OICC Press Journal of Nanostructure in Chemistry 2193-8865 3 1 (December 2013) 2013 04 30 Separation of the defect-free Fe3O4-Au core/shell fraction from magnetite-gold composite nanoparticles by an acid wash treatment 10.1186/2193-8865-3-25 EN Hojatollah Montazeri Department of Medical Biotechnology, School of Advanced Medical Technologies, Tehran University of Medical Sciences, Tehran, 1417614411, IR Amir Amani Department of Medical Biotechnology, School of Advanced Medical Technologies, Tehran University of Medical Sciences, Tehran, 1417614411, IR Hamid Reza Shahverdi Department of Materials Engineering, University of Tarbiat Modares, Tehran, 14115-143, IR Emad al din Haratifar Department of Materials Engineering, University of Tarbiat Modares, Tehran, 14115-143, IR Ahmad Reza Shahverdi Biotechnology Research Center, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran, 1417614411, IR Pharmaceutical Sciences Research Center, School of Pharmacy, Tehran University of Medical Sciences, Tehran, 417614411, IR Journal Article 2013 04 30 Abstract Some undesired nanoparticles, such as malformed structures or incomplete core/shell Fe 3 O 4 -Au nanocomposites, might be formed when Fe 3 O 4 -Au core/shell nanocomposites are being synthesized. These impurities should be separated before any applications are performed. In this investigation, magnetic cores (Fe 3 O 4 ) were synthesized using a conventional fabrication method involving coprecipitation of Fe 2+ and Fe 3+ . Carboxyl-capped magnetite-gold composite nanoparticles, measuring ≤50 nm, were then synthesized using a plant extract ( Eucalyptus camaldulensis ). The prepared carboxyl-capped magnetite-gold composite nanoparticles were further subjected to acid treatment for 18 h and characterized with different instrumentation methods. The results of the investigation showed that acid treatment can be applied successfully to separate defect-free Fe 3 O 4 -Au core/shell nanoparticles from different types of Fe 3 O 4 -Au nanocomposites, without any considerable changes in their physiochemical properties.