Seznam abstraktů 2024: SEKCE A - NANOMATERIÁLY PRO ELEKTRONICKÉ, MAGNETICKÉ A OPTICKÉ APLIKACE. UHLÍKOVÉ NANOSTRUKTURY, KVANTOVÉ TEČKY

This presentation will focus on the application of advanced ultrafast laser-based techniques for the synthesis and diagnostics of 2D materials and their nanoelectronic device components. Specifically, the pulsed laser assisted fabrication of transparent graphene electrodes and interlayers for photovoltaic devices, is demonstrated. Furthermore, we present a fast, non-destructive and roll-to-roll compatible photochemical method for the doping of graphene and transition metal dichalcogenide (TMD) crystals. In the second part, we present an all-optical, non-invasive ultrafast laser-scanning microscopy method to resolve the crystallographic imperfections of atomically thin TMD nanocrystals, via experimentally probing and theoretically interpreting their nonlinear optical properties. In particular, we show that polarization resolved second harmonic generation (PSHG) imaging reveals with high-precision a pixel-by-pixel mapping of the armchair orientations on a CVD-grown TMD sample. This allows us to measure the mean orientational average of armchair angle distributions from specific regions of interest and consequently to define the standard deviation of these distributions as a crystal quality factor. Furthermore, the same method can be used to optically identify the twist angle in stacked layers of different armchair orientation. We envisage our methodology as a new tool for the discovery of new phenomena in twisted 2D layers employed in the future nanoelectronic devices.

Graphene oxide is a carbonaceous material that has unique physicochemical properties (specific surface area, pollution resistance, conductivity, high mechanical strength) and can be produced in large quantities with relative ease. It is a material formed by the oxidation of graphene, which can be further modified with, for example, ascorbic acid to form reduced graphene oxide (rGO), or with hydrogen peroxide to form holey graphene oxide (HGO). The application of graphene oxide and its modifications in processes leads to improved sensitivity, electrocatalytic behaviour and reduced fouling. Thus, a kampron, which is an electronic component with graphene oxide derivatives fabricated using 3D printing technology, has been experimentally prepared with the advantage of applications in various fields - physical, chemical and biological. Graphene oxide in the form of filaments will be used for 3D printing. Thus, in several stages, the action in the physical domain (pressure), chemical domain (gases and vapours) and biological domain (gases exhaled from the lungs) will be investigated. The changes caused by the investigated influences on the sensors are reflected by a change in the voltage on the sensor. This paper focuses on the first stage of the research, i.e. the fabrication and verification of reactivity of sensors printed in a single layer, which are similar to conventional comb or spiral sensors. The next stages of the research will focus on the investigation of sensors arranged in multiple layers, with the final stage involving the preparation of sensors with complex spatial shapes, while higher sensitivity is also expected.

Amine plasma polymer (PP) films are thin coatings created through the plasma polymerization of amine-containing monomers or from the mixture of nitrogen-containing and hydrocarbon gases. They can be prepared under various plasma conditions with varying nitrogen content, functional groups, and cross-linking. They have shown potential applications in biomolecule immobilization for biosensors or improved cell viability in tissue engineering. Previously, we have investigated the bioapplication of such films deposited from a mixture of cyclopropylamine and argon in a low-pressure (50 Pa) radio frequency plasma discharge. Generally, amine PPs are considered amorphous, but our recent discovery revealed that they might contain crystalline domains. We proved it for the film deposited at 30 W in the pulsed mode because of its partial solubility in water (around 18% of the film thickness was reduced after immersion in water for 216 hrs) that enabled the extraction of the crystalline particles from the film. The extract contained particles with a 5-15 nm diameter determined by dynamic light scattering and atomic force microscopy. High-resolution transmission electron microscopy proved that the nanoparticles are graphitic. The fluorescence spectra of these particles revealed excitation-dependent emission for excitation wavelengths from 300 to 500 nm. When the human monocyte cells (THP 1) were cultivated on the partially soluble amine PP film, they had a higher fluorescence signal than the corresponding control plates of THP 1. Thus, we concluded that the cells uptake the particles.

