Ing. Štěpán Potocký, Ph.D.

Doped diamond has found a commercial use for achieving durable and reproducible electrical measurements in atomic force microscopy (AFM). Yet so far it has not been used on self-sensing AFM probes due to thermally and mechanically sensitive integrated detection circuits. Herein, conventional microwave plasma chemical vapor deposition (CVD) is employed while taking advantage of thermal conductivity along the silicon AFM cantilever probe for growing high-quality B-doped nanocrystalline diamond film on the probe apex that is selectively seeded by dip coating in nanodiamond solution. By investigating various CVD process parameters, it is shown that the detection circuit remains functional up to 400 °C for 2 h deposition or up to 8 h at 300 °C. Scanning electron microscopy and Raman spectroscopy corroborate quality of the diamond coating and doping. The self-sensing probes are successfully tested in conductive AFM (C-AFM) regime and surface spreading resistance regime, showing linear response in current–voltage spectroscopy and capability of conductivity mapping on metals and semiconductor devices. In the results, prospects for stable C-AFM measurements when conventional optical detection is not suitable, such as on photosensitive materials or in probe-electron microscopy, are opened.

This study looked at the fabrication and electrochemical performance of PANI/Diamond hybrid electrodes. Here, two PANI types were synthesized using a novel acid-assisted polymerization technique carried out at room temperature. Contrary to other synthetization methods, a pronounced benzenoid units ratio was confirmed by Raman measurements. Low (3k ppm) and high (10k ppm) boron-doped diamond films were grown by microwave plasma CVD process. Electrochemical investigations of fabricated PANI/diamond electrodes confirmed that both the PANI morphology (porous nanofibrils vs. densely packed structure) and the B doping level have a crucial impact on their performance in terms of electrochemical window width and oxidative/redox peak characteristics.

Among the family of 2D Transition Metal Dichalcogenides, single-layer MoS2, has attracted significant attention for potential applications in optoelectronic devices. Here, we conducted a set of experiments to optimize the growth conditions to synthesize a few layers of MoS2 on Si/SiO2 substrate using MoO3 as a solid source by thermal Chemical Vapour Deposition (CVD) at vacuum or atmospheric pressure. We also investigated the film quality of the grown MoS2 flakes for different substrate orientations (vertical vs. horizontal) and the substrate temperatures (850 °C vs. 950 °C). Moreover, we performed calculations of film thickness from the peak energy difference between the in-plane (E2g) and out-of-plane (A1g) phonon modes reflected in the Raman spectra. We show that employing a MoO3 solid source instead of a Mo ultrathin layer (standardly used in CVD) provides an easy and cost-effective approach, having a broader technological window for the CVD process and to synthesize good enough few-layer MoS2 flakes for opto-electronic applications.

Optically active color centers in diamonds have been intensively studied due to their potential in photonics, energy harvesting, biosensing, and quantum computing. Silicon vacancy (SiV) center offers an advantage of suitable emission wavelength and narrow zero-phonon line at room temperature. Measurement of surface potential and photovoltage can provide better understanding of the physics and control of SiV light emission, such as charge states and charging effects. Herein, optoelectronic properties of nanocrystalline diamond films with SiV centers at different layer thicknesses (10-200 nm, controlled by the growth time) under ambient conditions are studied. Time-dependent measurements are performed in the light-dark-light cycle. Positive photovoltage arises on samples with SiV layer thicknesses below 55 nm on both H- and O-terminated surfaces. Above 55 nm the photovoltage switches to negative. This layer thickness thus represents a halfway boundary between surface-controllable and bulk SiV centers dominant contribution. A band diagram scheme explaining the photovoltage switching mechanism is provided. Nanocrystalline diamond films with silicon vacancy (SiV) centers exhibit a change in work function and surface photovoltage including a switch of polarity with the increasing growth thicknesses (5-175 nm) for both H- and O-terminated surfaces. The SiV layer thickness of 32 or 20 nm, respectively, represents a halfway boundary between surface-controllable SiV centers and dominant bulk SiV contribution.image (c) 2023 WILEY-VCH GmbH

