The electro-magnetic field generated within and around dissipative nano-structures upon light radiation is intimately associated to the formation of localized heat sources. In turn, this phenomenon determines localized temperature variations, effect which can be exploited for applications such as photocatalysis , nanochemistry  or sensor devices .
Here we show how the geometrical characteristics of plasmonic nano-structures can indeed be used to modulate the temperature response. The idea is that when metallic structures interact with an electromagnetic field they heat up due to Joule effect. The corresponding temperature variation modifies the optical response of the structure [4,5] and thus its heating process. The key finding is that, depending on the structures geometry, absorption efficiency can either increase or decrease with temperature. Since absorption relates to the thermal energy dissipation and thus to temperature increase, the mechanism leads to positive or negative loops. Consequently, not only an error would be made by neglecting the role of temperature, but it would be not even possible to know, a priori, if the error is towards higher or lower absorption values.
Our model can be utilized to study opto-thermal phenomena when high temperature or high intensity sources are employed.
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The proper exploitation of the plasmon resonance typical of metallic nanoparticles can allow for the confinement of the electromagnetic field in nanometric volumes, thus creating the so called "hot spots". These nanometric volumes are characterized by high field, remarkably useful characteristic for a huge variety of applications in photonics and optics.
The most commonly employed plasmonic metals, Au and Ag, yield resonances only reaching up to the near-UV electromagnetic range, in fact stretching upwards the energy of plasmon resonances requires the use of different materials.
Deep-ultraviolet plasmon resonances were indeed predicted exploiting one of the cheapest and most abundant materials available on earth. Aluminium holds the promise of a broadly-tuneable plasmonic response, theoretically extending far into the deep-ultraviolet (DUV). Complex fabrication issues, including the strong Al reactivity, have however stood in the way of achieving this ultimate DUV response.
We report the successful realization of 2-dimensional arrays of ultrafine aluminium nanoparticles that exhibit a remarkable plasmonic response up to the DUV electromagnetic range. Careful nanofabrication allowed to maintain the mean NP size below 20 nm, preserving a purely-metallic core. These systems exhibit a striking high-energy plasmon resonance up to 6.8 eV photon energy, and preserve their DUV plasmon response when exposed to atmosphere [1,2]. These observations pave the way to the full exploitation of aluminium plasmonic tunability, hence extending the numerous applications of plasmonics to the high-energy side of the spectral range.
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Metallic nanostructures can be utilized as heat nano-sources which can find application in different areas such as photocatalysis, nanochemistry or sensor devices. Here we show how the optical response of plasmonic structures is affected by the increase of temperature. In particular we apply a temperature dependent dielectric function model to different nanoparticles finding that the optical responses are strongly dependent on shape and aspect-ratio. The idea is that when metallic structures interact with an electromagnetic field they heat up due to Joule effect. The corresponding temperature increase modifies the optical response of the particle and thus the heating process. The key finding is that, depending on the structures geometry, absorption efficiency can either increase or decrease with temperature. Since absorption relates to thermal energy dissipation and thus to temperature increase, the mechanism leads to positive or negative loops. Consequently, not only an error would be made by neglecting temperature but it would be not even possible to know, a priori, if the error is towards higher or lower values.
Heating processes in plasmonics are essential every time the interaction with electromagnetic fields induces dissipation within metallic nanostructures. In particular the capability to predict the final temperature reached by a system (e.g. an ensemble of nanoparticles within a host medium) can be crucial when dealing with electronic, medical or chemical applications. Here we present a dispersive model of the dielectric function of a metallic medium which depends on temperature. Since temperature, in turn, depends on the intensity of the electromagnetic source and on the optical response of the medium itself, the model expresses non-linearity features. The model, which does not require any fitting parameter, can be utilized whenever the impact of temperature on the optical response of a system needs to be clarified and/ or when non-linearities might play a major role.
The ability to confine light in small volumes, associated to low background signals, is an important technological
achievement for a number of disciplines such as biology or electronics. In fact, decoupling the source position from the
sample area allows an unprecedented sensitivity which can be exploited in different systems. The most direct
implications are however related to either Surface Enhanced Raman Scattering (SERS) or Tip Enhanced Raman
Scattering (TERS). Furthermore, while the combination with super-hydrophobic patterns can overcome the typical
diffusion limit of sensors, focused surface plasmons decaying into hot electrons can be exploited to study the electronic
properties of the sample by means of a Schottky junction. Within this paper these techniques will be briefly described
and the key role played by both surface and localized plasmons will be highlighted.