13 C hyperpolarization with nitrogen-vacancy centers in micro- and nanodiamonds for sensitive magnetic resonance applications
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2025-02-28 |
| Journal | Science Advances |
| Authors | Rémi Blinder, Yuliya Mindarava, Martin C. Korzeczek, Alastair Marshall, Felix Glöckler |
| Institutions | UniversitÀt Ulm, Leibniz Institute of Surface Engineering |
| Citations | 7 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: $^{13}$C Hyperpolarization in Diamond Nanoparticles
Section titled âTechnical Documentation & Analysis: $^{13}$C Hyperpolarization in Diamond NanoparticlesâThis document analyzes the research demonstrating room-temperature $^{13}$C hyperpolarization using Nitrogen-Vacancy (NV) centers in micro- and nanodiamonds. It highlights the critical material requirements and connects them directly to 6CCVDâs advanced MPCVD diamond capabilities, positioning 6CCVD as the essential supplier for replicating and advancing this research.
Executive Summary
Section titled âExecutive Summaryâ- Record Room-Temperature Hyperpolarization: Achieved significant $^{13}$C NMR signal enhancements of 1500x (2 ”m particles) and 940x (100 nm particles) over the thermal signal at ambient conditions (0.29 T).
- Material Optimization for T$_{1}$: Demonstrated a sevenfold improvement in the $^{13}$C spin-lattice relaxation time ($^{13}$C T$_{1}$) in nanodiamonds by combining Air Oxidation (AO) and Triacid Cleaning (TAC) surface treatments, mitigating surface magnetic noise.
- Enhanced NV Initialization: Utilized a 3D-printed microphotonic waveguide structure to improve the homogeneity and efficiency of 532 nm green laser illumination in highly scattering diamond powders.
- Optimized DNP Protocol: Employed the robust PulsePol sequence, enhanced by composite pulses (1.3x gain) and slow sample rotation ($\le$ 25°/s, 2x gain), to address orientation-induced spectral broadening and maximize NV involvement.
- Enabling Technology: Successfully established NV-containing nanodiamonds as a viable, cryogen-free platform for generating hyperpolarized $^{13}$C spins, promising future applications in sensitive MRI and NMR.
- Future Material Requirement: The research explicitly points toward the need for high-purity, low-nitrogen CVD diamond to achieve longer T${1}$ lifetimes and higher absolute polarization levels (P${13C}$ > 1%).
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the research paper, summarizing the key physical and performance metrics.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Hyperpolarization Enhancement ($\epsilon_{13C}$) | 1500 | Times | 2 ”m particles |
| Hyperpolarization Enhancement ($\epsilon_{13C}$) | 940 | Times | 100 nm particles |
| Polarization Magnetic Field (B$_{pol}$) | 0.287 | T | DNP/EPR |
| Detection Magnetic Field (B$_{det}$) | 1 | T | NMR Detection |
| $^{13}$C Spin-Lattice Relaxation Time ($^{13}$C T$_{1}$) | 152 $\pm$ 12 | s | 100 nm particles (AO + TAC, measured at 7.05 T) |
| NV Spin-Lattice Relaxation Time (NV T$_{1}$) | 4.23(7) | ms | 100 nm particles (AO + TAC) |
| NV Density (100 nm) | 3.4(2) | ppm | After 10 MeV electron irradiation |
| P1 Density (100 nm) | 18(1) | ppm | Substitutional Nitrogen |
| Electron Irradiation Dose | 3 x 10$^{18}$ | cm-2 | NV creation |
| Annealing Temperature | 800 | °C | NV creation |
| Air Oxidation Temperature | 620 | °C | Graphitic residue removal |
| Sample Rotation Speed ($\omega_{r}$) | $\le$ 25 | °/s | Optimized DNP efficiency |
| Laser Wavelength | 532 | nm | Optical Pumping |
Key Methodologies
Section titled âKey MethodologiesâThe hyperpolarization was achieved through a multi-step process involving material engineering, surface treatment, and optimized DNP protocols.
- Material Preparation: Milled high-pressure high-temperature (HPHT) Type Ib diamond powders (2 ”m and 100 nm median sizes) were used as the starting material.
- NV Center Creation: Substitutional nitrogens (P1 centers) were converted to NV centers via high-energy electron irradiation (3 x 10$^{18}$ cm-2 dose) followed by annealing at 800 °C.
- Surface Cleaning and T$_{1}$ Enhancement:
- Air Oxidation (AO) at 620 °C was performed to remove graphitic residues.
- Triacid Cleaning (TAC) (HNO${3}$, HClO${4}$, H${2}$SO${4}$ in 1:1:1 proportion at 200 °C) was applied to remove paramagnetic metallic residues (e.g., iron), resulting in a 7x increase in $^{13}$C T$_{1}$.
- Illumination Setup: A 3D-printed microphotonic structure (waveguide array) was used to embed the diamond powder in ethyl cinnamate (buffer medium) to improve illumination homogeneity and mitigate light scattering.
