Selective detection of Cr(VI) using a microcantilever electrode coated with a self-assembled monolayer

Abstract

We have demonstrated detection of Cr(VI) ions using functionalized microcantilevers under electrochemical control. Au-coated microcantilever working electrodes are modified with self-assembled monolayers of 4-mercaptopyridine (4-mPy) in sulfuric acid solution. Differential surface stress changes at the modified microcantilever have been measured as a function of applied potential while simultaneously measuring the current-potential response by cyclic voltammetry. The selective adsorption of Cr(VI) on 4-mPy monolayer-coated microcantilever electrode is attributed to hydrogen bonding. The stressogram (first derivative of surface stress of microcantilever with respect to potential versus electrode potential) suggests that a small amount of an intermediate oxidation state of chromium is retained at the 4-mPy monolayer, and this intermediate reduction product of Cr(VI) can be reversibly oxidized on the surface. Our results demonstrate that changes of differential surface stress due to the adsorption-controlled electrochemical reaction can be observed at high sensitivity. This potential controlled microcantilever technique offers insights into the behavior of the solid-liquid interface during electrochemical reactions at modified electrodes.

Speciation Analysis of Chromium in Environmental Samples

“…166 The selective detection of the various forms of Cr is based on the differences in the reduction potentials of Cr(VI) and Cr(III). Apart from mercury and platinum electrodes, gold electrodes and platinum ones modified with nanomaterials are used for these determinations, 167,168,169 examples of which are the electrode obtained by coating an electrode with a self-assembled monolayer (SAM) of gold nanoparticles (AuNPS) 170,171,172,173 or the modification of an electrode with gold nanoparticles and indium-tin oxide (ITO), which exhibits catalytic properties as well as better sensitivity and stability in Cr(VI) reduction. 169 According to literature reports, the electrochemical behavior of Cr(VI) depends to a considerable extent not only on the electrolytes used, but also on the electrode material (see Table 8).…”

Microcantilevers Modified with Ferrocene-Terminated Self-Assembled Monolayers: Effect of Molecular Structure and Electrolyte Anion on the Redox-Induced Surface Stress

“…Electrochemical reactions represent one type of transformation that has been used to drive the deflection of metal-coated cantilevers for sensing or actuator applications. Examples include underpotential metal deposition, oxidation−reduction of metal ions, doping/dedoping of conducting polymers, , electrocapillary effects, and redox-controlled movement of bistable [3] rotaxanes . The voltage potential applied to the cantilever (working electrode) is the external stimulus that triggers the electrochemical processes.…”

Interferometric measurement using bimorph actuated staggered mirror (BASM) microsensor

“…Microcantilever sensors have been extensively used for physical [1], chemical [2][3][4][5][6][7][8][9][10][11], and biological [1,[12][13][14][15][16] detection. A cantilever sensor deflects due to physically or chemically induced surface stress.…”