Erbium ion implantation into LiNbO3, Al2O3, ZnO and diamond - measurement and modelling - an overview.

The presented overview deals with the study of the luminescence properties of lanthanide ions incorporated into different dielectric crystalline materials for use in photonics and optoelectronics. From the crystalline materials, non-centrosymmetric hexagonal crystals of LiNbO3, Al2O3 and ZnO, together with the centrosymmetric cubic crystal of diamond, were chosen. The above-mentioned materials represent a certain cross-section through various crystal structure geometries with different internal bonding of atoms which represent different crystal vicinity for the incorporated Er ions. During more than ten years of our research, each of the crystals was doped with erbium ions and the resulting structural and luminescence properties were studied in detail and compared between the mentioned crystalline materials to find similar behaviour for erbium ions in the different crystalline materials. To better understand the incorporation of erbium in the studied crystalline materials, theoretical simulations of different erbium-doped crystal models were carried out. In the calculations, cohesive energies of the structures and erbium defect-formation energies were compared in order to find the most favourable erbium positions in the crystals. Also, from the geometry optimization calculations, the optimal geometry arrangements in the vicinity of erbium ions in different crystals were studied and visualized. The results of the theoretical simulations confirmed the experimental results - i.e., from all the theoretical erbium-doped crystal models, the most stable structures contained erbium in the substitutional positions with octahedral oxygen coordination.

Impact of electrolyte solution on electrochemical oxidation treatment of Escherichia coli K-12 by boron-doped diamond electrodes.

We studied the disinfection efficacy of boron-doped electrodes on Escherichia coli-contaminated water-based solutions in three different electrolytes, physiological solution (NaCl), phosphate buffer (PB), and phosphate buffer saline (PBS). The effect of the electrochemical oxidation treatment on the bacteria viability was studied by drop and spread plate cultivation methods, and supported by optical density measurements. We have found that bacterial suspensions in NaCl and PBS underwent a total inactivation of all viable bacteria within 10 min of the electrochemical treatment. By contrast, experiments performed in the PB showed a relatively minor decrease of viability by two orders of magnitude after 2 h of the treatment, which is almost comparable with the untreated control. The enhanced bacterial inactivation was assigned to reactive chlorine species, capable of penetrating the bacterial cytoplasmic membrane and killing bacteria from within.

Hydrogen-Terminated Diamond Surface as a Gas Sensor: A Comparative Study of Its Sensitivities.

A nanocrystalline diamond (NCD) layer is used as an active (sensing) part of a conductivity gas sensor. The properties of the sensor with an NCD with H-termination (response and time characteristic of resistance change) are measured by the same equipment with a similar setup and compared with commercial sensors, a conductivity sensor with a metal oxide (MOX) active material (resistance change), and an infrared pyroelectric sensor (output voltage change) in this study. The deposited layer structure is characterized and analyzed by Scanning Electron Microscopy (SEM) and Raman spectroscopy. Electrical properties (resistance change for conductivity sensors and output voltage change for the IR pyroelectric sensor) are examined for two types of gases, oxidizing (NO2) and reducing (NH3). The parameters of the tested sensors are compared and critically evaluated. Subsequently, differences in the gas sensing principles of these conductivity sensors, namely H-terminated NCD and SnO2, are described.

Infrared Absorption Spectroscopy of Albumin Binding with Amine-Containing Plasma Polymer Coatings on Nanoporous Diamond Surfaces.

Nanocrystalline diamond (NCD) layers functionalized with amine-containing functional groups have generated considerable interest as biocompatible substrates for attachment of biomolecules and cells with a view to biosensor and tissue engineering applications. Here we prepare nanoporous diamond layers with the surfaces modified by hydrogen plasma, oxygen plasma, and conformal 7 nm amine-containing plasma polymer (PP). Immobilization of bovine serum albumin (BSA) molecules is characterized on such surfaces. Grazing angle reflectance infrared spectroscopy as well as X-ray photoelectron spectroscopy show that concentration of amine-containing bonds after BSA exposure depends on the type of NCD surface modification. AFM measurements reveal that BSA proteins are physisorbed on H- and O-terminated diamond surfaces in different thicknesses and morphology. When the diamond layers are coated with the amine-containing PP, BSA molecules assume similar thickness and morphology, and their adhesion is significantly increased on both types of the diamond surfaces.

