In this work we study preparation methods of tin nanoparticles in different reaction conditions, then we study influence of reaction temperature, surfactant type and amount on size and melting point of nanoparticles. Prepared nanoparticles are characterized by dynamic light scattering, transmission and scanning electron microscopy, differential scanning calorimetry and powder X-ray diffraction. Results of individual analyses are mutually compared and the process of preparing the nanoparticles exhibiting the highest uniformity, depression of melting point and the lowest size evaluated. The smallest particles were synthetised by the reduction method at temperature of 120 °C and their diameter was 10 nm. Melting point depression of this sample is reported, sample melted at 225 °C.
The flow behaviour of soft materials – hydrogels prepared by unique combination of biopolymer (sodium hyaluronate) and oppositely charged surface active agent (Carbethopendecinium bromide – Septonex) was studied by steady-state viscosity measurements. The influence of different parameters such as way of preparation, concentration of both components, and molecular weight of sodium hyaluronate on the flow properties was determined and compared. It was proved that the way of preparation has not effect on the final flow properties in contrast with the influence molecular weight and concertation of surfactant. The independence of dynamic viscosity on the way of preparation seems to be very important finding especially with regards to potential utilization of these phase-prepared hydrogels in medical applications.
Hydration is one of the crucial properties for understanding the behavior of any chemical material. Due to the presence of hydrogen bonds together with hydrophobic and other types of intermolecular interactions water sorption influences the properties of the substances. Moreover, the importance of the absorbability is even higher when speaking about biopolymers which are somehow connected with hydrogels applications, potentially used in wound healing. The aim of this work was to study water sorption ability of selected biopolymers (dextran, chitosan, hyaluronan) and humic acid using two thermoanalytical techniques: differential scanning calorimetry (DSC) and perfusion microcalorimetry. These methods which are based on different measurement principle can give a complex overview on the sorption behavior of the sample. The results show expected differences of both temperature of melting and heat of hydration which are caused by many factors such as presence of side functional groups on the biopolymer chain, solubility of the studied biopolymers in water or molecular weight when speaking about hyaluronan.
The characterisation of glidants is important for process control and the design of its processing conditions or handling devices in pharmaceutical industry. Frequently used, fine glidants as Aerosil®, Cab-O-Sil® and magnesium stearate are specific for characterisation of dynamic behavior. These are complex powder systems, in particular because they contain varying amounts of air that can radically change (influence) their rheology or flow properties. The aim of this work is to describe the dynamic behavior of the above mentioned sliding substances. Avalanching regions were determined using a dynamic bulk angle measurement method in a rotating transparent drum. Aeration regions and compressibility factors were measured by the FT4 Freeman Technology. The first results showed the change of avalanching regions of all the glidants with the rotation speed of the measuring drum. Tested glidants were included into the aeration regions and their dynamic behavior was described.
In this work cerium oxide nanoparticles have been prepared via simple co-preciptation method and exposed to ionizing radiation of each plasma and gamma rays.
A change in the ceria structure and a significant increase in the relative fraction (%) of Ce3+ has been found when the prepared particles exposed to plasma for not less than 60 min. or a plasma discharge current more than 30(mA). Gamma radiation has not the same effect on the relative fraction (%) of Ce3+ and it had reduced the ceria crystallinity.
Skutterudites are complex alloys with promising thermoelectric properties and they have already achieved fair efficiency for the conversion of heat to electricity. Researchers are trying to further enhance the figure of merit by various ways, e.g. mechanical alloying and/or nanostructuring. Mechanical properties of the resulting materials are important as well. In a recent paper by G. Rogl et al. (J. Alloys Compd. 695 (2017) 682–696), various additives to skutterudites were thoroughly tested and some of them proved to increase the thermal-electrical conversion efficiency in a wide temperature range.
In this work we studied the microstructure and mechanical properties of two selected materials, namely (i) an industrial p-type DDyFe3CoSb12 skutterudite mixed with 1 wt.% Ta0.8Zr0.2B and (ii) an industrial n-type (MM,Sm)yCo4Sb12 skutterudite mixed with 1 wt.% Ta0.8Zr0.2B. The component powders were first sieved and blended manually, then they were ball-milled and finally uniaxially hot pressed. Thin lamellas were prepared from the compacted material using a focused ion beam in a scanning electron microscope. Analytical transmission electron microscopy was used on lamellas to study details of microstructure, precipitation and elements distribution. Quasistatic and dynamic nanoindentation tests were carried out on a grid by means of a Hysitron TI950 triboindenter in the range of applied loads from 10 to 1000 µN. The modulus mapping capability was applied to obtain quantitative maps of the storage and loss stiffness and the storage and loss modulus and the results were correlated with microstructure.
ACKNOWLEDGEMENTS: The research was supported by the Czech Science Foundation (Project 17-12844S).
A heterojunction formed between a single n-type ZnO nanorod and p-type GaN template was successfully prepared by low cost chemical bath deposition technique. Periodic circular patterns were fabricated by focused ion beam etching through poly(methyl methacrylate) mask to control the size, position, and periodicity of the ZnO nanorods. A possible growth mechanism is introduced to explain the growth process of the nanorods. Optical and electrical properties of the heterojunctions were investigated by low temperature photoluminescence spectroscopy and by the measurement of current-voltage (I-V) characteristics. The I-V characteristics were measured by directly contacting single ZnO nanorods with the conductive atomic force microscopy tip. The diode-like rectifying behavior was observed with a turn-on voltage of 2.3 V and the reverse breakdown voltage was 5 V.
Influence of graphite addition to the ball-milling charge composed of Mg splinters and Mg17Al12 particles upon the hydrogen sorption was investigated at sorption temperature 623 K. Measurements were carried out by Sieverts method. Graphite facilitates the ball-milling: It prevents re-agglomeration of crushed particles into large secondary particles. It also suppresses sticking the milled material to the balls and walls of the milling jar. It was found that an increase of carbon concentration up to a certain limit cL lying between 14 and 23 wt. % C, carbon increases both the absorption and the desorption rates and hydrogen storage capacity. Above cL, carbon causes a considerable decrease in HS capacity, which spoils the application potential of Mg@Mg17Al12/C. Crystallite size of the material under study, obtained by XRD, is in the order of tens of nm.