In people's daily life, energy storage is one of the most important topics of scientific research today [1] due to the use of small-size batteries in watches, phones, computers, and large supercapacitors / batteries in cars, etc. Reduced graphene oxide (rGO) is a promising material for improving the structural and electrochemical properties of capacitive electrodes of energy storage devices [2]. In addition, the rGO aerogel, which is lightweight and can exhibit a large surface area, is a more promising material for energy storage compared to the dense rGO membranes obtained by vacuum filtration. At the same time, the process of preparing rGO, as well as composite materials based on rGO, plays a significant role in the final characteristics of the material and the device. Dense free-standing rGO electrodes obtained by vacuum filtration are compared with composite electrodes made from rGO powder or aerorgel on a different substrate.
ACKNOWLEDGEMENT: O.O. thanks for support the projects PTDC/EME-REN/1497/2021 “Power Phoenix Battery - A Full Solid State Grid-scale Storage Solution”; UIDB/00481/2020 and UIDP/00481/2020 - Fundação para a Ciência e a Tecnologia, DOI 10.54499/UIDB/00481/2020 (https://doi.org/10.54499/UIDB/00481/2020) and DOI 10.54499/UIDP/00481/2020 (https://doi.org/10.54499/UIDP/00481/2020); CENTRO-01-0145-FEDER-022083 - Centro Portugal Regional Operational Programme (Centro2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund.
REFERENCES: [1] J. Mitali, S. Dhinakaran, A.A. Mohamad, Energy Storage and Saving, 1, 166-216, (2022); [2] S.M. Mousavi, S. A. Hashemi, M.Y. Kalashgrani, A.Gholami, M. Binazadeh, W.-H. Chiang, M.M. Rahman, Sustainable Energy Fuels, 7, 5176-5197 (2023)

Plasma polymers, i.e., macromolecular solids created during a passage of molecular fragments or precursors through a plasma, represent a unique class of materials with a broad range of applications. Although these materials are traditionally prepared in the form of thin films, our recent studies proved the possibility of producing also plasma polymer nanoparticles. This may be achieved using gas aggregation sources based on a magnetron sputtering of a polymeric target. In these sources, plasma polymer nanoparticles are formed due to the spontaneous gas-phase nucleation of sputtered molecular fragments in the aggregation chamber at increased pressure (~ 100 Pa). As reviewed in this study, this approach is applicable to produce various types of plasma polymer nanoparticles with tailor-made sizes, shapes or chemical compositions by variation of the deposition conditions (i.e., target material, working gas composition, aggregation pressure, applied power, etc.). However, a new phenomenon unique to nanoparticle deposition must also be accounted for: the re-bouncing of nanoparticles from a substrate caused by their relatively high speed upon landing on a substrate and their mechanical properties. As shown, this adverse effect may be overcome either by the adjustment of the pressure in the deposition chamber or by the use of a suitable structured substrate.
ACKNOWLEDGEMENTS: This work was supported by grant 24-12197S from the Czech Science Foundation.

This study presents a novel technique for polymerizing aniline (monomer) to form Polyaniline (PANI) films. PANI films were prepared via acid-assisted polymerization with concentrated formic acid in the presence of ethanol and ammonium peroxydisulfate (APS) at room temperature. Using this method, two PANI films were prepared with different APS ratios (10:1 for PANI 1 and 5:1 for PANI 2). After the synthesis, PANI was deposited on glassy carbon (GC) electrode to form PANI/GC heterostructures. We investigated the morphologies of the PANI films using SEM measurements, which revealed distinct structures: a nanofibrillar porous structure for PANI 1 and a densely packed arrangement for PANI 2. The electrochemical performance of the fabricated PANI/GC electrodes was evaluated using a three-electrode cell configuration in the scan rates ranging from 10 mV/s to 100 mV/s. Data analysis indicates that the morphology of the PANI structure significantly influenced the oxidation/reduction characteristics, which were modulated with GC characteristics. The PANI 1 /GC heterostructure exhibited a specific capacitance of 160 F/g, while this value increased to 407 for the PANI 2/GC. This study highlights the role of PANI structure and conductive support, providing valuable insights for the development of advanced energy storage materials.

