Physchem

Electrochemical properties of transition metal complexes are important parameters that should be considered for the successful application of these compounds in catalytic reactions. The proper choice of ligands and the type of its coordination allow the construction of a catalyst with high performance. The reversibility of complex oxidation is a prerequisite for successful participation in redox catalysis, while the potential values correlate with the rate of the process and necessary catalyst loading. This work summarizes the results of the exploration of a series of ruthenium carborane complexes based on the nido-C₂B₉ ligand obtained in our group by cyclic voltammetry and describes the found correlations. The knowledge of the electrochemical properties of the studied ruthenacarboranes is required for the optimization of its structure for successful catalysis of Atom Transfer Radical Polymerization or other applications. It was found that the value of the potential of reversible Ru(II)-Ru(III) transition may vary from −0.501 to 0.389 V versus Fc|Fc⁺ couple, depending on the nature of auxiliary phosphine, halogen or nitrile ligand, natural bite angle of κ²-diphosphine ligand and the presence of alkyl substituents in the carborane cage. The further oxidation towards formal Ru(IV) may be reversible or not depending on the complex structure. The found trends are in good agreement with the earlier performed findings in the field of coordination chemistry and should be considered as a tool for obtaining of complexes suitable for catalytic applications. Full article

The in situ characterization of catalysts provides important information on the catalyst and the understanding of its catalytic performance and selectivity for a specific reaction. Temperature programmed analyses (TPX) techniques for catalyst characterization reveal the role of the support on the stabilization and dispersion of the active sites. However, these can be altered at high temperatures since sintering of active species can occur as well as possible carbon deposition which hinders the active species and deactivates the catalyst. The in situ characterization of the spent catalyst, however, may expose the causes of catalyst deactivation. For example, a simple temperature programmed oxidation (TPO) analysis on the spent catalyst may produce CO and CO₂ via a reaction with O₂ at high temperatures and this is a strong indication that deactivation may be due to the deposition of carbon. Other TPX techniques such as temperature programmed reduction (TPR) and pulse chemisorption are also valuable techniques when they are applied in situ to the fresh catalyst and then to the catalyst upon deactivation. In this work, two Ni supported catalysts were considered as examples to elucidate the importance of these techniques in the characterization study of catalysts applied to the reaction of hydrogenation of CO₂. Full article

We have measured the Raman spectra of some oligothiophenes (bithiophene, terthiophene, quarterthiophene, sexithiophene and octithiophene) and polythiophene with wavelengths from 325–1064 nm (3.815–1.165 eV). All of the materials give good quality spectra with 1064 nm excitation, although there is weak background fluorescence for some of them. The UV lines of 405 and 324 nm generally provide good-quality spectra, albeit with significant fluorescence for bithiophene and quarterthiophene. Surprisingly, there is little difference between the relative intensities (i.e., the ratio of a band’s intensity as compared to the strongest band) of the spectra with the different excitation wavelengths. However, close inspection of the 2000–3200 cm⁻¹ region of octithiophene and polythiophene with 325 and 405 nm excitation shows several modes in this region that can be assigned to combinations and overtones involving the ~1440 cm⁻¹ C–C ring stretch that do not appear with 1064 nm excitation. The presence of overtones and combinations with anomalously large intensities is a hallmark of resonance Raman spectroscopy. Full article

The possibility of increasing the durability of coatings based on lime dry construction mix by introducing an additive containing synthetic aluminosilicates is substantiated. The regularities of the structure formation of the lime composite in the presence of an additive containing synthetic aluminosilicates, which additionally consists of a formation of calcium–sodium hydrosilicates and minerals of the zeolite group, an increase in the amount of chemically bound lime by 8.74%, are revealed. X-ray diffraction analysis and thermodynamic calculations have established that the mineralogical composition of the crystalline phase of the additive based on synthetic aluminosilicates is represented by thenardite, gibbsite, and the minerals of the zeolite group. It is shown that the content of the amorphous phase is 77.5%. It was found that the additive based on synthetic aluminosilicates is characterized by high activity, which is more than 350 mg/g. It was also found that the introduction of an additive based on synthetic aluminosilicates into the formulation of a lime dry mixture accelerates the curing of coatings and increases the compressive strength after 28 days of air-dry hardening by 1.9 times. Full article

