Seznam abstraktů 2022: SEKCE B - PRŮMYSLOVÉ A ENVIROMENTÁLNÍ APLIKACE NANOMATERIÁLŮ

Most human (industrial, mining, agricultural) activities result in the production of polluting wastes that often are not effectively removed before their release in the environment. Among pollutants, heavy metal ions and organic compounds, such as phenolics, drugs, and synthetic dyes are likely the most common. For example, heavy metals can easily bioaccumulate in living organisms causing chronic and acute toxicity or even carcinogenic and mutagenic effects. Synthetic dyes can absorb the sunlight limiting its penetration into deep waters, thus inhibiting the photosynthesis of aquatic plants, and limiting the water re-oxygenation capacity. Nanomaterials can help to either remove or detect environmental pollutants by mean of different mechanisms, like adsorption and catalysis. Ordered mesoporous silica (OMS) are inorganic nanostructured materials which can be easily obtained by surfactant-assisted sol-gel methods. Metal organic frameworks (MOFs) are organic-inorganic hybrid porous materials constituted by a cage-like structure consisting of an array of metal cations held together by organic linkers. Both types of materials are characterized by a highly uniform porous structure resulting in very high surface areas which make them very interesting for several purposes like, nanomedicine, industrial, and environmental applications. Here, the exploitation of OMS and MOFs for the removal and/or the detection of water pollutants, e.g., heavy metal ions, phenolics, and synthetic dyes is presented. These nanostructured materials were used either as adsorbents or supports for enzyme immobilization. The obtained adsorbents and immobilized biocatalysts are very promising tools for the removal and the detection of water pollutants.

Carbon felt electrode (CFE) is used as an electrode due to its good electric conductivity, high surface area, porosity, the ability to provide abundant redox reaction sites, excellent electrolytic efficiency, and mechanical stability at a relatively low cost [1-3]. However, they show poor wettability and low electrochemical activity. The most commonly used modification is CFE oxidation, which can be achieved by oxidising acid or thermal treatment. This activation step may improve the efficiency of the electrochemical processes and wettability through increased oxidised functional groups on the electrode surface.
Oxygen plasma treatment surface modification is single-step, effective and low time-consuming, and does not require solvents (eco-friendly). Acetaminophen electrooxidation is a reference standard representing anti-inflammatory, organic pharmaceuticals. The modification of the porous anodes results in increased kinetics of acetaminophen degradation in aqueous environments.
Our work focussed on CFE activation towards acetaminophen degradation. In order to show the efficiency of CFE modification with the use of oxygen plasma, this method was compared to other popular methods, i.e. thermal and chemical modifications. In thermal modifications carbon felt was heated at 250 °C and 500 °C. The chemical modifications were performed in hydrogen peroxide (30% H2O2) or in ammonium persulfate ((NH4)2S2O8). Finally, plasma-chemical modification was performed.
Given the low-cost and good performance in electrooxidation process, carbon felt electrode could be considered as anodes for organic pollutant degradation where their properties can be tuned by single-step, eco-friendly oxygen plasma modification.
REFERENCES: [1] González-García, J., Bonete, P., Expósito, E., Montiel, V., Aldaz, A., Torregrosa-Maciá, R., 1999. Characterization of a carbon felt electrode: structural and physical properties. J. Mater. Chem. 9, 419-426.; [2] Huong Le, T.X., Bechelany, M., Cretin, M., 2017. Carbon felt based-electrodes for energy and environmental applications: A review. Carbon 122, 564-591.; [3] Smith, R.E.G., Davies, T.J., Baynes, N. de B., Nichols, R.J., 2015. The electrochemical characterisation of graphite felts. Journal of Electroanalytical Chemistry 747, 29-38.

