Tuning the Optical Properties of Hyperbolic Metamaterials by Controlling the Volume Fraction of Metallic Nanorods

Uniform arrays of gold nanoelectrodes with tuneable recess depth

Nanoelectrode arrays are much in demand in electroanalytical chemistry, electrocatalysis, and bioelectrochemistry. One of the promising approaches for the preparation of such systems is templated electrodeposition. In the present study, porous anodic alumina templates are used to prepare Au nanoelectrode arrays. Multistage electrodeposition is proposed for the formation of recessed electrodes with the ability to tune the distance between the surface of the porous template and the top surface of the nanoelectrodes. A set of complementary techniques, including chronoamperometry, coulometry, and scanning electron microscopy, are used to characterize the nanoelectrode arrays. The number of active nanoelectrodes is experimentally measured. The pathways to further improve the recessed nanoelectrode arrays based on anodic alumina templates are discussed.

Magneto-optical effects in hyperbolic metamaterials based on ordered arrays of bisegmented gold/nickel nanorods

Hyperbolic metamaterials (HMM) based on multilayered metal/dielectric films or ordered arrays of metal nanorods in a dielectric matrix are extremely attractive optical materials for manipulating over the parameters of the light flow. One of the most promising tools for tuning the optical properties of metamaterialsin situis the application of an external magnetic field. However, for the case of HMM based on the ordered arrays of magneto-plasmonic nanostructures, this effect has not been clearly demonstrated until now. In this paper, we present the results of synthesis of HMM based on the highly-ordered arrays of bisegmented Au/Ni nanorods in porous anodic alumina templates and a detailed study of their optical and magneto-optical properties. Distinct enhancement of the magneto-optical (MO) effects along with their sign reversal is observed in the spectral vicinity of epsilon-near-zero and epsilon-near-pole spectral regions. The underlying mechanism is the amplification of the MO polarization plane rotation initiated by Ni segments followed by the light propagation in a strongly birefringent HMM. This stays in agreement with the phenomenological description and relevant numerical calculations.

The toolbox of porous anodic aluminum oxide–based nanocomposites: from preparation to application

Anodic aluminum oxide (AAO) templates have been intensively investigated during the past decades and have meanwhile been widely applied through both sacrificial and non-sacrificial pathways. In numerous non-sacrificial applications, the AAO membrane is maintained as part of the obtained composite materials; hence, the template structure and topography determine to a great extent the potential applications. Through-hole isotropic AAO features nanochannels that promote transfer of matter, while anisotropic AAO with barrier layer exhibits nanocavities suitable as independent and homogenous containers. By combining the two kinds of AAO membranes with diverse organic and inorganic materials through physical interactions or chemical bonds, AAO composites are designed and applied in versatile fields such as catalysis, drug release platform, separation membrane, optical appliances, sensors, cell culture, energy, and electronic devices. Therefore, within this review, a perspective on exhilarating prospect for complementary advancement on AAO composites both in preparation and application is provided.