List of Abstracts 2021: SESSION B - INDUSTRIAL AND ENVIRONMENTAL APPLICATIONS OF NANOMATERIALS
Date: October 21, 2021
The self-organized TiO2 nanotube layers have attracted considerable scientific and technological interest over the past 13 years motivated by their possible range of applications including photocatalysis, solar cells, hydrogen generation and biomedical uses [1,2]. The synthesis of these 1D TiO2 nanotube layers is carried out by a conventional electrochemical anodization of valve Ti metal sheet.
Among other TiO2 nanomaterials, these nanotube layers stand out due to their directionality, tunability of dimensions, ability to absorb significant amount of incident light and the possibility to utilize nanotube interiors and exteriors for decoration-coating of secondary materials.
One of the most significant applications of TiO2 nanomaterials is photocatalysis, which is very effective to decompose various pollutants (e.g. dyes) and kill bacteria [3,4].
The presentation will focus on the utilization of the nanotube layer for photocatalytic removal of various species in the liquid phase [5, 6] as well as gas phase [7]. We will also show that various secondary materials have a positive influence on photo-electrochemical properties of nanotube layers [8, 9]. Experimental details and some recent photocatalytic results will be presented and discussed.
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] K. Rajeshwar et al., J. Photochem. Photobiol. C: Photochem. Rev. 2008, 9, 171.; [4] Ch. Wei et al., Environ.Sci. Technol. 1994, 28, 934.
[5] J.M. Macak et al., Small, 2007, 3, 300.; [6] H. Sopha et al., Appl. Mater. Today, 2017, 9, 104.
[7] H. Sopha et al., Electrochem. Commun., 2018, 97, 91.; [8] S. Ng et al., Adv. Mater. Interfaces 2017, 1701146.; [9] F. Dvorak et al., Appl. Mater. Today, 2019, 14, 1.
Sulfur represents a low‑cost, sustainable and high theoretical capacity cathode material for lithium-sulfur batteries, which could meet the growing demand in portable power sources. However, the shuttling‑effect of the formed lithium polysulfides, as well as their low electric conductivity, compromise the electrochemical performance of lithium-sulfur cells.[1] To tackle this challenge, a so far unexplored cathode was developed, composed from sulfur covalently bonded directly on graphene. This was achieved by leveraging the nucleophilicity of polysulfide chains, which reacted readily with the electrophilic centers in fluorographene (Fig 1a). The reaction lead to the formation of carbon‑sulfur covalent bonds and a particularly high sulfur content of 80 wt. %. Owing to these features, the developed cathode exhibited excellent performance with only 5 wt. % of conductive carbon additive, delivering very high full‑cathode‑mass capacities and rate capability, combined with superior cycling stability. In combination with a fluorinated ether as electrolyte additive, the capacity persisted at ~700 mAh g−1 after 100 cycles at 0.1 C, and at ~644 mAh g−1 after 250 cycles at 0.2 C, keeping ~470 mAh g−1 even after 500 cycles.[2]
REFERENCES: [1] A. Bhargav, J. He, A. Gupta, A. Manthiram, Joule 2020, 4, 285.; [2] I. Tantis, A. Bakandritsos, D. Zaoralová, M. Medveď, P. Jakubec, J. Havláková, R. Zbořil, M. Otyepka Adv. Funct. Mater. 2021, 2101326.
With the spectacular rise of wearable technologies, R&D on microbatteries is rapidly emerging on the world market. For example, smart electronic textiles require new features and battery designs that traditional battery technologies simply cannot provide. This has opened the door to innovation and added a new dimension to the global competition in battery research.1 The potential sector that can be impacted includes Internet of Things (IoT), healthcare (skin patches, medical sensors, medical diagnostic devices), smart cards, etc. To date, the soft microbattery technology is still in its infancy because it requires the pooling of complementary knowledges in different scientific domains. Indeed, key competences in microelectronics, materials science, electrochemistry, polymer, and inorganic chemistry have to be gathered to overcome all technical challenges. Recently, we have reported a new concept for the development of stretchable Li-ion microbatteries.2-4 A prototype has been also integrated in a scleral eye contact lens5. The innovative approach is based on the assembly of two flexible substrates comprising arrays of micro-pillars on serpentine current collectors that are separated by a polymer electrolyte. These materials eliminate mechanical stress and increase energy performance and battery life. Preliminary results have shown the possibility to power low-consumption devices such as a light emitting diodes.
