Size Of Nanodiamonds Research Articles

Graphite to ultrafine nanocrystalline diamond phase transition model and growth restriction mechanism induced by nanosecond laser processing

To have a clear insight into nanocrystal growth from graphite to diamond upon high energy pulsed laser irradiation of graphite suspension, synthesis of ultrafine nanocrystalline diamonds with laser energy set up from 0.3 J to 12 J, repetition rate of 10 Hz has been studied. The method allows synthesizing ultrafine nanocrystalline particles continuously at the ambient temperature and normal pressure. The particle size is shown independent of laser energy, which is ultrafine and ranges in 2–6 nm. The theoretical grown size of nano-diamonds is found in well agreement with the experiment results. Four kinds of production were found: nano-diamond, spherical carbon nano-particles, flocculent amorphous carbon, and graphene nano-ribbon rolls. A solid-vapor-plasma-liquid coexistence model describing phase transition from graphite to diamond induced by nanosecond laser processing was proposed. Graphene nano-ribbon rolls might be the intermediate phase in the conversion from graphite to diamond.

Research Update: Direct conversion of amorphous carbon into diamond at ambient pressures and temperatures in air

We report on fundamental discovery of conversion of amorphous carbon into diamond by irradiating amorphous carbon films with nanosecond lasers at room-temperature in air at atmospheric pressure. We can create diamond in the form of nanodiamond (size range <100 nm) and microdiamond (>100 nm). Nanosecond laser pulses are used to melt amorphous diamondlike carbon and create a highly undercooled state, from which various forms of diamond can be formed upon cooling. The quenching from the super undercooled state results in nucleation of nanodiamond. It is found that microdiamonds grow out of highly undercooled state of carbon, with nanodiamond acting as seed crystals.

Electroplated Ni–B films and Ni–B metal matrix diamond nanocomposite coatings

Electrodeposition of Ni–B films and Ni–B nanocomposite coatings with diamond nanoparticles on steel substrates was performed in a modified Watts bath. The influence of electrodeposition parameters such as saccharine content, concentration of boron precursor and the content of diamond nanoparticles in the electroplating bath were investigated. The impact of the nanodiamond size on the microstructure of the Ni–B nanocomposite coatings was investigated for sizes ranging from 5nm to 100nm. The effects of co-deposited nanodiamond on the hardness and corrosion potential of the coatings was assessed and related to the microstructure. It is demonstrated that the particle size of the nanodiamond affects the texture of the coatings as well as their susceptibility to electrochemical attack in 3.5% NaCl solution. The boron content in the coating has also a strong effect on their microstructure and hardness.

Dipole polarizability of nanodiamonds and related structures

In the present work, mean dipole polarizabilities of the nanodiamonds and the related nanostructures modified with nitrogen vacancy centers or surface functional groups F and OH have been studied by DFT methods. Linear correlation between the mean polarizability and the size of nanodiamonds has been justified. It opens opportunities for prediction of polarizabilities of larger nanodiamond particles without high-cost quantum-chemical calculations. Introducing nitrogen vacancy centers slightly increases the resulting mean polarizability due to the repulsive interactions of lone pairs of N atoms (in A, B, and N3 centers) or unpaired electron (C center). Mean polarizabilities of polyfluorinated and polyhydroxylated nanodiamonds have been calculated for model structures with isolated, focal, and compact arrangements of the F/OHs on the surface. The enhancement of polarizability over the expected additive value has been found for nanodiamonds with compact placement of F/OH and in the case of the polyhydroxylated nanodiamond with the isolated OH groups.

Molecular dynamics-based refinement of nanodiamond size measurements obtained with dynamic light scattering

The determination of particle size by dynamic light scattering uses the Stokes-Einstein relation, which can break down for nanoscale objects. Here we employ a molecular dynamics simulation of fully solvated 1-5 nm carbon nanoparticles for the refinement of the experimental data obtained for nanodiamonds in water by using dynamic light scattering. We performed molecular dynamics simulations in differently sized boxes and calculated nanoparticles diffusion coefficients using the velocity autocorrelation function and mean-square displacement. We found that the predictions of the Stokes-Einstein relation are accurate for nanoparticles larger than 3 nm while for smaller nanoparticles the diffusion coefficient should be corrected and different boundary conditions should be taken into account.

Numerical simulations of nanodiamond nitrogen-vacancy centers coupled with tapered optical fibers as hybrid quantum nanophotonic devices.

Tapered optical fibers are promising one-dimensional nanophotonic waveguides that can provide efficient coupling between their fundamental mode and quantum nanoemitters placed inside them. Here, we present numerical studies on the coupling of single nitrogen-vacancy (NV) centers (single point dipoles) in nanodiamonds with tapered fibers. Our results lead to two important conclusions: (1) A maximum coupling efficiency of 53.4% can be realized for the two fiber ends when the NV bare dipole is located at the center of the tapered fiber. (2) NV centers even in 100-nm-sized nanodiamonds where bulk-like optical properties were reported show a coupling efficiency of 22% at the taper surface, with the coupling efficiency monotonically decreasing as the nanodiamond size increases. These results will be helpful in guiding the development of hybrid quantum devices for applications in quantum information science.

