The influence of lower temperature on size and polydispersity of silver nanoparticles prepared by reduction of the silver diammonia complex cation by sodium borohydride was studied. The preparation was carried out in ethylene glycol and ethanol in the presence of stabilizing agents. Silver nanoparticles were characterized by UV-Vis spectroscopy, dynamic light scattering (DLS) and transmission electron microscopy (TEM). The best results were achieved in ethanol. The smallest nanoparticles were prepared at the reaction temperature of -5 °C (3.4±1.7 nm). With decreasing temperature, the average size of silver nanoparticles increased up to 7.2±2.9 nm (-25 °C).
Nanoparticles and nanoisland films of noble metals have demonstrated their applicability in sensing, surface-enhanced Raman scattering, nonlinear optics. Self-assembly of such structures is considered as a promising approach for their fabrication due to its simplicity. One of the usable techniques is a self-assembled growth of silver nanoislands on the surface of ion-exchanged glass during silver out-diffusion in the case of annealing of glasses in a reducing atmosphere. Here we report the studies of silver nanoparticles (NPs) grown by silver-to sodium ion exchange in a commercial soda-lime glass slides and thermal processing in a hydrogen atmosphere.
To get the information about the NPs composition/crystalline structure we mechanically removed a single nanoparticle with the dielectric tip and then studied it with x-rays diffractometry. All studied NPs exhibited scattering pattern coinciding with the one of crystalline silver, which confirmed the fact that silver remains in the metallic state and possible reactions with oxygen / sulfur dioxide in the air are weak or completely absent. Together with the observed 6-months stability of the optical response, this allows to suppose that the out-diffused self-assembled nanoislands are somehow passivated.
To study the shapes of NPs, we washed them out from the substrate with water, centrifuged the resulting suspension, and subjected the precipitate to TEM. This experiment confirmed our previous estimations that the NPs shapes are truncated spheres/ellipsoids. Measured size distributions of the NPs showed that the majority of them are of 2-7 nanometers in size, however, few of them are as big as 150 nm.
Application potential of colloidal particles and nanoparticles is related to their size, shape and other physical and chemical properties. Those properties can be influenced by various ways of synthesis, while the presence of reducing agent and modifiers (polymers, surfactants) are the most vital ones. [1] One of the strongest reducing agents is tin with the redox couple Sn(II)/Sn(IV) and standard potential -0,384 V. [2] This redox system allows to change redox potential just by addition of hydrogen peroxide to the tin (II) solution, which causes its partial oxidation to tin (IV) and changes the ratio between its oxidized and reduced form. Those changes effect redox potential (which is measured by potentiometer) and influence the tailored synthesis of silver nanoparticles. Antibacterial activity of prepared nanoparticles, with an average size between 3 to 50 nm, was tested against pathogenic and resistant bacteria, while the smallest nanoparticles have shown high antibacterial activity with minimal inhibition concentration (MIC) in units of mg/L.
ACKNOWLEDGEMENTS: The authors are grateful for the support by the projects LO1305 of the Ministry of Education, Youth and Sports of the Czech Republic and inert grant UP Olomouc project IGA_PrF_2017_025.
REFERENCES: [1] Muhammad Akram Raza, Zakia Kanwal, Anum Rauf, Anjum Nasim Sabri, Saira Riaz and Shahzad Naseem: Size- and Shape-Dependent Antibacterial Studies of Silver Nanoparticles Synthesized by Wet Chemical Routes. Nanomaterials 2016, 6, 74; [2] Gajda, Tamás, Pál Sipos a Heinz Gamsjager. The standard electrode potential of the Sn4+/Sn2+ couple revisited. Monatshefte für Chemie - Chemical Monthly. 2009, 140(11), 1293-1303.
Among other elements, dispersed silver holds a special place because of its protective biocidal effect and specific physicochemical characteristics depending on the particle size and shape.
Absorption spectra of silver hydrosol were monitored in processes of Ag NPs formation in reduction reaction Ag+ (AgNO3 or Ag2SO4 as precursor) by tannin. The dependence of the optical absorption on the wavelength in the long-wavelength range of Plasmon spectra has been analyzed in terms of the Mie theory and some original method. Several parameters may be estimated, such as the volume fraction NV of metal particles, the effective concentration Ne of conduction electrons, and the damping factor gamma of the metal electron plasma vibrations (this factor is related to the particle conductivity). The most interesting are the changes in gamma that connect with surfaces defects. It was found that in case of AgNO3 precursor the increase of NV leads to gamma decrease with oscillations for both parameters when reaction Ag+m = Ag0m proceeds.
At low temperature, the stable silver particles (10 nm in diameter) undergo aggregation (rearrangement) because silver surface becomes defective. At 77 K changes in NV and gamma are great and the tunnel mechanism of surface defects formation was proposed. The defects include mobile small surface clusters H+(H2O)n and OH-(H2O)n. We compare the influences of precursor and Ag NPs concentration.
