Ultrathin Anodic Aluminum Oxide Membrane Research Articles

Large-scale plasmonic nanodisk array as a biosensing platform fabricated by transfer nanoprinting.

Surface plasmon resonance based on nanostructures has been a powerful analytical tool in rapid detection and analysis of biomolecules. However, the fabrication of nanostructure sensors, such as electron beam lithography and focused ion beam milling, has inherent defects as manufacturing cost, complex process flow, and small fabrication area. In this paper, using the transfer nanoprinting approach based on an ultrathin anodic aluminum oxide membrane, a centimeter-scale ordered periodic Ag-ZnS bilayer nanodisk on Au film with a low cost and simple process is fabricated. A surface plasmon polariton Bloch mode from nanodisk arrays is experimentally demonstrated at normal incident of light. The plasmonic platform exhibits an ideal refractive index bulk sensitivity of up to 438nm/RIU. Furthermore, by using a polyelectrolyte bilayer with well-defined thickness, the surface sensitivity of the biosensing platform is also investigated. The large-scale plasmonic bilayer nanoparticle biosensing platform has broad application prospects in development of low-cost and high-performance biosensing chips.

Large‐Scale Plasmonic Nanodisk Structures for a High Sensitivity Biosensing Platform Fabricated by Transfer Nanoprinting

AbstractSurface plasmon resonance in plasmonic nanostructures has become a powerful analytical tool in ultrasensitive label‐free biomolecule sensing. However, the fabrication of plasmonic nanostructure sensors relies on lithography‐based top‐down nanofabrication approaches, which have inherent shortcomings, such as high manufacturing cost, time‐consuming fabrication, and a small fabrication footprint. In particular, the small footprint of fabricated plasmonic nanostructures has significantly restrained the study of their angle‐dependent sensitivity. Here, a centimeter‐scale, high sensitivity sensing platform with low cost and high yield is experimentally demonstrated, fabricated through a transfer nanoprinting approach based on an ultrathin anodic aluminum oxide membrane. Two angle‐dependent resonant modes from the plasmonic nanodisk structure are observed at nonzero incidence angles. The dependence of the bulk sensitivity and surface sensitivity on the incidence angle under these two modes is systematically investigated. By functionalizing the plasmonic nanostructure, monitoring of binding of protein at dilute concentration is performed in real time at different incidence angles. The specific label‐free lowest detection limit is found to be 1.8 nanomolar for the longer wavelength resonant mode at a 10° incidence angle. This plasmonic nanostructure sensing platform should hold promise in the development of low cost and high throughput biosensing chips.

Size correlation of optical and SERS properties for highly ordered Au nanocone arrays with sub-100 nm feature size

Using ultrathin anodic aluminum oxide membranes as evaporation masks, highly ordered Au nanocone arrays with sub-100 nm feature size were fabricated on glass substrates. The size of Au nanocones was adjusted by the easily controllable nanopores’ dimension. Influences of Au nanocone size on the optical property and SERS activity were characterized by extinction and Raman spectra, respectively. For one thing, the spectral position of plasmon resonances was seen to slightly blue-shift with increasing the nanocone size, which coincided well with the result of finite-difference-time-domain simulation. For another, glass substrates patterned by Au nanocone arrays exhibited a high surface enhanced Raman scattering sensitivity to Rhodamine 6G. Compared with the bulk sample, the estimated enhancement factor was boosted from 8 × 106 to 1.79 × 107 as the diameter of Au nanocone increased from 36 to 77 nm. Such highly ordered nanocone arrays with tunable and uniform size have great potential for various optical or spectrographic applications.

Ultrathin AAO Membrane as a Generic Template for Sub-100 nm Nanostructure Fabrication

Anodic aluminum oxide (AAO) templates are emerging as a platform for simple, cost-effective, high-throughput top-down nanofabrication of regular arrays of nanostructures. Thus far, however, AAO pattern transfer has largely been restricted to smooth and chemically inert surfaces, mostly Silicon substrates. Here, we present a more generalizable strategy for preparing free-standing through-hole ultrathin alumina membranes (UTAMs) and transferring them to both smooth and rough substrates, thereby enabling the fabrication of centimeter-scale arrays of nanostructures with sub-100 nm feature diameters on almost arbitrary substrates. To validate the utility of our procedures, we transferred UTAMs to surfaces relevant for photocatalytic applications and prepared plasmonic photocathodes consisting of dense arrays of size-controlled sub-100 nm Au and Ni nanodots on top of chemically noninert NiOx thin films. To demonstrate the functionality of the fabricated structures, we used a plasmonic photocathode consisting of...

Synthesis of zinc oxide nanotubes within ultrathin anodic aluminum oxide membrane by sol–gel method

In this paper we report a simple method that enables the easy fabrication of ultrathin porous anodic aluminum oxide (AAO) membranes from two-step anodization in oxalic acid solution. ZnO nanotubes have been synthesized by injecting sol–gel into the pores of the ultrathin AAO membrane. The structures and morphologies of the ultrathin AAO membrane and ZnO nanotubes were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscope. The thickness of the as-prepared AAO membranes is about 1μm with highly ordered pores inside, and the ZnO nanotubes are straight with uniform thickness along the length and with diameter equal to those of nanopores.

Plasmon resonance properties of silver-patterned glass substrates fabricated by anodic alumina oxide templates

Ultra-thin anodic aluminum oxide membranes were prepared and served as deposition masks for fabrication of uniformly sized Ag nanodots with different aspect ratios on glass substrates. The surface plasmon resonance (SPR) properties of the supported Ag nanodots were investigated and compared with the predictions of the generalized Maxwell–Garnett theory. By modeling the nanodots as spheroids without adjusting their real geometrical parameters input to the calculation, the resulting theoretical SPR wavelengths are in good agreement with measured extinction peaks. The discrepancy between the theoretical and experimental plasmon resonance peak maxima is within 10 nm for the nanodots with an aspect ratio of less than 1.5. Although this wavelength discrepancy becomes large as the aspect ratio is increased, it is kept at approximately 35 nm for the nanodots with an aspect ratio of 2.44.

Individual switching of film-based nanoscale epitaxial ferroelectric capacitors

We have investigated the individual switching of nanoscale capacitors by piezoresponse force microscopy. Nanoscale epitaxial ferroelectric capacitors with terabyte per inch square equivalent density were fabricated by the deposition of top electrodes onto a pulsed laser deposited lead zirconate titanate thin film by electron beam evaporation through ultrathin anodic aluminum oxide membrane stencil masks. Using bias pulses, the nanoscale capacitors were uniformly switched and proved to be individually addressable. These film-based nanoscale capacitors might be a feasible alternative for high-density mass storage memory applications with near terabyte per inch square density due to the absence of any cross-talk effects.

Vortex Polarization States in Nanoscale Ferroelectric Arrays

Two-dimensional arrays of ferroelectric lead zirconate titanate (PZT) nanodots were fabricated using pulsed laser deposition through ultrathin anodic aluminum oxide membrane stencil masks. The static distribution of polarization configurations was investigated using in- and out-of-plane piezoresponse force microscopy (PFM). The observed presence of an in-plane polarization component in nominally (001) oriented PZT suggests the existence of a significant deviation from the regular tetragonal structure that allows the formation of complex core-polarization states. Core-polarization states may indicate the presence of quasi-toroidal polarization ordering. The experimental results are compared with a theoretical model to determine the fingerprint of a vortex polarization state in PFM.