Science and engineering of nanodiamond particle surfaces for biological applications (Review)

Exploring nanodiamonds: leveraging their dual capacities for anticancer photothermal therapy and temperature sensing

Cancer has become a primary global health concern, which has prompted increased attention towards targeted therapeutic approaches like photothermal therapy (PTT). The unique optical and magnetic properties of nanodiamonds (NDs) have made them versatile nanomaterials with promising applications in biomedicine. This comprehensive review focuses on the potential of NDs as a multifaceted platform for anticancer therapy, mainly focusing on their dual functionality in PTT and temperature sensing. The review highlighted NDs' ability to enhance PTT through hybridization or modification, underscoring their adaptability in delivering small molecule reagents effectively. Furthermore, NDs, particularly fluorescent nanodiamonds (FNDs) with negatively charged nitrogen-vacancy centers, enable precise temperature monitoring, enhancing PTT efficacy in anticancer treatment. Integrating FNDs into PTT holds promise for advancing therapeutic efficacy by providing valuable insights into localized temperature variations and cell death mechanisms. This review highlights new insights into cancer treatment strategies, showcasing the potential of NDs to revolutionize targeted therapeutics and improve patient outcomes.

Tritium-Labeled Nanodiamonds as an Instrument to Analyze Bioprosthetic Valve Coatings: A Case of Using a Nanodiamond Containing Coating on a Pork Aorta

Coatings with xenogenic materials, made of detonation nanodiamonds, provide additional strength and increase elasticity. A functionally developed surface of nanodiamonds makes it possible to apply antibiotics. Previous experiments show the stability of such coatings; however, studies on stability in the bloodstream and calcification of the material in natural conditions have yet to be conducted. Tritium-labeled nanodiamonds (negative and positive) were obtained by the tritium activation method and used to develop coatings for a pork aorta to analyze their stability in a pig's bloodstream using a radiotracer technique. A chitosan layer was applied from a solution of carbonic acid under high-pressure conditions to prevent calcification. The obtained materials were used to prepare a porcine conduit, which was surgically stitched inside the pig's aorta for four months. The aorta samples, including nanodiamond-coated and control samples, were analyzed for nanodiamond content and calcium, using the radiotracer and ICP-AES methods. A histological analysis of the materials was also performed. The obtained coatings illustrate a high in vivo stability and low levels of calcification for all types of nanodiamonds. Even though we did not use additional antibiotics in this case, the development of infection was not observed for negatively charged nanodiamonds, opening up prospects for their use in developing coatings.

Nanodiamonds: A Cutting-Edge Approach to Enhancing Biomedical Therapies and Diagnostics in Biosensing

Nanodiamonds (NDs) have garnered attention in the field of nanomedicine due to their unique properties. This review offers a comprehensive overview of NDs synthesis methods, properties, and their uses in biomedical applications. Various synthesis techniques, such as detonation, high-pressure, high-temperature, and chemical vapor deposition, offer distinct advantages in tailoring NDs' size, shape, and surface properties. Surface modification methods further enhance NDs' biocompatibility and enable the attachment of bioactive molecules, expanding their applicability in biological systems. NDs serve as promising nanocarriers for drug delivery, showcasing biocompatibility and the ability to encapsulate therapeutic agents for targeted delivery. Additionally, NDs demonstrate potential in cancer treatment through hyperthermic therapy and vaccine enhancement for improved immune responses. Functionalization of NDs facilitates their utilization in biosensors for sensitive biomolecule detection, aiding in precise diagnostics and rapid detection of infectious diseases. This review underscores the multifaceted role of NDs in advancing biomedical applications. By synthesizing NDs through various methods and modifying their surfaces, researchers can tailor their properties for specific biomedical needs. The ability of NDs to serve as efficient drug delivery vehicles holds promise for targeted therapy, while their applications in hyperthermic therapy and vaccine enhancement offer innovative approaches to cancer treatment and immunization. Furthermore, the integration of NDs into biosensors enhances diagnostic capabilities, enabling rapid and sensitive detection of biomolecules and infectious diseases. Overall, the diverse functionalities of NDs underscore their potential as valuable tools in nanomedicine, paving the way for advancements in healthcare and biotechnology.

