Diamond-rich crystalline nanosheets seeded with a Langmuir monolayer of arachidic acid on water.

The enigmatic self-assembling ability of nanodiamond (ND) particles has been discovered herein. Diamond-rich crystalline nanosheets with thickness of approximately ∼25 nm were grown from a Langmuir monolayer of arachidic acid (AA) at the interface between air and a dilute aqueous ND solution. Their fine rectangular shapes with uniform uniaxial birefringence indicate appreciable crystallinity, thus supporting that they are hydrated colloidal crystals of homogeneous ND particles.

A simple and soft chemical deaggregation method producing single-digit detonation nanodiamonds.

Detonation nanodiamonds (DNDs) are a class of very small and spherical diamond nanocrystals. They are used in polymer reinforcement materials or as drug delivery systems in the field of nanomedicine. Synthesized by detonation, only the final deaggregation step down to the single-digit nanometer size (<10 nm) unfolds their full potential. Existing deaggregation methods mainly rely on mechanical forces, such as high-power sonication or bead milling. These techniques entail drawbacks such as contamination of the sample and the need for a specialized apparatus. In this paper, we report a purely chemical deaggregation method by simply combining oxidation in air followed by a boiling acid treatment, to produce highly stable single-digit DNDs in a suspension. The resulting DNDs are surface functionalized with carboxyl groups, the final boiling acid treatment removes primary metal contaminants such as magnesium, iron or copper and the nanoparticles remain dispersed over a wide pH range. Our method can be easily carried out in a standard chemistry laboratory with commonly available laboratory apparatus. This is a key step for many DND-based applications, ranging from materials science to biological or medical applications.

Pore-Mouth Structure of Highly Agglomerated Detonation Nanodiamonds.

Detonation nanodiamond aggregates contain water that is removed by thermal treatments in vacuo, leaving available pores for the adsorption of target molecules. A hard hydrogel of detonation nanodiamonds was thermally treated at 423 K for 2 h, 10 h, and 52 h in vacuo to determine the intensive water adsorption sites and clarify the hygroscopic nature of nanodiamonds. Nanodiamond aggregates heated for long periods in vacuo agglomerate due to the removal of structural water molecules through the shrinkage and/or collapse of the pores. The agglomerated nanodiamond structure that results from long heating periods decreases the nitrogen adsorption but increases the water adsorption by 40%. Nanodiamonds heated for long times possess ultramicropores <0.4 nm in diameter in which only water molecules can be adsorbed, and the characteristic mouth-shaped mesopores adsorb 60% more water than nitrogen. The pore mouth controls the adsorption in the mesopores. Long-term dehydration partially distorts the pore mouth, decreasing the nitrogen adsorption. Furthermore, the nitrogen adsorbed at the pore mouth suppresses additional nitrogen adsorption. Consequently, the mesopores are not fully accessible to nitrogen molecules because the pore entrances are blocked by polar groups. Thus, mildly oxidized detonation nanodiamond particles can show a unique molecular sieving behavior.

Electromechanical Characteristics by a Vertical Flip of C70 Fullerene Prolate Spheroid in a Single-Electron Transistor: Hybrid Density Functional Methods.

In this study, the B3LYP hybrid density functional theory was used to investigate the electromechanical characteristics of C70 fullerene with and without point charges to model the effect of the surface of the gate electrode in a C70 single-electron transistor (SET). To understand electron tunneling through C70 fullerene species in a single-C70 transistor, descriptors of geometrical atomic structures and frontier molecular orbitals were analyzed. The findings regarding the node planes of the lowest unoccupied molecular orbitals (LUMOs) of C70 and both the highest occupied molecular orbitals (HOMOs) and the LUMO of the C70 anion suggest that electron tunneling of pristine C70 prolate spheroidal fullerene could be better in the major axis orientation when facing the gate electrode than in the major (longer) axis orientation when facing the Au source and drain electrodes. In addition, we explored the effect on the geometrical atomic structure of C70 by a single-electron addition, in which the maximum change for the distance between two carbon sites of C70 is 0.02 Å.

Snapshots of the Fragmentation for C70@Single-Walled Carbon Nanotube: Tight-Binding Molecular Dynamics Simulations.