Colloid lithography represents the simple and efficient approach for creation of a large-scale template for subsequent surface patterning, deposition of periodical metal nanostructures or periodical surface modification [Burtsev et al., 2018, doi.org/10.1016/j.apsusc.2017.10.055]. This approach, however, is significantly restricted by its ability to create only limited number of structures with confined geometry and symmetry. In this work, we propose the vapor annealing of ordered PS microspheres array, followed by surface grafting with diazonium salts as a process for creation of structures with required geometry and symmetry. Application of vapor annealing allows the effective tuning of PS microspheres morphology and altering of the size and shape of microsphere blocked underlying surface area. As a result, the subsequent grafting procedure [Guselnikova et al., 2018, doi.org/10.1016/j.colsurfa.2016.12.040; O. Guselnikova et al., 2017, doi.org/10.1002/admi.201701182] leads to the creation of ordered micropores array with tunable size or, moreover, columnar array. Combination of ethanol and toluene solvents with slight heating was found to be suitable for PS microspheres vapor annealing. The success of the grafting procedure was verified using the voltammetry and Raman technique. The local Au surface screening by PS microspheres and formation of the periodical organic layer, during the grafting through the PS mask, were confirmed by AFM, conductive AFM and SEM-EDX techniques [O. A. Guselnikova et al., 2017, doi.org/10.1002/polb.24282].
ACKNOWLEDGEMENTS: This work was supported by the Czech Science Foundation under the projects 18-26170S.
Surface integrity plays a key role in the surface modifications and coating processes that provide high and long-term performance of the treated components. The argon ion bombardment is commonly used in many surface modification processes and for the surface pre-treatment. The effect of argon sputtering cleaning on the internal stress, hardness and surface morphology of commercially pure titanium is investigated in this work. The titanium samples were mechanically polished and then etched by argon ions. The thickness of sputtered layer was measured by quartz thickness monitor. The hardness was investigated by nanoindentation, residual stress was measured by X-ray diffraction and surface morphology was monitored by atomic force microscopy. Removal of the surface layer by argon ion bombardment caused a decrease in residual stress and a decrease in hardness. Uneven sputtering of grains resulted in increased surface roughness. The observed changes in surface properties increased with increasing thickness of the removed layer.
Three alternative approaches to conventional laser based secondary neutral mass spectrometry are explored, the laser preionization, 2-color postionization and adaptive postionization. In preionization, the sample surface was first irradiated with a laser pulse (100 fs duration, 10^10-10^11 W/cm^2 intensity, 1240 nm wavelength) and subsequently bombarded with primary ions (Bi3+, 10 ns duration, 25 keV energy). Multiple correlation patterns were observed in the mass spectra confirming the mutual laser-SIMS interplay in the preionization mechanism. In the 2-color postionization, by mixing a fundamental laser field, with wavelength of 1240 nm and the intensity of 1×10^15 W/cm^2, with its second harmonic component, a control was attained over the ion yield. A significant alternation of ion yield, as increase/decrease of ion intensity, was demonstrated for both bulk silver surface and silver nanoparticles on surface. Finally, in the adaptive approach, the SIMS technique was combined with a near infrared femtosecond laser postionization based on an adaptive control through a laser pulse shaper. Versatility was confirmed by optimizing the ion yield for different molecules (tryptophan, anthracene, polyethylene, and oxalic acid) with focus on parent ion enhancement, fragmentation process, sublimation effect, and excited secondary species.
Chitin and chitosan are of great interest in the field of pharmaceutical, corrosion, medecine and engineering.
In this study, nanocrystallite shrimp shells has been prepared by using a high-energy planetary ball with an optimal rotational speed.
The raw material was subjected to standard chemical processing for chitin extraction, followed by deacetylation to obtain nanocrystallite chitosan, which is characterized by Scanning Electron Microscope (SEM), Energy Dispersive X-ray (EDX), X-ray Diffraction (XRD), and Fourier Transform Infrared Spectrometry (FT-IR).
In recent years, nanoparticles have high importance in various areas such as biomedical, environmental or pharmaceutical applications due to their chemical and physical properties. In all these applications, maintaining control over the particle size and shape is of high significance due to their size and shape-dependent properties. The most abundant method of synthesis of nanoparticles is a batch process because of its fast and easy reaction setup. However, many types of nanoparticles are very sensitive to reaction parameters which directly affect the size and shape of the final particles and the process is hardly reproducible.
In this work, we present nanoparticle synthesis using microfluidic devices. Compared to a batch process, microfluidics offers a high control over the reaction process by easy control of the system parameters (e.g. mixing and flow rates of reactants and reaction time) with the ability to make an operative change of parameters during the synthesis. Specifically, the synthesis of silica and silver nanoparticles using a droplet generation microfluidic device will be presented. The size and morphology of final nanoparticles will be analyzed and compared to traditional batch methods.
Synthesis of nanoparticles was possible employing a Nd:YAG pulsed laser at fundamental harmonic. The production of nanoparticles in water depends mainly by the laser parameters (pulse duration, energy, wavelength), by the irradiation conditions (focal spot, repetition rate, irradiation time) and by the medium where the ablation occurs (solid target, water, solution concentration). The nanoparticles can be introduced in solids, liquids of gases to change many physical characteristics.
The optical properties of polymers and solutions, the wetting ability of liquids, the electron density of laser-generated plasma, represent some examples that can be controlled by the concentration of metallic nanoparticles (Au, Ag, Ti). Some bio-medical applications will be presented and discussed.
Nanocomposite system formed by poly(vinyl acetate) (PVAc) matrix and halloysite nanotubes (HNT) filler was prepared in three different ways. The first method was kneading the melt in laboratory kneader. The second one was direct emulsion polymerization of vinyl acetate in the presence of HNT. The third method was the dispergation of HNT in toluene solution of PVAc in planetary ball mill. The filler content was 10 wt. % in all composites. The samples from all three preparation methods were subjected to the observation of nanoparticles dispergation efficiency within the bulk material using SEM. The best dispergation of particles was achieved using the ball mill. The particles were effectively dispersed, forming the agglomerates in the range from below one micrometer down to single nanotubes.
