Structural and Functional Properties of Iron (II, III)-Doped ZnO Monodisperse Nanoparticles Synthesized by Polyol Method
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Structural and Functional Properties of Iron (II, III)-Doped ZnO Monodisperse Nanoparticles Synthesized by Polyol Method Yesusa Collantes1 and Oscar Perales-Perez2 1
Department of Physics, University of Puerto Rico at Mayaguez, Mayaguez 00980, PR Department of Engineering Science and Materials, University of Puerto Rico at Mayaguez, Mayaguez, PR, 00680-9044 ABSTRACT In this work, bare and (Fe3+ and Fe2+)-doped ZnO nanoparticles (NPs) have been synthesized in a polyol medium at 180oC. The synthesis in polyol allows a precise control of doping under sizecontrolled conditions. The Fe concentration varied in the 0-2 at. % range. As-synthesized samples were characterized by X-ray diffraction (XRD), Fourier Transform Infrared (FT-IR), Photoluminescence (PL) spectroscopy and Vibrational Sample Magnetometry (VSM). XRD measurements confirmed the formation of well crystallized wurtzite ZnO with absence of secondary phases in bare and doped samples; the average crystallite size was estimated at 8.4 ± 0.3 nm for bare ZnO NPs. Systematic shifts in the main diffraction peaks due to the incorporation of the dopant species were observed in the Fe3+ and Fe2+ doped-ZnO samples. FTIR analyses evidenced the presence of organic moieties on the surface of the nanoparticles that are associated to the functional groups of polyol by-products; these adsorbed species could explain the observed stability of the NPs when suspended in water. PL measurements (excitation wavelength 345 nm) reveled that a tuning in the emission bands of ZnO NPs can be achieved through doping. VSM measurements evidenced a weak but noticeable ferromagnetic response at room temperature (RT) in doped samples. 2
INTRODUCTION Zinc Oxide (ZnO) is an important wide band gap semiconductor (3.3 eV) with excellent optical properties. Hexagonal ZnO-wurtzite structure (a = 3.29 Å, and c = 5.24 Å), is transparent in the UV region and exhibits a large excitation binding energy at room temperature (60 meV) [1]. ZnO has been focus of many research in the last decades due to its applications in optics and optoelectronics [2,3]. Recently, a renewed interest of researchers in ZnO at the nanoscale is based on the fact that Zinc oxide (ZnO) nanoparticles (NPs) display unique chemical and physical properties and numerous potential applications. Doping of ZnO NPs also has been explored as an attempt to enhance and/or tune their functional properties and enable these NPs to find novel applications not only in spintronics [4], but also in biology and medicine, including biological fluorescence labeling, imaging, diagnosis and photo-dynamic therapy as theranostics materials [5][6] . ZnO is a likely material for biological applications since it is non-toxic, biodegradable [7,8], presents high thermal and chemical stabilities [9]. Although the doping of ZnO with different transition metal ions has been reported elsewhere, the effect of the dopant oxidation state on the materials properties at the nanoscale has not been altogether addressed yet. Accordingly, the present research is focused on
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