Production, surface modification, physicochemical properties, biocompatibility, and bioimaging applications of nanodiamonds

Nanodiamonds (ND) are chemically inert and stable owing to their sp3 covalent bonding structure, but their surface sp2 graphitic carbons can be easily homogenized with diverse functional groups via oxidation, reduction, hydrogenation, amination, and halogenation. Further surface conjugation of NDs with hydrophilic ligands can boost their colloidal stability and functionality. In addition, NDs are non-toxic as they are made of carbons. They exhibit stable fluorescence without photobleaching. They also possess paramagnetic and ferromagnetic properties, making them suitable for use as a new type of fluorescence imaging (FI) and magnetic resonance imaging (MRI) probe. In this review, we focused on recently developed ND production methods, surface homogenization and functionalization methods, biocompatibilities, and biomedical imaging applications as FI and MRI probes. Finally, we discussed future perspectives.

Zero-Dimensional Carbon Nanomaterials for Fluorescent Sensing and Imaging

Advances in nanotechnology and nanomaterials have attracted considerable interest and play key roles in scientific innovations in diverse fields. In particular, increased attention has been focused on carbon-based nanomaterials exhibiting diverse extended structures and unique properties. Among these materials, zero-dimensional structures, including fullerenes, carbon nano-onions, carbon nanodiamonds, and carbon dots, possess excellent bioaffinities and superior fluorescence properties that make these structures suitable for application to environmental and biological sensing, imaging, and therapeutics. This review provides a systematic overview of the classification and structural properties, design principles and preparation methods, and optical properties and sensing applications of zero-dimensional carbon nanomaterials. Recent interesting breakthroughs in the sensitive and selective sensing and imaging of heavy metal pollutants, hazardous substances, and bioactive molecules as well as applications in information encryption, super-resolution and photoacoustic imaging, and phototherapy and nanomedicine delivery are the main focus of this review. Finally, future challenges and prospects of these materials are highlighted and envisaged. This review presents a comprehensive basis and directions for designing, developing, and applying fascinating fluorescent sensors fabricated based on zero-dimensional carbon nanomaterials for specific requirements in numerous research fields.

Transparent Colloids of Detonation Nanodiamond: Physical, Chemical and Biological Properties

Aqueous suspensions (colloids) containing detonation nano-diamond (DND) feature in most applications of DND and are an indispensable stage of its production; therefore, the interaction of DND with water is actively studied. However, insufficient attention has been paid to the unique physico-chemical and biological properties of transparent colloids with low DND content (≤0.1%), which are the subject of this review. Thus, such colloids possess giant dielectric permittivity which shows peculiar temperature dependence, as well as quasi-periodic fluctuations during slow evaporation or dilution. In these colloids, DND interacts with water and air to form cottonwool-like fibers comprising living micro-organisms (fungi and bacteria) and DND particles, with elevated nitrogen content due to fixation of atmospheric N2. Prolonged contact between these solutions and air lead to the formation of ammonium nitrate, sometimes forming macroscopic crystals. The latter was also formed during prolonged oxidation of fungi in aqueous DND colloids. The possible mechanism of N2 fixation is discussed, which can be attributable to the high reactivity of DND.

The role of nanoparticle charge in crystallization kinetics and ice adhesion strength for dispersions of detonation nanodiamonds

According to the classical nucleation theory, the presence of solid particles in a liquid should facilitate its heterogeneous nucleation upon supercooling. Here, we have analysed the behaviour of aqueous dispersions of detonation diamond nanoparticles (DND) with different signs of the surface charge in supercooled conditions and the frozen state. The behaviours of the diamond nanoparticles with a typical size of 4.5 nm were compared with each other and with deionized water in ice nucleation and ice shear experiments. The presented experimental data and analysis allowed the description of the significant increase in the freezing delay times for positively charged nanoparticles and the sharp decrease for negatively charged ones in comparison to deionized water, based on the peculiarities of the water structure around the nanoparticles and in the vicinity of a superhydrophobic surface. In addition, this approach has allowed the successful explanation of the difference in the practical work of adhesion for deionized water and dispersions of DND with different particle charges.

Nanothermometry with Enhanced Sensitivity and Enlarged Working Range Using Diamond Sensors