For many years the applications of ion track-etched materials have increased considerably, e.g., in charged particle detectors, nanopore sensors for molecules identification, ion-track filters, films with nanowires for magnetic studies, etc. Among the useful materials, well-susceptible to ion track recording, is Poly-Allyl-Diglycol Carbonate (PADC) that offers many advantages, such as ~ 100% detection efficiency for charged particles, high resistance to harsh environment, the lowest detection threshold, a high abrasion resistance and low production cost. These properties make the PADC particularly attractive for ion track detectors, even though its brittleness is disadvantageous, and to prepare a thin film (with a thickness < 500 μm) is still a challenge.
In this work PADC foils have been exposed to α-particles emitted by a thin radioactive source of 241Am and C+ ions accelerated at the Tandetron 4130 MC accelerator. The latent tracks generated in the polymer have been developed using a standard etching procedure in 6.25 NaOH solution. The dependence of the tracks’ geometry by the ion beam energy has been evaluated combining the information obtained by optical microscopy using a semiautomatic computer script (that selects ion tracks according the diameter and mean grey value), and nanometric resolution images by atomic force microscopy.
Two Prussian blue (PB) samples with different morphologies (spheres, mean size 160 nm; cubes, mean size 1.48 μm) and variable content of potassium (K-free and K-bearing) were used as a precursor material for the preparation of iron(III) oxides by solid state thermal decomposition method. A mixture of iron(III) oxide polymorphs (α-Fe2O3, β-Fe2O3, and γ-Fe2O3 nanoparticles) or pure maghemite (γ-Fe2O3 nanoparticles) were obtained by thermal decomposition of the cubic (K-bearing) or spherical (K-free) PB particles, respectively, at 350 °C in air. The particle’s morphology of the starting material (i.e. PB) was mostly retained after the thermal decomposition. The PB samples and the as-formed iron(III) oxides were characterized by using X-ray powder diffraction (XRD), 57Fe Mössbauer spectroscopy, and scanning electron microscopy (SEM). A high amount (58 wt%) of β-Fe2O3 polymorph was produced when K-bearing PB was used, simultaneously cubic clusters of maghemite were formed. We success in obtaining a single phase (maghemite) clustered nanoparticles with spherical morphology when used a K-free PB. The maghemite nanoparticles (4 nm) have proven to be superparamagnetic.
Sub-nanosecond electrical breakdown in dielectric liquids is of vital interest, e.g. for applications in high-voltage insulation and high-current switching. Liquid dielectrics in strong nonuniform electric fields are under influence of electrostrictive force that tends to move the fluid into the regions with higher electric field. If the voltage rise is fast enough, the liquid does not have enough time to be set into motion in order to reduce the internal stress. In this case the ponderomotive force induces significant stress in the bulk of the liquid which is manifested as a negative pressure. At certain threshold, the negative pressure causes cavitation ruptures of the fluid. Subsequently, free electrons can be produced by emission from the surface inside the cavity and accelerated to energies exceeding the energy for ionization of water and contribute to ultrafast electrical breakdown of water.
We present numerical model, which gives us basic ingredients necessary to study interaction of accelerated electrons with liquid water during sub-nanosecond electrical breakdown. We aim to determine geometrical conditions in electrode vicinity needed for electron multiplication and subsequent build up of space charge, for which we propose to use Monte Carlo software Geant4-DNA.
ACKNOWLEDGEMENTS: This contribution was supported by the Czech Science Foundation projects 18-04676S and 16-09721Y and LO1411 (NPU I) funded by the Ministry of Education, Youth and Sports of the Czech Republic.
Humic substances represent a wide range of organic compounds generated by gradual decomposition of plant residues and dead organisms in our ecosystems. They are among the most widespread compounds in the world that contain a huge amount of carbon in its structure. Is contains a lot of functional groups and mainly carboxyl -COOH group. We decided to use humic acid methylation to investigate the effect of the carboxyl group on our experiments.
Humic substances are able to bind various pollutants from Industrial production, agriculture and other human activities (like heavy metals, pesticides, herbicides, dyes, etc.). The interaction possibilities can be different: ion exchange, hydrogen bridge formation, coulombic interactions, hydrogen bridges, van der Waals interactions, hydrophobic interactions, absorption, etc.
The purpose of this work is to measure the decrease of selected initial concentrations of the selected organic dye probe (methylene blue) with a sample of lignitic humic acid and a methylated sample of that humic acid. The obtained humic acid sample will undergo a desorption experiment under the same time conditions. The output of the work will also monitor the ratio between the amount of adsorbed and desorbed methylene blue.
The results can provide more details abou the stability dye-humic complexes and the mobility of dye in systems containing humic substances.
Thin films of un-doped and Ni-doped TiO2 were synthesized by the sol-gel dip-coating technique and deposited on glass substrates, for different annealing temperatures (from 400 °C to 500 °C). The X-rays diffraction and Raman show the formation of anatase phase, we also notice that doping with Ni influence the intensity of anatase peaks and decreases of grain sizes (from 24.3 to 15.23 nm). The nanostructure Ni- doped TiO2 thin films was observed AFM, which shows that the elaborated films are smooth and dense with Rms values of about 3 nm. The calculate values of refractive index of thin films increases from 2.22 to 2.38, and reduction in transmittance and band gap with the increase in the nickel concentration. Vibrating sample magnetometer results of un-doped TiO2 thin films reveal a ferromagnetic behavior at room temperature with Ms = 0.67 10-4 emu and low content of nickel doping leads to an enhancement of the saturated magnetic moment Ms =1.11 10-3 emu.
