The excitation of surface plasmons in metallic nanoparticles induces optical properties hardly achievable in other optical materials, yielding a wide range of applications in many fields. This review presents an overview of surface plasmons in metallic nanoparticles. The concept of surface plasmons in nanoparticles is qualitatively described using a comparison with simple linear oscillators. The mathematical models to carry on calculations on surface plasmons are presented as well as the most common approximations. The different parameters governing the features of surface plasmons and their effect on the optical properties of the materials are reviewed. Finally, applications of surface plasmons in different fields as biomedicine, energy, environment protection and information technology are revised.

Local heating can be produced by iron oxide nanoparticles (IONPs) when exposed to an alternating magnetic field (AMF). To measure the temperature profile at the nanoparticle surface with a subnanometer resolution, here we present a molecular temperature probe based on the thermal decomposition of a thermo-sensitive molecule, namely, azobis[N-(2-carboxyethyl)-2-methylpropionamidine]. Fluoresceineamine (FA) was bound to the azo molecule at the IONP surface functionalized with poly(ethylene glycol) (PEG) spacers of different molecular weights. Significant local heating, with a temperature increase up to 45 °C, was found at distances below 0.5 nm from the surface of the nanoparticle, which decays exponentially with increasing distance. Furthermore, the temperature increase was found to scale linearly with the applied field at all distances. We implemented these findings in an AMF-triggered drug release system in which doxorubicin was covalently linked at different distances from the IONP surface bearing the same thermo-labile azo molecule. We demonstrated the AMF triggered distance-dependent release of the drug in a cytotoxicity assay on KB cancer cells.

In this work it is experimentally shown that capping ZnO nanoparticles with organic molecules leads to the appearance of magnetism at room temperature.The bonds between the molecules and the Zn atoms at the nanoparticle surface alter its electronic structure (as XANES and photoluminescence spectra demonstrate) arising magnetic moments with values that depend on the nature of the molecule. This result points out the possibility to observe magnetism at nanoscale in semiconductors without typical magnetic atoms (transition metals and rare earths).

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Colloidal semiconductor-magnetic hybrid nanocrystals with topologically controlled composition are fabricated by heterogeneous nucleation of spherical epsilon-Co domains onto anatase TiO2 nanorods. The latter can be selectively decorated at either their tips or at multiple locations along their longitudinal sidewalls, forming lattice-matched heterointerfaces regardless of the metal deposition sites. The possibility of switching between either heterostructure growth modes arises from the facet-dependent chemical reactivity of the oxide seeds, which is governed mainly by selective adhesion of the surfactants rather than by small differences in misfit-induced interfacial strain at the relevant junction points.

Monodisperse cubic spinet iron oxide magnetic nanoparticles with variable sizes were prepared following a multi-injection seeded-growth approach. As expected from such a well-known synthetic route, all samples were characterized by narrow size distributions, and showed excellent stability in both organic and aqueous media without the presence of aggregates, thus becoming ideal candidates for the study of their hyperthermia performance. Specific Loss Power measurements indicated low heating powers for all samples without a maximum for any specific size, contrary to what theory predicts. The magnetic study showed the formation of size-dependent nonsaturated magnetic regions, which enlarged with the particle size, evidencing a clear discrepancy between the crystal size and the effective magnetic volume. Strain map analysis of high resolution transmission electron micrographs indicated the presence of highly strained crystal areas even if nanoparticles were monocrystalline. The origin of the crystal strain was found to be strictly correlated with the seeded-growth synthetic procedure used for the preparation of the nanoparticles, which turned out to alter their magnetic structure by creating antiphase boundaries. Considering the calculated effective magnetic volumes and their magnetic dispersions in each sample, a reasonable agreement between hyperthermia experiments and theory was obtained

It has been recently reported that some non-magnetic materials in bulk state, exhibit magnetic behavior at the nanscale due to surface and size effects. The experimental observation of these effects is based on the measurement of very small magnetic signals. Thus, some spurious effects that are not critical for bulk materials with large magnetic signals may become important when measuring small signals (typically below 0.0001 emu). Here, we summarize some sources of these small magnetic signals that should be considered when studying this new nanomagnetismComment: 16 pages, 10 figure

Dumbbell‐like Au‐Fe3O4 nanoparticles and their single‐component counterparts, Au and Fe3O4, were compared regarding their H2O2 reduction capability. The Au‐Fe3O4 nanoparticles are catalytically more active, which is attributed to polarization effects from Au to Fe3O4. This activity can be further tuned by the size of the nanoparticles.