Nanothermometry is increasingly demanded in frontier research in physics, chemistry, materials science and engineering, and biomedicine. An ideal thermometer should have features of reliable temperature interpretation, high sensitivity, fast response, minimum disturbance of the target's temperature, applicability in a variety of environments, and a large working temperature range. For applications in nanosystems, high spatial resolution is also desirable. Such requirements impose great challenges in nanothermometry since the shrinking of the sensor volume usually leads to a reduction in sensitivity.Diamond with nitrogen-vacancy (NV) centers provides opportunities for nanothermometry. NV center spins have sharp resonances due to their superb coherence. NV centers are multimodal sensors. They can directly sense magnetic fields, electric fields, temperature, pressure, and nuclear spins and, through proper transduction, measure other quantities such as the pH and deformation. In particular, their spin resonance frequencies vary with temperature, making them a promising thermometer. The high thermal conductivity, high hardness, chemical stability, and biocompatibility of diamond enable reliable and fast temperature sensing in complex environments ranging from erosive liquids to live systems. Chemical processing of diamond surfaces allows various functionalities such as targeting. The small size and the targeting capability of nanodiamonds then enable site-specific temperature sensing with nanoscale spatial resolution. However, the sensitivity of NV-based nanothermometry is yet to meet the requirement of practical systems with a large gap of a few orders of magnitude. On the other hand, although NV-based quantum sensing works well from 0.3 to 600 K, extending the sensing scheme to high temperature remains challenging due to uncertainty in identifying the exact physical limits and possible solution at elevated temperatures.This Account focuses on our efforts to enhance the temperature sensitivity and widen the working temperature range of diamond-based nanothermometry. We start with explaining the working principle and features of NV-based thermometry with examples of applications. Then a transducer-based concept is introduced with practical schemes to improve the sensitivity of the nanodiamond thermometer. Specifically, we show that the temperature signal can be transduced and amplified by adopting hybrid structures of nanodiamond and magnetic nanoparticles, which results in a record temperature sensitivity of 76 μK/√Hz. We also demonstrate quantum sensing with NV at high temperatures of up to 1000 K by adopting a pulsed heating-cooling scheme to carry out the spin polarization and readout at room temperature and the spin manipulation (sensing) at high temperatures. Finally, unsolved problems and future endeavors of diamond nanothermometry are discussed.

Universal Dependence of Nuclear Spin Relaxation on the Concentration of Paramagnetic Centers in Nano- and Microdiamonds

An analysis of our data on ¹H and ¹³C spin-lattice and spin-spin relaxation times and rates in aqueous suspensions of purified nanodiamonds produced by detonation technique (DNDs), DNDs with grafted paramagnetic ions, and micro- and nanodiamonds produced by milling bulk high-temperature high-pressure diamonds is presented. It has been established that in all the studied materials, the relaxation rates depend linearly on the concentration of diamond particles in suspensions, the concentration of grafted paramagnetic ions, and surface paramagnetic defects produced by milling, while the relaxation times exhibit a hyperbolic dependence on the concentration of paramagnetic centers. This is a universal law that is valid for suspensions, gels, and solids. The results obtained will expand the understanding of the properties of nano- and microdiamonds and will be useful for their application in quantum computing, spintronics, nanophotonics, and biomedicine.

Recent Synergy of Nanodiamonds: Role in Brain-Targeted Drug Delivery for the Management of Neurological Disorders

The aim of the present review article is to summarize the role of nanodiamonds in various neurological diseases. We have taken related literature of making this review article from ScienceDirect, springer, Research gate, PubMed, Sci-finder, etc. The current approaches for treating neurological conditions such as glioblastoma includes chemotherapy or combination anti-retro viral therapy for HIV (human immunodeficiency virus) or use of anti-Alzheimer drugs during cognitive impairment. These approaches can provide only symptomatic relief as they do not target the cause of the disease due to their inability to penetrate the blood brain barrier. On long-term use, they may cause CNS toxicity due to accumulation in the brain. So nanodiamonds could prove as a promising approach in the brain targeting of the bioactive and to treat many neurological disorders such as Alzheimer's disease, Parkinson's disease, brain tumor (glioblastoma), HIV, amyotrophic multiple sclerosis, Huntington disease, stroke (cerebrovascular attack), batten disease, schizophrenia, epilepsy, and bacterial infections (encephalitis, sepsis, and meningitis) due to their ability to penetrate the blood-brain barrier and owing to their excellent surface properties, i.e., nano size and high surface area, ease of functionalization, multiple drug binding, and biocompatibility; they can be useful for brain targeted drug delivery with minimal side effects.

Recent Developments of Nanodiamond Quantum Sensors for Biological Applications

Measuring certain quantities at the nanoscale is often limited to strict conditions such as low temperature or vacuum. However, the recently developed nanodiamond (ND) quantum sensing technology shows great promise for ultrasensitive diagnosis and probing subcellular parameters at ambient conditions. Atom defects (i.e., N, Si) within the ND lattice provide stable emissions and sometimes spin-dependent photoluminescence. These unique properties endow ND quantum sensors with the capacity to detect local temperature, magnetic fields, electric fields, or strain. In this review, some of the recent, most exciting developments in the preparation and application of ND sensors to solve current challenges in biology and medicine including ultrasensitive detection of virions and local sensing of pH, radical species, magnetic fields, temperature, and rotational movements, are discussed.

