Fabrication of Boron-Doped Diamond Film Electrode for Detecting Trace Lead Content in Drinking Water

At a Glance

Metadata	Details
Publication Date	2022-08-31
Journal	Materials
Authors	Liang Wu, Xinghong Liu, Xiang Yu, Shijue Xu, Shengxiang Zhang
Institutions	China University of Geosciences (Beijing)
Citations	5
Analysis	Full AI Review Included

Executive Summary

This study details the fabrication and characterization of a highly sensitive Boron-Doped Diamond (BDD) film electrode on a porous titanium substrate, designed for the trace detection of lead ions (Pb²⁺) in drinking water using Square Wave Anodic Stripping Voltammetry (SWASV).

Core Achievement: Successfully fabricated a BDD electrode via Hot-Filament Chemical Vapor Deposition (HFCVD) that exhibits superior stability and sensitivity compared to conventional metal film electrodes.
Structural Quality: The BDD film showed high phase quality, confirmed by Raman spectroscopy (D band at 1330 cm^-1, absence of G peak on the surface), and featured a regular tetrahedral grain structure (~8 µm average size) with preferred (111) orientation.
Electrochemical Performance: Demonstrated an exceptionally wide potential window (2.2 V) and a low charge transfer resistance (R_ct = 6.54 Ω), facilitating rapid and efficient Pb²⁺ dissolution kinetics.
High Sensitivity: Achieved a low Limit of Detection (LoD) of 2.62 ppb for Pb²⁺, significantly below the WHO maximum recommended limit of 10 ppb.
Operational Range: The electrode maintained excellent linearity (R² = 0.994) across the critical concentration range of 5-30 ppb.
Robustness: The BDD electrode exhibited good anti-interference ability, maintaining signal integrity when common heavy metal ions (Cd²⁺, Cu²⁺, Zn²⁺) were present at equal concentrations.

Technical Specifications

Parameter	Value	Unit	Context
Substrate Material	Porous Titanium	N/A	Base for BDD film deposition
Deposition Method	HFCVD	N/A	Hot-Filament Chemical Vapor Deposition
Deposition Temperature	700	°C	Main growth parameter
B/C Doping Ratio	6000	ppm	Boron concentration in gas phase
C/H Ratio	2.4	%	Carbon source ratio
Deposition Pressure	3	KPa	Main growth parameter
Electrode Potential Window	2.2	V	Range: -1.2 V to +1.0 V (vs. SCE)
Charge Transfer Resistance (R_ct)	6.54	Ω	Measured via EIS in K₃[Fe(CN)₆] solution
Electrochemical Active Area	4.38	cm²	Calculated using Randles-Sevcik equation
Limit of Detection (LoD)	2.62	ppb	Calculated using 3N/S formula
Linear Detection Range	5-30	ppb	Concentration range for Pb²⁺
Electrode Sensitivity (S)	1.45	µA L µg^-1 cm^-2	Slope of the standard curve
Optimized Enrichment Time	150	s	SWASV parameter for maximum signal
Optimized Scanning Frequency	50	Hz	SWASV parameter for maximum signal
Average Diamond Grain Size	~8	µm	Observed via SEM
Raman D Band (Surface)	1330	cm^-1	Indicates diamond phase and Fano effect from doping

Key Methodologies

The BDD electrode was fabricated using a Hot-Filament Chemical Vapor Deposition (HFCVD) system on a titanium substrate, followed by electrochemical characterization and optimization.

Substrate Preparation: A titanium metal slice was cleaned and then seeded by immersion for 10 minutes in a solution of nanodiamond (ND) in ethanol (5 g ND/20 mL ethanol).
Doping Source: Diboron trioxide (B₂O₃) was dissolved in ethanol to serve as the boron doping source.
Nucleation Stage (0.5 h):
- Gases: Methane (CH₄) as carbon source, Hydrogen (H₂) as etching gas.
- Flow Ratio (H₂:CH₄): 10:1000 sccm.
Growth Stage (7.5 h):
- Gas Flow: C₂H₅OH + H₂ + B₂O₃:H₂ = 25:50:1000 sccm.
- Key Parameters: C/H ratio (2.4%), B/C ratio (6000 ppm), Pressure (3 KPa), Temperature (700 °C).
Structural Characterization: Scanning Electron Microscopy (SEM) was used for morphology, and Raman confocal microscopy was used to confirm diamond phase quality (sp³-C) and boron doping.
Electrochemical Testing:
- Cyclic Voltammetry (CV) determined the potential window (2.2 V) and background current.
- Electrochemical Impedance Spectroscopy (EIS) measured the charge transfer resistance (R_ct).
- Square Wave Anodic Stripping Voltammetry (SWASV) was used for Pb²⁺ detection.
Parameter Optimization: Enrichment time (optimized at 150 s) and scanning frequency (optimized at 50 Hz) were adjusted to maximize the dissolution peak current for 30 ppb Pb²⁺.

Commercial Applications

The developed BDD electrode technology offers a highly stable and sensitive platform for heavy metal detection, making it suitable for integration into advanced monitoring systems.

Environmental Monitoring and Public Health:
- Real-time trace monitoring of Pb²⁺ content in drinking water systems, ensuring compliance with WHO standards (10 ppb maximum).
- Deployment in remote or distributed water quality sensor networks due to the BDD electrode’s long life and chemical stability.
Industrial and Wastewater Treatment:
- Monitoring heavy metal effluent (Pb²⁺, Cd²⁺, Cu²⁺, Zn²⁺) from industrial processes (e.g., mining, battery manufacturing) before discharge.
Sensor Manufacturing:
- Development of robust, high-performance electrochemical sensors (voltammetric sensors) that replace less stable mercury or bismuth film electrodes.
Advanced Oxidation Technologies (AOT):
- While focused on sensing, BDD materials are widely used in AOT for pollutant degradation, leveraging their wide potential window and high electrochemical activity.

View Original Abstract

This work aimed to fabricate a boron-doped diamond film electrode for detecting trace amounts of lead in drinking water so as to safeguard it for the public. Available detectors suffer from high costs and complex analytical processes, and commonly used electrodes for electrochemical detectors are subject to a short life, poor stability, and secondary pollution during usage. In this work, a boron-doped diamond (BDD) electrode was prepared on a porous titanium substrate, and the microstructure and electrochemical properties of the BDD electrode were systematically studied. Moreover, the stripping parameters were optimized to obtain a better signal response and determine the detection index. As a result, diamond particles were closely arranged on the surface of the BDD electrode with good phase quality. The electrode showed high electrochemical activity, specific surface area, and low charge transfer resistance, which can accelerate the stripping reaction process of Pb2+. The BDD electrode presented a low detection limit of 2.62 ppb for Pb2+ under an optimized parameter set with an enrichment time of 150 s and a scanning frequency of 50 Hz. The BDD electrode also has good anti-interference ability. The designed BDD electrode is expected to offer a reliable solution for the dilemma of the availability of metal electrodes and exhibits a good application prospect in the trace monitoring of Pb2+ content in drinking water.

Tech Support

Original Source

DOI: https://doi.org/10.3390/ma15176013

References

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