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Nanotherapies are gaining increased interest for the treatment diverse diseases, particularly cancer, since they target the affected area directly, presenting higher efficacy and reduced side effects than traditional therapies. A promising nanotherapy approach is hyperthermia, where the nanoparticle can induce a local temperature increase by an external stimulus in the sick tissue to selectively kill the malignant cells. Among the diverse hyperthermia methods, photothermia is based on the absorption of light by the nanoparticles and further conversion into heat. Within the very wide range of nanostructured photothermal agents, iron oxides offer remarkable features since they are already approved by the FDA/EMA for various biomedical applications, they are biodegradable, easily manipulated using magnetic fields and can be imaged by diverse techniques. Here, we summarize the advantages of using the second biological window, both from the perspective of the skin and the optical properties of iron oxides. Further, we review the photothermal performance of iron oxide nanoparticles in the first, second and third biological windows. Overall, the results show that, for different types of iron oxide nanoparticles (Fe 3 O 4 , γ -Fe 2 O 3 , wüstite-FeO), both the heating capacity (i.e., induced temperature increase) and the photothermal conversion efficiency, η , vary in a complex way with the light wavelength, depending critically on the measurement conditions and physiochemical properties of the materials. Despite the spread in the reported photothermal properties of iron oxides, Fe 3 O 4 particles tend to perform better than their γ -Fe 2 O 3 counterparts, particularly in the second biological window. Interestingly, FeO, which has not been exploited so far from a photothermal perspective, shows very appealing absorption properties. Our preliminary studies using FeO/Fe 3 O 4 core/shell nanoparticles evidence that they have excellent photothermal properties, outperforming Fe 3 O 4 in both first and second biological windows. Finally, some applications beyond cancer treatment of iron oxide nanoparticles, exploiting the enhanced properties in the second spectral window, are discussed. [ABSTRACT FROM AUTHOR]

The physicochemical properties of spinel oxide magnetic nanoparticles depend critically on both their size and shape. In particular, spinel oxide nanocrystals with cubic morphology have shown superior properties in comparison to their spherical counterparts in a variety of fields, like, for example, biomedicine. Therefore, having an accurate control over the nanoparticle shape and size, while preserving the crystallinity, becomes crucial for many applications. However, despite the increasing interest in spinel oxide nanocubes there are relatively few studies on this morphology due to the difficulty to synthesize perfectly defined cubic nanostructures, especially below 20 nm. Here we present a rationally designed synthesis pathway based on the thermal decomposition of iron(III) acetylacetonate to obtain high quality nanocubes over a wide range of sizes. This pathway enables the synthesis of monodisperse Fe 3 O 4 nanocubes with edge length in the 9-80 nm range, with excellent cubic morphology and high crystallinity by only minor adjustments in the synthesis parameters. The accurate size control provides evidence that even 1-2 nm size variations can be critical in determining the functional properties, for example, for improved nuclear magnetic resonance T 2 contrast or enhanced magnetic hyperthermia. The rationale behind the changes introduced in the synthesis procedure (e.g., the use of three solvents or adding Na-oleate) is carefully discussed. The versatility of this synthesis route is demonstrated by expanding its capability to grow other spinel oxides such as Co-ferrites, Mn-ferrites, and Mn 3 O 4 of different sizes. The simplicity and adaptability of this synthesis scheme may ease the development of complex oxide nanocubes for a wide variety of applications.