A simultaneous steady-state and transient photothermal-lens modality was used for both the thermal and optical parameters of aqueous dispersed systems (carbon and silica nanoparticles, metal iodides, surfactants, heme proteins, albumin, and their complexes). Heat-transfer parameters (thermal diffusivity and thermal effusivity), the temperature gradient of the refractive index, light absorption, and concentration parameters were assessed. To simultaneously measure thermal and optical parameters, the time scale of thermal lensing (characteristic time, $t_c$) should correspond to an excitation beam size of 60–300 µm, and the relative time intervals $\left(0.5÷5\right)t_c$ and (5$÷20)t_c$ should be selected for transient and steady-state measurements, respectively. Dual-beam thermal-lens spectrometers in a mode-mismatched optical schematic at various excitation wavelengths were built. The spectrometers implement back-synchronized detection, providing different measurement conditions for the heating and cooling parts of the thermal-lens cycle. By varying the measurement parameters depending on the dispersed system, the conditions providing the suitable precision (replicability, repeatability, and reproducibility) of thermal-lens measurements were found; setups with a broad excitation beam (waist size, 150 and 300 μm) provide longer times to attain a thermal equilibrium and, thus, the better precision of measurements of thermal diffusivity. Full article

Biocidal compositions based on interpolyelectrolyte complexes and a low molecular weight antibiotic can become a promising material for creating biocidal coatings, as they combine wash-off resistance and dual biocidal action due to the biocide and the polycation. Molecular mass characteristics of polymers play an essential role in the physics and mechanical properties of the coatings. In this work, the properties of polydiallyldimethylammonium chloride (PDADMAC) coatings of various molecular weights are investigated and assumptions are made about the optimal molecular weight needed to create antibacterial compositions. To study the resistance to washing off and moisture saturation of the coatings, the gravimetric method was used, and the adhesive properties of the coatings were studied by dynamometry. It has been established that an increase in molecular weight affects the wash-off resistance of coatings, but does not affect moisture absorption and adhesion mechanics of coatings. All samples of PDADMAC were demonstrated to exhibit the same antibacterial activity. Thus, when developing systems for creating antibacterial coatings, it must be taken into account that in order to create stable coatings, the requirement to use PDADMAC with a high degree of polymerization is necessary for the coating desorption control during wash off-but not mandatory for the control of mechanical and antibacterial properties of the coating. Full article

Photo-microbes are well known to demolish rice and fruits, as farmers use chemical pesticides to overcome agricultural problems and economic damage. The use of pesticides in agriculture fails to protect crops in lower concentrations and increases the intake of chemicals that cause many human ailments. The sophisticated nanotechnology approach used in agriculture for antimicrobial activities offers several advantages for growth and improves nutrient absorption in plants. We report the green synthesis of silver nanoparticles (AgNPs) using Azadirachta indica (A. indica) and Mangifera indica (M. indica) tree leaf extract that contains antioxidants to treat numerous diseases. AgNPs tested against three plant pathogens, fungi Alternaria alternata (A. alternata), Sclerotium rolfsii (A. rolfsii), and bacteria Xanthomonas oryzae (X. oryzae), which leads to agricultural problems. The experiment was performed with different concentrations of AgNPs in μL/mL prepared using two other plants extract against fungi and bacteria during summer. The results expose the importance of plant extract in synthesizing silver nanoparticles (AgNPs) and their efficacy for microbes. A comparison among different concentrations of AgNPs (4 μL/mL, 6 μL/mL, and 10 μL/mL) was performed for two fungi (tomato disease) and bacteria (rice leaf blight disease). A-AgNPs (A. indica-AgNPs) demonstrate a greater zone of inhibition than M-AgNPs (M. indica-AgNPs), further highlighting the dependence of plants. Under in vitro conditions, the results of the antifungal activity showed zones of inhibition of 21 mm against A. alternata and 17 mm against A. rolfsii, while antibacterial activity against X. oryzae bacteria showed a 15 mm zone of inhibition at 10 mg/mL for A-AgNPs, and less for M-AgNPs. For AgNPs, the antifungal activity was characterized bya more significant area of inhibition than antibacterial activity was. The current study indicates that AgNPs with lower concentrations exhibitsuperior toxicity to microbes and may be able to manage diseases in rice and tomato, and increase plant growth. Full article