Using polyvinylformol films produced in our laboratory of Radiotoxicology of CRNA, the influence on alpha surface barrier silicon spectrometry parameters, as energy shift, efficiency and resolution was investigated. The thickness of films was estimated with the ASTAR web databases. No significant deterioration of the alpha spectrometry parameters was observed when using thin films. Efficiency of the detection remains unchangeable and resolution decrease with 8% for a thickness of 63 g/cm . Alpha shift from spectrum can be used for measuring the thin foils.
The surface of metal oxides reconstructs in many ways depending on the crystallographic planes and preparation procedures [1]. In the case of iron oxides, the surface reconstruction of α- Fe2O3(0001) (hematite) is still controversial [2]. Under oxidizing conditions, it has been found that part of the surface accommodates a peculiar phase, called “biphase”, which has been traditionally attributed to a coexistence of tiny alternating island of FeO and Fe2O3(0001), while the rest of the surface remains stoichiometrically reduced [3].
In this work, we optimize the recipe to grow the “biphase” over the entire surface, allowing a reliable analysis with spectroscopic microscopic. The analysis brings a solid evidence that this
surface is composed of a single continuous layer of iron oxide with a unique structure, its own lattice parameter and orientation different than that of the α-Fe2O3(0001), giving rise to a distinct Moire pattern. We use DFT calculations to propose the atomic model that is best-matching the experimental data.
REFERENCES: [1] U. Diebold et al., Annual Review of Physical Chemistry, 61:129-48 (2010); [2] G. Parkinson, Journal of Surface Science Reports, 71, 272-365 (2016); [3] G Thornton et al., Phys. Rev. Lett. 72. 1961-1964 (1995).
Nanocrystalline diamond (NCD) films are increasingly studied due to their potential in life science. However, biomedical applications require not only the presence of chemically active and functional groups but also their long-term stability against aging, resistance to harsh conditions as strong acids and sterilization methods, etc.
In this study the aging-stability of chemical composition of H-, O- and F-terminated NCD surfaces exposed to open air and sterilization process was investigated by SEM, XPS, Raman and water contact angle (WCA) measurements.
The first sample set was aged in the open air for 60 days. The second set was ultra-sonicated in deionized water or rinsed in ethanol. SEM and Raman measurements revealed stable surface morphology and diamond character of aged and sterilized NCD films.
Wettability of aged F- and H-NCD films remained the same while the WCA of O-NCD films increased from 10 to 60°. The ultra-sonication slightly changed the WCA of H- and F-NCD samples while the O-NCD surfaces remained hydrophilic. The ethanol treatment influenced the WCA of H- and O-NCD samples by 20 % whereas the F-NCD films preserved its initial wettability.
XPS analysis revealed stability of initial oxygen content of the aged H-, O- and F-terminated NCD films. However, F-NCD films have lost 4 at.% of fluor content after aging. XPS measurements confirmed that surface chemistry of all treated NCD films was more or less stable after sterilization. The effects of autoclave treatments will be also outlined. All provided analytic techniques confirmed stability of NCD surfaces and their suitability for applied research in life science.
ACKNOWLEDGEMENTS: This work was supported by project 15-33018A (Czech health research council).
In this work, cadmium sulfide (CdS) thin films are prepared in different deposition time by a simple and inexpensive chemical bath method and this for their use as buffer films in the solar cells based on the heterojunctions. The influence of this deposition parameter on CdS films properties was investigated by characterizing the structure, optical transmittance and photoluminescence. The X-ray diffraction results showed the formation of CdS with hexagonal or cubic phases. The UV-Vis transmittance spectra of our films revealed a high visible transmittance varying between 60 and 80%. Furthermore, a significant increase in the optical band gap value from 1.8 to 2.27 eV as a function of deposition time is noted. The photoluminescence spectrum of each CdS film shows three emission peaks situated at 537.32 nm (2.3 eV), 568.45 nm (2.18 eV) and 692.72 nm (1.79 eV) at room temperature, which may be attributed to the: transition valence band to conduction band, excitonic transition, donor-acceptor (DAP) pairs recombination and sulfur vacancies defects (Vs) present in these CdS films.
Quantitative STEM imaging together with Monte Carlo simulations of electron scattering in solids can bring interesting results about properties of many thin samples. It is possible to determine thickness of a sample, to calculate mass of particles and measure mass per length/area. Appropriate calibration is one of the crucial parts of the method. Even a small error or inaccuracy in detector response to electron beam - either blanked or full - brings significant error into thickness determination. This problem can be overcome by parallel STEM imaging in more segments of the detector. Comparing more segments gives a possibility to use a signal from different segments for different thicknesses of a sample. Accuracy of individual parts of the detector depends on the captured signal quantity. It is desirable to use such a STEM detector segment that provides the greatest signal change to a unit of thickness. To demonstrate the usage, we used a sample of SiO2 nanospheres placed on thin carbon lacey film; diameter of the nanospheres was in the range of 80 and 160 nm in order to compare the results from different detector segments. Thanks to the known thickness of the sample (calculated from its geometrical shape), it is possible to estimate the optimal acquisition settings and post processing steps with the known and the true state of the sample.
ACKNOWLEDGEMENTS: The research was supported by CSF (project 17-15451S), MEYS CR (LO1212), its infrastructure by MEYS CR and EC (CZ.1.05/2.1.00/01.0017).
