Effect of Carbon Layer Thickness on the Electrocatalytic Oxidation of Glucose in a Ni/BDD Composite Electrode

At a Glance

Metadata	Details
Publication Date	2023-08-01
Journal	Molecules
Authors	Hangyu Long, Kui Wen, Cuiyin Liu, Xuezhang Liu, Huawen Hu
Institutions	Jiangxi Science and Technology Normal University, Guangdong Institute of New Materials
Citations	2
Analysis	Full AI Review Included

Executive Summary

This study investigates the precise control of the precipitated carbon layer thickness on Nickel/Boron-Doped Diamond (Ni/BDD) composite electrodes to optimize non-enzymatic glucose sensing performance.

Core Innovation: A thermal catalytic etching method was used to embed Ni nanoparticles into BDD, followed by controlled oxygen plasma etching (200 W and 400 W) to tune the thickness of the resulting graphitic carbon layer.
Performance Optimization: The electrode etched under 200 W exhibited the best electrocatalytic performance, significantly surpassing the untreated (thickest carbon) and 400 W (thinnest carbon) samples.
Key Mechanism: The optimal carbon layer thickness (200 W etch) enhances glucose diffusion channels, maximizes the exposure of active Ni/C interfacial sites, and improves charge transfer kinetics.
Sensitivity Achieved: The optimal 200 W electrode demonstrated a high sensitivity of 1443.75 µA cm^-2 mM^-1 in the low concentration range (0-2 mM).
Detection Limit: The lowest limit of detection (LOD) achieved was 0.5 µM, confirming superior sensing capability compared to many reported Ni-based sensors.
Interfacial Stability: The thermal catalytic etching process ensures strong interfacial adhesion between Ni and BDD, resolving stability issues common with electrodeposited Ni nanoparticles.

Technical Specifications

Parameter	Value	Unit	Context
Optimal Sensitivity (Low Range)	1443.75	µA mM^-1 cm^-2	200 W etched electrode (0-2 mM)
Optimal Sensitivity (High Range)	831.25	µA mM^-1 cm^-2	200 W etched electrode (2-12.8 mM)
Optimal Limit of Detection (LOD)	0.5	µM	200 W etched electrode (S/N = 3)
BDD Deposition Temperature	750	°C	Hot Filament Chemical Vapor Deposition (HFCVD)
Ni Film Thickness (Sputtered)	~20	nm	Before thermal treatment
Thermal Catalytic Treatment Temp.	700	°C	Annealing in H₂ for 30 min
Oxygen Plasma Etching Powers	200, 400	W	Used for carbon layer thickness control (5 min duration)
BDD Growth Pressure	3	kPa	HFCVD process
Electrochemical Testing Potential	0.5	V	Amperometric measurement
BDD Characteristic Raman Peaks	500, 1200	cm^-1	Boron doping confirmation
Graphite Characteristic Raman Peaks	1350 (D), 1580 (G)	cm^-1	Precipitated sp² carbon phases

Key Methodologies

The Ni/BDD composite electrodes were fabricated using a four-step process involving HFCVD, sputtering, thermal catalytic etching, and controlled oxygen plasma etching.

BDD Film Deposition:
- P-type heavily doped silicon substrates were seeded with nanodiamond suspension.
- BDD film was deposited via HFCVD at 750 °C and 3 kPa for 8 h.
- Precursor gases: H₂ (49 sccm), CH₄ (1 sccm), and B₂H₆ (0.2 sccm).
Ni Film Sputtering:
- A nano-thick (approximately 20 nm) Ni film was deposited onto the BDD surface.
- Method: DC magnetron sputtering (150 W power, 0.5 Pa pressure, Ar gas).
Thermal Catalytic Etching (Formation of Untreated Electrode):
- The Ni/BDD sample was annealed in a tubular furnace at 700 °C for 30 min under H₂ (100 sccm) at 10 kPa.
- This process embeds Ni into the BDD (strong adhesion) and precipitates a thick graphitic carbon layer (the “untreated” sample).
Carbon Layer Thickness Control (Oxygen Plasma Etching):
- The thermally treated samples were subjected to oxygen plasma etching for 5 min.
- Etching powers used: 200 W (mild etch) and 400 W (strong etch).
Electrochemical Testing:
- Pretreatment: 100 cycles of CV in 0.5 M NaOH (0.2 to 0.6 V) to form a stable Ni(OH)₂/NiOOH layer.
- Measurement: Cyclic Voltammetry (CV) and Amperometry (at 0.5 V applied potential) in 0.5 M NaOH electrolyte with varying glucose concentrations.

Commercial Applications

The developed Ni/BDD composite electrode technology, characterized by high sensitivity, low LOD, and robust interfacial stability, is highly relevant for advanced electrochemical sensing platforms.

Medical and Biological Sensing:
- High-performance, non-enzymatic glucose sensors for real-time monitoring of blood glucose levels (diabetes management).
- Durable biosensors for continuous monitoring in biological fluids (e.g., sweat, tears).
Advanced Electrochemical Platforms:
- Fabrication of highly stable electrodes for general electrocatalysis and electroanalysis of small molecules beyond glucose.
- Sensors requiring high resistance to poisoning and corrosion, leveraging BDD’s inherent stability.
Diamond-Based Electronics and Materials:
- Integration of Ni/C nanoclusters onto BDD for enhanced conductivity and catalytic activity in harsh chemical environments.
- Development of composite electrode materials with strong metal-carbon-diamond interfacial adhesion for long-term industrial use.

View Original Abstract

High-performance non-enzymatic glucose sensor composite electrodes were prepared by loading Ni onto a boron-doped diamond (BDD) film surface through a thermal catalytic etching method. A carbon precipitate with a desired thickness could be formed on the Ni/BDD composite electrode surface by tuning the processing conditions. A systematic study regarding the influence of the precipitated carbon layer thickness on the electrocatalytic oxidation of glucose was conducted. While an oxygen plasma was used to etch the precipitated carbon, Ni/BDD-based composite electrodes with the precipitated carbon layers of different thicknesses could be obtained by controlling the oxygen plasma power. These Ni/BDD electrodes were characterized by SEM microscopies, Raman and XPS spectroscopies, and electrochemical tests. The results showed that the carbon layer thickness exerted a significant impact on the resulting electrocatalytic performance. The electrode etched under 200 W power exhibited the best performance, followed by the untreated electrode and the electrode etched under 400 W power with the worst performance. Specifically, the electrode etched under 200 W was demonstrated to possess the highest sensitivity of 1443.75 μA cm−2 mM−1 and the lowest detection limit of 0.5 μM.

Tech Support

Original Source

DOI: https://doi.org/10.3390/molecules28155798

References

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