Metal nanoparticles have special catalytic properties in comparison with massive metal. This feature is actively studied in various catalytic reactions: hydrogenation, oxidation, carbon-carbon bond formation, electrochemical reactions, electron transfer reactions et al. The purpose of our work was to study the features of catalytic reduction of hexacyanoferrate(III) ions with hydrogen in presence of Pd nanoparticles. Nanoparticles were obtained by the photochemical method in the presence of polyacrylate as a stabilizer. Xenon lamp was used as a light source. The effect of stirring, acidity of solution, hydrogen pressure and amount of catalyst on reduction process was studied. It was found that change of pH (in range from 3 to 11) and stirring of solution did not significantly affect rate constant of reduction process. These results demonstrate that internal or external diffusion is not the limiting stage. In addition, it has been shown that the reaction rate depends linearly on the hydrogen pressure and the amount of nanoparticles added. It was explained by first-order of hydrogen in reaction and by proportionality of rate from active surface of catalyst. It was also noted that pre-saturation of Pd-hydrosol with hydrogen leads to a significant acceleration of reaction. This may be due to the fact that on the surface nanoparticles occur a reversible dissociative adsorption of hydrogen with formation of H–PdNP bond. It has been proposed that dissociative adsorption of hydrogen on metal surface is nonactivational process. This assumption is confirmed by the absence of an effect of temperature on rate of the reaction.
The work was funded by RFBR according to the research project № 15-03-02068-a.
Hydrogels represent nowadays important material either from scientific point of view, as well as from the view of possible applications. This contribution is focused on the study of transport properties of reactive hydrogels based on biopolymer agarose. This polysaccharide can at certain conditions form hydrogel matrix. This non-reactive hydrogel can represent ideal carrier matrix for additional substances (e.g. polyelectrolytes). Incorporation of specific modifiers allows tuning the final properties (e.g. reactivity) of these hydrogel in respect to the needs of their possible applications. In present contribution, we have focused on modification of reactivity of agarose hydrogels through incorporation of sodium alginate, hyaluronic acid, carrageenan, sodium polystyrene sulfonate, dextran and chitosan. In experimental works, Rhodamine 6G was selected as a probe, whose transport was observed and quantified. Moreover, the results from diffusion experiments were correlated with several basic structural characteristics of individual studied hydrogels (internal pH value, content of water, wettability…) as well as their mechanical properties (mainly from rheological characterization). Two basic approaches in the study of transport properties of individual hydrogels were used in experimental part of this work (both based on diffusion processes). The first method was based on the simple macroscopic study on diffusion of Rhodamine 6G from solution into cuvettes containing individual agarose-based reactive hydrogels (diffusion model of constant source). The second used technique was based on Rhodamine 6G self-diffusion measurement (method of fluorescence correlation spectroscopy). Both used methods showed to be valuable in deeper description and characterization of interactions and mobility of selected probe in reactive agarose-based hydrogel matrices. The results of our work are indicating that the transport and barrier properties of individual agarose-based reactive hydrogels are significantly affected by charge of the polyelectrolyte, which has been incorporated in agarose hydrogels, as well as by its charge density.
In this work, four different flowability powder tests – angle of repose measuring, flow from hopper simulation, classical tube method and evaluation of flow functions using FT4 powder rheometer - were compared. The TiO2 powders with different content of nanoparticle were used for these comparisons. These powders were characterized by basic mechanical-physical parameters such as particle size distribution, density, moisture etc. The first flowability method (angle of repose measuring) uses stand with vibration feeder of fine powder material. Flow simulation method is based on powder flow from the hopper. Both mentioned test stands were created in Bulk Solids Centre Czech Republic. Third classical tube method is based on free pouring of powder on the pad. These three methods named above are evaluated on a static angle of repose. The fourth test is based on the calculation of the flow function as ratio major principal stress and unconfined yield strength measured using FT4 powder rheometer. Flowability methods of TiO2 powder have been compared. The advantages and disadvantages of the individual methods and the areas of their use have been identified.
In general, polymer materials are qualified as thermal insulators because they have low thermal conductivity below 1 W/mK (amorphous polyethylene ~ 0.4 W/mK). On the other hand, experiments and mathematical simulations show that the crystallization process of polymer structure has significant effect on the thermal transport processes. The value of thermal conductivity increases when the degree of crystallinity increases. In case of polyethylene crystal, the value of simulated thermal conductivity was several times higher than for the amorphous morphology. These facts predict the wide possibility of using especially for heat conductive components (computer chips, heat exchange fins).
This contribution represents the molecular dynamic (MD) simulation to predict the thermal conductivity of polyethylene nanocrystal. We focused on the different dimension of nanocrystal structure. Moreover, the process of MD simulation (especially the heat flux autocorrelation function vs time) was in detail mathematically analyzed using Fourier transformation.
With a wide potential window in aqueous solutions, low background current and high chemical stability, electrically conductive diamond is one optimal material choice as working electrode for electrochemical applications. As a wide band gap semiconductor, conductivity of diamond can be controlled through incorporation of electrically active impurities, usually using boron atom as acceptor atoms. For boron concentration above c.a. 2·1020 atoms per cm-3, that corresponds to a B/C ratio of c.a. 2000 ppm B/C in the gas phase during diamond layer synthesis, the conductivity of diamond switch from semiconducting in the freeze out regime with resistivity above 10 .cm to metallic type conductivity and resistivity of 1-10 m.cm and hence faster electron transfer. However, the potential window of diamond electrodes decreases with increasing boron concentration. This study is motivated by the objective to produce diamond electrode with both wide potential window and high electrical conductivity using a bilayer structure.
In this work, we present the fabrication and characterization of bilayer doped diamond electrodes. The bilayer with different doping concentration has been fabricated by plasma enhanced chemical vapor deposition in two steps: namely an inner thick layer of highly boron doped diamond ([B] > 2·1020 B atoms per cm-3) and an outer thin layer with a lower boron concentration. All samples were grown on electrically conductive silicon substrate using an ASTeX 5010 deposition system. Effect of the deposition time, i.e. the thickness and doping concentration of outer thin diamond layer on electrochemical properties of the diamond electrodes have been studied by cyclic voltammetry and impedance spectroscopy.
Acknowledgements: This work was supported by the Czech Science Foundation (contract No. 13-31783S), the Czech Ministry of Industry and Trade (contract No. FV – TRIO FV10312), the Technology Agency of the Czech Republic (contract No. TH02030874), and the J.E. Purkyně fellowship awarded to V. Mortet by Academy of Sciences of the Czech Republic.
Metal nanostructures with small number of atoms (atomic or molecular clusters) form a special group of nanosized objects. Due to discrete nature of the electronic structure their optical properties are closer to that of atoms and molecules, in particular, in very small clusters luminescence may be observe in the visible range.
