to the peaks observed and reported previously as hematite and magnetite [21,22]. The presence of these peaks suggests the reaction of ferrocene under microwave condition to form various arrangement of iron oxide.…”

Raman spectroscopy investigation of magnetite nanoparticles in ferrofluids

“…At 0.90 mW in both samples, a single broad structure at around 670 cm À 1 emerges. Although this band position matches exactly that of magnetite's strongest peak, it should be dealt with caution and analyzed together with other spectral regions [8]. The absence of other spectral features in the spectra, including the low intensity peaks of magnetite, we ascribe to the low concentration and the small size (below 10 nm, data in [20]) of the magnetic particles in the ferrofluids and to the low laser power.…”

“…For correct assignment of the band positions present in our samples and for phase identification, we used combined Raman data for key iron oxides bands [8,9,11,22], from where: The surfactant assisted A-MFs showed very good colloidal stability. The TMAOH concentration in these fluids is not sufficient for detection and will not be discussed.…”

“…Raman spectroscopy allows characterization of many types of samples without any specific preparation [8], which encouraged our experiments with liquids. In this paper, we focus on Raman micro-spectroscopy investigation of magnetite nanoparticles dispersed in two types of ferrofluids.…”

Síntesis de nanopartículas magnéticas de óxido de hierro para la remoción de arsénico del agua de consumo humano

“…La naturaleza de la sustancia fue confirmada utilizando espectroscopia de Raman, la muestra de referencia óxido de hierro (hematita) (figura 3,b) muestra señales fuertes a 226, 292 y 409 cm -1 , la relación de intensidad entre las señales 226/292 cm -1 en la hematita indican alguna heterogeneidad y cristalinidad a micro-escala (Chourpa et al, 2005); mientras tanto la muestra de magnetita presenta picos no resueltos a 671 y 712 cm -1 (figura 3,a) ausentes en la muestra de hematita y que coinciden con la señal de la magnetita pura (de Faria, Silva, & de Oliveira, 1997) (Shebanova & Lazor, 2003).…”