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In this work, we discuss the challenges associated with measuring and interpreting the vibrational properties of nanomaterials at mid- and far-infrared frequencies, where vibrational bands are often broad and overlapping. This issue is compounded by the complex interaction between infrared light and particulate samples, which depends on packing density and particle connectivity. Preliminary results concerning the far-infrared optical properties of Fe3O4 nanoparticles have been obtained using the two most reliable methods (specular reflectance and attenuated total reflectance). These results are compared to one another and to their Raman counterparts. Finally, the influences of particle size and composition on the vibrational spectra are qualitatively discussed.

In recent years, much effort has been invested into developing multifunctional drug delivery systems to overcome the drawbacks of conventional carriers. Magnetic nanoparticles are not generally used as carriers but can be functionalised with several different biomolecules and their size can be tailored to present a hyperthermia response, allowing for the design of multifunctional systems which can be active in therapies. In this work, we have designed a drug carrier nanosystem based on Fe3O4 nanoparticles with large heating power and 4-amino-2-pentylselenoquinazoline as an attached drug that exhibits oxidative properties and high selectivity against a variety of cancer malignant cells. For this propose, two samples composed of homogeneous Fe3O4 nanoparticles (NPs) with different sizes, shapes, and magnetic properties have been synthesised and characterised. The surface modification of the prepared Fe3O4 nanoparticles has been developed using copolymers composed of poly(ethylene-alt-maleic anhydride), dodecylamine, polyethylene glycol and the drug 4-amino-2-pentylselenoquinazoline. The obtained nanosystems were properly characterised. Their in vitro efficacy in colon cancer cells and as magnetic hyperthermia inductors was analysed, thereby leaving the door open for their potential application as multimodal agents. [ABSTRACT FROM AUTHOR]

The interplay between chemical inhomogeneities and magnetic properties in iron alloys is a subtle question that affects several nanoalloys with potential technological and biomedical applications. Herein below, we focus on the FCC palladium rich-iron nanoparticle system, specifically in three samples that reflect the key influence of synthesis conditions. Magnetic measurements as a function of field and temperature have allowed detecting the onset of anomalous relaxation phenomena of the magnetization due to the strong weakening of the exchange coupling in nanoparticles prepared at low temperatures. Such effects are triggered by the lack of a good inter-diffusion of atomic species during core growth and directly affect the magnetic anisotropy. Electron Magnetic Resonance spectroscopy has confirmed that iron clustering leads to a gradual transition from a superparamagnetic state at low temperatures to a nearly paramagnetic behaviour at high temperatures. The measurements of the g-factor and the average magnetic moment per Fe atom do not account for a significant polarization in Pd atoms. [ABSTRACT FROM AUTHOR]

Research has been conducted on nickel, palladium and platinum tetracyanometalates with 2,2'-bipyridine and 1,10-phenanthroline cyclic diquaternary cations. The synthesis and characterization of these compounds have been carried out and the results are reported.

The main objective of the preparation of the Fe3−xGaxO4 (0.14 ≤ x ≤ 1.35) system was to further the knowledge of the magnetic response of Ga3+-doped magnetite for application as MRI contrast agents. With this purpose, monodisperse nanoparticles between 7 and 10 nm with different amounts of gallium were prepared from an optimized protocol based on thermal decomposition of metallo-organic precursors. Thorough characterization of the sample was conducted in order to understand the influence of gallium doping on the structural, morphological and magnetic properties of the Fe3−xGaxO4 system. X-ray diffraction and X-ray absorption near-edge structure measurements have proved the progressive incorporation of Ga in the spinel structure, with different occupations in both tetrahedral and octahedral sites. Magnetization measurements as a function of field temperature have shown a clear dependence of magnetic saturation on the gallium content, reaching an Ms value of 110 Am2 kg−1 at 5 K for x = 0.14 (significantly higher than bulk magnetite) and considerably decreasing for amounts above x = 0.57 of gallium. For this reason, nanoparticles with moderate Ga quantities were water-transferred by coating them with the amphiphilic polymer PMAO to further analyse their biomedical potential. Cytotoxicity assays have demonstrated that Fe3−xGaxO4@PMAO formulations with x ≤ 0.57, which are the ones with better magnetic response, are not toxic for cells. Finally, the effect of gallium doping on relaxivities has been analysed by measuring longitudinal (T1−1) and transverse (T1−1) proton relaxation rates at 1.4 T revealing that nanoparticles with x = 0.14 Ga3+ content present remarkable T2 contrast and the nanoparticles with x = 0.26 have great potential to act as dual T1–T2 contrast agents. [ABSTRACT FROM AUTHOR]

Manganese/iron ferrite nanoparticles with different Mn2+/3+ doping grades have been prepared by a thermal decomposition optimized approach so as to ascertain the doping effect on magnetic properties and, especially, on the magnetic hyperthermia response. The oxidation state and interstitial position of Mn in the spinel structure is found to be critical. The particle size effect has also been studied by growing one of the prepared samples (from 10 to 15 nm in diameter) by a seed mediated growth mechanism. After analyzing the main structural and chemical parameters such as the Mn/Fe rate, crystalline structure, particle diameter, shape and organic coating, some Mn doping induced changes have been observed, such as the insertion of Mn2+ cations yielded more anisotropic shapes. Magnetic characterization, carried out by DC magnetometry (M(H), M(T)) and electron magnetic resonance (EMR) techniques, has shown interesting differences between samples with varying compositions. Lower Mn doping levels lead to larger saturation magnetization values, while an increase of the Mn content causes the decrease of the effective magnetic anisotropy constant at low T. The homogeneous magnetic response under applied magnetic fields, together with the great effect of nanoparticle size and shape in such a response, has been confirmed by the EMR analysis. Finally, a detailed magnetic hyperthermia analysis has demonstrated the large influence of NP size and shape on the magnetic hyperthermia response. The optimized Mn0.13Fe2.87O4_G sample with a diameter of 15 nm and slightly truncated octahedral shape is presented as an interesting candidate for future magnetic hyperthermia mediated biomedical treatments. [ABSTRACT FROM AUTHOR]