New Insights into the Reactivity of Detonation Nanodiamonds during the First Stages of Graphitization

The present study aims to compare the early stages of graphitization of the same DND source for two annealing atmospheres (primary vacuum, argon at atmospheric pressure) in an identical set-up. DND samples are finely characterized by a combination of complementary techniques (FTIR, Raman, XPS, HR-TEM) to highlight the induced modifications for temperature up to 1100 °C. The annealing atmosphere has a significant impact on the graphitization kinetics with a higher fraction of sp²-C formed under vacuum compared to argon for the same temperature. Whatever the annealing atmosphere, carbon hydrogen bonds are created at the DND surface during annealing according to FTIR. A “nano effect”, specific to the <10 nm size of DND, exalts the extreme surface chemistry in XPS analysis. According to HR-TEM images, the graphitization is limited to the first outer shell even for DND annealed at 1100 °C under vacuum.

Mixed sp2-sp3 Nanocarbon Materials: A Status Quo Review

Carbon nanomaterials with a different character of the chemical bond-graphene (sp2) and nanodiamond (sp3)-are the building bricks for a new class of all-carbon hybrid nanomaterials, where the two different carbon networks with sp3 and sp2 hybridization coexist, interacting and even transforming into one another. The extraordinary physiochemical properties defined by the unique electronic band structure of the two border nanoallotropes ensure the immense application potential and versatility of these all-carbon nanomaterials. The review summarizes the status quo of sp2 - sp3 nanomaterials, including graphene/graphene-oxide-nanodiamond composites and hybrids, graphene/graphene-oxide-diamond heterojunctions, and other sp2-sp3 nanocarbon hybrids for sensing, electronic, and other emergent applications. Novel sp2-sp3 transitional nanocarbon phases and architectures are also discussed. Furthermore, the two-way sp2 (graphene) to sp3 (diamond surface and nanodiamond) transformations at the nanoscale, essential for innovative fabrication, and stability and chemical reactivity assessment are discussed based on extensive theoretical, computational and experimental studies.

Diamond quantum thermometry: from foundations to applications

Diamond quantum thermometry exploits the optical and electrical spin properties of colour defect centres in diamonds and, acts as a quantum sensing method exhibiting ultrahigh precision and robustness. Compared to the existing luminescent nanothermometry techniques, a diamond quantum thermometer can be operated over a wide temperature range and a sensor spatial scale ranging from nanometres to micrometres. Further, diamond quantum thermometry is employed in several applications, including electronics and biology, to explore these fields with nanoscale temperature measurements. This review covers the operational principles of diamond quantum thermometry for spin-based and all-optical methods, material development of diamonds with a focus on thermometry, and examples of applications in electrical and biological systems with demand-based technological requirements.

The effect of salt and particle concentration on the dynamic self-assembly of detonation nanodiamonds in water

Detonation nanodiamonds (DNDs) are becoming increasingly important in science and technology with applications from drug delivery to tribology. DNDs are known to self-assemble into fractal-like aggregates in water, but their colloidal properties remain poorly understood. Here, the effect of salt and particle concentration on the size and shape of these aggregates is investigated using dynamic light scattering and small-angle X-ray scattering. Our results suggest the existence of two particle aggregate populations with diameters on the scale of 50 nm and 300 nm, respectively. The concentration of NaCl, in the range 0.005-1 mM, does not have a significant effect on the size or shape of the particle aggregates. The hydrodynamic radius of both aggregate populations decreases as the DND concentration increases from 0.01 to 2 mg mL^-1. At the same time, the particle aggregates become denser and their overall shape changes from disk-like to rod-like with increasing DND concentration. We identify unexpected similarities between the aggregate structures observed for DNDs and those commonly observed for concentrated colloidal particles in high salt environments, described by classical colloid aggregation theories. Our results contribute to the fundamental understanding of the colloidal properties of DNDs and pave the way for the engineering of novel nanoparticle-based systems that make use of DNDs' unique colloidal properties for future applications.