Electrochemical oxidation (EO) is a reliable, scalable and assessed advanced oxidation process (AOP) for the mineralization of various aqueous pollutants. However, the process efficiency and effectiveness strongly depend on the morphology and electrocatalytic properties of the anode. For these reasons, tailoring both the nano- and chemical structures of the electrode allows enhancing efficiency, by controlling the quality and quantity of electrogenerated oxidants. Boron-doped diamond (BDD) electrodes exhibit extraordinary electrochemical properties, among which, low background current, high oxygen evolution potentials, and high stability under high potentials, enabling them to generate a high amount of •OH radicals, thus making them ideal candidates for the EO process. Moreover, by tuning the BDD synthesis parameters, it is possible to tailor both electrode morphology and electronic structure. In particular, two different aspects have been investigated in this study by altering the feed gas composition during microwave plasma-enhanced chemical vapor deposition: the effect of boron concentration in BDD and the realization of sp2-C rich diamond electrodes.
Boron doping is known to affect the production of chlorinated species and it is linked to the production of different intermediates during perfluorooctanoic acid (PFOA) oxidation [1]. Indeed, lowly-doped BDD favors the mineralization of long-chain degradates. On the other hand, persulfate electrosynthesis depends on the stability/reactivity of •OH and diamond surface active sites. For this reason, the presence of sp2-active sites on the electrode surface may support the adsorption of SO4−• species, enhancing the oxidation of organic compounds [2].
REFERENCES: [1] Journal of Hazardous Materials 403 (2021): 123606.; [2] Electrochimica Acta (2022): 141069.

Irrespective of all affirmative physiochemical properties of polytetrafluoroethylene (PTFE) hollow fiber (HF) membrane, its promotion to be served for water purification function is significantly threatened by biofouling which is known as the primary problem in the membrane technology. The hydrophobic nature of PTFE attracts biofoulants leading to the pore blockage and lowering of the flux and functional life. Thus, this investigation aimed to devise an innovative silan-mediated polydopamine (PDA) coating incorporated with ZnO nanoparticles (NP) to trim the surface of the PTFE HF membrane and subsequently increase its functional property and biofouling resistivity. SEM images and EDX spectroscopies showed the time-dependent growth of PDA coating and elemental analysis on the surface, respectively. The water contact angle results illustrated the successful transformation of the surface characteristics of the PTFE HF membrane form hydrophobic (app. 120°) to superhydrophilic (0°) after surface modification. An exclusive dead-end cell was devised to comparatively evaluate the permeation and protein separation of surface-modified and pure PTFE HF membranes under constant pressure. Filtration tests’ results, alongside the microbial assessments, revealed that the modified membranes showed a lower tendency towards biofouling. The outcomes of this study shed light on addressing the key challenges of today's demands for harnessing membrane biofouling and remarkably expand the PTFE HF membrane’s potential to be utilized in advanced water treatment technology.

Fibrous materials represent very interesting structures with unique characteristics among other materials. They possess a high porosity, a large specific surface area, and good breathability. In addition, biopolymers and fibers thereof offer a whole range of opportunities in biomedical applications, such as wound healing, tissue engineering, and also cosmetics and dermatologics [1,2,3,4,5].
In this work, the focus was given to biopolymeric gums prepared by centrifugal spinning, which is an interesting approach with numerous advantages compared to electrospinning. [1,2] Gum Arabica was used as the main material for the centrifugal spinning. This biocompatible and biodegradable polysaccharide can be prepared into 3D foams of fibrous materials with great prospects for biomedical application. The solution blends of Gum Arabica (GA) with several different concentrations and Poly(ethylene oxide) were tested. GA and PEO fibers were produced as novel carriers for entrapment of vitamin E and vitamin C4 The morphology and structure of all these blend fibers were investigated by SEM and FTIR and RAMAN spectroscopy. Most importantly, they were characterized by the release of vitamin E loaded in the fibers using UV-VIS spectroscopy.
In addition, interesting results of bioactive fibers incorporated with ZnO nanoparticles were achieved recently that will be discussed in this work [5].
ACKNOWLEDGEMENTS: This work was supported by the Ministry of Education, Youth and Sports of the Czech Republic (MEYS, CZ.02.1.01/0.0/0.0/17_048/0007421) and by project LM 2018103. CzechNanoLab project LM2018110 funded by MEYS CR is gratefully acknowledged for the financial support of the SEM measurements at CEITEC Nano Research Infrastructure.
REFERENCES: [1] P. Zahedi et al., Polym. Adv. Technol. 21 (2009) 77-95.; [2] M. Rihova et al., J Appl Polym Sci. 168 (2021) e49975.; [3] L. Hromadko et al., ACS Omega 2 (2017) 5052-5059.; [4] M. Rihova et al., Carbohydr. 294 (2022) 119792.; [5] M. Rihova et al., Ms in preparation.

