Synthesis of water dispersed Fe 3 O 4 @ZnO Composite Nanoparticles by the Polyol Method
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Synthesis of water dispersed Fe3O4@ZnO Composite Nanoparticles by the Polyol Method Yesusa Collantes1, Oscar Perales-Perez2, Oswald N. C. Uwakweh2 and Maxime J.-F.Guinel3 1 Department of Physics, University of Puerto Rico, Mayaguez, PR 00680 USA 2 Department of Engineering Science and Materials, University of Puerto Rico, Mayaguez, PR 00680 USA 3 Department of Physics, University of Puerto Rico, San Juan, PR 00936-8377 USA ABSTRACT Water-soluble Fe3O4@ZnO composite nanoparticles (NPs) were synthesized using a polyol route. The effects of the addition of the ZnO phase were evaluated by varying the Zn/Fe molar ratio in the 0.25-1.00 range as a function of the reaction time. X-ray diffractometry confirmed the formation of the magnetite and ZnO phases and suggested the possible formation of a composite structure. Also, using this method, pure magnetite and ZnO NPs were synthesized. The average crystallite sizes were estimated to 6.3 ± 0.3 nm and 8.6 ± 0.6 nm for magnetite and ZnO NPs, respectively. The samples were examined using transmission electron microscopy. Fourier transform infrared spectra indicated the presence of adsorbed species onto the solids surface, which may explain the good stability of the materials in water. Photoluminescence measurements at room temperature for pure ZnO nanoparticles exhibited the characteristic excitonic emission around 395 nm. Vibrating Sample Magnetometer measurements at room temperature evidenced the superparamagnetic behavior of magnetite nanocrystals, with a saturation magnetization of 60emu/g. The maximum magnetization ranged from 28 to 54emu/g for the composite NPs. Mössbauer spectroscopy measurements at room temperature showed evidence of evolving Fesites associated to superparamagnetic particles, as reflected on the coexistence of prominent doublet peaks and very weak sextet peaks. I.-INTRODUCTION Composite NPs have attracted much attention due to their unique physico-chemical properties and potential applications. These heterostructured systems present multifunctional properties arising from the synergy between co-synthesized materials [1]. The use of these NPs for Photodynamic Therapy (PDT) relies on the fact that semiconductor nano-materials could generate singlet oxygen and becomes a new generation of photosensitizers (PS) [2]. ZnO is an excellent PS candidate due to its nontoxicity and ability to biodegrade [3,4]. Moreover, it displays high thermal and chemical stabilities [5]. Furthermore, ZnO is a high quality semiconductor material with a band gap of 3.4 eV, is transparent in the UV region and has a large excitation binding energy at room temperature (60 meV) [6]. ZnO has the hexagonal wurtzite structure with lattice parameters a = 3.29Å, and c = 5.24 Å [6]. In turn, superparamagnetic magnetite combines high magnetic susceptibility and saturation magnetization with low remanence and low coercivity, finding multiple applications in bioseparation, targeted drug delivery, immunoassays and biosensors [7]. Therefore, the development of a composite Fe3O4@ZnO structure cou
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