Enhanced Potentiometry by Metallic Nanoparticles

Abstract

Measuring the oxidation-reduction potential (Eh) requires an interface that is not selective toward specific species but exchanges electrons with all redox couples in the solution. Sluggish electron transfer (ET) kinetics with the species will not reflect the "true" Eh of the solution. Here, we present a novel approach by which adsorbed metal nanoparticles (NPs) are used for enhancing ET exchange rates between redox species and electrode surface and therefore affect significantly the measurement of the open circuit potential (OCP) and cyclic voltammetry (CV). The OCP and CV of various organic and inorganic species such as l-dopa, dopac, iron(II), and iodide are measured by bare stainless steel and by stainless steel modified by either Pt or Au NPs. We study the effect of the surface coverage of the stainless steel surface by NPs on the electrochemical response. Moreover, the stainless steel electrode was modified simultaneously by Au and Pt nanoparticles. This improved concurrently the stainless steel response (CV and potentiometry) toward two different species; l-dopa, which shows fast electron transfer on Pt, and catechol, which exhibits fast electron transfer on Au. We believe that this approach could be a first step toward developing a superior electrode for measuring the "true" Eh of complex aquatic systems.

Copper Sulfide Nanocrystal Level Structure and Electrochemical Functionality towards Sensing Applications

“…Such activity can be explained by the fact that adsorbed copper sulfide NCs on the working electrode catalyze and mediate the H 2 O 2 reduction reaction. A mediator is usually used in order to enhance the electron transfer among the analyte (redox species) and the electrode surface . Upon oxidation, the Cu 2− x S nanocrystals show a significantly lower current with no clear peak development (Figure b).…”

Potentiometric Measurements in Biofouling Solutions: Comparison of Nanoporous Gold to Planar Gold

“…3 For the work described herein, the indicating electrode is an inert metallic redox electrode that is purposely designed to be nonselective and will 'ideally' respond to all redox active species in solution able to exchange electrons with the metallic surface. 1,2 When the indicator electrode is immersed in solution, it will equilibrate electrochemically with the dissolved redox species and a potential will develop at its surface. The measured potential is governed by factors such as (1) the redox species present, (2) their concentrations (activities), and (3) the rate of electron exchange with the electrode.…”

“…The measured potential is governed by factors such as (1) the redox species present, (2) their concentrations (activities), and (3) the rate of electron exchange with the electrode. 2,4,5 Such redox measurements have been used to characterize the redox state of solutions with a complex matrix including milk, cheese, sludge, water and biological systems. [6][7][8][9][10][11][12][13] An important and often neglected factor in the measurement of redox potential is the nature of the electrode surface, particularly the presence and extent of modification, contamination, and fouling/poisoning, as these variables can significantly reduce electron exchange rates.…”

“…5,14 To increase the quantitative usefulness of redox potential measurements in complex environments, it's necessary to design elec-trodes that will minimize the impact of contamination on the electrode response and facilitate electron exchange with as many redox species as possible. 2 In this work, we closely examined two electrodes -planar gold and nanoporous gold [15][16][17] -and evaluated their potentiometric redox response in solutions of increasing biological complexity. Nanoporous gold (NPG), in particular, has been shown to minimize the effect of biofouling on an electrochemical response via a biosieving-like mechanism [18][19][20] and facilitate charge transfer via nanoconfinement.…”

High Sensitive Surface Plasmon Resonance (SPR) Sensor Based on Modified Calix(4)arene Self Assembled Monolayer for Cadmium Ions Detection

“…Low levels of cadmium ions was obtained by the under potential deposition on a selfassembled monolayer on gold electrode. 35) In this work, a chromogenic calix(4)arene molecule was immobilized onto modified SAM gold surface of an SPR sensor chip for cadmium ions detection. The functionalization of SPR sensor is based on the oxidation of calixarene-SAM alcohol group to quinone.…”