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Ahmadi R.,Sharif University of Technology | Ahmadi R.,Tehran University of Medical Sciences | Masoudi A.,Sharif University of Technology | Madaah Hosseini H.R.,Sharif University of Technology | Gu N.,Jiangsu Key Laboratory of Biomaterials and Devices
Ceramics International | Year: 2013

In the present study, a one step hydrothermal process was employed to synthesize magnetite nanoparticles using oleic acid as surfactant agent at 140 °C. Effects of reaction time and alkalinity were studied on particles size and morphology. By changing these parameters, some monodisperse spherical nanoparticles with mean particle size between 2.71 and 13.88 nm were synthesized and characterized via TEM, XRD, VSM, TGA and FT-IR techniques. Assuming the Avrami behavior of particles formation, a kinetics equation was proposed for the transformation rate at 140 °C. Using some simplifying assumptions, nucleation and growth rates were calculated for the hydrothermal formation of magnetite nanoparticles at 140 °C. © 2012 Elsevier Ltd and Techna Group S.r.l.

Ahmadi R.,Sharif University of Technology | Gu N.,Jiangsu Key Laboratory of Biomaterials and Devices
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2013

In this work, ferrofluids containing dextran coated magnetite nanoparticles have been synthesized via co-precipitation method. FT-IR results verified presence of dextran molecules on the particles surface. TEM results showed that mean particle size is 7.23 nm, while mean hydrodynamic size determined via PCS technique varies between 39.8 and 125.8 nm depending on the ferrofluid concentration. The maximum hydrodynamic size was obtained in mid concentrations. To the best of our knowledge, effect of concentration on mean hydrodynamic size has not been systematically studied before. VSM results confirmed the superparamagnetic behavior of the synthesized nanoparticles with saturation magnetization of 57.82 emu/g. The stable ferrofluids were intravenously injected into mice and used as MRI contrast agent. Results showed that these ferrofluids can be considered as potential MRI contrast agents especially for imaging lymphatic system. © 2012 Elsevier B.V. All rights reserved.

Ahmadi R.,Sharif University of Technology | Malek M.,University of Tehran | Hosseini H.R.M.,Sharif University of Technology | Shokrgozar M.A.,Pasteur Institute of Iran | And 4 more authors.
Materials Chemistry and Physics | Year: 2011

Magnetite nanoparticles (mean particle size ranging from 10 to 20 nm) were prepared by a biomoleculeassisted solution-phase approach under ultrasonic irradiation. Cysteine was used as the capping agent in the solution. The results show that cysteine could be an efficient biocapping agent in producing Fe3O4 nanoparticles. The crystal structure and magnetic properties of the nanoparticles were characterized by XRD and VSM techniques, respectively. FT-IR was used to investigate the presence of cysteine on the nanoparticles surface. The influence of pH value of the solution on the size distribution and hydrodynamic size of nanoparticles were studied by TEM and DLS methods, respectively. The MTT assay performed by incubation of L929 cells, showed the good biocompability of synthesized ferrofluids. In vitro T1 and T2 relaxivity measurements along with in vivo studies, which were conducted on rats, demonstrate that synthesized nanoparticles are applicable as the contrast agents, especially for imaging of the lymphatic system. © 2011 Elsevier B.V. All rights reserved.

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