Influence of crystal structure and composition on optical and electronic properties of pyridinium-based bismuth iodide complexes.

This study investigates the impacts of structure and composition on the optical and electronic properties of a series of pyridinium-based bismuth iodide complexes. Organic substrates with various functional groups, such as 4-aminopyridine (4-Ampy), 4-methylpyridine (4-Mepy), 4-dimethylaminopyridine (4-Dmapy), and 4-pyridinecarbonitrile (4-CNpy) with different electron-donating and electron-withdrawing groups at the para position of the pyridine ring were employed. Crystallographic analysis reveals various bismuth iodide structures, including 1D chains and discrete 0D motifs. The optical band gap of these materials, identified via diffuse reflectance spectroscopy (DRS) and verified with density functional theory (DFT) calculations, is influenced by the crystal packing and stabilising interactions. Through a comprehensive analysis, including Hirshfeld surface (HS) and void assessment, the study underscores the influence of noncovalent intermolecular interactions on crystal packing. Spectroscopic evaluations provide insights into electronic interactions, elucidating the role of electron donor and acceptor substituents within the lattice. Thermogravimetric differential thermal analysis (TG-DTA) indicates structural stability up to 250 °C. Linear sweep voltammetry (LSV) reveals significant conductivity in the range of 10-20 mS per pixel at 298.15 K. X-ray absorption spectroscopy (XAS) at the Bi L3 edge indicates a similar oxidation state and electronic environment across all samples, underscoring the role of bismuth centres surrounded by iodides.

The Memristive Properties and Spike Timing-Dependent Plasticity in Electrodeposited Copper Tungstates and Molybdates.

Memristors possess non-volatile memory, adjusting their electrical resistance to the current that flows through them and allowing switching between high and low conducting states. This technology could find applications in fields such as IT, consumer electronics, computing, sensors, and medicine. In this paper, we report successful electrodeposition of thin-film materials consisting of copper tungstate and copper molybdate (CuWO4 and Cu3Mo2O9), which showed notable memristive properties. Material characterisation was performed with techniques such as XRD, XPS, and SEM. The electrodeposited materials exhibited the ability to switch between low and high resistive states during varied cyclic scans and short-term impulses. The retention time of these switched states was also explored. Using these materials, the effects seen in biological systems, specifically spike timing-dependent plasticity, were simulated, being based on analogue operation of the memristors to achieve multiple conductivity states. Bio-inspired simulations performed directly on the material could possibly offer energy and time savings for classical computations. Memristors could be crucial for the advancement of high-efficiency, low-energy neuromorphic electronic devices and technologies in the future.

In vitro cytocompatibility and antibacterial studies on biodegradable Zn alloys supplemented by a critical assessment of direct contact cytotoxicity assay.

In vitro cytotoxicity assessment is indispensable in developing new biodegradable implant materials. Zn, which demonstrates an ideal corrosion rate between Mg- and Fe-based alloys, has been reported to have excellent in vivo biocompatibility. Therefore, modifications aimed at improving Zn's mechanical properties should not degrade its biological response. As sufficient strength, ductility and corrosion behavior required of load-bearing implants has been obtained in plastically deformed Zn-3Ag-0.5Mg, the effect of simultaneous Ag and Mg additions on in vitro cytocompatibility and antibacterial properties was studied, in relation to Zn and Zn-3Ag. Direct cell culture on samples and indirect extract-based tests showed almost no significant differences between the tested Zn-based materials. The diluted extracts of Zn, Zn-3Ag, and Zn-3Ag-0.5Mg showed no cytotoxicity toward MG-63 cells at a concentration of ≤12.5%. The cytotoxic effect was observed only at high Zn2+ ion concentrations and when in direct contact with metallic samples. The highest LD50 (lethal dose killing 50% of cells) of 13.4 mg/L of Zn2+ ions were determined for the Zn-3Ag-0.5Mg. Similar antibacterial activity against Escherichia coli and Staphylococcus aureus was observed for Zn and Zn alloys, so the effect is attributed mainly to the released Zn2+ ions exhibiting bactericidal properties. Most importantly, our experiments indicated the limitations of water-soluble tetrazolium salt-based cytotoxicity assays for direct tests on Zn-based materials. The discrepancies between the WST-8 assay and SEM observations are attributed to the interference of Zn2+ ions with tetrazolium salt, therefore favoring its transformation into formazan, giving false cell viability quantitative results.

The Utilisation of Solid Fuels Derived from Waste Pistachio Shells in Direct Carbon Solid Oxide Fuel Cells.

The comprehensive results regarding the physicochemical properties of carbonaceous materials that are obtained from pistachio shells support their usage as solid fuels to supply direct carbon solid oxide fuel cells (DC-SOFCs). The influence of preparation conditions on variations in the chemical composition, morphology of the biochar powders, and degree of graphitization of carbonaceous materials were investigated. Based on structural investigations (X-ray diffraction analysis and Raman spectroscopy), it was observed that disordered carbon particles developed during the application of thermal treatments. The use of X-ray fluorescence enabled a comparative analysis of the chemical composition of the inorganic matter in biocarbon-based samples. Additionally, the gasification of carbonaceous-based samples vs. time at a temperature of 850 °C was investigated in a H2O or CO2 gas atmosphere. The analysis demonstrated the conversion rate of biochar obtained from pistachio shells to H2, CH4 and CO during steam gasification. The electrochemical investigations of the DC-SOFCs that were supplied with biochars obtained from pistachio shells were characterized by satisfactory values for the current and power densities at a temperature range of 700-850 °C. However, a higher power output of the DC-SOFCs was observed when CO2 was introduced to the anode chamber. Therefore, the impact of the Boudouard reaction on the performance of DC-SOFCs was confirmed. The chars that were prepared from pistachio shells were adequate for solid fuels for utilization in DC-SOFCs.

