Self-Assembly of Nanodiamonds and Plasmonic Nanoparticles for Nanoscopy

At a Glance

Metadata	Details
Publication Date	2022-02-28
Journal	Biosensors
Authors	Lukas Schmidheini, Raphael F. Tiefenauer, Volker Gatterdam, Andreas Frutiger, Takumi Sannomiya
Institutions	Institute for Biomedical Engineering, ETH Zurich
Citations	11
Analysis	Full AI Review Included

Technical Documentation & Analysis: Plasmon-Coupled Nanodiamonds for Super-Resolution Nanoscopy

Executive Summary

This document analyzes the research demonstrating a novel hybrid system utilizing plasmonic coupling between Gold Nanoparticles (GNPs) and Nitrogen-Vacancy (NV) center Nanodiamonds (NDs) for super-resolution imaging applications.

Hybrid System Development: A self-assembled hybrid system was created by coupling NV-center nanodiamonds to 50 nm GNPs using DNA hybridization techniques.
Coupling Mechanism: Multiphoton excitation (1020 nm) of the GNPs generates second harmonic emission (centered at 520 nm), which acts as a near-field excitation source for the NV centers (emission peak ~650 nm) in the coupled nanodiamonds.
Stochastic Blinking: The inherent flickering instability of the GNP harmonic modes directly influences the ND emission, resulting in stochastic blinking—a critical requirement for Stochastic Optical Reconstruction Microscopy (STORM).
Super-Resolution Proof: By utilizing these stochastic emission fluctuations, the system demonstrated a proof-of-principle for super-resolution imaging, achieving a resolution of 187 nm, surpassing the diffraction limit.
Application Potential: The platform is highly promising for intracellular biosensing and bioimaging due to the DNA-based coupling, low power requirements, low background, and enhanced tissue transparency offered by multiphoton excitation.
6CCVD Relevance: This research validates the need for high-quality, ultra-pure diamond materials (SCD) and precise surface engineering capabilities (polishing, metalization) that 6CCVD provides to advance quantum sensing and nanoscopy technologies.

Technical Specifications

The following hard data points were extracted from the analysis of the GNP-Nanodiamond hybrid system:

Parameter	Value	Unit	Context
Excitation Wavelength (Multiphoton)	1020	nm	Laser source for GNP excitation
GNP Emission Center (SHG)	520	nm	Second Harmonic Generation, matching NV excitation
Nanodiamond Emission Peak	~650	nm	Corresponds to NV^- centers photoluminescence
GNP Size (Diameter)	50	nm	Chosen for Localized Surface Plasmon (LSP) resonance at 520 nm
ND Size (Diameter, Simulated)	15	nm	Used in MMP 6 simulation
Inter-particle Gap Distance (Simulated)	5	nm	Distance between GNP and ND in coupled system
Power Dependence Slope (GNP)	1.97	N/A	Logarithmic scale, confirming two-photon absorption
Maximum Coupling Efficiency (I_ND/I_GNP)	~0.7	mW	Optimal laser power for efficient energy transfer
Super-Resolution Achieved	187	nm	Distance resolved beyond the diffraction limit (λ/2 ~325 nm)
ND Illumination Power (Max Tested Alone)	1.2	mW	No detectable emission observed in NDs without GNP coupling (800-1300 nm range)

Key Methodologies

The experiment relied on precise chemical functionalization and controlled self-assembly to achieve the necessary nanoscale coupling distance (5 nm gap).

Nanodiamond Surface Oxidation: Nanodiamonds were annealed at 600 °C in air to oxidize the surface, generating carboxylic acid (COOH) groups.
Amine Functionalization: A two-step chemical process was used to functionalize the oxidized nanodiamond surface with amine (-NH₂) groups.
DNA Tagging: The amine-functionalized NDs were reacted with an SSMCC crosslinker, followed by reaction with thiol-modified DNAs (DNA1), enabling specific binding.
GNP Functionalization: Gold nanoparticles were separately functionalized with complementary DNA strands (DNA2).
DNA Hybridization Assembly: The ND-DNA1 and GNP-DNA2 conjugates were mixed with a target DNA (C1-C2) to induce self-assembly, controlling the coupling distance and particle ratio via DNA length and concentration.
Multiphoton Optical Analysis: Coupled particles were coated on glass coverslips and excited using a multiphoton laser at 1020 nm.
Dual-Channel Detection: Emission was separated into a Green channel (480-580 nm, corresponding to GNP SHG) and a Red channel (620-680 nm, corresponding to ND NV^- emission).
Nanoscopy Implementation: Stochastic emission fluctuations (blinking) in the nanodiamonds were utilized in a time-series stack of images, followed by localization algorithms (point spread function fitting) to achieve super-resolution.

