Nanocrystalline Diamond Particles Research Articles

Tailoring optical emission of silicon-vacancy centers in two-dimensional diamond nanosheets via a two-step oxidation approach

Incorporating two-dimensional (2D) diamond nanosheets with fluorescent color centers exhibits great potential in the application of quantum sensing. However, color centers always show poor optical emission in chemical-vapor-deposited (CVD) diamond nanomaterials. To address this issue, Si doped diamond/graphite hybrid films were successfully fabricated in microwave-plasma CVD device. The films consist of diamond-core/graphite-shell nanosheets with high amount of diamond nanocrystalline particles. Two post treatments of acid oxidation and annealing in air were used to tailor photoluminescence (PL) of silicon-vacancy (SiV) centers. The SiV centers in the oxidized samples exhibit small PL increase compared with the as-deposited samples with SiV PL quenching. It is found that the graphite phase is selectively etched away with the presence of nanocrystalline diamond particles during the treatment of acid oxidation while the nanocrystalline diamond particles are efficiently removed with the presence of graphite using the air annealing method. Based on this result, a two-step approach of acid oxidation followed by air annealing was conducted to etch the non-diamond phase, forming diamond nanosheets. The SiV centers exhibit significant PL enhancement with a maximum value of 28 folds, compared with the single-step oxidized samples. The Raman and XPS results reveal that such PL increase originates from direct bonding of oxygen on the sp 3 carbon. Therefore, our work provides a feasible approach to prepare 2D diamond nanosheets with high-brightness color centers.

Diamond formation mechanism in chemical vapor deposition.

It is a key challenge to prepare large-area diamonds by using the methods of high-pressure high-temperature and normal chemical vapor deposition (CVD). The formation mechanism of thermodynamically metastable diamond compared to graphite in low-pressure CVD possibly implies a distinctive way to synthesize large-area diamonds, while it is an intriguing problem due to the limitation of in situ characterization in this complex growth environment. Here, we design a series of short-term growth on the margins of cauliflower-like nanocrystalline diamond particles, allowing us to clearly observe the diamond formation process. The results show that vertical graphene sheets and nanocrystalline diamonds alternatively appear, in which vertical graphene sheets evolve into long ribbons and graphite needles, and they finally transform into diamonds. A transition process from graphite (200) to diamond (110) verifies the transformation, and Ta atoms from hot filaments are found to atomically disperse in the films. First principle calculations confirm that Ta-added H- or O-terminated bilayer graphene spontaneously transforms into diamond. This reveals that in the H, O, and Ta complex atmosphere of the CVD environment, diamond is formed by phase transformation from graphite. This subverts the general knowledge that graphite is etched by hydrogen and sp3 carbon species pile up to form diamond and supplies a way to prepare large-area diamonds based on large-sized graphite under normal pressure. This also provides an angle to understand the growth mechanism of materials with sp2 and sp3 electronic configurations.

Effect of surface oxidation on photoluminescence of silicon vacancy color centers in the nanocrystalline diamond films

The effect of three different surface oxidation approaches (air annealing, acid oxidation and oxygen plasma) on microstructural evolution and silicon vacancy (SiV) photoluminescence (PL) in the nanocrystalline diamond (NCD) films is investigated. All oxidation methods lead to the bonding of oxygen functional groups at diamond surface. The SiV centers exhibit the PL enhancement of about 105-fold in the air-annealed sample, compared with the as-deposited films. Nevertheless, the PL enhancement is about 7-fold and 2-fold in the acid- and plasma- treated samples, respectively. Combination of Raman spectra, HRTEM imaging with cross-sectional oxygen mapping confirms that such different PL behavior originates from the formed different thick oxidation layers. The air oxidation results in a thicker oxidation layer with improved crystallinity than the other two methods. In addition, when the air-annealed films are re-terminated with hydrogen, the SiV PL emission tends to drop remarkably under the same crystallinity. It indicates that hydrogen termination leads to the PL quenching of SiV centers. Therefore, our work reveals that the direct bonding of oxygen to sp3 carbon or the improvement of diamond crystalline quality plays an effective role in the PL enhancement of SiV centers during the oxidation of hydrogen-terminated NCD particles or films.

