Rational Design of the Electronic Structure of CdS Nanopowders.

In this study, various techniques, such as energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Raman spectroscopy, and spectrophotometry, were used to analyze the properties of nanometric CdS particles synthesized with varying precursor concentrations. EDX analysis revealed the nonstoichiometric composition manifested by an increase in the Cd/S ratio from 1.02 up to 1.43 with increasing precursor concentration. The growth of lattice parameters and unit cell volume accompanying preferential crystallization of the hexagonal phase along with an increasing Cd/S ratio was confirmed by XRD analysis. This indicated the presence of interstitial cadmium in nonstoichiometric Cd1+xS. The formation of shallow Cdi donor levels below the bottom edge of the conduction band impacts the bang-gap energy; a decrease from 2.56 to 2.21 eV along with increasing nonstoichiometry was observed. This is accompanied by a widening of the range of absorption of light, which creates conditions that can lead to an increase in the efficiency of redox reactions in photochemical processes.

Vibrational dynamics of ethosuximide polymorphs. Infrared absorption and inelastic neutron scattering spectroscopy and model calculations.

Commercially available and administered to the patients ethosuximide is a racemic mixture of two enantiomers, each of them exist in different conformations. The presence of the species mentioned are proven by the title experimental methods aided by DFT model calculations. Results of the latter are matched against spectroscopic data by the clustering window analysis. One type of hydrogen bonds exist in the solid forms of ethosuximide NH⋯O, leading to the polymorphic variety of the substance studied.

On relaxation and vibrational dynamics in the thermodynamic states of a chiral smectogenic glass-former.

This article shows the full characteristics (i.e., the phase situation as well as the relaxation and vibrational dynamics) of the (S)-4'-(1-methyloctyloxycarbonyl)biphenyl-4-yl 4-[5-(2,2,3,3,4,4,4-heptafluorobutoxy)pentyl-1-oxy]-benzoate chiral liquid crystal. Besides two enantiotropic chiral smectic phases (SmC* and ), the compound under study also forms the hexatic smectic phase and two crystal phases (Cr1 and Cr2). The XRD patterns imply a similar structure of both crystal phases. The sample crystallizes upon slow cooling, while the phase undergoes a glass transition during fast cooling. Upon subsequent heating, cold crystallization is observed. Our research reveals the complex relaxation dynamics in the identified thermodynamic states, e.g., two relaxations up to the beginning of cold crystallization, three modes in the crystal phases and seven processes in all smectic phases. The results from the scaling of the dielectric response indicate that the origin of the dynamics and behavior of the dielectric permittivity is the same for all phases, regardless of the change in temperature and/or external biasing field. The high value of the fragility index (mf ≈ 146) indicates that the compound under study is a fragile glass-forming system. The region of the -COO- and -COC- group stretching vibrations is primarily sensitive to the structural changes occurring during phase transitions.

Investigation of crystallization kinetics and its relationship with molecular dynamics for chiral fluorinated glassforming smectogen 3F5HPhH6.

The phase transitions, crystallization kinetics and molecular dynamics of (S)-4'-(1-methylheptylcarbonyl)biphenyl-4-yl 4-[5-(2,2,3,3,4,4,4-heptafluorobutoxy)pent-1-oxy] benzoate (3F5HPhH6) are investigated by differential scanning calorimetry, polarizing optical microscopy and broadband dielectric spectroscopy. The vitrification of the antiferroelectric hexatic phase is observed for cooling rates ≥5 K min-1 and the fragility index determined from dielectric data is mf ≈ 90. Two regimes of non-isothermal cold crystallization are distinguished using the Kissinger and Augis-Bennett methods in the heating rate ranges of 1-5 K min-1 (larger activation energy) and 8-20 K min-1 (lower activation energy). The correlation between the time of non-isothermal cold crystallization (using isothermal approximation) and relaxation time of the α-process is determined. The obtained coupling coefficient ξ ≈ 0.7 and temperature dependence of the crystallization rate Z from the Ozawa model imply a mainly diffusion-controlled cold crystallization below 275 K. The Avrami exponents n and Ozawa exponents nO determined for isothermal melt crystallization and non-isothermal cold crystallization, respectively, weigh in favour of two- rather than three-dimensional crystal growth. The transition between crystal phases is observed on heating, with a lower activation energy for 1-3 K min-1 than for 5-20 K min-1 rates.

