List of Abstracts 2017: POSTER SESSION A
Date: October 19, 2017
One of the ways to create new and improve existing elements of photovoltaics is the design development and synthesis of nanostructured materials with unique photovoltaic properties. This is achieved by superstructures based on complexes of semiconductor quantum dots (QDs) and metallic nanoparticles (NPs). Such superstructures combine either unique optical properties of QDs, such as high quantum yield and large values of extinction coefficients over a wide spectral range, and amplification of local fields near metallic NPs.
In our work we have obtained colloidal complexes of CdZnSe/ZnS QDs and Au NPs in organic solvents with different interparticle spacing, which is achieved by covalently bound amphiphilic ligands of different chain length. We have shown that the optical properties of QDs strongly depend on the distance to the Au NPs. This fact is associated with two competing processes: a resonant nonradiative energy transfer from a QD to a NP and an enhancement of the electromagnetic field near the Au NP. As a result of different procedures of chemical treatment during the complexes formation optimal chemical parameters to maximize the optical responses of QDs have been established.
The results obtained will expand the understanding of the interaction of components in hybrid nanostructured materials. The established principles of nanoobjects interaction will also open new directions for the development of nano-optics and nanoplasmonics.
The well-known morphological feature of structures containing InGaN/GaN MQWs is V-pits defect formation. These V-pits originate in InGaN QWs and they are created due to dislocations and strain present there. InGaN/GaN structures with a different number of QWs and different thickness of GaN covering layers were grown, measured by AFM and their PL properties were compared.
The depth of V-pits is the same for different thickness of GaN capping layer (30 – 100 nm) but it differs for the different total thickness of MQW structure (which contains from 10 to 30 QWs), as demonstrated by AFM images and depth profile measured on the deepest V-pit. The number of InGaN QWs increases the surface diameter of the V-pits as well as their depth.
Studied nanostructures were prepared by Aixtron 3×2FT CCS MOVPE system, equipped by LayTec EpiCurve TT apparatus. The active MQW region, prepared on sapphire substrates with GaN buffer layer, contains 2×5, 4×5 or 6×5 pairs of InxGa1-xN quantum wells (1.5 nm thick, x=0.06, 735 °C) and GaN barriers (6 nm, 800 °C) with GaN capping of 30 nm or 100 nm, respectively.
We have found that:
V-pits size (depth and diameter) depends on the total thickness InGaN layers and on the growth rate. Not on the capping layer thickness!
Fast exciton QW photoluminescence can be increased by thickness of GaN capping layer, higher In content and lower growth rate capping layer.
Semiconductor quantum dots (QDs) with tunable band gaps has been acquired a great interest for the production of high-efficiency light-emitting diodes (LEDs) [1]. Among the known nanomaterials, a significant place is occupied by ternary alloyed Cd-S-Se nanocrystals. Their unique optical and chemical properties, including perfect photoluminescence quantum yield (PLQY), tunable emission and photostability, are advantageous for LED applications. In the current research, we present an investigation of the optical properties of highly luminescent thin films of CdS0.9Se0.1 QDs in different polymer matrices. The CdS0.9Se0.1 nanocrystals were synthesized by modified synthesis route based on work of X. Peng et al. [2]. To protect QDs against the chemical influence of the environment and to achieve maximum luminescence efficiency, QDs were embedded in polymers of different chemical nature, such as poly(vinyl butyral-co-vinyl alcohol-co-vinyl acetate), poly(methyl methacrylate) and polystyrene. The CdS0.9Se0.1/polymer thin films with thickness from 500 to 900 nm and excellent dispersion of the nanoparticles have been deposited on ultra-clean glass substrates by spin-coating technique. Prepared thin films were highly transparent in the visible spectral range. The structural and optical properties were analyzed by X-ray diffraction, UV-VIS spectroscopy and transmission electron microscopy (TEM). The band gap of CdS0.9Se0.1/polymer thin films was found to be 2.25 eV. It has been shown that CdS0.9Se0.1/polymer thin films exhibit high photoluminescence with PLQY 91%, which increases with increasing QDs concentration in a polymer matrix.
REFERENCES: [1] S. Sullivan, W. Liu, P. Allen, J. S. Steckel, J. Sol. St. Sci. Tech., 2 (2) (2013) R3026-R3030.; [2] W. W. Yu, X. Peng, Angew. Chem. Int. Ed. 41 (13) (2002), 2368–2371.
The L21-structure Fe2AlTi intermetallics appears as one of the two phases in Fe-Al-Ti superalloy nanocomposites [1]. Experimental data related to low-temperature magnetic properties of this Heusler compound indicate that local magnetic moment of iron atoms is about 0.9 Bohr magneton [2]. In contrast, previous quantum-mechanical calculations [2] predicted Fe2AlTi to be non-magnetic. We largely solve this discrepancy between the theory and experiment by performing first-principles calculations which were both unconstrained and fix-spin-moment constrained when searching for the ground-state electronic structure. It turns out that only the latter approach results in a correct magnetic state of Fe atoms in Fe2AlTi intermetallics with their local magnetic moments equal to about 0.48 Bohr magneton. The impact of the magnetic state on mechanical and structural properties is analysed.
REFERENCES: [1] R. Krein, M. Friák, J. Neugebauer, M. Palm, and M. Heilmaier: L21-ordered Fe–Al–Ti alloys, Intermetallics 18, 1360-1364 (2010).; [2] E. Shreder, S. Streltsov, A. Svyazhin, A. Lukoyanov, V. Anisimov, Electronic structure and physical properties of Fe2Mal (M = Ti, V, Cr) Heusler alloys, Proceedings of the Third Moscow International Symposium on Magnetism (2005) pp. 220-223.
Fe-Al-based nano-composites with a superalloy-type of microstructure constitute a very promising class of materials. They possess a great potential as an alternative to the currently used steels in high temperature applications. Intermetallics-containing nano-composites, such as those with the Fe3Al compound being one of the phases, may open a way towards future automotive and energy-conversion technologies with lower fuel consumption and reduced environmental impact. Unfortunately, a wider use of Fe3Al-based materials is partly hampered by their moderate ductility at ambient temperatures and low strength at elevated temperatures. Therefore, current materials-design activities are focused on obtaining a comprehensive understanding of the dependence of materials properties on the structure and composition. We employ quantum-mechanical calculations to analyse relations between ordering tendencies of Al atoms in the disordered Fe-Al phase on one hand and thermodynamic, structural, magnetic and elastic properties of Fe-Al-based nano-composites on the other. In particular, coherent interfaces between Fe3Al and disordered Fe-Al phase with {001}, {011} and {111} crystallographic orientations are computed and analysed.
