Multifunctional Core/Shell Diamond Nanoparticles Combining Unique Thermal and Light Properties for Future Biological Applications
At a Glance
Section titled āAt a Glanceā| Metadata | Details |
|---|---|
| Publication Date | 2023-12-12 |
| Journal | Nanomaterials |
| Authors | S. A. Grudinkin, Kirill Bogdanov, V. A. Tolmachev, Š. Š. ŠŠ°ŃŠ°Š½Š¾Š², Ilya E. Kaliya |
| Institutions | Ioffe Institute, ITMO University |
| Citations | 2 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled āExecutive SummaryāThis research details the development and characterization of multifunctional core/shell diamond nanoparticles (CSNDs) designed for advanced biomedical applications, specifically combining photothermal therapy, local thermometry, and fluorescent imaging.
- Core Functionality: The core is heavily doped with Boron (BND) via Chemical Vapor Deposition (CVD), acting as an efficient photothermal absorber/heater when exposed to near-infrared or visible laser light (532 nm used for testing).
- Shell Functionality: The shell is a transparent CVD diamond layer embedded with negatively charged Silicon Vacancy (SiV) color centers, which serve as an optical thermometer and fluorescent marker.
- Sensing Mechanism: Local heating of the BND core shifts the SiV Zero-Phonon Line (ZPL) emission wavelength (~738 nm), allowing for precise, remote nanothermometry.
- Therapeutic Achievement: The CSNDs achieved therapeutic temperatures (45-50 Ā°C) using incident laser power densities (44-52 W/cm2) considered safe for biological systems.
- Synthesis Method: A two-stage Hot Filament CVD (HFCVD) process was utilized to sequentially grow the BND core and the SiV-doped shell on an opal substrate, promoting a close-to-spherical morphology.
- Imaging Capability: The intense and narrowband ZPL of the SiV centers provides high-quality fluorescent imaging in the biological transparency window.
Technical Specifications
Section titled āTechnical Specificationsā| Parameter | Value | Unit | Context |
|---|---|---|---|
| Nanoparticle Morphology | Core/Shell, Close-to-spherical | N/A | Grown on SiO2 opal substrate |
| Core Diameter (BND) | 800-1100 | nm | Heavily Boron-doped |
| Shell Thickness (SiV) | ~500 | nm | Luminescent SiV layer |
| Core Doping Concentration (B/C) | 64,000 | ppm | In gas mixture (Diborane/Methane) |
| Excitation Wavelength | 532 | nm | Used for heating and PL measurement |
| SiV ZPL Wavelength (Low Power) | 738.9 | nm | Baseline temperature |
| SiV ZPL Wavelength (High Power) | 741.1 | nm | Maximum observed shift |
| Therapeutic Temperature Target | 45-50 | Ā°C | Relevant for hyperthermia |
| Required Power Density (Therapy) | 44-52 | W/cm2 | Achieved 45-50 Ā°C range |
| Maximum Induced Temperature | >150 | Ā°C | Achieved at 40 mW laser power |
| Diamond Raman Peak (Shell) | 1332 | cm-1 | Characteristic sp3 lattice |
| BND Raman Shift (Core) | ~1300 | cm-1 | Shift due to heavy boron doping |
Key Methodologies
Section titled āKey MethodologiesāThe multifunctional CSNDs were fabricated using a two-stage Hot Filament Chemical Vapor Deposition (HFCVD) technique on a synthetic opal film substrate.
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Substrate Preparation:
- Synthetic opal films (9-15 monolayers of ~250 nm amorphous SiO2 spheres) were formed on a fused silica wafer using vertical deposition.
- The opal structure and spherical particle shape minimize heat leakage from the growing ND to the substrate.
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Stage 1: Boron-Doped Diamond (BND) Core Growth:
- Method: HFCVD, using detonation nanodiamonds (~4 nm) as nucleation centers.
- Doping: Diborane (B2H6) was introduced into the CH4/H2 gas mixture to achieve heavy boron doping (64,000 ppm B/C ratio).
- Process Parameters: Tungsten coil temperature 2000-2200 Ā°C; Substrate temperature 800 Ā°C; Pressure 48 Torr; Methane concentration 4%; Growth time ~3 h.