Aluminium oxide nanopowder is used for sintering into ceramic materials with attractive mechanical properties. The simplest and most common sintering methods are wet methods during which the nanopowder is dispersed in a liquid. High surface energy increases the quality of the sintered material. Atmospheric pressure plasma is known improve its wetting properties and the quality of ceramic sintered using the electrophoretic method. However, polarisation abnormalities during the deposition suggested an addition of negatively charged species on the powder’s surface during the treatment, probably NOX molecules. To verify this hypothesis, we have used the Thermal Desorption Spectroscopy on the treated and the untreated nanopowder to study the changes that occurred during the treatment. We have found that a large number of additional NO, NO2, CO2 and hydroxyl were attached to the surface, at least some of them were grafted rather than adsorbed. This provided additional evidence that the abnormalities were caused by NOX molecules on the surface.
Thin flexible self-supporting ceramics are new promising materials exploitable in many applications because of their unique combination of the physical and the chemical properties. These properties exceed the performance of polymers, glass materials or other insulators. In the following study, we present our findings of a special behavior of the alumina based dielectric barrier tapes with different thickness and material compositions. These tapes are investigated as substrates for dielectric barriers for surface dielectric barrier discharge with coplanar-like geometry.
Special geometry with various strip distances of silver coplanar electrodes was deposited on the surface of investigated ceramic barrier tapes. Oscilloscopic measurement was used to evaluate discharge breakdown voltage and voltage-current waveforms, for different ceramic materials and different discharge gaps. In this work we also present our easy and efficient method for measurements of electrical breakdown on the surface and inside of ceramic composites. A thermal camera was used to monitor increase of temperature of ceramic that can substantially influence measured breakdown voltage.
Since the discovery of graphene, the interest in two-dimensional layered materials expanded and so did the group of transition metal dichalcogenides (TMDs). The TMDs were considered as air stable materials as graphene at normal conditions. However, recent experimental study of Gao et al (Aging of transition Metal Dichalcogenide Monolayers, ACS Nano 2016, 10, 2628-2635) shows that monolayers of MoS2 and WS2 are air-unstable matarials at normal conditions. In our work we focused on 2H-MoS2 from theoretical point of view. To describe the whole oxidation process at atomistic level, we systematically calculated the reactivity of monolayer 2H-MoS2 with oxygen atoms using programme Vienna Ab Inition Programme (VASP) which is based on DFT. Our results proved the air-unstability of monolayer MoS2. We found out the oxidation started as adsorption of oxygen atoms at S atoms on edge which could be also replaced, and oxidation could continue as substitution of oxygen atoms instead of sulphur-edge atoms. Substitution led to conversion of MoS2 to MoO3 starting from the edge of monolayer 2H-MoS2 and it could spread further towards the center of the material. The results were published in Chemistry - A European Journal, 23(53), 2017.
The study presents the results of surface modification of polymers induced by atmospheric pressure non-isothermal plasma generated in reduction atmosphere. The technology based on diffuse coplanar surface barrier discharge (DCSBD), capable of meeting the industrial production requirements, was used with the aim to achieve highly hydrophobic surfaces. One rigid (PMMA) and three flexible polymers (PMMA, PTFE and PET) were treated without undesirable changes in their optical properties. The changes in wetting phenomena and surface free energy were observed depending on plasma treatment conditions. The most significant modification occurred on flexible PMMA foil. Using pure hydrogen plasma, we were able to achieve an increase of water contact angle up to ~127 from the original value 78° (untreated PMMA sample). Observed etching process on polymer surfaces and the changes in surface roughness were detected by a scanning electron microscopy (SEM) and atomic force microscopy (AFM).
Organic materials have risen to great importance in the world of electronics. Especially polymers have brought new possibilities to the field. With their numerous advantages like thermal stability, etch resistance and flexibility [1], organic compounds are growingly being studied and used for conductive layers, high resolution lithographic and packaging applications. In order to understand the logic behind the development and selection of such materials, it is fundamental to acquire a basic familiarity with the relationships between their structural parameters and physicochemical properties. Chemical depth profiling techniques like time-of-flight secondary ion mass spectrometry (ToF-SIMS) can help identify the relationship between the polymer chemical behavior when being bombarded by primary ions and their structural parameters.
In this work we present the characterization of Poly (methyl methacrylate) and Polystyrene thin films with varying molecular weights (2-9.9x105 g.mol-1) by ToF-SIMS measurements. It focuses on the in-depth investigation of the influence of the molecular weight of the mentioned polymers on the efficiency of the sputtering process, at different energies. The characterization was carried out using monoatomic Cesium sources with different energies for sputtering and Bismuth ion sources for analysis. Additionally, roughness measurement using Atomic Force Microscopy (AFM) were performed because the surface topographic change during sputtering is known to be one of the most important factors to affect depth resolution. The experiments show an inversely proportional relationship, with different orders of magnitude, between the sputtering yield volume (nm3/primary ion) and the molecular weight Mw. This tendency can be related whether to the studied polymers glass transition temperature (Tg) or to the initial solution viscosity.
REFERENCES: [1] J.M. Rooney, (1984) "Microelectronic Applications for Polymers: Structure‐Property Relationships", Microelectronics International, Vol. 1 Issue: 4, pp.32-35, https://doi.org/10.1108/eb044142; [2] Ninomiya, S., Ichiki, K., Yamada, H., Nakata, Y., Seki, T., Aoki, T. and Matsuo, J. (2009), Precise and fast secondary ion mass spectrometry depth profiling of polymer materials with large Ar cluster ion beams. Rapid Commun. Mass Spectrom. 23: 1601-1606. Doi:10.1002/rcm.4046.
