Working Electrode Array Research Articles

Aptamer-functionalized screen-printed electrode coupled with graphene oxide and methylene blue nanocomposite as enhanced signal label for total arsenic determination in shellfish

Abstract This work introduces an aptamer-functionalized screen-printed electrode (SPE) coupled with enhanced signal label for total arsenic (As) detection in shellfish, where total As is extracted with dry-ashing method and reduced to detectable As(III). Working electrode array is fabricated on a homemade SPE, proven to be superior to single electrode with equivalent modifications. Au nanoparticles (AuNPs) are electrodeposited onto the SPE to self-assemble As(III)-sensitive aptamer (Ars-3). As(III) response is successfully amplified with an enhanced signal label from the Ars-3/AuNPs/SPE, as provided by the synergistic effect between methylene blue (MB) and graphene oxide (GO). The modifications of AuNPs and Ars-3, as well as the incubation process of GO-MB nanocomposite, are examined by morphological and electrochemical methods. With optimizations of electrochemical setups and sample pretreatments, this method is adopted in a series of analyses with laboratorial and real samples. The limit of detection is 2 × 10−4 mg L-1, and the wide dynamic range up to 10 mg L-1 is well found. The Ars-3/AuNPs/SPE with the GO-MB signal label shows good reproducibility and long-term stability, and presents a high tolerance to possible interference ions. The applicability for real shellfish detection is confidently validated by different means as standard reference material, recovery test and certified ICP-MS.

Miniaturized chemical sensor with bio-inspired micropillar working electrode array for lead detection

A disposable, miniaturized and compact microelectromechanical systems (MEMS) chemical sensor incorporated with three-dimensional, free-standing micropillar working electrode array was proposed, fabricated and tested for electrochemical detection of lead ions. Inspiration of designing arch-shaped columnar sensing electrode array originated from the biological imitation of shark’s olfactory sensing system, considering shark has developed ultrasensitive olfactory capacity during the evolutionary processes. The analytical performance of proposed bio-inspired MEMS chemical sensor was comprehensively investigated. Under optimal conditions, high sensitivity of 32nA/(μg/L) as well as favorable detection limit of 0.2μg/L was achieved with short deposition time of 30s. The sensor exhibited linear responses to lead ions in the concentration range from 1 to 130μg/L with good linearity (correlation coefficient: 0.9994). The collection efficiency towards target ions in the preconcentration step was significantly enhanced by the presence of micropillar electrode array, due to both the enlargement of electrode surface area and the interaction effect between protruding micropillars and moving solution. Proposed MEMS chemical sensor eliminates the involvement of mechanical/forced stirring of testing solution, making it a potential alternative to conventional macro-sized electrochemical sensor for the application of on-site determination of heavy metal contamination.

A CMOS Potentiostat Circuit for Parallel Direct DNA Sensing

An on-chip CMOS potentiostat, including a triangle wave signal generator, a small current signal detector and a potential controller, and its auxiliary circuits are presented for deoxyribonucleic acid (DNA) sensing applications. A fully differential transimpedance amplifier (TIA) with reconfigurable resistors was used for wide range current measurements. An 8×8 pixel array consisting of a 64-pixel rectangular working electrode array with an optimized reference and counter electrode structure is proposed for testing purposes. The design is based on 0.18 μm CMOS technology with a 1.8 V supply. Post-verification measurements show that the scanning signal generator can generate a triangle wave with a tunable frequency when the voltage changes from 300 mV to 1.69 V. The circuit also achieves a large dynamic range of up to 100 dB, and shows very good linearity from 90 pA to 9 μA.