Intensity of transitions from the $b^1{{\displaystyle \sum }}_{\mathrm{g}}^{+}$ and a¹Δ_g states to the ground state ${\mathrm{X}}^3{{\displaystyle \sum }}_{\mathrm{g}}^{-}$ in the near IR emission spectrum of the S₂ molecule has been calculated by the multireference configuration interaction method taking into account spin-orbit coupling (SOC). The intensity of the$b^1{{\displaystyle \sum }}_{\mathrm{g}}^{+}$ − ${ \mathrm{X}}^3{{\displaystyle \sum }}_{\mathrm{g},Ms=\pm 1}^{-}$ transition is largely determined by the spin interaction with the electromagnetic wave, which comes from the zero-field splitting of the ground X multiplet and the SOC-induced mixing between b and ${\mathrm{X}}^3{{\displaystyle \sum }}_{\mathrm{g},0}^{-}$ states. The Einstein coefficients for the experimentally detected 0−0, 0−1, 1−1 bands of the $b^1{{\displaystyle \sum }}_{\mathrm{g}}^{+}-{\mathrm{X}}^3{{\displaystyle \sum }}_{\mathrm{g},Ms=\pm 1}^{-}$ emission system are calculated in good agreement with observations. The Einstein coefficient of the $a^1{∆}_{\mathrm{g}}-{\mathrm{X}}^3{{\displaystyle \sum }}_{\mathrm{g},Ms=\pm 1}^{-}$ magnetic dipole transition is very low, being equal to 0.0014 s⁻¹. Nonetheless, the weakest of all experimentally observed bands (the 0−0 band of the a-X_Ms=±1 transition) qualitatively corresponds to this calculation. Most importantly, we provide many other IR bands for magnetic dipole $b^1{{\displaystyle \sum }}_{\mathrm{g}}^{+}$ − ${ \mathrm{X}}^3{{\displaystyle \sum }}_{\mathrm{g},Ms=\pm 1}^{-}$ and $a^1{∆}_{\mathrm{g}}-{\mathrm{X}}^3{{\displaystyle \sum }}_{\mathrm{g},Ms=\pm 1}^{-}$ transitions, which could be experimentally observable in the S₂ transparency windows from a theoretical point of view. We hope that these results will contribute to the further experimental exploration of the magnetic infrared bands in the S₂ dimer. Full article

Changing the composition of a precursors mixture is a powerful tool to tune the structure and properties of carbonaceous nanoparticles synthesized via the solvothermal route. We have addressed the influence of the ratio of urea or thiourea to citric acid during their solvothermal treatment in dimethylformamide on the optical and sensing properties of the obtained colloidal product. It has been found that the urea-derived products are more diverse in comparison with the thiourea-based ones. The excitation-dependent fluorescence of the products and their sensitivity to mercury(II) ions have been investigated; one to three types of fluorophores have been observed in the products depending on the composition. The nanoparticles prepared in excess of urea have been found more sensitive to the heavy metal, with the sensitivity of the long-wave emission band being superior. Full article

In this work, novel microporous layers (MPLs) were developed based on fluorinated ethylene propylene (FEP), as a hydrophobic agent, and carboxymethylcellulose (CMC), as a wettability modulator and rheology controller for the inks, which were deposited onto pre-hydrophobized macroporous gas diffusion layers (GDLs). Higher CMC amounts led to higher dynamic viscosities of the inks, which induced the formation of a more compact and less cracked MPL surface. Different concentrations of CMC were tested and the experimental measurements showed a threshold limit pointing out an optimal composition that positively affected the electrochemical performances at medium-low relative humidity (RH), which is important to mitigate the need of saturating inlet gases. Durability of the best performing samples was assessed by means of an ad hoc developed accelerated stress test (AST) and compared to one of the conventional FEP-based GDMs. It was found that a lower decrement of both the output power density and the overall cell efficiency can be obtained upon the ASTs with the novel samples. Full article