Erbium ion implantation into diamond - measurement and modelling of the crystal structure.

Diamond is proposed as an extraordinary material usable in interdisciplinary fields, especially in optics and photonics. In this contribution we focus on the doping of diamond with erbium as an optically active centre. In the theoretical part of the study based on DFT simulations we have developed two Er-doped diamond structural models with 0 to 4 carbon vacancies in the vicinity of the Er atom and performed geometry optimizations by the calculation of cohesive energies and defect formation energies. The theoretical results showed an excellent agreement between the calculated and experimental cohesive energies for the parent diamond. The highest values of cohesive energies and the lowest values of defect formation energies were obtained for models with erbium in the substitutional carbon position with 1 or 3 vacancies in the vicinity of the erbium atom. From the geometry optimization the structural model with 1 vacancy had an octahedral symmetry whereas the model with 3 vacancies had a coordination of 10 forming a trigonal structure with a hexagonal ring. In the experimental part, erbium doped diamond crystal samples were prepared by ion implantation of Er+ ions using ion implantation fluences ranging from 1 × 1014 ions per cm2 to 5 × 1015 ions per cm2. The experimental results revealed a high degree of diamond structural damage after the ion implantation process reaching up to 69% of disordered atoms in the samples. The prepared Er-doped diamond samples annealed at the temperatures of 400, 600 and 800 °C in a vacuum revealed clear luminescence, where the 〈110〉 cut sample has approximately 6-7 times higher luminescence intensity than the 〈001〉 cut sample with the same ion implantation fluence. The reported results are the first demonstration of the Er luminescence in the single crystal diamond structure for the near-infrared spectral region.

Nanocarbon Allotropes-Graphene and Nanocrystalline Diamond-Promote Cell Proliferation.

Two profoundly different carbon allotropes - nanocrystalline diamond and graphene - are of considerable interest from the viewpoint of a wide range of biomedical applications including implant coating, drug and gene delivery, cancer therapy, and biosensing. Osteoblast adhesion and proliferation on nanocrystalline diamond and graphene are compared under various conditions such as differences in wettability, topography, and the presence or absence of protein interlayers between cells and the substrate. The materials are characterized in detail by means of scanning electron microscopy, atomic force microscopy, photoelectron spectroscopy, Raman spectroscopy, and contact angle measurements. In vitro experiments have revealed a significantly higher degree of cell proliferation on graphene than on nanocrystalline diamond and a tissue culture polystyrene control material. Proliferation is promoted, in particular, by hydrophobic graphene with a large number of nanoscale wrinkles independent of the presence of a protein interlayer, i.e., substrate fouling is not a problematic issue in this respect. Nanowrinkled hydrophobic graphene, thus, exhibits superior characteristics for those biomedical applications where high cell proliferation is required under differing conditions.

Development of Composite Poly(Lactide-co-Glycolide)- Nanodiamond Scaffolds for Bone Cell Growth.

There are relatively few nanotechnologies that can produce nanocomposite scaffolds for cell growth. Electrospinning has emerged as the foremost method of producing nanofibrous biomimetic scaffolds for tissue engineering applications. In this study diamond nanoparticles were integrated into a polymer solution to develop a nanocomposite scaffold containing poly(lactide-co-glycolide) (PLGA) loaded with diamond nanoparticles. To investigate the effect of adding diamond nanoparticles to PLGA scaffolds, primary human mesenchymal stem cells (hMSCs) were seeded on the scaffolds. The cytocompatibility results showed that addition of diamond nanoparticles did not impinge upon cell proliferation, nor was there a cytotoxic cellular response after 9 days in culture. Scanning electron microscopy, transmission electron microscopy, atomic force microscopy and confocal microscopy enabled qualitative characterization of the fibres and revealed cell morphology and number. Furthermore, surface roughness was measured to evaluate diamond nanoparticle modifications, and no significant difference was found between the diamond nanocomposite and pure polymer scaffolds. On the other hand, bright spots on phase images performed by atomic force microscopy suggested a higher hardness at certain points on fibers of the PLGA-nanodiamond composites, which was supported by nanoindentation measurements. This study shows that PLGA nanofibers can be reinforced with nanodiamond without adversely affecting cell behaviour, and thus it sets the foundation for future application of these scaffolds in bone tissue engineering.