Fe–Si-B alloys are widely used as transformer magnets and magnetic cores because of their excellent soft magnetic properties. Fe70Si20B10 powders have milled in a high energy planetary ball mill (Retsch PM400) under argon atmosphere at different time of milling. The metal powders obtained have average diameter d50 of 2.5 to 10 µm. The introduction of B into Fe- Si can result in a decrease of magnetic anisotropy (therefore leading to decrease of coercivity).
The Nanocomposite magnetic cores were made from the Fe70Si20B10 powder obtained by high energy ball milling for different milling time. The powders particles were mixed with unsaturated polyester (UP) to obtain toroidal cores. Polymerization process was made under magnetic field H= 500 A/m, and ensured a preferential orientation of a powder particles.
Influences of the metallic powder fraction on soft magnetic properties as well as thermal increase under isothermal conditions were investigated along with the possibility to control these properties with the size and amount of powder fraction.
It was also found that the soft magnetic properties of the polymer composites can be controlled in a wide range and depends on mass fraction of the metallic powder Fe70Si20B10 in the composite, on shape and size of the powder particles and their orientation in composite.
The combination of well-known technology for nanofibrous materials production and carbon nanotubes is presented here. Electrospinning is technology offering many arrangement options. The needleless electrospinning with three different types of fiber generated electrodes – spinners was used to produce polymer electrospun nanofibers reinforced by carbon nanotubes. The study is focused to description of different types of spinning electrodes in behavior during electrospinning process with respect to final fiber morphology presented by fiber diameters. The comparison between production of blind AC and DC electrospun nanofibrous layers and nanofibrous layers reinforced by carbon nanotubes is studied here too.
A great attention is paid to carbon nanostructures and their application in conductive structures, antistatic components and anticorrosive layers today.
In this work will be presented study of different oxidation methods of graphite and carbon nanotubes (CNT) and the effects on their properties. We are able to prepare samples with different degree of oxidation (C/O ratio) according to the oxidation agents. Whereas carbon materials are oxidized by per acetic acid or hydro peroxide minimally, with per sulfuric acid is the increase of oxygen groups more evident. There are very slight destructions and defects in the end or in the middle of the fibres when CNT are used. If the oxidation agent is permanganate the increase of oxygen groups is enormous, however, there is significant destruction of CNT. The obtained products were characterized by Raman spectroscopy, XPS, SEM, AFM and elemental analysis.
By oxidation of carbon materials better electrical compatibility is achieved. Moreover, due to this oxygen groups the creation of chemical bond with supporting polymer system is much easier as well as improvement of carbon materials by connection with conductive polymers.
This work examines possible correlation between electromagnetic shielding efficiency and resistivity of thermoplastic polymer nanocomposites with carbon nanotubes. Polyoxymethylen was used as basic matrix to which nanoparticles in the weight percentage ratio were added. Multi-walled carbon nanotubes in various percentages by weight ratio were used as filler. The nanocomposite was made by the Arburg injection molding machine. For evaluation of electrical properties electromagnetic shielding effectiveness and resistivity of the final nanocomposite with and without nanofillers was evaluated. These results are compared and discussed. Correlation between electromagnetic shielding efficiency and resistivity of thermoplastic polymer nanocomposite is evaluated and prediction model is introduced in the conclusion.
We present a combined experimental and theoretical study aimed on the properties of surfaces of several 2D materials – graphene, fluorographene, molybdenum disulfide, and phosphorene. We measured their surface energies by using inverse gas chromatography for large interval of coverages. We calculated the surface energy of these materials using density functional theory approach and tested a variety of modern van der Waals corrected functionals. Additionally, we studied the behavior of small organic molecules (acetone, acetonitrile, dichloromethane, ethanol, ethyl acetate, hexane, and toluene) on the surfaces of these materials. Accurate experimental enthalpies in combination with theoretical modeling enabled us to indentify several phenomena related to surface adsorption: the adsorption enthalpies at low coverage (less than 2%) were influenced by the presence of high-energy sites, whereas the clustering of molecules altered the measured adsorption enthalpies at high coverage.
REFERENCES: Lazar P, Karlický F, Jurečka P, et al. J. Am. Chem. Soc., 135, 6372-6377, 2013; Lazar P, Otyepková E, Banas P, et al. Carbon, 73, 448-453, 2014; Karlický F, Otyepková E, Banáš P, Lazar P. et al. J. Phys. Chem. C, 119, 20535-20543, 2015; Lazar P, Otyepková E, Karlický F et al. Carbon, 94, 804-809, 2015; Lazar P, Otyepka M, Phys. Rev. B 91, 115402, 2015; Otyepková E, Lazar P. Čépe K, et al. Appl. Mater. Today, 5, 142-149, 2016
The development of 2D inorganic materials has attracted significant attention over the past few years in the field of nanotechnology. 2D materials such as 2D oxides (Perovskites) graphene derivatives (Fluorographene) and transition metal dichalcogenides ((Molybdenum disulfide) possess improved optical, electrical, thermal, magnetic and mechanical properties due to their size (nanosized). Germanane and Silicane which are classified as graphane analogues consist two new 2D materials whose properties are still under investigation[1]. The aim of this project was to synthesize and study Germanane and Silicane. Moreover the possibility to develop hybrid nanostructures using Germanane and Silicane matrices following top down synthetic methods (intercalation reactions, using Carbon dots and metal nanoparticles), was examined. The materials were studied using a variety of characterization methods such as X ray diffraction (XRD), Fourier transform infrared (FTIR), Raman and X-ray photoemission (XPS) spectroscopies and Atomic force and Scanning Electron microscopies(AFM, SEM) that proved the successful synthesis of the materials and revealed information about their structure and properties [2-3] (i.e. size, band gap).
ACKNOWLEDGEMENTS: IKY Fellowships of Excellence for Postgraduates Studies in Greece -SIEMENS Program.
REFERENCES: [1] N. Madhushankar et al., “Electronic properties of germanane field-effect transistors,” 2D Materials, vol. 4, no. 2, p. 21009, 2017.; [2] S. Jiang r et al., “The structure and amorphization of germanane,” Journal of Materials Chemistry C, vol. 2, no. 17, pp. 3185–3188, 2014.; [3] K. Nishimurar et al., “Characterization of Layered Polysilane,” Japanese Journal of Applied Physics, vol. 35, no. 3A, p. L293, 1996.