Compound physical and mechanical effects stimulating metastable diamond formation

Purpose. To synthesize diamond polycrystals in a thermodynamically stable region, and to grow up a single crystal shell under conditions of thermodynamic metastability. To investigate some physical properties and features of the internal structure for synthesized single crystals for the development of new models and hypotheses regarding the issue of diamond genesis. Methodology. Experimental studies using shock-wave effects on a metal alloy containing non-diamond carbon. Methods of infrared and ultraviolet spectroscopy, X-ray phase analysis, electron paramagnetic resonance, isotope analysis, differential thermal analysis, electron microscopy, and others are used. The synthesis of nanocrystalline diamond particles as nuclei for growing single crystals is carried out by the shock-wave method using profiled shock waves. Findings. A complex of physicochemical methods for studying the grown diamond monocrystals has been carried out. The reasons for the discrete growth of diamond and the retention of the central inclusion (a polycrystalline diamond of shock-wave origin) in the process of growth have been established and analyzed. It is shown that the discreteness of diamond formation is characteristic only for thermodynamically metastable conditions. The results of the experiments give grounds to make an assumption about the metastable growth, including of diamonds from primary deposits. Originality. The hypothesis has been developed concerning the origin of diamond nanoparticles in interstellar carbon clouds which refer exclusively to central polycrystalline inclusions in a monocrystal diamond shell. The hypothesis eliminates the scientific contradiction that arises in all cases when attempts are made to interpret the natural discreteness of diamond formation based on the regularities of the graphite-diamond state diagram. Possible causes of discrete diamond formation in nature and the scenario of the formation of diamond nanocrystals in an interstellar cloud of atomic carbon have been considered. Practical value. The value of the experimental research results refers to the development of a non-energy-intensive technology for the growing large diamond monocrystals at temperatures of 5001400 K, and pressures of 105107 Pa.

Synthesis and characterization of nanocrystalline diamond from graphite flakes via a cavitation-promoted process

Herein, we describe the multi-step synthesis and characterization of monodisperse cubic-structured nanocrystalline diamond particles, showing that they can be easily prepared from graphite flakes under ambient conditions. The above synthesis features the conversion of graphite flakes into graphene oxide (via a modified Hummer's method) and its subsequent transformation into nanodiamond under the action of ultrasonication-induced cavitation, with the nucleation and growth of nanodiamond particles being strongly influenced by the incorporation of a specific metal oxide spacer material. Overall, the developed method is demonstrated to be superior to conventionally used ones, exhibiting the advantages of simplicity, high yield, and upscaling potential.

Impact of Nano-Crystalline Diamond Enhanced Hydrophilicity on Cell Proliferation on Machined and SLA Titanium Surfaces: An In-Vivo Study in Rodents.

By coating surfaces with nano-crystalline diamond (NCD) particles, hydrophilicity can be altered via sidechain modifications without affecting surface texture. The present study aimed to assess the impact of NCD hydrophilicity on machined and rough SLA titanium discs on soft tissue integration, using a rodent model simulating submerged healing. Four different titanium discs (machined titanium = M Titanium, NCD-coated hydrophilic machined titanium = M-O-NCD, sand blasted acid etched (SLA Titanium) titanium, and hydrophilic NCD-coated SLA titanium = SLA O-NCD) were inserted in subdermal pockets of 12 Wistar rats. After one and four weeks of healing, the animals were sacrificed. Biopsies were embedded in methyl methacrylate (MMA), and processed for histology. The number of cells located within a region of interest (ROI) of 10 µm around the discs were counted and compared statistically. Signs of inflammation were evaluated descriptively employing immunohistochemistry. At one week, M-O-NCD coated titanium discs showed significantly higher amounts of cells compared to M Titanium, SLA Titanium, and SLA-O-NCD (p < 0.001). At four weeks, significant higher cell counts were noted at SLA-O-NCD surfaces (p < 0.01). Immunohistochemistry revealed decreased inflammatory responses at hydrophilic surfaces. Within the limits of an animal study, M-O-NCD surfaces seem to stimulate cell proliferation in the initial healing phase, whereas SLA-O-NCD surfaces appeared advantageous afterwards.

