Diamond Nanocone Research Articles

Oxygen functionalized diamond nanocone arrays coupling cobalt phthalocyanine for enhanced electrochemical CO2 reduction

The development of high-efficiency catalysts plays a crucial role in advancing CO2 electroreduction techniques. Among potential candidates, diamond-based electrocatalysts show promise due to their broad electrochemical windows, which effectively suppress competitive hydrogen evolution and ensure high CO2 reduction efficiency. In this study, we report an integrated electrode composed of oxygen-terminated diamond nanocone (ODcone) with CoPc-molecules anchoring (CoPc/ODcone). The CoPc/ODcone electrodes exhibited remarkable performance, achieving a maximum Faradaic efficiency (FE) of 94.1% for CO at −0.97 V vs reversible hydrogen electrode (RHE), and maintaining an FECO higher than 80% over a wide potential range of −0.67 V to −1.07 V vs RHE. The outstanding performance of the CoPc/ODcone electrode can be attributed to the synergistic effects between the nanostructured diamond surface and the CoPc catalyst. The hydroxyl-rich nature of the diamond surface facilitates the anchoring of CoPc molecules and bonding with Co atoms in CoPc. Simultaneously, the nanostructured diamond with sharp tips enhances CO2 adsorption, thereby improving the catalyst's performance. This study provides valuable insights into the utilization of non-metallic carbon materials, particularly diamond, as metal-free catalysts in CO2 electrochemical reduction and tackles challenges such as low current density and poor Faradaic efficiency, thus contributing to the advancement of more effective catalysts for CO2 electroreduction.

Morphology evolution and non-uniformity removal mechanism analysis of diamond nanocone arrays by reactive ion etching

Microstructures of diamond can be fabricated by reactive ion etching and during this process the evolution of surface morphology can affect the electric field near the microstructure. These changes in the electric field will alter the trajectory of ions, thereby affecting the number of ion bombardments on the surface regions of the microstructure. Consequently, this will affect the removal rate of the material on the microstructure surface and consequently affects the evolution of microstructure morphology. In order to understand the morphology evolution process of diamond during etching. H2 and Ar were used as the reactive gases to etch the nanocrystalline diamond (NCD) films with masks. The electric field near the microstructure and the trajectories of reactive ions was stimulated. The number of H+ and Ar+ bombardments at various regions on the diamond microstructure surface has been recorded and analyzed. By observing the cross-sectional morphology of the microstructure at different periods, the etching process of nanocones was analyzed. The study found that the microstructure of the diamond surface would gradually be etched into convex shaped and waist drum shaped and cone. By stimulating the electric field near the microstructure, it was found that the electric field distorted near the microstructure, causing the electric field lines initially perpendicular to the diamond surface to be diverted. As a result, the trajectory of the particles originally arrived perpendicularly to the diamond surface was distorted and hence they bombarded against the sidewall of the diamond microstructures. The angle between the ion trajectory and the electric field line also increased gradually.

Determining the Dependence of Single Nitrogen-Vacancy Center Light Extraction in Diamond Nanostructures on Emitter Positions with Finite-Difference Time-Domain Simulations.

In this study, we obtained a diamond nanocone structure using the thermal annealing method, which was proposed in our previous work. Using finite-difference time-domain (FDTD) simulations, we demonstrate that the extraction efficiencies of nitrogen-vacancy (NV) center emitters in nanostructures are dependent on the geometries of the nanocone/nanopillar, emitter polarizations and axis depths. Our results show that nanocones and nanopillars have advantages in extraction from emitter dipoles with s- and p-polarizations, respectively. In our simulations, the best results of collection efficiency were achieved from the emitter in a nanocone with s-polarization (57.96%) and the emitter in a nanopillar with p-polarization (38.40%). Compared with the nanopillar, the photon extraction efficiency of the emitters in the nanocone is more sensitive to the depth and polarization angle. The coupling differences between emitters and the nanocone/nanopillar are explained by the evolution of photon propagation modes and the internal reflection effects in diamond nanostructures. Our results could have positive impacts on the design and fabrication of NV center-based micro- and nano-optics in the future.

Effects of Substrate Bias on the Diamond Nanostructure by Reactive Ion Etching

Dense and uniform diamond nanocone arrays on titanium substrate were constructed by using bias-assisted reactive ion etching (RIE) of diamond films in a microwave plasma chemical vapor deposition (MPCVD) system. A hydrogen/argon mixture was employed as work gas with ratio of 3/1. The formation of nanocone structure was generated the lengthways physical bombardment/sputtering by argon ions, and selective chemical reaction of graphite and disordered carbons by hydrogen atoms and ions. The structure, size, and density depended on the substrate bias. The surface morphology of diamond film and nanostructures were characterized by field emission scanning electron microscope (FESME), and the composition of diamond film and nanostructures were characterized by Raman spectra. The Stopping and Range of Trons in Matter (SRIM) software was used to simulate the bombardment effect of the diamond film on different Ar+ ion incident angles during the etching process. The experimental results showed substrate bias at −180 V and −210 V was beneficial to the formation of high density, small size and sharp nanocones, meanwhile larger bias contributed to the formation of large size nanocones. Besides, as-prepared nanocones still maintained significant diamond phase.

