Atomic Force Microscopy (AFM) Tip based Nanoelectrode with Hydrogel Electrolyte and Application to Single-Nanoparticle Electrochemistry
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2024-02-23 |
| Journal | Journal of Electrochemical Science and Technology |
| Authors | Kyungsoon Park, Thanh Duc Dinh, Seongpil Hwang |
| Institutions | Korea University, Jeju National University |
| Citations | 2 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: AFM Tip-Based Nanoelectrodes using BDD Diamond
Section titled âTechnical Documentation & Analysis: AFM Tip-Based Nanoelectrodes using BDD DiamondâExecutive Summary
Section titled âExecutive SummaryâThis research successfully demonstrates a facile, cost-effective method for fabricating nanoelectrodes by leveraging the precise control of Atomic Force Microscopy (AFM) coupled with a Boron-Doped Diamond (BDD) tip and a solid agarose hydrogel electrolyte.
- Core Innovation: Nanoelectrode fabrication achieved by controlling the nanometer-sized contact area between a conductive BDD AFM tip and a hydrogel electrolyte via AFM non-contact mode set points.
- Material Advantage: BDD was selected for its outstanding electrochemical characteristics and mechanical properties, overcoming limitations associated with conventional ultramicroelectrode (UME) fabrication techniques.
- Scalable Control: The electroactive area was precisely controlled, yielding estimated nanoelectrode heights ranging from 54.8 nm to 231.6 nm, demonstrating radial diffusion characteristics typical of ultramicroelectrodes.
- Single-Nanoparticle Application: The platform was successfully used for the electrochemical deposition and subsequent electrocatalytic characterization of single copper (Cu) nanoparticles.
- Electrocatalysis Confirmed: The Cu-modified BDD tip confirmed two-step consecutive nitrate reduction, highlighting the platformâs utility for studying single-nanoparticle activity.
- 6CCVD Value Proposition: 6CCVD specializes in high-quality BDD diamond substrates, providing the foundational material necessary for replicating and scaling this advanced nanoelectrode technology.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the research detailing the materials and performance metrics of the BDD nanoelectrode platform.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Electrode Material | Boron-Doped Diamond (BDD) | N/A | Conductive AFM Tip |
| Electrolyte Medium | Agarose Hydrogel | 8.3 wt% | Quasi-solid electrolyte |
| Redox Probe | Ferrocenemethanol (FcMeOH) | 1.0 mM | Used for CV characterization |
| Supporting Electrolyte | Potassium Chloride (KCl) | 1.0 M | Used for FcMeOH studies |
| Estimated Nanoelectrode Height (a) | 54.8 | nm | Corresponds to 4 nm AFM set point |
| Estimated Nanoelectrode Height (a) | 231.6 | nm | Corresponds to 6 nm AFM set point |
| Steady-State Current (iss) | ca. 2 | pA | Observed at 12 nm set point |
| Cu Nanoparticle Morphology (1 nm set point) | Urchin-like spikes | ca. 100 nm | Spike width |
| Cu Nanoparticle Morphology (13 nm set point) | Nanorod | 90 nm (W) x 200 nm (L) | Width and Length |
| Nitrate Reduction Potential (First Stage) | -0.83 | V | vs. Ag/AgCl quasi-reference electrode |
| CV Scan Rate (Electrocatalysis) | 0.05 | V/s | Used for Cu deposition and nitrate reduction |
Key Methodologies
Section titled âKey MethodologiesâThe fabrication and characterization of the BDD nanoelectrode relied on precise control of the AFM non-contact mode interaction with the hydrogel medium.
- Hydrogel Preparation: Agarose (8.3 wt%) solution was prepared, heated (700 W microwave for 30 s), cooled overnight, and cut into pads.
- Electrolyte Soaking: Agarose pads were soaked for 8 hours in an aqueous electrolyte containing redox molecules (1.0 mM FcMeOH) and supporting electrolyte (1.0 M KCl) to achieve equilibrium.
- Nanoelectrode Fabrication (AFM Control): A BDD-coated AFM tip (working electrode) was brought into contact with the agarose hydrogel (electrolyte/substrate) using the AFM non-contact mode.
- Area Control: The electroactive contact area (and thus the nanoelectrode size) was precisely governed by adjusting the oscillation amplitude set point of the AFM controller. Lower set points resulted in closer contact and larger electroactive areas.
- Electrochemical Characterization: Cyclic Voltammetry (CV) was performed using the BDD tip (WE), Pt wire (CE), and Ag/AgCl wire (quasi-RE) positioned within the hydrogel.
