Preparation of boron-doped diamond microelectrodes to determine the distribution size of platinum nanoparticles using current transient method
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2023-06-29 |
| Journal | Environmental and Materials |
| Authors | T. A. Ivandini Aliyah, Reza Rizqi Nurhidayat, Afiten R. Sanjaya, Rahmat Wibowo, Yasuaki Einaga |
| Institutions | Keio University, University of Indonesia |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis study successfully developed and characterized boron-doped diamond (BDD) microelectrodes for the rapid, low-noise electrochemical screening of platinum nanoparticle (Pt NP) size distribution using the current transient method (chronoamperometry).
- Core Achievement: BDD microelectrodes (25 ”m diameter) were synthesized via Microwave Plasma-Assisted Chemical Vapor Deposition (MPACVD) on tungsten needles.
- Methodology: The size distribution of colloidal Pt NPs (4.46-4.78 nm average diameter) was determined by measuring current transients generated during the electrocatalytic oxidation of hydrazine (15 mM) upon single NP collision.
- Superior Noise Performance: BDD electrodes exhibited a significantly low background noise level of 0.15 nA, demonstrating superior stability compared to Au microelectrodes (~1 nA).
- Correlation with TEM: The observed current transients (5-6 nA for BDD) correlated strongly with the most frequently observed particle sizes determined by Transmission Electron Microscopy (TEM).
- Electrode Stability: The BDD materialâs semiconductor properties and sp3 bonding minimized adsorption and reduction processes, resulting in stable current transients and lower background current.
- Value Proposition: The prepared BDD microelectrode is highly promising for accurately and affordably screening the size distribution of nanoparticles, particularly Pt NPs, offering a robust alternative to conventional metal electrodes.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| BDD Microelectrode Diameter | 25 | ”m | Final insulated electrode size |
| Tungsten Needle Substrate Diameter | 20 | ”m | Substrate for BDD growth |
| BDD Crystalline Size (Average) | ~5 | ”m | Determined by SEM analysis |
| MPACVD Plasma Power | 2500 | W | BDD deposition process |
| BDD Deposition Time | 10 | h | BDD film growth duration |
| Hydrazine Concentration | 15 | mM | Reactant concentration in PBS |
| Electrolyte pH (PBS) | 7.4 | - | Electrochemical measurement condition |
| Applied Potential (CA) | +0.4 | V | vs Ag/AgCl, optimal for hydrazine oxidation |
| BDD Background Noise Level | 0.15 | nA | Measured during CA, low noise performance |
| Au Background Noise Level | ~1 | nA | Measured during CA, comparison electrode |
| Pt NP Size (90 mM NaBH4) | 4.46 | nm | Average diameter (TEM) |
| Pt NP Size (60 mM NaBH4) | 4.78 | nm | Average diameter (TEM) |
| BDD Transient Current (90 mM NPs) | 5-6 | nA | Corresponds to 3.45 nm NPs (TEM) |
| Au Transient Current (60 mM NPs) | 20 | nA | Corresponds to 5.17 nm NPs (TEM) |
| Raman Diamond Peak | ~1300 | cm-1 | C-C sp3 bond characteristic |
| XPS C 1s Peak | 287.5 | eV | C-C and C-H bonds at BDD terminal |
Key Methodologies
Section titled âKey MethodologiesâThe experimental procedure involved three main stages: BDD microelectrode fabrication, Pt nanoparticle synthesis, and electrochemical characterization.
1. BDD Microelectrode Fabrication (MPACVD)
Section titled â1. BDD Microelectrode Fabrication (MPACVD)â- Substrate Preparation: Tungsten needles (20 ”m diameter) were used as the substrate.
- Seeding: Needles were ultrasonicated for 1.5 h in a suspension of nanodiamond particles in 2-propanol.
- Deposition: Polycrystalline BDD was deposited using Microwave Plasma-Assisted Chemical Vapor Deposition (MPACVD) (ASTeX Corp.).
- Plasma Power: 2500 W.
- Duration: 10 h.
- Precursor Solution: Acetone and Trimethoxyborane (50:4 v/v ratio).
- Insulation: The BDD-coated needle was insulated by filling a pre-pulled glass capillary with epoxy, followed by incubation at 60 °C overnight.
- Characterization: Film quality was assessed using Raman spectroscopy (confirming C-C sp3 bonds) and surface termination via X-ray Photoelectron Spectroscopy (XPS).