REFERENCES: [1] M. Nasreldin, S. de Mulatier, R. Delattre, M. Ramuz, T. Djenizian, Flexible and stretchable microbatteries for wearable technologies, Advanced Materials Technologies, Hall of Fame, 2000412 (2020).; [2] T. Djenizian and R. Delattre, « Deformable accumulator », International Patent n° WO 2018/167393 A1, 20-sept-2018.; [3] M. Nasreldin, R. Delattre, B. Marchiori, M. Ramuz, S. Maria, J. L. de Bougrenet de la Tocnaye, T. Djenizian, Microstructured electrodes supported on serpentine interconnects for stretchable electronics, APL Materials, 7, 031507 (2019).; [4] M Nasreldin, R. Delattre, C. Calmes, M. Ramuz, V. A. Sugiawati, S. Maria, J-L de Bougrenet de la Tocnaye, T. Djenizian, High Performance Stretchable Li-ion Microbattery, Energy Storage Materials, 33, 108 (2020).; [5] M. Nasreldin, R. Delattre, M. Ramuz, C. Lahuec, T. Djenizian and J-L de Bougrenet de la Tocnaye, Flexible Micro-Battery for Powering Smart Contact Lens, Sensors, 19, 2062 (2019).
The proper functioning of every solid-state or electrochemical device relies on electrical current flowing through conducting paths. In extreme situations the current density passing through a 2D conductor may irreversibly lead to a morphological change resulting in an open circuit condition and total device failure. High electron fluxes force atoms residing in the conducting material to migrate along the wire in the current flow direction. This electromigration phenomenon is present with different intensities in any electrical device and is enhanced in 2D electrodes due to the small cross-sections through which even low voltages may induce substantial current densities. During high electron fluxes atoms migrate pilling up material close to anode while at the cathodic side voids with increasing size will form. Thus, one way of retarding or even blocking electromigration may be through decreasing void mobility. The current work addresses this issue. A simple approach is described by growth of an anodic oxide affecting the surface mobility of voids. Thin film combinatorial libraries based on Al and Cu were tested for this purpose. Al and Cu 2D test wires were alloyed with Ga in a combinatorial fashion and high throughput experimentation was performed for assessing the influence of the liquid metal atoms on the electromigration process. The dynamics of such electron flux induced atomic movement was modeled and the grain boundaries pinning by Ga was demonstrated. Void mobility is directly affected by immobile grain boundaries. Even though an electrochemical surface treatment via anodization did not prove a clear void pinning effect, the use of small Ga amounts alloyed with Al or Cu resulted in a clear enhancement of resistance against electromigration even in flexible electrodes deposited on polymeric substrates.
Developing ecofriendly, scalable, flexible and non-leaking electrochemical capacitors with good mechanical properties and retaining safety remains a significant challenge in energy storage device. Generally, there is a need to use ecofriendly electrode and electrolyte materials for these devices, which possess mechanical endurance too. Therefore, in this study, environmental friendly materials (cellulose integrated with active materials) have used for the fabrication of full device. We present here a unique approach that demonstrates flexible, ultralight, scalable, binder free and non-leaking energy storage device. The fabricated full device shows excellent electrochemical performance and stability without much deterioration in performance.
Plasma spraying of liquid feedstocks allows deposition of materials from suspensions and solutions. Due to the combination of a liquid carrier and ultrafine powders (suspensions) or in-situ formation of the final material in the plasma jet from solutions, preparation of ultrafine composites is possible, typically in a form of coatings on the substrates. However, preparation of loose nanocomposite powders is also possible. Moreover, both suspension and solution spraying routes may be combined, either together or even with conventional plasma spraying of coarse dry powders, thus merging benefits of “nanometric” and “micrometric” constituents in the final composite microstructure. As a consequence, great variability of the industrially-relevant deposition process may be achieved providing coatings with properties tailored for various applications ranging from compact wear-resistant layers, porous thermal barrier coatings, bio-compatible medical coatings, catalyst carriers, fuel-cells, etc. The presentation will introduce examples of several such coatings recently deposited at IPP CAS using hybrid water-stabilized plasma torch.
