Nanoholes

This review will discuss the possibility to control and improve the reactivity of Titania by design of new tailored nano-architecture. Specifically, analyses quasi-ID Ti02 nanostructures, e.g. nanorods, nanowires and nanofibres, nanotubes and nanopillars. 2D Titania nanostructures, e.g. columnar-type films, ordered arrays of nanotubes or nano-rods/-wires, nanobowl array, nanomembranes (called also nanohole array) and nanosponge, and Ti-based ordered mesoporous matrices will be instead discussed in a consecutive review paper. 

Alumina nanotubes have been prepared by the anodic oxidation of aluminum [41] the resulting tubes have one-dimensional channels with uniform diameters of 5nm and lengths of 50-100 nm. An alumina membrane with a highly ordered nanohole array in 50-100 nm diameter has also been synthesized by long-period anodization thus these local alumina nanotubes have been tried as a template for metal nanowire formation. 

A variety of nanomaterials have been synthesized by many researchers using anodic aluminum oxide film as either a template or a host material e.g., magnetic recording media (13,14), optical devices (15-18), metal nanohole arrays (19), and nanotubes or nanofibers of polymer, metal and metal oxide (20-24). No one, however, had tried to use anodic aluminum oxide film to produce carbon nanotubes before Kyotani et al. (9,12), Parthasarathy et al. (10) and Che et al. (25) prepared carbon tubes by either the pyrolytic carbon deposition on the film or the carbonization of organic polymer in the pore of the film. The following section describes the details of the template method for carbon nanotube production. 

Iwasaki, T., Motoi, T., and Den, T., Mutiwalled carbon nanotubes growth in anodic alumina nanoholes. Appl. Phys Lett 75,2044 (1999). 

H. Masuda and K. Fukuda, Ordered metal nanohole arrays made by a two-step replication of honeycomb structures of anodic alumina, Science 268 1466-1468 (1995). 

Nanohole Arrays in Metal Films as Integrated Chemical Sensors and Biosensors... 

Keywords Nanohole array Surface plasmon resonance Optical sensing Chemical sensing Biosensing Microfluidic Nanofluidic Extraordinary optical transmission... 

The arrays of nanoholes on Au films are generally fabricated using focused ion beam (FIB) milling. The geometric parameters of the arrays, such as hole diameter and periodicity (distance between the holes), can be controlled with nanometric... 

Fig. 5 Scanning electron micrographs of an array of nanoholes on gold films in two magnifications. Two hundred nanometer hole diameter and 550 nm of periodicity...

Fig. 6 EOT from two arrays of nanoholes with different periodicities (indicated). Hole diameter is 200 nm...

For periodic metallic nanostrucmres, the phase-matching condition for SP resonance coincides with the Bragg resonances of the grating. At normal incidence, the wavelength of SPP resonance (Xspp) for a square array of nanoholes can be calculated using [12,27] ... 

The sensing demonstration described above was realized in normal transmission, which is much simpler than the typical angled reflection arrangement employed in the commercial SPR systems. This transmission setup is more compatible to the lab-on-chip concept, since miniaturized light sources, such as LEDs, and photodiodes (or a CCD) can sandwich the sensing areas of the array of nanoholes, yielding a compact package. 

Figure 8 shows the surface-enhanced resonance Raman scattering (SERRS) spectra of oxazine 720 adsorbed on arrays of nanoholes in gold films with different... 

Fluorescence-based measurements are already very sensitive and widely used in bio-medical analysis. However, the metallic nanostructures provide further improvement on the sensitivity and limit of detections through the enhancement of the local field. Therefore, a large number of researchers are dedicated to developing substrates for SEFS [46-52]. The effect of the geometrical parameter of the nanostructure on the efficiency of the SEFS is well illustrated in Fig. 9. In this case, the SEFS enhancement factor (SEFS enhancement factor) is plotted against the periodicity of the arrays of nanoholes in gold films. The experiments were realized by spin-coating the arrays of nanoholes with a polystyrene film doped with the oxazine 720 [48]. 

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