6CCVD Solutions & Capabilities

6CCVD is uniquely positioned to supply the foundational diamond materials and advanced surface engineering required to replicate, scale, and extend this groundbreaking research in plasmonic nanoscopy and quantum sensing.

Applicable Materials

To achieve the high photostability and precise NV center characteristics required for nanoscopy, researchers need the highest quality diamond host material.

High-Purity Single Crystal Diamond (SCD): 6CCVD provides optical-grade SCD wafers and plates, which are the ideal precursors for creating stable, high-coherence NV centers necessary for quantum sensing and super-resolution applications.
Polycrystalline Diamond (PCD) Substrates: For scaling up the functionalization process or integrating the hybrid system into larger devices, 6CCVD offers large-area PCD plates up to 125 mm in diameter.
Boron-Doped Diamond (BDD): For extending the application into electrochemical biosensing (as mentioned in the paper’s potential applications), 6CCVD supplies BDD materials, offering conductive, chemically inert surfaces.

Customization Potential

The success of this experiment relies heavily on precise surface chemistry and nanoscale proximity (5 nm gap). 6CCVD’s advanced processing capabilities ensure optimal material preparation for subsequent functionalization steps.

Research Requirement	6CCVD Capability	Sales Advantage
Ultra-Smooth Surface Preparation	Precision Polishing: Ra < 1 nm (SCD) and Ra < 5 nm (Inch-size PCD).	Ensures uniform surface functionalization (oxidation/amine attachment) and minimizes scattering losses, crucial for consistent DNA hybridization and coupling efficiency.
Integrated Plasmonic Structures	Custom Metalization: In-house deposition of Au, Pt, Pd, Ti, W, Cu.	Allows researchers to move beyond self-assembly by fabricating precise plasmonic nanoantennas or waveguides directly onto the diamond surface, potentially enhancing coupling efficiency and stability compared to DNA hybridization.
Thin Film/Membrane Integration	Custom Thickness Control: SCD and PCD layers available from 0.1 µm up to 500 µm.	Critical for creating thin diamond membranes suitable for transmission electron microscopy (TEM) analysis or for integration into microfluidic/intracellular imaging devices.
Custom Dimensions	Large-Area Wafers: Plates/wafers up to 125 mm (PCD).	Supports the transition from proof-of-concept experiments to scalable, high-throughput biosensing platforms.

Engineering Support

6CCVD’s in-house PhD team specializes in MPCVD growth parameters, defect engineering, and surface modification techniques. We can assist researchers in optimizing the diamond material for similar Super-Resolution Nanoscopy and Intracellular Biosensing projects. This includes consultation on:

Optimizing NV center density and charge state (NV^- vs. NV⁰) for enhanced blinking contrast.
Selecting the appropriate diamond crystal orientation and surface termination for specific chemical functionalization protocols (e.g., amine attachment).
Designing integrated plasmonic structures for deterministic coupling, replacing stochastic DNA assembly.

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

View Original Abstract

Nanodiamonds have emerged as promising agents for sensing and imaging due to their exceptional photostability and sensitivity to the local nanoscale environment. Here, we introduce a hybrid system composed of a nanodiamond containing nitrogen-vacancy center that is paired to a gold nanoparticle via DNA hybridization. Using multiphoton optical studies, we demonstrate that the harmonic mode emission generated in gold nanoparticles induces a coupled fluorescence emission in nanodiamonds. We show that the flickering of harmonic emission in gold nanoparticles directly influences the nanodiamonds’ emissions, resulting in stochastic blinking. By utilizing the stochastic emission fluctuations, we present a proof-of-principle experiment to demonstrate the potential application of the hybrid system for super-resolution microscopy. The introduced system may find applications in intracellular biosensing and bioimaging due to the DNA-based coupling mechanism and also the attractive characteristics of harmonic generation, such as low power, low background and tissue transparency.

Tech Support

Original Source

DOI: https://doi.org/10.3390/bios12030148

References

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