TiO2 nanocolumn arrays are prepared by porous-anodic-alumina (PAA)-assisted anodizing of Al/Ti or Al/TiNx layers in oxalic acid electrolyte. The Al layer is anodized at 40 V to form PAA; then the Ti or TiNx layer is reanodized to 100 V. This leads to the growth of anodic TiO2 or N-containing TiO2 nanocolumns within the alumina pores. The fabricated nanocolumns are approx. 40 nm wide and 160 nm long. To tune the extent of column exposure, the surrounding PAA is partially or completely etched, whereas the crystallinity and doping degree are modified by annealing in ambient atmosphere or in vacuum at 600 °C.
Cyclic voltammetry and electrochemical impedance spectroscopy (EIS) measurements of the nanocolumn arrays are performed in borate buffer in the dark. Mott-Schottky analysis from the EIS measurements in potential range between -1 V and 1 V vs. SHE reveals for the N-containing columns n-type semiconducting behavior, in contrast with most of the undoped TiO2 nanocolumns exhibiting dielectric properties. The calculated doping concentration and the flat-band potential vary with the annealing conditions. This allows us to conveniently tune the thickness of the depletion layer at the column surface in order to enhance their photoelectrochemical water-splitting ability by improving photogenerated charge carrier separation and band-gap tuning. In addition, Mott-Schottky analysis of the N-containing nanocolumns reveals the presence of surface states, as manifested by Fermi level pining, which may provide additional benefits for heterogeneous charge-carrier transport for water oxidation. ACKNOWLEDGEMENT: Research leading to these results was supported by GAČR grant no. 15-23005Y.
The intense 738 nm narrow band luminescence of the SiV-centers for polycrystalline nanodiamonds produced by shock wave synthesis followed by grinding and separation into fractions with median sizes from 25 to 1000 nm are observed for all fractions. Polycrystals composed of tightly connected differently oriented diamond nanocrystals with mean sizes of 10-15 nm were formed by merging the boundary areas of the crystal lattices of adjacent nanocrystals. Size-dependent structural and luminescent properties were studied by comparative Raman and luminescence spectroscopy. Analysis of the Raman spectra from luminescent diamonds with median sizes from 1000 nm to 180 nm shows damage of the intergranular layers with the increase of amorphous carbon content. Raman spectroscopy for the fractions from 180 nm to 25 nm shows damage of the cubic diamond nanocrystals with the appearance of disordered carbon structures, which increases with decreasing median size accompanied with a strong decrease of the luminescent intensity. It was found than SiV luminescence intensity has a maximum at the median size of about 180 nm that is controlled by competition between deactivation of the SiV-centers by defects in the diamond nanocrystal lattice and nonradiative recombination centers in the volume of the intergranular layers.
We report on characterization of wide bandgap semiconductors by conductive atomic force microscopy (CAFM) and ballistic electron emission microscopy (BEEM). In-house developed electronics was incorporated into commercial AFM/STM Veeco Multimode microscope to measure conductivity maps by CAFM and ballistic electron emission microscopy maps by BEEM. Spectroscopy characteristics obtained from the measured data by topographic correlation method are discussed. Bulk substrates of GaN and ZnO were treated chemically and by Ga+ focused ion beams to investigate charge transport on surface-treated surfaces with a nanometer resolution. The understanding of the electric charge transport and Schottky barrier formation at the nanoscale is essential for the application of semiconductor nanostructures in electronic and photonic devices; ACKNOWLEDGEMENTS: This work was supported by the Czech Science Foundation project 15-17044S.
Recently, the arrangement of diffraction primitives according to a phyllotactic model was presented. This arrangement was used to benchmarking purposes of the e-beam writer nano patterning. The phyllotactic arrangement has several interesting properties. One of them is related with the coherence between the nano- or microscopic domain of individual optical primitives and the properties of visually perceived images created by these structures in the macro domain. This paper presents theoretical analysis of the phyllotactic arrangement in the referred context. Different approaches enabling the creation of diffractive optically variable images are proposed. The practical part of the presented work deals with the nano patterning of such structures using two different types of the e-beam pattern generators. One of them is a system with a variable shaped beam of electrons, while the other one is a system with a Gaussian-shaped beam. E-beam writing strategies and the use of inherent spiral patterns for exposure ordering and partitioning are also discussed.
Polyhedron diamond shaped cobalt oxide (Co3O4) nanoparticles were fabricated using microwave assisted method followed by calcination at high temperature. The morphology of the prepared Co3O4 nanoaprticles was investigated by Transmission electron microscopy, Scanning electron microscopy and X-ray diffraction analysis. XRD analysis shows that Co3O4 nanoparticles are highly crystalline and made up of cubic unit cells. It was concluded from SEM and TEM images that prepared Co3O4 nanoparticles are of diamond-like in shape with diagonal lengths 165 and 117 nm. It was clear from images that Co3O4 nanoparticles are hollow from inside. Actually carbon dioxide gas was produced during synthsis which entrapped inside the lattice during arrangement of unit cells. That is why lattice looks hollow from inside. The product is well separated and very thin walled. Synthesized Co3O4 nanoparticles was used as catalyst for dry and aqueous media reaction at same time here. The catalytic thermal decomposition of ammonium perchlorate (AP) and catalytic reduction of 4-nitrophenol was studied here.. The catalytic thermal decomposition of AP was monitored by thermogravimetric differential scanning calorimetry. It was observed that only 1% amount of Co3O4 catalyst bring down the thermal decomposition temperature of AP by 100 oC. The catalytic reduction of 4-NP was monitored by UV-Visible spectrophotometry. The value of apparent rate constant was calculated as 0.309 min-1 for 0.001 g dosage of Co3O4 catalyst at 25 oC.
Fly ash is one of products of coal combustion process. It is removed from the flue gas stream and in the next step directed for landfills or for recycling purposes, eg. building industry, road industry. It is desired to limit the amount fly ash landfills [1], which can harmfully influence the sustainable development [2]. Fly ash chemical composition allows for the use of this material in differenced areas [3]. It should be noted that fly ash composition differs in relation to many factors: the composition of fuel used and the type of boilers.
Due to the favorable chemical composition of fly ash, its transformation into zeolites is one of potential, possibilitie of its use [4]. Crystalline, microporous zeolites according to unique properties have high industrial application possibilities [2] eg. in purification of flue gases [5]. The proposition of its synthesis out of fly ash is an economically attractive and justified option.
