Electroanalysis of Bromate, Iodate and Chlorate at Tungsten Oxide Modified Platinum Microelectrode Arrays

Integrated multi-ISE arrays with improved sensitivity, accuracy and precision

Increasing use of ion-selective electrodes (ISEs) in the biological and environmental fields has generated demand for high-sensitivity ISEs. However, improving the sensitivities of ISEs remains a challenge because of the limit of the Nernstian slope (59.2/n mV). Here, we present a universal ion detection method using an electronic integrated multi-electrode system (EIMES) that bypasses the Nernstian slope limit of 59.2/n mV, thereby enabling substantial enhancement of the sensitivity of ISEs. The results reveal that the response slope is greatly increased from 57.2 to 1711.3 mV, 57.3 to 564.7 mV and 57.7 to 576.2 mV by electronic integrated 30 Cl⁻ electrodes, 10 F⁻ electrodes and 10 glass pH electrodes, respectively. Thus, a tiny change in the ion concentration can be monitored, and correspondingly, the accuracy and precision are substantially improved. The EIMES is suited for all types of potentiometric sensors and may pave the way for monitoring of various ions with high accuracy and precision because of its high sensitivity.

Arrays of microelectrodes: technologies for environmental investigations

Within this work it is our intention to provide an overview of the use of arrays or microelectrodes in the characterisation of environmental samples. Electrochemical methods are often a relatively simple and inexpensive alternative to spectroscopic or chromatographic methods for the analysis of a wide range of analytes. Arrays of microelectrodes display a number of advantages over simple planar macroelectrodes and the reasons for this will be detailed within this work. We will also describe some of the most common methods for constructing microarrays. The application of these arrays for analysis of environmental samples such as soil and water for heavy metal contamination has been the major focus of research in this field and comprises much of this review. However other systems will also be detailed such as determination of various anions or other samples such as pesticides.

A comparative study on fabrication techniques for on-chip microelectrodes

This paper presents an experimental study on different microelectrode fabrication techniques, with particular focus on the robustness of the surface insulation towards typical working conditions required in lab-on-a-chip applications. Pt microelectrodes with diameters of 50 μm, 100 μm and 200 μm are patterned on a Si substrate with SiO(2) film. Sputtered SiO(2), low-pressure chemical vapor deposition (LPCVD) low-temperature oxide (LTO), Parylene C, SU-8, and dry-film were deposited and patterned on top of the chips as the passivation layer. This paper provides the detailed fabrication processes, the adhesion enhancement strategies, and the major advantages and disadvantages of each fabrication technique. Firstly, the quality and adhesion strength of the passivations were investigated by means of hydrolysis tests, in which sputtered SiO(2) and dry-film resist showed serious delamination issues and LTO showed minor defects. Secondly, the reliability of the microelectrodes was tested by impedance measurements after overnight ethanol incubation and self-assembled monolayer (SAM) formation. Thirty chips, representing a total of 300 electrodes, were measured, and statistical analyses of the results were conducted for each passivation technique. All of the electrodes passivated with these five techniques showed consistent impedance values after ethanol incubation. On the other hand, only LTO, Parylene C, and SU-8 ensured uniform electrical behavior after SAM formation. Having used both hydrolysis and impedance tests to verify the superior quality of the Parylene-based passivation, electrochemical experiments were performed to study the long-term stability of the passivation layer. Finally, the electrodes were incubated with electroactive alkanethiols functionalized with ferrocene. Square-wave voltammetry measurements demonstrated reproducible results on electrochemical label detection, which confirms the suitability of the Parylene passivation for charge-transfer-based measurements.

New Developments in Electrochemical Sensors Based on Poly(3,4-ethylenedioxythiophene)-Modified Electrodes

There is a growing demand for continuous, fast, selective, and sensitive monitoring of key analytes and parameters in the control of diseases and health monitoring, foods quality and safety, and quality of the environment. Sensors based on electrochemical transducers represent very promising tools in this context. Conducting polymers (CPs) have drawn considerable interest in recent years because of their potential applications in different fields such as in sensors, electrochemical displays, and in catalysis. Among the organic conducting polymers, poly(3,4-ethylenedioxythiophene) (PEDOT) and its derivatives have attracted particular interest due to their high stability and high conductivity. This paper summarizes mainly the recent developments in the use of PEDOT-based composite materials in electrochemical sensors.

Ultramicroelectrode array based sensors: a promising analytical tool for environmental monitoring

The particular analytical performance of ultramicroelectrode arrays (UMEAs) has attracted a high interest by the research community and has led to the development of a variety of electroanalytical applications. UMEA-based approaches have demonstrated to be powerful, simple, rapid and cost-effective analytical tools for environmental analysis compared to available conventional electrodes and standardised analytical techniques. An overview of the fabrication processes of UMEAs, their characterization and applications carried out by the Spanish scientific community is presented. A brief explanation of theoretical aspects that highlight their electrochemical behavior is also given. Finally, the applications of this transducer platform in the environmental field are discussed.

Microelectrode arrays for electrochemistry: approaches to fabrication

Microelectrode arrays have unique electrochemical properties such as small capacitive-charging currents, reduced iR drop, and steady-state diffusion currents. These properties enable the use of microelectrode arrays and have captured much interest in the field of electrochemistry. Techniques for the fabrication of such arrays are reviewed. The relative features and merits of different techniques are also discussed.