Seznam abstraktů 2024: SEKCE B - PRŮMYSLOVÉ A ENVIROMENTÁLNÍ APLIKACE NANOMATERIÁLŮ

Metal nanoparticles on conductive or semiconductor surfaces are of wide scientific and technological interest. They find application as catalysts in electro- and photo-catalytic reactions, or in plasmonics and sensing, among other areas.
A straightforward and versatile, yet underexplored, way to produce supported metal particles is “solid-state dewetting” [1], that is, the heat-induced agglomeration of thin metal films into defined nanoparticles well-attached onto a support.
In this talk, I will discuss the use of solid-state dewetting to control key properties of catalyst nanoparticles (size, composition, and structure) formed on electrodes and photocatalytic layers [2]. I will show how to enable nanoscale effects such as metal-support interactions to boost the catalyst performance in electrocatalytic reactions (e.g., hydrogen evolution) [3], and how tuning the catalyst composition affects catalyst stability and activity in photocatalysis [4,5]. In addition, I will show how dewetting can be steered to produce model nanocatalysts composed of ensembles of spatially-separated and uniformly-oriented metal nanoparticles with defined exposed facets [6].
REFERENCES: [1] C.V. Thompson, Annu. Rev. Mater. Res. 2012, 42, 399; [2] M. Altomare et al., Chem. Sci. 2016, 7, 6865; [3] S. Harsha et al., Adv. Funct. Mater. 2024, 2403628; [4] D. Spanu et al., ACS Catal. 2020, 10, 15, 8293; [5] D. Spanu et al., ACS Catal. 2018, 8, 6, 5298;
[6] R.K. Sharma et al., 2023 Meet. Abstr. MA2023-02 2059.

Platinum group metals such as Pt, Ru, Pd, Ir, etc., have superior performance for various catalytic applications [1]. Due to their scarcity, efforts were being made to reduce the mass/loading or replace these noble metals. Atomic Layer Deposition (ALD) is one among the best technique to facilitate lowering of loading mass on a support of interest [2,3]. Due to the governing surface energy variations between noble metals and support surfaces, the growth initiates as nanoparticles (NP) and with a further increase in ALD cycles the agglomeration among NP’s dominates over the individual NP size increase, thus developing thin films of relatively higher thickness.
For electrocatalytic applications, it is important to choose the right substrates. Among available substrates, carbon papers and titania nanotube layers are best choices considering their physio-chemical properties, availability and low costs incurred.
The uniform decoration of these substrates by NPs of catalysts proved to be highly efficient in electrocatalysis, as shown in our recent papers [4-6].
The presentation will introduce and describe the synthesis of different noble metal NPs by ALD on important substrates. It will also include the corresponding physical and electrochemical characterization and encouraging results obtained in electrocatalysis.
REFERENCES:[1] Huang, Z. F. et al. Advanced Energy Materials vol. 7 (2017) 1700544; [2] Yoo, J. E. et al. Electrochem. commun. 86, (2018) 6; [3] Anitha, V. C. et al. J. Catal. 365, (2018) 86; [4] Sitaramanjaneya M. Thalluri & Macak, J. M. Small (2023) 2300974; [5] B. Bawab et al., Electrochim. Acta 429 (2022) 141044; [6] B. Bawab et al. CEJ 485 (2024) 148959

Rare earth elements (Gd, Lu, Tm, Tb, Pr) modification effects on two-phased TiO2 (anatase-brookite) were analyzed. The powders were synthesized by a one-step hydrothermal method. The phase composition, crystalline size and shape of samples were studied by X-ray powder diffraction, transmission, scanning electron microscopies and energy-dispersive X-ray spectroscopy. The decreasing of crystallite size and increasing of lattice strain due to the modification were confirmed by the Scherrer, modified Scherrer, Williamson-Hall, Size-strain plot (SSP) and Halder-Wagner methods. The textural characteristics of the samples were determined from N2 adsorption-desorption isotherms using the methods of Brunauer-Emmet-Teller and Barret-Joiner-Halenda and revealed their mesoporous structure. UV-Vis diffuse reflectance spectra of the modified samples showed a blue shift compared to the unmodified sample. The values of band gap energy of the modified powders increased due to a phenomenon of quantum confinement or size quantization. The modification with rare earth elements improved the photocatalytic activity of anatase-brookite composite in the reaction of hydrogen evolution, which is ascribed to physico-chemical properties.

