Controlling the Multiscale Topography of Anodized Aluminum Oxide Nanowire Structures for Surface-Enhanced Raman Scattering and Perfect Absorbers

Abstract

In this study, a plasmonically active substrate is developed with the aim of controlling the perfect absorption and manipulating its optical properties for application in SERS (in NIR regime) and colorimetry. Based on modified fabrication method of anodized aluminum oxide (AAO), the cost-effective selfaggregation technique is presented to fabricate unique topography of bone-fire-like funnel-shaped collapsed and vertically aligned nanowire structures. The length of the nanowire and the modification of surface topography induced by capillary force inside the nanowire are set to structural parameters, and the effect of their changes is closely studied. After deposition of 40 nm gold (Au) film on numerous AAO nanowire structures with different wire lengths and unique topography, the localized surface plasmon resonance excitation is generated, and also its application on reflection and SERS spectra have been shown quantitatively. The length of the wire and surface topography modification are identified as suitable parameters to tune the reflection/absorption (from <40 to >90%) as well as colorimetric effect. Finally, an optimized wire length of Au-coated AAO substrate in SERS sensing application with 3.92 × 10 5 order of enhancement of rhodamine 6G (R6G) Raman signal is demonstrated.

Enhancing the Efficiency of GaSb Photovoltaic Cell Using Thin-Film Multiscale Haze and Radiative Cooling

“…Second, the bending elastic force depends solely and inversely on the wire length. The shorter the wires, the higher the bending resistance . The effects of this bending force can be confirmed in Figure a,b for 1 and 5 μm wire length structures, respectively.…”

“…For a given length and size, with a constant gap between the wires, the surface tension forces are directly proportional to liquid− air surface tension and therefore to the contact angle of the liquid meniscus inside the pore. 38 Water has a higher surface tension and larger meniscus contact angle than PA. Because PA has lower-surface-tension forces, AAO nanowires collapse in broader domains relative to those in water drying processes. For a given lengths of nanowires, PA-dried AAO nanowire structures had lower packing density, larger cluster sizes, and larger numbers of nanoridges and nanovoids relative to waterdried samples.…”

“…First, the surface-tension-induced aggregation of the nanowire array arises from a disturbance in the drying process. For a given length and size, with a constant gap between the wires, the surface tension forces are directly proportional to liquid–air surface tension and therefore to the contact angle of the liquid meniscus inside the pore . Water has a higher surface tension and larger meniscus contact angle than PA. Because PA has lower-surface-tension forces, AAO nanowires collapse in broader domains relative to those in water drying processes.…”

“…Because of the increased path length of the incident light, absorption is enhanced at the active layer of the device. This thin haze film/membrane is advantageous because it uses less material and lowers the overall fabrication budget of cells. ,,− The fabrication of haze films satisfies the thickness requirement along with the economically favorable production of solar PV cells to produce omnidirectional broad-band antireflection properties. − …”

Effect of the Duty Cycle of Flower-like Silver Nanostructures Fabricated with a Lyotropic Liquid Crystal on the SERS Spectrum

“…Surface-enhanced Raman scattering (SERS) has been widely explored because it can be used to improve the sensitivity of Raman spectra [13][14][15]. Different nanostructures, such as nanowires [16][17][18], nanorods [19][20][21], nanospheres [22,23], and nanoflowers [24][25][26], are fabricated to obtain a high enhancement effect of the Raman spectra. Some SERS materials are prepared with chemical methods, such as the seed-mediated-growth method [19,27,28], the wet-chemical method [29], and the hydrothermal method [30].…”