2. Pt Nanoparticle (NP) Synthesis
Section titled â2. Pt Nanoparticle (NP) Synthesisâ- Precursors: 15 mL of 2 mM H2PtCl6 solution.
- Capping Agent: 0.75 mL of 50 mM Na3C6H5O7 (sodium citrate) was added to stabilize the colloidal solution and control particle growth.
- Reduction: 0.3 mL of fresh NaBH4 (60 mM or 90 mM concentrations) was added dropwise under vigorous magnetic stirring for 30 min.
- NP Characterization: Particle size and morphology were confirmed using UV-Vis spectroscopy and Transmission Electron Microscopy (TEM-EDX).
3. Electrochemical Measurements
Section titled â3. Electrochemical Measurementsâ- Setup: Three-electrode cell using a potentiostat (ALS/HCH Instruments).
- Working Electrodes: BDD, Au (25 ”m), or Pt (20 ”m) microelectrodes.
- Reference Electrode: Ag/AgCl.
- Counter Electrode: Pt spiral.
- Electrolyte: 15 mM Hydrazine in 50 mM Phosphate Buffer Solution (PBS) pH 7.4.
- Techniques:
- Cyclic Voltammetry (CV): Used to determine the optimal oxidation potential (+0.4 V vs Ag/AgCl).
- Chronoamperometry (CA): Used to observe current transients resulting from single Pt NP collision and electrocatalytic amplification of hydrazine oxidation.
- Procedure: 1.0 mL of colloidal Pt NPs solution was injected into the cell, and CA was performed at +0.4 V.
Commercial Applications
Section titled âCommercial ApplicationsâThe development of stable, low-noise BDD microelectrodes for single nanoparticle analysis has significant implications across several high-tech engineering and research sectors:
- Catalyst Development and Screening:
- Rapid, high-throughput screening of size distribution for precious metal catalysts (Pt, Pd, Au) used in industrial chemical processes and hydrogenation reactions.
- Quality control (QC) for optimizing synthesis parameters to ensure uniform nanoparticle size, which directly impacts catalytic efficiency and longevity.
- Fuel Cell and Energy Storage:
- Monitoring the degradation and size evolution of Pt catalysts in Proton Exchange Membrane Fuel Cells (PEMFCs), crucial for improving durability and reducing cost.
- Environmental and Biomedical Sensing:
- Development of highly sensitive, chemically inert electrochemical sensors for detecting trace metal ions or nanoparticles in complex biological fluids or environmental samples.
- Applications in biochemical oxygen demand (BOD) sensors and detection of neurochemicals (e.g., dopamine), leveraging BDDâs wide potential window and low background current.
- Nanomaterials Manufacturing QC:
- In-line quality assurance for industrial production of colloidal nanoparticles, providing a faster, more cost-effective alternative to electron microscopy techniques (TEM/SEM) for size verification.
- Advanced Electrochemistry Research:
- Providing a stable platform for studying fundamental single-entity electrochemistry, including electron transfer kinetics and collision dynamics, without interference from high background noise typical of metal electrodes.
View Original Abstract
Boron-doped diamond (BDD) microelectrodes were prepared to investigate the correlation of hydrazine oxidation current responses with Pt nanoparticle (Pt NP) size distribution. The BDD film was grown on the surface of a tungsten needle with a diameter of 25 ”m. An average particle size of around 5 ”m BDD crystalline was successfully synthesized using a microwave plasma-assisted chemical vapor deposition technique. The Raman spectrum confirmed the presence of diamond formation as indicated by peaks corresponding to C-C sp3 bonds, while X-ray photoelectron spectroscopy spectrum showed the presence of C-H and C-OH bonds on the surface of the BDD microelectrode. Meanwhile the Pt nanoparticles was synthesized through reduction reaction of PtCl62- solution using NaBH4 with citric acid as the capping agent. Particles size between 4.46 to 4.78 nm were observed by using TEM measurements. The BDD microelectrodes were utilized to investigate the relationship between Pt nanoparticle size distribution and the current generated from the oxidation reaction of 15 mM hydrazine in a 50 mM phosphate buffer solution pH 7.4 in the presence of 1.0 mL nanoparticle solutions. A current range of 5 and 6 nA with a noise level of 0.15 nA was observed showing a good correlation with the particle sizes of Pt NPs. Comparison was also performed with the measurements using Au microelectrodes, indicated that the prepared BDD microelectrodes is promising for the measurements of nanoparticle sizes distribution, especially Pt NPs.