Feb 12, 2009
Nanopatterning of boron-doped diamond surfaces
German and French scientists present a facile electro-oxidative technique to structure organic monolayers on boron-doped diamond.
One widely utilized process for local nanopatterning is field enhanced oxidation, also referred to as local anodic oxidation. It consists of the application of a small voltage between a positively biased sample interface, acting as the anode, and a conductive tip, brought to the vicinity of the surface. Along the path followed by the scanning probe, oxidation patterns are formed. The phenomenon occurs in ambient air in the presence of an adsorbed thin water layer, leading to surface anodization on a scale depending on the dimension of the water meniscus formed between the probing tip and the interface. In recent years, this technique has been proposed for the local modification of surfaces such as Au, Ti, Si, SiOx and mica on a micro- or nanometer scale, allowing a simultaneous visualization of the generated patterns.
The interest in boron-doped diamond (BDD) interfaces has drastically increased in the last decade due to its exceptional physical properties combined with semi-metallic surface conductivity. This together with the absence of surface oxide formation and reduction reactions, which are found on conventional metal and metal oxide electrode materials between oxygen and hydrogen evolution, helped the development of a large range of electroanalytical applications of BDD interfaces. In view of potential bioanalytical applications as renewable supports, patterning of monolayers is very important, because molecular patterns can serve as templates for the immobilization of biorecognition elements such as DNA, proteins or even entire cells. Recently, researchers from Germany and France have moved one step closer to this goal. They showed the possibility of selective pattering of organosilane monolayers on synthetic oxidized BDD electrodes in the nanometer range by electro-oxidation. The procedure was particularly successful with monolayers of n-octadecyltrichlorosilane (OTS). A quantitative evaluation of the patterning conditions, namely the required potential bias and the relative humidity (RH) led to the conclusion that for a total removal of the OTS monolayer from the BDD substrate, a potential bias of 3−3.5 V and a RH>70% are required. The possibility of selectively removing organic monolayers from BDD electrodes opens perspectives for the generation of micro- to nanometer sized patterns on this versatile electrode material.
The researchers presented their work in Nanotechnology.
About the author
Sascha E. Pust is a PhD student at the Institute of Pure and Applied Chemistry, University of Oldenburg, Germany. His research focuses on the localized characterization and modification of biomaterials and other functionalized supports. Sabine Szunerits is a Professor in Nanoelectrochemistry at the Grenoble Institute of Technology (INPG). Her research interests range from local investigations of functional interfaces to the development of sensitive interfaces for opto- and electroanalytical applications. Rabah Boukherroub is a group leader at the Interdisciplinary Research Institute (IRI, Lille). His research interests are in the area of functional materials, surface chemistry and biosensors. Gunther Wittstock is the head of the Condensed Matter Interfaces & Electrochemistry group at the University of Oldenburg, Germany. His research interests range from classic electroanalytical applications to the characterization of new functional materials utilizing microelectrochemical techniques, especially scanning electrochemical microscopy. Financial support by the Deutsche Forschungsgemeinschaft (DFG), the German Academic Exchange Office (DAAD) and the Hanse Institute for Advanced Study is gratefully acknowledged.