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A huge focus worldwide is devoted to the production of novel tailored materials to improve electronic devices through sustainable processes. Nowadays, as reagents for the production of metal oxide–carbon composites that could be used in catalysis, sensing, and electrochemical devices, biopolymers are leading candidates. Various TiO2- based nanostructured materials fabricated using different cellulose templates such as nano and microcellulose fibres have been reported previously in the literature. Cellulose, as the most abundant renewable biopolymer, was used as well in our research to control the morphology, porosity, and therefore the properties of the derived composite samples at the nanoscale. Moreover, the tin(IV) oxide has a similar bandgap as already well-studied TiO2, while has not yet reached as wide applicability. In this work, to broaden the research in the field of SnO2 nanostructures, we investigated the properties of cellulose-immobilised SnO2 samples. Additionally, the influence of post-reaction treatment of the samples was investigated. This work focuses on the course of non-hydrolytic sol-gel freeze-drying synthesis in combination with the reductive mineralization of cellulose. Samples' post-treatment was carried out under both inert and atmospheric conditions, at three chosen temperatures (60 °C, 700 °C, and 800 °C). Thin films of the resulting composite samples were prepared and characterised using grazing incidence X-ray diffraction (GIXRD), which overall showed the degree of chemical homogeneity of studied composites. Morphologic and surface geometries were studied by scanning electron microscopy (SEM). Finally, the photocatalytic activity was investigated by photocatalytic degradation with a model micropollutant with previously calculated bandgap values from diffuse reflectance spectroscopy (DRS) measurements.

Nowadays, the need for clean energy solutions is rapidly growing. Systems of high interest include versatile nanomaterials capable of energy conversions and storage, whether as photocatalysts, battery materials or transport layers in photovoltaic devices. Such materials need to satisfy multiple criteria, depending on their application, while the method of their synthesis needs to be reproducible, low-cost, green and scalable. Here we report on a solid state synthesis of titanium oxide nanoparticles through spark plasma discharge. We obtained primary particles of sizes as low as 10 nm with a mixed phase composition. Microscopy revealed multiple stages of assembly, stemming from coalescence and aggregation to agglomeration of web like structures. All of these result point out to a highly nanoporous material with an increased number of oxygen defects introduced into the structure which will hopefully serve as a superior electron transporting layer for flexible organic solar cells.

This invited workshop talk delves into the effective conductivity of geopolymer-graphite composites using mathematical modeling techniques. To simulate the percolation threshold, a particle- based Monte Carlo method is employed to generate virtual composite microstructures and simulate percolation phenomena. The effective medium model is then utilized to model the conductivity of the composite. The percolation and effective conductivity of a multi-phase mixture is closely related to the physicochemical characteristics of the mixed phases, such as the porosity and particle size distribution of individual components (metakaolin, graphite, and air) embedded in the geopolymer gel matrix. To investigate the effect of particle size distribution of the mixture phase on the percolation threshold, Hymostruc is used to generate a three-dimensional model of a mixture, which is then analyzed for connectivity of the conductive (graphite) filler using Matlab. The results indicate that the percolation threshold of a three-phase mixture of metakaolin, graphite, and pore is affected by the addition of segregated third phase, namely metakaolin or air (particle). To study the effect of metakaolin and porosity on the percolation threshold, the concept of effective volume fraction is introduced. This is defined as the ratio of the volume fraction of graphite to the total solid volume after excluding the segregated volume. Finally, a simple analytical effective medium model proposed by Bruggeman is used to simulate the variation pattern of conductivity of the mixture with increasing graphite content, in combination with the percolation threshold of the system simulated by Monte Carlo method. The simulation results show good agreement with the measurement results

Zinc oxide (ZnO) and titanium oxide (TiO2) are two widely studied metal oxide semiconductors due to their unique optical, electronic, and catalytic properties. These materials have attracted considerable interest in the development of advanced electronic device like sensors, solar cells, and photocatalysts, among other applications. Nanostructured thin films of ZnO and TiO2, with thicknesses ranging from a few to several hundred nanometres, have received increasing attention in recent years due to their exceptional properties arising from the quantum confinement and large surface area-to-volume ratio. These properties include enhanced optical absorption, improved charge transport, and increased reactivity, making them suitable for the above-mentioned various applications. In this work several chemical and physical methods of synthesis were utilized to produce nanostructured thin films, which were thoroughly characterized by SEM, STEM, TEM, AFM, GIXRD, UV- Vis, DLTS and ss-IS, and used in advanced configurations of thin-film based solar cells (perovskite) and as immobilized photocatalysts.

