Selective and Practical Graphene-Based Arsenite Sensor at 10 ppb

Abstract

Arsenic detection in field water samples at concentrations of relevance with affordable and simple equipment is of global interest. We report a biomimetic electrode using electrochemically reduced graphene oxide (ERGO) for highly selective and sensitive reagent-free arsenite (As3+) detection in field water samples, down to the ten parts per billion level, enabling measurement of drinking water quality affordably for millions of arsenic-affected people. This electronically and structurally optimized ERGO electrode shows selective detection of As3+ in both phosphate buffered saline (PBS, pH ∼7) and field water samples, even though more than 100 times larger conductivity and total dissolved solids (TDS), respectively, are present in them. Raman and FTIR spectroscopies were used to understand the mechanism of selectivity and sensitivity. The sensing mechanism involved two processes, namely, selective binding of As3+ with the −COOH groups of ERGO followed by its electro-oxidation by an applied potential. Density functional theory (DFT) and force-field calculations were used to obtain crucial insights into the site selectivity and mechanism of oxidation of As3+. A two-electron transfer process from As3+ to ERGO followed by associative O ligand addition to As3+ by a ketone oxygen atom, and concomitant regeneration of −COOH group is presented. The ion selectivity depends both on structural and electronic factors. First, the compact pyramidal-shaped As3+ species may closely approach the edge −COOH functional group to a greater extent than the other ions enabling covalent binding of the As center with the ketone O atom. Furthermore, closer proximity of the lowest unoccupied molecular orbital (LUMO) acceptor level of the positively charged ERGO and the highest occupied molecular orbital (HOMO) donor level of the As3+ species suggests that a uniquely selective resonant charge-transfer effect occurs between the As3+ species and ERGO.

Cysteine-Protected Antibacterial Spheroids of Atomically Precise Copper Clusters for Direct and Affordable Arsenic Detection from Drinking Water

“…The inverse square capacitance (1/C sc 2 ) plot of CASs-coated film decreases with increasing potential. 39,40 From Figure S17b, it is evident that there is a sharp decrease of 1/C sc 2 value with an increase of the potential from −1 to +0.8 V, and the negative slope of the plot indicates that the coating is positively charged. However, the bare GCE shows a positive slope, indicating its negative charge.…”

Vertically Aligned Nanoplates of Atomically Precise Co6S8 Cluster for Practical Arsenic Sensing

“…Arsenic in drinking water affects over 120 million people worldwide, and its grip is expanding continuously due to the excessive use of groundwater, fertilizers, and agrochemicals. , A practical arsenic sensor in water without the need for preconcentration and sophisticated instrumentation is very much in need. Key to developing such practical electrochemical devices for arsenic is the development of stable, selective, sensitive, and affordable electrodes. , Increased sensitivity requires the electrode to be composed of specific chemical species with morphologies or superstructural microcrystalline assemblies, enhancing the specific surface areas. − In view of the sensitivity of cobalt-based systems for arsenic sensing, we decided to explore the atomically precise Co 6 cluster system to develop a practical sensor. We have developed a method of ambient electrospray deposition (ESD) of the Co 6 cluster system leading to their 2D nanostructures with unique morphologies. − In this work, we present a practical electrochemical arsenic sensor based on the resulting structures for arsenite detection down to 5 parts per billion (ppb) in tap water implementable in field applications.…”

“…Key to developing such practical electrochemical devices for arsenic is the development of stable, selective, sensitive, and affordable electrodes. 26,27 Increased sensitivity requires the electrode to be composed of specific chemical species with morphologies or superstructural microcrystalline assemblies, enhancing the specific surface areas. 28−30 In view of the sensitivity of cobalt-based systems for arsenic sensing, 31 we decided to explore the atomically precise Co 6 cluster system to develop a practical sensor.…”

Selection of Highly Specific DNA Aptamer for the Development of QCM‐Based Arsenic Sensor

“…[1] Arsenic groundwater contamination has been reported in over 70 countries. [2] There are various reports on arsenic detection, which comprise optical sensors, [3][4][5] electrochemical sensors, [6][7][8] Plasmonic sensors, [9,10] calorimetric sensors, etc. [11,12] Though different assays have achieved satisfying detection capabilities and selectivity, these techniques require labelling, multiple washing, and characterization steps.…”