Enhanced nucleation of diamond on three dimensional tools via stabilized colloidal nanodiamond in electrostatic self-assembly seeding process

Nanocrystalline diamond particles are promising candidates for copious applications in materials science, biology and electronics. In this work, diamond nucleation density was unprecedentedly enhanced via a non-invasive electrostatic self-assembly seeding approach. By addition of glutamic acid to the nanodiamond seeding solution, the positively charged amino-group of glutamic acid, which is adsorbed on nanodiamond particles, enhances the adsorption on negative charged cemented carbide substrate. The highest nucleation density (1.0×1010cm−2) was achieved by utilizing glutamic acid at pH 4 as well as DI water at pH 2.2. This density was 20–1000 times higher than most earlier published results on WC-Co substrate. The concentration of the organic molecule, pH, concentration of ND particles and ultrasonication seeding time were found to be important for the seeding process. The colloidal stability was tweaked by pH of the dispersion and concentration of glutamic acid. The optimized parameters for nanodiamond adsorption on WC-Co substrate were found to be pH 4 at a concentration of 7×10−5M of glutamic acid at a nanodiamond concentration of 0.005wt%, while the seeding was conducted for 30min. The short ultrasonication time inhibits aggregation and void formation due to peeling off of nanodiamond patches at prolonged seeding times. Moreover, diamond thin films were deposited uniformly and densely on end mills made of cemented carbide. This work indicates that electrostatic induced adsorption of diamond nanoparticles is crucial for the development of ultra-high nucleation densities for the growth of high performance nanocrystalline diamond films, especially for micro sized tools with sharp cutting edges. It may serve as an approach for pinhole-free ultra-thin films deposition on micro-electromechanical system, and encapsulation coating in harsh environment.

A double-mediator based whole cell electrochemical biosensor for acute biotoxicity assessment of wastewater

This work investigates the feasibility and sensitivity of a double-mediator based whole cell electrochemical biosensor to detect the acute biotoxicity of wastewater. The lipophilic mediator menadione was used to mediate the intracellular metabolic activities whereas hydrophilic potassium ferricyanide was employed as extracellular electron acceptor to transport the electron from the menadiol to anode. A chitosan hydrogel polymer film with boron-doped nanocrystalline diamond (BND) particles was electrodeposited onto a glassy carbon (GC) electrode to immobilize Saccharomyces cerevisiae cells and the mediators. The feasibility of the as-prepared biosensor was verified by determine the acute biotoxicity of four heavy metal ions(Cu2+, Cd2+, Ni2+, Pb2+), three phenol pollutants (3,5-dichlorophenol, 4-chlorophenol, phenol) and three real wastewater samples. The IC50 values for Cu2+, Cd2+, Ni2+, Pb2+ are 10.12mg/L,13.88mg/L, 17.06mg/L and 34.56mg/L. And the IC50 value is 16.48mg/L, 34.40mg/L and 44.55mg/L for 3,5-dichlorophenol, 4-chlorophenol and phenol, respectively. The results of this work indicate that the double-mediator based whole cell electrochemical biosensor could be applied into the acute toxicity assessment of real wastewater samples with excellent performance and highlight their merit as portable and sensitive, which may providing a reasonable and reliable way for wastewater toxicity online detection.