We have performed a combined theoretical and experimental study of FeSn2 intermetallics. We were motivated by a scarcity of published data as well as previous theoretical calculations of the antiferromagnetic (AFM) state of FeSn2, when this compound was found mechanically unstable due to imaginary-frequency phonons, i.e., effectively denying the existence of FeSn2. Addressing both mechanical and thermodynamic stability within density-functional theory (DFT) calculations, we focused on the AFM state as well as the ferromagnetic (FM) state of FeSn2, which were both considered in earlier experiments. In contrast to the previous calculations, we found the AFM FeSn2 state mechanically stable (no imaginary-frequency phonons). The same is true for the FM state, which possesses a slightly higher energy than the AFM state. The mechanical stability allowed for assessing the thermodynamic properties within both harmonic approximations as well as computationally much more demanding quasi-harmonic approximation. Interestingly, while the static-lattice formation energy of AFM FeSn2 is negative and, therefore, the compound is predicted stable with respect to the decomposition into elemental end-members, phonon-related contributions have a destabilizing impact at low temperatures. Our calculations were complemented by experimental characterization of Fe-Sn samples and the experimental FeSn2 lattice parameters were found in excellent agreement with theoretical values.
ACKNOWLEDGEMENTS: M.F., P.Č ., P.R., O.S., D.F., Š.M. and A.M. acknowledge the Czech Science Foundation for the financial support received under Project No. 22-05801S. We also acknowledge computational resources provided by the Ministry of Education, Youth and Sports of the Czech Republic under the Projects e-INFRA CZ (ID:90254) at the IT4Innovations National Supercomputing Center and e-Infrastruktura CZ (e-INFRA LM2018140) at the MetaCentrum as well as CERIT Scientific Cloud, all provided within the program Projects of Large Research, Development and Innovations Infrastructures.

Ternary nitride coatings (Ti₁₋ₓAlₓN) were synthesized by varying the aluminum content, and their crystal structures and morphologies were analyzed. The Ti₁₋ₓAlₓN coatings were deposited on cemented carbide substrates under pulsed bias conditions of -30 V, -60 V, and - 300 V (duty cycle 10%) with different compositions. Additionally, a series of samples were deposited with a -300 V pulsed bias, but with a duty cycle of 20%. The chamber pressure was at 4.5 Pa (N₂) for all samples. XRD analysis showed that the crystal structure of Ti₁₋ₓAlₓN coatings transitioned from a NaCl-type (cubic structure; c-) to a wurtzite-type (hexagonal structure; h- ) as the aluminum content increased to X=0.6-0.7. All coatings have a columnar structure. The pulsed bias resulted in a rough surface. The profilometer measurements showed an increase in surface roughness (Sa) from 0.16 μm to approximately 0.26 μm as the aluminum content increased, likely due to 3D growth as columnar grains reached the coating surface. However, increasing the duty cycle to 20% reduced the roughness (Sa ≈ 0.15-0.16 μm), and this roughness remained nearly constant with increasing Al content.

Scintillators transform high-energy ionizing radiation into the easily detected photons. Semiconductor CsPbBr3-like (CPB) aggregates with narrow bandgap (about 2.5 eV) possess very fast (hundreds of picoseconds) and strong free exciton luminescence (green at the nanoscale). CPB grown on ZnO microrods showed improved photoluminescence by an order of magnitude. Calculations by density functional theory (DFT) methods could be used to understand and predict the properties of the CPB nanocrystals on ZnO surfaces.
Thus, in this study the behavior of the CPB nanocrystals on the surface of ZnO, considering polar and non-polar surfaces was investigated by DFT methods. We designed model of nanoscale slabs of ZnO and CPB clusters with oleic ligands (OA, OAm) of 155 atoms in overall size. We employed force field molecular dynamics (FFMD) and density functional tight binding simulations (DFTB). The results of polar surfaces (Zn-face ([0001] or O-face [0001 ̅]) surfaces and non-polar surfaces ((101 ̅0) and (112 ̅0) oriented) were compared. We observed that interparticle charge transfer barrier exists due to the steric hindrance when the CPB are furnished with unoptimized surfaces or ligands configurations, leading to inefficient interparticle energy transfer and limited photocatalytic performance. We show that properly designed ligands enable the exciton wave function to extend into the interfacial region, leading to a significant electron density redistribution at the ligand-CPB interface. Influence of specific properties of particular ZnO surface facettes is also presented and discussed.

