Plasmon enhanced light absorption in aluminium@Hematite core shell hybrid nanocylinders: the critical role of length

Abstract

The light absorption as well as the near field enhancements properties of Al@α-Fe2O3 core shell hybrid nanocylinders (HNs) have been systematically studied by means of Discrete Dipole Approximation simulations. The Al@α-Fe2O3 HNs consist of a right circular cylinder Al core, wrapped by a circular section of an α-Fe2O3 shell, both having the same finite length L. A general and useful methodology has been implemented to assess separately the partial contributions to the absorption spectrum of each component of the Al@α-Fe2O3 HN. The employed methodology can be applied not only to those HNs studied here but also to any other nanostructure with arbitrary geometry and several components providing relevant information not accessible through standard spectroscopic techniques. The absorption spectra have been employed to calculate the absorbed photon flux ϕ within the α-Fe2O3 shell. According to the HN size, plasmon enhanced light absorption in the α-Fe2O3 shell of the Al@α-Fe2O3 HNs is evidenced, which is attributed to a plasmon-induced energy transfer mechanism based on near field enhancements. The effect of the HN length on the absorbed photon flux ϕ is an important issue that has not been addressed yet, as only infinitely long HN has been considered in previous studies. It is demonstrated that the HN length L has a crucial influence on the absorbed photon flux ϕ, as it is the main structural parameter that allows us to tune the dipole plasmon resonance of the Al core into the visible region. Furthermore, it is shown that Al cores lead to larger ϕ values than the typical plasmonic metals Ag and Au. The results presented in this work point out that the HN length should be explicitly taken into account for an optimum design of core shell hybrid cylindrical nanostructures with enhanced or improved photoactive properties.