Paula Montoya

Influence of Surface Treatment on Magnetic Properties of Fe3O4 Nanoparticles Synthesized by Electrochemical Method

The changes of magnetic properties in magnetite nanoparticles during two different stabilization processes were investigated. Magnetic nanoparticles (MNPs) were obtained by electrochemical synthesis from two kinds of salts: (CH3)4NCl and NaCl. After that, two methods-steric and electrostatic-were used to stabilize MNPs with oleic acid (OA) and sodium hydroxide (NaOH), respectively. As a consequence, aqueous and organic dispersions were obtained after surface modification. The coated nanoparticles were characterized by TEM, zeta potential, thermogravimetry analysis (TGA), cyclic voltammetry (CV), magnetization measurements, and infrared and Mössbauer spectroscopy. The results showed that the particles were between 8 and 13 nm in size. In addition, the MNPs were coated with negative charge layers from NaOH by physisorption and coated with carboxylate groups from OA by the chemisorption process, and hence, they exhibited different reactivity and behavior depending on the nature of the electrolyte used in the electrochemical synthesis. Furthermore, the uncoated and coated MNPs had a narrow size distribution. Additionally, the saturation magnetization values showed dependence on the magnetite synthesis conditions and surface modifiers.

Electrodeposition of Polypyrrole Films: Influence of Fe3O4 Nanoparticles and Platinum Co-Deposition

Inorganic particles/conductive polymers composites in bulk or films have been subject of intense study during the last decade. This type of materials offer the potential to being used in batteries, electro-chemical display devices, molecular electronics, electromagnetic shields, opto-electronic applications, microwave-absorbing materials, and even for corrosion protection (Garcia et al., 2002; McNally et al., 2005). Conducting polymers have some specific problems that make difficult its use in the above applications. Instability under oxygen and UV exposure, easily doping and over-oxidation are the most common among others. A novel strategy have been reported to improve its properties and extend the application range of these materials, this is the incorporation of inorganic particles of metallic oxides such as MnO2, V2O5, TiO2, Fe2O3, Fe3O4 and WO3 or metallic particles of Zn, Cu, Au, Pt into the conductive polymer (Demets et al., 2000; Ferreira et al., 2001; Kawai et al., 1990; Kuwabata et al., 2000; Lenz et al., 2003; Montoya et al., 2010; Vishnuvardhan et al., 2006). For example we have recently demonstrated that the incorporation of magnetite into polypyrrole (PPy) decreases the electric resistance of the polymeric film and not only stabilize the polaronic form of the polypyrrole, but also preserve the polymer from further oxidation (Montoya et al., 2010). Polypyrrole (PPy) exhibits interesting properties such as high conductivity, relatively good environmental stability, and wide technological applications. PPy can be obtained either by chemical and electrochemical polymerization. The electropolymerization is considered a controlled synthesis method that provides better control of thickness and morphology of films (by controlling parameters as current, voltage, and time), efficient (high materialtransfer efficiency with nearly 100% material utilization and recovery), and environmentally safe (usually a water-based process). The aim of this chapter is to show in detail, two particular cases concerning the development of PPy/inorganic particles composite coatings deposited on stainless steel. First of all, a brief introduction is presented discussing the electrochemical polymerization methods. Then, as a first case, the effect of magnetite (Fe3O4) nanoparticles on the polymer matrix is presented. The second case is the co-deposition of platinum/PPy. Both studies show the effect of the addition of the inorganic phase on the

Assessment of the moisturizing properties of a magnetic mask containing iron oxide particles

Moisturizer is an important component of many cosmetic products. It helps to maintain the skins integrity and its barrier functions. Recently, magnetic masks that seek to improve the properties of the skin have been developed and have become a new cosmetic trend. However, scientific proof of their stated properties is lacking.