Quantum‐Grade Nanodiamonds from a Single‐Step, Industrial‐Scale Pressure and Temperature Process
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2025-10-02 |
| Journal | Advanced Functional Materials |
| Authors | Yahua Bao, Michal Gulka, Parkarsh Kumar, Jakub Čopák, Priyadharshini Balasubramanian |
| Institutions | Czech Academy of Sciences, Institute of Organic Chemistry and Biochemistry, Charles University |
| Citations | 1 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled “Executive Summary”The research introduces a revolutionary, single-step Pressure & Temperature Qubits (PTQ) method for producing quantum-grade nanodiamonds (NDs) containing Nitrogen Vacancy (NV) centers, overcoming major scalability limitations of current methods.
- Industrial Scalability: The PTQ method achieves industrial-scale yields, producing >1 kg of fluorescent NDs per work week using a single modified commercial press. This output would require over 40 years using traditional multi-step irradiation and annealing techniques.
- Superior Spin Properties: PTQ NDs exhibit a ≈5-fold enhancement in optical Rabi contrast (up to 40% observed) compared to commercial electron-irradiated NDs (COMM), significantly improving quantum measurement sensitivity.
- Enhanced Relaxation Times: The material demonstrates long T1 relaxation times approaching 1 ms, a bulk-like value crucial for high-sensitivity relaxometry sensing applications.
- Structural Purity and Stability: The high-temperature plastic deformation (~1700 °C, 7 GPa) promotes lattice healing, resulting in lower internal strain (16% smaller zero-field splitting) and superior charge stability (2x higher NV-/NV0 ratio).
- Cost and Time Efficiency: By replacing multi-step irradiation, annealing, and rapid high-temperature annealing (HTA) with a single, fast (≈minutes) process, production time and costs are drastically reduced.
- Multifunctional Bio-Compatibility: PTQ NDs are non-cytotoxic and simultaneously produce both NV (red) and diamagnetic H3 (green) centers, enabling dual-color imaging for nanosensing in biological environments.
Technical Specifications
Section titled “Technical Specifications”| Parameter | Value | Unit | Context |
|---|---|---|---|
| PTQ Processing Temperature | ~1700 | °C | Single-step plastic deformation |
| PTQ Processing Pressure | ~7 | GPa | Single-step plastic deformation |
| PTQ Processing Time | 4 | min | Per press run |
| Starting ND Size (Zeta Potential) | 43.3 ± 3 | nm | Non-luminescent precursor |
| PTQ ND Size (Zeta Potential) | 52.0 ± 2 | nm | Acid oxidized |
| Average Rabi Contrast (PTQ) | 15.9 | % | Single-particle measurement (vs. 3.2% for COMM) |
| T1 Relaxation Time (Alternating) | 989 (≈1) | µs (ms) | PTQ Single-particle, bulk-like value |
| NV-/NV0 PL Ratio (Thin Layer) | 5.37 | N.A. | PTQ Acid Ox. (vs. 2.57 for COMM) |
| NV Zero-Field Splitting (2*E) | 15.2 | MHz | PTQ (vs. 18.2 MHz for COMM), indicating lower strain |
| NV- Excited State Lifetime (τAVG) | 24.0 | ns | PTQ (vs. 19.5 ns for COMM) |
| P1 Nitrogen Concentration | 10.9 | ppm | PTQ (EPR measurement) |
| NV Concentration | 0.31 | ppm | PTQ (EPR measurement) |
| 13C Spin-Lattice T1 | 55 | s | PTQ (NMR measurement) |
| Carbon Structure Purity (sp3) | 93.0 | % | XPS measurement, negligible sp2 content (0.2%) |
| Production Yield (Per Work Week) | >1 | kg | Industrial scale using one modified press |
| Cytotoxicity Threshold | >100 | µg/mL | Viability >70% after 72 h incubation |
Key Methodologies
Section titled “Key Methodologies”The Pressure & Temperature Qubits (PTQ) method utilizes a modified commercial cubic press apparatus to achieve high-yield, single-step NV center creation:
- Starting Material Preparation: Non-luminescent 50-nm Type Ib HPHT diamond powder (containing ≈120 ppm substitutional nitrogen) is mechanically blended with diamagnetic sodium chloride (NaCl) at a 75/25 wt.% ratio.