Green renewable biopolymers have attained extensive attention recently in advanced electronics and wearable sensing devices to decrease the cost and, above all, to replace nonbiodegradable dielectric thermoplastic polymers (e.g. BOPP and PVDF) while retaining device’s flexibility and boosting their recyclability. Among them, nanocellulose has gained particular attention due to its inherent biocompatibility, biodegradability, and cost-effectiveness. Nanocellulose consists of linear cellulose chains of repeating ß-D-glucopyranose units, covalently connected through b-1,4 glycosidic bonds, which symmetrical molecular structure with dipole moments of C-H and C-OH bands generate a strong polarity, and yield differently semi-crystalline structures by intra- and intermolecular hydrogen bonds between adjacent glucose groups, all beneficial for dielectric properties.
Herein, films were prepared from native (CNF) and carboxylated (TCNF) cellulose nanofibrils, with and without the addition of thermally conductive multi-layered Ti3C2Tx MXene, to examine the impact of polar (−OH, −COOH) surface groups on the film morphological, moisturizing, dielectric (permittivity, loss, and AC conductivity), and thermal dissipation properties as function of temperature (0 to 100°C). The electrostatic repulsion and hydrogen bonding interaction between the hydrophilic surface/terminal groups on CNF/TCNF and MXene was shown to render their self-assembly distribution and organization into morphologically differently structured films, and, consequently, different properties.
ACKNOWLEDGMENTS: This work was supported by the Slovenian Research and Innovation Agency (Project no. J2-3053 and Programmes no. P2-0424 and P1-0125).

Amidst growing concerns over the environmental impact of petroleum-based industries and their contribution to global ecological challenges, there is a pressing need for sustainable alternatives in chemical synthesis. This study addresses this imperative by exploring an innovative catalytic approach for the eco-friendly production of acetaldehyde from ethanol, a crucial chemical feedstock. Catalysts utilized so far perform poorly due to their low stability. Supported copper nanoparticles at higher temperatures suffer from the rapid deactivation caused by nanoparticles sintering and reduction of active sites by coking. To address this issue, the advanced copper nanoparticle-decorated nanofibers (107 nm in diameter) with outstanding surfacer area (700 m2 g−1) were synthesized and tested, showing enhanced stability to benchmark (Aerosil 300 SiO2/Cu). Two approaches were compared for copper catalyst preparation, i.e., dry impregnation and one-pot synthesis. Remarkably, the dry-impregnated DI-9.4 sample at 325 °C after 100 h remained at over 66 % of ethanol conversion with 99 % selectivity to acetaldehyde (acetaldehyde productivity: 3.09 g g h-1) compared to benchmark catalyst dropped to 40 % of ethanol conversion. These findings highlight the potential of the superior morphological advantage of electrospun SiO2 nanofibers as efficient catalysts.
ACKNOWLEDGEMENTS: This work was supported by the project Quantum materials for applications in sustainable technologies (QM4ST), funded as project No. CZ.02.01.01/00/22_008/0004572 by P JAK, call Excellent Research.

This study demonstrates the use of needle-punched nonwoven fabrics of poplar seed fiber and polyester fiber blends in sensor applications. For this purpose, the surfaces of the produced fabrics were functionalized by coating them with silver nanowires (AgNWs). AgNWs were synthesized according to the polyol method and then coated onto the nonwoven fabrics through dip coating process. Surface morphology is characterized by scanning electron microscopy (SEM), and the analysis revealed a uniform coating on the fabric surface. Measurement of electrical surface resistance of treated fabrics confirmed that the presence of silver nanowires significantly improved the electrical conductivity. The capacitor structure was fabricated as a sandwich via placing a stretchable sealing film (Parafilm®️) between two conductive nonwoven samples. Variation in the relative capacitance as a result of loading and unloading was observed. Poplar blended nonwoven fabrics exhibited great potential to be used as capacitive sensors to measure variable weight pressures. By virtue of its biodegradability, availability and light-weight solution, bio-waste poplar fibers offer a novel application for developing wearable and flexible tactile sensors.

