(a) Sketch of the optical setup used to perform IRRAS spectroscopy: the incoming IR radiation, reflected by a parabolic mirror (FM) and two plane mirrors (PM), is focused by an elliptic mirror (EM) on the nanorod platform positioned in the upper part of the sample compartment. The radiation impinges with a grazing angle of 80° and it is linearly polarized by a wire-grid polarizer (the directions of E vector for both TE- and TM-polarized light are indicated by arrows in Figure). The outgoing IR radiation is focused finally onto an MCT photovoltaic detector through a specular mirror system. (b) Representative SEM image of the nanorod platform with the direction of E vector drawn when it is perpendicular or parallel to the main axis of nanorods, depending on the relative in-plane orientation of our sample and the E polarization. (c) IRRAS reflectance spectra of our sample when the main axis of nanorods is parallel to E using TE- (blue curve) and TM-polarized light (orange curve) and when the main axis of nanorods is perpendicular to E (pink curve and green curve for TE- and TM-polarized light, respectively).