Nanodiamond Layers Research Articles

Staged dendrite suppression for high safe and stable lithium-sulfur batteries

The unavoidable dendrite growth and shuttle effect have long been stranglehold challenges limiting the safety and practicality of lithium-sulfur batteries. Herein, we propose a dual-action strategy to address the lithium dendrite issue in stages by constructing a multifunctional surface-negatively-charged nanodiamond layer with high ductility and robust puncture resistance on polypropylene (PP) separator. The uniformly loaded compact negative layer can not only significantly enhance electron transmission efficiency and promote uniform lithium deposition, but also reduce the formation of dendrite during early deposition stage. Most importantly, under the strong puncture stress encountered during the deterioration of lithium dendrite growth under limiting current, the high ductility and robust puncture resistance (145.88 MPa) of as-obtained nanodiamond layer can effectively prevent short circuits caused by unavoidable lithium dendrite. The Li||Li symmetrical cells assembled with nanodiamond layer modified PP demonstrated a stable cycle of over 1000 h at 2 mA cm−2 with a polarization voltage of only 29.3 mV. Additionally, the negative charged layer serves as a physical barrier blocking lithium polysulfide ions, effectively mitigating capacity attenuation. The improved cells achieved a capacity decay of only 0.042% per cycle after 700 cycles at 3 C, demonstrating effective suppression of dendrite growth and capacity attenuation, showing promising prospect.

Moderator developments in HighNESS and feedback to compact sources design

The main, high-brightness neutron source for ESS is based on the low-dimensional moderator concept, and will serve the initial suite of neutron scattering instruments. In the HighNESS project several design options have been identified and investigated for a second source for ESS, intended to be complementary to the primary one. The emphasis of this project, completed in September 2023, was on the design of high-intensity sources, delivering Cold, Very Cold (VCN), and Ultra-Cold Neutrons (UCN). Remarkable results include: a cold moderator based on liquid deuterium capable of delivering an intensity close to a factor 10 greater than the ESS upper moderator; a VCN moderator based on solid deuterium at 5 K, surrounded by nanodiamond layers, delivering brightness above 40 Å an order of magnitude higher than a conventional cold moderator placed in the same location; and several design options for UCN sources based on the use of superfluid helium and solid deuterium. The use of these new sources would have a major impact on fundamental physics experiments and neutron scattering techniques. We investigate the possible impact that these concepts can have for compact sources, with particular emphasis on VCN.

High-Energy Excimer Annealing of Nanodiamond Layers.

Here, we aimed to achieve exposure of a nanodiamond layer to a high-energy excimer laser. The treatment was realized in high-vacuum conditions. The carbon, in the form of nanodiamonds (NDs), underwent high-temperature changes. The induced changes in carbon form were studied with Raman spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction (XRD) and we searched for the Q-carbon phase in the prepared structure. Surface morphology changes were detected by atomic force microscopy (AFM) and scanning electron microscopy (SEM). NDs were exposed to different laser energy values, from 1600 to 3000 mJ cm-2. Using the AFM and SEM methods, we found that the NDs layer was disrupted with increasing beam energy, to create a fibrous structure resembling Q-carbon fibers. Layered micro-/nano-spheres, representing the role of diamonds, were created at the junction of the fibers. A Q-carbon structure (fibers) consisting of 80% sp3 hybridization was prepared by melting and quenching the nanodiamond film. Higher energy values of the laser beam (2000 and 3000 mJ cm-2), in addition to oxygen bonds, also induced carbide bonds characteristic of Q-carbon. Raman spectroscopy confirmed the presence of a diamond (sp3) phase and a low-intensity graphitic (G) peak occurring in the Q-carbon form samples.

