Optimization of Wide-Field ODMR Measurements Using Fluorescent Nanodiamonds to Improve Temperature Determination Accuracy

At a Glance

Metadata	Details
Publication Date	2020-11-18
Journal	Nanomaterials
Authors	Tamami Yanagi, Kiichi Kaminaga, Wataru Kada, Osamu Hanaizumi, Ryuji Igarashi
Institutions	Gunma University, National Institutes for Quantum Science and Technology
Citations	9
Analysis	Full AI Review Included

Technical Documentation & Analysis: Wide-Field ODMR Thermometry

Executive Summary

This research successfully optimized wide-field Optically Detected Magnetic Resonance (ODMR) measurements using fluorescent nanodiamonds (FNDs) to significantly improve temperature determination accuracy, paving the way for advanced quantum sensing in biological systems.

Core Achievement: Demonstrated highly accurate wide-field temperature imaging (210 x 210 µm area) using FNDs containing Nitrogen-Vacancy (NV) centers.
Accuracy Improvement: Temperature determination accuracy was improved by a factor of approximately 1.5 compared to conventional methods.
Optimal Methodology: A Monte Carlo simulation determined the optimal microwave frequency sweep range for ODMR curve fitting to be 2860-2880 MHz.
Performance Metric: Achieved a high temperature determination accuracy of 1 K/Hz^1/2 or better, suitable for monitoring mesoscopic temperature distributions in multicellular systems.
Material Basis: The method relies on the remarkable temperature dependence of the NV center axial anisotropy parameter (D), which changes proportionally at 77 kHz/K.
Application Potential: The technique is critical for monitoring tissue homeostasis, organelle-level thermometry (e.g., mitochondria), and high-throughput image cytometry for stem cell differentiation.

Technical Specifications

The following hard data points were extracted from the research detailing the material properties and experimental performance:

Parameter	Value	Unit	Context
Nanodiamond Particle Size Range	50-100	nm	Used for ODMR measurements
Average NV Centers per Particle	~40	-	-
Electron Irradiation Dose	1.0 x 10¹⁸	e^-/cm²	Used for NV center creation
Thermal Annealing Temperature	800	°C	Performed under vacuum for 2 h
Axial Anisotropy Parameter (D)	2869.34 ± 1.31	MHz	Mean value obtained from 200 bright spots
Rhombic Anisotropy Parameter (E)	4.21 ± 0.31	MHz	Mean value obtained from 200 bright spots
Temperature Dependence of D	77	kHz/K	Proportional constant due to crystal lattice expansion
Optimal ODMR Sweep Range	2860-2880	MHz	Determined by Monte Carlo simulation
Wide-Field Imaging Area	210 x 210	µm	Area suitable for monitoring multicellular systems
Achieved Temperature Accuracy	1	K/Hz^1/2	Accuracy achieved using the optimal sweep range
Excitation Wavelength	532	nm	Green laser excitation (1000 mW)
Microwave Output Power	< 700	mW	Applied via 1.5-turn copper coil

Key Methodologies

The experiment involved precise material preparation and optimized ODMR measurement techniques:

NV Center Generation: Nanodiamond powder (0-0.10 µm) was subjected to 2 MeV electron irradiation at a dose of 1.0 x 10¹⁸ e^-/cm².
Thermal Processing: The irradiated material was thermally annealed at 800 °C for 2 hours under vacuum to mobilize vacancies and form NV centers.
Surface Purification: Surface graphite was removed by oxidation at 550 °C for 2 hours, followed by a 3-day treatment in H₂SO₄:HNO₃ (9:1 v/v) at 70 °C to obtain negatively charged NV centers.
Surface Charge Control: Further surface treatment involved washing with 0.1 M NaOH and 0.1 M HCl at 90 °C to ensure dispersibility and surface termination.
ODMR Setup: Wide-field fluorescence imaging was performed using a 532-nm green laser and an EMCCD camera, collecting fluorescence through a 650 nm long-wave pass filter.
Microwave Delivery: Microwaves were generated, amplified (< 700 mW output), and applied to the sample via a 1.5-turn copper coil.
Optimal Sweep Determination: A Monte Carlo simulation was used to determine the optimal frequency sweep range (2860-2880 MHz) for curve fitting the ODMR spectrum with two Lorentzian functions, maximizing temperature determination accuracy.
Measurement Protocol: Measurements were performed after 1-hour temperature stabilization, restricting local temperature changes to ± 0.1 K during the 2-minute measurement period.

6CCVD Solutions & Capabilities

6CCVD provides the high-purity, low-strain diamond materials and custom fabrication services necessary to replicate, scale, and advance this wide-field quantum thermometry research.

