Defects In Nanodiamonds Research Articles

Geometries of defects in nanodiamonds optimized with the low-cost methods: How good are they for the electronic g-tensor calculations?

The geometry optimization of 30 paramagnetic defects, including biomedically attractive nitrogen-, silicon-, germanium-, and nickel-related color centers, is performed after their incorporation into hydrogenated nanodiamond (ND) of C84H64 size. The main aim is to examine the effectiveness of the low-cost methods, namely, PBEh-3c, r2SCAN-3c, B97-3c, HF-3c, and GFN2-xTB, in reproducing the geometries of these defects basing on the similarity between the results of the subsequent electronic g-tensor calculations. It is revealed that the overall performance of PBEh-3c, r2SCAN-3c, and B97-3c is very alike and can be considered as good, however, none of these “3c” approaches is able to cope with all tested geometries. The results of HF-3c, on the other hand, are disappointing, as this method is outperformed by computationally much more lighter GFN2-xTB. Additional calculations carried out for dangling bonds introduced into hydroxylated and aminated NDs show that all low-cost methods perform reasonably well for this type of defect but the largest quantitative discrepancies once again are demonstrated by HF-3c. The obtained findings lay the foundations for the future studies of larger NDs with the purpose to figure out the magnetic properties dependence on the size of NDs or defect positions within NDs.

All-Optical Modulation of Single Defects in Nanodiamonds: Revealing Rotational and Translational Motions in Cell Traction Force Fields.

Measuring the mechanical interplay between cells and their surrounding microenvironment is vital in cell biology and disease diagnosis. Most current methods can only capture the translational motion of fiduciary markers in the deformed matrix, but their rotational motions are normally ignored. Here, by utilizing single nitrogen-vacancy (NV) centers in nanodiamonds (NDs) as fluorescent markers, we propose a linear polarization modulation (LPM) method to monitor in-plane rotational and translational motions of the substrate caused by cell traction forces. Specifically, precise orientation measurement and localization with background suppression were achieved via optical polarization selective excitation of single NV centers with precisions of ∼0.5°/7.5 s and 2 nm/min, respectively. Additionally, we successfully applied this method to monitor the multidimensional movements of NDs attached to the vicinity of cell focal adhesions. The experimental results agreed well with our theoretical calculations, demonstrating the practicability of the NV-based LPM method in studying mechanobiology and cell-material interactions.

Silicon-Vacancy Nanodiamonds as High Performance Near-Infrared Emitters for Live-Cell Dual-Color Imaging and Thermometry.

Nanodiamonds (NDs) with color centers are excellent emitters for various bioimaging and quantum biosensing applications. In our work, we explore new applications of NDs with silicon-vacancy centers (SiV) obtained by high-pressure high-temperature (HPHT) synthesis based on metal-catalyst-free growth. They are coated with a polypeptide biopolymer, which is essential for efficient cellular uptake. The unique optical properties of NDs with SiV are their high photostability and narrow emission in the near-infrared region. Our results demonstrate for the first time that NDs with SiV allow live-cell dual-color imaging and intracellular tracking. Also, intracellular thermometry and challenges associated with SiV atomic defects in NDs are investigated and discussed for the first time. NDs with SiV nanoemitters provide new avenues for live-cell bioimaging, diagnostic (SiV as a nanosized thermometer), and theranostic (nanodiamonds as drug carrier) applications.

On-Demand, Direct Printing of Nanodiamonds at the Quantum Level.

The quantum defects in nanodiamonds, such as nitrogen‐vacancy (NV) centers, are emerging as a promising candidate for nanoscale sensing and imaging, and the controlled placement with respect to target locations is vital to their practical applications. Unfortunately, this prerequisite continues to suffer from coarse positioning accuracy, low throughput, and process complexity. Here, it is reported on direct, on‐demand electrohydrodynamic printing of nanodiamonds containing NV centers with high precision control over quantity and position. After thorough characterizations of the printing conditions, it is shown that the number of printed nanodiamonds can be controlled at will, attaining the single‐particle level precision. This printing approach, therefore, enables positioning NV center arrays with a controlled number directly on the universal substrate without any lithographic process. The approach is expected to pave the way toward new horizons not only for experimental quantum physics but also for the practical implementation of such quantum systems.

