Template Deposition of Metals

Abstract

Template synthesis is a relatively simple and easy procedure which has made the fabrication of rather sophisticated nanomaterials accessible to almost any laboratory. Template synthesis requires access to instrumentation capable of metal sputtering and electrochemical deposition. The characterization of the fabricated nanostructures can be done using instrumental techniques including spectrophotometry, voltammetry, optical microscopy, atomic force microscopy, and electronic microscopies (scanning electron microscopy (SEM) and transmission electron microscopy (TEM)).The method is based on the simple but effective idea that the pores of a host material can be used as a template to direct the growth of new materials. Historically, template synthesis was introduced by Possin (1) and refined by Williams and Giordano (2) who prepared different metallic nanowires with widths as small as 10 nm within the pores of etched nuclear damaged tracks in mica. It was further developed by Martin's group (3-5) and followed by others (6) with the number of examples and applications (7) continually increasing. The nanoporous membranes usually employed as templates are alumina or track-etched polymeric membranes which are widely used as ultrafiltration membranes. Recently, metal nanostructures have also been obtained using the pores created by self-assembly in block copolymer structures under the influence of electric fields and high temperatures (8, 9).The first part of this section focuses on the main characteristics and fabrication techniques used for obtaining templating membranes and depositing metal nanostructures by suitable electroless and electrochemical procedures. Methods such as sol-gel (10-12) or chemical vapor deposition (10, 13), which have been used primarily for the template deposition of carbon, oxides, or semiconducting-based materials, will not be considered here in detail. The second part of the section focuses on the electrochemical properties of the fabricated nanomaterials with emphasis on the characteristics and applications of nanoelectrode ensembles (NEEs). Templating membranes 16.2.2

Electrochemical Behavior of Nanoelectrode Ensembles in the Ionic Liquid [BMIm][BF4]

“…From the value of experimental plateau currents and Equations 1 and 2, the recession depth can be evaluated in the order of 30 -50 nm. This recession can be possibly originated during the cleaning of the outer surface of the NEE during the preparation of the ensemble [22].…”

Nanoelectrode ensembles as recognition platform for electrochemical immunosensors

“…Templating membranes were polycarbonate track-etched membranes (SPI-pore, 47 mm filter diameter, 6 m thickness) with a nominal pore diameter of 30 nm, average pore density 6 × 10 8 pore/cm 2 , coated by the producer with polyvinylpyrrolidone. The final NEEs were assembled as previously described (Ugo and Moretto, 2007). A hole punched in an insulating layer of plastics (Monokote by Topflite) determined the A geom , typically 0.07 cm 2 .…”

“…NEEs were prepared by template gold electroless deposition (Ugo and Moretto, 2007), using recently described updates (De Leo et al, 2007a,b). Templating membranes were polycarbonate track-etched membranes (SPI-pore, 47 mm filter diameter, 6 m thickness) with a nominal pore diameter of 30 nm, average pore density 6 × 10 8 pore/cm 2 , coated by the producer with polyvinylpyrrolidone.…”

Modification of nanoelectrode ensembles by thiols and disulfides to prevent non specific adsorption of proteins

“…Handy NEEs were assembled as previously described [13]. Briefly: a small piece (approximately 8 mm × 8 mm) of golden membrane was attached to a suitable conductive substrate; the gold layer on the outer face of the membrane was removed by peeling with scotch tape (so that only the head of the gold nanowires inside the pores will be exposed to the sample solution); all the surface of the NEE, apart a hole of 3 mm diameter (which defines the geometric area of the ensemble, A geom = 0.07 cm 2 ), was insulated with a film of plastics (Monokote by Topflite).…”

“…It is interesting to note that NEEs are indeed nanocomposite made by a pre-ordered arrangement of two different materials. On one side, there is the large surface of the templating membrane composed by an insulating organic polymer, typically track-etch polycarbonate (PC) [1,13]. On the other side, each pore of the starting membrane in the final NEE hosts a gold nanowire, suitable for electrochemical transduction.…”