Modulation of nitrogen vacancy charge state and fluorescence in nanodiamonds using electrochemical potential
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2016-03-24 |
| Journal | Proceedings of the National Academy of Sciences |
| Authors | Sinan Karaveli, Ophir Gaathon, Abraham Wolcott, Reyu Sakakibara, Or A. Shemesh |
| Institutions | McGovern Institute for Brain Research, Massachusetts Institute of Technology |
| Citations | 106 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: NV Charge State Modulation via Electrochemical Potential
Section titled âTechnical Documentation & Analysis: NV Charge State Modulation via Electrochemical PotentialâReference: Karaveli et al., Modulation of nitrogen vacancy charge state and fluorescence in nanodiamonds using electrochemical potential, PNAS (2016).
Executive Summary
Section titled âExecutive SummaryâThis research demonstrates precise, voltage-dependent control over the Nitrogen Vacancy (NV) center charge state ($NV^0$ and $NV^-$) and fluorescence dynamics in nanodiamonds (NDs) using an electrochemical cell setup. This capability is critical for advancing quantum sensing and biological voltage imaging.
- Core Achievement: Successful modulation of NV fluorescence by applying small potential differences (down to 20 mV) across NDs in an aqueous electrolyte.
- Mechanism Dependence: The charge state switching mechanism is strongly dependent on surface termination: Hydroxylated NDs rely on electric field-induced band bending ($NV^0 \leftrightarrow NV^-$), while Hydrogenated NDs rely on charge transfer ($NV^0 \leftrightarrow NV^+$ dark state).
- High Sensitivity: Single NV centers in hydroxylated NDs showed clear fluorescence modulation for potential swings of 100 mV, directly relevant to neuronal action potentials.
- Enhanced Performance: Hydrogenated ND clusters achieved detection sensitivity down to 20 mV with a rapid 5 ms temporal response, demonstrating potential for parallel optical detection.
- 6CCVD Value Proposition: The findings validate the necessity of highly controlled diamond material propertiesâspecifically surface termination and defect engineeringâwhich 6CCVD provides via high-purity MPCVD Single Crystal Diamond (SCD) and Polycrystalline Diamond (PCD) wafers.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the experimental results, highlighting the performance metrics achieved in electrochemical NV sensing:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Single NV Sensitivity (Hydroxylated) | 100 | mV | Minimum detectable potential swing |
| Cluster NV Sensitivity (Wide-Field) | 20 | mV | Minimum detectable potential swing (33-ms exposure) |
| Maximum PL Modulation ($\Delta F_{max}/F_{mean}$) | 110 | % | Achieved in Hydrogenated NDs (over ±0.75 V range) |
| Temporal Resolution (Cluster) | 5 | ms | Achievable response time for 100 mV pulses |
| ND Mean Size (Hydroxylated) | 18 ± 8 | nm | HPHT derived nanodiamonds |
| ND Mean Size (Hydrogenated) | 12 ± 5 | nm | HPHT derived nanodiamonds |
| Excitation Wavelength | 532 | nm | Continuous Wave (CW) Laser |
| Electrolyte pH | 7.7 | - | Stabilized using phosphate buffer |
| Applied Voltage Sweep Range ($\Psi_{app}$) | ±0.75 | V | Range used for charge state modulation studies |
| NV Charge State Transition (Hydroxylated) | $NV^0 \leftrightarrow NV^-$ | - | Driven by band bending |
| NV Charge State Transition (Hydrogenated) | $NV^0 \leftrightarrow NV^+$ | - | Driven by charge transfer to dark state |
Key Methodologies
Section titled âKey MethodologiesâThe experiment utilized a three-electrode electrochemical cell setup integrated with high-resolution fluorescence microscopy to monitor NV center dynamics.
- Substrate Preparation: ITO-coated coverslips (30-60 Ω/sq) were cleaned and prepared as the Working Electrode.
- ND Deposition: HPHT-derived nanodiamonds (NDs) were deposited onto the ITO coverslips from aqueous or toluene solutions.
- NV Creation: NDs were irradiated and annealed to induce NV centers.
- Surface Termination: NDs were characterized as either primarily hydroxylated (O-terminated) or hydrogenated (H-terminated).
