Univerzitní institut

Simultaneous Cross-Linking and Nanoparticle Anchoring by Dialdehyde Cellulose in Injectable Composite Chitosan/Polypyrrole Hydrogels

Thu, 01 Jan 2026 00:00:00 GMT

Simultaneous Cross-Linking and Nanoparticle Anchoring by Dialdehyde Cellulose in Injectable Composite Chitosan/Polypyrrole Hydrogels Muchová, Monika; Münster, Lukáš; Kolařík, Roman; Víchová, Zdenka; Vašíček, Ondřej; Humpolíček, Petr; Vícha, Jan The injectable composite hydrogel with covalently bound polypyrrole (PPy) has been prepared using dialdehyde cellulose (DAC) as a bifunctional cross-linker, forming dynamic imine bonds with water-soluble half acetylated chitosan (SCN) and simultaneously tethering the PPy nanoparticles by aldol condensation. The novelty lies in translating this dual chemistry into an injectable, self-healing hydrogel system, for the first time fully utilizing dynamic Schiff base cross-linking in combination with covalent PPy anchoring. PPy is also involved both in hydrogel cross-linking, altering its rheological behavior, but also providing antioxidative and anti-inflammatory effects. The resulting hydrogels exhibited shear-thinning behavior, rapid self-healing, and storage moduli ranging from 25 to 47 Pa, allowing for injection through 21 G needles. All formulations were noncytotoxic toward NIH/3T3 fibroblasts and RAW 264.7 macrophages. In scratch assays, SCN_DAC_20_PPy significantly accelerated wound closure, with the residual wound area to 39 +/- 2% after 10 h versus 83 +/- 7% for controls and 65 +/- 3% for the corresponding PPy-free hydrogel. In LPS-stimulated macrophages, all hydrogels decreased nitric oxide production, and PPy-containing hydrogels additionally reduced IL-6 secretion. The SCN/DAC/PPy injectable hydrogels thus exhibit cytocompatibility, self-healing properties, and anti-inflammatory activity, representing a promising platform for the future development of advanced wound dressings.

Ni- and Zn-Doping Effects on Cu/SiO2 Catalysts in Nonoxidative Ethanol Dehydrogenation

Thu, 01 Jan 2026 00:00:00 GMT

Ni- and Zn-Doping Effects on Cu/SiO2 Catalysts in Nonoxidative Ethanol Dehydrogenation Pokorný, Tomáš; Macháč, Petr; Moravec, Zdeněk; Šimoníková, Lucie; Leonová, Lucie; Hlavenková, Zuzana; Škoda, David; Pacultová, Kateřina; Karásková, Kateřina; Stýskalík, Aleš Nonoxidative ethanol dehydrogenation opens a pathway for the sustainable production of acetaldehyde and butadiene. One crucial aspect of producing butadiene by the Lebedev process is the high-temperature stability of ethanol to acetaldehyde conversion. However, copper-based catalysts, despite exhibiting high activity and selectivity, suffer from sintering and coking and need to be improved for successful industrial applications. Herein, we show Cu-based (similar to 2.5 wt %) catalysts doped with Ni and Zn (0.028-0.36 wt %) to improve the catalytic performance of nanoparticles. The catalysts were prepared by hydrolytic sol-gel and dry impregnation methods. STEM analysis determined the nanoparticle sizes in the 1.9-2.8 nm range. Ni-doped catalysts outperformed the parent Cu catalysts in ethanol dehydrogenation activity at lower temperatures (185-220 degrees C) but suffered from faster deactivation. The Zn-doped catalysts exhibited improved high-temperature stability. For these materials, acetaldehyde selectivity fluctuated around similar to 90% and acetaldehyde productivity reached 3.63 g g-1 h-1 at 290 degrees C and a WHSV of 4.73 h-1. The improved stability of the Zn-doped samples was correlated with lower coke formation (XPS, TG analysis, and Raman spectroscopy).