Over the past 15 years, self-organized TiO2 nanotube layers have attracted considerable scientific and technological interest due to their wide possible range of applications including (photo-) catalysis, hydrogen generation and biomedical uses [1,2]. The synthesis of the 1D TiO2 nanotube layers is usually carried out by electrochemical anodization of valve Ti metal sheets in various electrolytes. The advantage of anodic TiO2 nanotube layers compared to TiO2 nanotubes prepared by other methods (e.g. hydrothermal) are the tunability of dimensions, their directionality, ability to absorb significant amount of incident light and the possibility to utilize nanotube interiors and exteriors for decoration-coating of secondary materials [2].
The presentation will focus on the recent progress in the TiO2 nanotube layer synthesis. We will discuss an upscaling of the nanotube layers towards areas of dozens of cm2 [3, 4] and the preparation of high aspect ratio layers in a short time [5], considering the control of the anodization parameters. The selective etching of anodic TiO2 nanotube layers towards single-wall nanotube layers [6] and single nanotubes [7], where nanotubes are separated from one another into tube powders will be also discussed. Examples of magnetically guidable nanotube photocatalysts will be demonstrated [7,8].
REFERENCES: [1] J. M. Macak et al., Curr. Opin. Solid State Mater. Sci., 2007, 1-2, 3.; [2] K. Lee et al., Chem. Rev., 2014, 114, 9385.; [3] H. Sopha et al., Electrochem. Commun. 2018, 97, 91-95.; [4] H. Sopha et al., Applied Materials Today 2022, 29, 101567.; [5] M. Alijani et al., Electrochim. Acta 2021, 376, 138080.; [6] M. Motola et al., Electrochem. Commun., 2018, 97, 1-5.; [7] D. Beketova et al., ACS Appl. Nano Mater. 2020, 3, 1553−1563.; [8] M. Sepúlveda et al., Ms submitted.

Artificial photosynthesis (AP) is the mechanism allowing to perform CO2 reduction into fuels thanks to water and solar energy. Although works conducted to improve the selectivity (ability to direct the reaction to yield a particular product), stability (lifetime of the catalyst) and activation (ability to increase the rate of the desired reaction), no industrially viable systems are available at the present date. Efforts to make commercial, circular and scalable systems must be made.
We present the fabrication of a large-area electrode (≈137cm²) based on an electrochemically etched nanostructured porous silicon (PSi), coated by atomic layer deposited (ALD) titanium dioxide (TiO2), a photocatalyst. The porous structure was observed by SEM and we ensured the ALD allowed to deposit the catalyst down to the bottom of the pores using EDAX. PSi has proved to be an interesting material for AP applications thanks to its large specific surface area and low reflectivity in the visible. However, it is prone to photo-oxidation, leading the photoelectrochemical cells to be inefficient as the charge transfer becomes impossible. We demonstrate that a TiO2 layer as thin as 10 nm is thick enough to prevent silicon’s oxidation when exposed to water. The passivation efficiency was measured by following the Si-O-Si band evolution using FTIR technique while exposing coated and uncoated samples to water. The light absorption capabilities were measured on different PSi morphologies to determine which one could be more suitable for solar fuel production. Finally, wettability properties seem to make nanostructuration apt for catalysis in aqueous media.

