The controlled fabrication and geometry tunable optics of gold nanotube arrays

Abstract

Arrays of vertically aligned gold nanotubes are fabricated over several square centimetres which display a geometry tunable plasmonic extinction peak at visible wavelengths and at normal incidence. The fabrication method gives control over nanotube dimensions with inner core diameters of 15-30 nm, wall thicknesses of 5-15 nm and nanotube lengths of up to 300 nm. It is possible to tune the position of the extinction peak through the wavelength range 600-900 nm by varying the inner core diameter and wall thickness. The experimental data are in agreement with numerical modelling of the optical properties which further reveal highly localized and enhanced electric fields around the nanotubes. The tunable nature of the optical response exhibited by such structures could be important for various label-free sensing applications based on both refractive index sensing and surface-enhanced Raman scattering.

Surface plasmon and photonic mode propagation in gold nanotubes with varying wall thickness

“…Our experimental observations of the apparent red shift in the scattered-light spectra of AuNTs as a function of decreasing wall thicknesses are in qualitative agreement with simulation, in addition to prior literature on metallic tubular and core-shell structures. [5][6][7]10 To further elucidate the results presented here and help attribute the observed experimental red shifts to particular mode types, it is necessary to place the present work in the context of prior work on metallic nanotubes and core-shell systems, which has primarily been concerned with smaller inner-diameter nanostructures.…”

“…In the case of gold nanotubes (AuNTs), a pronounced red shift has been observed with decreasing wall thickness (WT) and increasing inner diameter (ID) (for WT ranging from 4-30 nm and ID ranging from 12-30 nm). [5][6][7] It is noteworthy that, while for tubular and core-shell structures an apparent red spectral shift is observed as a function of decreasing shell thickness, the opposite trend is observed in solid nanoparticle systems (spheres and rods), where a red shift and spectral broadening occur as a function of increasing size. 8 Therefore, core-shell and tubular systems can be considered unique in their plasmonic response relative to solid geometries.…”

“…[5][6][7] In that size regime, intrawall electric-field coupling (i.e. coupling between the inner and outer surface of the wall) is strong, and surface plasmon hybridization models can be applied (quasistatic regime).…”

Fabrication of Nano-Micro Hybrid Structures by Replication and Surface Treatment of Nanowires

“…Therefore, the physical separation is totally impossible and if it is tried to demold with even weak forces, the AAO filter cannot but break. According to previous studies, etching can be performed using various etchants (NaOH, KOH and H 3 PO 4 ) to remove the AAO filter [39][40][41][42]. We tested 2 mol of each etchant for the same etching time.…”

Ordered arrays of vertically aligned Au-nanotubes grafted with flocky Au/Ag-nanospikes based on electrodeposition and subsequent redox reaction

“…Previously, by using porous anodic aluminum oxide (AAO) as template, Au-NT arrays were achieved by complicated multi-step template replication and sacrificial pre-filled materials [1][2][3][4][5][6]. Therefore, developing a simple and effective approach to large-area Au-NT arrays is very important.…”