In this study, the potential to modify the phase structure and morphology of manganese dioxide synthesized via the hydrothermal route was explored. A series of samples were prepared at different synthesis temperatures (100, 120, 140, and 160 °C) using KMnO4 and MnSO4·H2O as precursors. The phase composition and morphology of the materials were analyzed using various physicochemical methods. The results showed that, at the lowest synthesis temperature (100 °C), an intercalation compound with composition K1.39Mn3O6 and a very small amount of α-MnO2 was formed. At higher temperatures (120–160 °C), the amount of α-MnO2 increased, indicating the formation of two clearly distinguished crystal structures. The sample obtained at 160 °C exhibited the highest specific surface area (approximately 157 m2/g). These two-phase (α-MnO2/K1.39Mn3O6) materials, synthesized at the lowest and highest temperatures, respectively, and containing an appropriate amount of carbon xerogel, were tested as active mass for positive electrodes in a solid-state supercapacitor, using a Na+-form Aquivion® membrane as the polymer electrolyte. The electrochemical evaluation showed that the composite with the higher specific surface area, containing 75% manganese dioxide, demonstrated improved characteristics, including 96% capacitance retention after 5000 charge/discharge cycles and high energy efficiency (approximately 99%). These properties highlight its potential for application in solid-state supercapacitors.

The influence of organic-inorganic ureasil-based polymers containing sulfur on the bioanalytical properties of electrochemical biosensors was studied. The ureasil-As2S3 (0.1 g of As2S3) and ureasil-chalcogenide (0.066 and 0.198 g of S) composites were selected for research. Network properties (free volume) of the samples are rather similar as revealed by positron annihilation lifetime spectroscopy (PALS) measurements. At the same time, the effect of sulfur on the operational parameters of laccase biosensors was observed. In particular, the obtained results showed the differences in the sample responses in chronoamperometric measurements which most probably do not originate from differences in the structure of the samples at the nanoscale level. The results of this work support the earlier proposed topological and chemical mechanisms for effective enzyme immobilization using holding polymer matrixes.

The current research aims to present the structural characterization of Gd-doped ceria powders and ceramics, investigating the structural evolution resulting from cerium substitution with Gd across the entire composition range from 0 to 100 mol.% Gd2O3. Ce1-xGdxO2-x/2 powders with varying Gd contents (0 ≤ x ≤ 1) were synthesized using the ionic gelation method followed by thermal annealing. The resulting powders were subjected to high-temperature treatment to obtain ceramics. Characterization methods included X-ray diffraction (XRD) to identify phase composition and confirm the formation of Ce1-xGdxO2-x/2 solid solutions, infrared spectroscopy (IR) and scanning electron microscopy (SEM) for structural and morphological studies, and X-ray photoelectron spectroscopy (XPS) to evaluate the electronic structure. Comparative analysis of Gd-doped calcined powders and sintered pellets revealed the impact of thermal treatment on the structural features of the resulting solid solutions, elucidating the influence of gadolinium substitution. The novelty of this research lies in demonstrating the successful preparation of Ce1-xGdxO2-x/2solid solutions via an alginate-mediated ion-exchange process and providing a detailed structural investigation over the entire range of dopant concentrations. This assessment highlights the feasibility for further research of these materials as suitable candidates for intermediate-temperature solid oxide fuel cells (IT-SOFCs) or catalyst applications. Doi: 10.28991/ESJ-2024-08-05-01 Full Text: PDF

We focus our attention on the influence of hydrophobic silver nanoparticles (Ag NPs) on the 1-Stearoyl-2-oleoylsn-glycero-3-phosphocholine (SOPC) model system. Results obtained by differential scanning calorimetry (DSC) and infrared (IR) spectroscopy were compared to their counterpart for lipid systems with incorporated hydrophobic gold nanoparticles (AuNPs) and pure SOPC lipid in a water environment. The results show a strong effect of hindering the gel-to-liquid crystalline phase transition for both types of noble metal hydrophobic NPs. The effect of the phase transitions shift to the lower temperatures is more pronounced for the silver particles for the concentrations studied. According to the IR spectral analyses, no negative effect is observed of the NPs on the lipid hydration for the concentration studied, and the plasmon effect of the Ag NPs appears to be more pronounced.