Due to its low cost, chemical and thermal stability, and advantageous electronic and optical properties, TiO2 has become an irreplaceable material in many modern technologies, such as (photo)catalysis, sensing, or energy harvesting. In many cases, the intrinsic properties of TiO2 may be further enhanced by its nanostructuring and/or combination with other materials. While the nanostructuring increases the specific surface and facilitates physicochemical phenomena like adsorption and diffusion of chemical species, the presence of other materials might boost the functional properties of TiO2. A typical example of the latter is the combination of TiO2 with plasmonic metals that allows for the activation of visible light excitation of TiO2 and, in this way, improves the titania photocatalytic performance. This study introduces a novel plasma-assisted strategy for producing transparent and nanostructured TiO2:Ag coatings. This technique is based on the simultaneous deposition of Ti NPs by a magnetron-based gas aggregation source and sputter deposition of silver. As shown, after the thermal annealing step that transforms metallic Ti NPs to TiO2, formed films preserve a highly porous structure composed of individual TiO2 nanoparticles decorated with Ag nano-islands. Furthermore, the size/number of Ag nano-islands can be adjusted by changing the Ag and Ti NPs deposition rates ratio, which in turn allows for controlling the optical properties. This result thus paves the way for the solvent-free and cost-effective production of nanomaterials with tailor-made properties for future applications.
ACKNOWLEDGEMENTS: This work was supported by the grant GAČR 21-05030K from the Grant Agency of the Czech Republic.

Lithium-ion batteries (LIBs) are widely used to power portable devices, microelectronics, vehicles, etc. With many advantages such as high surface area and improved charge transport, self-supported 3-D nanostructured metal oxides such as titania nanotubes (TNTs) are promising electrode materials for LIBs and their impact is particularly significant when considering the miniaturization of energy storage systems and the development of 3D microbatteries.
This presentation will review the fabrication of all-solid-state Li-ion microbatteries using modified TNTs as negative electrodes [1-9]. Effects of material selection and processing on the performance and reliability are presented as a means to develop conceptual guidelines to understand and improve microbattery designs. Different chemical modifications of nanotubes by ALD technique [10] and by the conformal electrodeposition of polymer electrolytes [11] for enhanced electrochemical performance will be presented. Fabrication of full 3D microcells showing high electrochemical performance will be presented and the development of the next generation of 3D flexible microbatteries will be also introduced.
REFERENCES: [1] B. L. Ellis, P. Knauth, T. Djenizian, Adv. Mater., 26, 3368 (2014).; [2] N. Plylahan, M. Letiche, M. Barr, and T. Djenizian, Electrochem. Commun., 43, 121 (2014).; [3] N. Plylahan, A. Demoulin, C. Lebouin, P. Knauth, T. Djenizian, RSC Adv., 5, 28474 (2015).; [4] N. Plylahan, M. Letiche, M. Barr, B. Ellis, S. Maria, T. N. T. Phan, E. Bloch, P. Knauth, and T. Djenizian, J. Power Sources, 273, 1182 (2015).; [5] G. Salian, C. Lebouin, A. Demoulin, S. Maria, P. Knauth, M. Lepihin, A. Galeyeva, A. Kurbatov, and T. Djenizian, J. Power Sources, 340, 242 (2017).; [6] I. V. Ferrari, M. Braglia, T. Djenizian, and P. Knauth, J. Power Sources, 353, 95 (2017).; [7] G. Salian, B. M. Koo, C. Lefevre, T. Cottineau, C. Lebouin, A. T. Tesfaye, P. Knauth, V. Keller, T. Djenizian, Adv. Mater. Technol., 3, 1700274 (2018).; [8] Fraoucene, V. A. Sugiawati, D. Hatem, M. S. Belkaid, F. Vacandio, M. Eyraud, M. Pasquinelli, T. Djenizian, Front. Chem., 7, 66 (2019).; [9] G. D. Salian, C. Lebouin, M. Galeyeva, A. P. Kurbatov, T. Djenizian, Front. Chem., 7, 675 (2019).; [10] H. Sopha, C. Ghico, S. Ng, M. Alijani, L. Hromadko, J. Michalicka, T. Djenizian, J. Macak, Materials Chemistry and Physics, 276, 125307 (2022).; [11] V. A. Sugiawati, F. Vacandio, T. Djenizian, Molecules, 25, 2121 (2020).

