Reversible Photo‐Switching of the Magnetization of Iron Oxide Nanoparticles at Room Temperature

Abstract

Optically switchable magnetic materials are becoming increasingly important in the field of high-density information storage media. [1][2][3] We have been trying to prepare new types of magnets in which the magnetic properties can be controlled by photo-illumination. Our previous work has shown that cobalt-iron cyanide exhibits photoinduced magnetization effects due to an internal electron transfer.[4] However, practical examples of such photo-magnetic systems are limited in number [5] because the strategies that are necessary to achieve photoinduced switching in the solid state are yet to be clarified.The use of organized organic assemblies to direct the formation of mesoscopic inorganic structures under mild conditions and the attempts to intercalate inorganic materials into functional organic molecules are also of topical interest. [6] We have focused our attention on composite materials as a novel strategy for realizing such photo-functional magnetic systems. These include the incorporation of organic photochromes into magnetic systems, for example, photo-controllable magnetic vesicles and Langmuir-Blodgett films containing Prussian blue (a ferromagnet at low temperature) and azobenzene. [7] Although the examples described above show interesting photo-responsive phenomena, the results were only achieved at low temperature. It is evident that the temperature at which photo-switching occurs needs to be increased to room temperature in order to realize devices for practical applications. In the present work we have focused on iron oxide

Separation of Complex Feed Streams of a Product by Layer Melt Crystallization

“…This is consistent with earlier results showing a modification of other NPs' magnetic properties induced by the grafting phosphonate‐group‐containing organic moieties 37, 38. In the case of NP@LC1, the modification of the anisotropy constant (as compared to that of NP@OA) can be explained either by the decrease of the carboxylate functions onto the surface (around 25%) or by a modification of the electronic environment near the surface due to the decrease of the ligand density 44…”

Smart Self‐Assemblies Based on a Surfactant‐Encapsulated Photoresponsive Polyoxometalate Complex

“…The prepared complex building block can form self‐assemblies in solution, and smart morphological changes between fibrous and spherical aggregates are successfully achieved for the first time through tuning the multiple supramolecular interactions by photoirradiation. As expected, the present photoresponsive hybrid system should possess: visible functional potentials in reversible magnetism adjustment of inorganic clusters through photoisomerization;11 optical property controlling of inorganic clusters through aggregate structure and morphology change; and aggregate morphology‐directed transition of the hydrophobic/hydrophilic property.…”

Magnetocurrent of Charge-Polarizable C60-Diphenylaminofluorene Monoadduct-Derived Magnetic Nanocomposites

“…Synthesis of magnetic γ-FeO x (1.0 < x < 1.5) nanoparticles was carried out by modifications of the literature procedures. , In a typical reaction, a mixture of FeCl 3 ·6H 2 O (2.70 g, 0.010 mol), FeCl 2 ·4H 2 O (1.98 g, 0.010 mol), sodium acetate (4.92 g, 0.060 mol, as a hydrolyzing agent), H 2 O (4.0 mL), and n -octylamine (7.3 mL, as a capping agent) in 1,2-propanediol (66 mL) was prepared and stirred under reflux at 150 °C for a period of 5.0 h. It was followed by precipitation upon the addition of 2-propanol to afford the product in a nearly quantitative yield. Sufficient binding of n -octylamine, even though as a weak capping agent, on the surface of iron oxide nanoparticles modified the surface compatibility to organic substances and rendered their moderate solubility in organic solvents, such as toluene and chloroform.…”