The zeta potential of a surface is an important property that determines the electrostatic interactions between a material surface and the surrounding environment. A distinctive and incompletely understood phenomenon is the positive zeta potential observed when hydrogenated diamond nanoparticles (nanodiamonds; NDs) are introduced to water. In contrast, the zeta potential of the hydrogenated single-crystalline diamond surface was reported to be negative at close-to-neutral pH [1]. The Kelvin probe is used to measure surface potential, which provides another important surface characteristic related to the work function of a material. A more profound comprehension of the interrelationship between zeta and surface potentials may bring a more complete understanding of material surface properties. The present study investigates and compares the zeta and surface potentials of hydrogenated diamond surfaces with a different topology, nanoparticles and nanocrystalline diamond (NCD) layers. The hydrogenated detonation NDs were obtained by annealing in the hydrogen gas at 500-1000°C. The NCD layers were grown on silicon substrates via plasma-enhanced chemical vapor deposition and subsequently exposed to hydrogen or oxygen plasma to ensure hydrogen or oxygen surface terminations, respectively. The results demonstrate that the NDs zeta potential, determined by the electrophoretic light scattering technique, is consistently positive across the entire hydrogenation temperature range. Furthermore, a strong correlation is observed between the zeta and surface potential, as measured by the Kelvin probe. In contrast, the zeta potential of hydrogenated NCD layers, measured by the streaming potential technique, was negative in the slightly acidic to basic pH ranges with an isoelectric point below pH = 3 and its correlation with the Kelvin probe was less obvious. Finally, we discuss possible material and methodological factors that could contribute to the observed discrepancies in zeta potential, such as sp2 carbon or structural defects, and propose new approaches to understand these phenomena better.
REFERENCES: [1] A. Härtl, J.A. Garrido, S. Nowy, R. Zimmermann, C. Werner, D. Horinek, R. Netz, M. Stutzmann, The Ion Sensitivity of Surface Conductive Single Crystalline Diamond, J. Am. Chem. Soc. 129 (2007) 1287-1292. https://doi.org/10.1021/ja066543b.

We have developed CdSe/CdZnS colloidal quantum dots (QDs) within perovskite (MAPbX3 (X=Cl, Br)) thin film matrices using a soft-chemistry method [1,2].
At room temperature (300 K), we successfully demonstrated single-photon emission from a single CdSe/CdZnS QD-in-perovskite hybrid through antibunching measurements, confirming that the quantum yield remained largely unaffected by the soft-chemistry process.
At cryogenic temperatures (4 K), we identified two spatially-dependent emission mechanisms (down to the micrometer scale) within the MAPbBr3 matrix: direct excitonic recombination and long-lived shallow trap emission, following a truncated 2D Förster resonant transfer model [3].
After a halide exchange process (replacing Br with Cl) on MAPbBr3 thin films doped with CdSe/CdZnS QDs, we obtained QDs within MAPbClxBr3-x tunable bandgap materials. At 4 K, we could optically address single QDs, achieving state-of-the-art narrow emission linewidths and deterministic single charge control of individual QDs in MAPbCl3 matrices through an optical gate.
These findings pave the way for the development of QD-in-perovskite field-effect devices for single-photon applications, based on soft chemistry processes with CdSe/CdZnS colloidal QDs.
REFERENCES: [1] J. Baronnier et. al., Nanoscale 14, 5769-5781 (2022); [2] J. Baronnier et. al., Phys. Chem. Chem. Phys. 23, 22750-22759 (2021); [3] J. Baronnier et al., Nanomaterials 13, 2376 (2023).

Non-stoichiometric molybdenum oxides emerged as potent tools in optoelectronics, providing tunable optical properties and energy-conversion capabilities at very favorable cost. In our previous work, we reported the possibility to control the optoelectronic properties by changing temperature during an original short microwave-assisted synthesis. The changes in optical properties were not caused by varying size or shape of produced nanoparticles, but through modulation of their chemical structure confirmed by Fourier-transform infrared spectroscopy. We understand this process as defect engineering of oxygen vacancies in MoOX structure. In this work, it is further explored by energy-resolved electrochemical impedance spectroscopy (ER-EIS), by means of UV-vis-NIR and imaging confocal Raman spectroscopy complemented by X-ray photoelectron spectroscopy (XPS). We observed changes in density of electronic states by applying ER-EIS and prove subsequent modification of optical properties during the process. The optical and Raman response is compared to different MoOX clusters prepared by either microwave-assisted synthesis or previously reported liquid-phase exfoliation method. Our results highlight the potential in preparation of tailored MoOX structures with desired optical response but also point out a possibly adverse phenomena which could interfere with the optoelectronical performance of such a device. This knowledge contributes to development of new polyoxomolybdate-based materials in various applications including photothermal therapy, microelectronics or energy conversion and storage.
ACKNOWLEDGEMENT: This work was supported by the Slovak Research and Development Agency contract No. APVV-20-0485, SK-FR-22-0012 and by the Slovak Grant Agency for Science under contract No. VEGA 2/0117/22.

