Inverse magnetorheological fluids

We report a new kind of field-responsive fluids consisting of suspensions of diamagnetic (DM) and ferromagnetic (FM) microparticles in ferrofluids. We designate them as inverse magnetorheological (IMR) fluids for analogy with inverse ferrofluids (IFFs). Observations on the particle self-assembly in IMR fluids upon magnetic field application showed that DM and FM microparticles were assembled into alternating chains oriented along the field direction. We explain such assembly on the basis of the dipolar interaction energy between particles. We also present results on the rheological properties of IMR fluids and, for comparison, of IFFs and bidispersed magnetorheological (MR) fluids. Interestingly, we found that upon magnetic field, the rheological properties of IMR fluids were enhanced with respect to bidispersed MR fluids with the same FM particle concentration, by an amount greater than the sum of the isolated contribution of DM particles. Furthermore, the field-induced yield stress was moderately increased when up to 30 % of the total FM particle content was replaced with DM particles. Beyond this point, the dependence of the yield stress on the DM content was non-monotonic, as expected for FM concentrations decreasing to zero. We explain these synergistic results by two separate phenomena: the formation of exclusion areas for FM particles due to the perturbation of the magnetic field by DM particles, and the dipole-dipole interaction between DM and FM particles, which enhances the field-induced structures. Based on this second phenomenon, we present a theoretical model for the yield stress that semi-quantitatively predicts the experimental results.Projects 12-01-00132, 13-02-91052, 13-01-96047, 14-08-00283 (Russian Fund of Fundamental Investigations), 2.1267.2011 (Ministry of Education of Russian Federation), the Act 211 (Government of the Russian Federation № 02.A03.21.0006). The University of Granada (Acción Integrada con Rusia; Plan Propio 2011). L. Rodríguez-Arco acknowledges financial support by Secretaría de Estado de Educación, Formación Profesional y Universidades (MECD, Spain) through its FPU program

Nanoporous Silica-Based Materials for Sorption of Pharmaceuticals and Biomolecules

Our concern in this paper is to review four kinds of mesoporous silica materials which can be used as potential sorbents for pharmaceuticals. It is known that a continuous development of science, medicine and food industry has an effect on contamination of the natural environment. Moreover, many impurities, such as drugs, vitamins or proteins etc., which get into environment from urban and hospital wastes, can also influence on human organisms. Thus, there is a need to control an amount of those compounds, especially in the natural waters and wastewaters [1-4]. In this work, we present four types of silica materials which can be helpful in water purification by using adsorption process

An effective scaling frequency factor method (ESFF): review and local factors transferability problem

Scaling procedures are known to reproduce very accurate vibrational spectra provided that multiparameter scaling in conjunction with high-quality force fields is carried out. In contrast to purely theoretical approaches (variational and perturbational), they are applicable to large systems. In this work, a brief review of the scaling procedures is given. The emphasis is put on the recently proposed effective scaling frequency factor (ESFF) method [Chem. Phys. Lett., 446, 191, (2007), J. Mol. Spectr., 264, 66, (2010)] - the multiparameter frequency scaling method providing better scaled frequencies than the well-established scaled quantum mechanical (SQM) force field approach. In addition, the results of our calculations on the benzene-based related systems, i.e., benzene and most of its methyl derivatives, are presented. The calculations concern the middle- and low-frequency range of the vibrational spectra, where strong mixing of the local vibrations often takes place. The factors transferability problem is discussed

An effective scaling frequency factor method (ESFF): review and local factors transferability problem

Scaling procedures are known to reproduce very accurate vibrational spectra provided that multiparameter scaling in conjunction with high-quality force fields is carried out. In contrast to purely theoretical approaches (variational and perturbational), they are applicable to large systems. In this work, a brief review of the scaling procedures is given. The emphasis is put on the recently proposed effective scaling frequency factor (ESFF) method [Chem. Phys. Lett., 446, 191, (2007), J. Mol. Spectr., 264, 66, (2010)] - the multiparameter frequency scaling method providing better scaled frequencies than the well-established scaled quantum mechanical (SQM) force field approach. In addition, the results of our calculations on the benzene-based related systems, i.e., benzene and most of its methyl derivatives, are presented. The calculations concern the middle- and low-frequency range of the vibrational spectra, where strong mixing of the local vibrations often takes place. The factors transferability problem is discussed

Amine-functionalized silica particles with magnetic core as magnetically removable adsorbents of Ag(I) ions

Adsorption of silver ions over amine-functionalized silica particles with magnetic core has been studied. This adsorbent has been synthesized via sol–gel method, in the presence of Fe 3 O 4 particles as magnetic cores. As a comparison, magnetic silica adsorbent with non-functionalized surface was also synthesized. As-obtained materials have been characterized by elemental analysis, acid–base titration, nitrogen sorption measurements, X-ray photoelectron spectroscopy and scanning electron microscopy. What is more, parameters of electrical double layer at the silica adsorbent/electrolyte solution interface were also examined. Kinetic of adsorption and isotherms of silver ions were determined. The obtained adsorption of Ag(I) ions for the studied materials was in the range of about 0.2–0.3 mmol/g