Sharif Digital Repository

Plasmonic nanostructures offer great enhancement of the Raman signal due to the strong confinement of the electromagnetic field. Thus, they are considered as suitable candidates for surface enhanced Raman spectroscopy (SERS). In this work, we present an alternative fabrication route, called the glancing angle deposition (GLAD), for tunable fabrication of plasmonic self-organized Ag nanoparticle arrays aimed at SERS. Using the GLAD technique, the inter-particle distance within the arrays can be made as small as 1 nm. Moreover, the plasmonic resonance can be precisely tuned over the whole visible range. The GLAD method can be up-scaled; and when a transparent substrate is used, it enables... 

An analytic formulation revealing exact contribution of different factors affecting the interference interaction between eigenmodes of a scatterer is presented by utilizing our previously reported modal scattering power formula. For special case of arbitrary multilayer concentric and nonconcentric nanoshells, a recursive method for analytically calculating the T-matrix, and each of these factors is derived. Results for a three layer structure showing the conditions for constructive and destructive interference interactions are discussed in details. It is shown that the interference interaction can occur in the vicinity of the overlapping resonance frequencies of the two spatially overlapping... 

Chiral discrimination has always been a hot topic in chemical, food and pharmaceutical industries, especially when dealing with chiral drugs. Enantiomeric recognition not only leads to better understanding of the mechanism of molecular recognition in biological systems, but may further assist in developing useful molecular devices in biochemical and pharmaceutical studies. By emerging nanotechnology and exploiting nanomaterials in sensing applications, a great deal of attention has been given to the design of optical nanoprobes that are able to discriminate enantiomers of chiral analytes. This review explains how engineering nanoparticles (NPs) with desired physicochemical properties allows... 

Quasi-3D plasmonic nanostructures consisting of a metallic film perforated as an array of nanoholes, separated by a gap from a nanodisk array, are theoretically investigated under plane wave illumination with transverse electric and transverse magnetic polarizations. The results are compared with the results of a simple nanodisk array. A full discussion involving the couplings between plasmon resonance in nanodisks, surface plasmon polaritons on the interfaces of metallic film, and different diffractive grating orders that contribute in the couplings will be presented. The large difference between the plasmon behavior of the nanodisk array alone and nanodisk array in the presence of nanohole... 

The three-dimensional split-field finite-difference time-domain (SF-FDTD) method is combined with the totalfield- scattered-field method for injecting a plane wave. A formulation is derived for calculating the incidence transformed fields of SF-FDTD on a one-dimensional auxiliary grid. The resulting fields obtained in the scattered zone are used to calculate the far fields, based on a proposed fully time-domain near-to-far-field transformation. The far-field information is used to calculate the extinction cross section of the periodic structure under oblique incidence. To analyze metallic periodic structures, a formulation with a reduced number of variables is proposed based on the auxiliary... 

This paper is concerned with the investigation of an optical band-pass filter based on subwavelength surface plasmon polaritons. The transmission characteristics are numerically analyzed by the finite-difference time-domain method, and simulation results reveal that the structure has a band-pass filtering characteristic. The metal–insulator–metal plasmonic nanostructure is implemented by several vertical rectangular cavities across an optical waveguide. The metal and dielectric materials utilized for the realization of the filter are silver and air, respectively. Furthermore, the performance can be efficiently modified by tuning the geometric parameters such as the cavities’ length and width... 

Plasmonic nanostructures have emerging applications in solar cells, photodynamic therapies, surface-enhanced Raman scattering detection, and photocatalysis due to the excitation of localized surface plasmons. The exciting electric field resulting from the collective oscillation of free electrons is highly dependent on the dielectric medium, shape, size, composition, and configuration of plasmonic nanostructures. From an engineering perspective, one can tune the optimal properties in the desired applications of geometrical parameters such as the shape, size, and nanoparticles' configuration. Such optimization should be performed analytically (with exact solutions) or numerically (with... 

In this paper, we report a promising sunlight-driven screen-printed TiO2 porous nanorods (PNR) photoanode decorated with Au plasmonic nanostructures for photoelectrochemical (PEC) light-to-electricity conversion. Fabricated photoanodes were characterized using field emission scanning electron microscopy, high-resolution transmission electron microscopy, energy dispersive spectroscopy, X-Ray diffraction analysis, X-ray photoelectron spectroscopy, N2 adsorption-desorption isotherms, UV–vis spectroscopy and electrochemical impedance spectroscopy in detail. The Au-PNR-TiO2 photoanode demonstrates superior PEC activities both under simulated sunlight and visible light irradiation. Interestingly,...