Micro- and nanostructuring of oligo- and polythiophenes in two and three dimensions

Uses of Scanning Electrochemical Microscopy (SECM) for the Characterization with Spatial and Chemical Resolution of Thin Surface Layers and Coating Systems Applied on Metals: A Review

Scanning Electrochemical Microscopy (SECM) is increasingly used in the study and characterization of thin surface films as well as organic and inorganic coatings applied on metals for the collection of spatially- and chemically-resolved information on the localized reactions related to material degradation processes. The movement of a microelectrode (ME) in close proximity to the interface under study allows the application of various experimental procedures that can be classified into amperometric and potentiometric operations depending on either sensing faradaic currents or concentration distributions resulting from the corrosion process. Quantitative analysis can be performed using the ME signal, thus revealing different sample properties and/or the influence of the environment and experimental variables that can be observed on different length scales. In this way, identification of the earlier stages for localized corrosion initiation, the adsorption and formation of inhibitor layers, monitoring of water and specific ions uptake by intact polymeric coatings applied on metals for corrosion protection as well as lixiviation, and detection of coating swelling—which constitutes the earlier stages of blistering—have been successfully achieved. Unfortunately, despite these successful applications of SECM for the characterization of surface layers and coating systems applied on metallic materials, we often find in the scientific literature insufficient or even inadequate description of experimental conditions related to the reliability and reproducibility of SECM data for validation. This review focuses specifically on these features as a continuation of a previous review describing the applications of SECM in this field.

Micropatterned multienzyme devices with adjustable amounts of immobilized enzymes

Multienzyme microstructures of glucose oxidase (GOx) and horseradish peroxidase (HRP) were prepared by layer-by-layer deposition inside microfluidic networks on glass substrates in order to allow both site-specific deposition and control of the amount of immobilized enzymes. The obtained microstructures were characterized by scanning force microscopy for the topography of the deposited layers. The local enzyme activity was characterized by the substrate-generation/tip-collection mode and the enzyme-mediated feedback mode of the scanning electrochemical microscope (SECM). These measurements provided quantitative information about the immobilized enzyme activity as a basis for adjusting enzyme loading for multienzyme structures that realize logical operations based on enzymatic conversions. Information about local HRP activity can also be obtained by optical readout using an Amplex UltraRed fluorgenic substrate and reading with a confocal laser scanning microscope with a much higher repetition rate for image acquisition. Using these principles, a layout with HRP and GOx microstructures was realized that showed the functionality of an OR Boolean logic switch.

Fabrication of self-organized chemically and topologically heterogeneous patterns on the surface of polystyrene-b-oligothiophene block copolymer films

A novel fabrication of the chemically and topologically heterogeneous patterns on the surface of polymeric films over an area of more than 1 square centimeter in a single step was demonstrated by using the self-organizing character of polystyrene-b-oligothiophene block copolymers. Hexagonally arranged open pores of a size of approximately 2 mum are spontaneously formed by casting the polymer solution under a moist air flow. The amphiphilic character of the polystyrene-b-oligothiophene block copolymers played the crucial role as a surfactant to stabilize the inverse emulsion of water droplets in the organic solvent, and subsequently the structure of the arranged hydrophilic oligothiophene segments remained on the interiors of the micropores. The chemical composition of the surface of the microporous films was characterized by time-of-flight secondary ion mass spectrometry (ToF-SIMS) to prove the chemical heterogeneity. The ToF-SIMS imaging clearly indicated that the oligothiophene forms the aggregated structure on the interior of the open micropores on the surface while the flat area on the surface was covered with the polystyrene.