In this study the guidelines for the synthesis of zeolites based on fly ash were developed. Hydrothermal synthesis method was used. For the study ashes from the pulverized coal-fired boiler were selected. As a result of the experiments zeolite Na-P1 and sodalite were obtained. Changes in the concentration of NaOH used for the synthesis of products were investigated. The main purpose was to obtain higher synthesis yields and to confirm the literature data, stating that it is possible to receive another type of zeolite changing only the base concentration [6]. REFERENCES: [1] Official Journal of the European Union; Opinion of the European Economic and Social Committee on ‘The processing and exploitation, for economic and environmental purposes, of industrial and mining waste deposits in the European Union’ (own-initiative opinion) 2012/C 24/03; [2] Khadse Shaila, Dawle Nisha, Patil Pralhad, Panhekar Deepa, Zeolite Synthesis Strategies from Coal Fly Ash: A Comprehensive Review of Literature, Int. Res. J. Environment Sci. 4, 3, 93-99 (2015); [3] K. Galos, A. Uliasz-Bocheńczyk, Źródła i użytkowanie popiołów lotnych ze spalania węgli w Polsce, Gospodarka Surowcami Mineralnymi, 21, 1 (2005); [4] T. Suchecki, Zeolity z popiołów lotnych. Otrzymywanie i aplikacje w inż. Środowiska, Ossolineum (2005); [5] N. Czuma, K. Zarębska, P. Baran; Fusion synthesis conditions analysis on the SO2 sorption properties of zeolites produced out of fly ash; International Conference on The Sustainable Energy and Environment Development AGH UST in Krakow, 17-19.05.2016; [6] D. Bukalak, W. Nowak, I. Majchrzak-Kucęba, "Wpływ zawartości Si i Al. w popiele lotnym na tworzenie się frakcji zeolitowych typu Na-P1", Monografia pod red. J. Ozonka, M. Pawłowskiej, 58, 1, 36-47 (2009).
The main aim of this contribution is focused on deep study on transport properties of selected probe (Rhodamine 6G) in reactive hydrogels. Generally hydrogels, as a typical example of non-Newtonian liquids, represent important material either from scientific point of view, as well as from the view of possible applications. Hydrogels based on thermoreversible biopolymer agarose were selected in this work as a representative material for further research. The biggest advantages of the application of agarose hydrogel can be found in its simple and reproducible preparation procedure. Moreover, this non-reactive agarose matrix can be filled with additional homogeneously distributed molecules (e.g. polyelectrolytes), which can consequently represent the reactive part of such a hydrogel matrix. These reactive hydrogels were used as a model system for studying of both interactions in the systems as well as mobility of selected probe. In present work the different polyelectrolytes (e.g. sodium alginate, hyaluronic acid, sodium polystyrene sulphate and chitosan) were used as the reactive parts of hydrogel. The transport processes of reactive hydrogels were studied in this work by two individual techniques (both based on diffusion process). The first method deals with the simple macroscopic study on diffusion of Rhodamine 6G from solution into cuvettes containing agarose-based reactive hydrogels (diffusion model of constant source). The second technique used in this work was based on study of self-diffusion of Rhodamine 6G in hydrogels by using of the method of fluorescence correlation spectroscopy. Both utilized methods showed to be valuable for deeper description and characterisation of interactions and mobility of selected probe in reactive hydrogel-based matrices. The results are indicating that the transport and barrier properties of individual agarose-based reactive hydrogels are significantly affected by polyelectrolyte charge and its charge density. The results of present work in connection with deep meta-analysis of literature can significantly contribute to further applied research and development in the area hydrogels and carrier materials based on different biopolymers and polyelectrolytes complexes.
Recent advances in Nano-biotechnology, offer potential longer duration storage options for silver nanoparticles (SNPs) with preferable capping agents where a plentiful efforts have been given to minimize the toxicity effects SNPs. To overcome the toxicity scenario of SNPs, a novel green methodology was put forward in the present investigation. Biogenic SNPs were synthesised using water extract of Garden Rhubarb (GR) stems under ambient conditions. The method demonstrates an eco-friendly, instant and easy route for stable SNPs synthesis. The formation of instant SNPs was analysed by visual observation and monitored by UV–visible (UV-vis) spectrophotometer. The characteristic surface plasmon resonance (SPR) band at 445 nm, revealed the formation of SNPs. The X-ray diffraction (XRD) pattern of green SNPs showed their crystalline structure. SEM and TEM studies revealed that the shape of SNPs was spherical and has approximate diameter within 100 nm range. The zeta potential measurements on 180th day after SNPs synthesis, revealed the stability and size distribution of SNPs. The values are 29.6mV, 28.1mV and 24.1mV for three varied compositions of AgNO3 (1mM) and GR extract. The high dielectric constant (ε) has been observed for GR mediated SNPs, the ε values were found to reach the minimum value of 40000 at frequency 1MHz. Suitable tuning of the dielectric performances can conclusively prove their applications in multifunctional sensors, optical, and charge storage devices; ACKNOWLEDGEMENTS: The work was supported by MŠMT ČR-USA Kontakt II (LH14050) and NPUI(LO1504)Ministry of Education, Youth and Sports of the Czech Republic.
E-beam lithography is a flexible technology for various diffraction gratings origination. The e-beam patterning typically allows for the creation of optical diffraction gratings in the first diffraction order. However, the very high resolution enables also the patterning of structures providing the zero-order diffraction. Recently, we presented a work on the structural colors of metallic layers covering both regular-line structures and CGH (computer generated hologram) structures. This work presents a study dealing with zero-order diffraction structures with self-similar properties. The practical part of the work is focused on two aspects: design parameters and technological issues. Variations in design parameters include the tone of the structure (positive or negative), the density of filling, the filling factor, and the depth of the structures. The achieved gamut of colors may by primarily extended by the proper selection of metal deposition technology and its parameters, and further by the proper selection of the metal and the thickness of its layer; these are the technological issues.
Membranes are typically created by a thin silicon nitride (SIN) layer deposited on a silicon wafer. Both, top and bottom side of the wafer is covered by a thin layer of the silicon nitride. The principle of silicon nitride membranes preparation is based on the wet anisotropic etching of the bottom side of the silicon wafer with crystallographic orientation (100). While the basic procedure for the preparation of such membranes is well known, the nano patterning of thin membranes presents quite important challenges. This is partially due to the mechanical stress which is typically presented within such membranes. The resolution requirements of the membrane patterning has gradually increased. Advanced lithographic techniques and etching procedures had to be developed. This paper summarizes theoretical aspects, technological issues and achieved results. The application potential of silicon nitride membranes as a base for multifunctional micro system (MMS) is also discussed.