- Electrochemical Cell Assembly: A cylindrical polypropylene tube was epoxied onto the ITO coverslip, containing the aqueous electrolyte (100 ”M KCl, phosphate buffer, pH 7.7).
- Electrode System: A potentiostat (CH Instruments 630D) was used in a three-electrode configuration:
- Working Electrode: ITO coverslip with NDs.
- Counter Electrode: Platinum (Pt) wire.
- Reference Electrode: Leak-free Ag/AgCl electrode.
- Optical Measurement: Wide-field and confocal fluorescence measurements were performed using a 100x oil objective (NA = 1.4) and 532 nm excitation, with long-pass filters (562 nm or 650 nm) to isolate NV fluorescence.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research highlights the critical role of precise diamond material engineeringâspecifically surface termination and defect controlâfor developing high-performance electrochemical sensors. 6CCVD is uniquely positioned to supply the advanced MPCVD diamond materials necessary to replicate, scale, and extend this work from nanodiamonds to integrated thin-film devices.
Applicable Materials
Section titled âApplicable MaterialsâTo transition this proof-of-concept from NDs to robust, integrated sensing platforms, high-quality Single Crystal Diamond (SCD) or thin-film Polycrystalline Diamond (PCD) is required.
| Research Requirement | 6CCVD Material Solution | Rationale |
|---|---|---|
| High-Coherence NV Centers | Optical Grade SCD (0.1”m to 500”m) | Provides the lowest defect density substrate for creating stable, near-surface NV centers via controlled implantation and annealing, ensuring maximum spin coherence time. |
| Integrated Electrodes/Sensors | Thin-Film PCD Wafers (up to 125mm) | Offers large-area substrates for scaling up the wide-field imaging approach, enabling parallel detection arrays for biological samples. |
| Conductive Interface/Band Bending | Custom Boron-Doped Diamond (BDD) | BDD films can serve as the conductive working electrode, replacing ITO, offering superior chemical inertness and tunable conductivity for precise Fermi level control, essential for modulating the NV charge state. |
Customization Potential
Section titled âCustomization PotentialâThe electrochemical setup requires precise control over surface chemistry and electrode integration. 6CCVDâs in-house capabilities directly address these needs:
- Surface Termination Control: We provide SCD and PCD wafers with guaranteed surface termination states (e.g., H-terminated for charge transfer mechanisms or O-terminated for electric field-induced band bending) to optimize NV charge state stability and modulation depth.
- Custom Metalization: The experiment utilized ITO and Pt electrodes. 6CCVD offers internal metalization services, including deposition of Ti/Pt/Au, W, or Cu contacts directly onto SCD or PCD surfaces. This enables the fabrication of robust, integrated diamond working electrodes, eliminating the need for external ITO substrates.
- Dimensional Scaling: While the paper used NDs, 6CCVD can supply custom SCD plates up to 10mm thick or PCD wafers up to 125mm in diameter, allowing researchers to move from ND suspensions to stable, thin-film integrated devices.
- Ultra-Low Roughness Polishing: For near-surface NV applications requiring precise control over the electric double layer, 6CCVD guarantees Ra < 1nm polishing on SCD and Ra < 5nm on inch-size PCD wafers.
Engineering Support
Section titled âEngineering SupportâThe successful implementation of NV-based electrochemical sensing relies heavily on optimizing the diamond material recipeâfrom initial growth purity to post-processing surface chemistry. 6CCVDâs in-house PhD team specializes in defect engineering and surface functionalization for quantum applications. We can assist researchers in selecting the optimal material specifications (e.g., nitrogen concentration, implantation depth, and surface termination) required for similar electrochemical voltage sensing or biological potential imaging projects.
Call to Action: For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Significance The nitrogen vacancy center (NV) in diamond is a fluorescent color center that can be in several charge states depending on its local electrostatic environment. Here, we demonstrate the control of the charge state and fluorescence of NVs in nanodiamonds (NDs) by applying a potential difference across NDs in an electrochemical cell. Controlling the charge state can improve spin-based sensing protocols of the NV. Conversely, the NVâs strong fluorescence dependence on electrochemical potential differences also enables a new modality for optical sensing of its environment. With this electrochemical setup, we show that a single NV can reveal a 100-mV potential swing, whereas multiple NVs allow for the detection of potential swings as small as 20 mV.