Nanostructured diamond layers enhance the infrared spectroscopy of biomolecules.

We report on the fabrication and practical use of high-quality optical elements based on Au mirrors coated with diamond layers with flat, nanocolumnar, and nanoporous morphologies. Diamond layers (100 nm thickness) are grown at low temperatures (about 300 °C) from a methane, carbon dioxide, and hydrogen gas mixture by a pulsed microwave plasma system with linear antennas. Using grazing angle reflectance (GAR) Fourier transform infrared spectroscopy with p-polarized light, we compare the IR spectra of fetal bovine serum proteins adsorbed on diamond layers with oxidized (hydrophilic) surfaces. We show that the nanoporous diamond layers provide IR spectra with a signal gain of about 600% and a significantly improved sensitivity limit. This is attributed to its enhanced internal surface area. The improved sensitivity enabled us to distinguish weak infrared absorption peaks of <10-nm-thick protein layers and thereby to analyze the intimate diamond-molecule interface.

Utilizing Constant Energy Difference between sp-Peak and C 1s Core Level in Photoelectron Spectra for Unambiguous Identification and Quantification of Diamond Phase in Nanodiamonds.

The modification of nanodiamond (ND) surfaces has significant applications in sensing devices, drug delivery, bioimaging, and tissue engineering. Precise control of the diamond phase composition and bond configurations during ND processing and surface finalization is crucial. In this study, we conducted a comparative analysis of the graphitization process in various types of hydrogenated NDs, considering differences in ND size and quality. We prepared three types of hydrogenated NDs: high-pressure high-temperature NDs (HPHT ND-H; 0-30 nm), conventional detonation nanodiamonds (DND-H; ~5 nm), and size- and nitrogen-reduced hydrogenated nanodiamonds (snr-DND-H; 2-3 nm). The samples underwent annealing in an ultra-high vacuum and sputtering by Ar cluster ion beam (ArCIB). Samples were investigated by in situ X-ray photoelectron spectroscopy (XPS), in situ ultraviolet photoelectron spectroscopy (UPS), and Raman spectroscopy (RS). Our investigation revealed that the graphitization temperature of NDs ranges from 600 °C to 700 °C and depends on the size and crystallinity of the NDs. Smaller DND particles with a high density of defects exhibit a lower graphitization temperature. We revealed a constant energy difference of 271.3 eV between the sp-peak in the valence band spectra (at around 13.7 eV) and the sp3 component in the C 1s core level spectra (at 285.0 eV). The identification of this energy difference helps in calibrating charge shifts and serves the unambiguous identification of the sp3 bond contribution in the C 1s spectra obtained from ND samples. Results were validated through reference measurements on hydrogenated single crystal C(111)-H and highly-ordered pyrolytic graphite (HOPG).

Novel, fast, and reliable electrochemical dsDNA biosensor based on O-terminated pristine nanocrystalline boron-doped diamond electrode for DNA interaction studies.

We present a novel application of a nanocrystalline boron-doped diamond electrode (B-NCDE) for the construction of an electrochemical DNA biosensor based on double-stranded DNA (dsDNA) for various bioanalytical applications. Surface characterization of the transducer surface (prior and after the fabrication of negatively charged O-terminated surface - O-B-NCDE) was performed by scanning electron microscopy (SEM), Raman spectroscopy, and linear sweep voltammetry (LSV) that was further used for the voltammetric determination, scan rate dependence investigation, and repeatability examination of dsDNA electrochemical oxidation at the O-B-NCDE. The fabrication of a dsDNA/O-B-NCDE biosensor via electrostatic adsorption of dsDNA involved a thorough optimization process of deposition potential (Edep), deposition time (tdep), and optimal saturation concentration (cg(satur)) with optimal values of 0.3 V, 3 min, and 10 mg/mL. The bioanalytical applicability of the fabricated dsDNA/O-B-NCDE biosensor was verified by examining the nature of the interaction between dsDNA and five selected DNA intercalators - namely thioridazine hydrochloride (TR), trimipramine maleate (TRIM), levomepromazine maleate (LEV), imipramine hydrochloride (IMI), and prochlorperazine maleate (PER) - where intercalation was proven for all of the five tested compounds. Moreover, the proposed novel bioanalytical test offers the possibility to selectively distinguish between the phenothiazine representatives (TR, LEV, and PER) and representatives of tricyclic antidepressants group (TRIM and IMI).