Bulk polymer materials are generally qualified as thermal insulators because they have low thermal conductivity, in case of amorphous polyethylene (~ 0.4 W/mK). On the other hand, single-molecule crystal of polyethylene exhibits many times higher thermal conductivity (~ 10 W/mK) and extremely high value of thermal transport was observed in case of polyethylene single chain (~ 100 W/mK). These new facts predicts the wide possibility of using as a cheaper alternative to the commercial metallic materials. Especially for heat conductive components such as computer chips, heat exchanger fins and so on. Moreover, their chemical stability and electrical insulation can be useful for other technological applications.
This contribution represents the equilibrium molecular dynamics simulation (Green-Kubo relation) to predict the thermal transport properties (especially thermal conductivity) of polyethylene. We focused on polyethylene single chain, single-molecule crystal and amorphous polyethylene and showed the difference of thermal conductivity between these structures. Moreover, the effect of temperature on the value of thermal conductivity was studied.
Metal nanoparticles show unique optical properties. Many methods for synthesis of such nanoparticles are quite simple in terms of implementation, but do not give consistently reproducible results. It complicates research wherein nanoparticles synthesis is just an intermediate step.
We developed a method of synthesis of bimetallic gold-silver nanoparticles with in situ seeding initiation by adding of sodium borohydride. We investigated influence of various parameters (pH, precursor ratio, temperature, mixing intensity and others) on the synthesis process. Thus, it was possible to select optimal conditions for the maximum reproducibility. The obtained nanoparticles were characterized by transmission electron microscopy (TEM) and changes of optical density spectra of the nanoparticles during their coagulation were studied. The described method allows quickly obtain non-toxic SERS-active nanoparticles with the maximum SERS enhancement factor about 10^5 which lies the near infrared range for Raman shifts, which are typical for biological objects such as bacterial cells and spores. ACKNOWLEDGEMENT: This work is supported by Ministry of Education and Science of the Russian Federation (Target funding, project №16.1812.2014/K).
One of the key technology issues of clean energy storage and power generation based on hydrogen is effective hydrogen storage. Magnesium is a prospective candidate base-component of hydrogen storage alloys, because its hydride, MgH2, contains 7.66 wt. % H2. However, lazy kinetics of MgH2 formation during hydrogen storage and reverse decomposition into Mg and hydrogen during its desorption is a serious obstacle that prevents a wide application of pure Mg as a hydrogen storage material. Great effort has been devoted in literature to find ways how to improve the sorption kinetics by catalysis. Particles of catalyzing phase(s) were deposited on the surface of Mg-rich grains that are the main hydrogen reservoir. They acted as entrance gates for hydrogen. In the present work, hydrogen sorption behavior of chosen ball-milled MgmXn intermetallics (X= Al, Ga, In, Si, Sn) was studied with the aim to judge the availability of MgmXn to catalyze the hydrogen sorption in Mg. The materials were prepared by induction melting of components (Mg with Al, Ga, In) and by subsequent ball-milling in hydrogen, or by ball-milling in hydrogen only (Mg with Si, Sn). Hydrogen solubility in MgmXn was estimated at temperatures 250°C and 350°C. Also the equilibrium hydrogen pressure of hydrides at 350°C was estimated.
The objective of this study is to evaluate the interaction mechanism of variously substitued coronenes binding monovalent anions and cations using quantum chemical tools. The aromatic receptors are mimicking the graphene monolayer and the substituents on the perifery are altering their fundamental properties. The variations of polarizability, electric multipole moments, binding energy, binding distance and finaly relative energies of CTESs are followed in the presence of an external electric field (EEF). EEF was found to have minor effect on both polarizability and quadrupole moment of the receptors and the trends observed for binding strength do not correlate. Contrary, the EEF-induced dipole moments and CTES energies are significantly affected. We observed correlation of the binding energies and the energies of CTESs, thus hypothesizing that the electron sharing and in extreme cases multicenter covalency are the terms contributing significantly to the complexation of the ion with extended π-receptors such as carbon nanostructures. In a nutshell, the wildly accepted view of electrostatically-driven ion adsorption on aromatic surface is questioned in our study and we provide data supporting that the quantum effects, i.e. exchange and correlation, determine to large extend the nature of these interactions. 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).
Nanoparticles are promising scaffolds for applications such as imaging, chemical sensors and biosensors, diagnostics, drug delivery, catalysis, energy, photonics, medicine and more. Surface functionalization of nanoparticles introduces an additional dimension in controlling nanoparticle interfacial properties and provides an effective bridge to connect nanoparticles to biological systems. With fascinating photoluminescence properties, carbon dots (C-dots), carbon-containing nanoparticles that are attracting considerable attention as a new type of quantum dot, are becoming both an important class of imaging probes and a versatile platform for engineering multifunctional nanosensors. In this study we focused on CQDs synthesis, characterization and stability study by spectrophotometric methods.
Plasma polymerized hexamethyldisiloxane (pp-HMDSO) coatings have been attracting interest of many researches. Due to their properties, these materials have a great potential to succeed in large field of applications such as protective anti-scratch layers on plastic substrates, corrosion protection coatings, barrier films for pharmaceutical packaging etc. Functionalized organosilicon plasma polymers have been investigated for development of unique biomaterials. Addition of a suitable dopant during plasma polymerization is one of the ways to form specific functionalities modulating chemistry, physical properties as well as biocompatibility of the films. In the present work, low pressure RF capacitively coupled discharge was used to deposite organosilicon thin films with nitrogen-containing functional groups on single crystalline silicon substrates. Resulting plasma polymers were investigated by several methods aimed primarily at determination of chemical composition, surface microstructure and mechanical properties. The present study includes results of Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, confocal microscopy, atomic force microscopy and nanoindentation, and their comparison with respect to deposition parameters.
Latest research on Zn(OH)2 found it to be a very interesting precursor in the synthesis of nano-ZnO with controlled size and morphology [1,2]. Doping Zn(OH)2 is expected to be a facile way of obtaining precursors for doped nano-ZnO, which is one of the most studied semiconductors for applications like spintronics, nano- and optoelectronics. Yet, this was a surprisingly challenging matter since following the same procedure (coprecipitation) as for the pure Zn(OH)2 but with small amounts of Mn2+, all of our doping attempts resulted directly in Mn-doped nano-ZnO. In order to understand these results, we performed a systematic study of the samples prepared without and with variable amounts of Mn2+ ions. XRD, TEM and FTIR investigations have shown a variation in the morphology of the samples versus the Mn nominal concentration. EPR spectroscopy has been used as the best suited technique to obtain information regarding the localization of the Mn2+ ions and local structure in the Zn(OH)2 and ZnO samples, based on our recent results on Mn-doped nanostructures [1,3,4]. REFERENCES: [1] S. V. Nistor, D. Ghica, M. Stefan, I. Vlaicu, J. N. Barascu, C. Bartha, J. Alloys Compd. 548 (2013) 222-227; [2] F. Demoisson, R. Piolet, F. Bernard, Cryst. Growth Des. 14 (2014) 5388−5396; [3] S. V. Nistor, M. Stefan, L. C. Nistor, D. Ghica, I. D. Vlaicu, A. C. Joita, J. Phys. Chem. C 119 (2015) 23781-23789; [4] S. V. Nistor, M. Stefan, L. C. Nistor, D. Ghica, I. D. Vlaicu, J. Alloys Compd. 662 (2016) 193-199.
