Vol.:(0123456789) 1 3 J Mater Sci: Mater Electron DOI 10.1007/s10854-017-6395-7 Efect of ZnO coating on two diferent sized α-Fe nanoparticles: synthesis and detailed investigation of their structural, optical, hyperfne and magnetic characteristics A. K. Rathore 1,2,3  · S. P. Pati 2,4  · Manojit Ghosh 3  · A. Roychowdhury 2,5  · D. Das 2   Received: 3 November 2016 / Accepted: 16 January 2017 © Springer Science+Business Media New York 2017 Mössbauer study traces some paramagnetic phase formed due to the surface passivation layer along-with larger parti- cles of Fe in the ordered state. 1 Introduction In recent years, great interest has been focused on the study of multifunctional nanocomposite (NC) materials [1, 2]. This is because; the physical and chemical properties of these composite materials can be tuned by relative sizes of the constituent materials in one entity. The multifunctional composite nanostructures exhibit diferent physical proper- ties over the single-component materials. Thus, these com- posites have aroused wide research interest for their huge technological applicability such as magnetic immobiliza- tion [3], drug targeting [4], biological labeling [5], etc. Our interest in the present work is related to synthesis of com- posites containing a magnetic metal in a nonmagnetic host. The magnetic properties of these nanocomposites can be tailored easily by controlling the size of metal crystallites in the nonmagnetic matrix. At the same time better stability can easily be achieved with less agglomeration. So far, var- ious approaches have been made to synthesize metal–metal oxide magnetic-fuorescent bi-functional nanocomposites. Okasha et al. [6] synthesized metal/semiconductor Ag/ CdSe core/shell hybrid NC by pyrolysis of organometallic compound followed by the traditional method of synthe- sizing CdSe. It demonstrates that exciton–phonon interac- tion is in the weak coupling regime. Liu et al. [7] studied the microwave-absorption properties of ZnO coated iron nanocapsules. In the present investigation, bi-functional nanocomposites having metal α-Fe nanoparticles (NPs) embedded in the semiconductor ZnO matrix have been syn- thesized via the chemical route. Abstract The growth of metal–semiconductor (α-Fe/ ZnO) bi-functional nanocomposites (NCs) by a wet-chem- ical route has been reported in the present article. Struc- tural characterization by X-ray difraction measurements confrmed the formation of the pure phase nanocomposite along with some oxide impurity appeared as the surface passivation layer on Fe nanoparticles. Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopic studies have demonstrated the nature of the functional groups present in the samples. A red shift in the ultraviolet– visible (UV–vis) spectrum of the NCs indicates the band gap modifcation of ZnO due to the presence of metallic α-Fe nanoparticles in close proximity. Photoluminescence (PL) emission spectra of the NCs show a blue shift with respect to the pristine ZnO which corroborates the close- proximity efect. The successful formation of nanocompos- ite is also evidenced from the band shift observed in UV– Vis and PL spectra. Some defect related emission peaks are also traced in the PL spectra. Magnetization measurements reveal that the saturation magnetization is very high for these NCs attributed to the dominant surface contribution. * Manojit Ghosh manojit_ghosh1@redifmail.com 1 UGC-DAE Consortium for Scientifc Research, University Campus, Khandwa Road, Indore 452001, India 2 UGC-DAE Consortium for Scientifc Research, III/LB-8, Bidhannagar, Kolkata 700098, India 3 Indian Institute of Engineering Science and Technology, Shibpur, Howrah 711103, India 4 Department of Electronic Engineering, Tohoku University, Sendai 980-7985, Japan 5 Department of Physics, Krishnath College, Berhampore, West Bengal 742101, India