Nitrate Sensor with a Wide Detection Range and High Stability Based on a Cu-Modified Boron-Doped Diamond Electrode

At a Glance

Metadata	Details
Publication Date	2024-04-01
Journal	Micromachines
Authors	Shengnan Wei, Danlin Xiao, Yang Li, Chao Bian
Institutions	State Key Laboratory of Transducer Technology, Aerospace Information Research Institute
Citations	4
Analysis	Full AI Review Included

Executive Summary

The research details the development of a highly stable and wide-range electrochemical sensor for nitrate detection, leveraging a Copper (Cu)-modified Boron-Doped Diamond (BDD) electrode.

Core Value Proposition: The sensor combines the catalytic effect of Cu with the exceptional stability and antifouling properties of BDD, enabling reliable, high-frequency monitoring of nitrate-polluted waters.
Wide Detection Range: Achieved a broad linear detection range from 0.07 mg/L up to 100 mg/L, making it suitable for both low-level compliance checks and highly contaminated samples.
High Stability: Demonstrated excellent durability, recording a Relative Standard Deviation (RSD) of only 1.03% over 25 consecutive tests in a 10 mg/L nitrate solution.
Low Detection Limit (LOD): The sensor achieved a low LOD of 0.065 mg/L, meeting stringent environmental monitoring requirements.
Electrode Renewal: The BDD substrate allows for electrochemical renewal (cleaning) by applying a positive voltage, stripping contaminants and modified copper, thus extending the sensor’s lifespan and reusability.
Selectivity: The sensor exhibited good anti-interference ability, with current response deviations of less than 9% even when interfering ions were present at 10-fold the nitrate concentration.

Technical Specifications

Parameter	Value	Unit	Context
Electrode Material	Cu-modified BDD	N/A	Working Electrode
Linear Detection Range (Segment 1)	0.07 - 3	mg/L	Low concentration range
Linear Detection Range (Segment 2)	3 - 100	mg/L	High concentration range
Limit of Detection (LOD)	0.065	mg/L	Calculated (4600 nM)
Sensitivity (Low Conc.)	3.5	µA·mg·L^-1	0.07-3 mg/L range
Sensitivity (High Conc.)	5.33	µA·mg·L^-1	3-100 mg/L range
Stability (RSD)	1.03	%	25 consecutive tests (10 mg/L NO₃^-)
Long-Term Stability	2.02	%	RSD after 7 days (5 mg/L NO₃^-)
Optimal Electrolyte pH	1.5	N/A	Adjusted using H₂SO₄
Optimal Electrolyte Concentration	100	mM	Na₂SO₄ concentration
Cu Modification Solution	0.15	mol/L	CuSO₄ solution (pH 1)
Cu Modification Cycles	10	cycles	Cyclic Voltammetry (CV)
Detection Method	Linear Sweep Voltammetry (LSV)	N/A	Scan rate: 50 mV/s

Key Methodologies

BDD Electrode Fabrication: Boron-doped diamond films were prepared on silicon wafers using Chemical Vapor Deposition (CVD), then diced into 3 mm diameter electrodes.
Electrode Pretreatment: Electrodes were cleaned via sequential ultrasonic treatment (acetone, ethanol, deionized water, 5 min each).
Electrode Activation: Organic contaminants were removed by applying a +3 V voltage for 120 s in 0.5 mol/L H₂SO₄, followed by CV scanning from -3 V to +3 V at 50 mV/s.
Copper Modification: Copper clusters were deposited onto the BDD surface using Cyclic Voltammetry (CV). The process involved 10 cycles of scanning from 0 V to -0.8 V at a scan rate of 50 mV/s, utilizing a 0.15 mol/L CuSO₄ solution (pH 1).
Electrolyte Optimization: The detection electrolyte was optimized to 100 mM Na₂SO₄ (to maximize ionic strength and reduction current) and adjusted to pH 1.5 (using H₂SO₄, balancing nitrate reduction promotion against hydrogen evolution interference).
Nitrate Detection: Linear Sweep Voltammetry (LSV) was performed in a three-electrode setup. The scan voltage range was -0.8 V to -0.1 V at 50 mV/s, recording the reduction peak current proportional to the nitrate concentration.
Electrochemical Renewal: The electrode surface can be renewed by applying a positive voltage to strip the modified copper and contaminants, allowing for reuse of the BDD substrate.

Commercial Applications

The wide detection range (0.07-100 mg/L) and high stability (RSD 1.03%) make this sensor ideal for robust, field-deployable monitoring systems.

Wastewater and Effluent Monitoring: Suitable for continuous monitoring of industrial and municipal wastewater streams where nitrate concentrations can fluctuate widely and often exceed 50 mg/L.
Agricultural Water Quality: On-site monitoring of agricultural runoff and drainage ditches to track fertilizer leaching, benefiting from the sensor’s stability and resistance to fouling.
Groundwater and Surface Water Assessment: Real-time, high-frequency monitoring of rivers, lakes, and aquifers, particularly in areas known for severe nitrate pollution.
Process Control Systems: Integration into automated water treatment plants (e.g., denitrification processes) requiring reliable, long-term sensors that can be easily renewed in situ.
High-End Sensor Manufacturing: The use of BDD as a substrate provides a foundation for highly corrosion-resistant and robust sensor platforms, suitable for harsh chemical environments.

View Original Abstract

This paper describes an electrochemical sensor based on a Cu-modified boron-doped diamond (BDD) electrode for the detection of nitrate-contaminated water. The sensor utilizes the catalytic effect of copper on nitrate and the stability of the BDD electrode. By optimizing the electrolyte system, the linear detection range was expanded, allowing the sensor to detect highly concentrated nitrate samples up to 100 mg/L with a low detection limit of 0.065 mg/L. Additionally, the stability of the sensor was improved. The relative standard deviation of the current responses during 25 consecutive tests was only 1.03%. The wide detection range and high stability of the sensor makes it suitable for field applications and the on-site monitoring of nitrate-contaminated waters.

Tech Support

Original Source

DOI: https://doi.org/10.3390/mi15040487

References

2019 - Spatial groundwater quality and potential health risks due to nitrate ingestion through drinking water: A case study in Yan’an City on the Loess Plateau of northwest China [Crossref]
2024 - Source-specific nitrate and nitrite intakes and associations with sociodemographic factors in the Danish Diet Cancer and Health cohort [Crossref]
2015 - Urgent need to reevaluate the latest World Health Organization guidelines for toxic inorganic substances in drinking water [Crossref]
2017 - Determining sources of nitrate in the semi-arid Rio Grande using nitrogen and oxygen isotopes [Crossref]
2016 - Managing Groundwater Nitrate Contamination from Livestock Farms: Implication for Nitrate Management Guidelines [Crossref]