Pressure Sensor Devices Featuring a Chemical Passivation Made of a Locally Synthesized Diamond Layer

The rear side of a pressure sensor diaphragm is prepared with an additional diamond layer as protective coating against harsh media. The preparation sequence for the diamond coating is developed as a simple backend process, combining only two additional steps in the standard process. These are the local seeding of nanodiamond layer and the low‐temperature diamond growth at <300 °C in a linear antenna microwave plasma‐enhanced chemical vapor deposition reactor, where only at the nanodiamond seeded sites, a high‐quality diamond film was synthesized. The seeding resolution in the setup used was limited to ≈80 μm, but can be further reduced. In an industry‐typical assembly sequence the diamond coated pressure sensor devices are further equipped with a support wafer and mounted to a TO‐8 socket. Tests of such sensor systems indicate that the diamond layer does not hamper the stability of the device. This proofed method of postprocessing an only‐local and low‐temperature synthesis of a diamond layer on the wafer‐level opens‐ up possibilities for many other applications, since this approach is scalable and in general cost effective.

Novel nanodiamond coatings for durable xenogenic heart valve prostheses: Mechanical properties and in vivo stability

Nanodiamond adsorption coatings were obtained on the surface of the collagen tissue crosslinked by glutaraldehyde for enhancing its mechanical properties, including stress at break, elongation at break, and elastic modulus (Young's modulus). The effect of nanodiamonds of positive and negative surface charge was compared. Negatively charged nanodiamonds strongly influenced the mechanical characteristics compared with positively charged particles on the background of its smaller surface concentration that was determined using tritium-labeled nanodiamonds. A chitosan layer was applied from the solution of supercritical CO2 to prevent calcification of the tissue. In vivo experiments showed that the nanodiamond layer is stable and does not lead to additional calcification of the tissue. However, we observed higher metal concentrations on the tissue covered with negatively charged nanodiamonds. Note that the total calcification of bovine pericardium was less than for non-covered tissue. Our data revealed that layer-by-layer applied nanodiamond and chitosan films significantly enhance the mechanical properties of the bovine pericardium and allowed us to hope for the creation of a wear-resistant material based on it.

Nanodiamond photocathodes for MPGD-based single photon detectors at future EIC

We are developing gaseous photon detectors for Cherenkov imaging applications in the experiments at the future Electron Ion Collider. CsI, converting photons in the far ultraviolet range, is, so far, the only photoconverter compatible with the operation of gaseous detectors. It is very delicate to handle due to its hygroscopic nature: the absorbed water vapour decomposes the CsI molecule. In addition, its quantum efficiency degrades under ion bombardment. These are the key reasons to quest for novel, less delicate materials for photocathodes adequate for gaseous photon detectors. Layers of hydrogenated nanodiamond particles have recently been proposed as an alternative material and have shown promising characteristics. The performance of nanodiamond photocathodes coupled to thick GEM-based detectors is the objects of our ongoing R&D. The first phase of these studies includes the characterization of thick GEM coated with nanodiamond layers and the robustness of its photoconverting properties with respect to the bombardment by ions from the multiplication process in the gaseous detector. The approach is described in detail as well as all the results obtained so far within these exploratory studies.

Emittance evaluation of electron beams produced by photoemission

In this work we study the emittance of electron beams generated by three photocathodes (PCs), one based on Cu sample and two on different nanodiamond (ND) layers. The active layers of the ND-based PCs consisted of untreated and hydrogenated ND particles, 250 nm in size, sprayed on alluminum substrates. We show photoemission measurements performed by a KrF nanosecond excimer laser (λ = 248 nm) in a vacuum chamber at 10−6 mbar and the study of emittance. This last was carried out by the pepper pot method using radiochromic films, HD-810 Gafchromic, as sensible detectors for electrons. The study of the emittance was performed by varying the laser spot onto the PC surface and the accelerating voltage (5, 10 and 15 kV). The obtained results showed quantum efficiencies of the ND-based photocathodes higher than that of the reference Cu one, which instead exhibited the lowest value of normalized emittance, 0.2 mm mrad.