What Are the Key Factors for the Detection of Peptides Using Mass Spectrometry on Boron-Doped Diamond Surfaces?

We investigated the use of boron-doped diamond (BDD) with different surface morphologies for the enhanced detection of nine different peptides by matrix-assisted laser desorption/ionisation mass spectrometry (MALDI-MS). For the first time, we compared three different nanostructured BDD film morphologies (Continuous, Nanograss, and Nanotips) with differently terminated surfaces (-H, -O, and -F) to commercially available Ground Steel plates. All these surfaces were evaluated for their effectiveness in detecting the nine different peptides by MALDI-MS. Our results demonstrated that certain nanostructured BDD surfaces exhibited superior performance for the detection of especially hydrophobic peptides (e.g., bradykinin 1-7, substance P, and the renin substrate), with a limit of detection of down to 2.3 pM. Further investigation showed that hydrophobic peptides (e.g., bradykinin 1-7, substance P, and the renin substrate) were effectively detected on hydrogen-terminated BDD surfaces. On the other hand, the highly acidic negatively charged peptide adrenocorticotropic hormone fragment 18-39 was effectively identified on oxygen-/fluorine-terminated BDD surfaces. Furthermore, BDD surfaces reduced sodium adduct contamination significantly.

Design and investigation of properties of nanocrystalline diamond optical planar waveguides.

Diamond thin films have remarkable properties comparable with natural diamond. Because of these properties it is a very promising material for many various applications (sensors, heat sink, optical mirrors, chemical and radiation wear, cold cathodes, tissue engineering, etc.) In this paper we report about design, deposition and measurement of properties of optical planar waveguides fabricated from nanocrystalline diamond thin films. The nanocrystalline diamond planar waveguide was deposited by microwave plasma enhanced chemical vapor deposition and the structure of the deposited film was studied by scanning electron microscopy and Raman spectroscopy. The design of the presented planar waveguides was realized on the bases of modified dispersion equation and was schemed for 632.8 nm, 964 nm, 1 310 nm and 1 550 nm wavelengths. Waveguiding properties were examined by prism coupling technique and it was found that the diamond based planar optical element guided one fundamental mode for all measured wavelengths. Values of the refractive indices of our NCD thin film measured at various wavelengths were almost the same as those of natural diamond.

Controlling electrostatic charging of nanocrystalline diamond at nanoscale.

Constant electrical current in the range of -1 to -200 pA is applied by an atomic force microscope (AFM) in contact mode regime to induce and study local electrostatic charging of oxygen-terminated nanocrystalline diamond (NCD) thin films. The NCD films are deposited on silicon in 70 nm thickness and with 60% relative sp(2) phase content. Charging current is monitored by conductive AFM. Electric potential contrast induced by the current is evaluated by Kelvin force microscopy (KFM). KFM shows well-defined, homogeneous, and reproducible microscopic patterns that are not influenced by inherent tip-surface junction fluctuations during the charging process. The charged patterns are persistent for at least 72 h due to charge trapping inside the NCD film. The current-induced charging also clearly reveals field-induced detrapping at current amplitudes >-50 pA and tip instability at >-150 pA, both of which limit the achievable potential contrast. In addition, we show that the field also determines the range of electronic states that can trap the charge. We present a model and discuss implications for control of the nanoscale charging process.

Nanoparticles assume electrical potential according to substrate, size, and surface termination.

