ABSTRACT
Biomedical and biotechnological applications of magnetic nanoparticles and their dispersions in liquids are found to be potentially useful. An exponential growth in publications of papers, reviews and patents has been observed. Possibilities of their indiscriminate use on individual as well as environmental health hazards are also investigated. Still, there appears to be a good scope for further research work in the field. Even a small improvement either in preparation method or development of novel nanoparticles may prove to be beneficial in longer run. With this aim in mind, the present review discussed the work carried out in author's laboratory on synthesis and characterization of certain biomagnetic particles and biocompatible fluids composed of these particles. Modified methods were used to synthesize these particles. Notable amongst these are direct binding of biomolecules or drug on magnetic nano particles, low Curie point functionalized magnetic particles, targeted drug delivery system, photodyne therapy, anti-bacterial activity and bioremediation of marine fungi. Advantages and limitations of these work in light of recent work is also discussed.
Subject(s)
Magnetite Nanoparticles , Biotechnology , Drug Delivery Systems , Humans , MagneticsABSTRACT
Study of energy transport velocity of light is an effective background for slow, fast, and diffuse light and exhibits the photonic property of the material. We report a theoretical analysis of magnetic field dependent resonant behavior in forward-backward anisotropy factor, light diffusion constant, and energy transport velocity for bidispersed magnetic colloids. A bidispersed magnetic colloid is composed of micrometer size magnetic spheres dispersed in a magnetic nanofluid consisting of magnetic nanoparticles in a nonmagnetic liquid carrier. Magnetic Mie resonances and reduction in energy transport velocity accounts for the possible delay (longer dwell time) by field dependent resonant light transport. This resonant behavior of light in bidispersed magnetic colloids suggests a novel magnetophotonic material.
Subject(s)
Colloids/chemistry , Energy Transfer , Models, Chemical , Models, Molecular , Rheology/methods , Computer Simulation , Light , Magnetic FieldsABSTRACT
Mie scattering functions for a magnetizable sphere whose relative refractive index is dependent on the externally applied magnetic field are computed for four different sizes of the sphere. It is found that Mie resonances are observed at certain critical fields when the incident light is polarized with its electric vector perpendicular to the applied field. The width of resonance as well as the critical fields shifts with the increase in size of the spheres. Results are compared with the experimentally observed scattering effects in a dispersion of magnetite spheres in a ferrofluid.
ABSTRACT
An unusual emission of light is observed when a coherent light beam is passed through a mixture of a magnetorheological suspension and a ferrofluid that is subjected to a critical magnetic field. When first the incident light is removed and then the field is switched off, a flash of light is observed. In this Letter certain characteristics of this unusual emission are reported. Our findings suggest that a part of the incident light energy is magnetically trapped within the medium. Upon removal of the field, the same is released. Several physical phenomena that may give rise to such emission are discussed. The magnetically tunable emission will be useful to develop photonic devices.
ABSTRACT
In the present investigation we report the effect of capillary diameter and the direction of applied magnetic field on the rotational viscosity of water and kerosene based ferrofluids. We found that changes in the field induced rotational viscosity are larger in the case of water based magnetic fluid than that of kerosene based fluid. The field induced rotational viscosity is found to be inversely proportional to the capillary diameter and it falls exponentially as a function of the angle between the direction of field and vorticity of flow. Magnetophoretic mobility and hydrodynamic volume fraction of nanomagnetic particles are determined for above cases.
ABSTRACT
Magnetically induced elongation of magnetic nanocomposite micelles is observed microscopically. The superparamagnetic particles of double-surfacted water based ferrofluid are incorporated in spherical micelles of cetyltrimethyl ammonium bromide (CTABr) mixed with sodium salicylate salt (NaSal). Under the application of an external magnetic field these spherical magnetic micelles deformed to ellipsoids. The shape distortion occurs instantaneously and disappears when the external field is removed. This magnetodeformational effect is analyzed using linear magnetization and Hookean elasticity.
ABSTRACT
Electron spin resonance (ESR) spectra of magnetic fluids involving polydispersed Zn(0.5)Fe(0. 5)Fe(2)O(4) (FZ5) and Zn(0.7)Fe(0. 3)Fe(2)O(4) (FZ7) nanomagnetic particles are scanned from 4.2 to 300K. The FZ7 fluid exhibits certain distinct features below 40K which are different from FZ5 fluid. These include (i) an isotropic shift in resonance field in zero-field-cooled ESR study, (ii) deviation of resonance field from sin(2)theta behavior (where theta is the angle between axis of the particle and field) in field cooled (FC) sample and (iii) abrupt increase in anisotropy field for FC sample. The results are analyzed in light of the core-shell model for nanomagnetic particles.
ABSTRACT
Magnetically induced diffraction patterns by micron sized magnetic spheres dispersed in a ferrofluid disappear at a certain critical magnetic field. This critical field is found to depend on the concentration of the ferrofluid and on the volume of the magnetic spheres. We attribute this effect to the zero forward scattering by magnetic spheres as predicted by Kerker, Wang, and Giles [J. Opt. Soc. Am. 73, 765 (1983)]. We suggest that such a dispersion can be used to study the optical analogues of localization of electrons in condensed matter, the Hall effect, and the anisotropic diffusion, etc. The combination of the micron sized magnetic spheres and the ferrofluid will also be useful to design magnetically tunable photonic devices.
ABSTRACT
Effective viscosity of a magnetic fluid as a function of applied magnetic field oriented in the perpendicular direction of the capillary flow is determined. Close agreement with the Shliomis expression derived on the basis of effective field method is observed.
ABSTRACT
Magnetically induced extinction and birefringence of systems containing a mixture of ultramicroscopic particles with different optical and magnetic properties have been theoretically investigated. It is shown that the effects may exhibit an extremum and an inversion in sign with increasing applied field strength if the system contains diamagnetic as well as ferromagnetic particles. The field strengths at which the effects exhibit the extremum and the inversion in sign are found to depend on the relative number distribution of the two types of particles and on the wavelength of the incident radiation. Experimental results from systems containing particles of bentonite and chromium ferrite in different proportions are also discussed.
ABSTRACT
A polydisperse sample can be statistically represented by a log-normal distribution having two parameters, viz., geometrical standard deviation sigma(g) and modal size parameter X(m). In an earlier paper a method to determine sigma(g) from the shift in the angular position of the maximum in Itheta(2) vs theta plot was discussed. The present paper describes a method of determining the other parameter X(m) from the polarization measurement in the forward direction. This can be achieved by comparing the angular position of maxima in P (degree of polarization) vs theta with that of the similar curve of a single particle. Certain experimental results are also discussed. This method is expected to be useful in routine particle size analysis.
