δ-FeOOH: a superparamagnetic material for controlled heat release under AC magnetic field

Experimental evidences on its in vitro use reveal that delta-FeOOH is a material that release-controlled amount of heat if placed under an AC magnetic field. delta-FeOOH nanoparticles were prepared by precipitating Fe(OH)(2) in alkaline solution followed by fast oxidation with H2O2. XRD and Fe-57 Mossbauer spectroscopy data confirmed that delta-FeOOH is indeed the only iron-bearing compound in the produced sample. TEM images evidence that the averaged particle sizes for this delta-FeOOH sample is 23 nm. Magnetization measurements indicate that these delta-FeOOH particles behave superparamagnetically at 300 K; its saturation magnetization was found to be 13.2 emu g(-1); the coercivity and the remnant magnetization were zero at 300 K. The specific absorption rate values at 225 kHz were 2.1, 6.2, and 34.2 W g(-1), under 38, 64, and 112 mT, respectively. The release rate of heat can be directly controlled by changing the mass of delta-FeOOH nanoparticles. In view of these findings, the so-prepared delta-FeOOH is a real alternative to be further tested as a material for medical practices in therapies involving magnetic hyperthermia as in clinical oncology.