Bactericidal activity of biomimetic diamond nanocone surfaces.

The formation of biofilms on implant surfaces and the subsequent development of medical device-associated infections are difficult to resolve and can cause considerable morbidity to the patient. Over the past decade, there has been growing recognition that physical cues, such as surface topography, can regulate biological responses and possess bactericidal activity. In this study, diamond nanocone-patterned surfaces, representing biomimetic analogs of the naturally bactericidal cicada fly wing, were fabricated using microwave plasma chemical vapor deposition, followed by bias-assisted reactive ion etching. Two structurally distinct nanocone surfaces were produced, characterized, and the bactericidal ability examined. The sharp diamond nanocone features were found to have bactericidal capabilities with the surface possessing the more varying cone dimension, nonuniform array, and decreased density, showing enhanced bactericidal ability over the more uniform, highly dense nanocone surface. Future research will focus on using the fabrication process to tailor surface nanotopographies on clinically relevant materials that promote both effective killing of a broader range of microorganisms and the desired mammalian cell response. This study serves to introduce a technology that may launch a new and innovative direction in the design of biomaterials with capacity to reduce the risk of medical device-associated infections.

Structure Transition Mechanism of Single-Crystalline Silicon, g-C3N4, and Diamond Nanocone Arrays Synthesized by Plasma Sputtering Reaction Deposition

Single-crystalline silicon, g-C3N4, and diamond nanocone arrays were synthesized on nickel-covered silicon (100) substrates by a novel method of plasma sputtering reaction deposition. The experimental results show that the morphologies, structures, and composition of the as-grown nanocones strongly depend on the ratios of the inlet mixed gases. The silicon, g-C3N4, and diamond nanocone arrays could be grown at the CH4/(N2 + H2) ratios of about 1/20–1/10, 1/150–1/60, and 0, respectively. The analyses of the optical emission spectra from the discharged plasma indicate that the inlet methane controls the growth of the nanocones by suppressing the H+-sputtering effect to adjust the amounts of the silicon, carbon, and nitrogen atoms attaining the substrate, which determines the composition, structures, and crystallinity of the grown nanocones.

Controlled growth of crystalline g-C3N4 nanocone arrays by plasma sputtering reaction deposition

Vertically and neatly arranged crystalline graphitic C3N4 (g-C3N4) nanocone arrays were firstly synthesized on nickel-covered silicon (100) substrates supported on a graphite frame. Synthesis was accomplished using an abnormal glow discharge plasma sputtering reaction deposition method with a feed gas mixture of CH4, N2 and H2. The experimental results show that the morphologies, structures, composition and photoluminescence of the grown nanostructures strongly depend on the CH4/(N2+H2) ratios (0–1/10). The hexagonal g-C3N4 nanocone arrays were well grown at a CH4/(N2+H2) ratio of around 1/150 as a result of the hydrogen ion sputtering of the graphite frame to generate a lot of carbon atoms, the hydrogen ion etching on the growing graphite structures, and the reaction between the active nitrogen atoms and the sputtered carbon atoms. The g-C3N4 nanocone arrays have the characteristic photoluminescence-peak of g-C3N4 and very nice wettability to the polymer absorber layers. At the higher or lower CH4/(N2+H2) ratios, the silicon or diamond nanocone arrays were grown respectively due to the ion-sputtering of the silicon substrate and the inhibition of CHn-radicals on the H+-sputtering of the graphite frame or the mismatch between the sputtered carbon atoms and the dissociated nitrogen atoms.

One-Step Growth and Shaping by a Dual-Plasma Reactor of Diamond Nanocones Arrays for the Assembling of Stable Cold Cathodes

Arrays of conical-shaped nanodiamond structures are formed on silicon substrate by a single-step CVD process from CH4/H2 mixtures. The formation of these nanocones has been found to depend on interplay between growing and etching during the CVD process carried out in a dual-mode MW/RF plasma reactor. Morphology and structure of the conical-like systems can be controlled by varying the process parameters, and have been investigated by scanning electron microscopy (SEM), reflection high energy electron diffraction (RHEED) and micro-Raman spectroscopy. The Field Emission (FE) properties of different diamond nanocones arrays have been investigated and compared with those of analogous systems in order to assess the feasibility of the present nanomaterials as electron emitters for cold cathodes. The FE behavior is discussed taking into account the structure of the different diamond nanocones.