Effects of Size and Surface Properties of Nanodiamonds on the Immunogenicity of Plant-Based H5 Protein of A/H5N1 Virus in Mice

Nanodiamond (ND) has recently emerged as a potential nanomaterial for nanovaccine development. Here, a plant-based haemagglutinin protein (H5.c2) of A/H5N1 virus was conjugated with detonation NDs (DND) of 3.7 nm in diameter (ND4), and high-pressure and high-temperature (HPHT) oxidative NDs of ~40-70 nm (ND40) and ~100-250 nm (ND100) in diameter. Our results revealed that the surface charge, but not the size of NDs, is crucial to the protein conjugation, as well as the in vitro and in vivo behaviors of H5.c2:ND conjugates. Positively charged ND4 does not effectively form stable conjugates with H5.c2, and has no impact on the immunogenicity of the protein both in vitro and in vivo. In contrast, the negatively oxidized NDs (ND40 and ND100) are excellent protein antigen carriers. When compared to free H5.c2, H5.c2:ND40, and H5.c2:ND100 conjugates are highly immunogenic with hemagglutination titers that are both 16 times higher than that of the free H5.c2 protein. Notably, H5.c2:ND40 and H5.c2:ND100 conjugates induce over 3-folds stronger production of both H5.c2-specific-IgG and neutralizing antibodies against A/H5N1 than free H5.c2 in mice. These findings support the innovative strategy of using negatively oxidized ND particles as novel antigen carriers for vaccine development, while also highlighting the importance of particle characterization before use.

PVP-coated Gd-grafted nanodiamonds as a novel and potentially safer contrast agent for in vivo MRI

PURPOSE

Testing the potential use of saline suspension of polyvinylpyrrolidone (PVP)-coated gadolinium(Gd)-grafted detonation nanodiamonds (DND) as a novel contrast agent in MRI.

METHODS

Stable saline suspensions of highly purified de-agglomerated Gd-grafted DND particles coated by a PVP protective shell were prepared. T₁ and T₂ proton relaxivities of the suspensions with varying gadolinium concentration were measured at 8 Tesla. A series of ex vivo (phantom) and in vivo dynamic scans were obtained in 3 Tesla MRI using PVP-coated Gd-grafted DND and gadoterate meglumin in equal concentrations of gadolinium, and then T₁ -weighted hyperintensity was compared.

RESULTS

The proton relaxivities of PVP-coated Gd-grafted DND were found to be r₁ = 15.9 ± 0.8 s^-1 mM^-1 and r₂ = 262 ± 15 s^-1 mM^-1 , respectively, which are somewhat less than those for uncoated Gd-grafted DND but still high enough. Ex vivo MRI evaluation of PVP-coated Gd-grafted DND results with a dose-dependent T₁ -weighted hyperintensity with a significant advantage over the same for gadoterate meglumin. The same was found when the 2 contrast agents were tested in vivo.

CONCLUSION

The novel MRI contrast agent - saline suspensions of PVP-coated Gd-grafted DND - provides significantly higher signal intensities than the common tracer gadoterate meglumin, therefore increasing its potential for a safer use in clinics.

Fluorescent and Electron-Dense Green Color Emitting Nanodiamonds for Single-Cell Correlative Microscopy

Correlative light and electron microscopy (CLEM) is revolutionizing how cell samples are studied. CLEM provides a combination of the molecular and ultrastructural information about a cell. For the execution of CLEM experiments, multimodal fiducial landmarks are applied to precisely overlay light and electron microscopy images. Currently applied fiducials such as quantum dots and organic dye-labeled nanoparticles can be irreversibly quenched by electron beam exposure during electron microscopy. Generally, the sample is therefore investigated with a light microscope first and later with an electron microscope. A versatile fiducial landmark should offer to switch back from electron microscopy to light microscopy while preserving its fluorescent properties. Here, we evaluated green fluorescent and electron dense nanodiamonds for the execution of CLEM experiments and precisely correlated light microscopy and electron microscopy images. We demonstrated that green color emitting fluorescent nanodiamonds withstand electron beam exposure, harsh chemical treatments, heavy metal straining, and, importantly, their fluorescent properties remained intact for light microscopy.

