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

Maeve H S Mclaughlin,Alexander C Pakpour-Tabrizi,Richard B Jackman

doi:10.1038/s41598-021-89045-2

Maeve H S Mclaughlin, Alexander C Pakpour-Tabrizi + Show 1 more

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https://doi.org/10.1038/s41598-021-89045-2

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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.

Highlights

This work compares the electrochemical impedance response of polished and unpolished boron doped diamond (BDD) electrodes, during mercury detection measurements
The electrochemical impedance spectroscopy (EIS) measurements in this paper are an extension to previous work by the authors, where BDD electrodes, some decorated with gold nanoparticles, were used to detect mercury in a 0.1 M H NO3 electrolyte via square wave anodic stripping voltammetry (SWASV)[8]
The relative proportions of sp3 diamond carbon and sp2 non-diamond carbon at the surface of the BDD and pBDD electrodes was assessed with Raman spectroscopy (Fig. 1a)

Summary

Introduction

This work compares the electrochemical impedance response of polished and unpolished boron doped diamond (BDD) electrodes, during mercury detection measurements. Most typically grown by microwave plasma-enhanced chemical vapour deposition methods, is considered a wide band gap semiconductor, it can display quasi-metallic properties if boron is incorporated at concentrations in excess of 1 020 cm−35. Such heavily boron doped diamond (BDD) as electrode materials are well suited to the high sensitivity detection of mercury and other species via electrochemical measurements. The EIS measurements in this paper are an extension to previous work by the authors, where BDD electrodes, some decorated with gold nanoparticles, were used to detect mercury in a 0.1 M H NO3 electrolyte via square wave anodic stripping voltammetry (SWASV)[8]. Mercury was detected in the potential range 0.5–0.8 V during these SWASV measurements

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