A diamond nanocone array for improved osteoblastic differentiation.

Efficient delivery of biomolecules to cells is of great importance in biology and medicine. To achieve this, we designed a novel type of densely packed diamond nanocone array to conveniently transport molecules to the cytoplasm of a great number of cells. The nanocone array was fabricated by depositing a thin layer of diamond film on a silicon substrate followed by bias-assisted reactive ion etching. The height of the diamond nanocones varied from 200 nm to 1 μm with tip radii of approximately 10 nm. Our fluorescein and propidium iodide staining results clearly demonstrated that dramatically enhanced delivery of fluorescein into cells was realized without leading to noticeable cell death with the aid of nanocone treatment. As a test case of the drug delivery application of the device, MC-3T3 cells in differentiation medium were applied to the nanocone array for enhanced intracellular delivery of the medium. This was confirmed by the fact that nanocone treated cells experienced much higher differentiation ability at an early stage in comparison with untreated cells. Overall, the results indicate that the diamond nanocone array provides a very simple but yet very effective approach to achieve delivery of molecules to a large number of cells.

Surface Nanostructuring of Boron-Doped Diamond Films and Their Electrochemical Performance

Uniform and vertically aligned nanocone and nanopillar arrays were successfully constructed on heavily boron-doped nanocrysatlline diamond films by carrying out bias-assisted reactive ion etching in hydrogen/argon plasmas. The electrochemical properties of the nanostructured boron-doped diamond films were investigated by cyclic voltammetry using 1 mM [Fe(CN)6](3-/4-) as redox couple. Compared to the planar boron-doped nanocrystalline diamond film electrode, the surface nanostructuring of boron-doped diamond film electrodes demonstrate enhanced sensitivity due to their enlarged electro-active surface areas. The results indicated that boron-doped diamond nanocones and nanopillars are promising electrode materials which benefit to improve the efficiency, sensitivity and reproducibility of biomedical and chemical sensors.

Chemical gases sensing properties of diamond nanocone arrays formed by plasma etching

A uniform diamond nanocone array was formed by plasma etching of diamond film in a hot filament chemical vapor deposition (HFCVD) system. A surface amorphous carbon coating layer, which is formed during CH4/H2 plasma-etching process, was removed by Ar plasma in a reactive ion etching system. The hydrogenation of diamond nanocones was performed in H2 ambience by using the same HFCVD system. The air-diluted NH3 and NO2 gases sensing properties of the diamond cone arrays had been studied by using electric current versus measurement time characteristics at room temperature. The repeatable chemical sensing properties of the hydrogenated diamond cone array sensor are enhanced, in comparison with as-formed diamond film. Surface two-dimensional hole gas structure and greatly increased surface-to-volume ratio both play a key role for the excellent detection performance. As-formed diamond nanocone arrays show a promising prospect for applications as chemical sensor for both reducing (NH3) and oxidizing (NO2) gases.

Synthesis and field electron emission characteristics of diamond multilayer films grown by graphite etching

Diamond multilayer film with nanocrystalline diamond film coated on a layer of diamond nanocone film, was synthesized on silicon substrates by using in situ graphite etching in a hot filament chemical vapour deposition reactor. Many small and sharp protrusions on the surface of the multilayer film were observed using scanning electron microscope and atomic force microscope. The multilayer film exhibits lower turn-on field and larger emission current than flat diamond films and diamond nanocone films. Field electron emission measurements at different residual gas pressures indicate that emission current of the multilayer film shows no obvious degradation and the Fowler–Nordheim (F–N) plots parallel to each other when the residual gas pressure is increased from 10−7 to 10−5 Torr. At a higher pressure of 10−3 Torr, obvious degradation of emission current was observed. The slope of the F–N plot becomes larger, indicating that the work function is increased. The possible reason is that the surface of the multilayer film is fully covered by residual gas molecules.

Field electron emission of carbon-based nanocone films

Diamond nanocone, graphitic nanocone, and mixed diamond and graphitic nanocone films have been synthesized through plasma enhanced hot filament chemical vapor deposition (HFCVD). The field emission properties of these films have been experimentally investigated. The studies have revealed that all three kinds of nanocone films have excellent field electron emission (FEE) properties including low turn-on electric field and large emission current at low electric field. Compared with the diamond nanocone films (emission current of 86 μA at 26 V/μm with the turn-on field of 10 V/μm), the graphitic nanocone films exhibit higher FEE current of 1.8×102 μA at 13 V/μm and a lower turn-on filed of 4 V/μm. The mixed diamond and graphitic nanocone films have been found to posses FEE properties similar to graphitic nanocone films (emission current of 1.7×102 μA at 20 V/μm with the turn-on field of 5 V/μm), but have much better FEE stability than the graphitic nanocone films.