3D-printing is an emerging field of technology, known for its quick, scalable and advanced manufacturing technique for electrode fabrication [1]. In a short span of time, this technology has expanded its roots to various fields. Metal plating of 3D-printed nanocarbon electrode (3D-CE) was a successful approach towards electrochemical detection of sugars (glucose and sucrose) at various concentrations [2]. These customized 3D-CE are beneficial for sensing specific molecular targets, and is expected to find ample scope in the future with improvement. In another work, we adopted conventional patterning approach of dip coating 3D-CE, to improve its catalytic properties. This proved to be a fast, cost-effective, binder free approach of coating catalytically active 2D materials such as, transition metal dichalcogenides (TMDs) and MXene, over the 3D-CE conductive substrate. In short, this work showed the possibility of catalytically activating the nanocarbon electrode surface, using various layered 2D materials for energy conversion purposes such as, hydrogen evolution reaction, and broadening its possibilities for various electrochemical applications in the future [3]. Also recently, 3D-printing industry has collaborated with the global health community to address the shortages faced during the COVID-19 pandemic [4]. In short, 3D-priniting technology has significant scope in the coming times, to meet the requirements of everyday life.
REFERENCES: [1] A. Ambrosi, M. Pumera, Chem. Soc. Rev., 2016, 45, 2740-2755.; [2] K.P.A. Kumar, K. Ghosh, O. Alduhaish, M. Pumera, Electrochem. Commun., 2020, 120, 106827.; [3] K.P.A. Kumar, K. Ghosh, O. Alduhaish, M. Pumera, Electrochem. Commun, 2021, 122, 106890.; [4] K.P.A. Kumar, M. Pumera, Adv. Funct. Mater., 2021, 31, 2100450.
Anton Paar is a global manufacturer of scientific equipment used in many different research fields. The product portfolio includes over 70 instruments covering more than 20 different analytical techniques. Material characterization instruments from Anton Paar are well suited for the study and characterization of all types of materials, e.g. thin film drug delivery systems. Surface structure of polymeric drug delivery coating plays an important role on controlled drug release. To get a full picture of the qualitative and quantitative properties, in this case two complementary techniques are used. Namely, atomic force microscopy (AFM) and grazing incidence small angle x-ray scattering (GISAXS). Due to unique integrated measurement workflow of the Tosca 400 AFM, the surface texture and grain size are characterized with unprecedented efficiency, while GISAXS gives a deeper insight into structural changes upon a larger area of the studied thin films. Both methods complement each other in characterizing a drug-delivery system and deliver a full picture of the structural behavior influencing the drug delivery.
Date: October 22, 2021
The bio-waste generated from various sources and their conversion into valuable materials provides extensive research on multiple areas such as energy, water purification, and biomedical. Herein, we propose a detailed study on tree gum biowaste into fibers, films, and sponges and their potential uses in energy harvesting, food packaging, and environmental bioremediation. The study illustrated that the biowaste gum exudates special attention, such as low-cost, non-toxic, biodegradable, and sustainable materials, to fabricate valuable products, characterization, and applications. The primary focus is on preparing activated carbon nano/microstructures, self-standing films, and highly porous sponges via an environmentally friendly approach. Further oil/water separation and organic dyes removal by hierarchically porous sponges, biodegradable food packaging films, and “green” energy harvesting was demonstrated. In the future, intense research is to be carried out to make it economically viable tree gum biowastes, an alternative system, for green and sustainable progress in diverse endeavors.
Microrobots are small-scale motile objects that engineered chemically, physically and/or biologically to exploit their actuation for targeted goals. In the context of environmental remediation, microrobots have ability to critically enhance removal capacities toward harmful contaminants. In this work, we explore activated carbon and titanium dioxide as self-propelled catalytic and light-driven microrobots, respectively. We utilize platinum-decorated activated carbon as a novel autonomous adsorbent towards emerging contaminants. With their active motion, microrobots lead to 3-fold decrease in adsorption time compared to nonmotile conditions. Additionally, the microrobots provide a safe and effective contaminant capture process with regeneration ability up to 3 subsequent cycles.