Applicable Materials

The high-accuracy ODMR measurements rely fundamentally on the quality and coherence of the NV centers. 6CCVD offers materials optimized for quantum sensing:

Optical Grade Single Crystal Diamond (SCD): Recommended for achieving the highest possible NV center coherence times and signal contrast. Our SCD wafers (0.1µm to 500µm thick) provide ultra-low strain, which is crucial for minimizing the linewidth broadening that limits temperature accuracy.
Optical Grade Polycrystalline Diamond (PCD): Ideal for scaling the wide-field imaging platform. 6CCVD offers PCD plates up to 125mm in diameter, enabling the creation of large-area sensing substrates for high-throughput biological applications (e.g., monitoring stem cell differentiation over large cell cultures).

Customization Potential

To move this research from a benchtop setup (using an external copper coil) to an integrated, high-performance device, 6CCVD offers comprehensive customization:

Research Requirement	6CCVD Customization Service	Technical Benefit
Integrated Microwave Delivery	Custom Metalization: Internal capability for depositing Au, Pt, Pd, Ti, W, and Cu contacts.	Enables the fabrication of on-chip microwave transmission lines directly onto the diamond substrate, improving field homogeneity and power efficiency.
High-Throughput Platform	Large-Area PCD Wafers: Plates/wafers up to 125mm (5 inches) in diameter.	Allows researchers to scale the 210 x 210 µm wide-field imaging area to cover entire cell culture dishes or tissue samples.
Surface Quality for Bio-Interfacing	Precision Polishing: SCD surfaces polished to Ra < 1nm; Inch-size PCD polished to Ra < 5nm.	Provides the atomically smooth surface necessary for direct cell adhesion and minimizes background scattering during fluorescence imaging.
Specific Substrate Integration	Custom Dimensions & Thickness: Substrates available up to 10mm thick, with custom laser cutting services.	Ensures seamless integration of diamond sensors into existing microscope stages, microfluidic devices, or specialized ODMR setups.

Engineering Support

The optimization of the ODMR sweep range (2860-2880 MHz) highlights the need for precise material characterization and experimental control. 6CCVD’s in-house PhD team specializes in the material science of NV centers:

Material Selection: We assist researchers in selecting the optimal diamond type (SCD vs. PCD) and nitrogen concentration to maximize NV center density while maintaining high coherence for similar nanometer-scale thermometry projects.
Post-Growth Processing: We provide consultation on optimizing post-growth treatments, including irradiation and annealing recipes, to achieve the desired NV^- charge state and concentration required for high-accuracy wide-field sensing.
Global Logistics: We offer reliable global shipping (DDU default, DDP available) to ensure rapid delivery of custom diamond solutions worldwide.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Fluorescent nanodiamonds containing nitrogen-vacancy centers have attracted attention as nanoprobes for temperature measurements in microenvironments, potentially enabling the measurement of intracellular temperature distributions and temporal changes. However, to date, the time resolution and accuracy of the temperature determinations using fluorescent nanodiamonds have been insufficient for wide-field fluorescence imaging. Here, we describe a method for highly accurate wide-field temperature imaging using fluorescent nanodiamonds for optically detected magnetic resonance (ODMR) measurements. We performed a Monte Carlo simulation to determine the optimal frequency sweep range for ODMR temperature determination. We then applied this sweep range to fluorescent nanodiamonds. As a result, the temperature determination accuracies were improved by a factor ~1.5. Our result paves the way for the contribution of quantum sensors to cell biology for understanding, for example, differentiation in multicellular systems.

Tech Support

Original Source

DOI: https://doi.org/10.3390/nano10112282

References

2007 - Microscopic detection of thermogenesis in a single hela cell [Crossref]
2009 - Hydrophilic fluorescent nanogel thermometer for intracellular thermometry [Crossref]
2012 - Intracellular temperature mapping with a fluorescent polymeric thermometer and fluorescence lifetime imaging microscopy [Crossref]
2013 - Genetically encoded fluorescent thermosensors visualize subcellular thermoregulation in living cells [Crossref]
2013 - Nanometre-scale thermometry in a living cell [Crossref]
2017 - Non-neurotoxic nanodiamond probes for intraneuronal temperature mapping [Crossref]
2018 - Precision temperature sensing in the presence of magnetic field noise and vice-versa using nitrogen-vacancy centers in diamond [Crossref]
2020 - Practical applications of quantum sensing: A simple method to enhance the sensitivity of nitrogen-vacancy-based temperature sensors [Crossref]
2011 - Diamond photonics [Crossref]