The aim of this work is the study of mechanical properties of thin amorphous and nanocomposite SiOxCyHz films deposited on single crystalline silicon, glass and polycarbonate substrates. The films were prepared from mixture of hexamethyldisiloxane and oxygen using plasma enhanced chemical vapor deposition in capacitively coupled glow discharge reactor. The nanocomposite coatings were deposited under dusty plasma conditions. The film/substrate indentation response has been investigated from the near surface up to film/substrate interface using several different types of indentation techniques. The hardness, elastic modulus, fracture toughness and creep resistance of the studied films have been determined. Particular attention has been paid to the effects of the viscoelastic-plastic substrate on the indentation response of the film/substrate system. Additional analysis tools have been used like AFM, XPS and optical methods.
In nanowire-based three-dimensional device architecture (e.g. gate-all-around nanowire field effect transistors) it is required to intentionally grow nanowires at precisely determined location and, additionally, perpendicularly to the substrate. The former requirement was successfully met utilizing the so-called Vapour-Liquid-Solid (VLS) mechanism, where a eutectic catalyst droplet is used to localize the semiconductor material nucleation and growth to the droplet-substrate (liquid-solid) interface. The growth direction of VLS-grown nanowires and its manipulation is, however, a complex task attracting a lot of attention.
For semiconductor nanowire growth from the vapour phase, hydride precursors are commonly used and hydrogen is often utilized as a carrier gas. Here, using in-situ scanning electron microscopy and spatially-resolved Auger spectroscopy we revealed the essential role of atomic hydrogen in determining the growth direction of Ge nanowires with Au catalyst. With hydrogen passivating nanowire sidewalls the formation of inclined facets is suppressed, which stabilizes the growth in the <111> direction. By contrast, without hydrogen gold diffuses out of the catalyst and decorates the nanowire sidewalls, which strongly affects the surface free energy of the system and results in the <110> oriented growth. The experiments with intentional nanowire kinking reveal the existence of an energetic barrier, which originates from the kinetic force needed to drive the droplet out of its optimum configuration on top of a nanowire. Our results stress the role of the catalyst material and surface chemistry in determining the nanowire growth direction and provide additional insights into a kinking mechanism, allowing to inhibit or intentionally initiate spontaneous kinking.
The applications of nanoparticles or ultrafine glidant particles are increasing over the last years. In most of these industry applications the flow behavior of the particles is critical issue for the proper design of the processes and devices. Therefore flowability tests including ratio ffc (consolidation stress to unconfined yield strength), bulk properties measurements and novel patented angle of repose Zenegero method were performed. The new method is based on a continuous flow of particles whose flow dynamics doesn’t affect with the fall of bulk material the target arrangement of material pile. Evaluation of pile angle is performed at 8 views rotated around the perimeter of the pile ensuring more accurate result. The most commonly used glidant such as Aerosil®, Ca-O-Sil® and magnesium stearate were taken for three type of flowability tests evaluation. In order to understand the nanoparticles flow behavior was also determined their particle size distribution, compressibility and cohesion. Initial results show that new Zenegero method gives more comprehensive flow information and good sensitivity. In addition, it was confirmed that the flowability of glidant with a narrow particle size distribution leads to good flow conditions. This study reveals how choice of flow characterization method can play a key role in multi-factorial determination of the glidant type.
Tapping mode atomic force microscopy (TM-AFM) and scanning spreading resistance microscopy (SSRM) were found to be useful scanning probe microscopy (SPM) techniques for the characterization of surface conductivity and morphology of the conductive ceramic-like and graphene-containing nanocomposite prepared from polyaniline/montmorillonite (PANI/MMT) nanocomposite. In this work, the changes in conductivity and morphology of PANI/MMT nanocomposites before and after heat treatment are studied. PANI/MMT nanocomposite was prepared using oxidative polymerization of anilinium sulfate by ammonium peroxydisulfate in the presence of MMT particles (size fraction 40 µm). Prepared PANI/MMT powder was pressed into tablets using pressure 400 MPa. These tablets were calcined in dynamic argon atmosphere at temperature 1400 °C for 1 hour. The changes of local current on the surface and on the fractures (i.e. in the internal volume) of tablets were studied using SSRM and the local current maps of PANI/MMT nanocomposites before and after calcination were compared. SSRM shows that while after the calcination the conductivity in the internal volume of the sample strongly increased, the conductivity on the surface disappeared. Tapping mode is characterized by a less sample-tip interaction and, therefore, with respect to the nature of prepared nanocomposites, provides images without many visible artefacts. Electron microscopy, X-ray diffraction analysis, and Raman spectroscopy were used for further characterization.
The method of sample preparation is a widespread problem in all types of measurements from nanoparticles to coarse material. This article focuses on a specific method of sample preparation namely on determination of TiO2 nanoparticles size distribution. The treatment of sample comprising a higher number of nanoparticles is complicated. Nanoparticles often cluster together and thereby affect the course and the results of measurement. Therefore, a brief comparative study examining the effect of vibration on the degradation of nanoparticles and demolition of submicron agglomerates. Experimental work was carried out using a vibration exciter and the size of TiO2 nanoparticles was then measured on the CPS Disc Centrifuge DC24000 in the laboratory of Bulk Solid Centre Czech Republic. The study was performed on four different TiO2 samples, compared and evaluated for several time vibration periods. From the first results can be seen that slight changes in the composition of the sample greatly affect the degree of particles clumps comminution in the measuring liquid.
