Ultrananocrystalline Diamond Research Articles

The ultra-low friction mechanism of diamond film by in-situ forming of graphene sheet on sliding interface

In the present study, a novel process of in-situ fabrication of graphene sheets on ultrananocrystalline diamond (UNCD) film with aid of Au layer catalyst was designed. An in-situ ultra strong CC bonds are formed in the graphene-diamond interface under the action of heating, which can decrease the friction coefficient of the film. Besides, the friction-induced formation of graphene nano-scrolls play a pivotal role in achieving an exceptionally low friction coefficient of 0.025 for annealed Au/UNCD film. The potential structural formation mechanisms and frictional mechanisms have been discussed in detail. The achievement in this work provides a novel insight into the in-situ fabrication of graphene-diamond structure in mechanical fields with outstanding low friction coefficient and anti-wear performance.

Atomic-Scale Friction and Adhesion at Ambient Pressure.

In this Perspective, we present the recent advancement and the prospects of atomic-scale friction and adhesion measurements across the pressure gap between ultrahigh vacuum and ambient pressure environments using variable-pressure atomic force microscopy (VP-AFM). We introduce the VP-AFM that enables nanotribological studies under various gas conditions with partial pressure ranging from UHV (1.0 × 10-10 mbar) to 1 bar. We highlight the frictional behaviors of ultrananocrystalline diamond surface in oxygen and water gas environments, as well as the chemical states probed with near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS). The atomic scale degradation processes of MA(CH3NH3)PbBr3, which is an organic-inorganic hybrid perovskite (OHP) investigated with VP-AFM are introduced. Finally, we discuss the potential works on catalytic model systems including bimetallic Pt3Ni(111) and TiO2(110) and the future perspective of nanotribology under ambient conditions.

Microstructure control and mechanical properties of ultra-nanocrystalline diamond films

Ultra-nanocrystalline diamond (UNCD) films exhibit excellent mechanical properties because of their unique structure, such as small grain size and high grain boundary ratio. The effect of nitrogen atoms in nitrogen-doped UNCD films on their structure and mechanical properties deserves in-depth study. In this study, we focus on the microstructure control of UNCD films and its effect on the mechanical properties. Ultra-nanocrystalline diamond films were prepared using microwave plasma chemical vapor deposition under varying nitrogen flow rates. It was observed that the hardness and elastic modulus of UNCD films initially increased and then decreased with the increase of nitrogen flow rate. The structure of UNCD films was characterized using transmission electron microscopy and the crystal quality was analyzed through Raman spectroscopy. Nitrogen-interstitial atom defects were identified in the photoluminescence spectra. These defects contribute to shorter interatomic bonds and enhance the covalent bonds in the crystalline structure, resulting in an increase in hardness. The sp2/sp3 ratio and effective nitrogen atom concentration in the UNCD film were analyzed by X-ray photoelectron spectroscopy. The results indicate that an increase in the effective nitrogen atom concentration corresponds with a notable reduction in grain size, which is simultaneously accompanied by a rise in the number of grain boundaries. Meanwhile, the increase of sp2 content in the UNCD leads to the increase of grain boundary width and density, resulting in the increase of hardness and elastic modulus. This work provides theoretical basis and experimental guidance for the development of high performance UNCD films through precisely regulating the microstructure.

Novel approach to produce 3D boron-doped diamond for pollutant removal from water

Diamond growth from Chemical Vapor Deposition (CVD) on foreign substrates can require different pretreatment not only to improve the film nucleation but also to assure its adhesion by decreasing the expected film/substrate interface stress. To improve boron-doped film nucleation, growth, and adherence, different substrate pretreatments have been used mainly from the seeding process with diamond powder at various particle sizes. Despite this, the development of diamond growth on a Ti mesh remains difficult because of the requirement of a cohesive film to cover a 3D macroporous sample with varying growth rates based on its distinct network geometry. Then, this work describes a novel approach to growing boron-doped diamond (BDD) and boron-doped ultrananocrystalline diamond (B-UNCD) on titanium dioxide nanotubes (TDNT) produced simultaneously on both sides of Ti mesh by an anodization process. The films were obtained from two-step growth processes by assuring the entire diamond overlay on both TDNT/Ti mesh sides, including their outer/inner surfaces, as a 3D sample. TiO2 - TiC conversion has dominated the renucleation process, facilitating the nanometric scale control. The film morphologies were systematically analyzed by FEG-SEM images at different sample planes and depths for both sample sides at different stages of film growth. The unique morphology of titania nanotubes associated with columnar and/or renucleation development of BDD, considering the film defects and valley, can systematically increase the electrode specific area. Raman spectra showed the film quality and its micro and/or ultrananodiamond structure and the boron doping features. Also, this growth process allowed a dopant-controlled adjustable conductivity. Then, the boron doping levels for both films were evaluated from Mott-Schottky plots at around 1019 Bcm−3, characterizing them with good conductivity. In addition, electrochemical measurements from Cyclic Voltammetry (CV) confirmed the expected diamond response on redox pair following the quasi-reversible criteria as high-performance diamond electrodes and in situ Raman spectroelectrochemical measurements assessed the stability of samples during electrochemical measurements, ensuring structural integrity. Finally, the samples were applied to the degradation of methylene blue, proving to be superior materials for electrochemical applications due to their advantages compared to those of similar 2D electrodes.