- Encapsulation: The ND/NaCl mixture is loaded into a tantalum (Ta) metal container and placed within a unique cubic press cell designed for high temperatures and pressures.
- High-Pressure/High-Temperature Treatment: The cell is subjected to simultaneous pressurization (7 GPa) and heating (1700 °C) for approximately 4 minutes.
- Mechanism of Defect Creation: The high pressure induces plastic deformation in the diamond particles, generating C vacancies. The high temperature increases nitrogen mobility, allowing vacancies to combine with substitutional nitrogen (P1 centers) to form NV and H3 centers.
- Graphitization Suppression: The sodium chloride melts at >1500 °C, operating as a semi-hydraulic fluid that keeps the NDs entirely within the diamond thermally stable region, fully suppressing graphite formation.
- Purification: The PTQ-treated NDs are washed with deionized water to remove NaCl and sonicated to break up agglomerates.
- Surface Oxidation: The NDs are acid-oxidized (concentrated sulfuric and nitric acid, 3:1 ratio, 90 °C, 10 h) to clean the surface, which enhances NV- charge stability for quantum sensing applications.
Commercial Applications
Section titled “Commercial Applications”The PTQ method unlocks the widespread commercial adoption of fluorescent nanodiamonds by providing a scalable, high-quality material source.
- Quantum Sensing and Metrology:
- High-Sensitivity Probes: The long T1 times (≈1 ms) and high Rabi contrast (up to 40%) are ideal for developing highly sensitive quantum sensors for magnetic fields, electric fields, and strain.
- Relaxometry: Enables high-fidelity relaxometry sensing, particularly in environments where low laser power is required to minimize charge effects.
- Biomedical and Bioimaging:
- Nanosized Probes: The ~50 nm size, non-cytotoxicity, and dual-emission capability (NV red and H3 green) allow for submicrometer resolution probes in biological environments.
- Cellular Sensing: Suitable for local detection of temperature changes or specific molecules within cells (e.g., using NV spin relaxometry measurements).
- Nuclear Hyperpolarization:
- Enhanced NMR/MRI: The preserved 13C T1 time (55 s) is essential for efficient dynamic nuclear polarization (DNP) experiments, potentially leading to significant sensitivity gains in clinical MRI and laboratory NMR.
- Industrial Material Supply:
- Mass Production: The kg/week yield capacity addresses the resource consumption bottleneck, making NV-NDs economically viable for large-scale manufacturing of quantum devices and sensors.
- Solid-State Quantum Computing:
- Qubit Source: Provides a scalable and cost-effective source of high-quality solid-state qubits for integration into next-generation quantum technologies.
View Original Abstract
Abstract Nanodiamonds with nitrogen vacancy (NV) centers are a promising workhorse for myriad applications, from quantum sensing to bioimaging. However, despite two decades of extensive research, their use remains limited by the lack of scalable methods to produce quantum‐grade material. While traditional NV‐production methods involve multi‐step irradiation and annealing processes, a fundamentally different approach is presented here based on a single‐step high‐temperature plastic deformation. It enables industrial‐scale yield of high‐quality luminescent nanodiamonds while significantly reducing production time and costs. Utilizing a unique cubic press apparatus capable of reaching higher temperatures and pressures, 50‐nm luminescent nanodiamonds with outstanding optical and spin properties are achieved in a single step from non‐luminescent material. Compared to electron‐irradiated nanodiamonds, i.e., common commercially available material, this method yields NV centers with significantly improved charge stability, T 1 relaxation times approaching 1 ms, and a ≈5‐fold enhancement in optical Rabi contrast. What this streamlined process produces in one week would require more than 40 years by current irradiation and annealing methods. Scalable, quantum‐grade nanodiamonds are thus unlocked, providing the missing link for their widespread adoption.