Two-Photon Lithography (TPL) represents one of the most promising nanofabrication technologies for manufacturing highly precise and complex three-dimensional objects. Although TPL offers significant potential in both laboratory and industrial applications, achieving a substantial increase in writing speed while maintaining high accuracy still remains challenging. In this context, an advanced TPL platform is presented, utilizing a combination of an inertia-free acousto-optic scanner (AOD) and a flying stage to significantly accelerate the writing process. With our approach, utilizing the AOD system, we demonstrate the possibility of achieving very high fabrication speeds on the order of several 10^6 voxels/s while maintaining high resolution. To validate our AOD-enabled TPL system, we present examples of printing on several objects from the fields of micro-optics, mechanical metamaterials, and bioscaffolds that confirm achieved writing speed and resolution. The presented results show that our method provides a promising solution for high-speed 3D nanofabrication across various application areas and beyond laboratory use.

The popularity of the nanosystems containing zinc oxide (ZnO) is rapidly raising. Therefore, ZnO-based nanostructures appear on top of the world-wide R&D. In particular, wide bandgap reaching value of about 3.3-3.5 eV, high exciton binding energy of about 60 meV and fast timing of luminescence (decay time is ~400-500 ps in the case of excitonic emission) make it attractive for the time-of-flight (TOF) applications like TOF positron emission tomography, especially in combination with other materials such as CsPbBr3. Another scientific and industrial branch where ZnO and/or CsPbBr3 can find use is renewable sources of energy like solar cells. It is known that luminescence as well as charge carriers transport can be moderated by doping with different ions and/or post-growth treatment including annealing in different atmospheres and exposure to plasma. Doping with erbium, annealing in air and separate hydrogen plasma treatment are the efficient tools for the ZnO properties moderation. However, there is lack of information about simultaneous doping with Er at higher concentrations (1-30%) and hydrogen plasma treatment, especially when combined with the preceding annealing in air. Therefore, the aim of the current work is to address these important points in order to improve the efficiency of luminescence processes inside ZnO nano- and microrod.
ACKNOWLEDGEMENTS: The financial support of the Czech Science Foundation project No. 24-12872S and the program “Strategy AV 21” of the Czech Academy of Sciences, specifically work package VP 27 Sustainable Energy (Renewable energy resources and distributed energy systems) are gratefully acknowledged.

In recent years, there is a growing interest in the rapid and selective sensing of neurotransmitters such as kynurenine-type molecules. Neurotransmitters from the kynurenine pathway can be involved in many pathological processes in the immune and nervous systems in a concentration-dependent manner. Fluorescence sensing is a simple and effective method compared to complicated instrumental techniques, and utilizing metallic nanoclusters with good fluorescence properties can be an alternative to quantum dots or fluorescent dyes.
The aim of our research was to prepare bimetallic silver/gold nanoclusters as fluorescent probes for the identification of kynurenine pathway molecules. Human apo-transferrin and γ-globulin were used as reducing and stabilizing agents, and synthesis parameters (e.g. silver to gold ratio, temperature) were optimized to achieve high fluorescence and kinetic stability. The prepared nanoclusters were characterized using instrumental techniques to determine their size, metal content, oxidation state and protein secondary structure, furthermore their behavior in high ionic strength environments and at different pH (1-13) was also investigated. Subsequently the nanoclusters were tested with different kynurenine pathway molecules to check their selectivity, and the interaction with the selected molecules were studied to determine the reaction kinetics. In the case of γ-globulin-stabilized bimetallic nanoclusters, the effect of the introduced silver atoms on colloidal, optical and sensing characteristics were determined.
ACKNOWLEDGEMENT: Project no TKP2021-EGA-32 has been implemented with the support provided by the Ministry of Culture and Innovation of Hungary from the National Research, Development and Innovation Fund, financed under the TKP2021-EGA funding scheme.

