Materials Engineering

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Research Topic Summary.

The project aims at creating a novel hybrid material able to change of color at will. The key element of this novel technology is based on the combination of two phenomena observed in the nature and transferable to material science: plasmonic and structural colors. The developed functional nanomaterial will be composed of colloidal metallic nanoparticles (NPs) that will be properly synthesized and assembled into 3D printing polymer (3DP) to ensure a variety of plasmonic colors under thermal and mechanical stresses. By changing height and width of a polymer film and/or the size of nanostructures through the shape memory effect, the distance between the nanoparticles will be modified inducing a color change in the composite material. To enhance the color palette of this stimuli-responsive nanocomposite, its surface will be structured with diverse diffractive nano & micropatterns. As result, combining the color emission of the nanoparticles with the structural colors will allow enhancing specific wavelengths and the palette of reachable colors. The specificity thermo-mechanical properties of the 3DP will ensure the reversibility of color by properly controlling the reassembly of the nanoparticles inside and on the surface of the material. The project has the ambition to address four main innovative issues: i- Developing new routes to fabricate a stress-responsive colorimetric polymeric material by finely controlling assembly of colloidal metallic NPs within a 3DP (from random to ordered assembly), ii- Modification of the multilayer reflector geometry of the hybrid material to generate different color- changes: combining the colour emission of the nanoparticles with the structural colours of the 3DP will allow enhancing the potential reachable wavelengths and avoiding bleaching effect of colour materials. iii- Development of a rapid active colour change in the material using bio-inspired photonic material and plasmonic NPs properties Activating the reversibility of the colour change material

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Research Topic Summary.

Recent advances in organic optoelectronics, particularly in efficient organic light-emitting devices (OLEDs), have called for new electro-active organic materials as well as for new device technologies. Small OLED-based displays already generate hundreds of millions of dollars. Larger OLED displays will penetrate the television market in the not-too-distant future. Nowadays white displays play important role in lightening. Further advances of these devices substantially rely on development and studying of high-performance organic charge-transport and emitting materials, theoretical understanding of charge and energy transport in the organic systems and their well-balanced application in OLED devices. Despite their recent progress, OLEDs are still dealing with the issues of efficient and balanced carrier injection and transportation because of large difference of barrier heights and low carrier mobility. Unbalanced hole and electron current in OLEDs makes the recombination zone narrower, thereby leading to less efficiency with high roll-off and shorter lifetime. Various approaches for efficient hole injection have been also adopted in the past, however, hole transport phenomena is still dealing with the critical issues like low hole mobility, high injection barrier between two highest occupied molecular orbital levels, and morphological and thermal instability caused by Joule heating. Hence, hole-transporting materials possessing low ionization potential for efficient hole injection, high hole mobility, thermal durability and morphological stability with high glass transition temperature are still demanding. Efficiency of OLED devices would be increased several times by using the materials in multilayer structures. Objective of the project- synthesis, characterization and application in OLED devices of new structure electroactive materials having efficient charge transporting properties in order to develop devices having higher efficiencies than those of OLEDs using commercially available charge transporting derivatives.

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Research Topic Summary.

It is very important to use various natural wastes for the production of new functional materials. The manufacturing of amber jewelry generates large amounts of waste that could be used in textile finishing to give it functional antibacterial properties. It is planned to carry out investigations by inserting amber dust into the structure of the yarn and processing textile materials with it.

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Research Topic Summary.

Spatial knitted structures expand functionality of textiles in very high level, it enables to obtain the final dimensional shape. It significantly reduces amount of industrial waste as well as demand of raw materials (fibres and yarns). There is possibility to combine different fibres, textile and non-textile yarns, and different patterns in one spatial and multilayer knitted structure. However, such multiplex structure makes processes of modelling and designing more difficult. There are still many unsolved problems and questions in designing of new knitted structures and prediction of their properties. The main aim will be development of the method for spatial knitted structures modelling and prediction of their properties as well as development and investigation of spatial knitted structures with specific properties.

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Research Topic Summary.

Research topic focusses on the development of multifunction biopolymers based organic or organic-inorganic compositions possessing antimicrobial, antioxidant, healing, protective or other properties and correlation of properties and behavior in order to get the maximum benefit from the systems developed. The main tools for achieving this are theoretical and experimental research, and imitation and modeling of systems behavior.