In the present work, two-dimensional graphene nanosheets were synthesised, characterized and subsequently modified for gas sensor and electrochemical measurements. We used microwave plasma torch discharge (2.45 GHz) operating at atmospheric pressure conditions. Argon was used as the working gas and ethanol vapours carried by argon were used as precursor for carbon nanosheets synthesis. Characteristic high surface-to-volume ratio of prepared material together with structural defects and various chemical groups on the surface serve as powerful combination for fast conductance changes upon adsorption. Therefore, prepared material consisting of graphene nanosheets was modified to perform different electrochemical measurements including gas sensing of ammonia and cyclic voltammetry characterization using several redox species.
Our samples were analysed by scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy to obtain an exact insight into the behaviour of prepared sensors.
Graphene-based materials show unique properties. These single layered materials consist of 2D structure of carbon atoms, belong to the strongest known materials, that are very mechanically flexible, optically transparent and that are excellent electrical and thermal conductors. Recently, several studies on these types of materials have highlighted the potential of this material for hydrogen storage (HS) and raised new hopes for the development of an effective solid-state HS media. In the present paper, the structure and HS properties of graphene oxide (GO) and chemically reduced graphene oxide (rGO) produced by different procedures were studied. Hydrogen sorption characteristics of GO and rGO were measured using the Sieverts-type gas sorption analyzer PCT–Pro Setaram Instrumentation. The study of HS was carried out at temperature range from 198 K to 423 K under hydrogen pressure from 1x10-4 to 4 MPa.
For the HS point of view, the advantage of GO or rGO compared to graphene, is the presence of multiple chemical groups that can be used for introducing modifiers and their superior spreading on the materials surface. The suitably functionalized GO or rGO materials could potentially exhibit outstanding HS properties.
Fluorographene represents a suitable 2D precursor material for synthesis of wide portfolio of graphene derivatives, including hydroxofluorographene,[1] thiofluorographene,[2] alkylated/alkenylated/arylated graphenes,[3] chlorofluorographene,[4] cyanographene and graphene acid.[5] However, one of the major challenges in the community is to equip graphene with metal bearing molecular species. Such hybrid materials offer a great potential in electrocatalysis, heterogeneous catalysis, energy storage and organic magnetism. In the present contribution, we present a strategy to prepare graphene derivatives with covalently bound molecular species thus creating advanced functional materials. The graphene functionalization developed in our laboratories utilizes specific chemistry of fluorographene, which involves simultaneous substitution and reductive defluorination.[6,7] This offers tailoring of the final composition of covalently bound graphene-molecule superstructures and their properties, which can be exploited in various applications.[8]
REFERENCES:
[1] Tuček J, Holá K, Bourlinos AB, Blonski P, Bakandritsos A, Ugolotti J, Dubecký M, Karlický F, Ranc V, Cepe K, Otyepka M, Zbořil R: Room temperature organic magnets derived from sp3 functionalized graphene. Nat. Commun., 8, 14525 , 2017.; [2] Urbanová V, Holá K, Bourlinos AB, Čépe K, Ambrosi A, Loo AH, Pumera M, Karlický F, Otyepka M, Zbořil R: Thiofluorographene-Hydrophilic Graphene Derivative with Semiconducting and Genosensing Properties. Adv. Mater., 27(14), 2305-2310, 2015.; [3] Chronopoulos DD, Bakandritsos A, Lazar P, Pykal M, Čépe K, Zbořil R, Otyepka M: High-Yield Alkylation and Arylation of Graphene via Grignard Reaction with Fluorographene. Chem. Mater., 29(3), 926–930, 2017.; [4] Lazar P, Chua CK, Holá K, Zbořil R, Otyepka M, Pumera M: Dichlorocarbene-Functionalized Fluorographene: Synthesis and Reaction Mechanism. Small, 11(31), 3790-3796, 2015.; [5] Bakandritsos A, Pykal M, Blonski P, Jakubec P, Chronopoulos DD, Poláková K, Georgakilas V, Cepe K, Tomanec O, Ranc V, Bourlinos AB, Zbořil R, Otyepka M: Cyanographene and Graphene Acid - Emerging Derivatives Enabling High-Yield and Selective Functionalization of Graphene. ACS Nano, 11(3), 2982–2991, 2017.; [6] Dubecký M, Otyepková E, Lazar P, Karlický F, Petr M, Čépe K, Banáš P, Zbořil R, Otyepka M: Reactivity of Fluorographene: A Facile Way toward Graphene Derivatives. J. Phys. Chem. Letters, 6(8), 1430-1434, 2015.; [7] Zbořil R, Karlický F, Bourlinos AB, Steriotis TA, Stubos AK, Georgakilas V, Šafářová K, Jančík D, Trapalis C, Otyepka M: Graphene Fluoride: A Stable Stoichiometric Graphene Derivative and its Chemical Conversion to Graphene. Small, 6(24), 2885-2891, 2010.; [8] Chronopoulos DD, Aristides B, Pykal M, Zbořil R, Otyepka M: Chemistry, properties, and applications of fluorographene. Appl. Mater. Today, 9, 60-70, 2017.
Acrylic fibres are one of typical wastes from textile industry. Till now are these fibres burned in or tucked to the rubbish dumps. Acrylic fibres are long time used source of carbon particles. Reason of them is in chemical structure a thermal behaviour of acrylic polymer, which is not meltable.
In this study is presented easy method to prepare nanostructural sphere shape carbon particles with diameter around one micrometre. Particles are prepared at 500°C in oven with protection against the oxidation. Particles are evaluated by standard methods.
ACKNOWLEDGEMENTS: Supported by: MŠMT Czech Republic, project SGS 21198 „Preparation of modified carbon sorbents“.
The fundamental interest in nanomaterials field is to understand the new physics that occurs due to size effects, reduced dimensionality and surface forces. Substances confined in a nanoscale environment exhibits unique properties, and has been the subject of much attention. Especially interesting have been the effects of phase transitions, structure and dynamical properties of substances in one dimensional pores. Recent investigations of confined systems have shown a rich phase behavior associated with melting in confined systems. The melting behavior of substances confined in nanopores of different inner diameter has been characterized by Dielectric Spectroscopy method. We find that the melting point inside pores strongly depend on pores size and the kind of pores applied. The shift of the melting temperature of confinement phase relatively to the bulk is determined by the wetting parameter, which is a ratio of the fluid-wall to the fluid–fluid attractive interactions. Numerous studies of water confined in porous matrices have been performed using a variety of methods, and have presented the formation of ice structures other than the hexagonal structure Ih found in bulk ice at ambient conditions. In order to better understand the phenomena which occurs at the nanometric scale we performed the research of structure of ice confined in different kind of nanopores (silica and carbon) by using Neutron Diffraction method. ND measurements for studies systems showed the evidence of different structure of ice than the Ih structure.
