Seznam abstraktů 2019: SEKCE B - PRŮMYSLOVÉ A ENVIROMENTÁLNÍ APLIKACE NANOMATERIÁLŮ

The self-organized anodic 1D TiO2 nanotubular layers (TNTs) have attracted considerable scientific and technological interest over the past two decades, all motivated by a great performance in the range of applications including photo-catalysis, solar cells, hydrogen generation and biomedical uses. These nanotubes possess unique features (tunable dimensionality, structural flexibility, unidirectional electron transport), chemical and mechanical stability and biocompatibility.
One of their major application targets has been as scaffolds or templates for deposition of secondary materials towards new energy applications. Unlike randomly ordered mesoporous TiO2 support, TNTs offer the advantage of directed charge transport and controlled phase separation between donor and acceptor materials, which is useful in various types of solar cells (dye-sensitized, perovskite solar cells, etc.) and thus they contribute to promising nanoscale solar hybrid technologies.
Numerous techniques were utilized for modification of TNTs for this purpose, such as for example wet chemical and electrochemical routes or physical deposition techniques. However, recently it has been shown that the utilization of Atomic Layer Deposition (ALD) can extend the functional range of TNTs by homogenous coatings or decoration of tubes by secondary materials. ALD is the only technique of choice to coat in particular high-aspect ratio TNTs. Overall, the deposited coatings influence strongly photo-electrochemical properties of TNTs.
The presentation will be focus in detail on TNTs of various aspect ratios coated by suitable chromophores using ALD. Experimental details and some very recent photo-electrochemical and structural characterization of a new type of heterostructured photo-chemical cells will be presented and discussed.

Li-rich oxides of different phase compositions xLi2MnO3·(1-x)LiMO2 are synthesized by coprecipitation of mixed transition metal carbonates followed by solid-state reaction with lithium hydroxide. X-ray powder diffraction, scanning electron microscopy, and magnetic studies are used to characterize the pristine structure of the oxides with different compositions. The materials are tested as positive electrode in lithium half-cells. Galvanostatic charge-discharge measurements are performed at different current densities. The lithium-ion diffusion coefficients (DLi+) are estimated from the cyclic voltammetry experiments and found to reach maximum values for composition at x=0.35 having the best electrochemical characteristics.

Lithium-rich oxides with different compositions are synthesized by coprecipitation method and tested as cathode materials for lithium-ion batteries (LIBs). The paper presents research into the degradation processes: capacity and voltage fade during cycling life. The lithium mobility is known to make one of the major contributions to LIBs lifetime. Therefore, galvanostatic intermittent titration (GITT) is provided to estimate lithium-ion diffusion coefficients (DLi+). We also calculate ohmic and polarization resistance values. There is shown the influence of the structural transformation of lithium-rich oxides on their kinetic parameters. We make an assumption about the optimal composition of such cathode materials for good electrochemical properties.

Expanding of the titanosilicate zeolite catalyst usage means dealing with larger molecules, which; however, penetrate with difficulties into the zeolite micropores. Therefore it is important to develop catalysts with improved mass transport properties (layered and hierarchical materials), which will have good accessibility of the active sites even for sterically demanding molecules.
In this contribution, we report characterization and catalytic properties of MFI titanosilicate nanosponge (nanosponge TS-1, nsTS-1). The catalytic properties of the material are compared with conventional TS-1 and silica-titania pillared TS-1 (TS-1-TiPi) in epoxidation of cyclooctene, norbornene, linalool and citronelol being representatives of different sterically demanding molecules. In addition, a deeper comparison with other catalysts for selective oxidation of bulky substrates will be provided. When oxidizing linalool, the reaction was almost completed in less than 30 min over nsTS-1 while using TS-1-TiPi it took 5 hours to achieve the same conversion. Selectivity of the reaction was the same in both cases (52% for the furanoid isomer of linalool oxide).
The nsTS-1 combines the properties of crystalline zeolites in terms of active site character and properties of mesoporous molecular sieves in terms of mass transport properties. At the same time, nsTS-1 is structurally uniform material in contrast to, in principle composite, catalysts like TS-1-TiPi (having crystalline layers and amorphous pillars). This is expected to be an advantage in catalyst preparation as well as stability under process conditions.

Solid solutions La0.5Ca0.5Mn1-xFexO3 synthesized by the method of polymer-salt compositions at a temperature of 900 °C with the perovskite structure were tested in the methane oxidation reaction. It was shown that at 600 °C, complete conversion of methane occurs for all compositions, however, the nature of the dependence of the degree of conversion for lower temperatures is not linear and depends on the chemical composition. The formation of planar defects in the direction of crystallographic planes (101) in the perovskite structure at the stage of the synthesis of solid solutions and the appearance of nanoparticles of Ca-Mn oxides on the surface of perovskite after participation after reaction were shown by the HRTEM method.

The world population is going to explode from the current levels of 7.3 billion to 8.5 billion in 2030 and further to 9.7 billion in 2050. Metro cities are becoming Mega cities in terms of population density. How are we going to meet the ever-rising energy demands of our future Mega cities, providing wealthy conditions for living while keeping the necessary investment realizable?
Today’s technologies for renewable energy generation just simply do not provide solutions for this challenge.
There is no power more expensive than the one missing.
Many governments already understood that and are pushing to bring renewables into the cities by stricter enforcement of Green building codes applying a “carrot & stick” mechanism (mostly based on energy certificates like LEED or GRIHA) to integrate renewables and energy efficiency in buildings.
OPV technology perfectly suits the building market as it provides solutions that can be integrated in to existing construction materials while adding to the aesthetic design of the building. Among other materials, OPV can be integrated in laminated façade glass using standard glass or Polycarbonate lamination processes and applied to membranes. It is a semitransparent, a look-through technology, which furthermore reflects NIR heat waves and absorbs UV. Last but not least it is no final product but a designable (by project) piece of inlay that will - for the first time ever - convince the architects involved to use PV in the façade

