Extraordinary Effects in Quasi-Periodic Gold Nanocavities: Enhanced Transmission and Polarization Control of Cavity Modes

Plasmonic quasi-periodic structures are well-known to exhibit several surprising phenomena with respect to their periodic counterparts, due to their long-range order and higher rotational symmetry. Thanks to their specific geometrical arrangement, plasmonic quasi-crystals offer unique possibilities in tailoring the coupling and propagation of surface plasmons through their lattice, a scenario in which a plethora of fascinating phenomena can take place. In this paper we investigate the extraordinary transmission phenomenon occurring in specifically patterned Thue–Morse nanocavities, demonstrating noticeable enhanced transmission, directly revealed by near-field optical experiments, performed by means of a scanning near-field optical microscope (SNOM). SNOM further provides an intuitive picture of confined plasmon modes inside the nanocavities and confirms that localization of plasmon modes is based on size and depth of nanocavities, while cross talk between close cavities <i>via</i> propagating plasmons holds the polarization response of patterned quasi-crystals. Our performed numerical simulations are in good agreement with the experimental results. Thus, the control on cavity size and incident polarization can be used to alter the intensity and spatial properties of confined cavity modes in such structures, which can be exploited in order to design a plasmonic device with customized optical properties and desired functionalities, to be used for several applications in quantum plasmonics

Electropolymerized Highly Photoconductive Thin Films of Cyclopalladated and Cycloplatinated Complexes

International audienceThe complete characterization of novel electro-polymerizable organometallic complexes is presented. These are newly synthesized cyclometalated complexes of general formula (PPy)M(O∧N) n (H(PPy) = 2-phenylpyridine, M = Pd(II) or Pt(II), H(O∧N) n = Schiff base). Polymeric thin films have been obtained from these complexes by electro-polymerization of the triphenylamino group grafted onto the H(O∧N) n ancillary ligand. The redox behavior and the photoconductivity of both of the monomers (PPy)M(O∧N) n and the electropolymerized species have been investigated. The polymeric films of (PPy)M(O∧N) n have shown a very significant enhancement of photoconductivity when compared to their monomeric amorphous counterparts. The high stability of the obtained films strongly suggests that electropolymerization of cyclometalated complexes represents a viable deposition technique of quality thin films with improved photoconduction properties, hence opening the door to a new class of materials with suitable properties for optoelectronic applications