Feedback‐amplified electrochemical dual‐plate boron‐doped diamond microtrench detector for flow injection analysis
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2015-03-03 |
| Journal | Electrophoresis |
| Authors | Grace E. M. Lewis, Andrew J. Gross, Barbara Kasprzyk‐Hordern, Anneke Lubben, Frank Marken |
| Institutions | University of Bath |
| Citations | 4 |
| Analysis | Full AI Review Included |
6CCVD Technical Documentation: Feedback-Amplified BDD Microtrench Detectors
Section titled “6CCVD Technical Documentation: Feedback-Amplified BDD Microtrench Detectors”Executive Summary
Section titled “Executive Summary”This research successfully demonstrates a high-performance electrochemical flow cell utilizing a Boron-Doped Diamond (BDD) dual-plate microtrench electrode in a flow injection analysis (FIA) system. The results establish BDD as a chemically robust material for advanced analytical sensing.
- Core Achievement: Sensitivity enhancement by one order of magnitude (10x) achieved through the generator-collector feedback mechanism compared to a single working electrode.
- Mechanism: The operational mode successfully switches the diffusion process from external analyte consumption to internal analyte regeneration (redox cycling) within the microtrench.
- Material: The detector employs thin-film BDD (300 nm thick, 8000 ppm doping) on a silicon substrate prepared via a custom slicing, bonding, and Piranha etching process.
- Critical Geometry: Optimal feedback relies on precise micro-dimensions, specifically a 10 µm interelectrode gap (δ), a 5 mm trench length, and an effective trench depth estimated at 58 µm.
- Application: Demonstrated robust detection of hydroquinone (HQ) in phosphate buffer (pH 7), confirming BDD’s wide potential window and chemical stability are highly beneficial for separation science and robust electroanalysis.
Technical Specifications
Section titled “Technical Specifications”The following table summarizes the critical material and electrochemical parameters demonstrated by the BDD microtrench detector.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Diamond Material | BDD Thin Film | N/A | Boron-Doped Polycrystalline Diamond |
| BDD Film Thickness | 300 | nm | Deposited layer thickness |
| Boron Doping Level | 8000 | ppm | Heavy doping for metallic conductivity |
| Material Resistivity | 10 | MΩ cm | Initial BDD substrate resistivity |
| Substrate Size | 5 x 20 | mm | Custom dimensions for flow cell integration |
| Interelectrode Gap (δ) | 10 | µm | Microtrench width, critical for feedback efficiency |
| Trench Length | 5 | mm | Active electrode length |
| Estimated Trench Depth | 58 | µm | Calculated based on mass transport limiting current (Ilim) |
| Generator Potential (EGen) | 1.0 | V | vs SCE (Oxidation of Hydroquinone) |
| Collector Potential (EColl) | -0.4 | V | vs SCE (Reduction of product) |
| Limiting Feedback Current (Ilim) | 2.8 | µA | Observed for 1 mM HQ at 10 mL/h flow rate |
| Sensitivity Enhancement | 10x (1 order of magnitude) | N/A | Generator-collector mode vs single working electrode |
| Electrolyte | 0.1 M Phosphate Buffer | pH 7 | Used for hydroquinone oxidation studies |
| Operating Temperature | 22 ± 2 | °C | Ambient environment |
Key Methodologies
Section titled “Key Methodologies”The BDD dual-plate microtrench electrodes were fabricated via a complex multi-step process integrating standard micro-fabrication techniques with precise diamond preparation.
- BDD Substrate Preparation: Two separate 5 x 20 mm BDD substrates (300 nm BDD, 8000 ppm doping) with SiO2/Si3N4 interlayer were sourced.
- Photoresist Application: A single layer of SU-8-2002 photoresist was spin-coated onto both substrates (500 rpm for 15 s, then 3000 rpm for 30s).
- Bonding and Curing: The two substrates were pushed together, vis-à-vis (forming the 10 µm trench gap), and thermally cured on a hot plate (90°C for 2 min, followed by ramping to 160°C for 5 min).
- Device Definition: The end of the bonded dual-plate assembly was sliced off using a diamond cutter (Buehler Isomet 1000) and polished flat.
