Abstract
Microelectrodes offer higher current density and lower ohmic drop due to increased radial diffusion. They are beneficial for electroanalytical applications, particularly for the detection of analytes at trace concentrations. Microelectrodes can be fabricated as arrays to improve the current response, but are presently only commercially available with gold or platinum electrode surfaces, thus limiting the sensing of analytes that are more electroactive on other surfaces. In this work, gold (Au), copper (Cu), and palladium (Pd) are electrodeposited at two different potentials into the recessed holes of commercial microelectrode arrays to produce 3-dimensional (3D) spiky, dendritic or coral-like structures. The rough fractal structures that are produced afford enhanced electroactive surface area and increased radial diffusion due to the 3D nature, which drastically improves the sensitivity. 2,4,6-trinitrotoluene (TNT), carbon dioxide gas (CO2), and hydrogen gas (H2) were chosen as model analytes in room temperature ionic liquid solvents, to demonstrate improvements in the sensitivity of the modified microelectrode arrays, and, in some cases (e.g., for CO2 and H2), enhancements in the electrocatalytic ability. With the deposition of different materials, we have demonstrated enhanced sensitivity and electrocatalytic behaviour towards the chosen analytes.
Highlights
Electrochemical gas sensors are commonly used to detect chemical species and are widely commercially available from a number of companies [1]
By electrodepositing different metals into the holes of the MATFEs, we demonstrate a method to extend the type of materials assessable, to selectively target sensing towards different analytes of interest
This agrees with the unique rough fractal structures observed from scanning electron microscopy with the unique rough fractal structures observed from scanning electron microscopy characterisation
Summary
Electrochemical (amperometric) gas sensors are commonly used to detect chemical species and are widely commercially available from a number of companies [1]. Amperometric sensors offer several advantages compared to other analytical techniques, including low power consumption, the ability to operate efficiently at room temperature, simple design and fabrication, high portability, and low cost. They are often used for agricultural, clinical, environmental, workplace safety and industrial analysis [1]. In order to expand the applications of such devices, a focus has been placed on their miniaturisation, with the recent availability of low-cost planar electrode devices [5,6]. Micro-electrodes are beneficial for electroanalytical applications due to the high current density and lower ohmic drop as a result of increased radial diffusion (see Figure 1a) [8,9]. By electrodepositing different metals into the holes of the MATFEs, we demonstrate a method to extend the type of materials assessable, to selectively target sensing towards different analytes of interest
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