Electrical potential of nanoparticles under relevant environment is substantial for their applications in electronics as well as sensors and biology. Here, we use Kelvin force microscopy to characterize electrical properties of semiconducting diamond nanoparticles (DNPs) of 5-10 nm nominal size and metallic gold nanoparticles (20 and 40 nm) on Si and Au substrates under ambient conditions. The DNPs are deposited on Si and Au substrates from dispersions with well-defined zeta-potential. We show that the nanoparticle potential depends on its size and that the only reliable potential characteristic is a linear fit of this dependence within a 5-50 nm range. Systematically different potentials of hydrogenated, oxidized, and graphitized DNPs are resolved using this methodology. The differences are within 50 mV, that is much lower than on monocrystalline diamond. Furthermore, all of the nanoparticles assume their potential within -60 mV according to the Au and Si substrate, thus gaining up to 0.4 V difference. This effect is attributed to DNP charging by charge transfer and/or polarization. This is confirmed by secondary electron emission. Such effects are general with broad implications for nanoparticles applications.

Development of the Pseudomonas syringae pv. morsprunorum Biofilm Monitored in Real Time Using Attenuated Total Reflection Fourier Transform Infrared Measurements in a Flow Cell Chamber.

Biofilms of sessile Pseudomonas syringae cells formed on top of plant host's leaves or fruits allow surviving harsh environmental conditions (desiccation) and improve their resistance to antibacterial treatments of crops. A better understanding of these biofilms can help minimize their effect on harvests. In the present study, infrared attenuated total reflection spectroscopy coupled with optical and confocal laser scanning microscopy has been applied for the first time to analyze Pseudomonas syringae pathovar morsprunorum biofilm development in real time. The biofilm development was observed within a spectral window 4000-800 cm-1 under constant flow conditions for 72 h. The kinetics of representative integrated band areas (nucleic acids with polysaccharides at 1141-1006 cm-1, amino acid side chains with free fatty acids at 1420-1380 cm-1, proteins at 1580-1490 cm-1, and lipids with proteins at 2935-2915 cm-1) were analyzed with regard to the observed biofilm structure and the following P. syringae biofilm developmental stages were attributed: The inoculation phase, washing of weakly attached bacteria closely followed by recolonization of the vacated surface, the restructuration phase, and finally the maturation phase.

Light emission dynamics of silicon vacancy centers in a polycrystalline diamond thin film.

Diamond thin films can be, at a relatively low-cost, prepared with a high-density of light-emitting negatively charged silicon vacancy (SiV) centers, which opens up the possibility of their application in photonics or sensing. The films are composed of diamond grains with both the SiV centers and sp2-carbon phase, the ratio of these two components being dependent on the preparation conditions. The grain surface and the sp2-related defects might act as traps for the carriers excited within the SiV centers, consequently decreasing their internal photoluminescence (PL) quantum efficiency. Here, we show that in a 300 nm thick polycrystalline diamond film on a quartz substrate, the SiV centers in the diamond grains possess similar temperature-dependent (13-300 K) PL decay dynamics as the SiV centers in monocrystalline diamond, which suggests that most of the SiV centers are not directly interconnected with the defects of the diamond thin films, i.e. that the carriers excited within the centers do not leak into the defects of the film. The activation energy ΔE = 54 meV and the attempt frequency α = 2.6 were extracted from the measured data. These values corresponded very well with the published values for SiV centers in monocrystalline diamond. We support this claim by measuring the transient absorption via a pump and probe technique, where we separated the nanosecond recombination dynamics of carriers in SiV centers from the picosecond decay dynamics of polycrystalline diamond defects. Our results show that PL emission properties of SiV centers in polycrystalline diamond thin films prepared via chemical vapor deposition are very similar to those in monocrystalline diamond thereby opening the door for their application in diamond photonics and sensing.

Improved Gas Sensing Capabilities of MoS2/Diamond Heterostructures at Room Temperature.

