Pokročilé nízkodimenzionální nanomateriály
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- ItemDual Interface Modification for Reduced Nonradiative Recombination in n-i-p Methylammonium-Free Perovskite Solar Cells(AMER CHEMICAL SOC, 2025-01-22) Rodriguez-Perez, Juan José; Esparza, Diego; Ans, Muhammad; Contreras-Solorio, David Armando; Diaz Perez, Teresa; Rodriguez Pereira, Jhonatan; Barea, Eva Maria; Zarazua, Isaac; Prochowicz, Daniel; Akin, Seckin; P Martinez-Pastor, Juan; Pascual, Jorge; Mora-Sero, Ivan; Turren-Cruz, Silver-HamillHigh defect concentrations at the interfaces are the basis of charge extraction losses and instability in perovskite solar cells. Surface engineering with organic cations is a common practice to solve this issue. However, the full implications of the counteranions of these cations for device functioning are often neglected. In this work, we used 4-fluorophenethylammonium cation with varying halide counteranions for the modification of both interfaces in methylammonium-free Pb-based n-i-p devices, observing significant differences among iodide, bromide, and chloride. The cation treatment of the buried and top interfaces resulted in improved surface quality of the perovskite films and largely improved carrier dynamics with reduced nonradiative recombination. Consequently, the optimal interface-modified methylammonium-free perovskite solar cells surpassed 20% efficiency and demonstrated remarkable operational stability. Our findings underscore the potential of comprehensive surface engineering strategies in advancing the perovskite film and device quality, thereby facilitating their broader and more successful applications.
- ItemEnhancing Stability of Microwave-Synthesized Cs2SnxTi1-xBr6 Perovskite by Cation Mixing(WILEY-V C H VERLAG GMBH, 2025-05-05) Reyes-Francis, Emmanuel; Julián-López, Beatriz; Echeverría-Arrondo, Carlos; Rodriguez Pereira, Jhonatan; Esparza, Diego; López-Luke, Tzarara; Espino-Valencia, Jaime; Prochowicz, Daniel; Mora-Sero, Ivan; Turren-Cruz, Silver-HamillThe double-perovskite material Cs2TiBr6 shows excellent photovoltaic potential, making it a promising alternative to lead-based materials. However, its high susceptibility to degradation in air has raised concerns about its practical application. This study introduces an interesting synthesis approach that significantly enhances the stability of Cs2TiBr6 powder. We implemented a gradual cation exchange process by substituting Ti4+ with Sn4+ in the efficient microwave-assisted synthesis method, developing a double perovskite Cs2SnxTi1-xBr6 type. A systematic study of increasing concentration of Sn4+ in Cs2TiBr6 perovskite has been performed to analyze the effect of Sn-doping degree on the chemical and thermal stability of the material and the optical features in both nitrogen and ambient atmospheres, significantly increasing the stability of the material in the air for over a week. Furthermore, introducing Sn4+ results in a more uniform polygonal crystal morphology of the powders and a slight band gap broadening. We show that microwave-assisted synthesis is highly efficient and cost-effective in producing more sustainable lead-free perovskite materials with enhanced stability and desirable electrical characteristics. This work suggests a promising method for synthesizing perovskite materials, opening new routes for scientific research and applications.
- ItemWireless electrochemical fabrication of tungsten oxide nanoporous layers in closed bipolar cells(ELSEVIER SCIENCE INC, 2025-07-01) Sepúlveda Sepúlveda, Lina Marcela; Baishya, Kaushik; Rodriguez Pereira, Jhonatan; Čičmancová, Veronika; Hromádko, Luděk; Macák, JanIn this work, the anodization of tungsten (W) foils using closed bipolar electrochemical cells is demonstrated for the first time. The anodization was done using three different electrolytes: (1) 1 M NH4NO3, 1 wt%. H2O in ethylene glycol (EG); (2) 1 M (NH4)2SO4, 75 mM NH4F in H2O; and (3) 170 mM NH4 1.5 wt%. H2O in EG. Different square-wave potentials and frequencies were applied during the anodization. Among the tested electrolytes, electrolyte 1 produced the most well-defined and homogeneous WO3 nanoporous (NP) layers. X-ray photoelectron spectroscopy confirmed the presence of multiple W oxidation states on the WO3 NP layers using electrolytes 1 and 2, with W6+ and W5+ being the dominant species. The results demonstrate well-defined WO3 NP layers with a high W6+ species concentration and less than 10 at.% W5+ is achieved using electrolyte 1. These findings provide valuable insights into the relationship between the electrolyte composition, W oxidation states, and the morphology of WO3 NP layers.