Sampled voltammetry on an electrode array for the renewal of the electrode surface and the analytical solution during the analysis

Polarography with dropping mercury electrode has been widely used in electroanalysis. However, the method is less and less employed due to the toxicity of mercury. In this work, we have shown that it is possible to replace the dropping electrode by a working electrode array, allowing the renewal of the electrode surface and of the analytical solution during the analysis. This new concept has been demonstrated on copper analysis. Sampled current voltammetry has been carried out on an electrode array, giving rise to I vs. E curves with a limiting diffusion plateau. The principle can be extended to other electroanalytical methods as exemplified here with differential pulse voltammetry. Linear calibration curves have been obtained with both methods and a limit of detection of 2×10−5molL−1 has been reached for copper detection by differential pulse voltammetry.

Development of disposable low density screen-printed electrode arrays for simultaneous electrochemical measurements of the hybridisation reaction

Abstract This paper deals with the development of different formats of screen-printed array of electrodes. The arrays consist of a silver pseudo-reference electrode surrounded by four or eight radially distributed working electrodes. Two different commercially available inks were used to fabricate the working electrode (WE) surfaces: a carbon-based ink and a gold-based ink. Due to their low curing temperature, the inks were screen-printed onto an inert plastic substrate. The electrochemical characterisation of these arrays is shown; reproducibility of the arrays as well as the batch-to-batch reproducibility were also assessed. As model case, the four WE array was used as platform to develop an electrochemical genosensor. Analytical parameters such as linearity range, reproducibility and detection limit of the genosensor were evaluated. Preliminary results on real samples were also reported.

Amperometric detector for high-performance liquid chromatography, featuring a glassy carbon working electrode array in the wall-jet configuration

A wall-jet segmented-ring-disc electrode array is applied to reversed-phase HPLC. The segmented-ring electrode consists of eight independent glassy carbon discs, located around the central disc electrode. The electrode array is operated under amperometric conditions, and displays distinct qualitative advantage over other modes of electrochemical detection. The advantages are discussed in relation to data extraction from partially resolved chromatograms. The potential interference effects of closely eluting species are considered by the use of limited quantitative data. The power to distinguish between co-eluting components is clearly demonstrated by comparison with single-wavelength UV absorbance detection. The analytes studied were phenol, 4-methylphenol, 2-nitrophenol, 4-nitrophenol, 2-chlorophenol and 4-chlorophenol. A further application of the electrode array is discussed, that of the analogous operation to the wall-jet ring-disc electrode.

Collection efficiency studies for a wall-jet segmented ring disc electrode

This paper describes a platinum working electrode array in the form of a wall-jet segmented ring disc electrode (a central disc electrode, 1 mm diameter, surrounded by five satellite electrodes of equal diameter). The separation between the centre and any satellite electrode is 0.1 mm. Each electrode in the array can be controlled independently and such that the current from each individual member can be monitored simultaneously. The array, constructed by a different method to those previously reported, has an improved collection efficiency owing to the decrease in separation between the generator and collector electrodes. Results in this paper demonstrate the superior collection efficiency (up to 10.1% at an individual electrode) of this array over previously reported wall-jet segmented ring disc electrodes. A flow rate study was performed to verify that the centre disc and segmented ring electrodes displayed wall-jet and planar electrode response characteristics.

Miniaturized thin-film biosensors using covalently immobilized glucose oxidase

The production of a miniaturized glucose sensor by means of thin-film technology is reported. Two main problems related to miniaturization and device integration were solved: (1) the microminiaturization of a suitable electrochemical cell; (2) localized enzyme immobilization with a technology well suited for device integration. The well-known glucose oxidase/H 2O 2 system was used to determine the glucose concentration. A miniaturized four-electrode arrangement was introduced to measure H 2O 2 produced by the enzyme. A double working electrode array for reproducibility tests or differential measurements to suppress interferences is easily produced and can be placed on glass or flexible polymer substrates by means of thin-film technology. The enzyme was covalently coupled to a derivatized platinum thin-film working electrode by means of 1,2-arenequinones, which yield highly reproducible, fast and stable sensors. Measurement of a drop (5 μl) of physiological glucose solution is easily performed, giving a stable response after 40 s.