In this work metal clusters were created by the physical vapor deposition of metals in vacuum. In order to prevent the formation of large metal nanoparticles the dielectric material was deposited simultaneously with metal. The samples produced in this way consist of the dielectric matrix with the metal particles included into it. Changing the ratio of the deposition rates of metal and dielectric materials one can vary the clusters size, and hence their optical properties.
Three peaks in absorption spectra of silver clusters in SiO2 at 297 nm, 329 nm and 401 nm and two peaks in luminescence spectra at about 500 nm and 650 nm were observed. This can be explained by strong dispersion of the particle size, i.e. by the presence in the film of the two kinds of particles with different optical properties. The redshift of the absorption and luminescence bands is observed at thermal annealing or by increasing of the silver content.
The samples containing gold and copper exhibit broad absorption bands in the visible range, which is related to a larger number of transitions in this spectral region in clusters of these metals than in silver clusters.
Titanium materials are widely used in aerospace industry, in chemical industry and in total joint replacements because of their low density, high strength, good corrosion resistance, high toughness, and good biocompatibility. However, titanium materials have poor wear resistance and high friction. Implantation of nitrogen into titanium and its alloys significantly improves their surface properties such as hardness, friction, wear and corrosion resistance. Titanium nitride nanolayer was prepared by nitrogen ion implantation on titanium. The evolution of phase composition after annealing was investigated. The samples were analysed by X-ray diffraction, X-ray photoelectron spectroscopy and nanoindentation. The aim of this work is to examine the effect of the nitrogen concentration on phase representation in the modified surface area and the structural mechanisms of hardening after annealing.
In this work, TiO2 nanotubes were grown by anodic oxidation on Ti6Al4V substrates in organic solution containing ethylene glycol and Ammonium fluoride at several applied potentials varied between 20 and 70V followed by thermal annealing at 450°C for 2h. Different nanotubes diameters and lengths were obtained as revealed by scanning electron microscope. X-ray diffraction exhibits amorphous structure for all as-anodized nanotubes, it transforms to anatase after the annealing. Corrosion behavior was evaluated in artificial saliva at 37 °C with neutral pH of 7.4 by using open circuit potential, cyclic polarization and electrochemical impedance spectroscopy techniques.
Herein, we represent an innovative precursor for one-pot green synthesis of highly stabilized silver nanoparticles (AgNPs) at high concentration up to 2000 ppm via using of cellulose nanocrystals (CNC). For the first time, CNC without any surface modification in the presence of alkali is acting as both reducing and stabilizing agent in preparation of AgNPs. Extraction of CNC from cotton is carried out as per to acid hydrolysis (H2SO4 60% w/w) technique. The as prepared CNC are subjected to several washing treatments with deionized water to remove salts as well as the excess acid. The pH of never dried CNC slurry solution was then adjusted via using aqueous solution of NaOH (0.1M). During this, the temperature is raising up to 60 0C. At this point, equivalent amounts of silver nitrate are added separately to CNC solutions in order to prepare AgNPs with concentrations of 500 ppm, 1000 ppm and 2000 ppm. Thorough assessment of AgNPs formation, structural and morph-logical characteristics of AgNPs are investigated by making use of UV–vis spectroscopy, transmission electron microscopy (TEM), dynamic light scattering (DLS), zeta potential, FT-IR and X-ray diffraction(XRD) analysis. Research outputs signify (a) CNC has great tendency toward reducing and stabilizing the as formed AgNPs even at high concentration up to 2000ppm, b) average Sizes and size distribution of AgNPs are less than 50 nm with sphere-like morphology even at higher concentration and c) FTIR, XRD and AFM affirm the chemical structure, crystalline phase and spherical shape of AgNPs. Green synthesis of the well stabilized AgNPs at high concentration using CNC-alkali treatment is industrial feasible for quick handling as well as easily applicable in many sectors related to antibacterial purposes e.g. textile, paints, etc.
The deposition of organosilicone thin films from mixture of hexamethyldisiloxane (HMDSO) and oxygen by using capacitively coupled R.F. glow discharges under dusty plasma conditions was investigated. High resolution topography and mechanical property maps of the prepared films were acquired by using atomic force microscopy techniques. The chemical bond and composition of the deposited films were analyzed by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The mechanical properties of the films were studied using quasistatic as well as dynamic nanoindentation tests and their surface free energies were evaluated by means of contact angle measuring technique using several testing liquids exhibiting various surface tensions. The thermal stability of the films was studied using thermal desorption spectroscopy. Neural network modelling was used to study the effect of plasma parameters on the hardness of ppHMDSO films.
ACKNOWLEDGEMENTS: This research has been supported by the project CZ.1.05/2.1.00/03.0086 funded by European Development Fund and project LO1411 (NPU I) funded by Ministry of Education Youth and Sports of Czech Republic and The Czech Science Foundation (Project 15-17875S).
The main aim of the present work was to study the dependence of mechanical properties of Ti/Ni multilayer thin films on the thicknesses of constituent Ti and Ni layers. The multilayer thin films were made by depositing Ti and Ni layers alternately on single crystalline silicon substrates using magnetron sputtering method. A DC (direct current) magnetron sputtering without sample heating was used with Ti and Ni targets, power on each target was 350 W, the deposition pressure was 0.3 Pa, the growth rate was 0.75 nm/s and 1.52 nm/s for Ti and Ni layers, respectively. Thicknesses of Ti and Ni layers varied from 5 nm to 100 nm. The structure of the multilayer films was studied using XRD (X-ray diffraction technique), (SEM) scanning electron microscopy with focused ion beam technique and (TEM) transmission electron microscopy. Mechanical properties obtained from nanoindentation experiments will be discussed in relation to microstructural observations.
The research has been supported by the Czech Science Foundation (Project 15-17875S
Nitrogen incorporated organosilicone films were prepared by means of plasma enhanced chemical vapor deposition using capacitively coupled RF glow discharges in mixtures of hexamethyldisiloxane and nitrogen. The flow rate of nitrogen was 2 sccm and the flow rate of hexamethyldisiloxane was 0.4 sccm. The total pressure of deposition was 20.7 Pa and the power supply of CCP was 50 W. The deposition with these parameters was run 30 minutes.
The environmental stability of the deposited films was studied using confocal microscopy, spectroscopic ellipsometry and FTIR (Fourier Transform Infrared Spectroscopy). The structure changes of the films were monitored using X-ray photoelectron spectroscopy (XPS). The humidity induced structure changes resulted in substantial change of mechanical properties of the studied films. The mechanical properties were studied using nanoindentation techniques.
