Dual microelectrodes decorated with nanotip arrays: Fabrication, characterization and spectroelectrochemical sensing

Abstract

Gold microelectrodes decorated with nanotips were developed for spectroelectrochemical experiments. These new dual probes were fabricated by combining fabrication processes of scanning near-field optical microscopy with photolithography. A nanotip array was produced at the surface of a coherent optical fiber bundle by a wet chemical etching step. The resulting nanostructured surface was sputter-coated with a thin gold layer. This gold film conferred plasmonic properties to the sharp nanotips and served as well as the electrode material to enable electrochemical reactions. A photolithographic process was used to define on the bundle surface nanotips-decorated microelectrodes with tunable dimensions (radii ranging between 20 μm and 3.5 μm) individually or in an array format. The resulting microelectrodes with a regular nanotip pattern were characterized first by cyclic voltammetry. Numerical simulation was used to assess the electrochemical properties of these platforms and the influences of the recessed geometry and of the nanotips. Approach curves were recorded in negative and positive feedback modes of scanning electrochemical microscopy (SECM) on insulating and conducting substrates. Finally, spatially resolved Raman imaging allowed us to detect a mercaptobenzoic acid monolayer adsorbed on the microelectrode surface, demonstrating a surface-enhanced Raman scattering (SERS) effect induced by the gold-coated nanotips with a typical enhancement factor of~7 × 10 4. Such an approach introduces a reproducible method to fabricate promising SERS-active platforms with microelectrode behavior for SECM experiments.

An electrochemical quartz crystal microbalance (EQCM) based on microelectrode arrays allows to distinguish between adsorption and electrodeposition

“…This requirement excludes screen printing. MEAs were prepared by photolithography following the procedures described by Bombail et al 43 and also Lambie et al 44 We did not attempt to miniaturize the resonators themselves as reported by Michalzik et al 45 or to produce arrays of sensors as reported by Rabe et al 46 The Braunschweig group scaled the resonators down in size from 38.1 mm to 3 mm and constructed an 8 × 8 array of resonators on a single quartz wafer using reactive ion etching. The methods chosen here are much simpler.…”

“…This requirement excludes screen printing. MEAs were prepared by photolithography following the procedures described by Bombail et al 43 and also Lambie et al 44…”

Design of optoelectrodes for the remote imaging of cells and in situ electrochemical detection of neurosecretory events

“…optical and electrochemical. The current protocol derives from a previously reported one [50], aimed at designing gold microelectrodes possessing arrays of nanotips on their surface, and their use for spectro-electrochemical characterization of surfaces (physical, biological) by e.g. combined SECM (Scanning Electrochemical Microscopy) [51] and SERS (Surface Enhanced Raman Spectroscopy).…”

Review—Recent Advances in the Development of Nanoporous Au for Sensing Applications

“…Fabrication of electrochemical sensors that take advantage of optical properties has been explored recently in literature, known as spectroelectrochemical sensors. 84,85 This combined approach is well suited for NPG, which possesses both of these properties, making it a strong candidate for this technique going forward which may lead to improved selectivity and sensitivity.…”