Furthermore, we investigate the motion of light-driven titanium dioxide microrobots having urchin-like and irregular morphologies. Urchin-like microrobots demonstrate an interesting braking behavior under UV light with switchable motion direction to capture contaminants ‘’on-the-fly’’. However, smooth microrobots do not demonstrate the braking behavior or the change in motion direction at the same conditions. Therefore, these results indicate that the specific design of microrobots has a profound impact on constructing them with on-demand motion capabilities for environmental remediation.
The performance of the next-generation electronic devices based on graphene and other 2D materials is strongly influenced by the structure-function relationship. Scattering-type scanning near-field optical microscopy (s-SNOM) is the ideal technology to investigate such material systems at the nanoscale.
s-SNOM combines the best of two worlds: (i) the high spatial resolution of Atomic Force Microscopy (AFM) and (ii) the analytical power of optical microscopy and spectroscopy. Achieving an unmatched spatial resolution below 10 nanometer this technology opens a new era for modern nano-analytical applications such as chemical identification, free-carrier profiling and plasmonic near-field mapping. Recent research highlights on graphene and other 2D materials include contact-free access to the local conductivity [1], the electron mobility, and the intrinsic electron doping by resolving propagating phonon- plasmon-, and exciton-polariton directly in space and time (Fig.1) [2].
In this presentation we will introduce the basic principles of near-field microscopy for imaging and spectroscopy with 10 nanometer spatial resolution and address their impact and key applications in the field of 2D materials.
REFERENCES: [1] D. N. Basov, M. M. Fogler, F. J. Garcia de Abajo, 2016, Science, 354, 195.; [2] M. A. Huber, F. Mooshammer, M. Plankl, L. Viti, F. Sandner, L. Z. Kastner, T. Frank, J. Fabian, M. S. Vitiello, T. Cocker, R. Huber, Nature Nanotech, 2017, 12, 207.
Copper and lead are considered as heavy metals therefore they are highly toxic even at low dosages and can cause many health issues (e. g. anaemia, encephalopathy, hepatitis). Moreover, they are very common pollutants found in industrial effluents hence their removal is crucial also from the environmental point of view. In recent years, the scientists are focusing on the biosorption as a form of a passive remediation treatment based on the affinity between a biosorbent and an adsorbate.
The main aim of this study was to determine the best parameters for the adsorption of copper and lead ions on Thymus serpyllum L. plant. The effects of contact time, pH and adsorbent dosage were examined. The residual Cu(II) and Pb(II) concentration in filtrates after adsorption was analysed by atomic absorption spectrometry. The highest obtained adsorption capacity for Cu(II) ions was 12.66 mg g-1 at unadjusted pH after 10 minutes and 16 g L-1 adsorbent dosage. In case of Pb(II) ions, the highest adsorption capacity was 53.13 mg g-1 at unadjusted pH after 30 minutes and 12 g L-1 adsorbent dosage. The samples after adsorption were characterized by X-ray diffraction, scanning electron microscopy, thermal analysis and zeta potential measurements. The adsorbed copper and lead were found to be present in a form of the nanocrystalline compounds.
ACKNOWLEDGEMENTS: The work was supported by the Slovak Agency for Science and Development (project no. APVV-18-0357) and by the Slovak Grant Agency VEGA (project no. 2/0044/18) and COST action CA18112: Mechanochemistry for Sustainable Industry.
Nanofiber membranes are made of synthetic polymers mainly by electrospinning technology. The key point for creating a functional nanofiber membrane for water and air filters is to meet basic key properties such as filtration efficiency, mechanical resistance, and resistance to fouling and chemicals.
Design and manufacturing of the advanced nanofiber-based filters urgently require new environment-friendly and cost-effective surface treatments without the use of organic solvents and caustic solutions. To address this need, as an alternative, the atmospheric-pressure plasma treatment offers to be used for surface activation of polymer textile materials serving as a substrate for electrospun nanofiber.
Nanofiber carriers were pre-treated by dielectric barrier discharge in continuous mode to improve the adhesion between the produced nanofibers and substrate. The increased adhesive forces to carrier substrate were confirmed by two peeling tests.
The fact that the robust and effective atmospheric pressure DCSBD technology, primarily developed and optimized for the plasma treatment of textile and fibrous material, can be easily implemented in the industrial production lines predetermines this technology for in-line a large throughput manufacturing of advanced nanofiber-based filters.
ACKNOWLEDGEMENTS: This work was supported by project No. E01-14 funded by the ELIIT initiative.