Geometric and electromagnetic characterization of electron beams produced by nanodiamond photocathodes

In this work, the geometric and electromagnetic characteristics of electron beams generated by three photocathodes (PCs), two based on nanodiamond (ND) layers and one based on Cu (generally used as reference) were investigated. Specifically, the active layers of the ND-based PCs consisted of untreated and hydrogenated (H-ND) nanoparticles (250 nm in size) deposited by pulsed spray technique on p-doped silicon substrates as uniform coating. Photoemission measurements carried out by a KrF nanosecond excimer laser (λ = 248 nm) in a vacuum chamber at 10−6 mbar and the emittance evaluation, performed by the pepper pot method, are reported and discussed. For the last, radio-chromic films (HD-810 Gafchromic) were used as sensible screen for electrons. The study of the emittance was performed by varying the laser spot onto the PC surface and the accelerating voltage (5, 10 and 15 kV) . From emittance values, the normalized brightness was also estimated for all the cathodes. The obtained results showed quantum efficiency values of the ND-based photocathodes higher than that of the reference Cu one, but, at the same time, higher emittances and therefore worse performancers as the result of the enlarged beam divergence. Despite this, H-ND resulted to be the best PC between those investigated for the highest normalized beam brightness, thanks to its high electron current and low normalized emittance.

Electron beams produced by innovative photocathodes based on nanodiamond layers

The investigation of two different photocathodes (PCs) based on nanodiamond (ND) layers, irradiated by a KrF nanosecond excimer laser (wavelength, $\ensuremath{\lambda}=248\text{ }\text{ }\mathrm{nm}$; photon energy, ${E}_{\mathrm{Ph}}=5\text{ }\text{ }\mathrm{eV}$) is reported. The ND layers were deposited by means of a pulsed spray technique. Specifically, the active layer of each PC consisted of untreated (as-received) and hydrogenated ND particles, 250 nm in size, sprayed on a $p$-doped silicon substrate. The ND-based photocathodes were tested in a vacuum chamber at ${10}^{\ensuremath{-}6}\text{ }\text{ }\mathrm{mbar}$ and compared to a Cu-based one, used as reference. All the photocathodes were irradiated at normal incidence. The quantum efficiency (QE) of the photocathodes was assessed. QE values of the ND-based photocathodes were higher than that of the reference one. In particular, the hydrogenated ND-based PC exhibited the highest QE due to the negative electron affinity that results from the surface terminated by hydrogen. Additionally, the photocathode surface/local temperature and the multiphoton process contribution to the electron emission were studied.

Optical properties of nano- and ultrananocrystalline diamond thin layers in the UV and visible spectral range

The potential application of nano- and ultrananocrystalline diamond thin films in nanotechnology demands a detailed knowledge of the optical properties and their relation to the structure. By varying the atomic bonding structure and morphological properties of nanodiamond layers we have explored a relation between the structure and the spectral dependence of the refractive index and extinction coefficient in nanodiamond. For this purpose nanodiamond layers were prepared from CH4, H2 and Ar gas mixture in a chemical vapor deposition process with different Ar-content of the feed gas and self-bias of the substrate material. Optical parameters were determined by using a three-layer model in the evaluation of the spectral ellipsometric data. Surface topography was monitored and the average grain size was obtained from scanning electron microscopy images. Bonding characteristics of diamond and non-diamond phases were analyzed by Raman spectroscopy.

UV photocathodes based on nanodiamond particles: Effect of carbon hybridization on the efficiency

Photocathodes working in reflection-mode are made of rich-diamond (R-D) and rich-graphite (R-G) nanodiamond (ND) layers, deposited on different conductive substrates by means of the pulsed spray technique at low deposition temperatures (120 and 150°C) and starting from two types of ND particles. The two powders with an average grain size of 250nm have variable sp2 (graphite phase) and sp3 (diamond phase) hybridized carbon contents, as assessed by Raman spectroscopy and transmission electron microscopy. The ND particles are employed as-received or treated in H2 microwave plasmas.The principal aim of the paper is the comparative study of R-D and R-G photocathodes in the vacuum ultraviolet spectral range from 140 to 210nm, where they exhibit a high quantum efficiency and a good stability over time upon exposure to air. Specifically, the quantum efficiency values at 140nm of photocathodes based on hydrogenated R-D and R-G layers are 26.8 and 47%, respectively, proving that the more defective ND particles are, the more efficiently they emit. Moreover, these QE values are higher than those derived by photocathodes based on microwave plasma enhanced chemical vapor deposition diamond films (14% at 140nm) and the highest recorded in the state of international art.

