In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

Ferromagnetic materials

Chemistries that Facilitate Nanotechnology Kim E. Sapsford,† W. Russ Algar, Lorenzo Berti, Kelly Boeneman Gemmill,‡ Brendan J. Casey,† Eunkeu Oh, Michael H. Stewart, and Igor L. Medintz*,‡ †Division of Biology, Department of Chemistry and Materials Science, Office of Science and Engineering Laboratories, U.S. Food and Drug Administration, Silver Spring, Maryland 20993, United States ‡Center for Bio/Molecular Science and Engineering Code 6900 and Division of Optical Sciences Code 5611, U.S. Naval Research Laboratory, Washington, D.C. 20375, United States College of Science, George Mason University, 4400 University Drive, Fairfax, Virginia 22030, United States Department of Biochemistry and Molecular Medicine, University of California, Davis, School of Medicine, Sacramento, California 95817, United States Sotera Defense Solutions, Crofton, Maryland 21114, United States

Functionalizing nanoparticles with biological molecules: developing chemistries that facilitate nanotechnology.

Nanostructures have attracted huge interest as a rapidly growing class of materials for many applications. Several techniques have been used to characterize the size, crystal structure, elemental composition and a variety of other physical properties of nanoparticles. In several cases, there are physical properties that can be evaluated by more than one technique. Different strengths and limitations of each technique complicate the choice of the most suitable method, while often a combinatorial characterization approach is needed. In addition, given that the significance of nanoparticles in basic research and applications is constantly increasing, it is necessary that researchers from separate fields overcome the challenges in the reproducible and reliable characterization of nanomaterials, after their synthesis and further process (e.g. annealing) stages. The principal objective of this review is to summarize the present knowledge on the use, advances, advantages and weaknesses of a large number of experimental techniques that are available for the characterization of nanoparticles. Different characterization techniques are classified according to the concept/group of the technique used, the information they can provide, or the materials that they are destined for. We describe the main characteristics of the techniques and their operation principles and we give various examples of their use, presenting them in a comparative mode, when possible, in relation to the property studied in each case.

/pdf/characterization-techniques-for-nanoparticles-comparison-and-2ubze3ehrc.pdf

Characterization techniques for nanoparticles: comparison and complementarity upon studying nanoparticle properties

Recent advances in polyaniline research: Polymerization mechanisms, structural aspects, properties and applications

The tremendous interest in magnetic nanoparticles (MNPs) is reflected in published research that ranges from novel methods of synthesis of unique nanoparticle shapes and composite structures to a large number of MNP characterization techniques, and finally to their use in many biomedical and nanotechnology-based applications. The knowledge gained from this vast body of research can be made more useful if we organize the associated results to correlate key magnetic properties with the parameters that influence them. Tuning these properties of MNPs will allow us to tailor nanoparticles for specific applications, thus increasing their effectiveness. The complex magnetic behavior exhibited by MNPs is governed by many factors; these factors can either improve or adversely affect the desired magnetic properties. In this report, we have outlined a matrix of parameters that can be varied to tune the magnetic properties of nanoparticles. For practical utility, this review focuses on the effect of size, shape, composition, and shell-core structure on saturation magnetization, coercivity, blocking temperature, and relaxation time.

http://lee.chem.uh.edu/2013/Int.%20J.%20Mol.%20Sci.%202013,%2014,%2015977.pdf

Tuning the Magnetic Properties of Nanoparticles

An overview on magnetic of nanostructured magnetic materials is presented, with particular emphasis on the basic features displayed by granular nanomagnetic solids. Besides a review of the basic concepts and experimental techniques, the role of structural disorder (mainly the distribution of grain sizes), interparticle magnetic interactions and surface effects are also discussed with some detail. Recent results, models and trends on the area are also discussed.

Superparamagnetism and other magnetic features in granular materials: A review on ideal and real systems

Spherical magnetic nanoparticles with narrow size distribution and organic capping were diluted in paraffin with different concentrations to verify the role of dipolar interactions on the macroscopic magnetic behavior. Increasing concentration of magnetic nanoparticles leads to higher blocking temperatures. The experimental data were analyzed by means of a recently proposed model that takes into account magnetic interactions of dipolar origin, and an excellent agreement was found. Considering the magnetic interaction among particles it was possible to obtain the real magnetic moment and estimate structural parameters that are consistent with the ones obtained by small angle x-ray scattering and transmission electron microscopy.

Effect of dipolar interaction observed in iron-based nanoparticles

This paper describes a solution-phase route to prepare Ag−Fe3O4 colloidal dimer nanoparticles (NPs) with a dumbbell-like shape. Results show enhancement of the magnetic anisotropy and large coerciv...

Ag−Fe3O4 Dimer Colloidal Nanoparticles: Synthesis and Enhancement of Magnetic Properties

Colloidal iron oxide magnetic nanoparticles were synthesized from high temperature reaction of Fe(acac)3 solution. The size of particles was easily tunable from 4 to 22 nm in only one step in the synthesis process. From TEM images the particles showed cubic–faceted shape with good homogeneity and narrow size distribution. Preliminary magnetic measurements show the usual superparamagnetic and blocked regimes depending on temperature.

http://iopscience.iop.org/article/10.1088/0957-4484/16/9/009/pdf

Tailoring the size in colloidal iron oxide magnetic nanoparticles

Synthesis gas is produced by the reaction of light hydrocarbons, primarily methane, in a fluid bed reaction zone of attrition resistant nickel on alpha-alumina catalyst, with steam and oxygen and the conversion level is preserved by limiting the loss of nickel from the reaction and thereby limiting the back reaction of the synthesis gas to form methane in the presence of entrained catalyst in a cooling zone.

Jose M. Vargas

Papers

Superparamagnetism and other magnetic features in granular materials: A review on ideal and real systems

Effect of dipolar interaction observed in iron-based nanoparticles

Ag−Fe3O4 Dimer Colloidal Nanoparticles: Synthesis and Enhancement of Magnetic Properties

Tailoring the size in colloidal iron oxide magnetic nanoparticles

Synthesis gas preparation and catalyst therefor