A new generation of transformational long implanted life dental implants

A new generation of transformational long implanted life dental implants Unique low-cost/best biocompatible Ultrananocrystalline Diamond (UNCD™) coating enables a new generation of transformational long implanted life dental implants. This article summarizes the materials science/properties, integration strategies, and design/development of a new generation of dental implants (DIs) based on coating commercial Ti-alloy (Ti-6Al-4V) DIs with a unique transformational/low-cost/best biocompatible (because they are made of carbon atoms/element of life in human DNA/cells/molecules) ultrananocrystalline diamond (UNCD) coating.

Time-Resolved X-ray Emission Spectroscopy and Resonant Inelastic X-ray Scattering Spectroscopy of Laser Irradiated Carbon.

The existence of liquid carbon as an intermediate phase preceding the formation of novel carbon materials has been a point of contention for several decades. Experimental observation of such a liquid state requires nonthermal melting of solid carbon materials at various laser fluences and pulse properties. Reflectivity experiments performed in the mid-1980s reached opposing conclusions regarding the metallic or insulating properties of the purported liquid state. Time-resolved X-ray absorption studies showed shortening of C-C bonds and increasing diffraction densities, thought to evidence a liquid or glassy carbon state, respectively. Nevertheless, none of these experiments provided information on the electronic structure of the proposed liquid state. Herein, we report the results of time-resolved resonant inelastic X-ray scattering (RIXS) and time-resolved X-ray emission spectroscopy (XES) studies on amorphous carbon (a-C) and ultrananocrystalline diamond (UNCD) as a function of delay time between the irradiating pulse and X-ray probe. For both a-C and UNCD, we attribute decreases in RIXS or XES signals to transition blocking, relaxation, and finally, ablation. Increased signal at 20 ps following the irradiation of the UNCD is attributed to the probable formation of nanoscale structures in the ablation plume. Differences in the amount of signal observed between a-C and UNCD are explained by the difference in sample thickness and, specifically, incomplete melting of the UNCD film. Comparisons to spectral simulations based on MD trajectories at extreme conditions indicate that the carbon state in our experiments is crystalline. Normal mode analysis confirmed that symmetrical bending or stretching of the C-C bonds in the diamond lattice results in XES spectra with small intensity differences. Overall, we observed no evidence of melting to a liquid state, as determined by the lack of changes in the spectral properties for up to 100 ps delays following the melting pulses.

Electrochemical determination of ibuprofen by batch‐injection analysis using a BORON‐doped ultrananocrystalline diamond electrode

AbstractIn this paper, the evaluation of a boron‐doped ultrananocrystalline diamond (BD‐UNCD) electrode for the determination of ibuprofen (IBU) in pharmaceutical formulations using batch‐injection analysis with amperometric detection (BIA‐AD) is presented. The BD‐UNCD electrode was characterized by Raman spectroscopy and the electrochemical measurements were carried out before and after anodic pretreatment. An improved electrochemical response for IBU oxidation was observed using BD‐UNCD as compared to commercial boron‐doped diamond electrode. The optimized method based on the BIA‐AD system was carried out by using 2.0 V as the detection potential, a dispensing rate of 211.9 μL s−1, and an injection volume of 40 μL in an electrochemical cell containing 30.0 mL of 1.0 mol L−1 HClO4 as the supporting electrolyte. The proposed method provided an analytical curve within a linear dynamic range from 1.84 to 20.0 μmol L−1 (R2=0.9967) and a limit of detection of 0.55 μmol L−1. The intra‐day (n=10) and inter‐day (n=2) precisions for IBU concentrations of 5.0 and 10.0 μmol L−1 assessed as relative standard deviation (%RSD) ranged from 2.65 to 5.84 %. The accuracy of the method was assessed through the determination of IBU in pharmaceutical samples (tablets and solutions), yielding results that were consistent with those obtained through the comparative method (HPLC‐DAD).