Layer-by-Layer Oxidation for Decreasing the Size of Detonation Nanodiamond

Diamond nanoparticles attract much attention as they combine outstanding mechanical properties with biocompatibility and are available in large quantities. Control and tunability of the particle size is very important for any nanomaterial. Although oxidation can burn carbon and lead to a particle size decrease, this technique could not be successfully employed for nanodiamond size reduction on the nanoscale. In this work, two commercial nanodiamond powders are used to demonstrate separation of the oxidation reaction into two steps (i) the oxygen chemisorption and (ii) the CO and/or CO2 desorption. This allows for an effective control of the oxidation process. In situ thermogravimetric analysis suggests that the oxidation is thermodynamically rather than kinetically controlled, and that the carbon burn off can be adjusted by repeating chemisorption/desorption steps to remove carbon layer after layer. Small-angle X-ray scattering (SAXS) characterization of the diamond nanoparticles showed a continuous size ...

Precise estimation of HPHT nanodiamond size distribution based on transmission electron microscopy image analysis

Abstract Fluorescent nanodiamonds (NDs) are extremely promising fluorescent probes and sensors in experimental biology. For these applications, NDs obtained from high-pressure, high-temperature (HPHT) synthesis are used. Commercial HPHT NDs are polydisperse and of irregular shape. In this work, we used image analysis of transmission electron microscopy (TEM) micrographs to determine the actual size distribution of an HPHT ND sample with high precision. We developed novel TEM sample preparation procedure, which includes hydrophilization of a carbon-coated TEM grid by UV/ozone treatment and subsequent charge reversal and charge-controlled adsorption of nanoparticles. This method results in NDs spread evenly on the grid and radically improves the quality of TEM samples. Image analysis of TEM micrographs of commercial NDs revealed an unexpectedly high abundance of sub-10 nm NDs in the sample. This method can also be used for preparing TEM samples of other negatively charged nanoparticles, such as citrate-stabilized gold.

Mechanistic features of nanodiamonds in the lapping of magnetic heads.

Nanodiamonds, which are the main components of slurry in the precision lapping process of magnetic heads, play an important role in surface quality. This paper studies the mechanistic features of nanodiamond embedment into a Sn plate in the lapping process. This is the first study to develop mathematical models for nanodiamond embedment. Such models can predict the optimum parameters for particle embedment. From the modeling calculations, the embedded pressure satisfies p 0 = (3/2)·(W/πa 2) and the indentation depth satisfies . Calculation results reveal that the largest embedded pressure is 731.48 GPa and the critical indentation depth δ is 7 nm. Atomic force microscopy (AFM), scanning electron microscopy (SEM), and Auger electron spectroscopy (AES) were used to carry out surface quality detection and analysis of the disk head. Both the formation of black spots on the surface and the removal rate have an important correlation with the size of nanodiamonds. The results demonstrate that an improved removal rate (21 nm·min−1) can be obtained with 100 nm diamonds embedded in the plate.

Raman Spectra for Characterization of Onion-Like Carbon

In this work the Raman spectroscopy abilities for diagnostics of carbon onions synthesized from nanodiamonds have been analyzed. Several series of nanodiamonds transformed into onion-like carbon by heating at 1000–1900 K in vacuum were characterized with Raman spectroscopy. A high resolution transmission electron microscopy (HRTEM) was used to estimate the average size of nanodiamonds in the series synthesized by different methods. Each series consisted of a pristine nanodiamond powder and materials appeared after its heat treatment at different temperatures in vacuum. The changes corresponding to the nanodiamond crystal transformation into the onion-like carbon (via the stage of diamond cores enveloped by a few layer graphene) have been revealed in Raman spectra. The basic attention has been paid to behavior of D (disorder-induced), G (graphite) and 2D (two-phonon scattering)-bands in the Raman spectra.