TiO2/Fe3O4 nanocomposites with various TiO2:Fe3O4 ratios were synthesized by an ultrasonic-assisted deposition-precipitation method and their UV-light decolorization of Congo dye and magnetic separation were investigated. The nanocomposite samples were characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), surface area analayzer (BET) and Fourier transform infrared spectroscopy (FTIR). The effect of TiO2/Fe3O4 ratio on the photocatalytic activity and magnetic property of the nanocomposites was studied by comparing their decolorization curves and magnetism in the presence of magnet, respectively. The results revealed that the decolorization efficiency and the chemical oxygen demand (COD) removal of TiO2/Fe3O4 nanocomposite with the ratio of 24/1 reached about 95% and 50%, respectively, within 60 min at room temperature. However, this sample showed the least magnetism. The TiO2/Fe3O4 nanocomposites with the ratio of 16/1 showed the optimum magnetism and photodecolorization activity. Also, the ability of synthesized nanocomposites in holding the adsorbed Congo red dye on their surface was investigated.
Originally, the e-beam lithography (EBL) is a technique for creating high-resolution black and white masks for the optical lithography. Multi-level relief structures can be also prepared using EBL patterning. Their preparation is based on the image patterning with a gradient of exposure doses. Large-area multi-level structures can be effectively prepared using the electron beam pattern generator with a variable shaped beam. We present several writing strategies. Basically, the main writing strategy uses one stamp (i.e. one elementary exposure of the shaped electron beam) per one elementary area with the same exposure dose. This simple approach is fast and flexible, however it does not guarantee optimal results. The main problem is an imperfection of the stamps (size, shape, and homogeneity). Advanced algorithms are based on multiple exposure of the same elementary area, the total local exposure dose is a sum of several different stamps. Using these algorithms, a smoother surface of the structure can be achieved. On the other hand, the writing speed is considerably decreased. Tradeoff between the achieved parameters and the writing speed is discussed for selected set of writing strategy algorithms.
Binary relief phase-modulated gratings provide symmetrical diffraction of the incoming light beam. Asymmetrical gratings, e.g. asymmetrical triangular blazed gratings, are characteristic by an asymmetrical diffraction behavior, where one of the first diffraction orders is more important than the other one. Electron beam lithography is a suitable and flexible tool for patterning of such kind of gratings. High quality results can be readily obtained when the period of the grating is relatively large and the relief depth is relatively low, this is the case of gratings with a small blaze angle. As the blaze angle increases, the quality of result suffers from several patterning-related issues. One of the problem is a reflection of the incoming light beam from the back slope (anti-blaze facet) of the blaze grating. We propose a novel configuration, with a ribbed (nano) modulation of the back slope . This modulation is perpendicular to the direction of the grating grooves. This paper presents an analysis of the proposed blazed grating configuration. E-beam pattern generator with a Gaussian-shaped beam was used to prepare a few samples of blaze gratings with a ribbed back slope. Results of the experiment are presented. Finally, we discuss the optical performance of two blaze grating with similar parameters, one of them is with the flat back slope and another one is with the ribbed back slope.
Humic acids were fractionated using using universal buffer solutions in the range of pH values 2-12. The methods of dynamic light scattering and micro-rheology were used to investigate the molecular organization of humic acids in eluates. The obtained results were supplemented by ultraviolet/visible spectrometry, measurement of the zeta potential, conductivity and pH values. Fractionated humic acids had the supramolecular character and their molecular organization was strongly affected by pH value of surrounding medium. Observed changes in the secondary structure of humic acids were connected with the changes in colloidal stability, particle size distribution, polydispersity, and viscosity.
The various applications of Pd nanocrystals were reported in fuel cell, organic catalysis, SERS and hydrogen storage materials application. Among others, synthesis of Pd nanocrystal is important because this has different properties as per the particle shape. Especially, the thin film nanoparticle has optical property. Also the decahedron was reported to have high electrocatalysis due to twined boundary. We demonstrate that unreported ultrathin Pd decahedral could be exclusively prepared with generally controlled nanoparticles. The ultrathin Pd decahedral exhibited efficient optical, electrocatalysis and surface-enhanced Raman scattering activities due to their unique optical characteristics.
We have successfully synthesized Pd rhombicdodecahedron nanoparticles (RD NPs) and structurally heterogeneous nanoparticle with Pd and Au from rational design. Edge covered Pd nanoparticles (ECP NPs) were synthesized with partially modification of Pd RD NPs’ surfaces, and the catalytic active sites were observed through this elaborate modification. These NPs were used as catalysts in Suzuki coupling. Because of selective deposition of gold to the edge and vertex sites of Pd RD NPs, reactivity difference was occurred between two kinds of catalysts. This difference with physically blocked NPs could be direct evidence that edge and vertex atoms were main catalytic active sites instead of indirect evidences of past several researches. Pd RD NPs had higher reactivity compared with ECP NPs because the former had exposed edge and vertex atoms which had chemical activity because of lower coordination number. From the several experiments, the reaction pathway was turned out probably heterogeneous, and the catalysts had high recyclability in Suzuki coupling. Lastly, in previous researches about Suzuki coupling with high index facet NPs, for example, concave cube, their higher reactivity would be explained because of more numbers of catalytic active edge and vertex atoms compared with low index facet NPs. Further studies that the detailed investigation about surface modification of metal NPs were suggested, and through that kinds of studies, verification of exact chemical pathway of organic reaction with metal NPs would be necessary and important.
In the present investigation, composites based on basalt, PP, PET and jute are fabricated with basalt nanoparticles and epoxy resin. A high-intensity ultrasonic probe was used to obtain a homogenous molecular mixture of basalt nanoparticles and epoxy resin, thus the nanoparticles were infused into the resin through sonic cavitation. The loading effect of nanoparticles on the mechanical properties of the composites such as flexural modulus, tensile modulus and impact strength were measured. Dynamic mechanical analysis of all composites were done. Thermo-gravimetric (TG/DTG) composites showed that thermal degradation temperatures of composites shifted to higher temperature regions with the addition of basalt nanoparticles. Addition of basalt fiber improved the thermal stability of the composite considerably. Scanning electron microscopic images of tensile fractured sides of composites illustrated that better fiber-matrix interfacial interaction occurred in hybrid composites. Based on these results, it is clear that miscibility of nanoparticles in the resin is of prime importance with regard to performance.
The present work aims to investigate the characteristics of high temperature vacuum brazed WC-Co-NiCrBSi coatings deposited on 16MnCr5 steel substrate. The coatings characteristics like morphology, microstructure, chemical composition respectively the appearance of the interface with the substrate have been analyzed by means of Scanning Electron Microscopy (SEM) combined with energy-dispersive X-ray spectroscopy. The hardness profile of the cladding is evaluated with the help of a Vickers microhardness tester. Size, occurrence and distribution of pores and microcracks has been estimated using image processing of SEM micrographs. X-ray diffraction measurements performed on the feedstock powders (cermet and self-fluxing alloy powder) and subsequently on the brazed composite cladding, have been done in order to identify possible phase transformations. Tribological behavior is assessed with the aid of a tribometer utilizing a pin-on-disk testing arrangement. Corrosion resistance is appraised using the potentiodynamic polarization method in 3.5% NaCl solution at room temperature in a three-electrode cell configuration.