In Situ Regeneration of Copper-Coated Gas Diffusion Electrodes for Electroreduction of CO2 to Ethylene.

A key challenge for carbon dioxide reduction on Cu-based catalysts is its low faradic efficiency (FE) and selectivity towards higher-value products, e.g., ethylene. The main factor limiting the possibilities of long-term applications of Cu-based gas diffusion electrodes (GDE) is a relatively fast drop in the catalytic activity of copper layers. One of the solutions to the catalyst stability problem may be an in situ reconstruction of the catalyst during the process. It was observed that the addition of a small amount of copper lactate to the electrolyte results in increased Faradaic efficiency for ethylene formation. Moreover, the addition of copper lactate increases the lifetime of the catalytic layer ca. two times and stabilizes the Faradaic efficiency of the electroreduction of CO2 to ethylene at ca. 30%. It can be concluded that in situ deposition of copper through reduction of copper lactate complexes present in the electrolyte provides new, stable, and selective active sites, promoting the reduction of CO2 to ethylene.

Ultrasound Supported Galvanostatic Deposition of Zn Coatings Reinforced with Nano-, Submicro-, and Micro-SiC Particles-Weak Acidic Chloride Baths.

In this paper, we present results concerning the electrochemical deposition of Zn-SiC composite coatings reinforced with nano-, submicro-, and microparticles. The influence of current density, particle size, and ultrasound on functional parameters which are especially important from a practical point of view (i.e., concentration of particles in coatings, current efficiency, morphology, reflectivity, roughness, hardness, and corrosion resistance) are investigated and discussed. Coatings were deposited from commercial, chloride-based electrolytes dedicated for the deposition of Zn coatings in a weakly acidic environment. Electrodeposited composites contained up to 1.58, 4.08, and 1.15 wt. % of SiC for coatings reinforced with nano, submicro, and micrometric particles, respectively. The process proceeded with relatively high efficiency, exceeding 80% in almost all cases. The results indicate that ultrasounds strongly increase Faradaic efficiency and affect the kinetics of electrode processes and the properties of synthesized coatings. Moreover, the obtained results show that it is possible to synthesize composite coatings with slightly higher mechanical properties while retaining corrosion resistance compared to metallic Zn coatings.

Light intensity-induced photocurrent switching effect.

A better control over processes responsible for the photocurrent generation in semiconductors and nanocomposites is essential in the fabrication of photovoltaic devices, efficient photocatalysts and optoelectronic elements. Therefore, new approaches towards photochemical properties tuning are intensively searched for. Among numerous parameters, the photocurrent polarity is of great importance to the overall performance of a device. Usually, the polarity is controlled through an alignment of electronic states/bands, tailoring of applied potential or suitable selection of incident light wavelengths. In most scenarios though, the influence of light intensity is somehow neglected and either some arbitrarily chosen, natural conditions are mimicked or this parameter is varied only in a narrow range. Here we present a ternary nanocomposite in which the persistent photocurrent polarity switching is achieved through changes in the light intensity. We also present arguments suggesting this behaviour is of a general character and should be considered also in other photochemical systems.

Heavy pnictogen chalcohalides: the synthesis, structure and properties of these rediscovered semiconductors.

This review focuses on the synthesis, properties and selected applications of heavy pnictogen chalcohalides, i.e. compounds of the MQX stoichiometry, where M = As, Sb, and Bi; Q = O, S, Se, and Te; and X = F, Cl, Br and I. The first section focuses on their synthesis and crystal structures, and the second section discusses the electronic structure on the basis of quantum chemical modelling and selected experimental data. Finally, the third section discusses their electrical, photoelectrochemical and photocatalytic properties and applications. In contrast to perovskites, chalcopyrites and kesterites, chalcohalides have attracted relatively less attention, but their structure and properties are well suited for numerous applications.

Organotitania-Based Nanostructures as a Suitable Platform for the Implementation of Binary, Ternary, and Fuzzy Logic Systems.

Titanium dioxide nanocomposites were synthesized in hierarchical architectures through the use of a 1,4-dihydroxyanthraquinone photosensitizer. In the first step, the dye was either incorporated into the TiO2 core or adsorbed on its surface. In the subsequent phase, both structures were covered with an outer layer of titanium dioxide. The structure, morphology, aggregation, spectroscopic, and electrochemical properties of the synthesized TiO2 -based materials are presented with emphasis on the photosensitization and the photocurrent switching phenomena, which are also discussed within the context of the optical logic gates implementation and fuzzy logic systems operation. We present three different interpretations of the photocurrent action spectra yielding binary, ternary, or fuzzy logic circuits.