Ultrafast laser triggered electron emission from ultrananocrystalline diamond pyramid tip cathode

Nitrogen-incorporated ultrananocrystalline diamond [(N)UNCD] pyramid tip cathode has been considered as a next-generation high peak current electron source for dielectric laser accelerators as well as other high peak current particle accelerator applications. In this work, we study non-linear photoemission from an (N)UNCD pyramid tip cathode using an ultrafast laser with the pulse length of 150 fs with the central wavelength of 800 nm in the peak intensity range of 109–1010W/cm2. We demonstrated that as the incident laser intensity increases, the current emitted from the nano-tip first increases as a power function with an exponent of about 5 and then starts to roll over to an exponent of 3. This roll over is attributed to the Coulomb interaction between electrons emitted from the tip also known as the space charge. We also measured the photoemission electron energy spectra that show electrons with energies as high as ∼10 eV. Based on the shape of the electron energy spectra, we conclude that the high-energy electrons are thermally emitted electrons due to ultrafast laser heating at the tip of the (N)UNCD pyramid tip cathode.

Impact of surface treatments on the electron affinity of nitrogen-doped ultrananocrystalline diamond

In recent years, various forms of nanocrystalline diamond (NCD) have emerged as an attractive group of diamond/graphite mixed-phase materials for a range of applications from electron emission sources to electrodes for neural interfacing. To tailor their properties for different uses, NCD surfaces can be terminated with various chemical functionalities, in particular hydrogen and oxygen, which shift the band edge positions and electron affinity values. While the band edge positions of chemically terminated single crystal diamond are well understood, the same is not true for nanocrystalline diamond, which has uncontrolled crystallographic surfaces with a variety of chemical states as well as graphitic grain boundary regions. In this work, the relative band edge positions of as-grown, hydrogen terminated, and oxygen terminated nitrogen-doped ultrananocrystalline diamond (N-UNCD) are determined using ultraviolet photoelectron spectroscopy (UPS), while the band bending is investigated using photoelectrochemical measurements. In contrast to the widely reported negative electrode affinity of hydrogen terminated single crystal diamond, our work demonstrates that hydrogen terminated N-UNCD exhibits a positive electron affinity owing to the increased surface and bulk defect densities. These findings elucidate the marked differences in electrochemical properties of hydrogen and oxygen terminated N-UNCD, such as the dramatic changes in electrochemical capacitance.

Maximizing visible Raman resolution of nanodiamond grains fabricated by coaxial arc plasma deposition through oxygen plasma etching optimization

Among the nondestructive carbon material characterization tools, the prominence of visible Raman spectroscopy has surged remarkably for many years due to its ability to explore a diverse array of carbon bonding configurations. However, to fully unlock the distinctive features concealed within carbon composite materials, additional specimen treatments or precise spectroscope calibrations are necessary. In the same regard, the tiny diamond grain size (5–10 nm) and the pronounced amount of sp2 carbon in the ultrananocrystalline diamond film represent major challenges in visible light excitation. In this work, we employ calibrated oxygen plasma reactive ion etching conditions to manifest the nanodiamond visible Raman signature from ultrananocrystalline diamond/amorphous carbon composite (UNCD/a‐C) films fabricated by coaxial arc plasma deposition. Upon plasma etching, the broad defect band in the visible Raman spectra converged toward the diamond characteristic Raman peak at 1332 cm−1. A detailed explanation of band components of the Raman spectra is extracted through peak fitting procedures. The results of Raman spectroscopy are further correlated with the electrical characteristics of the nitrogen‐doped UNCD/a‐C films due to the optimized oxygen plasma etching processes.

Ultrananocrystalline diamond (UNCD™) coating for new-generation implantable medical devices/prostheses

Ultrananocrystalline diamond (UNCD™) coating for new-generation implantable medical devices/prostheses In this materials science piece, Orlando Auciello, describes the development of a unique multifunctional/best biocompatible ultrananocrystalline diamond (UNCDTM) coating for new-generation implantable medical devices and prostheses. Materials’ surfaces of vital medical devices, such as silicon (Si) microchip (artificial retina) implanted on human retina, restoring partial vision to people blinded by genetically induced photoreceptors degeneration, and metallic dental implants, are attacked chemically by eyes’ fluids or oral fluids respectively. Metallic stents/artificial heart valves, inside human blood vessels, activate blood enzymes, inducing coagulation, and fibrinolytic, leading to thrombus formation (i.e., blood clot in blood vessels, obstructing blood flow or loosed clot getting stuck in arteries/veins’ walls, causing life-threatening stroke/heart attack.