A lot of research in modern material nanoscience concerns carbon-based materials, among which fullerenes take very important role. The prospects of fullerenes are due to their good solubility in nonpolar solvents, which allows them to be used in various fields, including electronics, optics, cosmetics, and pharmaceutics. For biomedical aplications different organic solvents such as toluene, N-methylpyrrolidone (NMP) and benzene are used to obtain stable colloidal aqueous solutions of fullerenes. The exact mechanism of interaction between fullerenes molecules in organic solvents is still a matter of contention. Solutions of the fullerenes C60 and C70 in polar and non-polar solvents and their mixtures are characterized by various effects, such as the unexpected aggregation in “good” fullerene solvents, or solvatochromic effects in solvent mixtures. The temporal solvatochromic effect for fullerene/toluene/NMP solutions was observed by UV-Vis spectroscopy. Small-angle neutron scattering and dynamic light scattering were also carried out to evaluate the qualitative changes of C60 and C70 cluster structure in NMP/toluene mixture at various ratio of solvents. The combination of structural methods with UV-Vis spectroscopy helps to clarify and resolve question concerning correlation of solvatochromic and aggregation effects.
Electrorheological (ER) suspension are special class of systems, those physical properties, such as viscosity can be tuned using external electric field strength. Generally, they are two-phase systems consisting of solid polarizable particles and liquid insulating medium. After application of the external electric field, the particles are polarized and create the chain-like structures in the direction of the electric field streamlines. Such internal structure development resulting in the significant increase in viscosity usually in four orders of magnitude and more. This phenomenon is reversible, repeatable and once the electric field is switched-off the suspension become to its initial state. However, due to the usually various nature of dispersed phase and liquid medium, the sedimentation stability of the suspensions is the main issue. Also the ER performance of various systems based on conducting polymers is not sufficient, thus the development of the novel dispersed phases are still attractive. Moreover, graphene oxide (GO) particles and their hybrids were recently recognized as a suitable materials for ER suspensions. Hence, we were performed the SI-ATRP from GO surface as a novel approach how to provide GO-polymer particles with tunable conductivity and polymer layer in single step and thus solve the main drawbacks such as sedimentation stability as well as proper ER performance.
Electrorheological (ER) fluids are fascinating materials with a wide range of potential applications. However, low performance in electric field or poor sedimentation stability are the most serious limitations for these applications. To reduce the mentioned drawbacks various materials such as graphene were explored. Recent efforts to improve performance of the ER fluids led to the modification of the graphene with polymer substances. Herein, the proposed ER structures are based on the graphene oxide (GO) sheets controllably grafted with poly(methyl methacrylate) (PMMA). The oxygen-containing functional groups introduced by modified Hummers method enabled the immobilization of 2-Bromoisobutyryl bromide onto the GO. The controlled PMMA chain growth was performed by atom transfer radical polymerization resulting in the GO-g-PMMA entities. The reaction process was monitored by nuclear magnetic resonance spectroscopy and gel permeation chromatography. The successful grafting process was confirmed by infrared spectroscopy. Conductivity of the neat GO as well as the fabricated GO-g-PMMA structures was investigated using four-point method, while their reduction was examined by Raman spectroscopy. Such particles were further thoroughly dispersed in silicone oil (SO) and the ER performance of as-prepared ER fluids was investigated. The system containing the GO-g-PMMA exhibited superior dynamic yield stress and higher ER effects as the modified particles were able to develop more rigid field-induced structures, due to the enhanced particle conductivity and thus better response to external electric field. The results also showed that the presence of PMMA grafts enhanced the compatibility with SO, which was reflected in substantially improved stability against sedimentation.
Magnetic nanoparticles have unique physical and chemical properties in comparison to bulk magnetic materials. Magnetic nanoparticles which are based on pure metal phases (Fe, Co, Ni) exhibit better magnetic performance in comparison to their oxide counterparts. On the other hand, they have higher chemical activity and can undergo unwanted processes when are exposed to ambient conditions, e.g. oxidation, corrosion and agglomeration. The so-called encapsulation procedure preserves the specific physical and chemical properties of magnetic nanoparticles. Recently, it has been shown that the coating material in a form of few-layer graphene is believed to be the perfect encapsulation agent [1]. The few-layer graphene coatings perfectly isolate the encapsulated magnetic nanoparticle against corrosion and oxidation, and moreover the coating can be further functionalized in order to change its surface properties [2].
In this paper the synthesis of few-layer graphene encapsulated Fe-Co magnetic nanoparticles (GEMNs) is presented. GEMNs were synthesized using carbon arc discharge route [1]. The graphite electrodes contained various content of Fe and Co were used as initial precursors. The process was carried out under Ar-H2 atmosphere at 60 kPa and the discharge current of 70 A. The as-obtained products were purified in order to remove the non-encapsulated particles. The phase composition of GEMNs, their magnetic properties and diameter distribution can be precisely controlled by a simple macroscopic parameter, i.e. the content of the metal precursor in the anode. The synthesis procedure was selective and exclusively yielded few-layer graphene encapsulated nanoparticles. The obtained GEMNs had the mean diameter between 30 and 40 nm. The corresponding saturation magnetization reached even 160 emu/g. The phase composition studies showed that the inclusion of Co minimizes the formation of undesired paramagnetic austenite phase.
Acknowledgements: This work was financially supported partially by the GEMNS project granted in the European Union’s Seventh Framework Program under the ERA-NET EuroNanoMed II.
REFERENCES: [1] BYSTRZEJEWSKI M., ŁABĘDŹ O., KASZUWARA W., HUCZKO A., LANGE H., Controlling the diameter and magnetic properties of carbon-encapsulated iron nanoparticles produced by carbon arc discharge. Powder Technology, 2013, vol. 246 pp. 7-15; [2] KASPRZAK A., POPŁAWSKA M., BYSTRZEJEWSKI M., ŁABĘDŹ O., GRUDZIŃSKI I.P., Conjugation of polyethylenimine and its derivatives to carbon-encapsulated iron nanoparticles. RSC Advances 2015, vol. 5, pp. 85556-85567.