ACKNOWLEDGEMENTS: The research has been supported by the Czech Science Foundation (Project 15-17875S).
The paper deals with the study of layers applied by magnetic sputtering on samples for electron microscopy. It describes the effect of different layers deposition parameters on the change of the surface morphology of the samples. The reference substrate is Si wafer, layer materials are the most used gold and platinum. Scanning Electron Microscopy and Atomic Force Microscopy are used for qualitative and quantitative evaluation.
TiCN layers are widely used for their high hardness and abrasion resistance. Their structure, chemical composition and mechanical properties are affected by deposition parameters. In the present work, there were studied four TiCN layer deposited on Al substrate under variating C2H2/N2 process gas flow ratio.
Materials with ferroelectric, piezoelectric or pyroelectric properties are present nowadays, in bulk form, in many applications or devices: non-volatile memories, sensors, actuators etc. The present tendency is to explore the ferroelectric or multiferroic properties at nanometric scale, to use these materials in nanotechnology. Many of the applications are based on PZT, the material with the best ferroelectric properties: remnant polarization, coercive field or Curie temperature [1], but its toxicity rises serious environmental problems, leading to limitations of using lead-based materials in electronic devices in European Union [2]. The most promising lead-free material seems to be (Bi0.5Na0.5)TiO3 (BNT) because it shows strong ferroelectric properties with a significantly remnant polarization of 38 μC/cm2 and a Curie temperature of 320°C [3]. It was reported that the BNT ceramics have better ferroelectric/piezoelectric properties if doped with BaTiO3 (BT) because the BNT-BT system has a morphotropic phase boundary (MPB) between rhombohedral (R) and tetragonal (T) ferroelectric phases [4].
In present work we study epitaxial 0.92BNT-0.08BT thin film on SrTiO3 (STO) substrates with SrRuO3 (SRO) bottom electrode down to atomic level using high-resolution analytical Transmission Electron Microscopy techniques. Nanoscale ferroelectricity in epitaxial thin films is strongly affected by interfaces due to bonding of interfacial atoms in the ferroelectric to adjacent atoms in the electrode [5], so it is necessary to analyse the atomic arrangement at thin film-electrode interface. Also, the extended defects can occur during the layer deposition or layer relaxation, influencing the electrical properties. Using Electron Energy Loss Spectroscopy-Spectrum Imaging we obtained elemental maps from interfaces and extended defects.
REFERENCES: [1] Lucian Pintilie, Corneliu Ghica, Cristian Mihail Teodorescu, Ioana Pintilie, Cristina Chirila, Iuliana Pasuk, Lucian Trupina, Luminita Hrib, Andra Georgia Boni, Nicoleta Georgiana Apostol, Laura Elena Abramiuc, Raluca Negrea, Mariana Stefan & Daniela Ghica, Scientific Reports 5, Article number: 14974 (2015).; [2] J. Rödel, W. Jo, K. Seifert, E.M. Anton, T. Granzow, D. Damjanovic, J. Am. Ceram. Soc. 92 (2009) 1153.; [3] Ferroelectrics - Material Aspects, Editor Mickaël Lallart, chapter: Lead-Free Ferroelectric Ceramics with Perovskite Structure, Rigoberto López-Juárez, Federico González and María-Elena Villafuerte Castrejón, ISBN 978-953-307-332-3, DOI: 10.5772/702.; [4] Ferroelectrics - Physical Effects, Editor Mickaël Lallart, chapter: Morphotropic Phase Boundary in Ferroelectric Materials, ISBN 978-953-307-453-5, 2011.; [5] Chun-Gang Duan, Renat F. Sabirianov, Wai-Ning Mei, Sitaram S. Jaswal, Evgeny Y. Tsymbal, Nano Letters 6, 2006, 483-487.
The main problem to the use of aluminum oxide as a coating material is its brittleness due to low toughness and low bending strength. The combination of high hardness, strength, fire resistance inherent in aluminum oxide, with plasticity and thermal conductivity, characteristic for titanium causes interest in coatings obtained on the basis of a composite of Al2O3 and Ti. A five series of nanostructure coatings from composite the titanium and aluminum oxide powders have been prepared on a corrosion-resistant steel substrate by a new multi-chamber gas-dynamic accelerator (MCDS) with different powder composites Al2O3/xTi (x = 3 %, 13%, 25%, 40%, 50%). It was found that the addition of Ti powder to the Al2O3 powder leads to changes in the structural-phase composition and the hardness of the coatings obtained, the namely contributes to the formation of the intermetallic phase of AlTi3, which causes an increase in hardness (by 1.2 ... 1.3 times) of such coatings. To improve the structural characteristics it was conducted annealing of the obtained coatings. It was found that coatings from a composite of Al2O3/Ti powders contain twice as many particles of phase separations of nanoscale type as compared with Al2O3 coatings.
Nitrogen implantation into titanium and its alloys significantly improves their surface hardness, sliding behaviour, wear and corrosion resistance. A thin surface nanolayer originating, e.g., from air exposure or from condensation of oil vapours modifies the ion energy distribution and causes a difference in the ion range. The effect of the thickness of the contaminant carbon layer on the nitrogen distribution was investigated. Titanium samples with a carbon nanolayer were implanted with nitrogen ions. An almost Gaussian experimental concentration profile was observed. The maximum of nitrogen concentration moves into the specimen with increasing thickness of the nanolayer. The experimental findings are in agreement with the theoretical calculations. These results can be useful for optimizing surface modifications of titanium materials by ion implantation.
Nanofiltration has made tremendous progress during the past decades due to its excellent removal of contaminant from waste water. These membranes have gained interest recently for the treatment of inorganic effluent to reduce the amount of waste water produced and in addition improve the quality of effluent. The basic principle of nanofiltation separation is by sieving effect and electrical charge of a membrane. This can be clearly understood by determining the structural (pore radius and membrane porosity ratio) and electrical properties of a membrane. A polyamide thin composite NF membrane (AFC 30) was used to characterize the structural and electrical parameters. The structural values were estimated with permeation experiments of aqueous solution of neutral solutes in conjunction with steric hindrance model (SHP). The fixed charge density on the membrane surface was determined using sodium chloride experiments at different concentrations. The data from sodium chloride experiment were used to evaluate the effective charge density (ФX) by using the Spiegler-Kedem model together with the charge model called Teorell-Meyer Sievers (TMS). It was found that the membrane charge depends solely on the salt concentration in the solution, which is because of ion adsorption on the membrane surface.