Effects of annealing time on the microstructural and electrochemical properties of B-doped nanocrystalline diamond films

The effects of annealing time under 1000 ℃ on the microstructural and the electrochemical properties of boron-doped nanocrystalline diamond (BDND) films are investigated by HRTEM, UV and visible Raman spectroscopy, and cyclic voltammetry measurements. The results show that the size of nano-diamond grain in the film decreases with annealing time increasing. When the annealing time is 0.5 h, the grain size decreases from about 15 nm in the unannealed sample to about 8 nm and the content of diamond phase increases. When the annealing time increases to 2.0 h, the diamond grain size decreases to 2-3 nm, and the content of diamond phase decreases with the grain boundary increasing. In the case of annealing time of 2.5 h, the grain size of nano-diamond and the content of diamond phase increase slightly. The variations of nano-diamond grain size and the content of diamond phase indicate that the transformation between the diamond phase and the amorphous carbon occurs under the annealing with different times. The visible Raman spectra show that the G-peak position and the ID/IG value exhibit similar variations with annealing time increasing, revealing that the ordering of the amorphous graphite phase is improved when sp2 carbon cluster increases in number or size. The reactions on the electrode surface are quasi-reversible when the annealing times are 0.5, 1.0, 1.5 and 2.0 h. On the contrary, the reactions are irreversible when the sample is unannealed or annealed for 2.5 h. It is observed that the annealing treatment is beneficial to the improvement of the electrode mass transfer efficiency of BDND film. When the annealing time is 0.5 h, the electrode mass transfer efficiency as well as the ability of catalytic oxidation of BDND film is best. The results suggest that the smaller size of nano-diamond grain, the higher content of diamond phase and the uniform distribution of the nanocrystalline diamond grains are conducible to the improvement of the reaction reversibility on the electrode surface and the ability of catalytic oxidation of BDND films.

Size effect of nanodiamonds on P3HT:PCBM heterojunction solar cells

We have used 1.5wt.% of nanodiamonds having three different sizes such as 5, 50 and 250nm for making the hybrid active layer. As the nanodiamond size increased, the root mean square (rms) roughness also increased in the film. The film with nanodiamond has a higher absorption intensity than the P3HT:PCBM film. The power conversion efficiency (PCE) of the device has improved from 1.8% to 2.4%, as a result of increased current density for P3HT:PCBM mixed with nanodiamond having 50nm.

Size-reduction of nanodiamonds via air oxidation

Here we report the size reduction and effects on nitrogen-vacancy centres in nanodiamonds by air oxidation using a combined atomic force and confocal microscope. The average height reduction of individual crystals, as measured by atomic force microscopy, was 10 ± 1 nm/h at 600 °C, 4 ± 1 nm/h at 550 °C, and less than 1 nm/h at 500 °C from air oxidation at atmospheric pressure. The oxidation process modified the surface including removal of non-diamond carbon and organic material which also led to a decrease in background fluorescence. During the course of the nanodiamond size reduction, we observed the annihilation of nitrogen-vacancy centres which provided important insight into the behaviour of colour centres in small crystals. In these unirradiated samples, the smallest nanodiamond still hosting a stable nitrogen-vacancy centre observed was 8 nm.

Convergence in the Evolution of Nanodiamond Raman Spectra with Particle Size: A Theoretical Investigation

Structural characterization of nanodiamonds by vibrational spectroscopy requires knowledge of the factors determining the spectra. Raman spectroscopy is widely used to detect the diamond phase in nanodiamond powders and films, but several spectral features are still poorly understood. Here we present a theoretical study of the evolution of diamond hydrocarbon Raman spectra with increasing size, from the adamantane molecule to approximately 3 nm large tetrahedral and octahedral particles of T(d) symmetry, containing up to about 1000 carbon atoms. The self-consistent-charge density functional tight-binding method (SCC-DFTB) was used for the calculation of harmonic first-order Raman spectra. We demonstrate very good agreement with Raman spectra computed by standard density functional theory (DFT) for the smaller model systems. The evolution of the Raman patterns is smooth, and convergence to the bulk limit could clearly be observed in case of the acoustic vibrational modes (omega(A) = 0 cm(-1)). We found a simple relationship between nanodiamond size and vibrational frequency, which is analogous to the corresponding equation for the radial breathing mode of single-walled carbon nanotubes. The T(2) modes of octahedral diamond hydrocarbons coalesce faster to the bulk optical vibrational mode (in experiment, omega(O) = 1332 cm(-1)) than those of tetrahedral particles, consistent with the fact that the bulk/surface ratio is more favorable for octahedral particles. Our simulations unequivocally show that controversial Raman features around 500 and 1150 cm(-1) do not originate from the nanodiamond crystals, and that the nanocrystal shape plays an important role in the appearance of the Raman spectra even in the 3 nm domain.