There are two perspective materials which are planned to be combined as a composite for efficient and ultrafast radiation conversion in scintillator detectors, perovskites and zinc oxide. Perovskites are optically active materials with high light-absorption coefficients, intrinsic defect tolerance, and size-tunable optoelectronic properties. Zinc oxide (ZnO) is a direct bandgap semiconductor that has gained significant importance in optical, electrical, and optoelectronic applications. Prior works indicate that increased photoluminescence yield and electron transport may be achieved in such composite systems [Journal of Luminescence 239 (2021) 118396].
In this work, we study the structural and electronic properties of nanocomposite structure of CsPbBr3 (CPB) nanocrystals on different ZnO substrates: 0001-Zn face and 0001-O face with polar surfaces, 1010 and 1120 with non-polar surfaces. The material structure was characterized by scanning electron microscopy (SEM) in the secondary (SE) and backscattered (BSE) electron mode. Nanocomposite work function (WF) and time-resolved surface photovoltage (SPV) were studied by scanning Kelvin Probe (SKP) in the dark and under a solar simulator or UV illumination. Confocal photoluminescence (PL) micro-spectroscopy was used to characterize PL emission spectra and their spatially resolved maps. SEM images and PL maps showed different distribution, shape and agglomeration of the CPB nanocrystals on the different ZnO substrates. Uniform film with well-defined CPB microcrystals grew on polar 0001 Zn-face surface, showing also clearly resolvable crystals in the PL maps. Smaller cubic CPB crystallites were observed on non-polar 1010 ZnO surface, exhibiting diffuse PL maps. PL and SEM analyses showed an overall weak CPB adhesion and localized CPB crystals and PL spots on ZnO with both polar O-face and non-polar 1120 surface. These differences were also manifested in the CPB/ZnO optoelectronic properties. The work function of the bare reference ZnO samples was around 4.7 eV. After CPB deposition, the WF increased between 4.79 to 5.34 eV depending on the ZnO orientation. SPV was generally positive from 30 to 430 mV, thus, holes were generated (or transported) to the CPB. The exception was again the 0001 Zn-face surface, where CPB crystals exhibited negative SPV -40 to -70 mV, i.e. electrons being concentrated on CPB. CPB PL peak remained between 525 - 527 nm (with ZnO PL suppressed in the composite) whereas its intensity changed significantly depending on ZnO crystal orientation. Obviously both the ZnO surface polarity and surface chemistry are controlling the CPB growth and opto-electronic properties on ZnO crystal planes. This may be crucial for prospective nanoscintillator detector applications. Authors gratefully acknowledge the financial support from the Czech Science Foundation project No. 24-12872S and the program “Strategy AV 21” of the Czech Academy of Sciences, specifically work package VP 27 (Renewable energy resources and distributed energy systems).

Recent advances in the performance of perovskite solar cells (PSCs) have been strongly linked to advancements in interfacial engineering and the development of charge-selective contact. Self-assembled monolayers (SAMs) play an important role in inverted PSCs due to their distinctive and versatile ability to manipulate chemical and physical interface properties. Here we compared the dipole moments of (2-(9H-carbazol-9-yl)ethyl)phosphonic acid (2PACz), (4-(3,6-Dimethyl-9H-carbazol-9-yl)butyl)phosphonic acid (Me-4PACz), (4-(3,6-Dimethoxy-9H-carbazol-9-yl)butyl)phosphonic acid (MeO-4PACz), and (2-(3,7-Dibromo-10H-phenothiazin-10-yl)ethyl)phosphonic acid (Br-2EPT) molecules and their impact on the energy conversion of PSC devices. Additionally, we simulated the dipole moment and surface charge effect device behavior to support our hypothesis. Finally, we observed that the fill factor behavior in both devices and simulations exhibited a similar trend, which correlated with the dipole moment of SAMs.

Optimization of the surface and interface properties of hybrid perovskite optoelectronic devices is crucial for achieving both high performance and long-term stability. In this presentation, I would like to outline a number of straightforward and promising molecular engineering for enhancing the performance and stability of perovskite solar cells (PeSC) and self-powered perovskite photodetectors (PePD). Particularly, through optical simulation based on fast computing system, rational design of optimal device architecture for high-performance all-perovskite tandem solar cells is manifested. In addition, I will talk about how to lean on the experience in molecular engineering to realize high-performance and ultra-stable self-powered PePD, with specific focus on the development of novel multi-functional low band-gap polymer DPP-CNTVT. Finally, I will showcase an innovative perovskite-based energy harvesting system that is particularly suitable for use under shadow conditions, offering great potential as a new solution for energy scavenging in a variety of application scenarios. Our findings offer valuable insights for the development of high-performance and long-term stable PeSC and self-powered PePD, marking a significant milestone in these fields and representing a major step towards the practical application of these emerging technologies.