Ceramic alumina nanofibers were prepared by electrospinning methode using polymer solution of polyvinyl alcohol (PVA) as polymer binder and aluminum nitrate nonahydrate (Al(NO3)3*9H2O) as ceramic precursor. Four different samples of nanofibres were obtained using various concentrations of PVA/ Al(NO3)3*9H2O solution. All samples were characterized by scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX), infrared spectroscopy (IR) and thermogravimetric analysis(TG/DSC). Part of every sample undergo plasma treatment in air at atmospheric pressure. The obtained results of plasma-treated and untreated nanofibres were compared and subsequently chosen approach to sintering process.
In this study, milife fabrics (polyester nonwoven fabrics) coated with copper (MC) were used. Three common silanes including octyltriethoxy silane, phenyltriethoxy silane and tetraethoxy silane have been prepared to treat MC. Surface morphology, electromagnetic shielding effectiveness (EMI), electrical properties, and the fundamental properties including thickness and air permeability have been tested. It was obvious that EMI of the MC treated with phenyltriethoxy silane ranging from 40 to 50 dB increases about 80% of the values of MC but other two silane coatings make negative effect on MC, despite that electrical properties of all the samples get decreased in different level after silane coating. In addition, SEM shows that different thin films have been formed on the coated fabric surface depending on the different types of silane used for the sol-gel coating and air permeability gets decreased correspondingly as well.
Ion track-etched membranes are porous systems obtained by etching of the ion tracks using a suitable etchant solution. In this work, control of the pores’ spatial profiles and dimensions in PET polymers was achieved by varying the mole concentration of the etchant, etching temperature and etching time. For determination of the pores’ shape ion transmission spectroscopy technique was employed. In this method, alterations of energy loss spectra of the transmitted ions reflect alterations in the material density of the porous foils, as well as alterations of their thickness. Simulation code, developed by the team, allowed tomographic study of the ion track 3D geometry and its evolution during chemical etching. From the doping of porous membranes with lithium-based solution and its analysis, the ability of porous PET membranes to encapsulate nano-sized material was studied. The study is is important for various applications, e.g., for catalysis, active agents, biosensors, etc. The ability to capture lithium was measured at the research reactor LWR-15 using neutron depth profiling technique that allows to determine the lithium depth distribution in the porous sample.
This work deals with the preparation of platinum nanoparticles using ionizing radiation - accelerated electrons with energy 4.5 MeV produced by linear accelerator Linac - 4 - 1200 Tesla VT Mikroel. Aqueous solutions of platinum chloride with Triton X-100 as a reducing and stabilizing agent were used. Solutions were irradiated with doses up to 20 kGy in 20 ml glass vials. Solutions containing platinum ions were colored from yellow to black color after irradiation, depending of the dose. This points platinum ions reduction and nanoplatinum formation. Irradiated solutions were monitored by UV/VIS spectrometry, photon cross-correlation spectroscopy to determine particles size and distribution, transmission electron microscopy and X-ray diffraction analysis to provide information on the forms of prepared nanoparticles. The effects of PtCl4 and Triton X-100 concentrations and also dose deposited energy were studied.
UV / VIS measurements imply that the nanoplatinum may be formed. The occurrence of the plasma peak around the wavelength of 215 nm indicates the existence of nanoplatinum. This peak, however, is not 100% directly detectable due to the degradation of UV / VIS spectrum in the UV area by Triton X-100 presence. Results from transmission electron microscopy and photon cross correlation spectrometry indicate that platinum particles with dimensions of about nanometers occur. In addition to these nanoparticles there also occurred larger particles due to the aggregation of nanoparticles in larger units. These large particles, however, have a minority part. X-ray diffraction analysis results indicate the presence of platinum diffraction peaks.
These results demonstrate the possibility of radiation preparation of nanoplatinum in associative colloids represented by Triton X-100.
Based on the experimental data, theoretical models which explain effects of annealing-induced hardening and softening by deformation in ultrafine-grained aluminum are suggested. These theoretical models describe the main micromechanisms of plastic deformation in ultrafine-grained aluminum subjected to annealing and high pressure torsion. In the framework of the models, the plastic deformation is assumed to be realized through the emission of lattice dislocations from triple junctions of grain boundaries and the glide of these lattice dislocations across neighboring grains which lead to the formation of walls of climbing grain boundary dislocations. The energy characteristics and the critical stresses of dislocation emission are determined. Theoretical dependences of the flow stress on the plastic deformation value are calculated. Our theoretical results demonstrate well agreement with the experimental data for ultrafine-grained aluminum.
Commercially pure titanium grade 2 was implanted with 90 keV nitrogen ions with different fluences. X-ray diffraction analysis was performed to obtain a phase characterization. The surface morphology was investigated by scanning electron microscopy and atomic force microscopy, and the nitrogen depth distribution was measured by glow discharge optical emission spectroscopy. The formation of continuous TiN surface layer was observed. The dependence nitrogen concentration on the fluence showed a nitrogen saturation limit. Oversaturation caused the surface blistering. The highest applied fluence led to the sputtering of the blisters and the formation of cracks.