Porous cellulose beads were quaternized with glycidyltrimethylammonium chloride (GTMAC) to explore a potential use of them as an adsorbent for removal of humic acid (HA) from aqueous medium. The introduction of quaternary ammonium groups was confirmed by FT-IR and XPS analysis. The content of introduced quaternary ammonium groups increased with an increase in the GTMAC concentration. The adsorption capacity increased with a decrease in the initial pH value and attained the maximum value at pH 3 and increased with an increase in the content of quaternary ammonium groups. The removal % increased with the dose of quaternized cellulose beads at both pH 3.0 and 6.0. The adsorption process obeyed the pseudo-second order kinetic model and exhibited a better fit to the Langmuir isotherm model, suggesting that the adsorption of HA is accomplished through the electrostatic interaction between a quaternary ammonium group introduced and a dissociated carboxy group of a HA molecule. The maximum adsorption capacity obtained in this study is comparable to or higher than those published by other articles. HA loaded was completely released to NaOH solutions at higher than 100 mM to regenerate the quaternized cellulose beads. The above-mentioned results clearly show that the quaternized cellulose beads prepared in this study can be used as a regenerable adsorbent with high capacity for removal of HA from aqueous medium. Full article

This paper puts forward the use of “low-cost/low-end” hydroxyapatite-based adsorbing materials prepared from Tambaqui fish cleaning residues (i.e., bones) by grinding and/or thermal annealing. The nature of raw materials and treatments practically resulted in a “zero-cost” adsorbent for atrazine pesticide and Co²⁺ ion remediation in an aqueous solution. Despite the distinctive character of the two contaminants, all adsorptions were found to follow pseudo-second order kinetics and Freundlich isotherm models. Pristine hydroxyapatite proved to be more effective in adsorbing atrazine at low concentrations due to interactions with collagen residues. Conversely, heat-treated materials demonstrated better adsorption performances for cobalt due to the removal of organic residues hindering access to the surface. On the other hand, lower adsorption affinities resulted into a faster and more efficient Co²⁺ release into water. The different behavior in terms of phosphate and cobalt release shown by the three hydroxyapatite-based absorbents can be exploited for differential liberation of targeted nutrients, with high seed germination rates. Considering circular economic principles, waste-derived hydroxyapatites may be potentially attractive for removing ionic species, minimizing water pollution stemming from heavy industry, and for their subsequent targeted release to edible plants, enhancing agricultural availability of mineral nutrients for soil fertilization. Full article

This study details the irradiation of pure (99.995%) and immaculate metallic Zinc using Nd: YAG laser (1064 nm, 10 mJ, 9–14 ns). The influence and impact of multiple laser shots on the formation of microstructures and crystal structure orientations is assessed. Arrays of ablated craters are machined on the whole surface of the target to probe the electrical and topographical characteristics of laser-treated surfaces. Irradiated samples are examined by multiple characterizing techniques such as scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), and a four-point probe for electrical conductivity measurements. SEM and AFM analysis exhibited the formation of laser-induced ripple structures with periodicity sheerly dependent on laser shots. A comparison of surface topography of the virgin and treated samples disclosed a pronounced modification in surface texture. The XRD patterns of laser shined targets indicate no momentous structural change in the crystal structure, whereas the measurements on the electrical conductivity of the irradiated surfaces exhibit an exponential descending trend with an augmentation in laser shots. Full article

Graphene is one of the most well-known two-dimensional (2D) materials that has attracted significant interest due to its unique electrical and optical properties. Being a van der Waals substrate, the fabrication of few-layered graphene by stacking a pre-defined number of graphene monolayers is essential in the field. The thickness can influence the interface interaction and therefore tune the surface electronic properties. In the study, we demonstrate a bottom-up synthesis of pre-defined few-layer graphene on SiC substrate using the thermal decomposition method and carefully characterize its thickness by the non-damageable synchrotron-radiation-based X-ray photo-electron spectroscopy (SR-XPS). By varying the photon energy, we acquire different probe depths, resulting in the different intensity ratios of graphene to SiC substrate, which is then used to estimate the thickness of the few-layer graphene. Our calculation demonstrates that the thermal decomposition method in the study can repeatedly fabricate graphene samples with expected thickness. We further compare the obtained few-layer graphene to the single-layer graphene and HOPG using the scanning tunneling microscopy (STM) technique. Our work provides accurate methods for fabricating and characterizing pre-defined few-layer graphene, providing essential knowledge in future graphene-based thin film electronics. Full article

