Browsing by Author "Xavier, J."

Now showing 1 - 2 of 2

Electrochemical detection of Cd2+ ions in aqueous samples at nanoelectrodes
(Faculty of Science, University of Kelaniya, Sri Lanka, 2021) Ahmed, M. M. N.; Bodowara, F.; Penteado, J.; Zhou, W.; Xavier, J.; Pathirathna, P.
Contamination from heavy metals has been a potent threat to the environment, and its detrimental effects are felt globally. They bio-accumulate through the food chain, thus leaving humans highly vulnerable to overwhelming health hazards. Most traditional metal-detecting analytical instruments necessitate extensive sample pre-treatment processes, consequently, change metal speciation, one of the most critical factors for evaluating metal toxicity. Furthermore, they are cumbersome, require expensive instruments that are less user-friendly, restricting real-time metal monitoring. As a result, the development of a low-cost, portable, and reliable sensor capable of delivering precise information on metal speciation will significantly assist in the efficient implementation of metal mitigation systems. In this study, we utilize ion transfer between two immiscible electrolyte solutions (ITIES) to design a Cd2+ sensor. The chemistry at ITIES is governed by Gibbs's free energy of transfer for an ion at the interface of two immiscible solvents. A potentiostat is used to supply the energy required to overcome the energy barrier in the form of potential energy, and the resulting current is measured. ITIES is less complicated as it does not involve electron transfer; hence more attractive over other redox-based electrochemical techniques. A suitable ionophore, which lowers the energy barrier and increases the selectivity, can be added to the organic phase, facilitating the transfer of ions at lower potentials. Our electrode is a borosilicate glass electrode with an inner radius of 300 nm. It follows a hemispherical diffusion regime, owing to its nanoscale interface that allows fast kinetic measurements. An ionophore- 1-10 phenanthroline was used to facilitate the Cd2+ transfer across the nano-interface. We performed ITIES based cyclic voltammetry and amperometry experiments with our nanosensor in various matrices, including simple electrolytes like KCl and complicated buffer solutions such as artificial seawater and artificial cerebellum fluid. We also tested the strength of our ionophore against other standard ligands such as Ethylenediamine tetraacetic acid, Nitrilotriacetic acid and Dimercaptosuccinic acid etc. We found out that our electrode shows excellent stability and can withstand the complex matrices without fouling, an attractive feature of an exemplary sensor. We tested our sensor with Cd2+ dissolved in a water sample collected from Indian River Lagoon, Melbourne, FL; thus, we showcase our sensor's power as an environmental monitoring tool. To the best of our knowledge, this is the first time reporting a glass electrode with a sub-nano-meter scale for Cd2+ detection in a natural environmental sample using ITIES. Our ultra-small electrode will enable us to study the kinetics of ion transfer across ITIES; thus, allowing us to modify the sensor to enhance the sensitivity and selectivity.
A novel, ultra-fast, robust microelectrodes for real-time detection of heavy metals using fast-scan cyclic voltammetry
(Faculty of Science, University of Kelaniya, Sri Lanka, 2021) Abbood, R.; Alkhalaf, A. S. K.; Xavier, J.; Pathirathna, P.
Humans are highly vulnerable to being exposed to multiple sources of arsenic and cadmium, such as drinking water, foods, inhalation, and occupational means. The detrimental effects of arsenic and cadmium poisoning are well documented. Electrochemical sensors are more attractive over other analytical tools available for metal detection mainly due to the excellent selectivity, sensitivity, cost, and ease of use by a non-expert in the field. Interestingly, the reported electrochemical sensors for As3+ and Cd2+ in aqueous samples have been primarily performed with gold-based electrodes or other surface-modified electrode materials such as glassy carbon due to their enhanced sensitivity. However, the fabrication process of these electrodes is complex and expensive. Furthermore, most of these experiments were conducted in extreme pH conditions. Although the data obtained with environmental samples are promising, these tools are not suitable for in vivo detection of low concentrations of metals, particularly in the brain, and cannot perform fast measurements. Therefore, in this study, we developed a novel, ultra-fast, and robust electrochemical sensor that can perform real-time detection of As3+ and Cd2+ with a temporal resolution of 100 ms. Our electrode is fabricated with carbon-fibers, thus making an excellent biocompatible sensor for future in vivo studies. We performed our electrochemical measurements with cutting-edge electrochemical technology, fast-scan cyclic voltammetry. We optimized electrochemical parameters (potential window, resting potential, and scan rate) to generate unique cyclic voltammograms to identify As3+ and Cd2+ at a sub-second temporal resolution. Interestingly, we show that we can measure As3+ in the ambient air. We also performed calibration studies, selectivity, and stability studies to evaluate our novel metal sensors. Our preliminary data showcases the power of our tool as an excellent environmental sensor that can detect these two metal ions in aqueous samples. More importantly, these data indicate a great potential for developing this device to perform real-time in vivo measurements of metals in the brain.