Ústav fyzikální a spotřební chemie


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Now showing 1 - 5 of 98
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    Novel highly stable conductive polymer composite PEDOT:DBSA for bioelectronic applications
    (Springer Nature, 2023-05-15) Tumová, Šárka; Malečková, Romana; Kubáč, Lubomír; Akrman, Jiří; Enev, Vojtěch; Kalina, Lukáš; Šafaříková, Eva; Pešková, Michaela; Víteček, Jan; Vala, Martin; Weiter, Martin
    In this work, a novel conductive polymer composite PEDOT:DBSA for bioelectronic applications was prepared and optimized. The novel PEDOT:DBSA composite possesses superior biocompatibility toward cell culture and electrical characteristics comparable to the widely used PEDOT:PSS. The cross-linking processes induced by the cross-linker GOPS, which was investigating in detail using Fourier transform Raman spectroscopy and XPS analysis, lead to the excellent long-term stability of PEDOT:DBSA thin films in aqueous solutions, even without treatment at high temperature. The electrical characteristics of PEDOT:DBSA thin films with respect to the level of cross-linking were studied in detail. The conductivity of thin films was significantly improved using sulfuric acid posttreatment. A model transistor devicebased on PEDOT:DBSA shows typical transistor behavior and suitable electrical properties comparable or superior to those of avaible conductive polymers in bioelectronics, such as PEDOT:PSS. Based on these properties, the newly developed material is well suitable for bioelectronic applications that require long-term contact with living organisms, such as wearable or implantable bioelectronics.
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    Density of bulk trap states of hybrid lead halide perovskite single crystals: temperature modulated space-charge-limited-currents
    (Springer Nature, 2019-03-04) Pospíšil, Jan; Zmeškal, Oldřich; Nešpůrek, Stanislav; Krajčovič, Jozef; Weiter, Martin; Kovalenko, Alexander
    Temperature-modulated space-charge-limited-current spectroscopy (TMSCLC) is applied to quantitatively evaluate the density of trap states in the band-gap with high energy resolution of semiconducting hybrid lead halide perovskite single crystals. Interestingly multicomponent deep trap states were observed in the pure perovskite crystals, which assumingly caused by the formation of nanodomains due to the presence of the mobile species in the perovskites.
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    Direct measurement of oxygen reduction reactions at neurostimulation electrodes
    (IOP Publishing Ltd, 2022-06-01) Ehlich, Jiří; Migliaccio, Ludovico; Sahalianov, Ihor; Nikić, Marta; Brodský, Jan; Gablech, Imrich; Vu, Xuan Thang; Ingebrandt, Sven; Glowacki, Eric Daniel
    Objective. Electric stimulation delivered by implantable electrodes is a key component of neural engineering. While factors affecting long-term stability, safety, and biocompatibility are a topic of continuous investigation, a widely-accepted principle is that charge injection should be reversible, with no net electrochemical products forming. We want to evaluate oxygen reduction reactions (ORR) occurring at different electrode materials when using established materials and stimulation protocols. Approach. As stimulation electrodes, we have tested platinum, gold, tungsten, nichrome, iridium oxide, titanium, titanium nitride, and poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate). We use cyclic voltammetry and voltage-step amperometry in oxygenated versus inert conditions to establish at which potentials ORR occurs, and the magnitudes of diffusion-limited ORR currents. We also benchmark the areal capacitance of each electrode material. We use amperometric probes (Clark-type electrodes) to quantify the O-2 and H2O2 concentrations in the vicinity of the electrode surface. O-2 and H2O2 concentrations are measured while applying DC current, or various biphasic charge-balanced pulses of amplitude in the range 10-30 mu C cm(-2)/phase. To corroborate experimental measurements, we employ finite element modelling to recreate 3D gradients of O-2 and H2O2. Main results. All electrode materials support ORR and can create hypoxic conditions near the electrode surface. We find that electrode materials differ significantly in their onset potentials for ORR, and in the extent to which they produce H2O2 as a by-product. A key result is that typical charge-balanced biphasic pulse protocols do lead to irreversible ORR. Some electrodes induce severely hypoxic conditions, others additionally produce an accumulation of hydrogen peroxide into the mM range. Significance. Our findings highlight faradaic ORR as a critical consideration for neural interface devices and show that the established biphasic/charge-balanced approach does not prevent irreversible changes in O-2 concentrations. Hypoxia and H2O2 can result in different (electro)physiological consequences.
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    Impact of various oxidation processes used for removal of sulfamethoxazole on the quality of treated wastewater
    (KeAi Communications Co., Ltd., 2023-04-17) Tulková, Tereza; Fučík, Jan; Kozáková, Zdenka; Procházková, Petra; Krčma, František; Zlámalová Gargošová, Helena; Mravcová, Ludmila; Sovová, Kateřina
    The objective of this research is to describe the impact of different advanced oxidation processes used for the removal of sulfamethoxazole on wastewater quality. Ozone, UV, a combination of ozone and UV, and plasma discharge were employed. Concentrations of sulfamethoxazole were analysed by LC-MS/MS. Chemical and microbiological analyses and ecotoxicological tests were conducted to investigate the quality of treated wastewater. The results of this study show that the most effective technique for the removal of sulfamethoxazole is O3, followed by plasma discharge, O3 + UV and, finally, UV. A significant effect of tested advanced oxidation processes on the chemical composition of wastewater was not observed; however, the number of microorganisms was reduced. In the case of ecotoxicological tests with Lemna minor and crustacean Daphnia magna, a significant negative effect was only observed when plasma was applied.
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    Physico-Chemical Properties of Lithium Silicates Related to Their Utilization for Concrete Densifiers
    (MDPI, 2023-03-08) Kalina, Lukáš; Bílek, Vlastimil; Sedlačík, Martin; Cába, Vladislav; Smilek, Jiří; Švec, Jiří; Bartoníčková, Eva; Rovnaník, Pavel; Fládr, Josef
    Protection of concrete against aggressive influences from the surrounding environment becomes an important step to increase its durability. Today, alkali silicate solutions are advantageously used as pore-blocking treatments that increase the hardness and impermeability of the concrete’s surface layer. Among these chemical substances, known as concrete densifiers, lithium silicate solutions are growing in popularity. In the present study, the chemical composition of the lithium silicate densifiers is put into context with the properties of the newly created insoluble inorganic gel responsible for the micro-filling effect. Fourier-transform infrared spectroscopy was used as a key method to describe the structure of the formed gel. In this context, the gelation process was studied through the evolution of viscoelastic properties over time using oscillatory measurements. It was found that the gelation process is fundamentally controlled by the molar ratio of SiO2 and Li2O in the densifier. The low SiO2 to Li2O ratio promotes the gelling process, resulting in a rapidly formed gel structure that affects macro characteristics, such as water permeability, directly related to the durability of treated concretes.