- Trench Etching: The exposed photoresist was etched away using Piranha solution (1:5 v/v H2O2:H2SO4) to define the 58 µm deep microtrench structure.
- Electrochemical Setup: The completed electrode was integrated into an electrochemical flow cell, utilizing a 6-port 2-position switch valve and syringe pump for precise sample injection (20 µL volume) and controlled electrolyte flow (10-25 mL/h).
- Measurement: Bipotentiostatic cyclic voltammetry and chronoamperometry were performed using a PGSTAT12 system to measure the generator and collector currents simultaneously.
6CCVD Solutions & Capabilities: Enabling High-Performance BDD Sensing
Section titled “6CCVD Solutions & Capabilities: Enabling High-Performance BDD Sensing”The fabrication of high-sensitivity BDD electrochemical detectors requires tight control over material properties, specific dimensions, and surface quality. 6CCVD provides the specialized MPCVD diamond materials necessary to replicate, optimize, and scale this advanced generator-collector technology.
Applicable Materials
Section titled “Applicable Materials”To achieve the highly conductive, micro-structured sensing surfaces required for effective redox cycling and feedback amplification, the following 6CCVD materials are ideal:
- Heavy Boron Doped Polycrystalline Diamond (BDD PCD) Thin Films: The research requires thin (300 nm), highly doped BDD for low resistivity and wide electrochemical window. 6CCVD provides BDD PCD films with customizable doping levels and precise thickness control from 0.1 µm up to 500 µm, deposited on standard or custom substrates (e.g., Si, SiO2/Si3N4 systems).
- Bulk BDD Substrates (Substrates up to 10 mm thick): For applications requiring increased structural rigidity or significantly deeper trenches (as suggested for future improvements), 6CCVD can supply bulk BDD, allowing trench depths far exceeding the reported 58 µm, maximizing the diffusion volume and potentially increasing the internal mass transport limiting current (Ipeak, dual-electrode).
Customization Potential
Section titled “Customization Potential”The success of the microtrench detector hinges on precise geometry and surface finish, areas where 6CCVD excels:
- Precision Dimensioning: We offer custom sizing for plates and wafers up to 125 mm (PCD). We can supply the critical 5 mm x 20 mm BDD plates cut with high precision, ready for photoresist application and thermal bonding.
- Ultra-Flat Surfaces: Achieving the uniform 10 µm interelectrode gap (δ) demands exceptional surface quality. 6CCVD guarantees superior polishing, achieving surface roughness Ra < 5 nm on inch-size PCD material, ensuring the necessary interface flatness for reproducible mass transport control.
- Integration Support: We supply BDD materials compatible with standard micro-fabrication techniques, including the Piranha etching process utilized in this paper for trench definition and surface cleaning.
- Custom Metalization: Should the application evolve to require integrated electrical contacts or micro-heater elements, 6CCVD offers in-house deposition of standard metal stacks, including Ti, Pt, Au, and W.
Engineering Support
Section titled “Engineering Support”This dual-plate generator-collector methodology is highly sensitive to geometric parameters ($\delta$, depth, length) and material doping.
6CCVD’s in-house PhD engineering team specializes in MPCVD diamond applications. We offer consultation services to assist researchers and engineers in selecting the optimal BDD specifications (doping concentration and film thickness) required for maximizing the observed 10x feedback amplification for similar flow injection analysis (FIA) and chromatography detection projects. Our expertise ensures materials are optimized for robustness and signal-to-noise ratio in demanding electrochemical environments.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
An electrochemical flow cell with a boron‐doped diamond dual‐plate microtrench electrode has been developed and demonstrated for hydroquinone flow injection electroanalysis in phosphate buffer pH 7. Using the electrochemical generator‐collector feedback detector improves the sensitivity by one order of magnitude (when compared to a single working electrode detector). The diffusion process is switched from an analyte consuming “external” process to an analyte regenerating “internal” process with benefits in selectivity and sensitivity.
Tech Support
Section titled “Tech Support”Original Source
Section titled “Original Source”References
Section titled “References”- 2014 - Electrochemistry: Nanoelectrochemistry