Polytetrafluoroethylene (PTFE) which is also called as “TEFLON” is a synthetic fluoropolymer of tetrafluoroethylene that has wide applications due to its differentiating properties. In this study, different PTFE dispersions for preparation of polytetrafluoroethylene mesoporous active membranes doped by basalt and carbon particles which were created in high voltage electrostatic field has been studied. The adjusting of process parameters of common electrospinning system (Nanospider) for preparation of membranes with tunable porosity created by nanofibrous assembly (electrospinning) and interconnected particles (electrospraying) has also been investigated. The nanoparticles based on milled basalt and carbonwas used for activation and achieving of special effects. Superhydrophobic Polytetrafluoroethylene (PTFE) nanofibrous membranes with different surface structures were obtained by controlling operating parameters in the electrospinning process. The diameters and microstructure of the PTFE nanofibrous membrane were characterized by scanning electron microscopy. The contact angles on the nanomembranes were evaluated by static micro-drop observation, and a modified Yang equation was applied to analyze the contact angles. The superhydrophobic PTFE nanofibrous membranes were also tested for thermal properties. As a result of this study, optimized PTFE blend solutions were identified. The results also revealed that the specific surface area was the key factor affecting the contact angles. The thermal properties revealed that thermal conductivity was higher and thermal resistance was lower for carbon and basalt doped membranes.
The 1H Nuclear Magnetic Resonance Relaxometry has been used for studying properties of various porous materials. T1 and T2 relaxation times in such systems are influenced by the molecule confinement and T1/T2 ratio can reflect an interaction strength between an adsorbate molecules and an adsorbent surface. In this paper 1D relaxation times distributions and 2D T1-T2 maps from NMR measurements at magnetic field of 0.05 T are shown. Two mesoporous silica materials: MCM-41 and SBA-15 are studied at different water saturation states. Signals from hydroxyl groups, water confined in pores and bulk water are distinguished. Higher T1/T2 is measured for SBA-15 than for MCM-41 and the increase of T1/T2 ratio for the samples with lower amount of water is observed. Relaxation parameters for other porous systems such as exemplary geological samples in different saturation states and for biological samples are also compared.
ACKNOWLEDGEMENTS: The work was financed by the National Centre of Research and Development, contract No. PBS2/A2/16/2013 and contract No. STRATEGMED2/265761/10/NCBR/2015.
The crystallinity of fibres prepared by electrospinning shows lower level in comparison with samples processed by common technologies such as moulding or film casting. Thus, the attempts to improve the structure of electrospun fibres in order to increase physical and mechanical properties of nonwoven webs are obvious. Post-process thermal treatment is one of the possibilities of the crystallinity enhancement that can be easily included to the finishing operation of final products. For the experiment we used polyethylene oxide (PEO) representing electrospun-friendly material and two solvents - methanol and water, both ensuring good electrospinnability. It is demonstrated that a choice of polymer solvents plays a significant role in fibre diameter and their capabilities to resist applied heat. However, in all cases the enhancement of crystallinity is detected at the short time of thermal exposure.
The stability of plasma polymer matrix with functional metal fraction was investigated by UV-VIS and SEM techniques. Compared are properties of plasma polymer – silver nanocomposites where PTFE and/or nylon serve as plasma polymer matrix. Plasma polymer was deposited by rf magnetron sputtering of polymer bulks of PTFE and nylon 6.6, respectively. Silver was immersed into the matrix by two different ways: (i) in form of nanoislands, formed by diffusive coagulation of deposited Ag atoms onto the plasma polymer, and (ii) by directly deposited Ag particles of size about of 11 nm grown in gas aggregation cluster source. The nanocomposite sandwich structure was achieved by mutually alternating deposition of plasma polymer films and metal nanoparticles. Stability of prepared nanocomposite in ambient atmosphere, in water and under thermal load is investigated and compared for different sandwich structures and different plasma polymer matrixes (PTFE vs. nylon 6.6.). UV-VIS absorbance spectra and their spectral shifts are measured over the time to verify the nanocomposite stability. SEM imaging is employed as complementary method to observe a material response on external input. All measurements are carried out with the view to tailor preparation of stable nanocomposites for SERS and bio-medical applications.
ACKNOWLEDGEMENTS: This work is supported by GAČR 16-14024S.
The use of synthetic polymers in packaging applications has been limited as a result of ecological problems. Using rice husk to produce eco-friendly and biodegradable food packaging materials is a partially solution to reduce the used of conventional nonbiodegradable materials made from petroleum. Rice husk (RH) are low cost, cellulosic-based materials and the chemical composition is the main factor that imparts a high possible application of this class of materials in biopolymer composites production. Biocomposites based on rice husk (RH) and low-density polyethylene (LDPE) were prepared by laboratory Brabender mixer. The influence of rice husk and high content of 10, 20, 30, 40 and 50 wt % RH on the composite properties was studied in this work. Results confirmed that the incorporation of the RH into the LDPE and increase of the content of the RH slightly increased the crystallinity which means that RH act as a nucleating agent. The initial degradation temperature of the neat LDPE is shifted to lower temperature by addition of RH which means that the thermal stability of the LDPE decreased by the addition of RH. The tensile strength and elongation at breake decreases of LDPE were found to decrease by the addition of RH and with an increase in the RH content while the water vapor transmission rade increase. When the biocomposites were immersed in distilled water for 60 days duration. The higher RH contenr composite absorbed more water compared to the others. This is due to the presence of cellulose in the RH structure that tends to absorb moisture from the surrounding environment.
The hardmetal Cr3C2-25NiCr (180-220 μm thick) coatings have been produced on a steel substrate by a new multi-chamber gas-dynamic accelerator. The Cr3C2-25NiCr powder (POLEMA JSC, Russia) (35-140 μm) was used as the starting material to deposit a dense layer. A detailed analysis of the features of the coatings structure on all the levels of the structure (from grain to dislocation) (phase composition, distribution of the disperse phase, grain nature, subgrains and dislocation structures) was conducted. The structural-phase state of the coatings was characterized using SEM, TEM, and XRD techniques. It was established that phase composition of Cr3C2-NiCr powder under the influence of high temperatures and the atmosphere of detonation products changes with the formation of a complex heterogeneous structural-phase state in the coatings. A layered structure of the regions of carbide particles and matrix metal was found in the immediate vicinity of the "carbide-matrix" boundary with the precipitates in the matrix of dispersed secondary carbides. It was shown that the nanocomposite Cr3C2 -NiCr coatings are characterized by the presence of nanodispersed ceramic compounds. Lamellae in the coatings consisted of nanocrystalline grains, separated by interlayers of the amorphous phase and oxide crystalline grains.
