Colloid Polym Sci DOI 10.1007/s00396-016-3972-x ORIGINAL CONTRIBUTION Iron nanoparticles on colloidal substrates Bogar Carpinteiro-Carreto 1 · Benjam´ ın M. Mar´ ın-Santib´ a˜ nez 2 · Jos´ e P´ erez-Gonz´ alez 3 · Francisco Rodr´ ıguez-Gonz´ alez 4 · H´ ector J. Dorantes-Rosales 5 · Rodrigo S´ anchez 6 Received: 25 May 2016 / Revised: 20 August 2016 / Accepted: 21 October 2016 © Springer-Verlag Berlin Heidelberg 2016 Abstract Iron nanoparticles are of interest for possible applications such as remediation of soil and water, and for their magnetic properties. In the present work, a sim- ple method for producing iron nanoparticles on a colloidal substrate is presented. These composites have potential applications related to their surface and magnetic properties. Keywords Nanocomposites · Core-shell composites · Iron nanoparticles · Colloidal silica · Nanoparticles  Rodrigo S´ anchez rodrsanchez@xanum.uam.mx 1 Facultad de F´ ısica, Universidad Veracruzana, Circuito Gonzalo Aguirre Beltr´ an s/n, Zona Universitaria, Xalapa 91000, Veracruz, Mexico 2 Escuela Superior de Ingenier´ ıa Qu´ ımica e Industrias Extractivas, Instituto Polit´ ecnico Nacional, U.P.A.L.M. C.P. 07738, Col. Lindavista, Mexico City, Mexico 3 Laboratorio de Reolog´ ıa y F´ ısica de la Materia Blanda, Escuela Superior de F´ ısica y Matem´ aticas, Instituto Polit´ ecnico Nacional, U.P.A.L.M. C.P. 07738, Col. Lindavista, Mexico City, Mexico 4 Departamento de Biotecnolog´ ıa, Centro de Desarrollo de Productos Bi ´ oticos, Instituto Polit´ ecnico Nacional, Col.San Isidro C.P. 62731, Yautepec, Morelos, Mexico 5 Departamento de Metalurgia y Materiales, Escuela Superior de Ingenier´ ıa Qu´ ımica e Industrias Extractivas, Instituto Polit´ ecnico Nacional, U.P.A.L.M. C.P. 07738, Col. Lindavista, Mexico City, Mexico 6 Departamento de F´ ısica, Universidad Aut´ onoma Metropolitana Unidad Iztapalapa, Av. San Rafael Atlixco 186, Col. VicentinaC.P. 09340, Mexico City, Mexico Introduction Iron nanoparticles are of interest for use, for example, in water and soil remediation [22, 37]. Previous work has mostly examined the synthesis and use of iron nanoparticles in bulk suspensions [22, 35, 37, 38] or the coating of iron cores with inert materials [4, 5, 12, 28]. However, synthe- sizing iron nanoparticles on colloidal substrates has several potential advantages, such as making them easier to incor- porate into filters, for example, if the colloidal substrate can be sintered or otherwise incorporated into ceramics or other suitable materials. While the reverse configuration—an iron core surrounded by a shell—has been obtained experimen- tally before [17, 19], colloidal cores decorated with iron constitute a novel system. Since nanoparticles decorating a colloidal substrate would have a surface area exposed to the bulk medium similar to that of suspended nanoparticles, properties governed by contact between said surfaces and the bulk, and by the nanoparticles’ internal structure, such as catalytic and electrochemical properties, would be largely the same, but properties such as diffusion and sedimentation would be governed by the much larger cores. Such composites would also be of interest for their mag- netic properties. Their overall magnetic susceptibility and other relevant properties would be different from those of iron nanoparticles and, of course, from those of bare silica. This could be of interest, for example, for active microrheol- ogy [7], particularly if the substance of interest has modest magnetic susceptibility. They could also be of interest for self-assembly studies in the presence of external magnetic fields [33]. Silica colloids have various useful features such as non- toxicity and high resistance to corrosion, being stable in common solvents like water and ethanol, and having sur- faces than can be easily modified chemically if desired.