Novel proton conducting materials with composition 85SiO2–9P2O5–6TiO2, modified by addition of liquid xH3PO4 in different amounts xH3PO4 = 0; 17; 35; 52 mmol, were synthesized via sol–gel route. XRD patterns show amorphous nature for “pure” (xH3PO4 = 0 mmol) sample and crystalline for all H3PO4-doped samples. FTIR and SEM analysis revealed that this modification led to appreciable structural changes on molecular level and morphology, which, heavily impacts the water intake ability, impedance behavior as well as the dielectric parameters. The detailed impedance examination showed distinct response of changing parameters such as relative humidity and temperature, while the dielectric parameters derived from the impedance spectra, provide in-depth understanding of proton conduction dynamic. Based on these observations different models were proposed gathering proton transfer in humid and dry atmospheres. The enhanced proton conduction is a basic requirement for successful usage of the material for hydrogen gas detection.

Novel proton conducting materials with composition 85SiO(2)-9P(2)O(5)-6TiO(2), modified by addition of liquid xH(3)PO(4) in different amounts X-H3PO4 = 0; 17; 35; 52 mmol, were synthesized via sol-gel route. XRD patterns show amorphous nature for "pure" (X-H3PO4 = 0 mmol) sample and crystalline for all H3PO4-doped samples. FTIR and SEM analysis revealed that this modification led to appreciable structural changes on molecular level and morphology, which, heavily impacts the water intake ability, impedance behavior as well as the dielectric parameters. The detailed impedance examination showed distinct response of changing parameters such as relative humidity and temperature, while the dielectric parameters derived from the impedance spectra, provide in-depth understanding of proton conduction dynamic. Based on these observations different models were proposed gathering proton transfer in humid and dry atmospheres. The enhanced proton conduction is a basic requirement for successful usage of the material for hydrogen gas detection. (C) 2020 The Authors. Published by Elsevier B.V.

In this study two hybrid organic-inorganic ureasilicate monomers with different length of polymer segments were chosen for preparation of sol-gel material that includes two moieties blended on the molecular scale. The first monomer was obtained by crosslinking a double terminated polyoxyalkyleneamine with an isocyanate modified silicone ethoxide and the second one - by crosslinking between the isocyanate modified silicone ethoxide with an amino modified silicone ethoxide. Sol-gel route was applied for transformation of the liquid monomer blends in transparent materials with varying degree of rigidity. The prepared samples were characterized by small-angle X-ray scattering, Fourier-transform infrared spectroscopy, positron annihilation lifetime spectroscopy, and swelling experiments. The results demonstrate that the structure of the obtained materials could be tuned by a simple variation of molar fraction ratio between these two monomers. This makes it possible to obtain nanostructured materials with predictable properties.

Recent results obtained by studies on the network properties using positron annihilation lifetime spectroscopy and swelling measurements in the ureasil-based and photocross-linked polymer matrices are compared. Common features observed are the larger difference (alpha(F2) - alpha(F1)) of the coefficients for the thermal expansion of free-volume holes alpha(F1), alpha(F2) below and above T-g, respectively, in the polymer matrices, the highest sensitivity of the amperometric enzyme biosensors constructed based on the polymer matrices. It is suggested that the correlation found may be more general. It seems, therefore, that controlling the network properties of polymer matrices suitable for construction of amperometric enzyme biosensors by examining (alpha(F2) alpha(F1)) magnitude in temperature dependent positron annihilation lifetime spectroscopy experiment may be used for improvement of operational parameters of such sensors.

Flexible optically clear ureasil monoliths were synthesized by hydrolysis and condensation of two hybrid organic-inorganic ureasilicate monomers (precursors) with different lengths of the polymer segments. The monomer with a longer polymer chain length was obtained by reaction of 1 mol of silicon modified alkoxyde (ICPTES) and 2 mol of double terminated polyetheramine (Jeffamine), and that with a shorter length by reaction of 1 mol of ICPTES and 1 mol of 3-aminopropyl triethoxysilane (APTES), which provides stoichiometric ratio between the initial ingredients. The obtained materials were characterized by optical UV-VIS spectroscopy and depth-sensing indentation method (DSI). The influence of the molar ratio between the ureasilicate monomers on the optical and mechanical properties of the samples was investigated.