Label-free tomographic imaging of nanodiamonds in living cells

Nanodiamonds have acknowledged growing attention due to their facile functionalization, stable fluorescence, low toxicity, and decent biocompatibility. However, despite advances applications of nanodiamonds in drug delivery, catalysis and bio-sensing, laser irradiation still limits long-time tracking of nanodiamonds in living cells due to phototoxicity. Here, using optical diffraction tomography, we performed quantitative morphological and biophysical analysis of living cells via endocytosis or electroporation of nanodiamonds (5 nm, 35 nm, and 100 nm) without the need for a fluorescence label. Optical diffraction tomography is an inexpensive and noninvasive microscopy technique, which images cells and subcellular structures as a function of their refractive index. The laser excitation power is much weaker than in the case of fluorescence microscopy, which reduces phototoxicity. Thanks to the very high refractive index of diamond, nanodiamonds in HeLa cells can be clearly discriminated from cellular structures using optical diffraction tomography. As an application, we show that aggregation and deaggregation of internalized nanodiamonds can be detected via changes in the refractive index distribution of the entire cell. Optical diffraction tomography successively images prevention of in-cell particle aggregation through polyglycerol coating of nanodiamonds. In the case of endocytosis, optical diffraction tomography shows deaggregation of nanodiamonds after a prolonged incubation time.Together, our findings implicate that refractive index measurements are a favorable tool to track nanodiamonds, without a fluorescent label, inside living cells. This could be useful to study real-time therapeutic or metabolic activities in living cells using very weak laser irradiation. Finally, the elaborate creation of fluorescent defects in nanodiamonds becomes redundant.

Germanium defects in nanodiamonds show promise for quantum information applications

Germanium-vacancy defects in nanodiamonds have more ideal optical properties than their nitrogen and silicon counterparts as single photon sources.

Hyperbolic Metamaterials via Hierarchical Block Copolymer Nanostructures

AbstractHyperbolic metamaterials (HMMs) offer unconventional properties in the field of optics, enabling opportunities for confinement and propagation of light at the nanoscale. In‐plane orientation of the optical axis, in the direction coinciding with the anisotropy of the HMMs, is desirable for a variety of novel applications in nanophotonics and imaging. Here, a method for creating localized HMMs with in‐plane optical axis, based on block copolymer (BCP) blend instability, is introduced. The dewetting of BCP thin film over topographically defined substrates generates droplets composed of highly ordered lamellar nanostructures in hierarchical configuration. The hierarchical nanostructures represent a valuable platform for the subsequent pattern transfer into a Au/air HMM, exhibiting hyperbolic behavior in a broad wavelength range in the visible spectrum. A computed Purcell factor as high as 32 at 580 nm supports the strong reduction in the fluorescence lifetime of defects in nanodiamonds placed on top of the HMM.

Long range interactions and related carbon-carbon bond reconstruction between interior and surface defects in nanodiamonds.

Interactions between interior substitutional nitrogen defects and surface unsaturated dangling bonds in synthetic nanodiamonds of ∼25 nm size were explored experimentally and theoretically. The experimental results demonstrate the disappearance of the specific paramagnetism of nitrogen centers in the smallest nanoparticles isolated after processing large micron diamonds in a ball mill, accompanied by the formation of unsaturated surface dangling bonds and internal defects. First principles modelling confirms the vanishing of the magnetic moments related with nitrogen centers even for distances from the surface defects greater than 1 nm. To understand this effect, we consider a bond reconstruction scheme with the formation of several carbon-carbon double bonds in the area between the interior and surface point defects. The scheme is in agreement with the changes in electron density through the distance between the two defects. The developed approach can be used to describe the interactions between various defects in carbon-based systems.

Probing and manipulating embryogenesis via nanoscale thermometry and temperature control.

Understanding the coordination of cell-division timing is one of the outstanding questions in the field of developmental biology. One active control parameter of the cell-cycle duration is temperature, as it can accelerate or decelerate the rate of biochemical reactions. However, controlled experiments at the cellular scale are challenging, due to the limited availability of biocompatible temperature sensors, as well as the lack of practical methods to systematically control local temperatures and cellular dynamics. Here, we demonstrate a method to probe and control the cell-division timing in Caenorhabditis elegans embryos using a combination of local laser heating and nanoscale thermometry. Local infrared laser illumination produces a temperature gradient across the embryo, which is precisely measured by in vivo nanoscale thermometry using quantum defects in nanodiamonds. These techniques enable selective, controlled acceleration of the cell divisions, even enabling an inversion of division order at the two-cell stage. Our data suggest that the cell-cycle timing asynchrony of the early embryonic development in C. elegans is determined independently by individual cells rather than via cell-to-cell communication. Our method can be used to control the development of multicellular organisms and to provide insights into the regulation of cell-division timings as a consequence of local perturbations.

High-throughput nitrogen-vacancy center imaging for nanodiamond photophysical characterization and pH nanosensing.