Effect of high pressure on relaxation dynamics and crystallization kinetics of chiral liquid crystal in its smectic phase.

The impact of high pressure on molecular dynamics and the crystallization process in the smectic phase with antiferroelectric properties of partially fluorinated liquid crystal (S)-4'-(1-methyloctyloxycarbonyl)biphenyl-4-yl-4-[7-(2,2,3,3,4,4,4-heptafluorobutoxy)heptyl-1-oxy]-benzoate (3F7HPhH7) was studied by broadband dielectric spectroscopy (BDS). By analyzing dielectric spectra measured under isobaric and isothermal conditions, the changes of the activation volume vs. temperature and the activation enthalpy vs. pressure have been determined to better understand the molecular system's behaviour in terms of its thermodynamic properties. The isothermal and isobar crystallization was studied by a BDS method along the trajectory of constant relaxation time τ on the (T, p) plane. The kinetics of this process was compared to that at ambient pressure, derived from the results of differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The melt crystallization depends primarily on the formation of nuclei with the activation energy of approx. 50 kJ mol-1. This energy corresponds with the intramolecular movements of the carbonyl group in the rigid core. The behaviour of the apparent activation energies suggests that this process becomes easier with the progressive crystallized volume fractions. The obtained values of the Avrami exponent nA suggest that the crystal growth is three-dimensional. Additionally, we successfully used the scaling of dielectric response for experimental data. The scaling of the dielectric relaxation processes indicates that the dynamics and the behaviour of dielectric permittivity have the same origin for all phases regardless of the change in temperature and/or pressure.

On the relaxation dynamics of a double glass-forming antiferroelectric liquid crystal.

The relaxation dynamics in the thermodynamic states of the glass-forming antiferroelectric liquid crystal (S)-4'-(1-methyloctyloxycarbonyl) biphenyl-4-yl 4-[7-(2,2,3,3,4,4,4-heptafluorobutoxy) heptyl-1-oxy]-benzoate (3F7HPhH7) was studied by broadband dielectric spectroscopy (BDS). Two glass transitions were found at Tg,1 = 259 K and Tg,2 = 239 K, which were associated with the freezing of anti-phase motions and reorientation around the long molecular axis in the antiferroelectric SmCA* phase, respectively. The low temperature α2-relaxation process shows a Vogel-Fulcher-Tammann (VFT)-type temperature dependence of its structural relaxation time τ(T). The two secondary ß- and γ-relaxation modes ascribed to the intramolecular motions observed in the glassy state show Arrhenius behaviour of τ(T). Analysing the band shifts and the oscillator strengths of specific IR absorption bands and their temperature dependencies enables comparing them with the dielectrically determined relaxation dynamics. The kinetics of the isothermal cold crystallization in the temperature range between Tg,1 and Tg,2 was studied in detail using the Avrami and Avrami-Avramow models. This process depends primarily on the diffusion rate and the activation energy is equal to 132 kJ mol-1. The obtained values of the Avrami exponent nA suggest that the crystal growth is three-dimensional.

Can the Isothermal Calorimetric Curve Shapes Suggest the Structural Changes in Micellar Aggregates?

Inspired by the unusual shapes of the titration curve observed for many surfactants and mixed colloidal systems, we decided to extend the analysis to isothermal titration calorimetric curves (ITC) by paying special attention to potential structural changes in micellar aggregates. In this paper, we used isothermal titration calorimetry in conjunction with Scanning Transmission Electron Microscopy (STEM), Small-Angle Neutron Scattering (SANS) and X-ray Scattering (SAXS) methods support by Monte Carlo and semiempirical quantum chemistry simulations to confirm if the isothermal calorimetric curve shape can reflect micelle transition phenomena. For that purpose, we analysed, from the thermodynamic point of view, a group of cationic gemini surfactants, alkanediyl-α,ω-bis(dimethylalkylammonium) bromides. We proposed the shape of aggregates created by surfactant molecules in aqueous solutions and changes thereof within a wide temperature range. The results provide evidence for the reorganization processes and the relationship (dependence) between the morphology of the created aggregates and the conditions such as temperature, surfactant concentration and spacer chain length which affect the processes.