The described coating technology makes possible the deposition of high quality hardfacings, with minimal influence on metallic substrate. The achieved porosity degree (approximately 1 %) is similar to the values reported in literature. It was found that the mean coefficient of friction is approximately two times lower in the case of WC-Co-NiCrBSi composite, compared to the one of 16MnCr5 steel. Consequently, the wear rate of the coating is more than 20 times lower than that of the unprotected substrate material. The electrochemical measurements resulted in a lower corrosion current density, correlated with a significant improvement in the corrosion behavior.
Civil Engineering is a sector that is usually described macroscopically. The use of Nanotextile requires an understanding of various phenomena on a basic level, ie. In the micro and nano-scale. If you are in the macroscopic world we can influence some forces neglect. However, the negligence for nanotextile is not possible. Software, which are used for calculations of diffusion properties of building materials do not provide for modeling the properties of membranes nanotextiles satisfactory results. The probable cause is negligence complex internal structure of these materials. Modeling of physical and chemical properties of nano-membranes is essential for their successful use in various technological fields, including construction. As a suitable software seems Comsol MultiPhysic, since it is possible to model multiphysics happening, ie. that can be added to the modeling include the forces acting on the micro and nano level (for example van der Waals forces). It is also possible to record the program structure and will create a pre eg. in a text editor or AutoCAD and assign the material parameters.
Thermal conductivity is one of the key material properties. In the IC industry for example local thermal conductivity determines local heat generation which affects the performance of an electronic circuit. Furthermore, materials with low thermal conductivity, such as polystyrene, are used for thermal insulation of buildings. Scanning Thermal Microscopy is a method used for assessment of this property with high lateral resolution. The drawback of this approach, however, is the fact that it produces only qualitative results. In order to obtain quantitative data, we need a calibration standard with known properties. Such a standard needs to be calibrated both for its topography and thermal properties. We present an application of spectroscopic imaging reflectometry for mapping thickness inhomogeneities of silicon dioxide step sample and we compare the results with results obtained with a large area atomic force microscope.
Method for measuring the distribution of electric potential in the layer of polymer solution in the strong electric field is based on direct measurement of electric potential probes and electrometric amplifier. Depending on the position of the probe relative to the surface of polymer solution is a recorded value of the measured electric potential in the solution loaded into a strong electric field. They studied the changes of the electrical potential. They are so obtained relevant data for later evaluation and correction theoretical predictions behavior of polymer solutions in electric fields.
Scanning thermal microscopy is an important tool for measuring temperature and thermal conductivity distribution in microscale and nanoscale. It is used e.g. in microelectronics, where during the microchip development phase it is important to minimize the generated heat and to optimize materials and geometries used for heat management. Unfortunately, Scanning Thermal Microscopy still produces more qualitative than quantitative results and many artefacts of different origin can be seen on the measured data. One way to increase the reliability of results is to model the probe-sample interaction in parallel to measurements in order to see the influence of artefacts. We present a numerical tool designed for fast calculations of virtual Scanning Thermal Microscopy images based on use of graphics cards, simple Finite Difference Method and a client-server based user interface. Examples of software performance are given on various calibration samples.
In various fields of nanotechnology heat flux plays an important role, either as principle of operation or as an unwanted effect. There are different heat transfer models that can be used for heat flux simulations at microscale and nanoscale and that include different heat flux paths (air or material conduction, radiation, convection) and different regimes (ballistic, diffusive). There are numerous theoretical and numerical tools available in the scientific literature, however understanding their limits and mutual comparison is not easy. We present our steps in development of a simple reference model that could be used for such comparison. The model is suitable for many of the computational methods available and can be used for benchmarking the methods performance and accuracy.
Metal nanoalloys display many interesting properties, such as depression of melting point,1 plasmon resonance, catalytic activity and phase separation.2 Nanoalloys could be synthesized by many different routes. The solvothermal synthesis, especially in oleylamine1–3 appears as very convenient and hot injection technique should ensure homogeneous conditions for nanoparticle nucleation and growth.
AgNi alloy nanoparticles were prepared by injection of an oleylamine solution of metal precursors (different molar ratios, 0.4 mmol total amount) to a 4:5 mixture of oleylamine and octadecene at 230 °C. After 10 min, the reaction mixture was cooled down. Nanoparticles were washed, isolated, and redispersed in hexane for characterization.
Nanoparticles were characterized by DLS, TEM, ICP OES, and SAXS, UV-VIS, HT-XRD, SEM and VSM.
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). REFERENCES: [1] Sopousek, J., Vrestal, J., Pinkas, J., Broz, P., Bursik, J., Styskalik, A., Skoda, D., Zobac, O., Lee, J. Calphad-Comput. Coupling Phase Diagr. Thermochem. 2014, 45, 33–39.; [2] Sopousek, J., Zobac, O., Bursik, J., Roupcova, P., Vykoukal, V., Brož, P., Pinkas, J., Vrestal, J. Phys. Chem. Chem. Phys. PCCP 2015, 17 (42), 28277–28285.; [3] Sopousek, J., Pinkas, J., Brož, P., Buršík, J., Vykoukal, V., Skoda, D., Styskalik, A., Zobac, O., Vrestal, J., Hrdlicka, A., Simbera, J. J. Nanomater. 2014, 2014, 1–13.
Optoelectronic devices play very important role in life nowadays. Most of the devices are widely used in fields ranging from image processing and fiber optic communication to common consumer electronics (twilight switches, house security systems, …), where componets such as photodiodes, laserdiods, phototransistors, photomultipliers, optoisolators, LEDs or OLEDs are mounted.
Accurate procedure is neccesary during the preparation to achieve their fully functionality. Because the devices are mostly prepared as multilayer systems, there is a requirement of correct functional layers‘ thickness. The thickness of the layers could be checked not only during the deposition but also retrospectively in the case of some failures during their deposition. The method of ion beam milling can be used for cross section preparation and can achieve cross sections of soft materials or material combinations consisting of hard and soft components. This contribution deals with case study, where layers thickness of optoelectronical device were determined by SEM method on cross section prepared by ion milling.
