A detailed EIS study of boron doped diamond electrodes decorated with gold nanoparticles for high sensitivity mercury detection

Abstract

This work compares the electrochemical impedance response of polished and unpolished boron doped diamond (BDD) electrodes, during mercury detection measurements. For each substrate type both bare electrodes and electrodes decorated with average diameter 30 nm AuNPs were used, to investigate the role of AuNPs during mercury sensing with diamond electrodes. In square wave anodic stripping voltammetry (SWASV) measurements for mercury detection, the mercury ions in the electrolyte are deposited onto, then stripped from the diamond electrode surface. To investigate the different electrode performances during these steps, the EIS measurements were made at the deposition and stripping potentials, alongside scans at open circuit potential for comparison. The performance of the electrodes is assessed in terms of their electron transfer rate (k0). The electrodes decorated with AuNPs are shown to have lower capacitance and higher reactivity than the bare pBDD and BDD electrodes, until the mercury concentration in the electrolyte is < 500 µM, when the sp2/sp3 carbon ratio at the surface of the electrodes has a greater influence on the sensitivity for mercury detection than the presence of AuNPs.

Diamond-Based Electrodes for Detection of Metal Ions and Anions

“…However, this work lacks interference and real analysis; therefore, it can be noted as a preliminary study. Thereafter, McLaughlin and coworkers demonstrated the use of AuNP-decorated BDD (B atoms at 10 20 cm −3 doping concentration) towards detection of Hg 2+ via SWASV responses and stripping voltammetry-based electron impedance spectroscopic (EIS) studies [ 82 , 83 ]. The SWASV response of AuNPs–BDD to Hg 2+ (scan range = 0.35 to 1.1 V; Ag/AgCl and Pt-wire as the reference and counter electrodes in 3M KCl; scan rate = 2.5 mV s −1 ) displayed a linear response from 0.5–100 µM with an LOD of 5 µM [ 82 ].…”

“…The SWASV response of AuNPs–BDD to Hg 2+ (scan range = 0.35 to 1.1 V; Ag/AgCl and Pt-wire as the reference and counter electrodes in 3M KCl; scan rate = 2.5 mV s −1 ) displayed a linear response from 0.5–100 µM with an LOD of 5 µM [ 82 ]. On the other hand, the SWASV-based EIS studies under the similar condition displayed a wide linear regression from 1 pM to 1 mM [ 83 ]. In both reports, authors explained the role of the AuNPs in different sizes (22 nm and 30 nm, respectively) and the sp 2 /sp 3 carbon ratios in the enhanced response to Hg 2+ .…”

“…Thus, careful optimization becomes essential. Table 1 summarizes the doping concentrations of specific atoms, methods of detection, linear regressions, and LODs of nanodiamond-based electrodes towards metal ions [ 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 , 92 , 93 , 94 , 95 , 96 , 97 , 98 , 99 , 100 , 101 , 102 , 103 ].…”

Rational Design of Diamond Electrodes

“…Starting from these diamond films and diamond composites, numerous nanostructured diamond electrodes (e.g., wires, foam, particles) have been produced by means of different approaches. Recently, diamond electrodes have been frequently utilized in the fields of electrochemical energy storage, − electrochemical energy conversion, − and electrosynthesis, , in addition to their “standard” chemical/biochemical sensing − and environmental degradation − applications.…”

First Screen-Printed Sensor (Electrochemically Activated Screen-Printed Boron-Doped Diamond Electrode) for Quantitative Determination of Rifampicin by Adsorptive Stripping Voltammetry

“…One of the most valuable properties of BDDEs is the electrogeneration of hydroxyl radicals under polarization at high anodic potentials resulting in a low electrochemical activity for the oxygen evolution reaction and a high chemical reactivity for organics oxidation [ 18 ]. Furthermore, BDDEs are stable at extreme temperatures and pressures and resistant to fouling, so are ideal for the application of portable sensors for in situ measurements over extended periods of time, even in harsh environments [ 19 ].…”