No abstract

Carbonyl iron (CI) particles were grafted with poly(glycidyl methacrylate) (PGMA) using atom transfer radical polymerization. Compact coating of PGMA largely improved the chemical stability of the particles in an acid environment and thus reduced the common drawback of bare CI particles. Furthermore, due to possible medical applications of CIpolymer systems for magnetic drug targeting, an in-vitro cytotoxicity test was performed using an NIH/3T3 cell line. The cell viability was evaluated by spectrometric assay (MTT).The results show that the prepared particles are not cytotoxic. Moreover, bare CI particles as well as synthesized core-shell particles were suspended in silicone oil, and the rheological behavior of MR suspensions was investigated in controlled shear rate mode under various magnetic field strengths. Dynamic yield stress as a measure of the rigidity of the created internal structures of the suspensions was determined using the Herschel-Bulkley model, which provided a reasonably good fit for rheological data. MR suspensions of PGMA-coated particles exhibited only slightly decreased yield stresses due to their negligibly-affected magnetic performance.Generally, MR suspensions are in most cases subjected to shear flow while exhibiting nearly Newtonian behavior in the absence of a magnetic field (off-state), or develop a yield stress and shear rate-dependent apparent viscosity after the application of an external field (onstate) [1,5,10]. The behavior of MR suspensions can be characterized by the Bingham plastic model [19], which belongs among the most popular models because of its simplicity and sufficient accuracy [20]. Nevertheless, the on-state pseudoplastic behavior of MR suspensions is in contradiction to the Bingham model. Therefore some authors [21][22][23] have employed the All chemicals were used as received. Carbonyl iron (CI) powder (SL grade) with a purity higher than 99.5 % was obtained from BASF (Germany). Glycidyl methacrylate (GMA, 97 %), α-bromo isobutyryl bromide (BiBB, 98 %), (3-aminopropyl) triethoxysilane (APTES, ≥ 98 %), ethyl α-bromo isobutyrate (EBiB, 98 %), triethylamine (Et 3 N, ≥ 99 %), N,N,N´,N´´,N´´-pentamethyldiethylenetriamine (PMDETA, ≥ 99 %), copper bromide (CuBr, ≥ 99 %), anisole (99 %) and aluminum oxide (neural, Brockmann I) were produced by Sigma Aldrich (USA). Other chemicals, namely tetrahydrofuran (THF, p.a.), acetone (p.a.), ethanol

Magnetic nanoparticles based on Fe3O4 were prepared by a facile and rapid one-pot solvothermal synthesis using FeCl3·6H2O as a source of iron ions, ethylene glycol as a solvent and NH4Ac, (NH4)2CO3, NH4HCO3 or aqueous NH3 as precipitating and nucleating agents. In contrast to previous reports we reduce the synthesis time to 30 minutes using a pressurized microwave reactor without the requirement of further post-treatments such as calcination. Dramatically reduced synthesis time prevents particle growth via Ostwald ripening thus the obtained particles have dimensions in the range of 20 to 130 nm, they are uniform in shape and exhibit magnetic properties with saturation magnetization ranging from 8 to 76 emu g(-1). The suggested method allows simple particle size and crystallinity tuning resulting in improved magnetic properties by changing the synthesis parameters, i.e. temperature and nucleating agents. Moreover, efficiency of conversion of raw material into the product is almost 100%.

An international journal to further the chemical sciencesRSC Advances is an international, peer-reviewed, online journal covering all of the chemical sciences, including interdisciplinary fields.The criteria for publication are that the experimental and/ or theoretical work must be high quality, well conducted adding to the development of the field.Thank you for your assistance in evaluating this manuscript. Guidelines to the refereesReferees have the responsibility to treat the manuscript as confidential. Please be aware of our Ethical Guidelines, which contain full information on the responsibilities of referees and authors, and our Refereeing Procedure and Policy.It is essential that all research work reported in RSC Advances is well-carried out and wellcharacterised. There should be enough supporting evidence for the claims made in the manuscript. When preparing your report, please:• comment on the originality and scientific reliability of the work • state clearly whether you would like to see the article accepted or rejected and give detailed comments (with references, as appropriate) that will both help the Editor to make a decision on the article and the authors to improve it Please inform the Editor if:• there is a conflict of interest • there is a significant part of the work which you are not able to referee with confidence • the work, or a significant part of the work, has previously been published • you believe the work, or a significant part of the work, is currently submitted elsewhere • the work represents part of an unduly fragmented investigationFor further information about RSC Advances, please visit: www.rsc.org/advances or contact us by email: advances@rsc.org. Enclosed please find the manuscript entitled "Novel synthesis of core-shell urchin-like ZnO coated carbonyl iron microparticles with enhanced magnetorheological activity". The paper is intended for publication in RSC advances if you consider it suitable. We believe that this article describing novel synthesis of inorganic-inorganic core-shell particles with unique urchin-like morphology having extraordinary rheological properties under applied magnetic field and further, exhibiting considerably enhanced sedimentation and thermo-oxidation stability with great potential in wide areas of industrial applications. We also hope that article is matching with the scope of your journal categories "Inorganic" and "Rheology and colloids" and is attractive enough in the same time. Sincerely yours Miroslav Mrlík et al. (Corresponding author)E-mail: mrlik@ft.utb.cz tel: +420 57 603 8128, fax: +420 576 031 444 ABSTRACTThe overall stability (thermo-oxidation, sedimentation) of the MR suspensions is a crucial problem decreasing their potential applicability in the real life. In this study the unique functional coating of carbonyl iron (CI) particles with ZnO structures was presented in order to develop new MR suspension based on the core-shell ZnO/CI urchin-like dispersed particles. The two-step synthesis provides the suitable core-shell particles wit...