We present a systematic study of membrane structure (pore diameter and arrangement) in anodized aluminum oxide (AAO) layers obtained by anodization voltages 8−20 V in sulfuric and 15−40 V in oxalic acid electrolyte solutions. Anodization of bulk aluminum in sulfuric acid at 10 V potential was found to be optimal for production or ultrathin freestanding membranes with pore diameter in sub-20 nm range. The developed process with slow electrochemical reaction results in AAO membranes with thickness below 70 nm. The minimum required time for formation of continuous AAO membrane was determined and influence of electrolyte concentration on pore diameter in membrane after barrier layer removal analyzed. Finally, we demonstrate a method of membrane transfer onto a different surface and using it for masked deposition of dense nanoparticle arrays with diameters below 20 nm.

A multilayer system is formed by deposition of 10-35 nm thin Au or Ag film with 18-25 nm diameter holes on 75-280 nm thick layers of porous anodized aluminum oxide (AAO) supported by a bulk sheet aluminum. We present a detailed study of system parameters, which influence the optical response, including porosity, metal layer thickness and crystallographic orientation of Al substrate. The spectral properties are mainly governed by interference of reflections from the Al substrate and the thin metal film separated by the AAO layer. Enhanced plasmonic attenuation component near 650 nm for Au films with holes can be observed when interferometric anti-reflection condition is fulfilled close to this particular wavelength.

In this work, stoichiometric separate bismuth selenide (Bi 2 Se 3 ) nanoplates and continuous Bi 2 Se 3 coatings are synthesized on graphene substrate by catalystfree vapor-solid deposition method. The orientation of synthesized nanoplates relative to the substrate surface varies from heteroepitaxial (planar) to oriented under different angles (non-planar). The non-planar growth of the nanoplates was achieved for the first time by short-term carrier inert gas flow in certain temperature interval of the synthesis process. The crystallographic growth directions of non-planar nanoplates were determined from HRTEM images as well as estimated from the slope angles of non-planar nanoplates. Bi 2 Se 3 coatings consisting of combination of planar and non-planar nanoplates exhibit significantly enhanced in comparison with coating consisting of only planar coalescent Bi 2 Se 3 nanoplates thermoelectric properties. Demonstrated graphene/Bi 2 Se 3 /graphene devices may find applications in thermoelectric and photo-detection sensors.

This study demonstrates a new, robust, and accessible deposition technique of metal nanoparticle arrays (NPAs), which uses nanoporous anodic alumina (NAA) as a template for capillary force-assisted convective colloid (40, 60, and 80 nm diameter Au) assembly. The NPA density and nanoparticle size can be independently tuned by the anodization conditions and colloid synthesis protocols. This enables production of non-touching variable-density NPAs with controllable gaps in the 20–60 nm range. The NPA nearest neighbor center distance in the present study was fixed to 100 nm by the choice of anodization protocol. The obtained Au NPAs have the resonant scattering maxima in the visible spectral range, with a refractometric sensitivity, which can be tuned by the variation of the array density. The thickness of the NAA layer in an Aluminum-NAA-NPA multilayer system enables further tuning of the resonance frequency and optimization for use with specific molecules, e.g., to avoid absorption bands. Applicability of the mentioned multilayers for colorimetric refractive index (RI) sensing is demonstrated. Their use as Surface-Enhanced Raman Scattering (SERS) substrates is tested using hemoglobin as a biological probe molecule.

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