One-pot green process for surface layering with nanodiamonds on polymer microspheres

This paper demonstrates a simple, yet versatile method for fabricating polymer particles covered with a thin nanodiamond layer by mixing polymer particles with nanodiamonds in supercritical carbon dioxide (scCO2) without using any surfactants or special solvents. The surface layering of nanodiamonds was probably based on softening of polymer particles by swelling with scCO2 and adhesive attachment of nanodiamonds on the surface of polymer particles. Our method enables control of the thickness of nanodiamonds-layered shell by scCO2 conditions such as temperature and pressure and is applicable to other inorganic nanomaterials.

Morphological and Electrical Characterization of Pillar-Like Structures in Nanodiamond Layers

The self-assembly of pillar-like structures in nanodiamond (ND) layers was obtained by means of the pulsed spray technique. This technique enabled to deposit ND layers directly on silicon substrate using a dispersion of as-received 250 nm nanocrystals. The chemical and structural properties of the ND layer were determined by Raman and photoluminescence spectroscopies and the morphological features were measured by confocal and atomic force microscopies. Self-assembled pillar-like structures were observed by both microscopies. The local electrical voltage and current of an isolated ND pillar were studied by scanning Kelvin probe microscopy and scanning capacitance microscopy (SCM), respectively. The electrical data obtained showed that the single pillar features an increase of voltage and a decrease of current. A theoretical model based on the finite element method confirmed the current behavior measured by SCM.

Highly efficient and stable ultraviolet photocathode based on nanodiamond particles

Nanodiamond (ND) layers on silicon substrate are deposited by the pulsed spray technique starting from nanoparticles of about 250 nm dispersed in 1,2-dichloroethane solvent. The aim of this letter is to investigate the quantum efficiency (QE) of photocathodes based on ND particles in the vacuum ultraviolet spectral range. Various ND layers are examined employing as-received and hydrogenated nanoparticles. As expected, the hydrogen plasma treatment improves strongly the photoemission of the layer giving a QE of 22% at 146 nm. Indeed, this efficiency value is achieved only if the particles are treated in H2 microwave plasma before the growth of the sprayed layer rather than to hydrogenate the already formed one. These QE values are higher than those of photocathodes based on plasma chemical vapor deposition diamond films, but with the advantage of being much stable, too. The highest QE values are explained to be due to the intrinsic chemical and structural features of utilized ND particles.

Mass production of fluorescent nanodiamonds with a narrow emission intensity distribution

Fluorescent diamond nanocrystals are attracting increasing interest for a broad range of applications, from biolabeling and single particle tracking to nanoscale magnetic field sensing. Their fluorescence stems from nitrogen-vacancy color centers created within synthetic diamond nanoparticles by high-temperature annealing, which results in the association of pre-existing nitrogen impurities and vacancies generated by high-energy particle (electron, proton, or helium ion) beam irradiation. Up to now, diamond nanocrystals have been irradiated as dry powder in a container or deposited as a thin layer on a flat substrate, depending on the type and energy of the irradiating particles. However, these techniques suffer from intrinsic inhomogeneities: the fluence of particles may vary over the whole sample area, as well as the thickness and density of the nanodiamond layer. Here, we present an approach based on direct large-scale irradiation of nanodiamonds in aqueous colloidal solution by high-energy protons. This approach results in a larger fraction of fluorescent particles, with a more homogenous distribution of nitrogen-vacancy centers per particle and less severe lattice damages compared to dry powder irradiation.