Control of Neuronal Survival and Development Using Conductive Diamond.

This study demonstrates the control of neuronal survival and development using nitrogen-doped ultrananocrystalline diamond (N-UNCD). We highlight the role of N-UNCD in regulating neuronal activity via near-infrared illumination, demonstrating the generation of stable photocurrents that enhance neuronal survival and neurite outgrowth and foster a more active, synchronized neuronal network. Whole transcriptome RNA sequencing reveals that diamond substrates improve cellular-substrate interaction by upregulating extracellular matrix and gap junction-related genes. Our findings underscore the potential of conductive diamond as a robust and biocompatible platform for noninvasive and effective neural tissue engineering.

New diamond coatings for peroxosulphate production

In this work new diamonds coating, named as nanocrystalline diamond (ND) and ultrananocrystalline diamond (UND) are evaluated for the production of peroxospecies derived from the electrolysis of sulphuric acid and their performance is compared to that of a commercial diamond coating widely used in the literature and well-known by its outstanding performance. The oxidant production was tested at two different current densities and significant differences were found in oxidant production between the electrodes applied in the different conditions studied. Results demonstrate that when the lowest current is applied (25 mA cm−2), the ND and UND electrodes are more efficient in the persulfate formation. For ND electrode, this behavior can be explained in terms of the promoted hydroxyl radical formation at these conditions. However, the UND electrode presented different behavior: the lesser hydroxyl formation and highest peroxospecies formation. This behavior may be attributed to the sum of two factors: the high sp2 content in the diamond film and its porosity, that can increase the sulphate adsorption at the surface that, in turn, facilitates the persulfate generation. This behavior can be proved by the Tafel plots and are explained by the electrode’s features discussed by Raman spectra. When the operation current is increased to harsher conditions (300 mA cm−2), the commercial electrode increases importantly the production of the studied oxidant. One more time it can be attributed to the hydroxyl radical generation at this condition. Considering the energy consumption and the process efficiency, it can be concluded that the UND electrode is more attractive for this application in the studied conditions.

CH4/(Ar–H2) plasma post-treatments produce nano-diamond aggregation and improvement in field emission properties of ultrananocrystalline diamond films

CH4/(Ar–H2) plasma post-treatments produce nano-diamond aggregation and improvement in field emission properties of ultrananocrystalline diamond films

(Invited) integration of Microneedles and Electrochemical Sensors for Medical Applications

Microneedles are small-scale devices that may be used for access to interstitial fluid and/or capillary blood for transdermal monitoring of chemicals [1]. In this presentation, the integration of several types of electrochemical sensors with hollow microneedles will be considered. For example, carbon fiber electrodes have been integrated with digital micromirror device-produced microneedles; ascorbic acid and hydrogen peroxide were detected with these devices [2]. Carbon paste electrodes have also been integrated with digital micromirror device-produced microneedles; electrodes made from rhodium-dispersed carbon paste were used for hydrogen peroxide sensing [3]. In addition, lactate oxidase-modified rhodium-dispersed carbon paste electrodes were demonstrated for lactate sensing, including in the presence of interferents such as ascorbic acid, uric acid, and acetaminophen. A multiplexed microneedle array containing digital micromirror device-produced microneedles was subsequently used for amperometric detection of glucose, lactate, and pH; detection of these analytes in complex media was shown [4]. More recently, digital micromirror device-produced hollow microneedles were modified with a working sensor, which was prepared with graphene ink and 4 (3-Butyl-1-imidazolio)-1-butanesulfonate) ionic liquid. Direct oxidation of fentanyl via square-wave voltammetry was shown; a detection limit of 27.8 μM was demonstrated using this approach [5]. Two photon polymerization has also been used to create hollow microneedles for biosensing; a porous carbon electrode created using interference lithography was used for potassium ion sensing in the presence of interfering sodium ions [6]. In another study, nitrogen-incorporated ultrananocrystalline diamond coatings were deposited on Ti –6Al–4V alloy microneedles using microwave plasma enhanced chemical vapor deposition; dopamine and uric acid were electrochemically detected in an in vitro study [7]. These studies indicate that microneedles may have utility for minimally invasive detection of analytes in a real time manner. Benefits and disadvantages of the microneedle-based sensing approach as well as efforts needed for clinical translation of microneedle-based sensing technology will be considered.