Spin-enhanced nanodiamond biosensing for ultrasensitive diagnostics

The quantum spin properties of nitrogen-vacancy defects in diamond enable diverse applications in quantum computing and communications¹. However, fluorescent nanodiamonds also have attractive properties for in vitro biosensing, including brightness², low cost³ and selective manipulation of their emission⁴. Nanoparticle-based biosensors are essential for the early detection of disease, but they often lack the required sensitivity. Here we investigate fluorescent nanodiamonds as an ultrasensitive label for in vitro diagnostics, using a microwave field to modulate emission intensity⁵ and frequency-domain analysis⁶ to separate the signal from background autofluorescence⁷, which typically limits sensitivity. Focusing on the widely used, low-cost lateral flow format as an exemplar, we achieve a detection limit of 8.2 × 10^-19 molar for a biotin-avidin model, 10⁵ times more sensitive than that obtained using gold nanoparticles. Single-copy detection of HIV-1 RNA can be achieved with the addition of a 10-minute isothermal amplification step, and is further demonstrated using a clinical plasma sample with an extraction step. This ultrasensitive quantum diagnostics platform is applicable to numerous diagnostic test formats and diseases, and has the potential to transform early diagnosis of disease for the benefit of patients and populations.

Effects of Fluorescent Diamond Particles FDP-NV-800nm on Essential Biochemical Functions of Primary Human Umbilical Vein Cells and Human Hepatic Cell Line, HepG-2 in vitro (Part VI): Acute Biocompatibility Studies

Background

Recently, we reported the safety and biocompatibility of fluorescent diamond particles, FDP-NV-Z-800nm (FDP-NV) injected intravenously into rats, where no morbidity and mortality were noted over a period of 3 months. The acute effects of FDP-NV-800nm particles on cultured human endothelial and hepatic cells remain unexplored.

Purpose

In this study, we aimed to explore select cellular and biochemical functions in cultured human umbilical endothelial cells (HUVEC) and a human hepatic cancer cell line (HepG-2) exposed to FDP-NV-800 in vitro at exposure levels within the pharmacokinetics (Cmax and the nadir) previously reported in vivo.

Methods

Diverse cellular and biochemical functions were monitored, which cumulatively can provide insights into some vital cellular functions. Cell proliferation and migration were assessed by quantitative microscopy. Mitochondrial metabolic functions were tested by the MTT assay, and cytosolic esterase activity was studied by the calcein AM assay. Chaperons (CHOP), BiP and apoptosis (caspase-3 activation) were monitored by using Western blot (WB). MAPK Erk1/2 signaling was assessed by the detection of the phosphorylated form of the protein (P-Erk 1/2) and its translocation into the cell nucleus.

Results

At all concentrations tested (0.001–0.1mg/mL), FDP-NV did not affect any of the biomarkers of cell integrity of HepG2 cells. In contrast, the proliferation of HUVEC was affected at the highest concentration tested (0.1mg/mL, C_max). Exposure of HUVEC to (0.01 mg/mL) FDP-NV had a mild-moderate effect on cell proliferation as evident in the MTT assay and was absent when proliferation was assessed by direct cell counting or by using the calcein AM assays. In both cell types, exposure to the highest concentration (0.1 mg/mL) of FDP-NV did neither affect FBS-stimulated cell signaling (MAPK Erk1/2 phosphorylation) nor did it activate of Caspase 3.

Conclusion

Our data suggest that FDP-NV-800nm are largely biocompatible with HepG-2 cells proliferation within the pharmacokinetic data reported previously. In contrast, HUVEC proliferation at the highest exposure dose (0.1 mg/mL) responded adversely with respect to several biomarkers of cell integrity. However, since the C_max levels are very short-living, the risk for endothelial injury is likely minimal for slow rate cell proliferation such as endothelial cells.

Nitrogen Fixation and Biological Behavior of Nanodiamond Colloidal Solutions

Detonation-produced nanodiamond, both as a powder (with adsorbed water) and especially when suspended in an aqueous colloid, can support the growth (both aerobic and anaerobic) of bacteria and fungi. These were isolated and identified by microbiological methods, optical and electron microscopy, as species of Penicillium, Purpureocillium, Beaveria, Trichoderma and Aspergillus genera. The C : N molar ratio of the developing fibers (comprising fungal mycelia with attached bacteria and entrapped nanodiamond) decreased from 25 to 11 between the 1^st and 10^th week of incubation (cf. 40 in initial nanodiamond, 4.6 typical for bacteria and 8.3 for fungi), and from 4 to <1 after the 12^th week, as the lysis of microorganisms releases carbon as CO₂ and nitrogen as NH₄ ⁺ or NO₃ ^- . The nitrogen content of the colloid increased by an order of magnitude and more, due to fixation of N₂ by nanodiamond under ambient conditions.The process requires water but not necessarily oxygen present.

