A Nanograss Boron and Nitrogen Co-Doped Diamond Sensor Produced via High-Temperature Annealing for the Detection of Cadmium Ions

At a Glance

Metadata	Details
Publication Date	2023-11-15
Journal	Nanomaterials
Authors	Xiaoxi Yuan, Yaqi Liang, Mingchao Yang, Shaoheng Cheng, Nan Gao
Institutions	State Key Laboratory of Superhard Materials, Jilin Engineering Normal University
Citations	2
Analysis	Full AI Review Included

Technical Documentation & Analysis: Nanograss B/N Co-Doped Diamond Sensors

Executive Summary

This analysis focuses on the fabrication and performance of a Nanograss Boron and Nitrogen Co-Doped Diamond (NGBND) sensor for highly sensitive electrochemical detection of Cadmium ions (Cd²⁺). The findings validate MPCVD diamond as a superior platform for advanced electrochemical sensing.

Novel Fabrication Route: A simple, cost-effective, and scalable method was developed using Microwave Plasma Chemical Vapor Deposition (MPCVD) co-doping (Boron and Nitrogen) followed by high-temperature annealing (800 °C) to selectively remove non-diamond carbon (NDC), creating the nanograss morphology without complex masks or Reactive Ion Etching (RIE).
Material Advantage: The NGBND electrode leverages the inherent stability and wide electrochemical window of diamond, enhanced by co-doping and nanostructuring to achieve a large specific surface area (8.5 times greater than the composite).
Exceptional Sensitivity: Utilizing Differential Pulse Anodic Stripping Voltammetry (DPASV), the sensor achieved a low detection limit (LOD) of 0.28 µg L^-1 for Cd²⁺, significantly below the WHO drinking water limit (3 µg L^-1).
High Performance Metrics: Demonstrated a wide linear detection range (1 to 100 µg L^-1) and excellent reproducibility (Relative Standard Deviation of 3.1%).
Mechanism Validation: COMSOL simulations confirmed that the sharp nanograss tips (tip radius ~few nanometers) significantly enhance local current density (up to 4.7 times increase), facilitating ion precipitation and boosting low-concentration detection.
Broad Applicability: The NGBND platform shows considerable promise for sensitive detection of other heavy metal ions, biomolecules, and environmental hazards.

Technical Specifications

The following hard data points were extracted from the research paper detailing the material synthesis and performance metrics.

Parameter	Value	Unit	Context
Growth System	Microwave Plasma CVD	2.45	GHz
Substrate Type	p-type Si	N/A	Mirror-polished
Nucleation Method	Ultrasonication in acetone	5	nm nanodiamond powder
Gas Flow Ratio (CH₄/H₂/B/N₂)	20/200/2/1	sccm	Co-doped diamond growth
Growth Time	6	h	NGBND/NDC composite formation
Annealing Temperature	800	°C	NDC removal/NGBND formation
Annealing Time	20	min	In air (etching process)
NGBND Tip Size	Few	nm	Nanograss morphology
Electrode Geometric Area	0.10	cm²	Working electrode size
Detection Limit (LOD)	0.28	µg L^-1	For Cd²⁺ via DPASV (3σ/slope)
Linear Range	1 to 100	µg L^-1	Cd²⁺ concentration
Reproducibility (RSD)	3.1	%	6 repetitive measurements at 100 µg L^-1
Current Density Enhancement	Up to 4.7	Times	Simulated increase (5 nm tip vs. 100 nm tip)
NGBND Conductivity	2 x 10⁴	S m^-1	Used in COMSOL simulation

Key Methodologies

The NGBND electrode fabrication relies on precise control over the MPCVD growth environment to achieve a high concentration of non-diamond carbon (NDC) and subsequent selective removal via thermal etching.

Substrate Preparation: Mirror-polished p-type Si substrates were prepared. Nucleation sites were formed by ultrasonication in an acetone solution containing 5 nm nanodiamond powder for 60 minutes, followed by standard cleaning (acetone, ethanol, purified water) and nitrogen drying.
Co-Doped Diamond Growth (NGBND/NDC Composite): Diamond films were deposited using a 2.45 GHz MPCVD system.
- Gas Sources: Methane (CH₄), Hydrogen (H₂), Trimethyl borate (B(OCH₃)₃) carried by H₂ (Boron source), and Nitrogen (N₂).
- Doping Strategy: High CH₄ concentration (20 sccm) was used to intentionally generate a large amount of NDC. Boron and Nitrogen co-doping (2/1 sccm flow rates, respectively) facilitated secondary nucleation and columnar growth, leading to the formation of the NGBND/NDC composite over 6 hours.
Nanograss Formation via Annealing: The composite film was subjected to high-temperature annealing in a quartz tube at 800 °C for 20 minutes in air. This step selectively etched away the NDC phase, leaving behind the high-surface-area nanograss boron and nitrogen co-doped diamond (NGBND) film.
Electrochemical Testing: The resulting NGBND film served as the working electrode (0.10 cm² geometric area) in a three-electrode system, characterized using Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS), and Differential Pulse Anodic Stripping Voltammetry (DPASV) for Cd²⁺ detection.