A new synthetic approach for hematite (Fe2O3) nanofibers was developed using a centrifugal spinning process followed by a two-step annealing treatment. Initially, the spinning solution was prepared with two different iron precursors and polyvinylpyrrolidone (PVP). These fibers were then subjected to a two-step high-temperature annealing process with optimized profiles to convert them into hollow hematite (α-Fe2O3) nanofibers. Comprehensive characterization of both the as-spun and annealed fibers was performed using scanning electron microscopy (SEM), X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and textural analyses. The photocatalytic performance of the hematite fibers was evaluated under UV light illumination for the photocatalytic carbon dioxide reduction and hydrogen production. The resulting hematite fibers exhibited very good photoactivity compared to the commercial TiO2-P25 photocatalyst. Due to their hollow structure, and excellent photocatalytic activity, these nanofibers show great potential for future photocatalytic applications.

Nanorobots, self-propelled autonomous nanomachines, can perform desired tasks in bio-applications, medical fields, and environmental remediation, among others. In the latter, nanorobots have been introduced as powerful tools due to their efficiency and great versatility [1]. To apply nanorobots in environmental remediation, their design must be customized to enable propulsion capabilities while providing efficient task accomplishement, such as pollutant sensing, capture, removal, transport, degradation, or chemical conversion. In this regard, it is highly advantageous to fabricate nanorobots by applying the principles of nanoarchitectonics [2,3]. Nanoarchitectonics studies the assembly and self-assembly abilities on the molecular and atomic levels and their influence on the properties of resulting nanomaterials. Using nanoarchitectonics, affinity of nanorobots toward pollutants can be tuned while enabling efficient propulsion in a specific environment. Additionally, catalytic abilities can be provided to degrade pollutants in the ‘on-the-fly’ mode. This talk will introduce approaches toward designing nanorobots for environmental remediation by applying the principles of nanoarchitectonics. The decoration with nanoscaled materials, such as magnetic nanoparticles and their influence on catalytic properties will be discussed. Moving to the molecular level, the influence of hydrogen bonding on the resulting properties of the nanorobots will be presented. Finally, nanorobots with decorations on the atomic scale will be introduced.
This work was supported by JSPS KAKENHI Grant Number 24KF0086.
REFERENCES: [1] A. Jancik-Prochazkova et al. ACS Appl. Mater. Interfaces 2022, 14, 45545-45552; [2] A. Jancik-Prochazkova et al. ACS Nano 2022, 17, 146-156; [3] A. Jancik-Prochazkova et al. Adv. Funct. Mater. 2024, 2402567.

Wastewater treatment is a global challenge 1, and photocatalysis offers a promising solution. This technique harnesses light and catalysts to break down pollutants in water, making it simpler and more sustainable than traditional methods 2.
The key to photocatalysis lies in the generation of reactive oxygen species (ROS) by the photocatalyst. These highly reactive molecules, including hydroxyl radicals (OH•), superoxide anion radicals (O₂•⁻), and singlet oxygen (¹O₂), break down pollutants into harmless components 3.
Recent research focuses on molybdenum disulfide (MoS2), a special material with properties ideal for generating ROS. MoS2's layered structure boasts active sites, particularly at its edges, where molybdenum atoms bond with unsaturated sulfur atoms. These edge sites readily trap light-generated electrons, initiating a cascade of reactions that ultimately produce ROS 3.
In this work, different new photocatalysts combining MoS2 with silicon based materials (mesoporous silica or integrating np silicon junctions) are explored for wastewater treatment. Different synthesis methods and MoS2 phases are being explored to optimize the number and distribution of these active edge sites, maximizing ROS production 4. Additionally, co-catalysts are used to further enhance ROS generation and minimize the recombination of these reactive species 2. The effectiveness of these photocatalysts is tested against common pollutants like dyes and antibiotics.
REFERENCES:
[1] United Nations, 2023, https://www.un.org/sustainabledevelopment/water-and-sanitation/.
[2] Sinar Mashuri, S.I.; Ibrahim, M.L.; Kasim, M.F.; Mastuli, M.S.; Rashid, U.; Abdullah, A.H.; Islam, A.; Asikin Mijan, N.; Tan, Y.H.; Mansir, N.; et al. Photocatalysis for Organic Wastewater Treatment: From the Basis to Current Challenges for Society. Catalysts 2020, 10, 1260.
[3] Rahman, A.; Jennings, J. R.; Tan, A. L.; Khan, M. M. Molybdenum disulfide-based nanomaterials for visible-light-induced photocatalysis. ACS Omega 2022, 7 (26), 22089- 22110.
[4] L. Zhou et al. Morphology/phase-dependent MoS2 nanostructures for high-efficiency electrochemical activity. J Alloy Compd 2020, 818.