Green hydrogen and its production are crucial and rapidly evolving topics as they are essential for the emission reduction in transportation, energetics, and chemical industry. Proton Exchange Membrane Water Electrolyzers allow the production of very clean hydrogen without carbon emission. Moreover, they are arguably the most suitable electrolyzers for industrial scale-up, compared to the other types of electrolyzers. The biggest challenge lies in the catalysts for the anodic Oxygen Evolution Reaction (OER) due to the strongly corrosive anodic conditions and high prices of commonly used iridium. One possible solution offers ruthenium: a very active yet unstable OER catalyst. Here we present a complete study of a magnetron sputtered Ir-Ru catalyst, which benefits from the excellent stability of iridium and the high activity of ruthenium at the same time. Surprisingly, only a small amount (25 %) of expensive iridium is needed to achieve a similar performance as a pure iridium catalyst. This effect was thoroughly investigated via various electrochemical methods and surface analysis methods to find the origin of the stabilization effect. Eventually, we used the Ir-Ru catalyst to prepare a low-iridium loading Proton Exchange Membrane Water Electrolyzer with good activity and stability.
High entropy alloys (HEAs) are multicomponent materials with at least five elements close to the equiatomic ratio. The multielement composition leads to many effects that stabilize solid solution phases instead of intermetallic compounds. It results in promising mechanical properties, high thermal stability, good corrosion resistance, etc. After the discovery of HEAs in 2004, the concept only concerned metallic materials. Later, the idea was extended to high entropy ceramics (carbides, nitrides, oxides). In this study, the high entropy nitrides (HENs) from the Cr-Hf-Mo-Ta-W system were deposited by magnetron sputtering from the elemental segmented targets. Two series of samples were deposited under different nitrogen flow from 0 sccm to 20 sccm at room temperature and 700 °C. The coatings deposited at low nitrogen flow consist predominantly of metallic and amorphous phases. At higher nitrogen flow (above 10 sccm), the coatings mainly consist of multielement face-centered cubic nitride with nanometric grain size, which lattice parameter increases with increasing nitrogen content. The chemical composition of films varies as a function of nitrogen flow and temperature. With increasing nitrogen flow and temperature, the deposition rate decreases from 67 nm min-1 at room temperature with no nitrogen to 38 nm min 1 at 700 °C under 20 sccm nitrogen flow. The coatings revealed very high hardness up to 26.6 GPa and Young’s modulus up to 531 GPa.
2D materials are among the most promising materials nowadays. Thus, considerable attention is devoted to studying these materials. Their unique properties are highly determined by the number of layers and their stacking sequence. Although the above-mentioned parameters have a clear driving role in the control of these properties, there was no technique able to reliably investigate stacking sequence nor number of layers.
As a novel approach dealing with this issue the multiwavelength electron diffraction has been proposed by prof. Piazza's research group. [1] As a part of this method, LVEMs are the only commercially available instruments able to provide essential information coming from electrons of low energy suitable for this method.
In addition to all imaging modes of LVEM5D devices, their analytical capabilities of diffraction mode can be used to obtain complementary information to diffraction patterns from conventional TEMs. Only such comprehensive information about the spot intensities and intensity ratios in diffraction patterns, while varying the electron energy, reveals more about the number of layers and stacking sequence of 2D materials. [2]
The method has been applied to graphene and graphene-based material Diamane and Diamanoid [3] - a new generation of wide band-gap semiconductors for electronics, photonics, and medical devices. Thanks to the aforementioned method the different configurations were evidenced in the specimens.
REFERENCES: [1] Puech P., Gerber I.C., Piazza, F. et al. Combining low and high electron energy diffractions as a powerful tool for studying 2D materials. Appl. Phys. A 127, 485 (2021). https://doi.org/10.1007/s00339-021-04568-9.; [2] Puech P., Gerber I.C., Piazza F., Monthioux M. Multiwavelength electron diffraction as a tool for identifying stacking sequences in 2D materials. Marc. (2020).; [3] Piazza F., Monthioux M., Puech P., Gerber I.C., Gough K. Progress on Diamane and Diamanoid Thin Film Pressureless Synthesis. C (2021). https://doi.org/10.3390/c7010009.