Application of positron annihilation spectroscopy using a variable-energy slow positron beam (VESPB) as a key experimental tool to understand ion-induced processes and defect structures in a number of polymer composite materials important for a practical use is demonstrated. The results concerning 40 keV B+ implanted polymethylmethacrylate (B:PMMA) and 30 keV Ag+ implanted PMMA (Ag:PMMA), and organic-inorganic ureasil composite (Ag:ureasil) are discussed. Utilized VESPB techniques allow to confirm carbonization of ion-irradiated B:PMMA, formation of carbon-shell Ag-core nanoparticles in Ag:PMMA and evolution in size of Ag nanoparticles in Ag:ureasil, which was revealed by means of UV-Vis absorption and Raman spectroscopy measurements.Application of positron annihilation spectroscopy using a variable-energy slow positron beam (VESPB) as a key experimental tool to understand ion-induced processes and defect structures in a number of polymer composite materials important for a practical use is demonstrated. The results concerning 40 keV B+ implanted polymethylmethacrylate (B:PMMA) and 30 keV Ag+ implanted PMMA (Ag:PMMA), and organic-inorganic ureasil composite (Ag:ureasil) are discussed. Utilized VESPB techniques allow to confirm carbonization of ion-irradiated B:PMMA, formation of carbon-shell Ag-core nanoparticles in Ag:PMMA and evolution in size of Ag nanoparticles in Ag:ureasil, which was revealed by means of UV-Vis absorption and Raman spectroscopy measurements.

Synthesis of gold nanoparticles (Au-NPs) was performed using method of an inorganic chemical reduction. The synthesized Au-NPs showed an intensive surface plasmon resonance band at 525 nm that is typical for corresponding Au-NPs reported in literature. The structural and morphology characterizations of the obtained Au-NPs were carried out using SEM, AFM, TEM, and X-ray spectral analysis. The possibility of usage of Au-NPs as a carrier for covalent immobilization of commercial laccase and the combination of the obtained bio-Au-NPs with ureasil polymers as host matrixes for formation of bio-nanocomposite films was studied. The prospect of using the obtained bio-nanocomposite films in biosensor technologies in order to improve the bioanalytical characteristics of sensory elements has been proved.

NiCo2O4-spinel has been prepared by three different techniques: The Pechini method, a hydrothermal method and a precipitation reaction. The obtained samples have been examined by X-ray diffraction (XRD), differential thermal analysis (DTA) and scanning electron microscopy (SEM). The results reveal that materials prepared by the Pechini method possess two phases (Co3O4 and NiO), those obtained by the hydrothermal method have phases of NixCo3-xO4. Single-phase NiCo2O4 material is obtained only by the precipitation reaction. The obtained NiCo2O4 material is nanosized, exhibiting thermal stability up to 700 °C, where thermal decomposition of NiCo2O4 to Co3O4 and NiO takes place. In the region of thermal stability, a linear thermal expansion of the elementary cell has been observed.

Polymer nanocomposites formed by low-energy ion implantation were studied by means of positron annihilation spectroscopy with a variable-energy positron beam or slow positron beam spectroscopy. Silver ion implantation into polymethylmethacrylate (Ag:PMMA) and hybrid organic-inorganic ureasil (Ag:ureasil) was performed at different ion fluences with a constant energy of 30 keV and a current density of 1 μA/cm2 in order to prepare Ag nanoparticles in the near-surface region of polymer matrix. Contribution of Doppler broadening slow positron beam spectroscopy technique for understanding Ag nanoparticles formation in Ag:PMMA and Ag:ureasil nanocomposite films is demonstrated.

Transparent organic-inorganic ureasilicate materials (ureasils) were synthesized by hydrolysis and co-condensation of two organic – inorganic precursors, obtained by reactions between 3-isocyanatepropyltriethoxysilane (ICPTES) and double terminated polyetheramine (Jeffamine), and between ICPTES and 3-aminopropyl triethoxysilane (APTES), respectively. The prepared samples were characterized by optical UV – VIS spectroscopy, small-angle X-ray scattering (SAXS), FTIR spectroscopy and the depth sensing indentation method (DSI). It is shown that the molar ratio between the initial components influences on the mechanical and optical properties of the materials in the investigated range.

Ureasil and ureasil-chalcogenide glass composites of different history (fresh and aged during 1 year) were used for the immobilization of laccase and the construction of amperometric biosensors. A correlation between the microscopical free-volume of the polymer matrices as revealed by low-temperature positron annihilation lifetime spectroscopy and biosensor characteristics of the laccase-containing ureasil based biosensors is established. The observed findings could be applied for improvement of the operational parameters of the constructed biosensors, which may have potential for monitoring the level of pollution of wastewater.