Optical particle counters are commonly used for aerosol characterization in various areas of industry (e.g. testing of clean rooms, testing of filters or air pollution control) [1]. A custom optical particle counter based on light scattering (scattering angle of 90 degrees) is being built at the Czech Metrology Institute. Most commercially available devices use single-wavelength laser illumination. In our device, we employ a continuum light source instead. The intensity of scattered light is measured using an amplified photodetector (Si detector element, wavelength range of 200-1100 nm). Polystyrene latex spheres sized by electrostatic classifier are used as reference particles. Aerosol is produced using TSI 3076 atomizer. Theoretical discussion of advantages and drawbacks of continuum light illumination approach is based on Lorenz–Mie–Debye solution of Maxwell's equations, which allows the mapping between particle size and angular-dependent scattered light intensity. The experiments and corresponding pulse height analysis are compared to a reference instrument – the commercial device TSI AeroTrak particle counter model 9310. The custom-built instrument sizing accuracy and resolution are evaluated.
For many years the ferroelectric multilayer structures were studied in order to develop various applications such as FeRAM, sensors, etc. The continuous downsizing trend of the nowadays applications in the nanometric range and below poses serious problems concerning the morphological, structural and compositional characterization of the advanced materials. The quality of the deposited thin films as well as the interfaces between the ferroelectric layer and the electrodes play a fundamental role in the electrical behavior of the heterojunction (polarization hysteresis loops, C-V and I-V characteristics). Transmission Electron Microscopy (TEM) is able to provide complete details about the morphology, structure and chemical information of such heterostructures. In this work we use Scanning Transmission Electron Microscopy (STEM) and Electron Energy Loss Spectroscopy (EELS) to study the defects and atomic interdiffusion at the interfaces in ferroelectric BaTiO3/SrRuO3/SrTiO3 (BTO/SRO/STO) multilayer, using a Cs probe-corrected JEM ARM 200F electron microscope. The BTO and SRO layers have been deposited on STO (001) substrate by Pulsed Laser Deposition. Structural and chemical data at the interfaces have been obtained by high-resolution STEM imaging and EELS spectrum imaging (EELS-SI). Atomic resolution chemical maps extracted from the EELS-SI data cube are correlated with the Z contrast in the high-resolution STEM images to reveal the atomic interdiffusion across the interface. Annular Bright Field (ABF) imaging allow to simultaneously identify both the position and nature of the atomic species in a crystalline material. The atomic arrangement of both heavy and light atomic species across the interfaces in the BTO/SRO/STO heterostructures is revealed.
The main aim of this contribution is the study of mechanical properties of hydrogels systems by classical rheological techniques (oscillation measurements) and further correlation of mechanical properties with inner structural and mechanical properties determined by novel microrheological techniques (dynamic light scattering, fluorescence correlation spectroscopy). As a model hydrogel medium; agarose as a representative polysaccharide will be used. The main advantage of the agarose hydrogel is their thermoreversibility and non-reactivity. Therefore the agarose hydrogels can be prepared with defined properties. As the studied samples will be agarose hydrogels with different concentrations in mixture with biopolymers. As the suitable biopolymers; chitosane, alginate, hyaluronate will be used, and for comparison also polystyrenesulfonate will be used. The main emphasis will be taken on time and temperature dependence on mechanical properties determined by macro- and microrheological techniques. Further fluorescence labeling hydrogels samples will be studied and the ability of probes penetrated into the hydrogels.
The measurement of local mechanical properties plays an important role in the design of modern materials, such as e.g. thin films or composites. Hardness and related properties are commonly studied using nanoindentation instruments, which provide also basic data processing. However, the procedures for data processing are not always fully accessible to the user and may not be well suited for all problems. Measurement uncertainty issues are also often left aside, as well as issues concerning numerical aspects, and only few indications on the credibility of the results are given. The goal of this contribution is to establish a novel software for independent analysis of loading and unloading produced by nanoindentation studies, including basic treatment of uncertainties and systematic errors. Uncertainties are treated either using the uncertainty propagation law or Monte Carlo studies. The software is open-source and thus the user can easily implement also own routines.
The quantitative analysis of the chemistry at the surface of functional plasma polymers
is highly important for the optimization of their deposition conditions and, therefore, for their
subsequent applications. The chemical derivatization of amine and carboxyl/anhydride layers
is a well-known technique already applied by many researchers, despite some known
drawbacks (e.g. side reactions or uncomplete reactions) that could lead to "unreliable" results. In this work, X-ray photoelectron spectroscopy using “non destructive” depth profiling with argon clusters is applied for the first time to study derivatized amine and carboxyl/anhydride plasma-deposited layers. This revealed an additional important parameter affecting the derivatization reliability, namely the permeation of the derivatizing molecule through the target analysed layer, i.e. a composite effect of the size of the molecule and of the porosity of the layer.
This work deals with the preparation of silver nanoparticles using ionizing radiation. Silver nanoparticles and microparticles were prepared using several different ionizing particles: accelerated electrons and UV and gamma photons. The nanosilver was prepared from aqueous solutions of silver nitrate with either Triton X-100 or Brij L4 as the stabilizer and reducing ˙OH radical scavenger. The effects of AgNO3 concentration, dose and type of deposited energy – accelerated electrons, gamma rays or UV – were studied. UV-Vis spectrometry was used to determine the concentration of silver nanoparticles. Photon Cross-correlation Spectroscopy was used to determine particle size in dispersions. For accelerated electrons, it was confirmed using UV-Vis spectrometry that an increase in the dose and increase in the initial concentration of silver nitrate lead to a larger concentration of silver nanoparticles. Using photon cross-correlation spectroscopy, it was confirmed that 50-100 nm particles are produced and that smaller particles form in Triton X-100 than in Brij L4. Microparticles were prepared in Brij L4 by irradiation with UV photons For gamma rays with a low dose rate, it was confirmed that an equilibrium of sorts forms between the production and sedimentation of silver nanoparticles.
Thermal stability and surface effects on AgCu nanoparticles synthesized in solution of diethylene glycol and polyvinylpyrrolidone were investigated by Knudsen effusion mass spectrometry during slow heating. Selection of a mass range for mass spectra monitoring was performed on the basis of data acquired by direct inlet probe mass spectrometry. As follows from the measurements, the organic substance which protects the nanoparticles against coagulation suddenly and quantitatively evaporates at elevated temperatures during the heating process. The AgCu alloy and coating from inner part of Knudsen cell as products of the heating were analysed by laser ablation inductively coupled plasma mass spectrometry. The data were subsequently used for specification of surface effects on the nanoalloys. 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) under the National Sustainability Programme II and by the Grant Agency of the Czech Republic under the project GA 14-12653S.