Enhanced protein immobilization efficacy by nanostructuring of ultrananocrystalline diamond surface

Enhanced protein immobilization efficacy by nanostructuring of ultrananocrystalline diamond surface

A Review of In-Situ TEM Studies on the Mechanical and Tribological Behaviors of Carbon-Based Materials

Carbon-based materials are widely applied in various devices due to their outstanding mechanical and tribological behaviors. In recent years, more attention has been paid to clarifying the nanocontact mechanisms of carbon-based materials, in order to promote nanoscale applications. The in-situ TEM method is currently the only way that can combine contact behavior and real interface. However, there is still a lack of a systematic summary of in-situ TEM studies on carbon-based materials. Therefore, this work provides an overview of in-situ TEM mechanical and tribological studies on carbon-based materials, consisting of the quantitative actuation and detection for in-situ tests, the strength of fracture and yield, the adhesion between interfaces, the friction performance, and wear features of carbon-based materials with different nanostructures, such as carbon nanotube, graphene, graphite, amorphous, sp2 nanocrystalline, and ultrananocrystalline diamond. Nanostructures play a crucial role in determining mechanical and tribological behaviors. Perspectives on current challenges and future directions are presented, with the aim of promoting the advancement of in-situ TEM research.

Ultrananocrystaline diamond (UNCD™) coatings for new generations high-tech/ medical devices/prostheses

Ultrananocrystaline diamond (UNCD™) coatings for new generations high-tech/ medical devices/prostheses This article provides a summary of materials science, materials integration strategies, materials properties, and design and development of new generations of industrial products, high-tech and external/implantable medical devices/prostheses, and treatment of medical conditions, based on the unique biocompatible Ultrananocrystalline Diamond (UNCD™) coating co-developed by Auciello and colleagues, and key oxide films and nanoparticles, to improve the quality of life of people worldwide. The target audience for this article includes undergraduate/graduate students, postdocs, scientists and engineers in Academia and Industry in different fields of science and technology, including materials scientists, mechanical engineers, bioengineers, applied physicists/chemists, medical device designers/manufacturers, and medical doctors/surgeons, who, by knowing more about biomaterials and devices they are implanting in people, may make better decisions when selecting a device based on the appropriate material for implantation.

Noninvasive Salivary Sensor Based on Ferrocene/ZnO/Nitrogen-Incorporated Nanodiamond/Si Heterojunction Nanostructures for Glucose Sensing in Neutral Conditions

The development of a simple and convenient noninvasive salivary glucose sensor to replace the needle-prick blood collection process can not only enhance early detection and diagnosis but also reduce excess medical care costs due to delayed treatment. This study presents a noninvasive sensor based on a ferrocene/ZnO/nitrogen-incorporated nanodiamond/Si heterojunction structure to measure glucose in saliva. The sensing electrode based on a heterojunction structure composed of ferrocene (FC), Bidens-like zinc oxide (b-ZnO), and nitrogen-incorporated ultra-nanocrystalline diamond (NUNCD) films, which is a kind of nitrogen-incorporated nanodiamond, was constructed on a silicon (Si) substrate. Herein, FC and b-ZnO act as a mediator and a specific surface area promoter, respectively, and NUNCD provides a good nucleation site and conducting path. Glucose oxidase (GOx) was introduced into the system to play the role of enzyme to catalyze the reaction and increase the electrode selectivity. The FC/b-ZnO/NUNCD/Si sensor exhibited superior performance in glucose measurements within the linear ranges (1) 20–100 μM (R2 = 0.9717) with a sensitivity of 1125.18 μA/(mM cm2) and (2) 20–600 μM (R2 = 0.9926) with a sensitivity of 804.11 μA/(mM cm2). Additionally, the sensor has a sensitivity of 1012.35 μA/(mM cm2) within the range 50–400 μM (R2 = 0.9912) for artificial saliva.

The Gemstone Cyborg: How Diamond Films Are Creating New Platforms for Cell Regeneration and Biointerfacing

Diamond is a promising material for the biomedical field, mainly due to its set of characteristics such as biocompatibility, strength, and electrical conductivity. Diamond can be synthesised in the laboratory by different methods, is available in the form of plates or films deposited on foreign substrates, and its morphology varies from microcrystalline diamond to ultrananocrystalline diamond. In this review, we summarise some of the most relevant studies regarding the adhesion of cells onto diamond surfaces, the consequent cell growth, and, in some very interesting cases, the differentiation of cells into neurons and oligodendrocytes. We discuss how different morphologies can affect cell adhesion and how surface termination can influence the surface hydrophilicity and consequent attachment of adherent proteins. At the end of the review, we present a brief perspective on how the results from cell adhesion and biocompatibility can make way for the use of diamond as biointerface.