We propose the sputtering deposition providing Ti thin films with controlled properties such as preferential crystallography and residual stress using Kaufman ion-beam source. The Ti thin films with thickness of 80 nm were deposited on [001] Si wafer covered by SiO2 deposited by plasma-enhanced chemical vapor deposition. To achieve the required crystallography and stress properties, we investigated the different beam voltage of Kaufman ion-beam source and controlled the substrate temperature during deposition using a built-in heater. We used two X-ray diffraction methods to determine the planes parallel to the sample surface and residual stress. We also measured the current-voltage curves to determine the resistivity (ρ) and the thermal coefficient of resistivity (α) of Ti thin films at different substrate temperatures using 4-probe measurement setup. We showed that it is possible to prepare stress-free Ti thin films with pure [001] orientation at the lowest beam voltage of 200 V and substrate temperate of 273 °C. The corresponding lattice parameters a0 and c0 were (2.954 ± 0.003) Å and (4.695 ± 0.001) Å, respectively. Electrical parameters of this sample as the ρ and the α were (9.2 ± 0.1)∙10-7 Ω∙m and (0.0026 ± 0.0002) K-1, respectively. We found out that these layers are well suitable for micro-electro-mechanical systems where the pure [001] orientation, no residual stress and low ρ and high α are essential. We found that ρ and α are dependent on each other. The ρ value was 2x worse than the value for bulk material which is excellent result for a thin film with the thickness of 80 nm.
Substrates with ZnO (or ITO) conductive layers were covered by thin film of
amorphous hydrogenated silicon (a-Si:H) deposited by PECVD technique. Under a turbo-molecular vacuum (10-4 Pa) the reactive laser ablation (RLA) was used to cover this a-Si:H thin film by germanium NPs. The RLA was performed using focused excimer ArF laser beam (193 nm, 100 mJ/pulse) under SiH4 background atmosphere (0.5 Pa). As a target the elemental germanium was used. Reaction between ablated Ge and silane led to formation of Ge NPs covered by thin SiGe layer. Then the deposited NPs were covered and stabilized by a-Si:H layer by PECVD. Those two deposition processes was alternated and applied a few times. The Si:H thin films with integrated Ge NPs were characterized by microscopic, spectroscopic and diffraction techniques. I-V characteristics of final diode structures without and under illumination were measured as well as their electroluminescence behaviour.
We acknowledge the CAS project KONNECT-007 and the MEYS project LTC17029
INTER-COST Action MP1406.
Excitation of plasmon resonances in noble metal nanoparticles opens us the possibility of controlling light at the nanoscale. This attractive feature leads to a number of prospective applications in solar cells, biosensors, optoelectronic devices, nanoantennas, nanolasers. However, so far only a few of proposals have been implemented in practice, mainly due to high ohmic losses in metals in the visible range. It turned out that the optical resonances of dielectric and semiconductor nanostructures with high refractive indices can also contribute to the control of light overcoming the diffraction limit. As in addition to a variety of different optical resonances these structures have very low optical losses, they form an advantageous alternative to plasmonic metal nanostructures. Controllable fabrication of such nanostructures, in particular, silicon nanostructures is a prerequisite for the development of applications. A method for fabrication of silicon thin films with nanoholes (nanohole silicon) combining the technique of high vacuum deposition with metal-assisted chemical etching (MACE) was proposed and realized in this contribution.
A combination of ultrasonic seeding with nanodiamond powder and photoresist polymers is essential for the growth of diamond structures or patterns by selective area deposition (SAD). Moreover, the SAD supported by the laser interference lithography represents a simple, cheap and fast method for the fabrication of periodically-ordered diamond structures on large areas suitable for biosensoric, photonic or plasmonic applications.
Here we studied the influence of two different photoresist polymers (S1802 and ma1215 spin-coated at thicknesses 100 nm and 1.5 um, respectively) and their multi-layered combinations with nanodiamond seeding layer(s) on the nucleation and growth of diamond thin films. Before the diamond CVD growth the atomically flat (100) silicon substrates were treated in different ways employing i) only nanodiamond seeding layer (NL), ii) only photoresist layer (PL), iii) nanodiamond/photoresist layer (NL/PL) and other layer combinations: iv) PL/NL, v) NL/PL/NL, vi) PL/NL/PL. All the samples were loaded to the microwave CVD system to grow the diamond thin films at low temperature (300 °C) in H2/CH4/CO2 gas mixture for 3 and 9 hours. The film morphology and its quality were evaluated by scanning electron microscopy and Raman measurements.
Employing standard NL treatment resulted in the growth of continuous and homogenous diamond thin film. In contrast to this nucleation layer, using the PL followed by the NL resulted in very poor film morphology consisting of inhomogeneities and voids. Better film homogeneity was obtained for the NL/PL multilayer structure independently on the photoresist type. The best diamond growth was achieved for the sandwich-like interlayer structure consisting of NL/PL/NL. Based on SEM and Raman measurements we propose the model in which the 3D like nucleation essentially contributes to film homogeneity due to multi-layered design and polymer contribution to the diamond early stage growth. Our findings define technological bases for successful patterned diamond growth employing the laser interference lithography.
ACKNOWLEDGEMENTS: This work was supported by GACR project 17-19968S and Czech-Austrian bilateral project 7AMB17AT036 (CZ 05/2017).
Zinc oxide nanorods as a potential material for nanoscale devices were prepared by chemical bath deposition (CBD). Effect of quality of the sol-gel deposited seed layer on the vertical alignment of the nanorods to a silicon substrate has been investigated. Special focus has been invested in observation of heat treatment during preparation of seed layer by dip-coating. This method is a two-step process including actual immersion of the substrate into solution of precursor and a preheating step. The preheating needs to be done to thermally decompose the zinc acetate precursor into zinc oxide seeds. Three different temperatures of preheating have been compared (300°C, 350°C, 400°C) and quality of seed layers and vertical alignment of nanorods have been observed. When the preheating temperature was higher than 350°C, the seed layer consisted of smaller and denser crystallites with a preferential orientation along the c-axis. CBD growth of ZnO nanorods on these seed layers resulted in their good vertical alignment.
In recent years, the research on electromagnetic shielding materials has increased dramatically. The Electromagnetic shielding can be defined as to prevent the propagation of electrical and magnetic waves from one place to another by using either a conductive or magnetic material. The effect of EMI shielding can be accomplished by minimizing the signals passing through a system either by absorption or reflection of waves. The reflection of radiation from the shield is possible if the shield has mobile charge carriers [2] [2]. From these aspects, flexible conductive textiles have gained the popularity due to their satisfactory electrical conductivity, electromagnetic interference shielding effectiveness, electrostatic dissipation, breathability, and light weight. In a variety of manufactured forms such as fabric tape or foam gaskets, they are an important kind of materials for preventing electromagnetic interference [1]. For instance, these fabrics could prevent the possible explosions of guided aircrafts due to electromagnetic interference.