In the last decade, X-B-C (X=Mo, Ta, W) emerged as prospective candidates for protective hard coatings employed in cutting and forming applications. According to theoretical prediction and first experiments, these materials exhibit a high stiffness in combination with moderate ductility.
In the present work a Mo-B-C nanostructured coating was prepared on WC-Co hard metal substrate by magnetron sputtering. The details of microstructure of deposited thin layer as well as elements redistribution and changes in phase constitution caused by subsequent annealing were studied by several experimental techniques, namely analytical scanning and transmission electron microscopy (AEM), high resolution electron microscopy, confocal microscopy and glow discharge optical emission spectroscopy (GDOES). The microstructure observations were correlated with mechanical properties characterized by means of nanoindentation experiments in both the static and the dynamic loading regime using a Berkovich indenter. Effect of the microstructure evolution on elastic modulus and indentation hardness of the coating is discussed.
This research has been supported by the Czech Science Foundation (Project 15-17875S).
Materials containing high-density ensembles of nanoscale twins (nanotwinned materials) exhibit the outstanding mechanical and physical properties - simultaneously high strength and functional ductility at room temperature. These characteristics are achieved due to operating of the specific deformation modes in nanotwinned materials. One of the specific modes in nanotwinned materials is viewed to be plastic deformation occurring through widening of nanoscale twins. A theoretical model is suggested which describes peculiar aspects of plastic deformation in nanotwinned materials. In the model, plastic deformation of nanotwinned materials occurs due to stress-driven migration of twin boundaries and lattice dislocation slip. The micromechanism of the twin boundary migration is represented by slip of partial dislocations along these boundaries activated by external stress. Energy and stress characteristics of this micromechanism are calculated. Also, dependence of the yield stress on the distance between the twin boundaries for nanotwinned copper (Cu) are calculated. Theoretical dependences of the yield stress on the distance between the twin boundaries are compared with similar experimental dependencies in the exemplary case of ultrafine-grained copper with nanotwinned structure. The theoretical results well agree with the experimental data. 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).
Recent years have seen a significant expansion of interest in nanomaterials. One of the reasons for this is that nanoparticles exhibit a number of extra properties relative to bulk material. Some of these properties can be effectively used in medicine or in electrical engineering.
Cu/Ni alloy nanoparticles we used two different methods of solvothermal synthesis - hot injection and continual heating. Ni(acac)₂ and Cu(acac)₂ were used as metal precursors. The alloys were prepared in a varying metal component proportions. Reactions were carried out at 230 °C under inert atmosphere. [1,2,3]
Prepared nanoparticles were characterized by DLS, SAXS and TEM to determine their size, shape and size distribution. The elementary composition was analyzed using ICP-OES. The presence of surface plasmon resonance was detected by UV-VIS. The results of both methods were appropriately compared. ACKNOWLEDGEMENTS: Research has been financially supported by the MEYS of the Czech Republic under project CEITEC 2020 (LQ1601). Authors thank the X-ray Diffraction and Bio-SAXS Core Facility of CEITEC. REFERENCES: [1] Sopousek, J.; Pinkas, J.; Vykoukal, V. Nanomaterials 2014, 2014, 1–13.; [2] Somorjai, G. A. J. Phys. Chem. C 2008, 112 (32), 12092–12095.; [3] Sopousek, J.; Vrestal, J.; Pinkas, J. Calphad 2014, 45, 33–39.
In this work we generalized and specified aerosol synthesis method of core-shell nanoparticles. This synthesis method was used with success in our previous publication about preparation of photocatalytic core-shell Si-ZnS nanoparticles. Reaction of two precursors takes place on the surface of carrier nanoparticles and leads to formation of photoactive shell. Likewise in other microemulsion methods, desired thickness of shell is achieved by limiting the extent of reaction. Unlike to the conventional microemulsion methods, both precursors are dissolved in a same solvent. In our method of application aerosol synthesis the carrier particles are dispersed in aqueous solution of the first precursor with a suitable concentration. This dispersion, which contains dispersed particles, is converted into a form of aerosol microdroplets in ultrasonic nebulizer. After that the aerosol is injected by air flow on the surface of a vigorously stirred solution containing the second precursor, which is in excess. The reaction near surface of carrier particles is largely heterogeneous and the shell growth is limited by an amount of the first precursor located in the aerosol droplet. Desired coating thickness is achieved by setting the initial parameters such as size and concentration of carrier nanoparticles and concentration of the first precursor. This work follows our previous publication, generalizes aerosol synthesis technology of core-shell nanostructures and discusses its prediction formulas accuracy.
This work deals with a composite material based on polymer/inorganic nanoparticles applicable in organic electronics as an active layer with thickness about hundred nanometres. Prepared composite, containing conjugated polymer MEH-PPV as a matrix and ZnO nanoparticles (NPs) as filler, was characterized using spectroscopic and microscopic methods and it was used for preparation of polymer light emitting diodes in next step of the research.
Creation of polymer/inorganic nanocomposite by incorporation of ZnO NPs in such polymer matrix leads to better injection of negative charge carriers from cathode into active layer material and thus the achieved electroluminescence of prepared device has much higher intensity (in several orders) in comparison that made from neat polymer. Moreover, excellent distribution and dispersion of NPs in polymer improve the homogeneity of radiation from whole device area.
In our contribution, we introduce method how to easily improve performance of polymer light emitting diodes by preparation of nanocomposite based on ZnO nanoparticles incorporated into the conjugated polymer.
Nanoparticles (NPs) are revolutizioning many fields of science and technology, often delivering unprecedented behaviors of the conventional materials. Hence, interest in usage of these novel NP properties is growing among all society, which intensifies the efforts to develop novel techniques providing uniform and stable NPs without the usage of toxic solvents and reducing agents. In this regard the cathode sputtering into glycerol seems to be a promising technique. It combines benefits resulting from easily acquirable monodisperse NP solutions with the possibility to control the particle size just by varying the temperature of the deposition process. This study deals with the preparation of metal NPs of defined sizes by adjusting the temperature during cathode sputtering of silver into glycerol. We chose glycerol due to its (i) biocompatibilty and (ii) significant temperature dependence of its viscosity, which was varied in temperature range from -10°C to 40°C. Metal NPs were investigated by ultraviolet-visible spectrometry, transmission electron microscopy and dynamic light scattering. In the temperature range from -10 to 15°C we observed a remarkable increase in NPs average size. However, when deposition temperatures exceeded 20°C, we registered a significant vaporization of glycerol, resulting in particle agglomeration. Our results indicate that the glycerol is suitable system for temperature-controlled deposition of metal NPs, enabling tuning of their size.