The effect of atmospheric and low-pressure plasma modification on polypropylene (PP) microfibers was examined. Mechanical changes on the microfiber surfaces were observed using scanning electron microscopy (SEM). Next, wettability was measured using the packedcell method. The fibers were applied into a cement matrix containing micro-milled recycled concrete. Test specimens were made and then the dynamic modulus of elasticity was continuously measured. After 28 days were made in the test specimens central notches to a depth of 14 mm. Finally, bending tests were performed. From the results, the fracture energy of the composite material was calculated. It was proven that low-pressure plasma modification as well as atmospheric plasma modification increases the wettability of PP fibers with water. Furthermore, it was found that samples containing plasma-modified microfibers have a higher fracture energy compared to the same samples with fibers without plasma modification. Conversely, plasma modification had no effect on the dynamic modulus of elasticity.

The present study investigates the effect of an oxidized nanocrystalline diamond (O-NCD) coating functionalized with bone morphogenetic protein 7 (BMP-7) on human osteoblast maturation and extracellular matrix mineralization in vitro and on new bone formation in vivo. The chemical structure and the morphology of the NCD coating and the adhesion, thickness and morphology of the superimposed BMP-7 layer have also been assessed. The material analysis proved synthesis of a conformal diamond coating with a fine nanostructured morphology on the Ti6Al4V samples. The homogeneous nanostructured layer of BMP-7 on the NCD coating created by a physisorption method was confirmed by AFM. The osteogenic maturation of hFOB 1.19 cells in vitro was only slightly enhanced by the O-NCD coating alone without any increase in the mineralization of the matrix. Functionalization of the coating with BMP-7 resulted in more pronounced cell osteogenic maturation and increased extracellular matrix mineralization. Similar results were obtained in vivo from micro-CT and histological analyses of rabbit distal femurs with screws implanted for 4 or 12 weeks. While the O-NCD-coated implants alone promoted greater thickness of newly-formed bone in direct contact with the implant surface than the bare material, a further increase was induced by BMP-7. It can be therefore concluded that O-NCD coating functionalized with BMP-7 is a promising surface modification of metallic bone implants in order to improve their osseointegration.

Two microwave (2.45 GHz) plasma systems with ellipsoidal and multimode clamshell cavity for diamond synthesis by chemical vapor deposition were compared. Both systems are capable of high pressure (up to 20 kPa) operation and high growth rates (several µm/h). It was shown that by using the multimode operation of the clamshell cavity system and specially design sample holder, it is possible to sustain a plasma in a cavity and reach good enough process reproducibility and diamond film quality over 4-inch substrates.

The easy and fast detection of drug content and concentration levels is demanded in biological research as well as in clinical practice. Here we study on microscopic level how nanodiamonds and gold nanoparticles interact with a multifunctional drug molecule directly on a biosensor surface. The sensors are made of interdigitated Au electrodes coated by 5 nm hydrogenated or oxidized nanodiamonds and further combined with Au colloidal nanoparticles (size 20 nm) providing nanoscale composite (spacing 100 nm). Atomic force microscopy is employed to measure local tip-surface adhesion forces and surface topography. AFM adhesion maps show that the drug binds to all types of nanoparticles and the adhesion is also significantly influenced by the substrates on which the nanoparticles are deposited. Role of local AFM tip interaction with nanostructured surface is also discussed.

Presented work focuses on chemical and physical properties of plasma modified polymeric macro-fibers. Polyethylene terephthalate (PET) and polypropylene (PP) fibers having approx. 300 µm in diameter were modified using cold oxygen plasma in order to achieve their surface changes needed for durable bond and adhesion with cement matrixes. A duration of plasma modification differed between 5 to 480 seconds, where an effect of the treatment was examined. Fiber surfaces chemical changes were researched via wettability measurement with demineralized water (the measurement was repeated immediately and after 1, 7 and 30 days to find out the changes stability). Physical changes were studied by means of weight balance (determination of weight loss) and tensile strength tests. It was found that wettability was enhanced significantly – up to two times, while mechanical properties of treated fibers decreased only slightly.