Toward Hyperpolarization of Oil Molecules via Single Nitrogen Vacancy Centers in Diamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2018-02-22 |
| Journal | Nano Letters |
| Authors | P. FernĂĄndez-Acebal, Oded Rosolio, Jochen Scheuer, Christoph MĂŒller, S MĂŒller |
| Institutions | UniversitÀt Ulm, Center for Integrated Quantum Science and Technology |
| Citations | 67 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Towards Hyperpolarization of Oil Molecules via Nitrogen-Vacancy Centers in Diamond
Section titled âTechnical Documentation & Analysis: Towards Hyperpolarization of Oil Molecules via Nitrogen-Vacancy Centers in DiamondâThis document analyzes the requirements and achievements of the research paper focusing on NV-center mediated Dynamic Nuclear Polarization (DNP) and connects them directly to 6CCVDâs advanced MPCVD diamond capabilities.
Executive Summary
Section titled âExecutive SummaryâThis research validates a novel, highly efficient method for achieving nuclear hyperpolarization in diffusive organic molecules (oil) using shallow Nitrogen-Vacancy (NV) centers in diamond, offering a significant advantage over conventional cryogenic DNP methods.
- Room-Temperature DNP: Demonstrated efficient polarization transfer from optically-pumped NV centers to external ÂčH nuclei in oil at ambient temperature, eliminating the need for cryogenic cooling.
- High-Purity Material Requirement: Success relied on ultra-high purity, 12C enriched Single Crystal Diamond (SCD) grown via CVD, featuring extremely low nitrogen concentration (â 5 ppb) to ensure isolated, high-coherence NV centers.
- Shallow NV Engineering: Polarization transfer was optimized using shallow NV centers located 3.2 nm and 5.3 nm beneath the diamond surface, created via low-energy ion implantation (2.5 keV).
- HHDR Protocol: The polarization transfer utilized the Hartmann-Hahn Double Resonance (HHDR) scheme, leveraging continuous dynamical decoupling (CDD) to strengthen the NV-nuclear interaction and weaken environmental noise effects.
- High-Resolution NMR Potential: This technique sets the foundation for achieving high-resolution Nuclear Magnetic Resonance (NMR) and imaging by significantly increasing the signal-to-noise ratio in liquid samples.
- Rapid Dynamics: Polarization loss and transfer dynamics occurred on the microsecond (”s) timescale, confirming the efficiency of the flip-flop mechanism in the high-viscosity oil environment.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the experimental implementation and theoretical modeling:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Diamond Material | Single Crystal Diamond (SCD) | N/A | Grown via CVD, 12C enriched. |
| Carbon Purity | > 99.999% | 12C Enrichment | Used to minimize decoherence sources. |
| Nitrogen Impurity | â 5 | ppb | Ultra-low concentration required for isolated NV centers. |
| NV Implantation Energy | 2.5 | keV | Used for creating shallow NV centers. |
| NV Implantation Dose | 108 | ions/cm2 | Low dose for sparse, single NV centers. |
| Shallow NV Depth (Z0) | 3.2 ± 0.2 and 5.3 ± 0.1 | nm | Two different depths tested for coupling strength. |
| External Magnetic Field (B) | 660 | G | Applied parallel to the NV center axis. |
| 1H Larmor Frequency ($\omega_N / 2\pi$) | 2.8 | MHz | Matched to the Rabi frequency ($\Omega$) for HHDR. |
| Oil Diffusion Coefficient ($D_{oil}$) | â 0.5 | nm2”s-1 | Fluka Analytical 10976 immersion oil (high viscosity). |
| Correlation Time ($\tau_c$) | 10 and 25 | ”s | Calculated for 3.2 nm and 5.3 nm NV depths, respectively. |
| Relaxation Time ($T_{1\rho}$) | 11 and 17 | ”s | Measured relaxation time in the rotating frame. |
| Maximum Achievable Polarization ($P_n$) | â 10-3 | N/A | Estimated maximum polarization per nuclei (exceeds thermal $P_{Th} \approx 10^{-7}$). |
Key Methodologies
Section titled âKey MethodologiesâThe experimental success hinges on precise material engineering and a specialized microwave driving protocol:
- High-Purity Material Synthesis: The diamond substrate was grown using MPCVD, ensuring ultra-high 12C isotopic purity (> 99.999%) and extremely low nitrogen concentration (â 5 ppb) to maximize NV center coherence time.
