Addition of triflate salts to the emeraldine base form of polyaniline in the solid state causes a lowering of its work function but not an increase of its conductivity. It is postulated that this effect is due to the formation of localized energy states in the band gap. On the other hand, strong protonic acids such as triflic acid as well as tetrafluoroboric acid lower both the work function and increase the conductivity of PANI-EB according to the known protonic form of the doping mechanism. The difference between these two kinds of doping has been demonstrated by measurement of the work function, conductivity, UV−vis, and IR spectroscopy.
The objective of this study was to adjust work function of polyaniline (PANI) in the solid state by precisely dosed UV irradiation. For this purpose triphenylsulfonium triflate salt was used as a photo acid generator. The structure of PANI before and after irradiation was characterized by UV−vis and FTIR spectroscopy. It has been observed that the appearance of the 1143-cm-1 band, corresponding to the polaron stretching mode, correlates with the changes of the Fermi level. This observation indicates that electrons in the proton-doped PANI are delocalized, leading to a change in the electronic structure of PANI. The changes result in lowering of the work function of PANI as measured by the field-effect transistor. Nondecomposed triflate salt can be removed by dipping the irradiated film into methanol to prevent further UV light sensitivity and further postexposure acid doping.
Electrodeposition of silver was investigated as a fabrication tool for constricting large (10 3 m 2 ) vias in silicon substrates while leaving a small opening in the center of the via. Silver reduction from ammoniacal silver nitrate was studied at electrodes of novel geometry, i.e., the edge of the vias, with respect to reduction potential, reduction pulse type, and pulse duration. A variety of crystal nucleation and growth patterns were observed and characterized by scanning electron microscopy. It was found that electroplated silver occluded the vias to leave open areas of less than 1 m 2 . Such occlusions might be used as restrictions in microfluidics systems, forming a type of solid-state micropore or nanopore.Electrodeposition of metals on patterned surfaces has been of interest for a number of applications including the deposition of interconnecting elements used in integrated circuits, microelectromechanical systems ͑MEMS͒ and LIGA ͑lithographic-galvanoformung-abformung, or lithography-electroplating-molding͒ processes to name examples. 1-3 In most of these applications, the goal has been to use electrodeposition to completely fill a feature that is patterned on a surface. Filling in surface features such that the deposited metal conforms to all surfaces of high-aspect-ratio topography is challenging and often requires complicated chemistry and experimental techniques. 4 The work reported here is to create a structure by use of electrodeposition to constrict a micrometer-sized opening to submicrometer size. The challenge is to attain precise control of the restriction size during electrodeposition. There have been reports of using templated electroless metal plating for partially filling in track etched membrane filters. 5 However, one feature of the templated method is it produces many pores simultaneously instead of patterning a single pore in a given location. Finer control of the deposition might be obtained using electrochemical methods.Our work is motivated by results and possible applications derived from protein nanopores. Biologically derived protein nanopores have been demonstrated for use in chemical detection and for DNA analysis. 6,7 Protein nanopores are studied while they are inserted in a lipid bilayer film. Because lipid membranes are fragile, the practical realization of these applications might require the use of an anthropogenic nanoscale pore. A stable, robust solid-state mimic might facilitate understanding of bionanopores and transport of large molecules through highly confined spaces by allowing control of the location, dimension, and composition of the pore. The challenge is to create one and only one hole, of nanometer scale in all dimensions, and in a defined location on a given substrate.A fabrication obstacle arises because many techniques which can reliably place patterns are expensive or create structures much larger than nanosize and those that create nanomaterials are often difficult to pattern down to a single feature. 8,9 One approach to resolving this discrepancy might b...
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