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Stage 2: SiV-Doped Shell Growth:
- Method: HFCVD over the BND cores.
- Doping: A crystalline silicon wafer was placed on the substrate holder. Atomic hydrogen etching of the wafer created volatile SiHx radicals, which were incorporated into the growing diamond lattice to form SiV color centers.
- Process Parameters: Tungsten coil temperature 2000-2200 Ā°C; Substrate temperature 750 Ā°C; Pressure 50 Torr; Methane concentration 4%; Growth time 1.5 h.
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Optical Characterization:
- Raman/PL Spectroscopy: Measured using a Renishaw āInViaā spectrometer (488 nm excitation) to confirm doping levels (Raman shift) and SiV presence (PL).
- Thermometry Calibration: A home-built setup (532 nm CW argon laser) was used to measure the SiV ZPL spectral shift as a function of incident light power, correlating the shift to temperature based on established literature data.
Commercial Applications
Section titled āCommercial ApplicationsāThis core/shell nanodiamond technology is highly relevant for advanced nanomedicine and sensing platforms, leveraging the unique thermal and optical properties of diamond color centers.
- Theranostics (Therapy + Diagnostics):
- Local Hyperthermia: The BND core provides efficient, localized heating for selective tumor cell destruction.
- Real-Time Thermometry: The SiV shell allows for simultaneous, non-invasive monitoring of the local temperature during therapy, ensuring controlled heating within the therapeutic window (40-46 Ā°C).
- High-Resolution Bioimaging:
- The intense, near-infrared SiV emission (~738 nm) is ideal for fluorescent imaging in biological tissues, minimizing scattering and absorption.
- Nanoscale Sensing:
- The temperature-dependent ZPL shift enables high-precision nanothermometry in complex environments, including intracellular spaces.
- Advanced Material Synthesis:
- The two-stage HFCVD process provides a scalable method for creating complex, multi-functional diamond heterostructures with tailored impurity profiles (e.g., combining B, Si, Ge, or N centers).
View Original Abstract
We report the development of multifunctional core/shell chemical vapor deposition diamond nanoparticles for the local photoinduced hyperthermia, thermometry, and fluorescent imaging. The diamond core heavily doped with boron is heated due to absorbed laser radiation and in turn heats the shell of a thin transparent diamond layer with embedded negatively charged SiV color centers emitting intense and narrowband zero-phonon lines with a temperature-dependent wavelength near 738 nm. The heating of the core/shell diamond nanoparticle is indicated by the temperature-induced spectral shift in the intensive zero-phonon line of the SiV color centers embedded in the diamond shell. The temperature of the core/shell diamond particles can be precisely manipulated by the power of the incident light. At laser power safe for biological systems, the photoinduced temperature of the core/shell diamond nanoparticles is high enough to be used for hyperthermia therapy and local nanothermometry, while the high zero-phonon line intensity of the SiV color centers allows for the fluorescent imaging of treated areas.
Tech Support
Section titled āTech SupportāOriginal Source
Section titled āOriginal SourceāReferences
Section titled āReferencesā- 2022 - Conjugated Polymer Nanoparticles and Their Nanohybrids as Smart Photoluminescent and Photoresponsive Material for Biosensing, Imaging, and Theranostics [Crossref]
- 2020 - Boron-Doped Nanodiamonds as Anticancer Agents: En Route to Hyperthermia/Thermoablation Therapy [Crossref]
- 2017 - Boron-Doped Nanodiamonds as Possible Agents for Local Hyperthermia [Crossref]
- 2021 - Nanodiamonds: Synthesis, Properties, and Applications in Nanomedicine [Crossref]
- 2013 - Targeting Polymeric Fluorescent Nanodiamond-Gold/Silver Multi-Functional Nanoparticles as a Light-Transforming Hyperthermia Reagent for Cancer Cells [Crossref]
- 2023 - A Plasmonic Fluorescent Ratiometric Temperature Sensor for Self-Limiting Hyperthermic Applications Utilizing FRET Enhancement in the Plasmonic Field [Crossref]
- 2022 - Laser Synthesized Nanodiamonds with Hyper-Branched Polyglycerol and Polydopamine for Combined Imaging and Photothermal Treatment [Crossref]