The swelling behavior of pure ureasil and ureasil-chalcogenide glass composites of different history (fresh, aged and thermally heated) was examined using ethyl alcohol. Swelling experiments showed the structure of the network of samples aged for 1 year after preparation has a lower swelling ability compared with pure ureasil as well with the composite, but the effect is more expressed for the pure polymer. In the cases of a thermally heated pure ureasil sample and a more than 5 years after preparation aged sample of the composite, the structure network has practically the same swelling ability as the fresh pure ureasil and the composite samples. It is suggested that one of the factors influencing the swelling is the change of the basic ureasil network due to aging and/or thermal heating.

Network properties of ureasil-based polymer matrixes suitable for construction of amperometric biosensors were probed by positron annihilation lifetime spectroscopy and swelling experiments. Temperature dependences of the ortho-positronium (o-Ps) lifetimes and their relative intensities were measured in a temperature range of 15-350 K. Glass transition temperatures and expansion coefficients of microscopical free-volume for the investigated polymers were determined. Differences in network behavior for the aged samples and the effect of chalcogenide (As2S3) particles on the free volume of ureasil network were observed. Swelling experiments using ethyl alcohol showed that the structure of the aged sample network had less swelling ability for the pure ureasil as well as composite. This suggests that the one of factors influencing swelling is the change of the basic ureasil network due to ageing. It is supposed that the network properties obtained by positron annihilation lifetime spectroscopy and swelling experiments could be very helpful to understand better the bio-functionality of the constructed biosensor based on the ureasil-chalcogenide glass composite.

ABSTRACT Innovative amperometric biosensors for monitoring the level of wastewater pollution have been constructed on the surface of the gold planar electrodes C220AT “DropSens” by using the organic–inorganic ureasil‐based composites as host matrixes and immobilized commercial laccase from Trametes versicolor . It was found that the biosensor based on the ureasil–chalcogenide glass composite is characterized by a very high sensitivity (67,540 А M −1 m −2 ) that is 38.3 times higher than for pure ureasil (the sensitivity of the bioelectrode was calculated as 1762 А M −1 m −2 ). On the other hand, application of the ureasil–chalcogenide glass composite with incorporated silver nanoparticles (NPs) synthesized by high‐dose (1.0 × 10 17 Ag + /cm 2 ) 30 keV Ag + ion implantation results in decreasing the biosensor sensitivity up to 2390 times (the sensitivity of the bioelectrode was 28.3 А M −1 m −2 ). The role of additives (chalcogenide glass and silver NPs) in the ureasil matrix on the biofunctionality of the biosensors produced is considered. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45278.

The purpose of this study is to determine the possibility of biofilm formation from different bacterial strains on the UREASIL surface as compared with the formation of biofilms on glass surface. Seven gram-positve and eight gram-negative bacterial strains were used in this study. The feasibility of microbial biofilm formation on the surface of the new material UREASIL and on the surface of glass (control samples) was detected by three methods: determination of the number of alive bacterial cells in the biofilms; determination of the protein content in the biofilms by a modified Lowry method; confocal laser scanning microscopy for detection/visualization of the biofilms. The structure of UREASIL was more unfavorable for adhesion: and breeding than that of the glass, but problematic species with strong production of capsule substance or slime, such as Klebsiella pneumonie and Pseudomonas aeruginosa formed thick biofilms after 48 h cultivation on UREASIL, which were detected by three methods: confocal fluorescence microscopy, modified Lowry method and counting the number of surviving bacteria that colonized the surface of the glass and the UREASIL.

This paper presents the results from a comparative study between two types of valve-regulated lead-acid battery cells, with uncoated and polymer composite coated absorptive glass mat (AGM) separators. The volt-ampere characteristics of the studied cells, recorded at different ambient temperatures, show that the cells with polymer coated separators have significantly lower overcharge (recombinant) current than the cells with conventional untreated AGM separator. During overcharge, the higher recombinant current in the cells with plain separator leads to higher cell temperature than that of the cells with polymer coated AGM separator.The possibility to avoid thermal runaway (TR) is also illustrated during polarization of the cells at 2.65 V. After 320 h, a conventional cell has C/4 current (trend to TR), while the cells with composite coating sustain low (C/26) constant current for long period of time (at least 650 h). The cycle life test indicates stable operation of the cells with coated separator, while the conventional cell reaches high recombinant current and thus, it is susceptible to thermal runaway phenomena. (C) 2015 Elsevier B.V. All rights reserved.