Carbon Nanotube–Based Electrodes for Detection of Low–ppb Level Hexavalent Chromium Using Amperometry

Abstract

Carbon nanotube (CNT)-based electrodes, prepared using a printable technique, were investigated for the electrochemical detection of hexavalent chromium (Cr(VI)). CNT pastes were coated onto paper substrates and commercially available screen-printed electrodes and used as amperometric sensors for Cr(VI). The CNT electrodes showed electrochemical current responses as high as 500 nA/ppb Cr(VI) and limit of detection as low as 5 ppb when a large area electrode was used. The CNT-modified, screen-printed electrodes showed good selectivity to Cr(VI) and were effective for quantifying the Cr(VI) levels in cooling tower blowdown water. A selective H 2 O 2 reduction technique was also applied to Cr(VI) detection and integrated into amperometric detection in a flow cell. These studies show that CNT-based electrodes can be promising for field applications and real-time monitoring of low-level Cr(VI) in power plant waters.

A Solution‐Processed High‐Temperature, Flexible, Thin‐Film Actuator

“…The final concentration was around 2 mg mL −1 . The CNT solution was made by sonicating ≈15 mg of P3 (Carbon Solution) SWCNT in 5 mL of a mixed solvent of 50%:50% (volume) water:ethanol using a probe sonicator (Sonics & Materials, Model: VC505, 500 W) and pulse mode (1 s on, 1 s off, 25% amplitude) for ≈20 min . Then, the CNT‐BN bilayer film was fabricated by sequential filtration of ≈5 mL of a 3 mg mL −1 CNT solution and ≈6 mL of a 3 mg mL −1 BN solution onto a poly(tetrafluoroethylene) (PTFE) filter with a pore size of 200 nm.…”

Electrochemical Sensors for Heavy Metal Ion Detection in Aqueous Medium: A Systematic Review

“…Nanomaterial-modified electrodes show a lot of benefits, such as a higher ratio of surface area to volume, low cost, high porosity, and easy modification. Carbon nanotubes were used to print on different electrodes, such as fluorine-doped tin oxide glass, a flexible paper electrode, and a screen-printed electrode for the fabrication of an amperometric sensor for chromium ion measurement . With the help of carbon nanotubes, the current response can be made stronger, which makes it possible to measure the heavy metal ion even at trace levels at concentrations as low as 5 μg/L.…”

“…Carbon nanotubes were used to print on different electrodes, such as fluorine-doped tin oxide glass, a flexible paper electrode, and a screen-printed electrode for the fabrication of an amperometric sensor for chromium ion measurement. 125 With the help of carbon nanotubes, the current response can be made stronger, which makes it possible to measure the heavy metal ion even at trace levels at concentrations as low as 5 μg/L. The same method was used by Rosolina et al 126 to investigate the effect of carboxylated, single-walled carbon nanotubes on glassy carbon electrodes, as well as pyridinium-functionalized sol–gel thin films on the detection of chromium ions by square wave voltammetry.…”

Recent Advances in Electrochemical Monitoring of Chromium

“…Printed carbon nanotubes (CNTs) onto the different electrodes (screen printed electrode, flexible paper electrode and onto fluorine-doped tin oxide glass) was carried out to fabricate specific amperometric sensor for Cr(VI) measurement. The use of CNTs allows the increase of the current response, resulting in the determination of Cr(VI) at trace levels at a concentration as low as 5 µg·L −1 [ 31 ]. Similarly, the modification of glassy carbon electrode (GCE) by carboxylated single-walled carbon nanotubes and pyridinium functionalized sol-gel thin film was carried out successfully by Samuel M. Rosolina and coworkers for Cr(VI) monitoring by square wave voltammetry (SWV) [ 32 ].…”