Synthetic iron oxides nanoparticles for biotechnological applications: a multimethod characterization

With the rapid development of nanotechnology, magnetic nanoparticles are currently being widely studied. It has long been known that the physico-chemical properties of magnetic nanoparticles can be vastly different from those of the corresponding bulk material. We present the development of iron oxide nanoparticles, synthesized by a novel and original procedure in nanometer size range. The nanoparticles are now currently produced in a very simple way, by developing a modification of the reverse micelles method, but avoiding the need of surfactants or polyols, being the synthetic procedure under patent submission. Nanoparticles were chemically coated with silica by the Stöber process in order to generate surface functionalities. The aim of the project is to define material characteristics in order to develop nanoparticles with proper dimensions, highest magnetic moment and most useful surface functionalities for biotechnological applications. The complete characterization of this new material and various intermediates was performed by X-Ray powder diffraction (XRPD) at both ambient and high temperature conditions, Mössbauer (MS) and Fourier Transform Infrared (FTIR) spectroscopies and Transmission Electron Microscopy (TEM). XRPD data were collected in the air on a computer-controlled Philips X’Pert Pro diffractometer on which a X’celerator (RTMS) counter and a Antoon Paar HTK 16 High Temperature Camera were mounted. High temperature measurements were performed up to 700°C with a heating rate of 60°C/min and 2 min rest at each measurement temperature. XRPD at room temperature and MS data indicate that both untreated and heat treated at 400°C samples are composed of maghemite, while those heat treated at a 600°C are composed essentially of hematite, even though some peaks assigned to maghemite are evident. The FTIR spectra confirm the presence of iron- and silicon-oxygen bonds together with a weak band attributed to OH groups. In situ high temperature experiments show that the maghemite--hematite phase transformation occurs between 500° and 550°C. Following [1], the study of the phase transformation is now in progress. TEM images showed a highly mono-disperse nanoparticle population with a mean size around 10 nm.