Insight into a Fenton-like Reaction Using Nanodiamond Based Relaxometry

At a Glance

Metadata	Details
Publication Date	2022-07-15
Journal	Nanomaterials
Authors	Sandeep K. Padamati, Thea Vedelaar, Felipe Perona Martínez, Anggrek Citra Nusantara, Romana Schirhagl
Institutions	University of Groningen, University Medical Center Groningen
Citations	8
Analysis	Full AI Review Included

Technical Documentation & Analysis: Nanodiamond Relaxometry for Fenton-like Reactions

This document analyzes the research paper “Insight into a Fenton-like Reaction Using Nanodiamond Based Relaxometry” to highlight the critical role of high-quality diamond materials in advanced quantum sensing applications and to position 6CCVD as the premier supplier for next-generation research platforms.

Executive Summary

The research successfully demonstrates the use of Nitrogen-Vacancy (NV) center relaxometry in fluorescent nanodiamonds (FNDs) to monitor complex chemical kinetics in real time.

Core Achievement: Real-time, non-destructive measurement of copper(II) concentration changes during a Fenton-like reaction (CuSO₄ + H₂O₂).
Quantum Sensing Advantage: T1-relaxometry avoids the limitations of conventional methods (EPR microwave absorption in aqueous solutions, photobleaching of fluorescent dyes).
Sensitivity: Achieved detection of paramagnetic species (Cu²⁺) down to nanomolar (nM) concentrations, significantly lower than many competing techniques (e.g., FAAS, ICP OES).
Biological Relevance: The concentrations studied are comparable to those found in biological environments, opening pathways for studying oxidative stress and chemodynamic therapies (CDT).
Material Requirement: The success hinges on the quality and stability of the NV centers within the diamond lattice, emphasizing the need for high-purity, controlled diamond substrates for future integrated devices.
Future Direction: The authors suggest future use of advanced pulsing schemes like Double Electron-Electron Resonance (DEER) to differentiate species, requiring ultra-high coherence SCD platforms.

Technical Specifications

The following hard data points were extracted from the methodology and results sections, highlighting the precision required for this quantum sensing application.

Parameter	Value	Unit	Context
Nanodiamond Size (Average)	~70	nm	FNDs used for relaxometry
NV Center Density	Several hundred	centers	Ensemble per FND particle
Copper(II) Detection Limit	100	nM	Quantified using T1 relaxometry
Reaction Time Scale Monitored	20	min	Kinetic trace monitoring
Laser Polarization Wavelength	532	nm	NV center excitation
Fluorescence Detection Filter	550	nm	Long-pass filter
Experimental Temperature	~22	°C	Room temperature, aqueous solution
Copper Concentration Range Tested	100 nM to 10	mM	T1 measurements
H₂O₂ Concentration Range Tested	10 nM to 10	mM	T1 measurements
Raman Excitation Wavelength	785	nm	Used for H₂O₂ decay quantification

Key Methodologies

The core of the research relies on T1-relaxometry, a quantum sensing technique utilizing the spin properties of NV centers.

FND Preparation: Nanodiamond stock solution (1 mg/mL, ~70 nm FNDs) was diluted to 10 µg/mL and deposited onto air plasma-treated glass-bottom Petri dishes.
NV Center Polarization: NV centers were polarized using a 532 nm laser (5 µs illumination time).
Pulsing Sequence: A pulsing scheme was applied via a pulseblaster to an acousto-optical modulator (AOM). Dark time between pulses varied from 0.2 µs to 10 ms.
Signal Acquisition: Photoluminescent signal was detected using an avalanche photo diode (APD) through a 550 nm long-pass filter. Each experiment was repeated 10,000 times to improve the signal-to-noise ratio.
T1 Measurement: The resulting fluorescence decay curve was fitted using a bi-exponential model to determine the T1 relaxation time, which is inversely proportional to the concentration of surrounding paramagnetic species (Cu²⁺).
Kinetic Analysis: A moving window method (combining 1st-2500th repetitions, then 100th-2600th, etc.) was used to achieve a time resolution of approximately 2.5 minutes for real-time kinetic tracking.
Complementary Techniques: UV-Vis absorption (800 nm band for Cu²⁺ decay), Raman spectroscopy (876 cm^-1 band for H₂O₂ decay), and fluorescence spectroscopy (HTA dye) were used to validate the T1 relaxometry results.