Characterization of natural carbon particles formed at low temperature UHP conditions

Micro-to-nanosized carbon particles forming symmetrically oriented trails in ultrahigh pressure (UHP) garnet have been studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. Micrometer-sized particles include two distinct morphological types: minor rod-shaped particles, and abundant equidimensional particles, interpreted on the basis of the Raman spectra, as graphite and diamond, respectively. The graphite spectra show structural disorder greater than that found in graphite of other UHP rocks. Most diamond spectra shows additional Raman features due to sp2 carbon phases and weaker and broader Raman bands than metamorphic diamond. The SEM images reveal clear topotactic relationships between garnet, micrometer-sized rods of graphite and equidimensional particles of diamond. The TEM study shows that garnet also contains multiwall nanotubes, nanocrystalline diamond particles and polyhedral carbon+silicate structures. The morphology and the orientation relationships between garnet and micro-to-nanometer graphite-like particles are compatible with formation through co-precipitation of garnet and metastable carbon allotropes. It is suggested that precipitation of disordered sp2 carbon can act as a precursor for diamond formation within the stability field of diamond. The presented data reveal the importance that the metastable carbon structures can have on the formation of diamond.

An Analysis of the Particle Formation and Growth Process of the Nanocrystalline Diamond (NCD) Particles on Various Interlayers

Journal Article An Analysis of the Particle Formation and Growth Process of the Nanocrystalline Diamond (NCD) Particles on Various Interlayers Get access Dong-Bae Park, Dong-Bae Park Precision Analysis & Development Lab, Cooperative Equipment Center, Korea Polytechnic University, Shihung , Korea Search for other works by this author on: Oxford Academic Google Scholar Chan-Hyoung Kang, Chan-Hyoung Kang Departments of Advanced Materials Engineering, Korea Polytechnic University, Shihung, Korea Search for other works by this author on: Oxford Academic Google Scholar Dong-Hyuk Cha Dong-Hyuk Cha Precision Analysis & Development Lab, Cooperative Equipment Center, Korea Polytechnic University, Shihung , Korea Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 21, Issue S3, 1 August 2015, Pages 1185–1186, https://doi.org/10.1017/S1431927615006716 Published: 23 September 2015

Diamond-like carbon electrochemical corrosion resistance by addition of nanocrystalline diamond particles for biomedical applications

Combining chemical and mechanical properties of diamond-like carbon (DLC) films opens the possibilities for its use in electrochemical applications. DLC electrochemical corrosion behavior is heavily dependent on deposition techniques and precursor gas. In this paper, nanocrystalline diamond (NCD) particles were incorporated into DLC films to study NCD-DLC electrochemical corrosion resistance in biomedical area. The films were grown over 316L stainless steel using plasma enhanced chemical vapor deposition. NCD particles were incorporated into DLC during the deposition. Raman scattering spectroscopy and scanning electron microscopy characterized NCD-DLC structure and morphology. Electrochemical Impedance Spectroscopy and potentiodynamic method investigate NCD-DLC electrochemical corrosion behavior in simulated body fluid. The presence of NCD particles increases the DLC corrosion resistance. However, as the NCD concentration increases, the disorder also increases. Therefore, DLC films at lower concentration of NCD particles had the maximum corrosion resistance. From these results, NCD-DLC films can be considered a potential candidate for an anticorrosion material in biomedical applications.

THERMAL STABILITY STUDY OF DIAMOND-LIKE CARBON FILMS CONTAINING CRYSTALLINE DIAMOND NANOPARTICLES

Nanocrystalline diamond (NCD) particles are incorporated into diamond-like carbon (DLC) films in order to prevent NCD-DLC electrochemical corrosion. In the current paper, the thermal stability of these films was investigated. The NCD-DLC films were deposited on 316L stainless steel substrates using plasma enhanced chemical vapor deposition. The grain size of the diamond crystallites and their concentration were varied in order to obtain different NCD-DLC films. The samples were annealed to 50°C for 1 h. The annealing temperature increased until the complete graphitization of the films (ramp of 50°C). Raman scattering spectroscopy was used to evaluate in detail the chemical structure of the DLC and NCD-DLC films. The atomic arrangements and graphitization level according to the increasing temperature are discussed. The influence of NCD particle sizes and concentration on NCD-DLC thermal stability are also discussed. The results showed that the presence of crystalline diamond particles increased the graphitization temperature, which permits the use of NCD-DLC films in high temperature environments.

