Magnetic and photo-catalyst Fe 3 O 4 –Ag nanocomposite: green preparation of silver and magnetite nanoparticles by garlic extract Shahab Khaghani 1 • Davood Ghanbari 1 Received: 26 August 2016 / Accepted: 11 October 2016 Ó Springer Science+Business Media New York 2016 Abstract At the first step Fe 3 O 4 nanoparticles were syn- thesized via a green hydrothermal method in the presence of garlic (Allium sativum) extract. Then silver nanoparticles and Fe 3 O 4 –Ag (90 %:10 % and 50 %:50 %) nanocom- posites were synthesized by hydrothermal method. The prepared products were characterized by X-ray diffraction pattern, scanning electron microscopy, and Fourier trans- form infrared spectroscopy. Vibrating Sample magne- tometer illustrated that Fe 3 O 4 nanoparticles have super- paramagnetic behaviour. The photo catalytic behaviour of Fe 3 O 4 –Ag nanocomposites was investigated using the degradation of four various azo dyes under ultraviolet light irradiation. The results show that nanocomposites have feasible magnetic and photo catalytic properties. 1 Introduction Most technological and medical applications require mono- disperse nanoparticles to have uniform physical and chemical properties. Small size and large surface-to-vol- ume ratio leads to distinct magnetic properties which are different from those of their bulk structures [1]. This behaviour has been explained as due to the large volume fractions of the atoms in the grain boundary area with unusual properties like spin canting, surface anisotropy, dislocations and super-paramagnetic behaviour. Magnetic separation is considered as a high speed and effective technique for separating magnetic particles. Thus, if the powder adsorbent catalyst is magnetic, it could be recov- ered conveniently by magnetic field [1, 2]. Ferrites are technologically essential materials that are used in the fabrication of magnetic, electronic and microwave devices. These materials have a potential application at high fre- quency range due to their very low electrical conductivity, fairly large magneto-crystalline anisotropy, relatively large saturation magnetization, mechanical hardness low pro- duction costs [3, 4]. Hydrothermal synthesis can be defined as a method of synthesis of single crystals that depends on the solubility of minerals in hot water under high pressure. The crystal growth is performed in an apparatus consisting of a steel pressure vessel called an autoclave, in which a nutrient is supplied along with water. A temperature gradient is maintained between the opposite ends of the growth chamber. At the hotter end the nutrient solute dissolves, while at the cooler end it is deposited on a seed crystal, growing the desired crystal. Advantages of the hydrother- mal method over other types of crystal growth include the ability to create crystalline phases which are not stable at the melting point. Also, materials which have a high vapour pressure near their melting points can also be grown by the hydrothermal method. The method is also particu- larly suitable for the growth of large good-quality crystals while maintaining control over their composition. We have used hydrothermal method for this synthesis. Obviously hydrothermal is a unique method for fabricating nanostructures with specific and controlled morphologies. While predominant morphology.in other methods like sol– gel, sonochemical is nanoparticle. Hydrothermal method provides preferred orientation morphology. In hydrother- mal method because of some particular conditions (high temperature and pressure) the nanoparticles grow in situ and form hierarchical structures [1, 4–6]. & Shahab Khaghani Shahab.khaghani@gmail.com 1 Young Researchers and Elite Club, Arak Branch, Islamic Azad University, Arak, Iran 123 J Mater Sci: Mater Electron DOI 10.1007/s10854-016-5872-8