6CCVD Solutions & Capabilities

The demonstrated T1-relaxometry technique represents a critical step toward integrated, high-coherence quantum sensors. While this paper utilized FNDs, the next generation of quantum sensing requires high-purity, engineered Single Crystal Diamond (SCD) platforms, which is 6CCVD’s core expertise.

Applicable Materials for Quantum Sensing Advancement

To replicate or extend this research into advanced quantum sensing platforms (e.g., integrated sensors, high-coherence measurements, DEER), researchers require high-purity MPCVD diamond substrates.

6CCVD Material	Specification & Relevance
Optical Grade SCD	Essential for creating shallow, high-coherence NV centers via ion implantation or delta doping. Our SCD offers superior purity and low strain, critical for maximizing T1 and T2 coherence times necessary for advanced relaxometry (e.g., DEER).
Custom SCD Thickness	We provide SCD wafers from 0.1 µm up to 500 µm. Precise thickness control is vital for optimizing the depth of the NV layer relative to the surface chemistry being monitored.
High-Purity PCD	For applications requiring larger area coverage (up to 125 mm diameter) where single-crystal coherence is less critical, our high-purity PCD offers a robust, large-format platform for ensemble NV sensing.

Customization Potential for Integrated Devices

The transition from FNDs in solution to integrated, chip-based quantum sensors requires specialized material engineering capabilities offered by 6CCVD.

Custom Dimensions and Substrates: 6CCVD provides custom plates and wafers up to 125 mm in diameter (PCD) and large-area SCD, allowing for the fabrication of complex microfluidic or chip-scale relaxometry devices.
Precision Polishing: Achieving low surface roughness is paramount for maintaining NV coherence near the surface. We offer Ra < 1 nm polishing for SCD and Ra < 5 nm for inch-size PCD, ensuring minimal surface noise interference.
Integrated Metalization: For creating microwave delivery structures (required for advanced DEER or ODMR pulsing schemes) directly on the diamond, 6CCVD offers in-house metalization services, including Au, Pt, Pd, Ti, W, and Cu deposition. This enables the creation of fully integrated quantum sensing chips.
Substrate Engineering: We offer custom diamond substrates up to 10 mm thick, providing robust mechanical support for complex experimental setups involving high-pressure or flow systems.

Engineering Support

6CCVD’s in-house team of PhD material scientists and engineers specializes in the growth and characterization of diamond for quantum applications. We provide expert consultation on:

Material Selection: Guiding researchers in choosing the optimal diamond grade (SCD vs. PCD) and orientation for specific quantum sensing requirements.
NV Center Optimization: Assisting with material specifications necessary for creating high-density or shallow NV layers, crucial for maximizing sensitivity in Fenton-like reaction and chemodynamic therapy (CDT) studies.
Global Logistics: We ensure reliable, global shipping (DDU default, DDP available) of sensitive, high-value diamond materials directly to your lab.

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

View Original Abstract

Copper has several biological functions, but also some toxicity, as it can act as a catalyst for oxidative damage to tissues. This is especially relevant in the presence of H2O2, a by-product of oxygen metabolism. In this study, the reactions of copper with H2O2 have been investigated with spectroscopic techniques. These results were complemented by a new quantum sensing technique (relaxometry), which allows nanoscale magnetic resonance measurements at room temperature, and at nanomolar concentrations. For this purpose, we used fluorescent nanodiamonds (FNDs) containing ensembles of specific defects called nitrogen-vacancy (NV) centers. More specifically, we performed so-called T1 measurements. We use this method to provide real-time measurements of copper during a Fenton-like reaction. Unlike with other chemical fluorescent probes, we can determine both the increase and decrease in copper formed in real time.

Tech Support

Original Source

DOI: https://doi.org/10.3390/nano12142422

References

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