In previously reported experimental studies, a yield of double-walled carbon nanotubes (DWCNTs) at C70@Single-walled carbon nanotubes (SWCNTs) is higher than C60@SWCNTs due to the higher sensitivity to photolysis of the former. From the perspective of pyrolysis dynamics, we would like to understand whether C70@SWCNT is more sensitive to thermal decomposition than C60@SWCNT, and the starting point of DWCNT formation, which can be obtained through the decomposition fragmentation of the nanopeapods, which appears in the early stages. We have studied the fragmentation of C70@SWCNT nanopeapods, using molecular dynamics simulations together with the empirical tight-binding total energy calculation method. We got the snapshots of the fragmentation structure of carbon nano-peapods (CNPs) composed of SWCNT and C70 fullerene molecules and the geometric spatial positioning structure of C70 within the SWCNT as a function of dynamics time (for 2 picoseconds) at the temperatures of 4000 K, 5000 K, and 6000 K. In conclusion, the scenario in which C70@SWCNT transforms to a DWCNT would be followed by the fragmentation of C70, after C70, and the SWCNT have been chemically bonding in the early stages. The relative stability of fullerenes in CNPs could be reversed, compared to the ranking of the relative stability of the encapsulated molecules themselves.

Predicting the Number of Graphene-Like Layers on Surface for Commercial Fumed Nanodiamonds with Raman Spectra and Model Calculations.

Nanoscale carbon materials have a broad range of applications in the field of surface and material sciences. Each vibration mode of a Raman and Fourier transform infrared (FT-IR) spectra corresponds to a specific frequency of a bond in the core and surface of the crystal, thus it is highly sensitive to morphology, implying that every band is sensitive to the orientation of the bonds and the atomic weight at either end of the bond. Accordingly, in this study we apply transmission electron microscope (TEM), Raman spectroscopies, and model calculations to study the relative content of carbon-carbon (C-C) bonds to the anhydrous and weakly aggregated elementary nanoscale carbon particles of detonation nanodiamonds. One point of the Raman bands at approximately 1300 cm-1 established that there are highly uniform C-C bonds in a tetrahedral crystal field environment not unlike that of diamonds. Another point at approximately 1600 cm-1 would be a hexagonal graphene-like sheet. By analyzing the relative content of carbon bonds using the area of intensity of the Raman peaks and a simulation of crystal morphology, we suggest that the number of graphene surface layers would be monolayers in nanodiamonds, comprising two kinds of C-C bonds, one being sp3 bonds of diamond in the core and the other being sp2 bonds of graphene on the surface.

Dynamic self-assembly of detonation nanodiamond in water.

Nanodiamonds are increasingly used in many areas of science and technology, yet, their colloidal properties remain poorly understood. Here we use direct imaging as well as light and X-ray scattering reveal that purified detonation nanodiamond (DND) particles in an aqueous environment exhibit a self-assembled lace-like network, even without additional surface modification. Such behaviour is previously unknown and contradicts the current consensus that DND exists as mono-dispersed single particles. With the aid of mesoscale simulations, we show that the lace network is likely the result of competition between a short-ranged electrostatic attraction between faceted particles and a longer-ranged repulsion arising from the interaction between the surface functional groups and the surrounding water molecules which prevents complete flocculation. Our findings have significant implications for applications of DND where control of the aggregation behaviour is critical to performance.

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.

Interaction of Polymethine Dyes with Detonation Nanodiamonds.

Among cationic, anionic, and merocyanine polymethine dyes, the binding to detonation nanodiamond (DND) colloid particles in hydrosol occurs only for negatively charged dye species. This, in view of the positive ζ-potential of the DND used in this study, suggests the predominance of electrostatic interactions over other intermolecular forces in such systems. Indeed, after decorating the merocyanine and the cationic dye by one and two negatively charged sulfopropyl groups, respectively, so that the net charge of their colored species becomes negative, the compounds also demonstrate affinity to the DND particles. In all cases, the binding of dyes to DND is accompanied by a decrease in fluorescence intensity and a bathochromic shift of their absorption and fluorescence bands. A quantitative study of the dyes adsorption on the DND nanoparticles as performed using the Küster-Freundlich and Langmuir equations reveals some peculiarities of their attaching to the DND aggregates and allows estimating the specific area of the DND particles at a concentration of 0.0212 wt/vol %.

Size dependent surface reconstruction in detonation nanodiamonds.

Nanometer-sized diamond particles are used in bio-medical applications, where the nature of the nanodiamond surfaces is crucial to achieving correct functionalisation. Herein, using high-resolution transmission electron microscopy and electronic structure calculations, we study the surface reconstructions that occur in detonation-synthesized nanodiamonds. Our results show that particles smaller than 3 nm exhibit size- and shape-dependent surface reconstructions, and that the surfaces can exhibit a higher-than-expected fraction of sp2+x bonding. This indicates an aliphatic character for sub-3 nm nanodiamond particles. Such behaviour impacts the functionality of nanodiamonds, where both size and surface charge can drive performance. Our observations offer a potential strategy for better functionalization control via the size range of the particles.