A large amount of microelectronic devices components are based on the unique properties of gallium nitride. Our purpose was to find the most effective and simple way for gallium nitride (GaN) nanoparticles synthesis. GaN nanoparticles were prepared by a gallium oxide powder – aluminium nanopowder (NP) mixture combustion process under air atmosphere and with the use of calorimetric bomb (under nitrogen atmosphere, P = 0.3 MPa). The aluminium nanopowder was obtained by electrical explosion process of aluminium wire in argon atmosphere. The GaN nanoparticles synthesis is based on the high – temperature chemical binding of nitrogen in the presence of oxygen impurities, that leads to the formation of stable crystal nitrides phases: AlN, GaN. The combustion process includes two stages, the first one (low – temperature) caused an absorption hydrogen burning (800 – 1200 °С), the second stage (high – temperature) leads to nitrides formation (2000 – 2400 °С). It was reported about Nb, Ta, B, C, Al and other elements nitrides formation during heat explosion of aluminium nanopowder – Nb, Ta, B, C, Al oxides mixture under air atmosphere.
ACKNOWLEDGEMENTS: The research is supported by The Ministry of Education and Science of the Russian Federation, Project No 11.1928.2017 (government order “Science/Project part”).
Nowadays researchers are strongly focusing on the growth of different metal oxides nanostructures (nanowires, nanorods etc.) for remarkable physical/chemical properties due to their large surface to volume ratio [1]. ZnO and NiO, due to their wide band gap, show important features such as low electronic noise, ability to maintain high breakdown voltages and ability to run at high power with many applications including gas sensors, electrochemical capacitors etc. [2-5]. The fabrication of composite nanostructures based on a combination of p-type and n-type semiconducting metal oxides offers an important path to connect different physical/chemical properties of individual components into a single system, ZnO/NiO in our case [6].
NiO nanowires (NWs) were grown on gold (Au) catalyzed alumina substrates using vapor-liquid-solid (VLS) mechanism and then the ZnO was directly added on the NiO NWs surface using vapor-solid (VS) mechanism. For TEM characterization the nanowires were removed from the surface of Al substrate and put on a copper grid.
This work presents the structural and compositional microanalysis down to atomic resolution of the as-prepared ZnO/NiO system and after 15 and 30 minutes exposure to NO gas using complex analytical electron microscopy techniques. Conventional TEM images show the morphology of the ZnO/NiO systems and HRTEM images reveal the crystallographic relation between ZnO and NiO. Using Electron Energy Loss Spectroscopy combined with Scanning TEM images we evidenced the Zn, Ni and O distribution in the analyzed samples.
ACKNOWLEDGEMENTS: This work is the result of an international collaboration in the frame of the CERIC-ERIC consortium.
REFERENCES: [1] Nanowires and Nanobelts: Materials, Properties and Devices. Volume 1: Metal and Semiconductor Nanowires, Volume 1, Springer Science & Business Media, 2013.; [2] P. Mitra and H. S. Maiti, Sensors and Actuators B: Chemical, 2004, 97, 49–58.; [3] C. Tian, Q. Zhang, A. Wu, M. Jiang, Z. Liang, B. Jiang and H. Fu, Chemical communications (Cambridge, England), 2012, 48, 2858–60.; [4] C. G. Granqvist, Handbook of Inorganic Electrochromic Materials, Elsevier, 1995.; [5] N. Kaur, E. Comini, D. Zappa, N. Poli and G. Sberveglieri, Nanotechnology, 2016, 27, 205701.; [6] H. Ohta, M. Hirano, K. Nakahara, H. Maruta, T. Tanabe, M. Kamiya, T. Kamiya and H. Hosono, Applied Physics Letters, 2003, 83, 1029.
This contribution deals with the atomic force microscopy (AFM) measurement of nanosphere size standards that were dispersed on flat glass surface. AFM measurement proceeded either on monodispersed particles or on mix of particles with two different diameters that were usually dense-packed on the surface. Obtained AFM data were evaluated in Gwyddion open source software (http://gwyddion.net/). Different ways of data processing for determination of particle diameters are presented together with advanteges and drawbacks of these approaches focusing on measurement uncertainty. Numerical modelling was performed for better understanding of data evaluation. Firstly, simulated virtual images by tip-sample convolution were created, secondly, various algorithms were used to get the information on particle diameters from these images.
Zinc oxide (ZnO) is a well known semiconductor material with a wide direct band gap (Eg~3.3 eV at 300 K). ZnO nanostructures are a subject of interest in many research groups mainly for their potential in electronic and photonic applications.
We introduce our approach to the preparation and characterization of periodic vertical arrays of ZnO nanorods and microrods. The arrays are prepared by hydrothermal growth through a poly(methyl methacrylate) (PMMA) mask on a ZnO seed layer substrate as well as on a gallium nitride (GaN) substrate. The PMMA is patterned by electron beam lithography (EBL) or with focused ion beams (FIB). The arrays are characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), and photoluminescence spectroscopy (PL). The properties and the growth mechanisms of the ZnO nanorods are related to (i) the patterning technique, (ii) the seed layer properties, and (iii) the parameters of hydrothermal growth.
Wollaston wire thermal probes were used for nanoscale and microscale thermal analysis since the first Scanning Thermal Microscopy applications on materials, probing temperature and thermal conductivity with very high spatial resolution. Their benefits were namely robustness, long life and high span of thermal conductivities they can analyse.
They become less used in last few years, when manufacturers stopped their production and replaced them by microfabricated probes, that can reach higher spatial resolution. However, the old design of Wollaston wire probes has still some benefits and there are still many experiments on which it would be helpful.
We present a revised manufacturing steps for Wollaston wire probes fabrication in a small manufacturing workshop environment. Results of temperature and local thermal conductivity measurements on various nanostructured and microstructured samples will be shown and the main uncertainty budget components related to probes sensing accuracy will be discussed.
Macroscopic magnetic field measurements are traceable to magnetic resonance quantum standards and traceability chains to industry are well established. However, important European high tech industries such as the magnetic sensor, information technology, and bio-medical industry, as well as R&D labs require traceable and reliable measurements of magnetic fields and flux densities on the micro- or nanometer scale e.g. for quantitative analysis and quality control. However such calibrations are presently unavailable. We are developing metrology tools and methods suitable for traceable measurements of the local stray field distribution of permanent magnets and magnetic encoder scales with spatial resolution from 50 micrometers down to 500 nanometers to underpin ultra-precise magnetic position sensing; to evaluate different local stray field measurement techniques with respect to traceability and uncertainties; and to establish traceability of local stray field measurements to macroscopic SI standards and to evaluate their uncertainties.