Abnormal Ionic Conductivities in Halide NaBi3 O4 Cl2 Induced by Absorbing Water and a Derived Oxhydryl Group.

In hunting for safe and cost-effective materials for post-Li-ion energy storage, the design and synthesis of high-performance solid electrolytes (SEs) for all-solid-state batteries are bottlenecks. Many issues associated with chemical stability during processing and storage and use of the SEs in ambient conditions need to be addressed. Now, the effect of water as well as oxyhdryl group (. OH) on NaBi3 O4 Cl2 are investigated by evaluating ionic conductivity. The presence of water and . OH results in an increase in ionic conductivity of NaBi3 O4 Cl2 owing to diffusion of H2 O into NaBi3 O4 Cl2 , partially forming binding . OH through oxygen vacancy repairing. Ab initio calculations reveal that the electrons significantly accumulate around . OH and induce a more negative charge center, which can promote Na+ hopping. This finding is fundamental for understanding the essential role of H2 O in halide-based SEs and provides possible roles in designing water-insensitive SEs through control of defects.

Exploring the Role of Manganese on Structural, Transport, and Electrochemical Properties of NASICON-Na3Fe2-yMny(PO4)3-Cathode Materials for Na-Ion Batteries.

Given the extensive efforts focused on protecting the environment, eco-friendly cathode materials are a prerequisite for the development of Na-ion battery technology. Such materials should contain abundant and inexpensive elements. In the paper, we present NASICON-Na3Fe2-yMny(PO4)3 (y = 0, 0.1, 0.2, 0.3, and 0.4) cathode materials, which meet these requirements. Na3Fe2-yMny(PO4)3 compounds were prepared via a solid-state reaction at 600 °C, which allowed to obtain powders with submicron particles. The presence of manganese in the iron sub-lattice inhibits phase transitions, which occurs at ∼95 and ∼145 °C in Na3Fe2(PO4)3, changing the monoclinic structure to rhombohedral and affecting the structural and transport properties. The chemical stability of Na3Fe2-yMny(PO4)3 was thus higher than that of Na3Fe2(PO4)3, and it also exhibited enhanced structural, transport, and electrochemical properties. The observed correlation between the chemical composition and electrochemical properties proved the ability to precisely tune the crystal structure of NASICONs, allowing cathode materials with more desirable properties to be designed.

Molecular Dynamic in Ethosuximide Glass Forming Pharmaceutical as Studied by Dielectric Relaxation Spectroscopy.

Polymorphism and molecular dynamics of ethosuximide with molecules of left- and right-handed chirality have been studied in detail using dielectric spectroscopy. Density functional theory calculations of molecular conformations and dimer formation were performed to aid the interpretation of measurements. Moving window correlation analysis of the imaginary part of dielectric permittivity spectra allowed us to complete the monotropic system of phases found by the differential scanning calorimetry method. Extra transition connected with freezing-in/activation of slow molecular motions was identified in partially ordered crystal CrI phase. In high-temperature orientationally disordered CrIh and in low-temperature conformationally disordered CrIl phases, 2 relaxation processes were detected at frequency range below 105 Hz. In glass of CONDIS CrIl, ß-relaxation was identified.

Correlation between electronic structure, transport and electrochemical properties of a LiNi1-y-zCoyMnzO2 cathode material.

Herein, the correlation between electronic structure, transport and electrochemical properties of layered LixNi1-y-zCoyMnzO2 cathode material is revealed. Comprehensive experimental studies of physicochemical properties of LixNi1-y-zCoyMnzO2 cathode material (XRD, electrical conductivity, thermoelectric power) are supported by electronic structure calculations performed using the Korringa-Kohn-Rostoker method with the coherent potential approximation (KKR-CPA) to account for the chemical disorder. It is found that even small O defects (∼1%) could significantly modify electronic density of states DOS characteristics via the formation of extra broad peaks inside the former band gap leading to its substantial narrowing. The calculated DOS values and their changes near EF tend to support experimental findings with irregular changes in the sign of thermoelectric power as well as the behavior of electrical conductivity curves as a function of Li content. Furthermore, the variations of the electromotive force of the Li/Li+/LixNi1-y-zCoyMnzO2 cell (for 0 < x < 1) remains in a quite good agreement with the relative variation of EF on DOS calculated from the KKR-CPA method.