Zinc oxide is a well know semiconducting metal oxide with a high electron mobility, wide band gap and large exciton binding energy. Due to its beneficial properties and the vast array of physical and chemical deposition methods that can be used for deriving various nanostructured forms it has been applied in solar cells, sensors, photocatalysis, electronics, etc. Here we prepared ZnO in the form of thin film with vertically ordered nanorods by a simple chemical method on different substrates firstly with the aim to elucidate the effect of synthesis and deposition conditions on their mechanical properties. Secondly, the influence of the type of substrate on their mechanical properties was investigated. Shedding more light on both aspects is crucial for further applications. To establish that, we used advanced microscopy (SEM) in combination with in situ mechanical testing in combination with nanoindenation. Samples were additionally characterized by XRD, AFM, KPFM and bending tests. Sample preparation was aided by use of focused ion dual beam microscope equipped with a femtosecond laser system. Obtained results were used to quantify the mechanical properties and failures such as cracks, which will enable us to optimize the synthesis and mitigate such events for further applications in flexible solar cells or gas sensors. Zinc oxide is a well know semiconducting metal oxide with a high electron mobility, wide band gap and large exciton binding energy. Due to its beneficial properties and the vast array of physical and chemical deposition methods that can be used for deriving various nanostructured forms it has been applied in solar cells, sensors, photocatalysis, electronics, etc. Here we prepared ZnO in the form of thin film with vertically ordered nanorods by a simple chemical method on different substrates firstly with the aim to elucidate the effect of synthesis and deposition conditions on their mechanical properties. Secondly, the influence of the type of substrate on their mechanical properties was investigated. Shedding more light on both aspects is crucial for further applications. To establish that, we used advanced microscopy (SEM) in combination with in situ mechanical testing in combination with nanoindenation. Samples were additionally characterized by XRD, AFM, KPFM and bending tests. Sample preparation was aided by use of focused ion dual beam microscope equipped with a femtosecond laser system. Obtained results were used to quantify the mechanical properties and failures such as cracks, which will enable us to optimize the synthesis and mitigate such events for further applications in flexible solar cells or gas sensors.

Kaolinite is a 1:1 clay mineral with the chemical formula Al2O3·2SiO2·2H2O that has a dioctahedral layer structure without charge. Each layer consists of one tetrahedral layer of silicon dioxide and one octahedral layer of aluminum oxide. The high proportion of SiO2 and Al2O3 makes kaolinite an excellent source of aluminosilicates, which is why it is one of the most commonly used natural precursors in the synthesis of geopolymers and zeolites. However, highly ordered crystalline systems are more resistant to alkaline attack than amorphous systems. Therefore, kaolin as a crystalline precursor is often used in its amorphous form - metakaolin, which requires temperature treatment, usually in the range between 600 and 800 °C. In recent years, mechanochemistry has begun to be studied as an alternative to the high-temperature processing (calcining) of kaolin into metakaolin. Due to the reduction of solvent consumption, energy, and faster chemical reactions, mechanochemistry is considered a greener approach in the synthesis of aluminosilicate materials such as geopolymers and zeolites. In this work, the possibility of mechanochemical synthesis of geopolymer-zeolite composite was investigated. The composite synthesis parameters were approximately set to a molar ratio of 1 mol Na2O: 1 mol Al2O3: 2.5 mol SiO2, while the amount of water and the curing temperature of the samples varied. The obtained samples were characterised by XRD, SEM, and ATR- FTIR analysis.

The insulation of buildings and transportation systems has emphasized the necessity to develop advanced materials taking concern to the comfort of modern society ; to noise reduction. A special class of advanced porous materials, i.e. aerogels, can be prepared from inorganic matter, synthetic or natural polymers, as well as inorganic/organic composites and hybrids. Among a variety of different porous materials, aerogels attract much attention due to their excellent properties such as high porosity (>90%), high specific surface area, a variety of macro- and mesopores, etc. The mechanisms of sound absorption are partly different from those of conventional porous absorbers with large macropores (different foams and fibrous materials). The understanding of the acoustic properties of aerogels is far from complete, and experimental results remain dispersed. The list of properties of aerogel materials could be extended to include non-toxic, biocompatible, renewable, and widely available materials. Most importantly, aerogels offer the possibility of functionalization of hydroxyl groups on the polymer backbone [1–3]. In this work, we prepared monolithic cellulose aerogels by the sol-gel procedure followed by their thorough characterization in terms of density, specific surface area and morphology. Samples are shaped to fit an impedance tube (29 mm diameter) to be tested as sound absorbers. Frequency sweeps were performed, and data were recorded from 500 to 6000 Hz. Cellulose concentrations were varied from 4 wt% microcrystalline cellulose (MCC) to 7 wt% MCC, and additionally samples were mixed with sodium sulphate during the preparation procedure to impact pore size, which consequently affects the sound insulation properties, see Figure 1.