The fluorescent nitrogen-vacancy (NV) defect in diamond has remarkable photophysical properties, including high photostability which allows stable fluorescence emission for hours; as a result, there has been much interest in using nanodiamonds (NDs) for applications in quantum optics and biological imaging. Such applications have been limited by the heterogeneity of NDs and our limited understanding of NV photophysics in NDs, which is partially due to the lack of sensitive and high-throughput methods for photophysical analysis of NDs. Here, we report a systematic analysis of NDs using two-color wide-field epifluorescence imaging coupled to high-throughput single-particle detection of single NVs in NDs with sizes down to 5–10 nm. By using fluorescence intensity ratios, we observe directly the charge conversion of single NV center (NV− or NV0) and measure the lifetimes of different NV charge states in NDs. We also show that we can use changes in pH to control the main NV charge states in a direct and reversible fashion, a discovery that paves the way for performing pH nanosensing with a non-photobleachable probe.

Comparison of morphological and structural characteristics of nanopowder particles obtained by natural diamond grinding and detonation synthesis

The study covers specific features of morphological and structural characteristics exhibited by nanopowder particles obtained by grinding a massive natural diamond and the method of detonation synthesis. High-resolution transmission and scanning electron microscopy, small-angle X-ray scattering demonstrated that natural diamond nanopowder particles obtained by grinding have a wider range of sizes and a plated appearance, unlike detonation synthesis nanopowders consisting of similar in size and isometric particles. X-ray diffraction analysis and Raman spectroscopy used in addition to the methods mentioned above showed that the structure of nanodiamond particles obtained from natural diamond is similar to the structure of a detonation synthesis nanodiamond. Each particle of natural nanopowder, as well as detonation synthesis nanodiamond, consists of a diamond core with a crystal lattice related to the cubic system and a shell containing mainly non-diamond carbon forms with sp 2 hybridization having a complex structure. The average particle size of nanopowders obtained from natural diamond and using detonation synthesis studied by three methods including BET showed results that are in satisfactory agreement with each other. The average nanoparticle size is about 24 nm for natural diamond powder and close to 5.6 nm for UDA-S-GO detonation synthesis nanodiamonds produced by the Federal Research and Production Center «Altai». An insignificant increase in the interatomic distances in diamond nanocrystals compared with a massive diamond crystal was shown experimentally. The study and analysis of a numerous images of natural and detonation synthesis diamond nanocrystals obtained by high-resolution transmission electron microscopy made it possible to establish that the most frequent defects in nanodiamonds are dislocations and point defects.

Location of paramagnetic defects in detonation nanodiamond from proton spin-lattice relaxation data

We developed an approach for determining location of intrinsic paramagnetic defects in nanodiamonds from the data of proton spin-lattice relaxation of the surface hydrogen atoms. The approach was applied to the detonation nanodiamond (DND) of the diameter of 5 nm. We found that dangling bonds with unpaired electron spins are located within the near-surface belt at the distance of 0.3–0.9 nm from the DND surface. The NMR data are compared with the results of EPR measurements.

Electronic features of vacancy, nitrogen, and phosphorus defects in nanodiamonds

Defective nanostructures with a surface termination are the focus of this work. In order to elucidate the influence of the defect on the properties of nanomaterials, we take hydrogen terminated nanodiamonds. Various vacancy defect centers are separately embedded in a nanodiamond at different positions. These include some of the known defects, such as the charged nitrogen-vacancy (NV−), the silicon-vacancy (SiV0), the germanium-vacancy (GeV0), the phosphorous-nitrogen (PN), and the nickel-vacancy (NiV−). For these defective nanodiamonds, we probe the influence of the defect type, its position, as well as the size of the nanodiamond through their structural and electronic features. A detailed and comparative analysis is provided here, based on quantum mechanical simulations. Our results shed light into the inherent differences of these defects in nanodiamonds, allowing for a better understanding of defective nanostructures. In the end, we discuss the potential of tuning their characteristics in view of novel nanotechnological applications.

