Applied Surface Science 302 (2014) 198–204 Contents lists available at ScienceDirect Applied Surface Science journal h om epa ge: www.elsevier.com/locate/apsusc Recent progress in the synthesis of magnetic titania/iron-based, composite nanoparticles manufactured by laser pyrolysis C.T. Fleaca a , M. Scarisoreanu a,∗ , I. Morjan a , R. Alexandrescu a,1 , F. Dumitrache a , C. Luculescu a , I.P. Morjan a , R. Birjega a , A.-M. Niculescu a , G. Filoti b , V. Kuncser b , E. Vasile c , V. Danciu d , M. Popa d a National Institute for Plasma, Laser and Radiation Physics (NILPRP) , Atomistilor 409, P.O. Box MG 36, R-077125, Magurele, Bucharest, Romania b National Institute for Materials Physics (NIMP), Atomistilor 105bis, P.O. Box MG7, R-077125, Magurele, Bucharest, Romania c METAV R&D, C.A. Rosetti 31 and Politehnica University of Bucharest, Independenei 313, Bucharest, Romania d “Babes-Boyai” University, Faculty of Chemistry and Chemical Engineering, Arany Janos 11, Cluj-Napoca, Romania a r t i c l e i n f o Article history: Received 1 July 2013 Received in revised form 20 October 2013 Accepted 21 October 2013 Available online 30 October 2013 Keywords: Laser pyrolysis Iron-based magnetic nanocomposites Titania PACS: 81.16.Mk 75.75.Fk 85.70.-w 81.07.Wx 61.46.Df a b s t r a c t We report the continuous, single step synthesis of titania/iron-based magnetic nanocomposites in a sin- gle step using gas-phase laser pyrolysis technique by separately and simultaneously introducing the precursors (together with C 2 H 4 sensitizer) in the reaction zone: Fe(CO) 5 on the central flow and, using air as carrier, TiCl 4 on the annular coflow. The laser power and, for the last experiment, the injection geometry were modified in order to change the Fe/Ti ratio in the resulted nanopowders. Due to the spe- cific geometry, the reaction zone (visible as a flame) have a reductive inner central zone surrounded by and oxidative environment, allowing the formation of the metallic–carbidic iron and/or iron-doped titania and iron oxide nanophases. The raw Fe-containing nanopowders have a ferromagnetic behavior, those synthesized at higher laser power and gas velocities show significant saturation magnetization M s values (10–12 emu/g), whereas those obtained (with higher yield and carbon content) at lower laser power and gas velocities (using wider central nozzle cross-section) have a very weak magnetization (M s ∼ 0.05 emu/g) in spite of the higher ethylene carried Fe(CO) 5 flow. The powders were annealed in air at 400 ◦ C show lower carbon content and, for those highly Fe-doped, the hematite phase formation. Pre- liminary tests using UV light confirm the photocatalytic action of the annealed nanopowders in salicylic acid degradation process in solution. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Titania (titanium dioxide TiO 2 ) have three main crystallographic forms: anatase, rutile (both tetragonal) and brookite (orthorom- bic). Their most spread application are as fillers in paints, varnishes, plastics or for paper (∼80% of the world consumption). Other appli- cations, which have a ∼8% market share, are as pigment for inks, fibers, rubber, cosmetics or food products. The remaining ∼12% are for producing metallic pure Ti, glass/electroinsulating ceram- ics, electrical conductors, chemical intermediates and catalysts [1]. The last specified application of TiO 2 (especially the anatase form) is related to their photocatalytic properties, allowing the decom- position of organic pollutant compounds or photogeneration of hydrogen, enhanced for is nanosize form, which have a greater specific surface and activity than bulk/micronic-size counterpart ∗ Corresponding author. Tel.: +40 21 4574489; fax: +40 21 4574243. E-mail address: monica.scarisoreanu@inflpr.ro (M. Scarisoreanu). 1 The Senior Researcher Dr. Rodica Alexandrescu had deceased during the prepa- ration of the manuscript. [2]. In order to be applied for wastewater depollution, TiO 2 must have long-term stability, a high efficiency, low-cost and long-term stability [3]. The slurry/suspension TiO 2 reactor is usually employed for this scope, due to the intrinsic high specific surface area, good dispersion conditions and efficient light absorption [4]. After the water purification, the separation of the employed TiO 2 photocat- alyst is required, especially from a large volume of water, which is both cost-expensive and time-consuming even when various solid support immobilization/impregnation techniques were used which also decrease the effective surface photocatalytic area [5]. A convenient way to overcome these drawbacks is to coat a mag- netic nanocore with TiO 2 shell or to connect the TiO 2 to magnetic nano-particles, resulting nanocomposites which can be easily sep- arated with the aid of a magnetic field and eventually recycled [6]. Obviously, a simple mechanical mixture of magnetic and pho- tocatalytic particles (even a very homogeneous one) can’t have the behavior shown by these nanocomposite due to the lack of connectivity between the two components which not allow the high magnetic recovery of the photocatalyst. These new materials belong indeed to the nanocomposites category, fulfilling de defini- tion of being “a multiphase solid material where one of the phases 0169-4332/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.apsusc.2013.10.138