On the surface properties of a nanodiamond

The dependences of the specific surface energy, the surface tension, and the surface pressure on the size, the surface shape, and the temperature of a nanodiamond with a free surface have been investigated using the Mie-Lennard-Jones interatomic interaction potential. The nanocrystal has the form of a parallelepiped faceted by the (100) planes with a square base. The number of atoms N in the nanocrystal varies from 5 to ∞. The isothermal isomorphic dependences of the specific surface energy, its isochoric derivative with respect to the temperature, the surface tension, and the surface pressure on the nanodiamond size have been calculated at temperatures ranging from 20 to 4300 K. According to the results of the calculations, the surface energy under this conditions is positive, which indicates that the nanodiamond cannot be fragmented at temperatures up to 4300 K. The surface pressure for the nanodiamond Psf(N) ∼ N−1/3 is considerably less than the Laplace pressure Pls(N)−1/3 ∼ N−1/3 for the same nanocrystal at the given values of the temperature, the density, and the number of atoms N. As the temperature increases from 20 to 4300 K, the lowering of the isotherm Psf(N) is considerably more pronounced than that of the isotherm Pls(N). At high temperatures, the isotherm Psf(N) changes the shape of the size dependence and goes to the range of extension of small nanocrystals. It has been demonstrated that the lattice parameter of the nanodiamond can either decrease or increase with a decrease in the nanocrystal size. The most significant change in the lattice parameter of the nanodiamond is observed at temperatures below 1000 K.

Visualization of nanodiamond formation in molten carbon under pressure

We discuss the characteristics and visualization of simulations of nanodiamond clusters grown from molten carbon. The general trends of nanodiamond size and quality as functions of growth conditions resemble those found experimentally. In particular, the probability of finding nanodiamonds, and their quality increased wth increasing sample density and cooling rate. We also discuss finite size effects and possible phase transitions within molten graphite.

The scattering and extinction properties of nanodiamonds

The study of scattering and extinction properties of possible nanodiamond grains in the ISM are reported. Calculations using Discrete Dipole Approximation (DDA) for varying ellipsoidal shapes and sizes from 2.5 to $10 nm$ are considered. Nanodiamonds show negligible extinction from IR to near-UV and very sharp far-UV rise. Comparison with observations rule out possibility of independent nanodiamond dust but point towards possibility of nanodiamonds as a component in the ISM. Radiation induced transformations may lead to carbonaceous grains with different core and mantles. So calculations are also performed for a core-mantle target model with nanodiamond core in graphite mantles. The graphite extinction features get modified with the peak at 2175 \AA{} being lowered, broadened, blue shifted and accompanied by enhanced extinction in the far-UV. Such variations in the 2175 \AA{} band and simultaneous far-UV rise are observed along some sources. A three component dust model incorporating silicate, graphite and graphite with nanodiamond core is also considered. The model extinction compares very well with the average galactic extinction in the complete range from 0.2 to $10 \mu m^{-1}$. The best fit requires small size and small number of nanodiamonds.

Determination of Size, Morphology, and Nitrogen Impurity Location in Treated Detonation Nanodiamond by Transmission Electron Microscopy

AbstractSize, morphology, and nitrogen impurity location, all of which are all thought to be related to the luminescent properties of detonation nanodiamonds, are determined in several detonation nanodiamond samples using a combination of transmission electron microscopy techniques. Results obtained from annealed and cleaned detonation nanodiamond samples are compared to results from conventionally purified detonation nanodiamond. Detailed electron energy loss spectroscopy combined with model‐based quantification provides direct evidence for the sp3 like embedding of nitrogen impurities into the diamond cores of all the studied nanodiamond samples. Simultaneously, the structure and morphology of the cleaned detonation nanodiamond particles are studied using high resolution transmission electron microscopy. The results show that the size and morphology of detonation nanodiamonds can be modified by temperature treatment and that by applying a special cleaning procedure after temperature treatment, nanodiamond particles with clean facets almost free from sp2 carbon can be prepared. These clean facets are clear evidence that nanodiamond cores are not necessarily in coexistence with a graphitic shell of non‐diamond carbon.

Infrared spectra of hydrogenated nanodiamonds by first-principles simulations

The heat of formation and infrared spectra of hydrogenated nanodiamonds with different morphologies (up to 1.92 nm in diameter) have been investigated using density functional theory. Preferential growth orientation along 〈1 1 1〉 orientations corresponding to an octahedral shape was observed according to the computed heat of formation. The simulated infrared (IR) spectra show distinct dependence on both size and morphology of the nanodiamonds. The major IR peaks in the region of 900–1300 cm −1 shift toward high wavenumber as the nanocluster size increases, while the C–H vibrations in the range 2500–3500 cm −1 show an opposite trend. The present results would be useful for identifying the size and morphology of nanodiamonds in experimental IR spectroscopy.

Special properties of X-ray diffraction on carbon onions

The kinematic theory of X-ray diffraction was applied to the study of the most intense Bragg’s reflection observed for carbon onions. It was shown that the agreement with experimental data was attained using a convolution of a Lorentzian contour with regard to the distribution of onion sizes and of an asymmetric contour taking into account the fluctuations of intershell distances inside the particle. It can be assumed that the observed scatter in intershell distances indicates a nonequilibrium state of the internal configuration of onion shells. It appeared to be possible to estimate not only the average onion size, which exceeds the average size of pristine nanodiamonds that are used for onion preparation by annealing, but their size distribution function as well.