Low-Power Laser Graphitization of High Pressure—High Temperature Nanodiamond Films

Laser-induced graphitization of 100 nm monocrystals of diamond particles synthesized by high-pressure high-temperature (HP-HT) methods is not typically observed. The current study demonstrates the graphitization of 150 nm HP-HT nanodiamond particles in ca. 20-μm-thick thin films formed on a glass substrate when the intensity of a focused 633 nm He-Ne laser exceeds a threshold of ~ 33 kW/cm2. Graphitization is accompanied by green luminescence. The structure and morphology of the samples were investigated before and after laser excitation while using X-ray diffraction (XRD), Raman spectroscopy, atomic force (AFM), and scanning electron microscopy (SEM). These observations are explained by photoionization of [Ni-N]- and [N]-centers, leading to the excitation of electrons to the conduction band of the HP-HT nanodiamond films and an increase of the local temperature of the sample, causing the transformation of sp3 HP-HT nanodiamonds to sp2-carbon.

Anomalously High Proton Conduction of Interfacial Water

Water at the solid-liquid interface exhibits an anomalous ionic conductivity and dielectric constant compared to bulk water. Both phenomena still lack a detailed understanding. Here, we report radio-frequency measurements and analyses of the electrodynamic properties of interfacial water confined in nanoporous matrices formed by diamond grains of various sizes, ranging from 5 nm to 0.5 μm in diameter. Contrary to bulk water, the charge-carrying protons/holes in interfacial water are not mutually screened, allowing for higher mobility in the external electric field. Thus, the protonic conductivity reaches a maximum value, which can be 5 orders of magnitude higher than that of bulk water. Our results aid in the understanding of physical and chemical properties of water confined in porous materials and pave the way to the development of new type of highly efficient proton-conductive materials for applications in electrochemical energy systems, membrane separations science, and nanofluidics.

Optical Magnetometry Based on Nanodiamonds with Nitrogen-Vacancy Color Centers

Nitrogen-vacancy color centers in diamond are a very promising medium for many sensing applications such as magnetometry and thermometry. In this work, we study nanodiamonds deposited from a suspension onto glass substrates. Fluorescence and optically detected magnetic resonance spectra recorded with the dried-out nanodiamond ensembles are presented and a suitable scheme for tracking the magnetic-field value using a continuous poly-crystalline spectrum is introduced. Lastly, we demonstrate a remote-sensing capability of the high-numerical-aperture imaging fiber bundle with nanodiamonds deposited on its end facet.

Unusual hygroscopic nature of nanodiamonds in comparison with well-known porous materials

Nanodiamond aggregates have interparticle pores of 4.5 nm on average, exhibiting porous nature involved in their water storage. This work studies the hygroscopic nature of porous nanodiamond aggregates by water absorption based on liquid water droplets. Nanodiamond aggregates show hydrophobicity from the water vapor adsorption. Surprisingly, porous nanodiamond aggregates quickly absorb water droplets at the bulk scale. The volume of absorbed liquid water is comparable to that of the water-absorbing clay Montmorillonite and higher than those of zeolites ZSM-5 and molecular sieve 5A. This hygroscopic nature of nanodiamonds is ascribed to the micro- and mesoporous structure of their aggregates and the special core-shell structure of each nanodiamond particle (wrapped by graphene-like carbon). The absorption rate of liquid water in the porous nanodiamonds is influenced by the surface wettability, while the hygroscopic capacity depends mainly on the hierarchical porosity.

Polymer/nanodiamond composites - a comprehensive review from synthesis and fabrication to properties and applications

Nanodiamond (ND) is an allotrope of carbon nanomaterials which exhibits many outstanding physical, mechanical, thermal, optical and biocompatibility characteristics. Meanwhile, ND particles possess unique spherical shape containing diamond-like structure at the core with graphitic carbon outer shell which intuitively contains many oxygen-containing functional groups at the outer surface. Such superior properties and unique structural morphology of NDs are essentially attractive to develop polymer composites with multifunctional properties. However, despite a long history from the discovery of NDs, which is dated back to the1960s, this nanoparticle has been less explored in the field of polymer (nano)composites compared with other carbon nanomaterials, e.g. carbon nanotube (CNT) and graphene. However, open literature indicates that research works in the field of polymer/ND (PND) composites have gained great momentum in the past half a decade. The present article provides a comprehensive review on recent achievements in ND based polymer composites. This review covers a very broad aspect from the synthesis, purification and functionalization of NDs to dispersion, preparation and fabrication of polymer/ND (PND) composites with a look in their recent applications for both structural and functional basis. Therefore, the review would be useful to pave the way for researchers to take some advancing steps in this respect.