- Single-Nanoparticle Deposition: Cu nanoparticles were electrochemically deposited onto the BDD tip apex using CV in a solution containing 0.5 M H2SO4, 50 mM CuSO4, and 0.1 M K2SO4.
- Morphology Analysis: The deposited Cu nanoparticles were characterized using Field Emission-Scanning Electron Microscopy (FE-SEM).
- Electrocatalytic Testing: The Cu-modified BDD tip was tested for nitrate reduction activity using linear sweep voltammetry in the presence of varying concentrations of KNO3.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD is uniquely positioned to support and advance research utilizing diamond nanoelectrodes, providing high-purity, custom-engineered MPCVD diamond materials that meet the stringent requirements of AFM-based electrochemistry.
Applicable Materials
Section titled âApplicable MaterialsâThe success of this research hinges on the use of Boron-Doped Diamond (BDD) due to its wide potential window, chemical inertness, and mechanical robustness.
| 6CCVD Material | Relevance to Research | Customization Potential |
|---|---|---|
| Heavy Boron-Doped Diamond (BDD) | Direct replacement/source for the conductive material. We supply BDD plates/wafers with tunable doping levels for optimal conductivity and electrochemical performance. | Custom doping concentrations (e.g., 1020 atoms/cm3) and thicknesses (0.1 ”m to 500 ”m). |
| Electronic Grade Single Crystal Diamond (SCD) | Ideal substrate material for subsequent deposition of conductive films (Au, Pt, Carbon) mentioned in the paper, offering superior thermal management and structural integrity. | Plates up to 10x10 mm, polished to Ra < 1 nm for ultra-smooth surface quality, critical for nanoscale contact studies. |
| Polycrystalline Diamond (PCD) | Cost-effective alternative for larger area macroelectrodes or substrates up to 125 mm in diameter, suitable for scaling up related electrocatalysis studies. | Custom dimensions up to 125 mm, polished to Ra < 5 nm. |
Customization Potential
Section titled âCustomization Potentialâ6CCVDâs in-house engineering capabilities directly address the need for precise material specifications required for advanced nanoelectrode fabrication:
- Custom Dimensions: While the paper used commercial AFM tips, 6CCVD can supply BDD wafers/plates up to 125 mm (PCD) or 10x10 mm (SCD) for researchers developing custom microelectrode arrays or specialized AFM cantilever structures.
- Advanced Metalization Services: The paper noted that alternative electrode materials (Au, Pt, Carbon) could be used. 6CCVD offers internal metalization capabilities (Au, Pt, Pd, Ti, W, Cu) directly onto diamond substrates, allowing researchers to test the electrocatalytic activity of various metal/diamond interfaces.
- Surface Preparation: Achieving stable, controlled contact at the nanometer scale (as demonstrated by the 4 nm set point) requires extremely flat surfaces. 6CCVD guarantees ultra-low roughness polishing (Ra < 1 nm for SCD), ensuring optimal surface quality for subsequent nanoscale deposition and AFM contact experiments.
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house PhD team provides expert consultation on material selection and optimization for complex electrochemical systems. We can assist researchers in:
- Doping Optimization: Selecting the precise boron doping level in BDD required to balance conductivity and electrochemical stability for specific applications like single-nanoparticle electrocatalysis or sensing.
- Interface Engineering: Designing custom metalization stacks (e.g., Ti/Pt/Au) on diamond substrates to enhance adhesion and electrical contact for novel nanoelectrode designs.
- Scaling Research: Transitioning successful nanoelectrode concepts to larger microelectrode arrays or macroelectrodes using our large-area PCD capabilities.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
<p>An unconventional fabrication technique of nanoelectrode was developed using atomic force microscopy (AFM) and hydrogel. Until now, the precise control of electroactive area down to a few nm<sup>2</sup> has always been an obstacle, which limits the wide application of nanoelectrodes. Here, the nanometer-sized contact between the boron-doped diamond (BDD) as conductive AFM tip and the agarose hydrogel as solid electrolyte was well governed by the feedback amplitude of oscillation in the non-contact mode of AFM. Consequently, this low-cost and feasible approach gives rise to new possibilities for the fabrication of nanoelectrodes. The electroactive area controlled by the set point of AFM was investigated by cyclic voltammetry (CV) of the ferrocenmethanol (FcMeOH) combined with quasi-solid agarose hydrogel as an electrolyte. Single copper (Cu) nanoparticle was deposited at the apex of the AFM tip using this platform whose electrocatalytic activity for nitrate reduction was then investigated by CV and Field Emission-Scanning Electron Microscopy (FE-SEM), respectively.</p>