Recent topics on the wet processes to form micro and nano structures for functional applications were introduced. A novel lithography process was developed for nanoscale patterning using electron beam lithography in combination with a resist material, organosilane self-assembled monolayer, which achieved patterning of arrayed nanodots as small as 20 nm in diameter. A photo-assisted Si anodization process to fabricate microscale pore arrays was also described. Using prepatterned array of pits on Si wafer surfaces as initiation sites, electrochemical etching was carried out in aqueous fluoride solution under the illumination from back side of the wafer to form arrays of uniform and high aspect ratio pores at the selected areas. The pore array was used for further modification, to fabricate pL volume SiO2 “test tubes” using surface oxidation and wet etching processes. Metal filling to the pores was also attempted to fabricate a microscale needle array.
Since an organic superconductor (TMTSF)2PF6 was discovered, many researches have been directed toward the achievement of organic superconductivity. A great number of organic superconductors are now known, most of which are charge-transfer (CT) salts. Electrocrystallization is a powerful tool for the preparation of CT salts, including those with superconductivity. Recently, new types of organic superconductors, such as non-TTF-based superconductors and magnetic superconductors with the field-induced superconductivity and with superconductor-insulator transitions, have been developed.
A key to realize the high performance of organic devices using conducting polymers is how to fabricate a highly organized structure on surface in a single molecular scale. Here we have demonstrated a new single-molecular processing-technique using electrochemistry that is called ‘electrochemical epitaxial polymerization’. This technique is based on a step-by-step electropolymerization of monomer along the lattice of iodine-covered Au(111) surface to form the single conjugated-polymer wires by applying voltage-pulses into monomer-electrolyte solution. By using this technique, we have succeeded in building a uniform high-density array of single conducting-polymer wires as long as 200 nm, under the control of density, length, direction and shape of the wires on the electrode. This first observation will open the door to a mass-production of single molecular-scale devices using conducting polymers.
Various important techniques to investigate the structure of solid/liquid interfaces are briefly described. It is shown that the monitoring of electrode surface reactions and the understanding of the relation between geometric/electronic structures and electrochemical characteristics become possible by combining various techniques. We placed the focus on Pd deposition on Au single crystalline electrodes.
Until the mid 1980s, there had been only a few in situ methods available for the atomic level structural determination of electrode surfaces in solution. Now several investigations have demonstrated that electrochemical scanning tunneling microscopy (EC-STM) is a powerful technique for in situ characterization, with atomic resolution, of surfaces under potential control. The object of this article is to highlight some of the advances in in situ scanning tunneling microscopy (STM) with atomic resolution. Several selected topics, observation of clean platinum electrode surface, specifically adsorbed anions such as iodine and sulfate on metal surfaces, adsorption of porphyrin on clean and iodine-modified electrodes, and binary adlayer consisting of porphyrin and phthalocyanine on gold electrode are focused on.
It is very important to determine the structure of electrode/electrolyte interface in situ not only for the study of fundamental surface science but also for the applications related to nanotechnology. Surface X-ray scattering (SXS) technique is one of the most promising methods to determine the interfacial structure with a high spatial resolution in situ. Here we focus on the SXS technique that enables to probe an interfacial structure even at solid/liquid interface. As an example, we described our results about the structural analyses of the electrochemical deposition processes of Pd and Ag on Au single crystal electrodes using the in situ SXS technique.
In Situ high-resolution FT-IR and Raman Spectroscopies combined with electrochemical analysis have been applied to the study of the electrochemical interface between the electrode and electrolyte solutions. This combination has proved to be advantageous for studying the reactions in the interfacial reaction field between the electrode and electrolyte solutions. These techniques, referred to as FT-IR and Raman spectro-electrochemistry, reveal the vibrational spectro-electrochemistry at the electrochemical interface under potentiostatic conditions. This paper describes that the in situ spectro-electrochemistry is a powerful tool for investigating electrochemical interface.
Information on the structure and surface reaction dynamics of an electrode/electrolyte interface is essential to reveal the reaction mechanisms and to control electrochemical reactions. Since the second order nonlinear optical processes such as second harmonic generation (SHG) and sum-frequency generation (SFG) are forbidden in the media of centro-symmetry, these techniques provide interface specific information and can be used to probe buried interfaces as far as they are accessible by light. We applied SHG and SFG to obtain information on electronic and molecular structure at the electrochemical interfaces and two examples are presented here. First, the electrochemical reaction HCHO at Pt surface was investigated by SHG spectroscopy. Next, the structure of interfacial water was characterized under potential control by SFG spectroscopy.
Ultrahigh vacuum-electrochemistry (UHV-EC) combined system can be utilized not only for single crystal electrode surfaces but also for particle catalysts. In this paper, using a cathode catalyst for fuel cells as an example, the characterization of nanoparticle catalysts by a UHV-EC system is described.
It is essential to develop high performance Pt electrocatalysts and to reduce the amounts used in polymer electrolyte fuel cells. Design of high performance cathode alloy catalysts for O2 reduction and anode alloy catalysts for highly CO-tolerant H2 oxidation as well as direct CH3OH oxidation will be introduced, based on the results investigated by our group. Problems accompanied with practical catalysts highly dispersed on carbon black supports and some solutions to the problems will also be discussed.
We have studied the charge transfer reactions at electrode/electrolyte interfaces in lithium-ion batteries and found that there exist large activation barriers at the interface for lithium-ion to insert and extract at the electrodes. By the theoretical calculation, the activation barriers were found to be correlated with the interaction between lithium-ion and solvent in electrolyte, and therefore, the activation barriers are principally due to the de-solvation process of lithium-ion in the electrolyte. These results are also confirmed by the model interface consisted of electrolyte/electrolyte. Based on these results, we discuss how the rate performance of lithium-ion batteries will be enhanced.
We review here several recent studies on protein patterning with microcontact printing (μCP), microfluidic networks (μFN), and dip-pen nanolithography (DPN). Microcontact printing (μCP) is a softolithographic technique and has been found to be appropriate for direct-printing with various proteins onto glass substrates at the monolayer level. However, little is known about the mechanism of the μCP process, in which the protein monolayer is transferred from the PDMS stamp to the substrate surface. Microfluidic network (μFN) features parallel microfluidic channels to make multi-color patterning with proteins, which allows us a high-throughput platform for multi-immunoassay named as “micromosaic immunoassay”. By combining the techniques of μFN and μCP, multi-color printing is possible with a single stamping. In DPN, relatively larger molecules such as immunoglobrin can be transferred from a cantilever probe to the substrate with nm-resolution. The transfer mechanism might be shared with μCP.