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Research Topic Summary.

The mechanism of bacterial adhesion to solid surfaces is a complex process affected by multiple factors. The most important property of bacterial adhesion mechanism is influenced by physicochemical interaction of the bacterial cells. The bacterial adhesion is determined by surface topography and roughness, free surface energy, including Van der Valse and electrostatic forces or acid-alkaline interactions, the potential arising in the phase boundary, hydrophobicity and surface charge. Surface derivatives, which are much smaller than bacterial cells, have been found to inhibit binding, reducing the interaction between bacterial cells and solids. The use of nanoparticles (metal and metal oxide) as antibacterial surfaces is a viable way. Most metallic or metal oxide nanoparticles (Ag, Fe3O4, TiO2, CuO, ZnO, etc.) have bactericidal properties through the generation of reactive oxygen species, although some of them are effective due to nanostructures and surface potential. Nano-particles formed on ceramic surfaces can disrupt the integrity of the bacterial cell membrane and its potential and activate the production of oxygen free radicals acting as nanocatalysts. The project will investigate: a) the formation of thin ceramic films by physical vapour deposition methods, selecting optimal forming technologies; b) the influence of technological parameters on the catalytic and antibacterial properties of the thin films; c) physicochemical investigation of the formed thin films. The aim of the project is to investigate the physical, chemical, and other characteristics of antimicrobial thin films and, on the basis of the research, cause the practical use of such systems.

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Research Topic Summary.

Exciplex-forming systems based on solid-state mixture of different organic luminophores have big potential for usage in many high-tech applications including optoelectronics and sensing. Nowadays, exciplex-forming emitters are widely used in organic light-emitting devices. However, the usage of exciplex emission for optical sensors is very limited. Aiming to demonstrate new perspectives of exciplex emission, the topic of this PhD study is related to development of state-of-art exciplex-forming emitters with desired thermally activated delayed fluorescence and/or long-living pristine luminescence for novel devices of organic electronics.

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Research Topic Summary.

Despite ZnO is widely used in various applications such as photocatalysts, photoelectrodes, an bacterial agents, gas sensors, supercapacitors and other electronic devices further search for new methods of producion enabling performance of the material due to geometrical con?guration, oxygen vacancy concentration etc. appears important ?eld. E.g. semiconducting properties ZnO nanowires (NW) show critical change in electrical and optical proper es that are observed for diameters below 30 nm. This work will further develope non catalytic thermal ZnO NW synthesis methods, allowing to obtain nanowires with diameters 5-30 nm, which will aim to form a new type of multifunctional coatings. During the project, multivariate approach will be used for investigation of interaction among di?erent ZnO NW properties. The multifunctional coatings, which will be developed in this work will constitute a new class of materials with wide application possibilities. Prepared in a layered structure, each layer can be tailored with separate functionality and deposited on virtually any surface. ZnO NW based multifunctional materials will be textile-compatible, lightweight, and stretchable therefore will open a new avenue for application in wearables, electronic textiles, and other devices for the Internet of Things. Applications are numerous, however 2 state-of-the-art applications will be developed: 1) Anti-reflecting coating, which will increase the solar cell efficiency, lower the cleaning costs and can be printed onto any surface: glass, Si, polymer, rubber and also on solar cells, which are already operational. 2) Sensors, which will be activated by light, sensitive and selective to gases, stretchable, and because of low power can be used on wireless platforms. These results are important at the international level, as they will open new horizons for the application of multifunctional coatings, and will be used in the developing of state-of-the art devices.

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Research Topic Summary.

In recent years, the development of nanotechnologies and understanding of the plasmonic properties of nanomaterials has opened new paths for exploitation of surface enhanced Raman scattering (SERS) sensing. SERS is known as extremely sensitive analytical tool that can be applied in variety of areas: electrochemistry, analytical chemistry, chemical physics, solid state physics, biophysics and in medicine. The crucial point in SERS is usage of noble metal nanoparticles that can enhance the extremely low signal of Raman scattering up to 108 times. Signal enhancement depends on the chemical composition of nanoparticles, shape and geometry of nanoparticles. The self-organized ensembles of nanoparticles that has a predefined order on the surface should allow to use such structures with the different excitation wavelengths and obtain reproducible SERS results. This is obtained through the effect of surface lattice resonance when the coupling distance between nanoparticles increases and becomes comparable to the resonance wavelength (far field contribution).