DFT calculations reveal pronounced HOMO-LUMO spatial separation in polypyrrole-nanodiamond systems

The low-cost efficient generation of renewable energy and its blending with societal lifestyle is becoming increasingly pervasive. Diamond-based inorganic-organic hybrid systems may have an immense, yet still mostly unexplored, potential in photovoltaic solar cells applications. In this work, we study the interactions of polypyrrole (PPy) with diamond nanoparticles (so-called nanodiamonds, NDs) by computational density functional theory (DFT) methods. We compute the structural and electronic properties of such hybrid organic-inorganic systems. During modeling, PPy is chemisorbed and physisorbed on (111) and (100) ND edge-like surface slabs terminated with oxygen, hydroxyl, carboxyl, and anhydride functional groups, i.e., in the arrangements most commonly found in real NDs. Moreover, NDs terminated with an amorphous surface layer (a-C:H, a-C:O) are considered to approach realistic conditions even further. In a predominant number of cases, we obtain the spatial separation of HOMO and LUMO at the interface, facilitating exciton dissociation. Further, there is a favorable energy level alignment for charge transport. The theoretical results, therefore, show the promising potential of PPy-ND composites in photovoltaic applications.

Applications of Nanodiamonds in the Detection and Therapy of Infectious Diseases

We are constantly exposed to infectious diseases, and they cause millions of deaths per year. The World Health Organization (WHO) estimates that antibiotic resistance could cause 10 million deaths per year by 2050. Multidrug-resistant bacteria are the cause of infection in at least one in three people suffering from septicemia. While antibiotics are powerful agents against infectious diseases, the alarming increase in antibiotic resistance is of great concern. Alternatives are desperately needed, and nanotechnology provides a great opportunity to develop novel approaches for the treatment of infectious diseases. One of the most important factors in the prognosis of an infection caused by an antibiotic resistant bacteria is an early and rigorous diagnosis, jointly with the use of novel therapeutic systems that can specifically target the pathogen and limit the selection of resistant strains. Nanodiamonds can be used as antimicrobial agents due to some of their properties including size, shape, and biocompatibility, which make them highly suitable for the development of efficient and tailored nanotherapies, including vaccines or drug delivery systems. In this review, we discuss the beneficial findings made in the nanodiamonds field, focusing on diagnosis and treatment of infectious diseases. We also highlight the innovative platform that nanodiamonds confer for vaccine improvement, drug delivery, and shuttle systems, as well as their role in the generation of faster and more sensitive clinical diagnosis.

Using hydrogen isotope incorporation as a tool to unravel the surfaces of hydrogen-treated nanodiamonds

We report here on a robust and easy-to-implement method for the labelling of detonation nanodiamonds (DND) with hydrogen isotopes (deuterium and tritium), using thermal annealing performed in a closed system. With this method, we have synthesized and fully characterized (FTIR, Raman, DLS, 3H/2H/1H and 13C MAS NMR) deuterium-treated and tritium-treated DND and demonstrated the usefulness of isotope incorporation in investigating the surface chemistry of such nanomaterials. For instance, surface treatment with deuterium coupled to FTIR spectroscopy allowed us to discriminate the origin of C-H terminations at the DND surface after the hydrogenation process. As a complementary, tritium appeared very useful for quantification purposes, while 1,2,3H NMR confirmed the nature of the C-1,2,3H bonds created. This isotopic study provides new insights into the characteristics of hydrogen-treated DND.

Controlling the fluorescence properties of nitrogen vacancy centers in nanodiamonds

Control over the formation and fluorescence properties of nitrogen vacancy (NV) centers in nanodiamonds (NDs) is an important factor for their use in medical and sensor applications. However, reports providing a deep understanding of the potential factors influencing these properties are rare and focus only on a few influencing factors. The current contribution targets this issue and we report a comprehensive study of the fluorescence properties of NVs in nanodiamonds as a function of electron irradiation fluence and surface termination. Here we show that process parameters such as defect center interactions, in particular, different nitrogen defects and radiation induced lattice defects, as well as surface functionalities have a strong influence on the fluorescence intensity, fluorescence lifetime and the charge state ratio of the NV centers. By employing a time-correlated single photon counting approach we also established a method for fast macroscopic monitoring of the fluorescence properties of ND samples. We found that the fluorescence properties of NV centers may be controlled or even tuned depending upon the radiation treatment, annealing, and surface termination.

Amphiphilic polymer coated nanodiamonds: a promising platform to deliver azonafide

An amphiphilic polymer is grafted on nanodiamonds to improve the colloidal stability and to deliver an anticancer drug azonafide.