The development of cost-competitive materials capable of producing fuels or electricity directly from the energy harvested from sunlight offers a desirable approach to fulfilling the need for clean, sustainable, and secure energy. Semiconductor metal oxides (e.g., TiO2, Fe2O3, or BiVO4) are abundant, photoactive, stable and cheap; and thus they have been among the most widely adopted materials for the conversion of solar energy into storable and transportable chemical energy such as e.g. hydrogen (H2). However, despite a huge scientific effort, their overall efficiency for solar-driven applications remains rather low due to several crucial limitations such as particularly fast recombination of photo-generated charges (electron-hole pairs) and sluggish kinetics of the redox surface reactions that hinder the practical application in this field. Defect engineering has become an attractive research direction for improving the optical and electronic properties of semiconductor photocatalysts towards boosting their photo(electro)chemical performance. For example, so-called non-stoichiometric black TiO2 has demonstrated unexpectedly enhanced photo(electro)chemical activity, which has been attributed to the co-catalytic effect of unsaturated Ti3+ ion at the titania surface due to the presence of oxygen vacancies (VO). Additionally, these unsaturated defects/sites provide a strong affinity to tightly bond or anchor various species such as transition metals single atoms, or carbon dots that can be used as even more effective co-catalysts. In this contribution, recent advancements regarding defect engineering toward significantly enhanced photocatalytic activity of oxide semiconductors will be summarized.

Reduction of nitroaromatics to the corresponding amines is a key process to produce polymers, pharmaceuticals, agrochemicals and dyes [1]. However, their effective and selective reduction requires high temperatures, pressurized hydrogen and involves noble metal-based catalysts [1]. Here we report on an earth-abundant, plasmonic nano-photocatalyst (CuFeS2), with an excellent reaction rate towards the selective hydrogenation of nitroaromatics. With solar light as the only energy input, the catalyst operates through the combined action of hot-holes and photothermal effects. Ultrafast laser transient absorption and light-induced electron paramagnetic resonance spectroscopies unveiled the energy matching of the hot holes in the valence band of the catalyst with the frontier orbitals of the hydrogen and electron donor, via a transient coordination intermediate. Consequently, the reusable and sustainable CuFeS2 catalyst delivers previously unattainable turn-over-frequencies, even in large-scale reactions, while the cost-normalized production rate stands an order of magnitude above the state-of-the-art [2].
ACKNOWLEDGEMENTS: We thank the ERDF and ESF (project no. Z.02.1.01/0.0/0.0/16_019/0000754), and the Czech Science Foundation (EXPRO project no. 19-27454X).
REFERENCE: [1] Westerhaus, F.A. et al. Nat. Chem. 5, (2013) 537-543.; [2] A. Cheruvasthoor Poulose, G. Zoppellaro, I. Konidakis, E. Serpetzoglou, E. Stratakis, O. Tomanec, M. Beller, A. Bakandritsos, R. Zbořil, Nat. Nanotechnol. (2022), https://doi.org/10.1038/s41565-022-01087-3.

Development of elastic nanosilicon-based anodes is considered as a promising strategy towards advanced lithium-ion batteries (LIBs) since silicon exhibits high theoretical specific capacity and relatively low discharge potential. However, silicon materials are not yet commercialized in LIBs mainly because of the large volume expansion of silicon during the lithiation and delithiation processes, and thus a sharp drop of the storage capacity over a number of battery cycles. The large volume expansion of silicon causes fracture of electrodes, and thus structural and mechanical damage.
To overcome the poor electrical conductivity of Si nanoparticles and allow a more effective supply of Li-ions into it, it has been incorporated with conductive materials. Carbonaceous materials (e.g. carbon black) represent the main material class that has been investigated for application in Si-based anode materials. Lately, another class of electrically conductive materials ‒ electrically conducting polymers (ECP) such as polypyrrole (PPy) ‒ have been integrated with Si nanoparticles to prepare Si/ECP composite materials. Also various polymer binders as polyacrylic acid are usually added to the composite to enhance the mechanical stability of the anode material thanks to the higher polymer modulus values and to the physical binding between the components. Despite the fact that many of these Si/carbon composite materials provide enhanced battery performance, there are still numerous issues that must be addressed.
Building on this concept and on the recent advances, new silicon-based anodes containing tailor-made PPy nanoparticles were prepared, and their electrochemical performance was evaluated.