The conversion of biomass platform chemicals, such as furfural (FFA) and levulinic acid (LA), into biofuels like furfural ether and γ-valerolactone (GVL) is highly significant. In this research, a nanoporous inorganic-organic Zr−phosphonate catalyst (ZrNPO3) was developed and utilized to selectively produce GVL through the catalytic transfer hydrogenation of LA. This catalyst, which features both acidic and basic sites, was also employed to generate biofuels like GVL and furfuryl ether under mild reaction conditions via cascade furfural transformation. The selectivity for GVL was further improved by using phosphotungstic acid@ZrNPO3. The study incorporated catalytic optimization, poisoning studies, and detailed physicochemical characterization to gain insights into the structure-activity relationship and reaction mechanism. The exceptional activity of the catalyst was attributed to the synergistic presence of Lewis acidic and basic sites. Developing a single catalyst capable of the one-pot tandem conversion of FFA to GVL represents a significant innovation for both catalysis researchers and the biofuel industry.

In the last several years, spin polarization of electrons has been reported as a promising method of improving oxygen evolution reaction (OER). Here, we report the development of a system of novel nanoantennas with a chiral lock for plasmon-assisted water splitting. The chiral nanoantennas were prepared via a thin mesoporous gold film, on which a dielectric spacer containing a chiral substance (L- or D-tryptophan) was deposited and a thin layer of platinum was sputtered. The resulting samples were characterized at each step of their preparation using modern analytical methods, such as AFM, SEM-EDX, XRD, XPS, UV-Vis and Raman spectroscopy. It is hypothesized that electron spin polarization suppresses the formation of hydrogen peroxide and promote the formation of the ground state O2 triplet during OER. This was confirmed via electrochemical measurements, particularly using linear sweep voltammetry and chronoamperometry in two regimes - with and without illumination. During the experiments, we found a correlation between the OER efficiency and the presence of chiral substances in the dielectric spacer. Practical measurements are consistent even after numerous repetitions, implying their accuracy. Finally, based on these results, a theoretical working principle of this system was proposed.

ACKNOWLEDGEMENT This work was supported by the GACR under project 23-08509S.

Poplar fibers, known for their high cellulose content and hollow structure, are primarily discarded as waste in the wood industry despite the tree's abundance. Recent advancements have enabled the utilization of poplar fibers in the textile industry, specifically in the production of nonwoven fabrics. This study explores the potential of valorizing poplar fibers by functionalizing them with silver nanowires (AgNWs) for technical applications. The focus is on enhancing the durability of conductive poplar nonwovens against washing procedures. Initially, silver nanowires were synthesized via the NaCl-mediated polyol method and subsequently coated onto a blend of poplar and polyester (PET) nonwoven fabric. The conductive fabric samples underwent a series of washing cycles to assess their durability. Post-washing analyses included morphological characterization and conductivity measurements to evaluate the performance and resilience of the coatings. This study provides insights into the wash durability of conductive poplar nonwovens, contributing to their potential application in electronic wearables, where compliance and comfort are critical.

In the PEM fuel cells technology research and development, like it is a case of most of the systems, significant attention is being paid by the research community to development of the novel, more efficient and less costly materials. Often is, however, neglected optimal application of such materials in the systems working under real conditions. Here different aspects need to be considered, like homogeneity of the local quantities distribution, sufficient accessibility of the reactants at the reaction sites etc. PEM fuel cells are using gaseous reactants (typically hydrogen and oxygen), generating water as a product. Gaseous reactants pose challenge to the electrochemical processes. It is because they are characterized by a relatively low volumetric density. At the same time, they are electrically insulating. To overcome these problems and to ensure high intensity of the electrode reactions, structure of the entire setup involving the electrodes, polymer electrolyte membrane and flow and electric charge distributors, needs to be highly optimized. The target of this contribution is to address selected aspects of the PEM fuel cells electrodes production, as well as aspects of their combination with the flow and charge distributors.

The production of green hydrogen, i.e. strictly from renewable resources, has become a worldwide global issue. The most advanced method is the electrolysis of water using electricity from a de-carbonated source. Another method is the dissociation of water by photocatalysis. Photocatalysis seems pivotal because it combines a simpler energy conversion scheme and systems whose photons-to-hydrogen conversion efficiency is close to unity. However, these efficiencies are only obtained in the absorption range of the photocatalysts which is often very limited and generally in the UV range. The efficiency, under solar irradiation, is solely constrained by the small fraction of useful light for photocatalysis (a few percent) and not anymore by the photocatalyst itself. Converting this unused light (~95%) into light adapted to the photocatalyst’s absorption is the route to obtain competitive efficiencies compared to the electrolysis process.
Upconversion is in this regard an interesting approach to harvest sunlight from IR and visible and thus enhance the overall solar to hydrogen conversion of photocatalyst. Through careful synthetic approaches we have developped Infrared to UV upconversion particles that in combination with classic photocatalysts (TiO2) can allow a significant improvement of the photocatalytic efficiency under solar irradiation.