- DNP Sequence Optimization:
- The phase-offset PulsePol sequence (n = 4.5 resonance condition) was used for robust NV-$^{13}$C polarization transfer, mitigating the adverse effects of NV-$^{14}$N hyperfine interaction.
- Individual rectangular pulses were replaced with optimized composite pulses to extend the microwave excitation bandwidth ($\Delta_{pol} \approx (2\pi)15$ MHz).
- Mechanical Rotation: Slow sample rotation ($\le$ 25°/s) was implemented perpendicular to the magnetic field to cycle different NV subsets through the excitation region, doubling the hyperpolarized signal.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe research highlights the limitations of using HPHT diamond (high P1/NV density, shorter T$_{1}$) and points toward the necessity of high-purity, low-nitrogen CVD diamond to achieve the next generation of hyperpolarization agents. 6CCVD is uniquely positioned to supply the required materials and custom engineering services.
Applicable Materials for Advanced Hyperpolarization
Section titled âApplicable Materials for Advanced HyperpolarizationâThe paper notes that achieving higher absolute polarization (P${13C}$ > 1%) requires material with low nitrogen content and long T${1}$ lifetimes, achievable with CVD growth (p. 8).
| Research Requirement | 6CCVD Solution & Material | Technical Advantage |
|---|---|---|
| High Purity, Low Nitrogen Content | Optical Grade Single Crystal Diamond (SCD) | SCD grown via MPCVD offers ultra-low nitrogen content, minimizing P1 centers and maximizing $^{13}$C T$_{1}$ lifetimes, essential for long-duration MRI tracers. |
| Nanoparticle Precursors | High-Purity Polycrystalline Diamond (PCD) Wafers | We supply PCD wafers up to 125 mm in diameter and custom thicknesses (0.1 ”m to 500 ”m), ideal for high-volume milling into high-purity micro- and nanodiamond powders. |
| Core-Shell Structures | Custom SCD/PCD Substrates & Epitaxial Growth | 6CCVD can provide low-nitrogen SCD or PCD substrates for subsequent isotopic enrichment (e.g., $^{13}$C shell over natural abundance core) via epitaxial CVD growth, enabling the proposed core-shell hyperpolarization agents. |
| Thin-Film Substrates | SCD/PCD Substrates up to 10 mm Thickness | For DNP experiments requiring better heat dissipation (e.g., liquid/gel dispersion), 6CCVD provides robust, high-thermal-conductivity diamond substrates. |
Customization Potential for DNP Integration
Section titled âCustomization Potential for DNP IntegrationâThe DNP protocol requires precise integration of microwave (MW) and radio frequency (RF) components, as well as highly controlled surface quality.
- Precision Polishing (Surface T$_{1}$ Mitigation): The research emphasized that surface magnetic noise shortens $^{13}$C T$_{1}$. 6CCVD offers industry-leading polishing services:
- SCD: Surface roughness Ra < 1 nm.
- Inch-size PCD: Surface roughness Ra < 5 nm.
- Benefit: Minimizing surface defects (dangling bonds) is crucial for maximizing the nuclear T$_{1}$ in nanodiamonds.
- Custom Metalization for RF/MW Circuitry: Future DNP setups may require integrated microwave antennas or heat sinks. 6CCVD provides in-house metalization capabilities, including Au, Pt, Pd, Ti, W, and Cu deposition on diamond substrates for integrated quantum sensing and DNP platforms.
- Custom Dimensions and Shaping: We provide custom laser cutting and shaping services for both SCD and PCD plates to fit specialized DNP resonators and microphotonic structures, ensuring optimal sample geometry for illumination and rotation.
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house PhD team specializes in MPCVD growth parameters, defect engineering (NV creation), and surface functionalization. We offer expert consultation to assist researchers in selecting the optimal diamond grade (SCD vs. PCD), nitrogen content, and post-processing steps (irradiation/annealing recipes) required to replicate or extend these sensitive magnetic resonance applications.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Nuclear hyperpolarization is a known method to enhance the signal in nuclear magnetic resonance (NMR) by orders of magnitude. The present work addresses the 13 C hyperpolarization in diamond micro- and nanoparticles, using the optically pumped nitrogen-vacancy center (NV) to polarize 13 C spins at room temperature. Consequences of the small particle size are mitigated by using a combination of surface treatment improving the 13 C relaxation ( T 1 ) time, as well as that of NV, and applying a technique for NV illumination based on a microphotonic structure. Adjustments to the dynamical nuclear polarization sequence (PulsePol) are performed, as well as slow sample rotation, to improve the NV- 13 C polarization transfer rate. The hyperpolarized 13 C NMR signal is observed in particles of 2-micrometer and 100-nanometer median sizes, with enhancements over the thermal signal (at 0.29-tesla magnetic field) of 1500 and 940, respectively. The present demonstration of room-temperature hyperpolarization anticipates the development of agents based on nanoparticles for sensitive magnetic resonance applications.