Clinical validation of a nanodiamond-embedded thermoplastic biomaterial.

Detonation nanodiamonds (NDs) are promising drug delivery and imaging agents due to their uniquely faceted surfaces with diverse chemical groups, electrostatic properties, and biocompatibility. Based on the potential to harness ND properties to clinically address a broad range of disease indications, this work reports the in-human administration of NDs through the development of ND-embedded gutta percha (NDGP), a thermoplastic biomaterial that addresses reinfection and bone loss following root canal therapy (RCT). RCT served as the first clinical indication for NDs since the procedure sites involved nearby circulation, localized administration, and image-guided treatment progress monitoring, which are analogous to many clinical indications. This randomized, single-blind interventional treatment study evaluated NDGP equivalence with unmodified GP. This progress report assessed one control-arm and three treatment-arm patients. At 3-mo and 6-mo follow-up appointments, no adverse events were observed, and lesion healing was confirmed in the NDGP-treated patients. Therefore, this study is a foundation for the continued clinical translation of NDs and other nanomaterials for a broad spectrum of applications.

Water Adsorption Property of Hierarchically Nanoporous Detonation Nanodiamonds.

The detonation nanodiamonds form the aggregate having interparticle voids, giving a marked hygroscopic property. As the relationship between pore structure and water adsorption of aggregated nanodiamonds is not well understood yet, adsorption isotherms of N2 at 77 K and of water vapor at 298 K of the well-characterized aggregated nanodiamonds were measured. HR-TEM and X-ray diffraction showed that the nanodiamonds were highly crystalline and their average crystallite size was 4.5 nm. The presence of the graphitic layers on the nanodiamond particle surface was confirmed by the EELS examination. The pore size distribution analysis showed that nanodiamonds had a few ultramicropores with predominant mesopores of 4.5 nm in average size. The water vapor adsorption isotherm of IUPAC Type V indicates the hydrophobicity of the nanodiamond aggregates, with the presence of hydrophilic sites. Then the hygroscopic nature of nanodiamonds should be associated with the surface functionalities of the graphitic shell and the ultramicropores on the mesopore walls.

Biocompatibility Assessment of Detonation Nanodiamond in Non-Human Primates and Rats Using Histological, Hematologic, and Urine Analysis.

Detonation nanodiamonds (DNDs) have been widely explored for biomedical applications ranging from cancer therapy to magnetic resonance imaging due to several promising properties. These include faceted surfaces that mediate potent drug binding and water coordination that have resulted in marked enhancements to the efficacy and safety of drug delivery and imaging. In addition, scalable processing of DNDs yields uniform particles. Furthermore, a broad spectrum of biocompatibility studies has shown that DNDs appear to be well-tolerated. Prior to the clinical translation of DNDs for indications that are addressed via intravenous administration, comprehensive assessment of DND safety in both small and large animal preclinical models is needed. This article reports the results of a DND biocompatibility study in both non-human primates and rats. The rat study was performed as a multiple dose subacute investigation in two cohorts that lasted for 2 weeks and included histological, serum, and urine analysis. The non-human primate study was performed as a dual gender, multiple dose, and long-term investigation in both standard/clinically relevant and elevated dosing cohorts that lasted for 6 months and included comprehensive serum, urine, histological, and body weight analysis. The results from these studies indicate that NDs are well-tolerated at clinically relevant doses. Examination of dose-dependent changes in biomarker levels provides important guidance for the downstream in-human validation of DNDs for clinical drug delivery and imaging.

Counting vacancies and nitrogen-vacancy centers in detonation nanodiamond.

Detonation nanodiamond particles (DND) contain highly-stable nitrogen-vacancy (N-V) centers, making it important for quantum-optical and biotechnology applications. However, due to the small particle size, the N-V concentrations are believed to be intrinsically very low, spawning efforts to understand the formation of N-V centers and vacancies, and increase their concentration. Here we show that vacancies in DND can be detected and quantified using simulation-aided electron energy loss spectroscopy. Despite the small particle size, we find that vacancies exist at concentrations of about 1 at%. Based on this experimental finding, we use ab initio calculations to predict that about one fifth of vacancies in DND form N-V centers. The ability to directly detect and quantify vacancies in DND, and predict the corresponding N-V formation probability, has a significant impact to those emerging technologies where higher concentrations and better dispersion of N-V centres are critically required.

Probing Interfacial Water on Nanodiamonds in Colloidal Dispersion.