W 및 Ti 박막 위에서 나노결정질 다이아몬드의 성장 거동

The growth behavior of nanocrystalline diamond (NCD) film has been studied for three different substrates, i.e. bare Si wafer, 1 thick W and Ti films deposited on Si wafer by DC sputter. The surface roughness values of the substrates measured by AFM were Si ) > W () > Ti (). During deposition in the microwave plasma CVD system, NCD particles were formed and evolved to film. For the first 0.5h, the values of NCD particle density were measured as Si Si > Ti. In the case of W substrate, NCD particles were coalesced and evolved to the film in the short time of 0.5 h, which could be attributed to the fact that the diffusion of carbon species on W substrate was fast. The slower diffusion of carbon on Si substrate is believed to be the reason for slower film growth than on W substrate. The surface of Ti substrate was observed as a vertically aligned needle shape. The NCD particle formed on the top of a Ti needle should be coalesced with the particle on the nearby needle by carbon diffusion. In this case, the diffusion length is longer than that of Si or W substrate which shows a relatively flat surface. This results in a slow growth rate of NCD on Ti substrate. As deposition time is prolonged, NCD particles grow with carbon species attached from the plasma and coalesce with nearby particles, leaving many voids in NCD/Ti interface. The low adhesion of NCD films on Ti substrate is related to the void structure of NCD/Ti interface.

Nanocrystalline Diamond Particles Prepared by High-Energy Ball Milling Method

In this present work, nanodiamond (ND) particles were successfully prepared from commercial micron diamond powder at room temperature by high energy ball milling process using an oscillatory mill (SPEX8000). The size reduction and structural evolutions of the milled samples were investigated as a function of the milling time by means of X-ray diffraction, and field emission scanning electron microscopy. The line broadening technique was used to determine the crystallite size and lattice strain. After 40 h of milling, obtained ND particles possessed uniform shape and 25 nm of average particle size. Also, energy dispersive X-ray results revealed the high purity of ND and demonstrated that the purification process using harsh acid mixture were effective to remove metal and non-diamond carbon impurities produced in milling stage. All results propose a scalable method to preparation ND particles as well as nanocrystalline materials.

Morphological analysis and cell viability on diamond-like carbon films containing nanocrystalline diamond particles

The coating of orthopedic prostheses with diamond like-carbon (DLC) has been actively studied in the past years, in order to improve mechanical, tribological properties and promote the material's biocompatibility. Recently, the incorporation of crystalline diamond nanoparticles into the DLC film has shown effective in combating electrochemical corrosion in acidic medias. This study examines the material's biocompatibility through testing by LDH release and MTT, on in vitro fibroblasts; using different concentrations of diamond nanoparticles incorporated into the DLC film. Propounding its potential use in orthopedics in order to increase the corrosion resistance of prostheses and improve their relationship with the biological environment.

