Porous magnets

Debra Rolison (right) was born in Sioux City, Iowa in 1954. She received a B.S. in Chemistry from Florida Atlantic University in 1975 and a Ph.D. in Chemistry from the University of North Carolina at Chapel Hill in 1980 under the direction of Prof. Royce W. Murray. She joined the Naval Research Laboratory as a research chemist in 1980 and currently heads the Advanced Electrochemical Materials section. She is also an Adjunct Professor of Chemistry at the University of Utah. Her research at the NRL focuses on multifunctional nanoarchitectures, with special emphasis on new nanostructured materials for catalytic chemistries, energy storage and conversion, biomolecular composites, porous magnets, and sensors. 

O Brien SM, Sloane RP, Thomas OR, Dunnill P, Characterization of non porous magnetic chelator supports and their use to recover polyhistidine-tailed T4 lysozyme from a crude E. coli extract, I. Biotechnol., 54 53-67, 1997. 

Another way to explore comes from a new result recently evidenced in our group, which was just cited in the introduction. It concerns VSB-1 (for Versailles Santa Barbara), a nickel oxyfluorophosphate [22] which is together porous, magnetic and ion exchanger, and which exhibits the largest pores ever discovered with synthetic solids. Indeed the tunnels are 24-rings (Fig. 16). Beside its structural characteristics, it provides also one of the rare examples of a porous solid with only water as template. If one remembers that the largest known pores exist in the mineral Cacoxenite [80], and that these pores are filled only by water molecules, this probably represents a new field of research in this area. 

As a new concept of inorganic membranes, the potential interest of porous magnetic films as separative barriers based on magnetic selectivity toward para-and diamagnetic species has been recently pursued. The idea is to promote magnetic interactions within the pores of the membrane in order to separate gas molecules or metallic cations with very close size, but different magnetic behavior (Table 25.4). 

Nitrogen-based radicals like nitroxides and verdazyl derivatives fulfill the basic requirements, since they share high stability and persistency and can be functionalized to coordinate metal ions. Charged radicals such as tetracyanoeth-ylene [68, 69] and tetracyanoquinone radical anions have also been reported [70], and a special case is represented by the o-quinone ligands that can be found in different oxidation states in valence tautomeric compounds [71]. Recently, PTM radicals substituted with carboxylate groups have been used to obtain metal-radical coordination polymers, which, in some cases, exhibit porous structures and relevant magnetic properties. Example of such porous magnets will be reported in detail in Section 4.3.3 [72]. 

Given the very considerable literature on molecule based magnets (MBMs), which includes a number of detailed books and reviews, 167-169, 172] pj-incipal attention here is given to describing the recent emergence of porous magnets. 

Reaction with, or glutaraldehyde-coupled to, non-porous magnetic materials Reaction with (17) via glutaraldehyde-coupling... 

Preparation of Porous Magnetic Nanocomposite Materials Using Highly Concentrated Emulsions as Templates... 

Fig. 15. Scanning electron micrograph of 10 ym monodisperse porous magnetic particles.

Synthesis of porous magnetic hollow silica nanospheres for nanomedidne application. loumal of Physical Chemistry C, 111(47), 17473-7. 

Ugelstad et al. have also developed mej hj)ds for preparation of porous, magnetic and nonspherical particles with a broad variation in chemical structures and miscibilities (hydrophobic, hydrophilic). The particles may thus be "tailor-made" and filled or coated with various compounds and dispersed in various carrier fluids to suit a yi e range of important applications in industry, medicine and research. Some of these applications are illustrated schematically in Fig. 1. 

Large-scale synthesis of porous magnetic composites for catalytic applications... 

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