The present work deals with the development of electrically conductive, multifunctional and durable cotton fabrics by in-situ deposition of copper particles. The dynamic light scattering, SEM and XRD techniques were employed to study the morphology of deposited copper particles. The utility of conductive fabrics was analyzed for electromagnetic shielding ability over frequency range of 30 MHz to 1.5 GHz. The EMI shielding was found to increase with increase in concentration of copper particles. Furthermore, the role of deposited copper particles on antibacterial properties was examined against pathogenic bacteria such as Staphylococcus aureus and Escherichia coli. At the end, the durability of coated fabrics was examined against several washing cycles. The fabrics showed good retention of the copper particles, proved by SEM microstructures and small loss in the conductivity of the material after washing.
The synthesis of high-quality semiconductor quantum dots (QDs) has been evolving in the last 20 years since the first synthesis of CdSe QDs by Murray et al. [1]. QDs have been gained a great attention in both fundamental and applied research due to their unique chemical and optical properties. The direct dependence of the optical characteristics of QDs, their sizes and shapes is maintained for binary compositions CdS and CdSe [2], and for ternary Cd-S-Se system. Here we report about the easily reproducible and controllable synthesis of highly luminescent CdS1-xSex QDs capped by oleic acid. The hot-injection method applied in our laboratory includes the synthesis of cadmium oleate with further injection of sulfur and selenium complexes with trioctylphosphine (TOP) at 240 °C and allows controlled growth of nanoparticles. The developed strategy of extraction and purification made it possible to obtain very small monodisperse nanopowders (up to 3 nm) with face centered cubic structure. The quantum yields of pure nanopowders reach 91%. With an increase of the selenium content, a stable red-shift of photoluminescence was observed. The whole series of CdS1-xSex QDs exhibit narrow photoluminescence signals in the spectral region from 420 nm to 590 nm. The obtained nanocrystals were characterized by X-ray diffraction, UV-VIS and photoluminescence spectroscopy, EDS and TEM microscopy.
REFERENCES: [1] C. B. Murray, D. J. Norris, M. G. Bawendi, J. Am. Chem. Soc., 115 (1993) 8706.; [2] W. W. Yu, X. Peng, Angew. Chem. Int. Ed. 41 (13) (2002), 2368–2371.
This study is focused on the synthesis of core-shell type of magnetic particles, where magnetic core is carbonyl iron (CI) microparticles and conducting shell is poly(2-(1H-pyrrole-1-yl)ethyl methacrylate) (PPEMA) synthesized using atom transfer radical polymerization (ATRP) technique. In order to obtain core-shell particles the surface initiated (SI)-ATRP is applied, where both benefits, magnetic behaviour of core and conducting behaviour of shell, are advantages for their intended applications as materials for electromagnetic shielding of piezo-resistors.
Basic characterizations of the neat CI and CI-PPEMA particles such as magnetization saturation using vibrating sample magnetometry and conductivity using four point Van der Pauw method will be performed. Also the confirmation of the controllable coating using gel permeation chromatography and nuclear magnetic resonance will be provided. The successful modification of CI with PPEMA will be further investigated using Fourier transform infrared spectroscopy. It will be also proved by dielectric spectroscopy if such CI-PPEMA particles possess enhanced properties in comparison to neat CI particles for electromagnetic shielding.
ACKNOWLEDGEMENTS: The authors wish to thank the Grant Agency of the Czech Republic (17-24730S) for financial support. This work was also supported by the Ministry of Education, Youth and Sports of the Czech Republic – program NPU I (LO1504). Author J. M. gratefully acknowledge to APVV-14-0891 for financial support.
We present a study of synthesis of colloidal gold nanodumbbells (AuNDs) as a promising surface-enhanced Raman scattering (SERS) substrate. Gold nanoparticles exhibit resonantly enhanced absorption and scattering properties of electromagnetic radiation and enhanced local electric field, a phenomenon called the localized surface plasmon resonance (LSPR). The resonant frequency of LSPR and the local field distribution is primarily determined by the chemical composition and morphology of nanoparticles. We prepared AuNDs by the recently established seed-mediated growth method of AuNRs in the presence of iodide ions. Thus, decreased curvature of AuNDs tips leads to optical response and local field distribution different from AuNR seeds. Our results revealed that the morphology of AuNDs can significantly alter in time. This process can be accelerated e.g. by increasing the temperature, or limited by replacing the original solvation layer composed of cetyltrimethylammonium bromide (CTAB) for its covalently bonded analogue (16-mercaptohexadecyl)trimethylammonium bromide (MTAB). We believe that understanding these mechanisms can contribute to a fabrication of SERS substrate with a specifically tailored optical response stable even after the laser irradiation. The major methods employed to characterize gold nanoparticles were the absorption spectrophotometry and scanning electron microscopy (SEM).
ACKNOWLEDGEMENTS: This work was supported by the Czech Science Foundation P205/13/20110S project.
This paper deals with the synthesis of silver nanoparticles (Ag NPs) under different reaction conditions, such as temperature and UV irradiation. We investigated how these variant parameters can affect the final properties of Ag NPs, mostly their size, shape and stability. It is well known that diameter and shape of nanoparticles influence their physical, biological and chemical properties and thus predict their applications in different fields. Tailoring final features of Ag NPs during the synthesis gives us the possibility to prepare nanoparticles with required properties, specifically for antimicrobial or antifungal agents. The prepared nanoparticles were characterized by following methods; transmission electron microscopy, scanning electron microscopy, dynamic light scattering and absorbance in UV - VIS region.
1D ZnO nanostructures and, more specifically, nanorods have attracted increasing interest in recent years due to their potential in optoelectronic applications. The lack of p-type ZnO emphasizes the importance of rectifying junctions realized on other p-type materials, either inorganic or organic, to form heterojunctions with n-type ZnO. Among different p-type materials, GaN is promising due to similar lattice constants with ZnO.
In our work nanosсaled heterojunctions were created by a simple wet chemical process. To control the position and size of ZnO nanorods, polymethylmethacrylate submicron patterns were prepared on the GaN template using focused ion beams. Selective growth was achieved only on patterned holes where the GaN template was exposed to the growth solution.