- Shallow NV Creation: Nitrogen ions were implanted at a low energy (2.5 keV) and low dose (10âž ions/cmÂČ) to position the NV centers within a few nanometers of the surface, maximizing coupling to external molecules.
- Surface Preparation: Immersion oil containing ÂčH nuclei was deposited directly onto the highly polished diamond surface, creating the liquid-solid interface necessary for molecular diffusion and interaction.
- Optical Initialization: Single NV centers were initialized into a highly polarized state (exceeding 92%) using a 532 nm green laser.
- Hartmann-Hahn Double Resonance (HHDR): A microwave field was applied to the NV electron spin, with the Rabi frequency ($\Omega$) tuned precisely to match the ÂčH nuclear Larmor frequency ($\omega_N = 2.8$ MHz at 660 G), enabling resonant flip-flop polarization transfer.
- Polarization Measurement: The NV center polarization loss, indicative of successful transfer to the nuclear bath, was measured via fluorescence signal after a final $\pi/2$ pulse.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research demonstrates the critical role of high-quality, engineered MPCVD diamond in advancing quantum sensing and hyperpolarization techniques. 6CCVD is uniquely positioned to supply the materials required to replicate, scale, and extend this work.
Applicable Materials
Section titled âApplicable MaterialsâTo replicate the high-coherence, low-noise environment necessary for efficient DNP, researchers require Optical Grade Single Crystal Diamond (SCD) with specific isotopic and impurity control.
| Research Requirement | 6CCVD Solution & Specification | Benefit to Researcher |
|---|---|---|
| Ultra-High Purity 12C | Isotopically Enriched SCD | Minimizes spin bath noise (e.g., 13C), maximizing $T_2$ and $T_{1\rho}$ coherence times essential for HHDR protocols. |
| Low Nitrogen Concentration (â 5 ppb) | Optical Grade SCD (Low N) | Ensures isolated, high-quality NV centers suitable for single-spin experiments and high polarization efficiency. |
| Substrate for Implantation | SCD Plates (0.1 ”m to 500 ”m) | Provides the ideal, defect-controlled starting material for precise, shallow ion implantation (2.5 keV). |
Customization Potential
Section titled âCustomization PotentialâThe success of this DNP protocol relies heavily on the quality of the diamond-liquid interface and precise material dimensions. 6CCVD offers extensive customization capabilities:
- Surface Quality: We provide Optical Grade SCD with superior polishing, achieving surface roughness Ra < 1 nm. This ultra-smooth surface is critical for ensuring stable, reproducible contact with the immersion oil and accurate control over the NV-molecule distance ($z_0$).
- Custom Dimensions: While the paper used small samples, 6CCVD can supply SCD plates up to 125 mm in diameter, enabling future scaling of DNP systems or integration into larger NMR setups.
- Thickness Control: We offer precise thickness control for SCD wafers from 0.1 ”m up to 500 ”m, allowing researchers to optimize thermal management and optical access for high-power laser polarization.
- Metalization Services: Although not explicitly used for DNP in this paper, 6CCVD offers in-house metalization (Au, Pt, Pd, Ti, W, Cu) for integrating microwave antennas or microfluidic channels directly onto the diamond surface for advanced DNP/NMR chip designs.
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house PhD team specializes in optimizing diamond material properties for quantum applications. We can assist with material selection for similar NV-based Quantum Sensing and Hyperpolarization projects.
- Recipe Optimization: We consult on the optimal nitrogen concentration and isotopic purity required to balance NV density (for ensemble DNP) versus coherence time (for single-spin DNP).
- Post-Processing Guidance: We provide technical specifications for substrates optimized for subsequent ion implantation and high-temperature annealing processes necessary to activate shallow NV centers.
- Global Logistics: We ensure reliable, global shipping (DDU default, DDP available) of sensitive, high-purity diamond materials directly to your research facility.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Efficient polarization of organic molecules is of extraordinary relevance when performing nuclear magnetic resonance (NMR) and imaging. Commercially available routes to dynamical nuclear polarization (DNP) work at extremely low temperatures, relying on the solidification of organic samples and thus bringing the molecules out of their ambient thermal conditions. In this work, we investigate polarization transfer from optically pumped nitrogen vacancy centers in diamond to external molecules at room temperature. This polarization transfer is described by both an extensive analytical analysis and numerical simulations based on spin bath bosonization and is supported by experimental data in excellent agreement. These results set the route to hyperpolarization of diffusive molecules in different scenarios and consequently, due to an increased signal, to high-resolution NMR.