Transparent polymeric materials (polymethylmethacrylate, polycarbonate, etc.) are very important for the manufacture of optical elements (e.g., lenses for glasses, solar panels, and monitor screens). Besides, they are a good substitute for heavy silicate glasses for cars and aviation. However, these polymers have a low abrasion resistance, small hardness (pencil hardness of 2B) and lose their transparency upon the long-term exposure to UV-light. The problem can be solved by applying coatings onto transparent polymeric materials that increase the hardness of polymers and simultaneously protect against UV and increase light transmittance in the wavelength range 350-1100 nm. In this work, coatings based on oligourethane methacrylate were obtained, and the pencil hardness of these coatings was investigated. As a result, an increase in the hardness of polycarbonate from 2B to H was observed. To increase the light transmission, a transparent coating based on nanoporous silicon dioxide SiO2 with a low refractive index of 1.20-1.30 was applied onto the first layer of oligourethane methacrylate nanocomposites by the sol-gel process. Thus, conditions for curing of two-layer coatings based on oligourethane methacrylate compositions and nanoporous SiO2 on polycarbonate were determined at temperatures 80-100 °C. The light transmission of polycarbonate with the two-layer coating increased from 92% to 94% in the wavelength range 350-1100 nm. ACKNOWLEDGEMENTS: This work was supported by Russian Foundation of Basic Research № 18-33-00907 mol_a.
Тhe immobilization of ZnO nanoparticles (NPs) on microporous support often demonstrate synergetic effect and enhance the photocatalytic performance of the hybrid nanomaterial, as well as facilitate the separation of NPs from the reaction system.
In this study, we aim to prepare ZnO/Zeolite (ZnO/Zeo) nanocomposites by different methods and to characterize the composition, morphology, surface area and absorption properties of obtained nanomaterials, and in the next step to test their photocatalytic properties. ZnO/Zeo were prepared by utilization of naturally abundant in Bulgaria zeolite, clinoptilolite and nano-sized ZnO semiconductor photocatalyst. Nanomaterials were synthesized by three methods: (i) precipitation of Zn(OH)2 precursor in alkaline aqueous solution on natural zeolite and annealing of resulting material to obtain ZnO/Zeo-1 composite; (ii) impregnation of sol-gel prepared ZnO on zeolite in ethanol solution and annealed at 400oC and 600oC to prepare ZnO/Zeo-2 nanocomposites; (iii) loading of Zn2+ ions on zeolite and further transformation to zinc oxide under calcination in air to form ZnO/Zeo-3.
The structure, morphology and surface chemistry of ZnO/Zeo nanocomposites were characterized by XRD, XPS, SEM, BET and UV-vis spectroscopy. The photocatalytic activity of synthesized nanocomposites towards methylene blue decomposition were tested and most appropriate method was evaluated for further synthesis and investigation of nanocomposites in other reaction of organic pollutants photodegradation.
Monitoring and counting of the fine particles during the temperature rise of the resorcinol-formaldehyde polymer suitable for conversion to carbon aerogel are discussed in the poster. Carbon aerogel is used as a supercapacitor and also in energy and water purification. It is produced by heat treatment under inert atmosphere. The approach combines the thermogravimetric analysis with detailed monitoring of the size distribution of fine particles produced. Thermogravimetric analysis (TGA) allows the exact temperature influence of the sample and identifies its weight loss. Aerosol stream leaving TGA enters a Scanning Mobility Particle Sizer (SMPS) where the particle size fractions are separated. A number of particles in the particles size fractions are identified by the condensation particle counter (CPC). By the long-term using of Carbon Aerogels results in degradation of these materials and release of fine particles, which could be harmful to health.
Phase transformation during hydrogen sorption was investigated in ten chosen magnesium-based hydrogen storage (HS) materials. Chemical composition of the materials consisted of Mg, as a principal hydrogen-binding element, additive X and amorphous carbon (CB), as an anti-sticking component. In order to assess the effect of X itself upon the structure, values of concentration of both X and CB were fixed to about 12 wt. %. The influence of X = Mg2Si, Mg2Ge, Mg17Al12, Mg5¬Ga2, NaCl, LiCl, NaF, LiF and two combinations Ni+Mg17Al12¬ and Ni+Mg2Si upon the changes in phase composition was tested. Phase content in HS materials was observed (i) after the intensive ball milling (BM), (ii) after the BM followed by hydrogen charging at 623 K and (iii) after the BM and one hydrogen charging/discharging cycle (C/D) at temperature 623 K. The study was carried out by SEM and XRD. It was found that, the C/D is approximately structurally reversible for X = Mg2Ge, Mg17Al12, NaF and LiF. However, additives X = Mg17Al12 and NaF decompose already during the BM. In alloys with combination of Ni with Mg17Al12, new phases NimAln¬ are formed. Phase composition changed during C/D for X = Mg2Si Mg5¬Ga2 and Ni+Mg2Si due to equilibration of phases composition. Observed structure changes of HS materials with chloride ionic additives NaCl and LiCl are, most likely caused by the relatively strong affinity between Mg and Cl. Hydrogen storage capacity of all studied alloys was 6.0 ± 0.3 wt. % H2.