The development of micro/nanostructures, which can move in a fluid environment in a controlled and autonomous way while performing specific tasks, is one of the present challenges of nanoscience and nanotechnology. In this context, many self-powered devices have been developed either as motors in a free-standing configuration (swimmers) or immobilized on a substrate (pumps). Among them, motors that are self-propelled by catalytic reactions have attracted a lot of attention. However, most of these devices are triggered by toxic chemicals, which prevents their applicability in various contexts, or cannot work at high salt concentrations. Therefore, new propulsion mechanisms, materials or safe chemicals need to be explored to overcome such limitations.
Ion exchange is one of the most interesting processes occurring at the interface between aqueous solutions and polymers endowed with sulfonic groups, such as the well-known Nafion1. When exchanged ions possess varying diffusion coefficients, this process generates local electric fields that can be utilized to propel fluid motion1,2. In this study, we demonstrate the design and fabrication of self-propelling micro/nanoswimmers and pumps based on Nafion, powered by ion exchange and fueled by salts. These Nafion micromachines are created through different lithographic techniques (colloidal, stencil, photo or electron beam lithographies) shaping Nafion into asymmetric structures3,4. The resulting micro/nanoswimmers exhibit fascinating collective motion in water driven by the interplay of their self-generated chemical/electric fields and their capability to pump surrounding matter towards them. The pumping activity of the micro/nanoswimmers induces the formation of growing mobile clusters, whose velocity increases with size. Such dynamic structures are able to trap nearby micro/nano-objects while purifying the liquid, which acts both as the transport media and as fuel3,4. This phenomenon holds promise for potential applications in water remediation currently under development.
References
[1] M. J. Esplandiu, D. Reguera, and J. Fraxedas, Soft Matter, 16 (2020) 3717.
[2] M. J. Esplandiu, K. Zhang, J. Fraxedas, B. Sepulveda, and D. Reguera, Acc. Chem. Res., 51 (2018) 1921
[3] M. J. Esplandiu, D. Reguera, D. Romero-Guzman, A. M. Gallardo-Moreno, and J. Fraxedas, Nat. Commun. 13 (2022) 2812.
[4] J. Fraxedas, D. Reguera, M. J. Esplandiu, Faraday discussions, 249 (2024) 424.

Flexible capacitive pressure sensors have applications in a wide variety of fields, especially soft robotics, bioelectronics, wearable devices and healthcare applications. In this study, a capacitive pressure sensor has been designed and fabricated using silver, nickel, and carbon nanoparticle conductive inks. Pad printing method was used to print nanoparticle inks on a polyamide-based taffeta label fabric. Capacitive pressure sensor underwent testing through three methodologies; these are pressing different fingers on the sensor surface, dropping water on the sensor and applying bending-relaxation process to the pressure sensor to determine sensor performance measuring capacitance variations. The capacitance of the fabricated pressure sensor changed according to the type of finger pressed and the number of water droplets dropped. As the amount of water droplets and the force of the pressed finger increase, the capacitance changes in the printed sensor also increase. On the other hand, there was no significant change in the capacitance values of the sensor after the bending-relaxation application. This shows that the proposed flexible pressure sensor can be used in wearable electronics, human-robot interactions, pressure mapping or detection of finger touch.

In this study, a flexible force sensor with silver and carbon mixed conductive nanoparticles was designed and tested for use in the robotics field. Conductive inks composed of Ag:C nanoparticles were printed on polyamide-based taffeta label fabric by pad printing method in order to fabricate a capacitive force sensor. The sensitivity of this capacitive sensor structure was tested and evaluated by loading different weights. The results showed that as the concentration of carbon nanoparticles in the conductive ink increases, a decrease in capacitive energy loading is observed. Hence, the production of a capacitive force sensor form was carried out with the appropriate number of printing layers and Ag:C concentration. The focus of research lies in the discovery and development of durable flexible force sensors for motion tracking in robotic applications.