6CCVD Solutions & Capabilities

6CCVD is uniquely positioned to supply the advanced MPCVD materials required to replicate, scale, and extend this high-impact research into commercial applications for heavy metal sensing.

Applicable Materials

The core of this research relies on highly controlled, heavily co-doped diamond films. 6CCVD specializes in delivering materials engineered to these exact specifications.

Research Requirement	6CCVD Solution & Material Grade	Technical Advantage
Boron and Nitrogen Co-Doping	Custom Doped PCD/SCD (BDD/NDD)	We offer precise control over B and N incorporation during MPCVD growth, essential for achieving the mixed-growth mode and high conductivity (2 x 10⁴ S m^-1) required for electrochemical activity.
High Roughness/Nanostructuring Precursor	High-Doping Polycrystalline Diamond (PCD)	By controlling the CH₄/H₂ ratio and doping levels, 6CCVD can produce films with high NDC content and specific grain structures, serving as the ideal precursor for the post-growth thermal nanostructuring process (800 °C annealing).
Substrate Compatibility	Diamond on Silicon (Si) Substrates	We routinely grow high-quality SCD and PCD films on Si wafers, providing the necessary foundation for integration into standard semiconductor processing and electrochemical setups.

Customization Potential

The successful implementation of the NGBND sensor requires precise material dimensions and electrode integration, capabilities central to 6CCVD’s service offering.

Custom Dimensions and Scale-Up: The paper used a small 0.10 cm² electrode area. 6CCVD can provide custom plates and wafers up to 125mm (PCD), enabling the scale-up of this sensor technology for industrial or multi-array sensing applications.
Thickness Control: We offer precise thickness control for both SCD and PCD films from 0.1 µm to 500 µm, allowing researchers to optimize film thickness for mechanical stability and electrochemical performance.
Electrode Integration and Metalization: Although the paper focused on the diamond surface, electrochemical sensors often require contact pads. 6CCVD offers in-house custom metalization services, including Ti/Pt/Au, W, Cu, and Pd, ensuring robust electrical contacts and integration into microfluidic or sensor arrays.
Precision Shaping: We provide advanced laser cutting and shaping services to achieve the exact geometric area (e.g., 0.10 cm²) and electrode patterns required for reproducible electrochemical measurements.

Engineering Support

The development of novel nanostructured diamond electrodes, such as NGBND, requires deep expertise in MPCVD growth kinetics and post-processing.

6CCVD’s in-house PhD team specializes in optimizing diamond growth recipes (gas flow, pressure, temperature, doping) to achieve specific morphologies and electrical properties. We can assist researchers and engineers in:

Material Selection: Consulting on the optimal B/N co-doping ratios and substrate choice to maximize the yield and quality of the nanograss structure.
Process Transfer: Assisting with the transfer of the high-CH₄/annealing nanostructuring methodology to larger-area substrates.
Application Extension: Providing material consultation for similar heavy metal detection projects (e.g., Pb²⁺, Zn²⁺, Cu²⁺) or other advanced electrochemical applications leveraging high-surface-area BDD.

Call to Action: For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly. We ship globally (DDU default, DDP available) to support your research needs.

View Original Abstract

The high-performance determination of heavy metal ions (Cd2+) in water sources is significant for the protection of public health and safety. We have developed a novel sensor of nanograss boron and nitrogen co-doped diamond (NGBND) to detect Cd2+ using a simple method without any masks or reactive ion etching. The NGBND electrode is constructed based on the co-doped diamond growth mode and the removal of the non-diamond carbon (NDC) from the NGBND/NDC composite. Both the enlarged surface area and enhanced electrochemical performance of the NGBND film are achievable. Scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and differential pulse anodic stripping voltammetry (DPASV) were used to characterize the NGBND electrodes. Furthermore, we used a finite element numerical method to research the current density near the tip of NGBND. The NGBND sensor exhibits significant advantages for detecting trace Cd2+ via DPASV. A broad linear range of 1 to 100 μg L−1 with a low detection limit of 0.28 μg L−1 was achieved. The successful application of this Cd2+ sensor indicates considerable promise for the sensitive detection of heavy metal ions.

Tech Support

Original Source

DOI: https://doi.org/10.3390/nano13222955

References

2021 - Layer double hydroxides (LDHs)-based electrochemical and optical sensing assessments for quantification and identification of heavy metals in water and environment samples: A review of status and prospects [Crossref]
2022 - Recent developments in electrochemical detection of cadmium [Crossref]
2012 - Fluorescent and colorimetric sensors for detection of lead, cadmium, and mercury ions [Crossref]
1992 - Cadmium in the human environment: Closing remarks
2021 - A smartphone-integrated ratiometric fluorescence sensor for visual detection of cadmium ions [Crossref]
2019 - Recent advances in nanomaterial-enabled screen-printed electrochemical sensors for heavy metal detection [Crossref]
2022 - Water treatment technologies in removing heavy metal ions from wastewater: A review
2018 - Solid-phase extraction of ultra-trace levels of lead using tannic acid-coated graphene oxide as an efficient adsorbent followed by electrothermal atomic absorption spectrometry; response surface methodology-central composite design [Crossref]
2018 - Reference measurements of cadmium and lead contents in candidates for new environmental certified materials by isotope dilution inductively coupled plasma mass spectrometry [Crossref]