Current-voltage characteristics of a single ZnO nanorod/GaN heterojunction were measured in Tescan Lyra 3 GM FIB/SEM chamber using a SmarAct nanomanipulator with a tungsten probe. Ohmic contact on p-GaN was prepared by thermal evaporation of a 50nm film of Ni covered with a 40nm film of Au, which were subsequently anneled at 500C.
The nanoscale n-ZnO/p-GaN heterojunction showed rectifying behavior. The impact of the nanorod deformation on the shape of the I-V curves is investigated. The influence of the annealing regime оn the electrical conduction mechanism in the GaN/ZnO nanostructures is discussed.
ACKNOWLEDGEMENTS: This work was supported by the Czech Science Foundation projects: 17-00546S and 15-17044S.
Substrates containing zinc oxide and different amounts of gadolinium for biosensorics were obtained for the first time by the standard sol-gel technique. This is a new material has not yet been extensively studied.
In this paper we present the results of the photoluminescent response of the zinc oxide surface when it is modified by various amounts of gadolinium during the classical sol-gel method of the surface obtaining. Aspects of creating a modified surface of zinc oxide are highlighted. The used concentrations of gadolinium vary from 1 to 33% caused both quenching and ignition of photoluminescence at the wavelength of 356 nm upon excitation into the absorption band of protein 280 nm. The photoluminescence intensity of zinc oxide without doping is 40 relative value units , the addition of 8% Gd increases the photoluminescence by 7 times (280 r.u.), the addition of 31% Gd decreases the photoluminescence by 40 times compared to undoped zinc oxide. These results are of great interest for the practical application of biosensor devices on zinc oxide because of its influence on the key characteristic of the sensor as selectivity.
In our study, we aimed to synthesize superparamagnetic nanoparticles able to isolate and immobilize and thus preconcentrate flavonoids for subsequent analysis.We report the optimal conditions such as different pH of Britton Robinson buffer, temperature and time of incubation on the isolation of different types of flavonoids, such as Genkwanin and Pratol from extracts of freshwater algae. For the determination and their characterization was used an Agilent 1200 Series Rapid Resolution LC system coupled on-line Agilent Technologies 6460 Triple quadruple MS detector with Agilent Jet Stream (all from Agilent Technologies, Waldbronn, Germany). We modified surface of nanomaghemite (γ-Fe2O3) by chitosane and amine groups. One type of superparamagnetic nanoparticle was able to bind Genkwanin and Pratol with 34.49 % and 27.65 % recoveries, respectively. In future, the nanoparticles can serve for application and as a platform of biosensors.
Novel ZnO – Gd3+ materials were prepared by sol-gel method and photoluminescence properties of their films were studied for biomedical application. Biosensor’s properties ZnO – Gd3+ films were investigated under the action of rabbit immunoglobulin G (IgG) in concentrations 10-9, 10-11 and 10-13 M in solution depositing on the surface of film. The doping of ZnO film by Gd3+ in an amount from 1-12 mass.% with increments of 1 mass. % results in significant variations of fluorescence spectra ZnO – Gd3+ films. The ZnO substrate without of Gd3+ compounds allows detecting IgG in a concentration of 10-11 M by fluorescence spectroscopy method by registration in UV region (320-450 nm). By using ZnO – Gd3+ system it was obtained the increase the concentration limit of immunoglobulin (10-13M) detection. In the only case (the content of Gd3+ in ZnO film - 8 mass. %) was observed batochromic shift of fluorescence band maximum by 20 nm (from 364 to 385nm) when interacting with immunoglobulin regardless of the concentration of the last.
Here, we report the optimal conditions for the isolation of reduced glutathione (GSH) and oxidized glutathione (GSSG) from various types of matrix, such as blood, plasma or cells and their characterization using ion-exchange liquid chromatography with VIS detector. In our study, we aimed to synthesize paramagnetic microparticles able to isolate and immobilize GSH,GSSG from blood or plasma and thus preconcentrate it for subsequent analysis on ion-exchange liquid chromatography with VIS detector. We modified amberlite and Dowex by nanomaghemite (γ-Fe2O3), as the functional carriers providing perfect paramagnetic properties. Both the paramagnetic microparticles were able to bind GSH and GSSG. Our paramagnetic microparticles have potential to improve GSH and GSSG isolation and in future can serve for application as a platform of biosensors or delivery system.
Anodic aluminum oxide (AAO) is a self-organized matrix with honeycomb-like structure formed by сlose-packed arrays parallel cylindrical nanopores.
The structure of AAO allows the formation of oriented organic molecules, as well as highly organized molecular nanoclusters. The latter include J-aggregates of cyanine dyes with unique spectral-optical properties, such as narrower luminescence and absorption spectra in comparison with monomeric forms of dye.
The absorption and luminescence of pseudoisocyanine J-aggregates formed in structured cylindrical nanopores of the anodic aluminum oxide were studied by the VIS spectroscopy and the laser confocal microscopy.
The luminescence maximum of J-aggregates was observed at 578 nm upon excitation at 543 nm as well as at 405 nm. Non-resonant luminescence occurred due to resonance energy transfer from oxygen vacancy in alumina to molecular nanoclusters. This is also confirmed by time-resolved luminescence spectroscopy, which shows the increase of luminescence decay time of J-aggregates placed in alumina up to the luminescence time of the clean AAO in comparison with J-aggregates coated on glass substrate.
Such hybrid material can be the basis of advanced optical sensors for atoms and molecules, due to free access of the detected molecules to fluorescent molecular nanoclusters through the nanoporous structure. Owing to the high optical nonlinearity of the organized molecular clusters, it is possible to develop the optical signal multiplexers. On the basis of AAO activated with dye monomolecules, random lasing was realized, which suggests the possibility of obtaining it also with molecular nanoclusters.
Self combustion synthesis, a method of production of fine ceramic particles by burning suitable metallic precursors with organic fuel in a presence of an oxidizing agent, is an easy to use, high yield method, that, when mastered, can lead to production of significant amounts of nanoparticles with tuned properties and morphology. The method was used to prepare fine particles of iron oxide, cerium oxide, praseodymium oxide and various other lanthanide oxides with different organic fuels, including glycine, citric acid, ethylene glycol, urea and starch. As metallic precursors, nitrates organic complex compounds were used. In summary, all particles produced by self combustion synthesis form, apart from separated nanoparticles, slightly larger aglomerates with dimensions of up several micrometers. The nano-sized grains however still remain apparent. Further experiments were also made with electrospinning the precursors into nanofibers with carrier polymer prior to calcination, so those would preserve the morphology during the process. These experiments were performed with both direct current and alternating current electrospinning. Electron microscope pictures show, that by using nitrates as precursors, the resulting oxidic fibers retain a smooth surface, while the use of organic complex compounds yields highly porous structures, some of which retain the general fibrous structure, depending on the carrier polymer and rate of heating. A formation of porous structures was generally observed for most of the organic complexes and fuels.