Plasma-enhanced synthesis of diamond nanocone films

Three DC plasma processes in a hot filament reactor were developed to synthesize nanostructured carbon films: (1) pure hydrogen plasma treatment of diamond films pre-coated on silicon substrate, (2) plasma-enhanced hot filament chemical vapor deposition (HFCVD) with a gas mixture of hydrogen and methane and (3) graphite etching in a pure hydrogen plasma. Highly aligned diamond nanocone films were synthesized on silicon substrates pre-coated with diamond films in all three processes. When the silicon substrates were pre-deposited with sparsely distributed diamond particles, diamond and graphitic nanocones were grown simultaneously on substrate areas with and without pre-deposited diamond particles, respectively in the last two processes. All the nanocones have nanometer-size tips and sub micrometer-size roots and are highly aligned with various orientation angles influenced by the direction of the electric field lines near the sample surface. In comparison with the conventional method using a methane and hydrogen mixture, it is found that diamond nanocones synthesized by graphite etching have one order of magnitude higher cone density, lower sp 2 carbon content and grow four times faster.

Simultaneous growth of well-aligned diamond and graphitic carbon nanostructures through graphite etching

A hot filament chemical vapor deposition process based on hydrogen etching of graphite has been developed to synthesize diamond and graphitic carbon nanostructures. Well-aligned diamond and graphitic carbon nanostructured thin films have been synthesized simultaneously on differently pretreated silicon substrates in a pure hydrogen plasma. Graphitic nanocones, diamond nanocones and carbon nanotubes were selectively grown on uncoated, diamond and nickel pre-coated silicon substrates, respectively, in a single deposition process. The nanocones are solid cones with submicron scale roots and nanometer-size sharp tips. The nanotubes are hollow tubes with outer diameter of approximately 50 nm. The orientation of the well-aligned carbon nanostructures depends on the direction of the electric field at the samples surface. Nucleation and growth of diamond on the nanocones were further investigated under similar conditions without plasma. Diamond nanocomposite films have been obtained by depositing a nanocrystalline diamond film on the layer of diamond nanocones.

The effects of bias polarity on diamond deposition by hot-filament chemical vapor deposition

Electric voltages with both polarities were applied to silicon substrates in a hot-filament chemical vapour deposition device to study the biasing effects on deposition of diamond and carbon nanocones. It has been found that positive biasing greatly enhanced diamond nucleation density and improved diamond film quality. On the other hand, negative biasing promotes deposition of dense, well-aligned carbon nanocones. The orientation of the carbon nanocones appears to align with the direction of the electric field lines near the substrate surface.PACS Nos.: 81.15.Gh, 81.05.Uw, 81.07.–b

Plasma-enhanced Deposition of Nano-Structured Carbon Films

By pre-treating substrate with different methods and patterning the catalyst, selective and patterned growth of diamond and graphitic nano-structured carbon films have been realized through DC Plasma-Enhanced Hot Filament Chemical Vapor Deposition (PE-HFCVD). Through two-step processing in an HFCVD reactor, novel nano-structured composite diamond films containing a nanocrystalline diamond layer on the top of a nanocone diamond layer have been synthesized. Well-aligned carbon nanotubes, diamond and graphitic carbon nanocones with controllable alignment orientations have been synthesized by using PE-HFCVD. The orientation of the nanostructures can be controlled by adjusting the working pressure. In a Microwave Plasma Enhanced Chemical Vapor Deposition (MW-PECVD) reactor, high-quality diamond films have been synthesized at low temperatures (310°C-550°C) without adding oxygen or halogen gas in a newly developed processing technique. In this process, carbon source originates from graphite etching, instead of hydrocarbon. The lowest growth temperature for the growth of nanocrystalline diamond films with a reasonable growth rate without addition of oxygen or halogen is 260°C.

The field emission properties of high aspect ratio diamond nanocone arrays fabricated by focused ion beam milling

High aspect ratio diamond nanocone arrays are formed on freestanding diamond film by means of focused ion beam (FIB) milling technology and hot-filament chemical vapor deposition (HFCVD) method. The structure and phase purity of an individual diamond nanocone are characterized by scanning electron microscopy (SEM) and micro-Raman spectroscopy. The result indicatesthat the diamond cones with high aspect ratio and small tip apex radius can be obtained by optimizing the parameters ofFIB milling and diamond growth. The diamond nanocone arrays were also used to study the electron field emission propertiesand electric field shielding effect, finding high emission current density, low threshold and weak shielding effect, all attributable to the high field enhancement factor and suitable cone density of the diamond nanocone emitter.