Superparamagnetic iron nanoparticles

As another method, sonolysis has been developed by Suslick to decompose carbonyl metal complexes into nanopowders, nanostructured materials, and nanoparticles in solution. Superparamagnetic iron nanoparticles stabilized by polyvinylpyrrolidone (PVP) or oleic acid were thus obtained upon sonochemical decomposition of... 

Muller, K., Skepper, J.N., Posfai, M., Trivedi, R., Howarth, S., Corot, C., Lancelot, E., Thompson, P.W., Brown, A.P., and Gillard, J.H. (2007) Effect of ultrasmall superparamagnetic iron oxide nanoparticles (Ferumoxtran-10) on human monocyte-macrophages invitro. Biomaterials, 28 (9), 1629-1642. 

Figure 1. MSC accumulate within the scar area. MSC fed with superparamagnetic iron oxide nanoparticles and injected into the border zone of infarcted myocardinm migrate into the infracted area.

Most clinically used nanoparticle contrast agents are iron-oxide based and are grouped into two categories Superparamagnetic iron oxides (SPIOs) are between 500 nm and 50 nm, and ultra-small SPIOs (USPIOs), which are smaller than 50 nm. 

Figure 8 Temperature-dependent Mossbauer spectra of metallic iron nanoparticles in zeolite NaX (a). The superparamagnetic blocking temperature Ti is aroimd 40 K. The solid lines have been calculated by a relaxation formalism assuming a hyperfine field distribution as shown in (b) with a bimodal size distribution of metallic iron particles. (Reprinted from Schiinemann, Winkler, Butzlaff and Trautwein. With kind permission from Springer Science Business Media)...

Superparamagnetic nanoparticles can form chains even at zero field as has been demonstrated by simulations and by experiment in a dispersion of iron nanoparticles at zero field. Ring formation happens by unpaired dipoles at the ends of chains and have also been observed with 27 nm cobalt particles. External magnetic fields can by applied in order to orient flexible chains in one direction enabling formation of superstructures. 

Figure 1. The temperature dependence of specific magneti2ation of the composite left plot and the manifestation of superparamagnetism of the iron nanoparticles and the ferromagnetic ordered clusteis of Fe-Eu-O.

A. Petri-Fink, M. Chastellain, L. Juillerat-Jeaimeret, A. Ferrari, and H. Hofmann Development of functionahzed superparamagnetic iron oxide nanoparticles for interaction with human cancer cells. Biomaterials 26, 2685-2694 (2005). 

Iron nanoparticles prepared by pyrolysis of poly(ferrocenylsilanes) inside periodic mesoporous sihca displayed the absence of room-temperature hysteresis in the magnetization curves which shows their superparamagnetic behavior [55]. However, magnetic properties cannot always be easily interpreted. For example, for this material data analysis of magnetization curves resulted in the ambiguous conclusion that either particle size distribution is bimodal, or iron particles have an oxide layer which behaves as small superparamagnetic nanoparticles. So magnetic measurements should be combined with other techniques (probably, in this case, EXAFS may be useful) to allow more accurate evaluation of particle structure. 

FeCCOs- Sonolysis was also used in our group to prepare iron nanoparticles stabilized by polydimethylphenylene oxide (PPO). The particles were found to be superparamagnetic and to adopt, depending on their size, the a (bcc) or the 7 (fee) structure. This method was extended to other precursors such as Co(NO)(CO)3, recently used by Gedanken to produce cobalt particles. ... 

Frederic T., Carsten E., and Anne M.H. Superparamagnetic iron oxide nanoparticles (SPIONs)-loaded Trojan microparticles for targeted aerosol delivery to the lung. Eur. J. Pharm. Biopharm. 86(1) (2014) 98-104. 

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