The quest to imbue semiconductor materials with magnetic properties has been a topic of significant interest over the past two decades. Traditionally, research has focused on applying magnetic semiconductors to spintronic devices. However, semiconductors also play a crucial role as catalysts. Recently, there has been growing interest in whether magnetic semiconductor catalysts can enhance their catalytic efficiency through the application of magnetic fields. The key to developing such materials lies not in the magnitude of their magnetism but in whether doping or defect engineering can induce spin-polarized energy bands in the semiconductor [1]. If spin-polarized energy bands can be created, it opens the possibility of using magnetic fields to control spin and, consequently, the absorption of light or the transition of photoelectrons. This has potential applications in spintronic optoelectronic devices or photocatalysts.
Our work begins with ZnO nanowires, studying the effects of surface modification or doping with Co layers on their spin-polarized energy bands [2]. We apply this understanding to enhance the photocatalytic efficiency under magnetic fields. Similarly, we have demonstrated that doping manganese cations (Mn2+) into CsPbBr3 halide perovskite nanoplates can significantly boost photocatalytic CO2 reduction reaction efficiencies when an external magnetic field is applied, attributed to the creation of spin-polarized electrons after Mn doping [3].
Our results show that manipulating spin-polarized electrons in photocatalytic semiconductors is an effective strategy to enhance photocatalytic efficiencies. This approach has the potential to bring new opportunities in future optoelectronic, energy, and biomedical applications through the spin polarization engineering of semiconductor energy bands.
REFERENCE: [1] K. Ando, Science 312, 1883 (2006); [2] J. X. Lin, J. Thaomonpun, V. Thongpool, W. J. Chen, C. H. Huang, S. J. Sun, Z. Remeš, Y. T. Tseng, Y. F. Liao, H. S. Hsu, , ACS Appl. Mater. Interfaces, 13, 19, 23173 (2021); [3] C. C. Lin, T. R. Liu, S. R. Lin, K. M. Boopathi, C. H. Chiang, W. Y. Tzeng, W. H. Chang Chien, H. S. Hsu, C. W. Luo, H. Y. Tsai, H. A. Chen, P. C. Kuo, J. Shiue, J. W. Chiou, W. F. Pong, C. C. Chen, and C. W. Chen, J. Am. Chem. Soc. 144, 34, 15718-15726 (2022).

Single atom magnets offer the possibility of magnetic information storage in the most fundamental unit of matter. Rare-earth atom adsorption on suitable surfaces is a viable pathway for creating atomic scale magnetic memories. The strongly localized 4f electrons of RE show a very limited degree of covalency and preserve well-defined integer occupation with their electronic configuration controlled by the ligand environment. Recent XAS and XMCD experiments for Dy adatoms on MgO/Ag(001) thin films reveal strong dependence of the Dy adatom electronic and magnetic character on supporting MgO layer thickness [1]. We investigate the electronic structure and magnetism of individual Dy atom adsorbed on the MgO(001) substrate using the combination of DFT with the Hubbard-I approximation to the Anderson impurity model (DFT+U(HIA)) [2]. The divalent Dy[2+] adatom is found. Quantum tunneling leads to formation of the ground state with an in-plane orientation of the magnetic moment.
It explains experimentally observed absence of remanent magnetization, and the butterfly-type magnetic hysteresis loop in Dy adatom on the top of MgO(001) substrate [1].
The XAS and XMCD spectra are calculated in a good agreement with the experimental data.
Our studies can provide a viable route for further investigation and prediction of the rare-earth single atom magnets. We acknowledge partial support provided by the GACR grant No. 24-11992S, and EU-MSMT project TERAFIT - CZ.02.01.01/00/22_008/0004594.
REFERENCES: [1] F. Donati et al., Nano Lett. 21, 8266 (2021); [2] A. Shick, E. Belsch, A. Lichtenstein, Phys. Rev. B 108, L180408 (2023).

This study presents innovative approaches to fabricating and utilizing nanostructured boron-doped diamond (BDD) electrodes for electrochemical applications, particularly supercapacitors. Three distinct methods are explored: molten salt thermal etching (MSTE), Au mask-assisted reactive ion etching (RIE), and the RIE process combined with silicon micro-pyramids.
The MSTE technique, applied at moderate temperatures (450 °C) throughout the electrode bulk, fabricates nanoporous BDD electrodes with increased electrochemically active surface area, exhibiting up to 50-fold higher capacitance compared to pristine BDDE.
The Au mask-assisted RIE method produces vertically aligned nanorods, with diameters controlled by the initial thickness of the Au mask. These nanostructured BDD electrodes demonstrate improved electron transfer kinetics and 80% capacitance retention after 2000 cycles.
Finally, the combined RIE process with Si micro-pyramids yields hierarchically structured BDD electrodes comprising both nano- and micro-morphologies, further enhancing capacitance (53.7 mF/cm2) and 95.5% retention after 5000 cycles.
These fabrication approaches demonstrate the potential of nanostructured BDD electrodes in advancing miniaturized supercapacitors and other electrochemical applications, offering a combination of durability, high efficiency, and versatile performance across various potentials.