Not All Fluorescent Nanodiamonds Are Created Equal: A Comparative Study

AbstractFluorescent nanodiamonds (FNDs) are vital to many emerging nanotechnological applications, from bioimaging and sensing to quantum nanophotonics. Yet, understanding and engineering the properties of fluorescent defects in nanodiamonds remain challenging. The most comprehensive study to date is presented, of the optical and physical properties of five different nanodiamond samples, in which fluorescent nitrogen‐vacancy (NV) centers are created using different fabrication techniques. The FNDs' fluorescence spectra, lifetime, and spin relaxation time (T1) are investigated via single‐particle confocal fluorescence microscopy and in ensemble measurements in solution (T1 excepted). Particle sizes and shapes are determined using scanning electron microscopy and correlated with the optical results. Statistical tests are used to explore correlations between the properties of individual particles and also analyze average results to directly compare different fabrication techniques. Spectral unmixing is used to quantify the relative NV charge‐state (NV− and NV0) contributions to the overall fluorescence. A strong variation is found and quantified in the properties of individual particles within all analyzed samples and significant differences between the different particle types. This study is an important contribution toward understanding the properties of NV centers in nanodiamonds. It motivates new approaches to the improved engineering of NV‐containing nanodiamonds for future applications.

ChemInform Abstract: Defects in Nanodiamonds: Application of High‐Frequency CW and Pulse EPR, ODMR

AbstractReview: 45 refs.

Photoluminescence of silicon‐vacancy defects in nanodiamonds of different chondrites

AbstractPhotoluminescence spectra show that silicon impurity is present in lattice of some nanodiamond grains (ND) of various chondrites as a silicon‐vacancy (SiV) defect. The relative intensity of the SiV band in the diamond‐rich separates depends on chemical composition of meteorites and on size of ND grains. The strongest signal is found for the size separates enriched in small grains; thus, confirming our earlier conclusion that the SiV defects preferentially reside in the smallest (≤2 nm) grains. The difference in relative intensities of the SiV luminescence in the diamond‐rich separates of individual meteorites are due to variable conditions of thermal metamorphism of their parent bodies and/or uneven sampling of nanodiamond populations. Annealing of separates in air eliminates surface sp2‐carbon; consequently, the SiV luminescence is enhanced. Strong and well‐defined luminescence and absorption of the SiV defect is a promising feature to locate cold (<250 °C) nanodiamonds in space.

Enhanced photoluminescence from single nitrogen-vacancy defects in nanodiamonds coated with phenol-ionic complexes.

Fluorescent nanodiamonds are attracting major attention in the field of bio-sensing and bio-labeling. In this work we demonstrate a robust approach to achieve an encapsulation of individual nanodiamonds with phenol-ionic complexes that enhance the photoluminescence from single nitrogen vacancy (NV) centers. We show that single NV centres in the coated nanodiamonds also exhibit shorter lifetimes, opening another channel for high resolution sensing. We propose that the nanodiamond encapsulation reduces the non-radiative decay pathways of the NV color centers. Our results provide a versatile and assessable way to enhance photoluminescence from nanodiamond defects that can be used in a variety of sensing and imaging applications.

Defects in Nanodiamonds: Application of High-Frequency cw and Pulse EPR, ODMR

Different aspects of applications of electron paramagnetic resonance (EPR) based techniques including high frequency (HF) electron spin echo (ESE), electron-nuclear double resonance (ENDOR) and optically detected magnetic resonance (ODMR) approaches to study diamond nanostructures are examined.

Silicon vacancy color center photoluminescence enhancement in nanodiamond particles by isolated substitutional nitrogen on {100} surfaces.

Fluorescent nanodiamonds were produced by incorporation of silicon-vacancy (Si-V) defect centers in as-received diamonds of averaged size ∼255 nm using microwave plasma chemical vapor deposition. The potential for further enhancement of Si-V emission in nanodiamonds (NDs) is demonstrated through controlled nitrogen doping by adding varying amounts of N(2) in a H(2) + CH(4) feedgas mixture. Nitrogen doping promoted strong narrow-band (FWHM ∼ 10 nm) emission from the Si-V defects in NDs, as confirmed by room temperature photoluminescence. At low levels, isolated substitutional nitrogen in {100} growth sectors is believed to act as a donor to increase the population of optically active (Si-V)(-) at the expense of optically inactive Si-V defects, thus increasing the observed luminescence from this center. At higher levels, clustered nitrogen leads to deterioration of diamond quality with twinning and increased surface roughness primarily on {111} faces, leading to a quenching of the Si-V luminescence. Enhancement of the Si-V defect through controlled nitrogen doping offers a viable alternative to nitrogen-vacancy defects in biolabeling/sensing applications involving sub-10 nm diamonds for which luminescent activity and stability are reportedly poor.

Ab Initio Studies of Fluorine Passivation on the Electronic Structure of the NV− Defect in Nanodiamond

We have investigated using density functional theory the effect of fluorine termination of a (001) diamond surface on the electronic energy levels of an NV- centre buried beneath the surface. We find that, like OH termination, fluorine passivates the surface and reduces the influence of the surface on the electronic properties of the NV- centre. The results have significance for the optical properties of NV- defects in nanodiamonds.