Date: October 22, 2021
Platinum group metals such as Pt, Ru, Pd, Ir etc., have superior performance in the field of catalysis.[1] Due to their scarcity efforts were being made to reduce or replace these noble metals. Atomic Layer Deposition (ALD) is one among the best technique that is available to reduce the metal loading of noble metals.[2],[3]
TiO2NT had received a great attention form applied fields such as photocatalysis, electrocatalysis, photovoltaics and biomedical fields considering their high surface area, conductivity and stability.[4],[5] Anodic oxidation of titanium foils using relevant electrolytes is one of the appropriate method to fabricate TiO2NT.[6] Uniformly decorating these NT by nanoparticles or thin films of catalyst proved to be highly efficient in several electrocatalytic applications.[7] ALD is the leading tool that can decorate high aspect ratio nano architectures.[8]
The presentation has a detailed description of different noble metal depositions by our ALD tool (Beneq TFS 200) on various aspect ratio TiO2NT’s. It also includes recent results of decorated TiO2NT for different applications.
REFERENCES: [1] Huang, Z. F. et al. Advanced Energy Materials vol. 7 (2017).; [2] Yoo, J. E. et al. Electrochem. commun. 86, (2018) 6.; [3] Anitha, V. C. et al. J. Catal. 365, (2018) 86.; [4] Sopha, H. et al. Appl. Mater. Today 9, (2017) 104.; [5] Macak, J. M., Zlamal, M., Krysa, J. & Schmuki, P. Small 3, (2007) 300.; [6] Macak, J. M. et al. Curr. Opin. Solid State Mater. Sci. 11, (2007) 3.; [7] Dvorak, F. et al. Appl. Mater. Today 14, (2019) 1.; [8] Zazpe, R. et al. Langmuir 32, (2016) 10551.
Nanocrystalline oxide of composition Yb3Ga5O12 belongs to the family of materials with garnet-related structure. It is a promising material with potential applications in the field of photonics when doped by lanthanides such as Er3+ or Ho3+. High content of Yb3+ ions in the Yb15−xErxGa25O60 and Yb15−xHoxGa25O60 hosts allows efficient excitation using ≈980 nm laser. This leads to sensitized energy transfer upconversion photoluminescence emission in visible region.
Nanophosphors of compositions Yb15−xErxGa25O60 and Yb15−xHoxGa25O60 (with x = 0; 0.01; 0.1; 0.5; 1; 2) were prepared by sol-gel combustion technique using citric acid as chelation agent. Phase composition and morphology of annealed products were examined by X-ray diffraction and by scanning electron microscopy. Diffuse reflectance spectroscopy was used for determination of absorption bands associated with the presence of lanthanide ions. Energy transfer from Yb3+ to Er3+/Ho3+ ions is provided by photoluminescence spectroscopy leading to dominant red/green emission bands. Possible upconversion mechanisms are proposed using energy level diagrams.
ACKNOWLEDGEMENTS: The author thanks for financial support from the grant of the Ministry of Education, Youth and Sports of Czech Republic (grant LM2018103), the European Regional Development Fund-Project “Modernization and upgrade of the CEMNAT” (No.CZ.02.1.01/0.0/0.0/16_013/0001829), the project NANOMAT CZ.02.1.01/0.0/0.0/17_048/0007376 and the project of Faculty of Chemical Technology, University of Pardubice „Excellent teams“ 2020.
Colloidal solutions of metal nanoparticles (NPs) are typically produced by multi-step methods with the use of a variety of chemicals. Resultant nanofluids require extra purification steps to remove the reactions by-products and/or modification steps to introduce anticoagulants for the solution stabilization. Here, we suggest a single-step method to produce nanofluid in which only two components are present: Cu NPs and polyethylene glycol (PEG, 400 g/mol). The method employs magnetron sputtering for the synthesis of Cu NPs in a gas aggregation cluster source and their subsequent loading into vacuum-compatible PEG. Cu NPs undergo coagulation when in PEG, with the formation of larger aggregates that scatter light, making the solution highly turbid and greyish. However, the aggregates eventually disintegrate into the constituent 22 ± 2 nm NPs, confirmed by in-situ liquid cell TEM and SAXS measurements. The environmental XPS was employed directly on the nanofluids to reveal the absence of copper oxidation. The resultant nanofluids become transparent and colorized green, demonstrating intense plasmonic and photoluminescent (PL) activity, with localized particle plasmon resonance at a wavelength of 630 nm and PL at 422 nm. The approach offers an alternative for the production of nanofluids, in which the processes of the NP formation are decoupled from the processes of their mixing with the liquid base. The method also opens the way to the production of even more complex nanofluids combining, for example, NPs of different metals, multi-component NPs (core@shell, Janus, nanoalloys), or hybrid organic/inorganic NPs.