Nowadays preparation of structures on flexible substrates is highly demanded because of using this patterns in field of flexible electronics. This contribution deals with photolitographic procces for preparation of structures on flexible substrates. The method of photolitography enables to create designed patterns in various material (e.g. metals as conductive layers) on various substrates (silicon wafers, foils, etc.). First the designed pattern is exposed through the mask by UV light into polymer resist, then the pattern is transfered into metal layer by wet etching through the developed windows in resist. In this paper several patterns are prepared through the positive resist PMMA by photolitography into various metal layer (Cu, Al) on flexible substrates.
During the last decade, interest in polymer/clay composites increased, mostly due to their very good physical, chemical, and mechanical properties which can be significantly enhanced in various ways compared to conventional polymers. One of the most studied conducting polymers is polyaniline (PANI) which has unique electrical and optical properties, and, in addition, its interaction with clay structure leads to improvement of resulting electrical conductivity. In this study, the clay mineral montmorillonite (MMT) was used. Raman spectroscopy is nondestructive technique and coupled with an optical microscope has a potential for determination of the chemical composition and possible inhomogeneity of the sample. Moreover, Raman spectroscopy is very sensitive to changes in the structure of polymers in terms of its protonation state. Aim of the study was the characterization of PANI/MMT nanocomposites prepared in three different forms (powders, layers, and tablets) by Raman microspectroscopy. In addition, the prepared samples were afterwards calcined to the 1300 °C, where the transformation of PANI to the few-layer graphene was observed. Above that, Raman microspectroscopy was used to creation of the Raman spectral maps which reveal the distribution of the formed few-layer graphene.
ACKNOWLEDGEMENTS: This work was supported by the Ministry of Education, Youth and Sports of the Czech Republic [grant numbers SP2017/65, LQ1602 (NPU II – IT4Innovations excellence in science)].
Surface Enhanced Raman Spectroscopy (SERS) is a method to amplify inherently weak Raman signals by increasing apparent Raman scattering cross-section for molecules of the analyte by the local amplification of the electromagnetic field in the close vicinity of metal nanostructures caused by the excitation of localized surface plasmon resonances.
The most straightforward approach to suppress intensity of background signal in order to minimize the spectral interference appears to develop SERS-active substrates based on materials of the simplest possible chemical composition with preference of inorganic materials. It is challenging with respect to the standard materials and routes used to obtain nanostructured SERS-active substrates. Most of nanotemplates are based on polymers and, thus, the inherent contamination affects negatively limits of detection, or identification of analyte.
We present the SERS-active substrates based on nanostructured pure-metallic layers deposited directly on Si wafer, where Si works also as internal standard. These substrates were prepared by magnetron sputtering of gold under specific conditions to obtain an optimal gold granularity. We develop the concept originating in our laboratory: the crumpled (polycrystalic) thin gold layer - the rather disordered material with extraordinarily high concentration of apparently homogeneously distributed “hotspots” in structures with sub-nanometer separation of ultrathin polycrystalline lamellas tightly stacked or arranged into V-grooves. Importantly, the crumpled thin gold layer is not contaminated by organic compounds and is more resistant to photodamage by laser beam.
To the second class of plasmonically important nanostructures belong inverse opals. Heat resistant, innorganic nanostructures of chemically simple composition are SiO2 inverse opals prepared by infiltration of direct polystyrene opals with TEOS (tetraethylorthosilicate) and following removal of polystyrene by its depolymerization under high temperature (annealing at 450°C).
The third class of heat resistant SERS active substrates is represented by materials based on metallized monolayers of SiO2 microspheres. Preparation of micro- and nanosphere monolayers involve the steps of particle hydrophobization, self-assembly on water surface, deposition onto Si wafer followed by annealing in the air and metallization. This class of substrates reveals very stable and low background signal in SERS.
ACKNOWLEDGEMENTS: This work was supported by the Czech Science Foundation P205/13/20110S project.
In the past years nanoindentation has become an indispensable tool to study hardness, elastic modulus and other related mechanical properties at the nanoscale, such as microstructured devices, nanocomposites and thin films. The metrological treatment of the method, however, has not been covered in such detail. Usually the uncertainties are estimated to be in the range of percent but a detailed uncertainty budget is seldom presented.
Not all parameters and options of the data processing can be given a priori, but often must be made by the user based on experience. Depending on the data, this may result in very different outcomes. In this contribution we point out the impact of some of these choices on the total uncertainty budget and summarize recommendations how to avoid the most significant problems. An open-source software for the analysis of nanoidentation data including uncertainties treatment (NIGET) is presented.
Diamond can become highly conductive due to impurity impact ionization and avalanche effects when sufficiently doped with boron and exposed to high electric field. Knowledge of those effects is important for the fabrication of potential novel high power electronic devices. High currents and voltages make characterization of impurity impact ionization uneasy and require pulsed characterization measurement methods to limit thermal effects. In this work, we first present the synthesis of epitaxial boron doped diamond layers by Plasma Enhanced Chemical Vapour Deposition and their microfabrication process and then we study their electrical properties in high electric field. Second, we describe the home-made Transmission Line Pulse current-voltage (I-V) characterization setup based on a Blumlein pulse generator. Finally, quasi-static I-V characteristic has been measured showing impurity impact ionization and avalanche effect at high electric field.
The theoretical models are suggested which describe specific plastic deformation mechanisms in ultrafine-grained materials with nanotwinned structure (nanotwinned materials). In the framework of the suggested models, micromechanism of nanotwin widening and micromechanism of combined action of lattice dislocation slip and twin boundary migration in nanotwinned materials are considered. In addition, the detwinning mechanism in ultrafine-grained nanotwinned metals through stress-driven migration of incoherent boundaries of nanoscale twins is examined. It is demonstrated that detwinning of ultrathin twins can occur at very low stresses, while detwinning of thicker twins requires high applied stresses.The theoretical results and their comparison with corresponding experimental data in the exemplary case of nanotwinned cooper (Cu) are discussed.
Acknowledgements. The work was supported by the Russian Fund of Basic Research (grant 16-32-60110) and Ministry of Education and Science of Russian Federation (grant MD-9152.2016.1).
Gas aggregation cluster sources (GAS) gained significant scientific interest in the last decades and were successfully used for the preparation of plasma polymer nanoparticles (NPs). However, deep insight into the processes of the NP formation and growth is still lacking. In this work, we applied a method of light scattering for in situ detection of the formation of organosilicon NPs within a GAS.