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Research Topic Summary.

To address the problem of overconsumption of energy and natural resources, relevant research focused on high-value-added products with exceptional functional properties and recycling potential. Modern challenges of textile science are related to interdisciplinary research, integrating traditional materials science with the application of biotechnology, principles of microelectronics engineering and so on. Research is concerned with materials of different properties that are integrated into systems to produce adaptive functional products. The goal of the research is to develop functional flexible systems based on textiles with good wearable properties and recycling possibilities.

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Research Topic Summary.

Functional textile properties (as antimicrobial, antistatic, flame retardance, oil, water repellent, smell elimination) are provided during materials manufacture process or during finishing. Textile materials (yarns, knitted, woven, nonwoven materials) are widely used in medical industry: cloths, surgical yarns, wound dressing, drug delivery systems, scaffolds in tissue engineering, artificial blood vessels, hernia mesh and etc. During research will be created and investigated new kind of medical functional textile materials.

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Research Topic Summary.

The European Commission, representing the interests of the EU, strategy is focused on a five ambitious objectives: employment, innovation, education, social inclusion and climate/energy. Great attention is paid to the search for alternative energy sources, energy storage and efficient energy utilization problem solutions. For this reason, the supercapacitor research as well as their applications in hybrid technologies where part of energy is stored and transferred via their use is rapidly expanding. In order to reduce the production costs and geometrical dimension of devices, the scientific community is constantly searching for novel and perspective materials as well as their development technologies. Graphene is very high strength, transparent, high electrical conductivity carbonaceous material. Unfortunately, the technological production costs and capacity far exceeds the activated carbon used in modern supercapacitors. This is due to the fact that currently used graphene production methods (mechanical exfoliation, epitaxial growth, chemical vapor deposition) are inappropriate for large-scale graphene extraction or require complex technological processes which also limit the integration of graphene in today's supercapacitor market. Currently, graphene oxide has gained a significant scientific community interest as a potential candidate for mass production of graphene. Generally, it is one or several layers two-dimensional atomic crystal material composed of the condenced benzene rings which are decorated with hydroxide groups. Graphite oxide can be effectively produced using well known Hummers method. Graphene oxide then can be obtained from graphite oxide via ultrasonic exfoliation method. Graphene oxide is hydrophilic which allows to form stable water dispersions. It is easy to manipulate with these dispersions as well as to obtain graphene after reduction of graphene oxide formed layers. However, the use of carbonaceous materials in supercapacitors has the main drawback - the charges physically stored on the surfaces of these materials in porous electrode layers are limited. Metal oxides due to their unique physical and chemical properties are considered very perspective materials to be used in new generation supercapacitors. These electrochemically active materials used in supercapacitor electrodes participate in fast and reversible faradaic reactions and can yield significantly higher specific capacitance and energy density. Highest theoretical performances can be reached with a series of metal oxides: RuO2, MnO2, NiO, Co3O4, V2O5, CuO and Fe3O4. The main factors affecting the performance of metal oxide-based electrodes include their crystallinity, crystal structure, specific surface area, pore size, morphology and electric conductivity. The later has a major impact on the supercapacitor performance where metal oxide-based electrodes are used. Unfortunately, the electric conductivity of metal oxide materials is generally poor which largely limits ion and electron transfer. Commonly, the electric conductivity of metal oxide-based electrodes is increased employing physical vapor deposition techniques – thermal evaporation, magnetron sputtering etc., which allows to deposit thin conductive layer on the surface of metal oxide. Specialized equipment is required to perform this technological step – not suitable for mass production of metal oxide-based electrodes, also limiting the integration of these materials into the today’s supercapacitor market. The heterogeneous system of reduced graphene oxide and metal oxide would effectively solve this problem. Research work will be carried out in the suggested dissertation topic as well as new knowledge and scientific expertise will be acquired about the structure and properties of nanostructured hybrid composites modified with reduced graphene oxide. Synthesis of graphene oxide, formation of layers, evaluation of laser exposure influence on the structure and properties will be performed as well as metal oxide hydration and nanostructurization followed by formation of graphene oxide-metal oxide films. Laser reduction method of graphene oxide will be performed to obtain nanostructured hybrid composites modified with graphene. Their chemical composition, surface morphology, structural and electrical properties will be investigated. It is expected that such a composite could be effectively used as a new generation supercapacitor electrode material.