Structural, Transport and Electrochemical Properties of LiFePO4 Substituted in Lithium and Iron Sublattices (Al, Zr, W, Mn, Co and Ni).

LiFePO4 is considered to be one of the most promising cathode materials for lithium ion batteries for electric vehicle (EV) application. However, there are still a number of unsolved issues regarding the influence of Li and Fe-site substitution on the physicochemical properties of LiFePO4. This is a review-type article, presenting results of our group, related to the possibility of the chemical modification of phosphoolivine by introduction of cation dopants in Li and Fe sublattices. Along with a synthetic review of previous papers, a large number of new results are included. The possibility of substitution of Li⁺ by Al3+, Zr4+, W6+ and its influence on the physicochemical properties of LiFePO4 was investigated by means of XRD, SEM/EDS, electrical conductivity and Seebeck coefficient measurements. The range of solid solution formation in Li1-3xAlxFePO4, Li1-4xZrxFePO4 and Li1-6xWxFePO4 materials was found to be very narrow. Transport properties of the synthesized materials were found to be rather weakly dependent on the chemical composition. The battery performance of selected olivines was tested by cyclic voltammetry (CV). In the case of LiFe1-yMyPO4 (M = Mn, Co and Ni), solid solution formation was observed over a large range of y (0 < y ≤ 1). An increase of electrical conductivity for the substitution level y = 0.25 was observed. Electrons of 3d metals other than iron do not contribute to the electrical properties of LiFe1-yMyPO4, and substitution level y > 0.25 leads to considerably lower values of σ. The activated character of electrical conductivity with a rather weak temperature dependence of the Seebeck coefficient suggests a small polaron-type conduction mechanism. The electrochemical properties of LiFe1-yMyPO4 strongly depend on the Fe substitution level.

Stochastic molecular motions in the nematic, smectic-A, and solid phases of p,p'-di-n-heptyl-azoxybenzene as seen by quasielastic neutron scattering and 13C cross-polarization magic-angle-spinning NMR.

Molecular rotational dynamics in p,p'-di-n-heptyl-azoxybenzene was studied by means of quasielastic neutron scattering (QENS) and 13C cross-polarization magic-angle-spinning (CPMAS) NMR. Fast reorientation of the hydrogen nuclei was observed by QENS in the two liquid crystalline (LC) phases nematic and smectic A, as well as in the crystalline phase. The latter could not be restricted to the -CH3 rotations alone, and a clear indication was found of some other reorientation motions persisting in the crystal. Two Lorentz-type components convoluted with the resolution function gave an excellent fit to the QENS spectra in both LC phases. The narrow (slow) component was attributed to the reorientation of the whole molecule around the long axis. The corresponding characteristic time of approximately 130 ps agreed well with the values obtained in recent dielectric relaxation and 2H NMR studies. The full width at half maximum of the broader (fast) component shows a quadratic Q dependence (Q is the momentum transfer). Hence the corresponding motions could be described by a stretched exponential correlation function and were interpreted as various "crankshaft-type" motions within the alkyl tails. The 13C CPMAS experiments fully corroborated the QENS results, sometimes considered ambiguous in complex systems.

Specific detection of glycans on a plasma membrane of living cells with atomic force microscopy.

Among the many alterations of cancer cells is the expression of different surface oligosaccharides. In this work, oligosaccharide expression in living cells (cancer and reference ones) was studied with atomic force microscopy by using lectins as probes. The unbinding force obtained for the same lectin type (concanavalin A or Sambucus nigra) suggested slightly dissimilar structures of binding sites of the same ligand type. For the lectin from Phaseolus vulgaris, a much larger unbinding force indicated a distinct structure of the binding site in cancer cells. The unbinding probability confirmed a higher content of both sialic acid and mannose-containing ligands in cancer and reference cells, respectively. These results demonstrate the potential of atomic force microscopy to directly probe the presence of molecules on a living cell surface, together with the quantitative description of their expression.