Plasma polymerization of hexamethyldisiloxane in its 10 % mixture with Ar was used to synthesize the NPs. The total pressure of 45 Pa and the RF discharge power in a range of 20 – 80 W were used. The GAS was constructed to allow passing of a laser beam (446 nm) across the beam of NPs at 2 cm from the orifice and acquiring the scattered light either by an optical emission spectrometer or by a CCD camera. Although for 20 W power constant intensity of the scattered light was obtained, cycling instabilities were detected for higher power. Both amplitude and period of such fluctuations increased with the discharge power raising from 40 to 80 W. Cycling repelling of NPs and formation of plasma voids are suggested as possible mechanisms for the observed phenomena.
ACKNOWLEDGEMENT: The authors would like to acknowledge the contribution of the COST Action CA15107 (MultiComp) and support by the grant LTC17062 from the Ministry of Education, Youth and Sports of the Czech Republic. M. V. and D.N. acknowledge the support from the student grant SVV 260 444/2017 of Charles University.
Metal nanoalloys display many unusual properties, such as depression of melting point, plasmon resonance, catalytic activity, and phase separation. Nanoalloys can be prepared by a variety of synthetic approaches, but highly advantageous is the solvothermal synthesis, specifically in oleylamine (OA). Silver and nickel are mutually immiscible, but in the nanoform are in a very close contact and thus create atypical structures.
AgNi nanoparticles were prepared by injection of a small volume of OA solution of AgNO3 and Ni(acac)2 in different molar ratios to a mixture of OA and octadecene at 230 °C. After 10 min, the reaction mixture was cooled down to room temperature and acetone was added to precipitate nanoparticles. The suspension was centrifuged and the precipitate was washed twice by a mixture of hexane and acetone. Finally, the precipitate was dispersed in hexane and characterized.
Dynamic light scattering (DLS), transmission electron microscopy (TEM), elemental analyses (ICP OES), small-angle X-ray scattering (SAXS) and high-resolution TEM/STEM with EELS and EDS analyses were performed for determination of chemical composition, average size, size distribution and shape of the prepared nanoparticles. Elemental mapping of individual nanoparticles showed a core/shell structure in which the silver nucleus was covered by a nickel layer. HT-XRD together with VSM and SEM/EDX analysis prove the phase separation and reveal magnetic properties.
ACKNOWLEDGEMENTS: This research has been financially supported by the Ministry of Education, Youth and Sports of the Czech Republic under the project CEITEC 2020 (LQ1601).
Poly(ε – caprolactone) bioabsorbable nano and micro fibers have been fabricated by uncommon needle less and collector less alternating current electrospinning. In this frame work, the focus of present work has been optimizing of the AC spinnability of poly (ε – caprolactone) using less harmful formic acid as a solvent, demonstrated the feasibility of fabricating the defects and beads free nano and microfibers for vascular scaffolds. Present work clearly describes the effect of solution concentration (5%, 10%, and 15%), viscosity, fiber morphology and applied AC potential (20 to 38Kv) during electrospinning have been investigated.
Nanoindentation experiments with micro- and nanoscale structures, like pillars, can provide novel insight into mechanical phenomena like size dependent hardening, that are important in design of NEMS/MEMS systems and in development of novel nanocomposite materials. In order to simulate small scale indentation process, one can not use continuum based tools, like Finite Element Method, but needs to incorporate the atomistic nature of the material, either based on some dislocations based models or using fully atomistic description, like classical molecular dynamics. A big disadvantage of this approach is that the accuracy is fully governed by accuracy of the used interatomic potential, which might be better or worse, but in all the cases is only an approximation of the whole problem. Moreover, for many systems there are no analytical potentials available so far, or the present potentials are not complex enough to represent the physical properties like bond angles or bond weakening. Based on ab-initio techniques, that would be itself too numerically demanding for the complete solution, we can generate data for creation of empirical potentials. Even in this case we however need to give some analytical formulation to the potential, which itself is already a constraint. We present our results in using neural network based potentials for nanoindentation experiments calculations. Here, the DFT data are used to train a neural network to give the particle energies or forces and the neural network is then used in the classical molecular dynamics. The efficiency of such solution will be demonstrated on simple systems where we can easily compare the analytical approach, neural networks and DFT results. Then, a model used for nanoindentation experiments simulation will be presented.
Nanoindentation instruments are commonly used to study hardness, elastic modulus and other related mechanical properties at the nanoscale. They are a popular tool for the study and design of thin film systems, nanocomposites and other nanostructured materials and devices. Metrological issues such as uncertainty analysis and traceability are often treated only briefly. In many cases only the statistical variability is taken into account although the uncertainties of the method itself are in the range of percent.
It is well known that the correct determination of the area function of the indenter plays a crucial role. However, this can also be a difficult step in the traceability measurement chain.
The probably simplest and most widely used calibration procedure is by measuring a well-characterized reference sample. We analyze the uncertainties related to this procedure and compare the impact of different sources of uncertainties, such as quality of reference sample, data acquisition, data processing and choice of fitting procedure. The uncertainty analysis is performed using NIGET, an open-source software for general nanoindentation data processing.
Energy and charge of the particle play the principal role in spatial distribution of ionizations, and thus in the DNA damage. We evaluated impact of different track structure of various low-energy ions with similar LET on DNA double-strand breaks (DSBs) induction and repair using high-resolution immunofluorescence confocal microscopy of γH2AX/53BP1 foci to study at microscale the extent, complexity, spatio temporal behavior and repair of DSBs induced by γ-rays, boron and neon ions of different characteristics.
Our results showed that repair kinetics is highly dependent on the radiation quality – the higher the LET, the slower γH2AX/53BP1 foci elimination was observed, indicating production of complex DSBs at nanoscale level that are more difficult to repair. Comparison of radiations with similar LET values (~135 keV/μm) - 47 MeV/n neon and 8 MeV/n boron ions revealed formation of significantly more persistent foci after neon in comparison to boron ions irradiation. More detailed studies of foci morphology were done on cells irradiated at low angle of 10° to maximize the resolution power of foci separation by confocal microscopy. The analysis of γH2AX/53BP1 foci size, circularity and complexity correlated with the above described results and further characterized induced DNA damage. Foci clusters induced by ions were bigger, greater irregularity and sere composed of more closely spaced (sub)foci within one γH2AX/53BP1 foci cluster. Depending on the physical parameters of radiation (energy, charge of particle), the different nanodosimetric patterns of energy dissipation along the particle track affected the extent and arrangement of DNA damage and thus also its reparability.