Currently, photocatalysts based on nano-sized titanium oxide powders are the most widely used. Along with TiO2 nanopowders, anodic titanium oxide nanotubes (TiO2 NTs) is considered as a promising material for catalytic photodegradation of organic pollutants, photoreduction of CO2 and water decomposition. This is due to the fact that vertically oriented massive TiO2 nanotubes, obtained on Ti substrates by electrochemical anodizing, have a large specific surface weight, as well as the possibility of precise control of the morphology and geometrical parameters by controlling the conditions of the anodizing process. However, it is known that the band gap of the TiO2 is 3.2 eV, requires ultraviolet radiation for photocatalytic activation. Since UV radiation accounts for a small part (5%) of the solar spectrum compared to visible light (52%) and infrared light (43%), any shift in the optical response of the TiO2 towards the longer wavelength region allows for higher photocatalytic activity.
This work is devoted to increasing the photocatalytic activity TiO2 NTs based materials in the visible wavelength range by optimizing geometry, phase and elemental composition, and electrophysical properties.
To determine the geometric (effective areas) and size parameters, phase states, crystal structures, high-resolution SEM, TEM, XRD and Raman spectroscopy were used. To determine the electrophysical and photoelectrochemical properties electrochemical impedance spectroscopy, photopotential spectroscopy and photocurrent methods were applied. The efficiency of photocatalytic activity were measured by methylene blue water solution discoloration under UV and visible light source. ACKNOWLEDGEMENTS: This work was supported by RFBR grant № 18-29-23038 mk.

Carbohydrate polymers isolated from tree exudates are a class of bio-based resources, which are gaining prominent research interest in many zones such as food, pharmaceutical, environmental, energy and biomedical [1]. In this work, we have explored to utilize non-edible and bio-wastes gums of types II and III sourced from Kondagogu and Karaya trees as an inexpensive viable material for energy and environmental applications. We have synthesized highly porous carbon structures from the gum wastes via high temperature carbonization and characterized by using spectroscopic and microscopic techniques. The produced micro/mesoporous carbon exhibits substantially high surface area, reusability and high ion transport properties. The produced carbon structures could advantage not only to produce electricity but also showed their efficiency to remove organic dye from contaminated water. Significantly, our study institutes an initial breakthrough in building up a ‘green’ and sustainable solution to overcome the energy deficiency and water purification in the society, by exploiting gum wastes.
REFERENCES: [1] Padil, V. V. T., Wacławek, S., Černík, M. & Varma, R. S. Tree gum-based renewable materials: Sustainable applications in nanotechnology, biomedical and environmental fields. Biotechnol. Adv. 36, 1984-2016 393 (2018).

Organic electrochemical transistors (OECTs) gathered great attention nowadays due to the unique properties that make them ideally suited for bioelectronics applications. The OECTs are made from organic mixed conductors that support electronic charge as well as ionic transport and as such are able to convert the ionic signaling in biological systems to electrical signal. These organic conductors are soft and therefore suitable for interaction with living cells and tissues, and due to large capacitance of the electrolyte double layers and the ability of ions to penetrate into organic semiconductors allow operating the OECTs at low voltages (typically up to 1 V) while providing high signal amplification. The amplification is then associated with high sensitivity in (bio)sensors. As a figure of merit for gain evaluation, a transconductance is used and compared all along the literature for various devices and materials.
In this contribution we discuss the ways to maximize the transconductance including utilization of nanomaterials allowing to reach high volumetric capacity. It is proposed herein that proper device design accounting for parasitic resistance is among the main factors contributing to maximization of the transconductance and therefore the sensitivity of the OECT for given material. Indeed, the measured transconductance 108 mS for the optimized OECTs reported here doubles the highest achieved values so far.
ACKNOWLEDGEMENTS: The work was supported by Czech Science Agency via project No. GA17-24707S.

Soft nanocomposite nanomaterials can be based either on polymer network or on self-assembled network of wormlike surfactant micelles (WLMs). To provide additional functionality to the matrix the nanomaterial can contain delivery vehicle components, for instance, nanoclay tactoids, which make them very promising for drug delivery and tissue engineering applications. Injectable systems represent an evergrowing class of nanomaterials possessing a unique combination of physical and chemical properties. Such materials, for instance, hydrogels can be used as control delivery systems, since they can be delivered in a minimally invasive manner, because their final form and shape are defined by the space, into which they are injected. The influence of organoclay on the mechanical properties of mixed WLMs of surfactants was studied by rheometry. The present study is devoted to soft nanocomposite based on network of WLMs composed of biocompatible zwitterionic and anionic surfactants with embedded plate-like bentonite nanoclay particles. It is shown that nanoparticles enhance significantly the rheological properties of WLM hydrogel acting as physical cross-links between micellar chains. It was explained by the formation of micelle-nanoparticle junctions as a result of binding of the WLMs end-caps to the layer of surfactant adsorbed on the particle surface. The studied network possesses gel-like properties. In particular, its rheological properties demonstrated plateau modulus, low values of loss factor. At the same time, under high deformation, the micellar chains was disrupted, which induced a much more pronounced drop of viscosity than the disruption of physical cross-links in polymer gels. The disrupted micellar chains were completely recovered due to restoration of non-covalent bonds between surfactant molecules within the micelle. It was demonstrated that the prepared nanocomposite hydrogels possess promising properties for injection applications.
ACKNOWLEDGEMENTS: the financial support of Russian Science Foundation (project №17-13-01535).