Lutetium aluminum garnet (LuAG) is the crystal well known for extraordinary useful for building highly efficient laser devices or ionizing radiation detectors. To design the most favorable physical properties, different dopants and synthesis methods are constantly developed, primarily focused on advantages of single-crystals. However, downscaling of the luminescent materials to nanosize also creates additional benefits of increased surface to volume ratio and thus, the efficiency of luminescence can be improved. Therefore, the aim of this work is to compare influence of Ce and Er doping on optical properties of LuAG nanogarnets. Synergy of methods like X-ray diffraction (XRD), Raman, photoluminescence (PL) and photothermal deflection spectroscopies (PDS) were applied to the newly synthesized LuAG:Ce(Er) nanopowders. In particular, the pure LuAG shows only negligible PL around 625 and 650 nm originating from accidental defects. The LuAG:Ce nanocrystals emits at 450 and 650 nm. The former wavelength corresponds to the cerium typical 5d-4f transition. LuAG:Er has 5 peaks in infrared PL spectrum around 1460, 1530, 1580, 1620 and 1660 nm which are commonly known Er3+ transitions between Stark levels. According to XRD, the materials are pure phase garnets.
ACKNOWLEDGEMENTS: The work was supported by Ministry of Education, Youth and Sports of Czech Republic (MEYS) Danube project 8X23025 and the program “Strategy AV 21” of the Czech Academy of Sciences, specifically work package VP 27 Sustainable Energy (Renewable energy resources and distributed energy systems). The financial support of the Leading Agency National Science Centre - Czech Science Foundation project No. 24-14580L is gratefully acknowledged.

GaN based structures from nanoscale to micron scale (quantum wires - nanorods -- micropillars) are widely used in many applications. Here we focus on detectors and scintillators with a view to water photocatalysis. Their preparation is based on epitaxial growth, mainly Molecular Beam Epitaxy and MetalOrganic Vapor Phase Epitaxy (MOVPE). Here we explain the advantages of MOVPE.
As the most prominent application, 1−3 μm high core-shell micropillars grown on a periodic mask were studied in the past decade for new-generation LEDs. Several groups reported that overgrowth of their pencil-shaped multiple InGaN/GaN quantum well (MQW) surfaces with p-doped GaN formed LEDs with several advantages over the planar design [1].
The aim of our future work is to develop a new type of scintillator structure based on GaN micropillars containing MQW heterostructures in core-shell geometry. This structure will take advantage of nonpolar orientation of QWs resulting in better overlap of electron hole wave function, increased efficiency of blue/UV luminescence and fast decay time. Published results of the time-resolved X-ray excited optical PL showing τ ≈ 0.14 ns [2].
The advantage of our suggested concept is also lower dislocation density in nanopillars and higher effective thickness. We suppose that the following technologies and structures will be developed:
• Growth of micropillars with minimal length of 3 μm.
• Growth of core-shell structure with InGaN/GaN MQW and luminescence in the blue or UV regions.
• The scintillator structure has expected PL decay time below 5 ns with sufficient RL efficiency in comparison to standard bulk or previously demonstrated MQW scintillators.
REFERENCES: [1] C. G. Bryce et al., Quantum Well Engineering in InGaN/GaN Core-Shell Nanorod Structures, J. Phys. D. Appl. Phys. 50, 42LT01 (2017)
[2]; J. Segura-Ruiz et al., Spatially and Time-Resolved Carrier Dynamics in Core-Shell InGaN/GaN Multiple-Quantum Wells on GaN Wire, Nano Lett. 21, 9494 (2021).

Due to their unique physicochemical properties, metal/metal oxide (Me/MeO) nanomaterials are gaining increasing attention in the scientific community. One possible and promising application field of such materials is their use as platforms for surface-enhanced Raman spectroscopy (SERS). In this case, the SERS activity is predominantly due to the plasmonic metals, while the presence of a metal-oxide may provide the possibility to clean once-used platforms by UV-induced photodegradation of analyte hence lowering the costs of SERS detection. Because of this, various methods to produce Me/MeO nanomaterials have been developed in the past decade. Among them, especially those based on different plasma-based techniques seem advantageous as they are compatible with the demand for a time- and cost-effective green way of producing materials. This study aims to explore and test the possibility of producing Au/Nb2O5 heterogeneous coatings by magnetron sputter deposition combined with a thermal treatment. As demonstrated, this approach makes it possible, under appropriate fabrication conditions, to achieve a high SERS activity with a detection limit of 10-7 M for methylene blue, and at the same time also UV-induced re-cyclability of formed Au/Nb2O5 coatings.
ACKNOWLEDGEMENTS: This work was supported by the grant GAČR 22-16667S from the Grant Agency of the Czech Republic.