Metakaolin is one of the most commonly used precursors for the geopolymer and zeolite preparation due to its high aluminosilicate content, and chemical purity. Generally, metakaolin is obtained by dehydroxylation of kaolinite structure by thermal activation. In this work, we prepared metakaolin through different activation routes, thermal and mechanochemical, respectively. Mechanochemically activated kaolinite (metakaolin) was chosen because it tends to follow the rules of green chemistry, by avoiding energy dissipation when high-temperatures are used. Geopolymers were additionally prepared using the conventional method of alkaline activation of metakaolin with sodium silicate solution. Zeolites were also prepared according to green chemistry rules and by mechanochemical activation instead of the commonly used, hydrothermal one. During the synthesis, both the water amount, and curing temperature were varied. First, the activation reactions were optimized, by monitoring the process and obtaining perfect values for most efficient parameters in terms of time, and other parameters such as temperature and milling speed. Furthermore, the correlation and difference between metakaolin prepared by two different methods were monitored. All prepared samples were thoroughly characterised. For the precursor, we monitored the degree of dihydroxylation, i.e., the degree of activation of the kaolin, or metakaolin preparation. For this purpose, we used the X-ray diffraction method (XRD) as a function of reaction time (milling or thermal activation). Following characterisation was performed using Fourier Transformed Infrared Spectroscopy (FTIR), which again allowed us to gain insight into the dihydroxylation rate and, to confirm characteristic aluminosillicate bonds present in our samples. Finally, we used Scanning Electron Microscopy to monitor microstructure of our samples, precursors and prepared geopolymes/zeolites.

Metakaolin is one of the most researched aluminosilicate minerals due to its simple structure and high (pozzolanic) reactivity. It is often used as a pure precursor in the synthesis of metastable zeolites (geopolymers) and zeolites themselves. However, metakaolin is a dehydroxylated form of kaolin clay and therefore needs high-temperature processing (usually between 600 and 800 °C). Mechanochemical synthesis represents a green approach in modern chemistry due to the reduced consumption of solvents, energy, and faster kinetics. By applying a mechanochemical approach in the synthesis of zeolites, hydrothermal conditions can be avoided, which is eco-friendlier. During the mechanochemical synthesis of zeolite from kaolin, the structure is disturbed through the dehydroxylation (amorphisation) of kaolin due to mechanical grinding, and at the same time, the reaction of alkaline ions and (meta)kaolin occurs, which results in the formation of zeolite and zeolite-like structures. Zeolites as 3D aluminosilicate structures, due to the defined sizes of the entrances of pores and channels, behave like molecular sieves that have very pronounced ion-exchange and adsorption properties. The ability to diffuse cations into the nanopores of the zeolite structure gives the possibility of high ionic conductivity, which opens up the possibility of using zeolites and zeolite-like structures in photovoltaic devices. In this work, the possibility of mechanochemical synthesis of zeolite was investigated, as well as the possibility of performance and applicability of thin-layer configurations of zeolite film in photovoltaic devices. The zeolite synthesis parameters were set to a molar ratio of 1 mol Na2O: 1 mol Al2O3: 2 SiO2, which correspond to zeolite A (LTA). Tape casting was used for the production of thin films, while the amount of water and the curing temperature of the samples was varied. The obtained thin film samples were characterized by XRD, ss-IS, and SEM analysis.

Nowadays, organic photovoltaic devices are receiving increased attention due to combination of their comparatively simple and cost effective processing and the ability to derive low weight, flexible thin-film solar cells for both indoor and outdoor application. Exciton generation and charge carrier recombination in such devices are influenced by multiple factors such as donor to acceptor ratio, energy offsets in the active layer (HOMO/LUMO) as well as energy alignment at the electron and hole transport layer interface, and lastly, active layer morphology. A good bulk heterojunction (active layer) needs to fully utilize excitons generated through the absorption of the acceptor and donor blend by converting the charge carrier flux into current at quantum yields as high as possible. Important parameters for this process are electron and hole mobilities, which often depend upon the crystallinity of the material inside the active layer as well as upon the crystal interconnectedness throughout the layer. These factors can be controlled through a variety of approaches out of which the molecular design is deemed to be the most important one nowadays. Here, we dedicated a study to spontaneous supramolecular assembly and thin film crystallization from solution by dropcasting of symmetric and asymmetric aminosquaraine derivatives to investigate the influence of various substituents on π-π stacking, preferential orientation and overall order of crystallinity. The synthesized compounds were characterized through cyclic voltammetry and UV-Vis spectroscopy, while thin films were fabricated for Grazing Incidence Small and Wide Angle X-ray Scattering (GISAXS and GIWAXS) using a 2D detector. The results revealed important information on crystallization suppression regarding volume hindrances caused by the extension of the chain. Moreover, the correlation between planarity of the molecule and quantity of the π-π bonds was discussed.