Surface functionalization of medical-grade polyvinyl chloride treated with ammonia plasma

Thu, 01 Jan 2026 00:00:00 GMT

Surface functionalization of medical-grade polyvinyl chloride treated with ammonia plasma Zaplotnik, Rok; Recek, Nina; Primc, Gregor; Gyergyek, Andrej; Lehocký, Marián; Mozetič, Miran; Vesel, Alenka Polyvinyl chloride (PVC) is often the material of choice for the synthesis of various components used in medical practice, particularly catheters. As-synthesized components may not exhibit appropriate biocompatibility, so the surface should be modified or coated. Amine groups were grafted onto the PVC surface by brief exposure to ammonia plasma generated by a low-pressure inductively coupled radiofrequency discharge in E mode (30 Pa, 25 W). The treatment time ranged from 0.5 to 300 s. The measured density of charged particles was approximately 2 ± 1 × 1015 m−3 and the flux of NH and NH2 radicals was approximately 3 × 1023 m−2s−1. X-ray photoelectron spectroscopy (XPS) was used to study the evolution of nitrogen-containing functional groups versus the treatment time. The chlorine concentration was not affected much, but the nitrogen concentration in the surface film increased logarithmically with increasing treatment time. The N concentration was approximately 2 at.% after 0.5 s of treatment and reached approximately 9 at.% after 300 s. Some PVC samples were also pretreated with hydrogen plasma. The pretreatment was beneficial for rapid functionalization, as the N concentration reached 6 at.% after 0.5 s of plasma treatment, but the concentration after prolonged treatment was the same as that for a single-step ammonia plasma treatment. High-resolution XPS Cl2p spectra revealed significant modification of the chlorine binding, especially after pretreatment with hydrogen plasma. A possible explanation for this modification is the formation of Cl− binding states, resulting from bond scission by the absorption of VUV radiation in the PVC surface film.

Cement nanocomposite with CoFe2O4 nanoparticles and graphite flakes for microwave absorption in X-band frequency

Thu, 01 Jan 2026 00:00:00 GMT

Cement nanocomposite with CoFe2O4 nanoparticles and graphite flakes for microwave absorption in X-band frequency Mariappan, Vanamoorthy; Křivánková, Eliška; Masař, Milan; Jurča, Marek; Machovský, Michal; Kalina, Lukáš; Vilčáková, Jarmila; Kuřitka, Ivo; Boháč, Martin; Yadav, Raghvendra Singh This study reports the microwave absorption in cementitious composites through the incorporation of graphite flakes (GF) and ultrasonically synthesized spherical cobalt ferrite (CoFe2O4) nanoparticles (CF). Composites with 2.5 wt% GF and 7.5 wt% CF were prepared and characterized for their structural, magnetic, mechanical, and electromagnetic properties. The phase purity of CF nanoparticles and the presence of fillers in the cement matrix were confirmed by X-ray diffraction (XRD). The morphology, distribution, and interfacial interactions between the fillers and the cement matrix were examined using field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). Magnetic hysteresis loops revealed a saturation magnetization of 5.8 emu/g for the cement nanocomposite, confirming the retention of some magnetic behaviour of CF in cement matrix. The results demonstrated excellent microwave absorption performance in X-band range, with a minimum reflection loss (RLmin) of −41.9 dB at 10.59 GHz and an effective absorption bandwidth (EAB) of 2.4 GHz (below −10 dB) at a thickness of only 2 mm, corresponding to microwave absorption efficiency of 99.994%. The obtained microwave absorption performance is attributed to the synergistic effects of permittivity and permeability, favourable impedance matching, and high attenuation constant due to the combined dielectric loss from GF and magnetic loss from CF. Despite a slight reduction in mechanical strength compared to the reference, the composite meets standard structural requirements. This work highlights the potential of using conductive and magnetic nanofillers to develop high-performance cementitious composites for X-band microwave absorption applications. © 2026 The Authors