Nanostructured anodes prepared with Si nanoparticles (10 nm) integrated within a conductive carbon-based matrix for the Li-ion batteries (LIBs) were studied by in situ Raman spectroelectrochemical (SEC) method, which gives information on the crystal lattice changes and possible degradation/amorphization of Si nanocrystals, as well as on the stability of the carbon matrix. An advantageous feature of silicon as an anode material is a high theoretical specific capacity (4200 mAh/g) compared to commonly used graphite (372 mAh/g), wide elemental abundance, and low discharge potential (∼0.4 V vs Li/Li+). Unfortunately, the large volume expansion (more than 300%) and associated stress in silicon electrode materials, as well as the significant storage capacity decrease during charge/discharge cycles affect the performance of Si-based LIBs in many ways. In this work, the key degradation processes in the composite electrodes during electrochemical lithiation and delithiation processes were studied. The shift of the first-order Raman peak of crystalline Si at 521 cm-1 is related to the stress evolution in nanoparticles caused by SEI (solid electrolyte interphase) layer formation on the electrode surface within the first charge/discharge cycle, and also to the lithiation-induced stress (tensile-to-compressive stress transition) in Si nanoparticles and in the native silicon oxide on their surface. Additionally, cyclic voltammetry and galvanostatic charge-discharge cycling were used to determine the stability of the SEI layer and the long-term capacity degradation of the Si electrode.
ACKNOWLEDGEMENTS: This work was supported by the Ministry of Education, Youth and Sports of the Czech Republic, contract No. CZ.02.1.01/0.0/0.0/16_026/0008382.

Environmentally sustainable, low-cost, flexible, and lightweight energy storage technologies require advancement in materials design in order to obtain more efficient organic metal-ion batteries. Synthetically tailored organic molecules, which react reversibly with lithium, may address the need for cost-effective and eco-friendly anodes used for organic/lithium battery technologies. Among them, carboxylic group-bearing molecules act as high-energy content anodes. Although organic molecules offer rich chemistry, allowing a high content of carboxyl groups being installed on aromatic rings, they suffer from low conductivity and leakage to the electrolytes, which restricts their actual capacity, the charging/discharging rate, and eventually their application potential. Here, a densely carboxylated but conducting graphene derivative (graphene acid) has been designed to circumvent these critical limitations, enabling effective operation without compromising the mechanical or chemical stability of the electrode. Experiments including operando Raman measurements and theoretical calculations revealed excellent charge transport, redox activity, and lithium intercalation properties of the graphene acid anode at single-layer level, outperforming all reported organic anodes, including commercial monolayer graphene and graphene nanoplatelets. The practical capacity and rate capability of 800 mAh/g at 0.05 A/g and 174 mAh/g at 2.0 A/g demonstrate the true potential of graphene acid anode in advanced lithium-ion batteries.

Vakuum servis s.r.o. is a service centre of Pfeiffer Vacuum, and also a representative of VAT Vakuumventile, SPECS, Scia Systems and HSR AG for the Czech and Slovak Republic. The company has been operating for more than 25 years in the field of vacuum technology, vacuum deposition and helium leak detection. The company is engaged in sales of vacuum equipment, servicing of rotary, dry, turbo and diffusion vacuum pumps, modernization of vacuum equipment, and produces helium leak detection systems. We manufacture customized HV and UHV vacuum systems .
We support company SPECS which is leader in the development and production of customized UHV surface analysis systems.
SPECS’ scientists and engineers are embedded in a global team of more than 150 employees designing, producing, selling and maintaining instruments for surface science, material science and nanotechnology.

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This paper investigates the geopolymers with metal microparticles (metal powder) as additives and assesses the antimicrobial effect of these composites. Samples of geopolymers were prepared with 4 % silver, copper, or nickel microparticle additive. The antimicrobial properties were based on a leaching test from composites, and the inhibition zone around Escherichia coli and Micrococcus luteus bacteria cells was investigated. Microparticles, especially silver and copper, were confirmed to be effective as antimicrobial reagents in geopolymer composites. Further studies will be focused on finding a suitable low concentration (due to cost) with sufficient antibacterial activity; other assessment options for the antibacterial effectiveness of these highly alkaline geopolymers will also be addressed.