Thin film composites of nanocrystalline diamond particles and diamond-like carbon: structural, electrochemical and biological properties

Diamond-like Carbon (DLC) films have been the focus of extensive research in recent years due to their potential application as surface coatings. In this paper, we report the main results obtained in our laboratories from the production and characterization of nanocrystalline diamond particles (NCD) incorporated in DLC films for biomedical applications. The films were growth on 316L stainless steel substrates from a dispersion of NCD nanoparticles in hexane using plasma enhanced chemical vapor deposition. Raman

A Kinetic Study on the Growth of Nanocrystalline Diamond Particles to Thin Film on Silicon Substrate

A kinetic study has been made for the growth of nanocrystalline diamond (NCD) particles to a continuous thin film on silicon substrate in a microwave plasma chemical vapor deposition reactor. Parameters of deposition have been microwave power of 1.2 ㎾, the chamber pressure of 110 Torr, and the Ar/CH4 ratio of 200/2 sccm. The deposition has been carried out at temperatures in the range of 400~700℃ for the times of 0.5~16 h. It has been revealed that a continuous diamond film evolves from the growth and coalescence of diamond crystallites (or particles), which have been heterogeneously nucleated at the previously scratched sites. The diamond particles grow following an h2 = k’t relationship, where h is the height of particles, k’ is the particle growth rate constant, and t is the deposition time. The k’ values at the different deposition temperatures satisfy an Arrhenius equation with the apparent activation energy of 4.37 ㎉/㏖ or 0.19 eV/atom. The rate limiting step should be the diffusion of carbon species over the Si substrate surface. The growth of diamond film thickness (H) shows an H = kt relationship with deposition time, t. The film growth rate constant, k, values at the different deposition temperatures show another Arrhenius-type expression with the apparent activation energy of 3.89 ㎉/㏖ or 0.17 eV/atom. In this case, the rate limiting step might be the incorporation reaction of carbon species from the plasma on the film surface.

Tribological behavior under aggressive environment of diamond-like carbon films with incorporated nanocrystalline diamond particles

Nanocrystalline diamond (NCD) particles are incorporated into diamond-like carbon (DLC) films in order to prevent NCD-DLC electrochemical corrosion. In the current paper, tribological behavior of NCD-DLC films under aggressive solutions is discussed. DLC and NCD-DLC coated steel disks and coated and uncoated steel ball were used under rotational sliding conditions. Raman scattering spectroscopy analyzed the film's atomic arrangements and graphitization level before and after tribocorrosion tests. The NCD-DLC films confirmed to be effective in the corrosion wear resistance under corrosive environments. The results pointed that NCD-DLC films are promising corrosion protective coating in aggressive solutions for many applications.

Enhanced field emission characteristics of boron doped diamond films grown by microwave plasma assisted chemical vapor deposition

Boron doped diamond films were synthesized on silicon substrates by microwave plasma chemical vapor deposition (MPCVD) technique. The effect of B 2O 3 concentration varied from 1000 to 5000 ppm on the field emission characteristics was examined. The surface morphology and quality of films were characterized by scanning electron microscope (SEM) and Raman spectroscopy. The surface morphology obtained by SEM showed variation from facetted microcrystal covered with nanometric grains to cauliflower of nanocrystalline diamond (NCD) particles with increasing B 2O 3 concentration. The Raman spectra confirm the formation of NCD films. The field emission properties of NCD films were observed to improve upon increasing boron concentration. The values of the onset field and threshold field are observed to be as low as 0.36 and 0.08 V/μm, respectively. The field emission current stability investigated at the preset value of ∼1 μA is observed to be good, in each case. The enhanced field emission properties are attributed to the better electrical conductivity coupled with the nanometric features of the diamond films.

Catalytic activity of gold on nanocrystalline diamond support

AbstractA simple and easily realizable method was found for the preparation of supported Au catalyst by sputtering island type gold film onto nanocrystalline diamond particles, that can catalyse CO oxidation to CO2. The oxidation of CO molecules from ambient air was observed and investigated by spectroscopic methods. Characteristic CO peaks of molecules adsorbed on gold surface and an increased intensity of the CO2 bands were detected, indicating the catalyst effect of the Au film. The catalytic efficiency was found to be dependent on the morphology of the deposited gold layer. Our measurements indicate also that CO molecules could adsorb permanently on active Au sites, leading to lowered activity of the catalyst. (© 2010 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)