The structure of interfacial water layers around nanoparticles dispersed in an aqueous environment may have a significant impact on their reactivity and on their interaction with biological species. Using transmission soft X-ray absorption spectroscopy in liquid, we demonstrate that the unoccupied electronic states of oxygen atoms from water molecules in aqueous colloidal dispersions of nanodiamonds have a different signature than bulk water. X-ray absorption spectroscopy can thus probe interfacial water molecules in colloidal dispersions. The impacts of nanodiamond surface chemistry and concentration on interfacial water electronic signature are discussed.

Information Entropy of Fullerenes.

The reasons for the formation of the highly symmetric C60 molecule under nonequilibrium conditions are widely discussed as it dominates over numerous similar fullerene structures. In such conditions, evolution of structure rather than energy defines the processes. We have first studied the diversity of fullerenes in terms of information entropy. Sorting 2079 structures from An Atlas of Fullerenes [ Fowler , P. W. ; Manolopoulos , D. E. An Atlas of Fullerenes ; Oxford : Clarendon , 1995 . ], we have found that the information entropies of only 14 fullerenes (<1% of the studied structures) lie between the values of C60 and C70, the two most abundant fullerenes. Interestingly, buckminsterfullerene is the only fullerene with zero information entropy, i.e., an exclusive compound among the other members of the fullerene family. Such an efficient sorting demonstrates possible relevance of information entropy to chemical processes. For this reason, we have introduced an algorithm for calculating changes in information entropy at chemical transformations. The preliminary calculations of changes in information entropy at the selected fullerene reactions show good agreement with thermochemical data.

The impact of structural polydispersivity on the surface electrostatic potential of nanodiamond.

The discovery of the multipolar surface electrostatic potential on faceted diamond nanoparticles explained numerous observations over the past decades, but also raised questions as to how it could be reconciled with seemingly contradictory observations of micron sized diamond and bulk diamond surfaces. It was also unclear how surface electrostatic potential would vary for more quasi-spherical shapes, and derivatives of the ideal truncated octahedron. Here we present new results examining the size-dependence of the multi-polar surface electrostatic potential up to experimentally relevant sizes, and explore the impact of {110} facets which have been shown to present in reasonable quantities (experimentally). We have used computational methods that are consistent with previous work to allow for a direct comparison, and show that both particle size and the fraction of {110} facets on nanodiamond play a critical role in the surface charge. When the particle size is below ~2.5 nm multipoles are likely to dominate, but over ~3.0 nm the {110} facets efficiently neutralize the charges leading to a practically monopolar distribution, consistent with observations at other length scales.

Communication: three-dimensional model for phonon confinement in small particles: quantitative bandshape analysis of size-dependent Raman spectra of nanodiamonds.

Raman spectroscopy of nano-scale materials is facing a challenge of developing a physically sound quantitative approach for the phonon confinement effect, which profoundly affects the phonon Raman band shapes of small particles. We have developed a new approach based on 3-dimensional phonon dispersion functions. It analyzes the Raman band shapes quantitatively in terms of the particle size distributions. To test the model, we have successfully obtained good fits of the observed phonon Raman spectra of diamond nanoparticles in the size range from 1 to 100 nm.

The spatial diamond-graphite transition in detonation nanodiamond as revealed by small-angle neutron scattering.

A spatial transition of the carbon state in detonation nanodiamond (DND) from crystalline diamond inside the particle to a graphite-like state at the DND surface is proposed on the basis of small-angle neutron scattering (SANS) analysis. The SANS contrast variation from concentrated (5 wt%) dispersions of DND in liquids (water, dimethylsulfoxide) reveals a shift in the mean scattering length density of DND as compared to pure diamond, which is related to the presence of a non-diamond component in the DND structure. At the same time, the diffusive character of the particle surface is deduced based on the deviation from the Porod law. The two observations are combined to conclude that the continuous radial density profile over the whole particle volume conforms to a simple power law. The profile naturally suggests that non-diamond states are concentrated mainly close to the particle surface; still there is no sharp boundary between the radial distributions of the two states of carbon in DND.

Diamond-lipid hybrids enhance chemotherapeutic tolerance and mediate tumor regression.

Self-assembled nanodiamond-lipid hybrid particles (NDLPs) harness the potent interaction between the nanodiamond (ND)-surface and small molecules, while providing a mechanism for cell-targeted imaging and therapy of triple negative breast cancers. Epidermal growth factor receptor-targeted NDLPs are highly biocompatible particles that provide cell-specific imaging, promote tumor retention of ND-complexes, prevent epirubicin toxicities and mediate regression of triple negative breast cancers.