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Research Topic Summary.

While mankind is facing new waves of the COVID-19 pandemics and the global spread of antibiotic-resistant micro-organisms new effective measures to combat the spread are necessary. It is well known that metal oxide nanomaterials and nanocomposite thin films are exhibiting antibacterial and antiviral properties. It is anticipated that exploiting a combination of tailored elemental composition and ultrashort laser microstructured materials, after exposure to thermal treatment under appropriate atmosphere, elaborated nanosurfaces will be developed that will potentially exhibit expressed anti-viral / bacterial properties. During the doctoral studies, it is foreseen to investigate the influence of the femtosecond laser effect on the morphology, elemental structure, and finally the antiviral and antibacterial properties of the nanostructures formed after oxidation at elevated temperatures. This topic is closely related to the project “Anti-viral filter with metal and metal oxide nanostructures (AntiVirus-21)” carried out by the research group in collaboration with the researchers from the Lithuanian University of Health Sciences.

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Research Topic Summary.

Graphene is a 2D nanocarbon material, carbon atomic hexagons monolayer. It is at the top of the significant interest due to the giant electron and hole mobility, charge carrier multiplication, flexibility, optical transparency, chemical inertness and other outstanding properties. One of the possible applications of the graphene is use of the graphene in Schottky contacts instead of the metal. Due to the very high mobilities the graphene can be used as a channel layer in field effect transistors and transistor based biosensors. Till now graphene was usually synthesized by chemical vapor deposition of the graphene on catalytic Cu, Ni, Co foils. Afterward, the long process of the graphene transfer onto the targeted semiconductor or dielectric substrates was used. It is a complex and time consuming procedure. Control of the graphene/semiconductor contact and graphene nanolayer properties are complicated in such a case. In present study graphene will be directly synthesized on the semiconductor surface by plasma assisted processes on semiconducting and dielectric substrates. Effects of the graphene structure on characteristics of the sensors will be studied. The relation between properties of the synthesized graphene layer and characteristics of the graphene-based sensors will be studied.

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Research Topic Summary.

The use of industrial polymeric waste in the development of new functional materials is a promising area for the development of sustainable technologies. One way to give desirable properties for purposive functional materials is to chemically modify their surface. Secondary raw materials are already mixtures, which are hampered by contamination with residues of additives required for the properties of the former product. The aim of the research is to search for new possibilities to use industrial polymer waste (plastic, textile) in the development of new functional materials.

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Research Topic Summary.

In this project, new, effective and inexpensive hole-transporting materials with ionization potentials below 5.2 eV will be synthesized. The compounds will be designed using planar electronically active moieties such as carbazole, fluorene, xanthone, thiazolothiazole etc. which will ensure high hole-drift mobilities. Photophysical, thermal, electrochemical, charge-transporting properties of the synthesized compounds will be studied. The obtained hole-transporting compounds will be tested in perovskite solar cells.

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Research Topic Summary.

The speedily growing consumer optoelectronic goods industry, favorable government initiatives, increasing application areas, and financially stronger customers spending more on optoelectronic devices are the factors boosting the global organic electronics market. The global organic optoelectronics industry generated $46.1 billion in 2019, and is expected to reach $159.1 billion by 2027, growing at a CAGR (Compound Annual Growth Rate) of 21.0% from 2020 to 2027. Organic optoelectronics covers special applications in the fields of field-effect transistors (FETs), light-emitting diodes (LEDs), and solar cells that will open the frame for a new type of devices. Organic LEDs (OLEDs) are among the latest and most advanced display technologies. OLED displays are used in mobile phones, laptops, and most prominently in televisions and other display panel electronic devices. The OLED display offers various advantages to users which are enhanced image quality in terms of better contrast, higher brightness, fuller viewing angle, a wider color range, much faster refresh rates, and lower power consumption. The advantages of organic materials have also allowed the displays to be ultrathin, flexible, foldable, and transparent. However, organic optoelectronics have few disadvantages, one of them is the degradation of organic components over time, which reduces the functional efficiency of the devises. For instance, it is observed that OLED TVs after a period tend to reduce the quality of display output, in terms of brightness and vibrant colors. Materials with a certain combination of features can allow to overcome these problems and realize highly efficient and stable OLEDs.