Doped nano-ZnO is one of the most studied semiconductors, many investigations being focused on tailoring material properties for applications in spintronics, nano- and opto-electronics, by changing the nature and concentration of the dopant. Doping nanocrystals is still an experimental challenge and the progress in controlling and understanding the incorporation of dopants in nanocrystals is slow. Thermally-induced decomposition of doped precursors is an alternative efficient way to obtain doped nano-ZnO and thus we expected doping Zn(OH)2 to be a facile way of obtaining precursors for doped nano-ZnO. Yet, this was a surprisingly challenging task: although we followed the same procedure (coprecipitation) as for pure Zn(OH)2, the addition of even 1 ppm of Mn2+ turned the synthesis result into Mn-doped nano-ZnO. This is the first reported observation of synthesis redirection from Zn(OH)2 towards nano-ZnO by doping instead of by changing synthesis / post-synthesis parameters. This behavior is unique, pertaining only to Zn(OH)2. In order to understand these results, we performed a systematic study of the samples prepared without and with variable amounts of Mn2+ ions. We discuss here the results of XRD, TEM, and EPR investigations of the structure and morphology of the samples versus the Mn nominal concentration, and of the localization of the Mn2+ ions in the nano-ZnO samples.
ACKNOWLEDGEMENTS: Financial support from CNCS-UEFISCDI, Project PN-II-RU-TE-2014-4-0939 is gratefully acknowledged.
REFERENCES: D. Ghica, I.D. Vlaicu, M. Stefan, L.C. Nistor, S.V. Nistor, RSC Advances 6 (2016) 106732, and cited references.
The effect of negative differential resistance can be observed experimentally in some material systems based on polymers. These observation are explained usually to be due to the presence of certain carrier traps which can capture the carriers of the electric current. In the present theoretical work we are going to show that besides this carrier trapping origin of the negative differential resistance there can also be an intrinsic mechanism present, causing such an effect. Namely, instead of the traps, the electron-phonon interaction can cooperate with the tunneling of the charge carriers between their localized states and can provide the effect the negative differential resistance. This electron-phonon interaction is included in a non-perturbative way. The theory will be briefly summarized and explained.
We investigate the band properties of InAs/AlSb/GaSb (N- structure) and InAs/GaSb material based type II superlattice (T2SL) photodedectors. Superlattice empirical pseudopotential method (SEPM) is used to define band-structures such as band gap and heavy hole-light hole (hh-lh) splitting energies in the mid wavelength infrared range (MWIR) and long wavelength range (LWIR). The calculations are carried out the variation of AlSb/GaSb layer thickness for (InAs)10.5/(AlSb)x/(GaSb)9-x and the variation of InAs layer thickness for (InAs)x/(AlSb)3/(GaSb)6 T2SL structures. For the same band gap energy of 229meV (5.4m in wavelength), hh-lh splitting energy is calculated as 194meV for (InAs)7.5/(AlSb)3/(GaSb)6 structure comparing to (InAs)10.5/(GaSb)9 structure with hh-lh splitting energy of 91meV within the MWIR. Long wavelength performance of InAs/AlSb/GaSb structure shows superior electronic properties over standard InAs/GaSb T2SL structure with larger hh-lh splitting energy which is higher than the bandgap energy. The best result is obtained for (InAs)17/(AlSb)3/(GaSb)6 with the minimum band gap of 128meV with hh-lh splitting energy of 194meV which is important for suppressing Auger recombination process. This values are very promising for a photodetector design in the both MWIR and LWIR at high temperature applications.
Three novel organic sensitizers were molecularly designed and synthesized based on triphenylamine (TPA), as the core donor (DTPA), linked to one, two or three carbazole (DCarb) moieties with different number of anchoring groups (AG) to generate: DTPA-π-DCarb-A (DE1), DTPA(π-DCarb-A)2 (DE-2) and DTPA(π-DCarb-A)3 (DE-3). The primary goal of this study was to investigate the influence of bridging different number of DCarb and AG, through π-spacer, with TPA on the photovoltaic performance in DSSCs. The molar extinction coefficient increased with increasing the number of DCarb and A. DE-3 showed the greatest light harvesting in solution and when anchored onto TiO2. Hence, the increase in the number of DCarb and AG led to better light harvesting and stronger electronic coupling with TiO2, which reflected positively on the photovoltaic properties, and this is the first systematic study of its kind involving TPA-π-carbazole motif. DE-3 achieved the best efficiency of 5.44% and showed IPCE of 74% at 470 nm. The Voc increased with increasing the number of anchoring groups. Equilibrium molecular geometries and frontier molecular orbitals studied by DFT and TD-DFT calculations were in excellent agreement with experiments, which showed enhanced electronic coupling with TiO2 and photovoltaic performance as the number of anchoring groups increased.
Si-based nano- and submicron-sized carriers have gained a substantial and deserved place among another perspective nanotherapeutic materials due to the wide range of advantages: tunable particle size and morphology, uniform and tunable pore size, high surface area and large pore volume etc.
Although various synthetic strategies to produce Silica particles (SP) have been developed, they are complicated and time consuming.
To overcome these drawbacks, basic sol-gel method based on Stober method that utilizes a reaction of simultaneous hydrolysis and condensation of silica source and organotrialkoxysilanes at the high alkaline pH was implemented through three different approaches:
1. Template-based sol-gel method with quaternary ammonium salts as templates.
2. Template-free sol-gel method.
3. Template-based sol-gel method with small organic amines, N- heterocyclic compounds or secondary, tertiary alkanolamines and NH4OH as alkaline catalysts.
SP were prepared through a template sol-gel approach with cationic surfactants of different length of alkyl chains and alkaline catalysts that allowed to obtain materials with a wide range of size (25-1000 nm) and variable textural characteristics.
ACKNOWLEDGEMENTS: This work was supported by Ministry of Education, Youth and Sports of the Czech Republic (grant No. LO1504), Science Foundation of the Czech Republic (grant No. 17-05318S) and Internal Grant of the Tomas Bata University in Zlin (grant No. IGA/CPS/2017/005.