In this work, we investigate the effect of the number of available adsorption sites for diffusing particles in a liquid confined between walls where the adsorption (desorption) phenomena occur. We formulate and numerically solve a model for particles governed by Fickian’s law of diffusion, where the dynamics at the surfaces obey the Langmuir kinetic equation. The ratio between the available number of adsorption sites and the number of total particles are used as a control parameter. The investigation is carried out in terms of characteristic times of the system for different initial configurations, as well as the cases of identical or non-identical surfaces. We calculate the bulk and surface densities dynamics, as well as the variance of the system, and demonstrate that the number of sites affects the bulk, surface distributions, and diffusive regimes. Full article

Nuclear resonant vibrational spectroscopy (NRVS) is an excellent synchrotron-based vibrational spectroscopy. Its isotope specificity and other advantages are particularly good to study, for example, iron center(s) inside complicated molecules such as enzymes. In order to investigate some small energy shifts, the energy scale variation from scan to scan must be corrected via an in-situ measurement or with other internal reference peak(s) inside the spectra to be calibrated. On the other hand, the energy re-distribution within each scan also needs attention for a sectional scan which has a different scanning time per point in different sections and is often used to measure weak NRVS signals. In this publication, we: (1) evaluated the point-to-point energy re-distribution within each NRVS scan or within an averaged scan with a time-scaled (not energy-scaled) function; (2) discussed the errorbar contributed from the improper “distribution” of ΔE_i or the averaged ΔE within one scan (E_err1) vs. that due to the different ΔE_i from different scans (E_err2). It is well illustrated that the former (E_err1) is as important as, or sometimes even more important than, the latter (E_err2); and (3) provided a procedure to re-calibrate the published NRVS-derived PVDOS spectra in case of need. This article establishes the concept that, at least for sectional NRVS scans, the energy positions should be corrected according to the time scanned rather than be scaled with a universal constant, as in a conventional calibration procedure. Full article

This paper presents the physicochemical characteristics of CeF₃ nanopowder (NP) obtained via electron evaporation. The initial NP was annealed in air (200–500 °C) for 30 min. The annealed NP was evaluated using the following methods: X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), differential scanning calorimetry-thermogravimetry (DSC-TG) and luminescence/magnetic measurements. The degree of cytotoxicity of CeF₃ nanoparticles (NPles) to cell cultures was determined. The cubic phase CeO₂ formed in CeF3 NP after annealing (500 °C). The appearance of the CeO₂ oxide phase led to an increase in the intensity of photoluminescence. Cathodoluminescence was not excited. The paramagnetic response of NPles decreased with an increase in the annealing temperature. Cerium fluoride NPles showed low cytotoxicity towards cancerous and non-cancerous cells. Annealing of the CeF₃ NP at low temperatures led to an improvement in the textural parameters of the not annealed NP. Improved texture parameters indicate the prospect of using CeF₃ as a biomedicine nanocontainer. Full article

The emergence of unexpected properties in two-dimensional materials, interfaces, and nanostructured materials opens an exciting framework for exploring new devices and applications. Recent advances in materials design and the nano structurization of novel, low-dimensional materials, surfaces, and interfaces offer a novel playground to design efficient multifunctional materials-based devices. Low-dimensional materials exhibit peculiarities in their electronic, magnetic, and optical properties, changing with respect to the bulk when they are layered down to a single layer, in addition to their high tunability. Their crystal structure and chemical bonds lead to inherent unique mechanical properties. The fabrication of van der Waals heterostructures by stacking materials with different properties, the better control of interfaces, and the tunability of the physical properties by mechanical strain, and chemical and electronic doping allow for the exploration of multifunctional devices with superconducting, magnetic, and optical properties and unprecedented degrees of freedom in terms of fabrication and tunability. Full article