Nanodiamond Coated Glass as a Protective Layer in Solar Cells

Diamond films are very hard and very resistant therefore useful for tribological components, molding parts, among other applications. Adjusting the precursor gas ratio in the gas mixture, a transition from micro- to nanocrystallinity may be achieved. Nanodiamond films possess similar properties as polycrystalline diamond, but with a reduced surface roughness and, thus suitable for application as protective coating. The purpose of this work is to use glass coated with a nanodiamond layer by Hot Filament Chemical Vapor Deposition (HFCVD) as a potential protective layer of a photovoltaic solar cell.

Self-assembled pillar-like structures in nanodiamond layers by pulsed spray technique.

Pillar-like structures of nanodiamonds on a silicon substrate are self-assembled for the first time by a pulsed spray technique. This technique allows us to deposit nanodiamond layers by using high quality nanocrystals of 250 nm dispersed in 1,2-dichloroethane (DCE) solvent. The analysis of 2D/3D confocal and atomic force microscopy images evidences the presence of self-assembled pillar-like structures distributed in an irregular way. The proposed method is simple, easy and cheap, and does not require complex growth processes or structured materials, ideal for upscaling toward industrial biochip implementation and photonic applications. The suggested formation mechanisms of self-assembly are based on the so-called coffee stain effect, i.e., on the time evolution of DCE evaporation.

Piezoelectrically actuated diamond cantilevers for high-frequency applications

In this work, we present a proof-of-concept for the modulation of field emission currents from boron doped nano-diamond based micro-electro-mechanical cantilevers. This modulation was achieved by variations in anode–cathode spacing using mechanical oscillations of the field emitting tips by means of piezoelectric actuation of an aluminum nitride layer. In these devices, the nano-diamond layers serve as a multifunctional material as they are used as field emitters, elastic layers in a unimorph layer stack and as electrodes for piezo-actuation. The cantilevers are processed using conventional micro-fabrication technology and are enhanced by focused ion beam milling, introducing nano-scale features. In addition, it is shown that a stress compensating geometry is efficient to counteract the large thermally induced strain in the nano-materials used.

Microstructures and photovoltaic properties of C60 based solar cells with copper oxides, CuInS2, phthalocyanines, porphyrin, PVK, nanodiamond, germanium and exciton diffusion blocking layers

Organic solar cells have a potential for use in lightweight, flexible, inexpensive and large scale solar cells. However, significant improvements of photovoltaic efficiencies are mandatory for use in future solar power plants. One of the improvements is donor–acceptor proximity in the devices, which are called bulk heterojunction solar cells. Bulk heterojunction is an efficient method to generate free charge carriers, and the charge transfer is possible at the semiconductor interface. The purpose of the present work is to fabricate and characterise C60 based solar cells with copper oxides, CuInS2, phthalocyanines, porphyrin, poly-vinylcarbazole, nanodiamond, germanium and exciton diffusion blocking layers. In the present work, C60 and fullerenol [C60(OH)10–12] were used for n-type semiconductors, and metal copper oxides, metal phthalocyanine derivative, porphyrin and poly-vinylcarbazole were used for p-type semiconductors. In addition, nanodiamond and germanium based molecules were added into the active layers of the solar cells. The novel aspect of the research is to investigate the relation between properties and microstructures of the solar cells using transmission electron microscopy, X-ray diffraction and electronic structure calculation. The impact of the research concerns the study of organic solar cells by means of microstructural analysis, property measurements and theoretical calculations.

Diamond photonic crystal slab: Leaky modes and modified photoluminescence emission of surface-deposited quantum dots

Detailed analysis of a band diagram of a photonic crystal (PhC) slab prepared on a nano-diamond layer is presented. Even though the PhC is structurally imperfect, the existence of leaky modes, determined both theoretically and experimentally in the broad spectral region, implies that an efficient light interaction with a material periodicity occurs in the sample. It is shown that the luminescence emission spectrum of a light source placed directly on the PhC surface can be modified by employing the optical modes of the studied structure. We stress also the impact of intrinsic optical losses of the nano-diamond on this modification.