There are many methods that allow detection of complex analytes such as soil contaminants and explosives, which are dispersed in the high amount of liquid and solid [Guselnikova et al., 2018, doi.org/10.1016/j.snb.2018.03.016; 2017, doi.org/10.1016/j.snb.2017.07.018]. Nevertheless, it remains a challenge to create a lab-on-a-chip (LoC) platform for on-line detection of small analytes amount (below the few femtoliters), with high sensitivity and specificity. It is expected that the combination of microfluidics and plasmonic will create a highly sensitive and affordable lab-on-a-chip platform and convincingly resolve this. The proposed approach will utilize the unique advantages of microfluidics that explore and uses unusual behavior of microscale-restricted liquids and surface-enhanced Raman spectroscopy [O. Guselnikova et al., 2017, doi.org/10.1002/cnma.201600284; Kalachyova et al., 2017, doi.org/10.1039/C7CP01828B], which is able to recognize the single molecule of the targeted analyte. In this work, we demonstrate the model of a micromixer incorporating with a plasmon active substrate. The design and realization of proposed experimental concept include the solving of following tasks: (i) utilization of Comsol software for mathematical simulation of possible processes in microfluidic mixer; (ii) preparation of microfluidic platform using 3D printing; (iii) application of excimer UV laser large-scale patterning and local gold deposition for creation of plasmonic active area. Our LoC platform allows detection of model analyte (R6G) at concentrations down to 10 fM (10−15 mol⋅L−1). Proposed unique features are the key to new scientific experiments and innovations in the field of lab-on-a-chip devices and analytical approaches.
ACKNOWLEDGEMENTS: This work was supported by the Grant Agency of Health Ministry 15-33459A.
Nano-sized materials become irreplaceable component of a number of devices for every aspect of human life. The development of new materials and deepening of the current knowledge requires a set of specialized techniques - for preparation/modification of the materials and analytical tools for proper understanding of their properties. A thoroughly equipped research centers become the requirement for the advanced materials research and development not only in nano-sized field.
The CANAM infrastructure in the Nuclear Physics Institute (NPI) ASCR Řež represents a scientific center with a wide set of techniques following every step from the synthesis and modification of nanostructures to their characterization using ion and neutron beams and microscopic techniques. These methods are involved in the new research fields of nano-sized, thin film materials comprising a wide range of materials and structures, such as: metal oxides, nitrides, carbides, carbon allotropes (fullerene, graphene etc.), nano-laminate structures (MAX phases), multilayers, etc.
These materials and structures can be prepared at NPI using different deposition techniques: ion beam sputtering, physical vapor deposition and molecular beam epitaxy. Based on the method, parameters and properties of the samples can be controlled and tuned, e.g., their composition, thickness (nm - μm), surface roughness, etc.
Advanced nuclear analytical methods can be applied for the sample characterization. They include RBS, RBS-channeling, PIXE, PIGE and micro-beam analysis installed at the Tandetron 4130MC accelerator, and Ion Energy Loss Spectroscopy using thin 241Am α-source, milli- and nano-probes of ions. Additionally, Neutron Depth Profiling (NDP), Prompt Gamma Neutron Activation (PGAA) and neutron radiography can be utilized at the nuclear research reactor LVR15 (operated by CV Řež) on the highly thermalized and intensive neutron beam.
The multimode AFM facility can further provide surface related information on morphology and magnetic/electrical properties with nano-metric precision. In addition, mechanical properties with a nano-indentation mode can also be inspected.
Grazing Incidence X-ray Fluorescence is a promising technique for analysis of nanostructures on solid surfaces. Interpretation of GIXRF data is usually done via forward calculations, so the experimental dataset is compared with result of some simulation. This is sometimes further automated via fitting the simulation result on the experimental data. The method used for simulation and capability of parametrization of the problem is therefore one of the crucial aspects of the GIXRF metrology. Simple analytical models have many limitations in the parametrization and in the amount of physical information that can be handled, e.g. they can not handle shadowing effects on densely covered surfaces. Here we present a numerical tool based on geometrical optics that can be used to simulate the X-ray Standing Wave (XSW) field in GIXRF experiments and thus to be used for data simulation. The algorithm is implemented on a graphics card to speedup the calculation and to allow use of the same fitting routines as the analytical models would use. Examples are shown on different artificial structures developed for purposes of GIXRF characterization.
Concrete waste after further processing can be used in the form of a micronized powder in which the unhydrated portions are reactivated. For this purpose, grid indentation and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM, EDX) are combined to determine properties of the concrete sample. The approximate composition of old concrete is calculated from these methods. The nanoindentation technique over two main material levels enabled evaluation of the indentation modulus of these phases due to the spectral deconvolution of measured data. Reverse reconstruction of indented areas concerning deconvolution results let to interlink of indentation and BSE diagrams. BSE diagrams are compared with SEM images analysis with BSE detector.
Lately, scanning ion conductance microscopy (SICM), has emerged as a versatile non-contact imaging tool. To obtain spatially-resolved electrochemical information, scanning electrochemical microscopy (SECM), also known as the chemical microscope, has been developed. Hybrid SICM-SECM techniques have been developed, in which the SICM compartment provides the accurate probe-sample distance control, while the SECM compartment measures the faradaic current for electrochemical information collection.
In this work, we demonstrate the use of an Atomic Force Microscopy (Park NX10) in combination with an ammeter for concurrent topography imaging and electrochemical mapping. The SICM-SECM probe consisted of a Au crescent electrode (AuE) on the peripheral of a nanopipette. High resolution probe-substrate distance control was obtained by the ion current feedback from SICM, while simultaneous electrochemical signal collection was achieved via the AuE from SECM. As a proof-of-concept experiment, a Au/Pyrex pattern standard sample was imaged with the SICM-SECM technique. The Au bar and the Pyrex substrate were clearly resolved from the SICM topography image, with the bar height and pitch width closely matching the actual values. In terms of the electrochemical property mapping, higher Faradaic current was seen when the probe was scanned over Au bar as a result of redox cycling, while lower Faradaic current was observed when the probe was over Pyrex substrate due to hindered diffusion. The capability of the SICM-SECM technique described here holds promise of many exciting applications in the field of electrochemistry, material science and battery research.