Molybdenum disulfide (MoS2) and nanocrystalline diamond (NCD) have attracted considerable attention due to their unique electronic structure and extraordinary physical and chemical properties in many applications, including sensor devices in gas sensing applications. Combining MoS2 and H-terminated NCD (H-NCD) in a heterostructure design can improve the sensing performance due to their mutual advantages. In this study, the synthesis of MoS2 and H-NCD thin films using appropriate physical/chemical deposition methods and their analysis in terms of gas sensing properties in their individual and combined forms are demonstrated. The sensitivity and time domain characteristics of the sensors were investigated for three gases: oxidizing NO2, reducing NH3, and neutral synthetic air. It was observed that the MoS2/H-NCD heterostructure-based gas sensor exhibits improved sensitivity to oxidizing NO2 (0.157%·ppm-1) and reducing NH3 (0.188%·ppm-1) gases compared to pure active materials (pure MoS2 achieves responses of 0.018%·ppm-1 for NO2 and -0.0072%·ppm-1 for NH3, respectively, and almost no response for pure H-NCD at room temperature). Different gas interaction model pathways were developed to describe the current flow mechanism through the sensing area with/without the heterostructure. The gas interaction model independently considers the influence of each material (chemisorption for MoS2 and surface doping mechanism for H-NCD) as well as the current flow mechanism through the formed P-N heterojunction.

Absolute energy levels in nanodiamonds of different origins and surface chemistries.

Nanodiamonds (NDs) are versatile, broadly available nanomaterials with a set of features highly attractive for applications from biology over energy harvesting to quantum technologies. Via synthesis and surface chemistry, NDs can be tuned from the sub-micron to the single-digit size, from conductive to insulating, from hydrophobic to hydrophilic, and from positively to negatively charged surface by simple annealing processes. Such ND diversity makes it difficult to understand and take advantage of their electronic properties. Here we present a systematic correlated study of structural and electronic properties of NDs with different origins and surface terminations. The absolute energy level diagrams are obtained by the combination of optical (UV-vis) and photoelectron (UPS) spectroscopies, Kelvin probe measurements, and energy-resolved electrochemical impedance spectroscopy (ER-EIS). The energy levels and density of states in the bandgap of NDs are correlated with the surface chemistry and structure characterized by FTIR and Raman spectroscopy. We show profound differences in energy band shifts (by up to 3 eV), Fermi level position (from p-type to n-type), electron affinity (from +0.5 eV to -2.2 eV), optical band gap (5.2 eV to 5.5 eV), band gap states (tail or mid-gap), and electrical conductivity depending on the high-pressure, high-temperature and detonation origin of NDs as well as on the effects of NDs' oxidation, hydrogenation, sp2/sp3 carbon phases and surface adsorbates. These data are fundamental for understanding and designing NDs' optoelectrochemical functional mechanisms in diverse application areas.

Thiol-yne reaction on boron-doped diamond electrodes: application for the electrochemical detection of DNA-DNA hybridization events.

Boron-doped diamond (BDD) interfaces were chemically functionalized through the catalyst free thiol-yne reaction. Different thiolated precursors (e.g., perfluorodecanethiol, 6-(ferrocenyl)-hexanethiol, DNA) were successfully "clicked" to alkynyl-terminated BDD by irradiating the interface at 365 nm for 30 min. Thiolated oligonucleotide strands were immobilized using the optimized reaction conditions, and the surface concentration was tuned to obtain a surface coverage of 3.1 × 10(12) molecules cm(-2). Electrochemical impedance spectroscopy (EIS) was employed to follow the kinetics of hybridization and dehybridization events. The sensitivity of the oligonucleotide modified BDD interface was assayed, and a detection limit of 1 nM was obtained.

Nanomolar hydrogen peroxide detection using horseradish peroxidase covalently linked to undoped nanocrystalline diamond surfaces.

In this article, we report on the low-level detection of hydrogen peroxide, a key player in the redox signaling pathway and a toxic product in the cellular system, using a colorimetric solution assay. Amine-terminated undoped nanocrystalline diamond thin films were grown on glass using a linear-antenna microwave plasma CVD process. The diamond surface consists mainly of -NH(2) termination. The aminated diamond surface was decorated with horseradish peroxidase (HRP) enzyme using carbodiimide coupling chemistry. The success of the HRP immobilization was confirmed by X-ray photoelectron spectroscopy (XPS). The enzymatic activity of immobilized HRP was determined with a colorimetric test based on the HRP-catalyzed oxidation of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sufonic acid (ABTS) in the presence of hydrogen peroxide. The surface coverage of active HRP was estimated to be Γ = 7.3 × 10(13) molecules cm(-2). The use of the functionalized diamond surface as an optical sensor for the detection of hydrogen peroxide with a detection limit of 35 nM was demonstrated.