This review provides a general overview of recent applications of magnetic nanoparticles for controlled radiofrequency (RF) heating in catalytic synthesis, mass transfer enhancement in laminar fl ow and magnetic separation. By directly delivering RF energy to magnetic materials, issues such as long heating periods and energy losses can be minimized. The main mechanisms of RF heating are briefl y reviewed. The effect of nanoparticles size, shape and composition on the effi ciency of RF heating is discussed. RF energy has been shown to be effective in many applications, however, it is still not used in chemicals due to high equipment costs.

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We present a simple method for direct and solvent-free formation of amides from carboxylic acids and amines using radiofrequency heating. The direct energy coupling of the AC magnetic field via nickel ferrite magnetic nanoparticles enables fast and controllable heating, as well as enabling facile work-up via magnetic separation.

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AC magnetic heating of superparamagnetic Co and Fe nanoparticles for application in hyperthermia was measured to find a size of nanoparticles that would result in an optimal heating for given amplitude and frequency of ac externally applied magnetic field. To measure it, a custom-made power supply connected to a 20-turn insulated copper coil in the shape of a spiral solenoid cooled with water was used. A fiber-optic temperature sensor has been used to measure the temperature with an accuracy of 0.0001 K. The magnetic field with magnitude of 20.6 μT and a frequency of oscillation equal to 348 kHz was generated inside the coil to heat magnetic nanoparticles. The maximum specific power loss or the highest heating rate for Co magnetic nanoparticles was achieved for nanoparticles of 8.2 nm in diameter. The maximum heating rate for coated Fe was found for nanoparticles with diameter of 18.61 nm.

Direct Amide Formation Using Radiofrequency Heating -The direct and solvent--free formation of amides from carboxylic acids and amines using radiofrequency heating is reported. The direct energy coupling of the AC magnetic field via nickel ferrite magnetic nanoparticles enables fast and controllable heating, as well as easy work up via magnetic separation. -(HOULDING, T. K.; TCHABANENKO, K.; RAHMAN, M. T.; REBROV*, E. V.; Org. Biomol. Chem. 11 (2013) 25, 4171-4177, http://dx.doi.org/10.1039/c2ob26930a ; Sch. Chem. Chem. Eng., Queen's Univ., Belfast BT9 5AG, UK; Eng.) -S. Karsten 42-035