- ItemBiopolymeric fibers prepared by centrifugal spinning blended with ZnO nanoparticles for the treatment of Acne vulgaris(ELSEVIER, 2024-04-01) Říhová, Martina; Číhalová, Kristýna; Pouzar, Miloslav; Kuthanová, Michaela; Jelínek, Luděk; Hromádko, Luděk; Čičmancová, Veronika; Heger, Zbyněk; Macák, JanAcne vulgaris is a serious dermatological disease affecting a significant part of the population. Currently, available therapeutics are effective only at high concentrations, which has a negative environmental and economic impact. In particular, ZnO nanoparticles (NPs) have a great potential in various biomedical applications due to their specific properties and antibacterial/antiviral activity. In this study, biomedically approved ZnO NPs with distinct diameter were used as the active therapeutic modality to treat acne-causing pathogens. For the first time, we show the utilization of ZnO NPs that were evenly distributed within centrifugally spun fiber carriers. Upon application on the skin, ZnO NPs can sustainably release and have profound antibacterial activity at lower therapeutic concentrations. Fibers were made using innovative centrifugal spinning procedure from natural polymers - gum arabic and pullulan - that are known for their biocompatibility. Different amount of ZnO NPs (from 0.03 to 4.5 wt.% related to the dry mass) was added into the spinning polymer solution, either in a form of a dry powder or as a dispersion containing NPs and isopropyl myristate. The resulting fibers were subsequently characterized for morphology and presence of ZnO NPs by Scanning Electron Microscopy and Energy-Dispersive X-ray fluorescence spectrometry. The materials were thoroughly assessed for their antibacterial activity against Cutibacterium acnes and Staphylococcus epidermidis , which are major opportunistic pathogens causing acne. The combination of two types of nanomaterials, namely active nanoparticles and fiber carriers, proved to be very promising and bear a great potential for the treatment of these diseases.
- ItemLow-Temperature Atomic Layer Deposition Synthesis of Vanadium Sulfide (Ultra)Thin Films for Nanotubular Supercapacitors(WILEY, 2024-04-01) Zazpe Mendioroz, Raúl; Sepúlveda Sepúlveda, Lina Marcela; Rodriguez Pereira, Jhonatan; Hromádko, Luděk; Michalička, Jan; Kolíbalová, Eva; Kurka, Michal; Thalluri, Sitaramanjaneya Mouli; Sopha, Hanna Ingrid; Macák, JanHerein, the synthesis of vanadium sulfide (VxSy) by atomic layer deposition (ALD) based on the use of tetrakis(dimethylamino) vanadium (IV) and hydrogen sulfide is presented for the first time. The (ultra)thin films VxSy are synthesized in a wide range of temperatures (100-225 degrees C) and extensively characterized by different methods. The chemical composition of the VxSy (ultra)thin films reveals different vanadium oxidation states and sulfur-based species. Extensive X-ray photoelectron spectroscopy analysis studies the effect of different ALD parameters on the VxSy chemical composition. Encouraged by the rich chemistry properties of vanadium-based compounds and based on the variable valences of vanadium, the electrochemical properties of ALD VxSy (ultra)thin films as electrode material for supercapacitors are further explored. Thereby, nanotubular composites are fabricated by coating TiO2 nanotube layers (TNTs) with different numbers of VxSy ALD cycles at low temperature (100 degrees C). Long-term cycling tests reveal a gradual decline of electrochemical performance due to the progressive VxSy thin films dissolution under the experimental conditions. Nevertheless, VxSy-coated TNTs exhibit significantly superior capacitance properties as compared to the blank counterparts. The enhanced capacitance properties exhibited are derived from the presence of chemically stable and electrochemically active S-based species on the TNTs surface.