ACKNOWLEDGEMENTS: The work was supported via the grant GACR 21-12828S from the Czech Science Foundation. R.T., K.B. and M.P. also appreciate the support from Charles University via a student grant SVV 260 579-2021.
Gold atom clusters (AuAC) with diameters smaller 2 nm are a frequently studied class of nanomaterials with interesting optical properties with discrete atom-like transitions and related photoluminescence. However, they can to date just be synthesized in the presence of organic surface ligands. Hence, the origin of the observed photoluminescence (from metal core or ligand) is to date unknown. In this study we present an entirely new class of fully inorganic AuAC available by laser fragmentation in liquids (LFL). We used LFL on plasmonic gold nanoparticles to obtain AuAC in an advanced liquid jet reactor and show to what extent the adjustment of the incident fluence [1] as well as the addition of anions at micromolar salinity [2] allows to significantly increase the yield of AuAC with diameters < 3 nm following a one step, one pulse fragmentation mechanism. The optical properties of the obtained AuAC are studied using UV-Vis spectroscopy as well as time-resolved fluorescence spectroscopy. The clusters show a distinctive UV fluorescence with two distinctive emission maxima associated with surface-based and core-based transition states. Finally, we observed that charging the AuAC surface by addition of hydroxide anions (alkaline pH) has a pronounced impact on the emission intensity, which verifies a clear impact of charge transfer effects on the AuAC´s electronic structure[3].
REFERENCES: [1] A. R. Ziefuss, S. Reichenberger, C. Rehbock, I. Chakraborty, M. Gharib, W. J. Parak, S. Barcikowski, Journal of Physical Chemistry C 2018, 122, 22125-22136.; [2] A. R. Ziefuss, S. Barcikowski, C. Rehbock, Langmuir 2019, 35, 6630-6639.; [3] A. R. Ziefuss, T. Steenbock, D. Benner, A. Plech, J. Gottlicher, M. Teubner, B. Grimm-Lebsanft, C. Rehbock, C. Comby-Zerbino, R. Antoine, D. Amans, I. Chakraborty, G. Bester, M. Nachev, B. Sures, M. Rubhausen, W. J. Parak, S. Barcikowski, Advanced Materials 2021.DOI: 10.1002/adma.202101549.
In heterogeneous catalysis, unique nanoparticles’ properties, especially a high percentage of surface atoms, are highly desired. Copper nanoparticles are active in (bio)ethanol dehydrogenation producing acetaldehyde. This catalytic reaction presents the first step in 1,3-butadiene production from ethanol and could become a sustainable substitution for current acetaldehyde and butadiene production (based on oil refinement).
This research project deals with various copper and copper-nickel silica-supported nanoparticles synthesized by different methods: solvothermal hot-injection, dry impregnation, electrostatic impregnation, hydrolytic and non-hydrolytic sol-gel. Various synthetic methods offer metal nanoparticles with different morphologies, sizes (from atomic dispersion to 20 nm), and particle size distributions. Several techniques were used to study these catalysts: scanning transmission electron microscopy combined with electron dispersive spectroscopy, nitrogen porosimetry, thermogravimetry, x-ray photoelectron spectroscopy, and inductively coupled plasma atomic emission spectroscopy. The catalytic performance of prepared catalysts was tested in the ethanol dehydrogenation in a gas-phase fixed-bed catalytic reactor. Light-off catalyst curves were established from 180 °C to 290 °C; stability with time-on-stream was tested at 325 °C for 10 hours. Copper nanoparticles are highly active and selective in the desired reaction (up to 89 % ethanol conversion at 250 °C) but suffer from coking and particle sintering, hampering their long-term stability. Nickel addition enhanced low-temperature catalyst performance. However, the catalyst’s stability needs to be further improved.
ACKNOWLEDGEMENTS: The work has been financially supported by the Czech Science Foundation under the project GJ20-03636Y.