Investigation of spectroscopic and electrical properties of doped poly(pyrrole-3-carboxylic acid).

The spectroscopic and electrical properties of poly(pyrrole-3-carboxylic acid) doped with p-TSA- (p-toluenesulfonate) and AQS- (anthraquinone sulfonate) were investigated. The variation in electrical conductivity as a function of temperature shows that the systems have semiconductor-like electrical characteristics. The investigated polymers exhibit 3D conductivity and less than 0.6 eV energy gaps. The IR and Raman spectra show that the charge carriers are polarons and bipolarons. Doping the poly(pyrrole-3-carboxylic acid) increases the number of charge carriers. Electron paramagnetic resonance has shown that localized polarons and bipolarons are formed within these polymers.

Molecular Dynamics of Steroidal Rotors Probed by Theoretical, Spectroscopic and Dielectric Methods.

Our study focuses on molecular rotors with fast-moving rotators and their potential applications in the development of new amphidynamic crystals. Steroidal molecular rotors with a dipolar fluorine-substituted phenyl group as the rotator were synthesized and characterized. Three different rotors were investigated with varying numbers of fluorine atoms. A comprehensive analysis was performed using vibrational spectroscopy (Raman, FT-IR), electronic circular dichroism (ECD), and dielectric response to understand the behavior of the investigated model rotors. The results were supported by theoretical calculations using Density Functional Theory (DFT) methods. The angle-dependent polarized Raman spectra confirmed the crystallinity of the samples. Nearly frequency and temperature-independent permittivity suggest low-frequency librational motion of stators. An in-depth analysis of ECD spectra revealed high conformational flexibility in solution, resulting in low ECD effects, while in the solid-state with restricted rotation, significant ECD effects were observed. These findings shed light on the conformational behavior and potential applications of the studied steroidal molecular rotors.

Structural studies and selected physical investigations of LiCoO2 obtained by combustion synthesis.

Nanocrystalline powders of LiCoO2 were synthesized using a modified solution combustion method, and the effects of the annealing temperature (450-900 °C) on structure and composition were investigated using various methods, including XRD, SEM, EPR, and electrical studies. It was found that, as the process temperature increases, the value of the specific surface area decreases, and, hence, the size of the crystallites increases. XRD analysis showed that phase-pure LiCoO2 material was maintained without additional phases. EPR studies revealed the presence of two Ni3+ complexes resulting from Ni impurities. The electrical properties of the studied LiCoO2 samples were investigated by using impedance spectroscopy. Comparison of the effect of annealing temperature on electrical conductivity shows a very interesting behavior. As the annealing temperature increases, the DC conductivity value increases, reaching a maximum at a temperature of 500 °C. However, further increase in the annealing temperature causes a steady decrease in the DC conductivity.

Slick Synthetic Approach to Various Fluoroalkyl Silsesquioxanes-Assessment of their Dielectric Properties.

We present a smart and efficient methodology for the synthesis of a variety of fluorinated silsesquioxanes (SQs) with diverse Si-O-Si core architecture. The protocol is based on an easy-to-handle and selective hydrosilylation reaction. An investigation on the placement of the reactive Si-HC=CH2 vs. Si-H in the silsesquioxane, as well as silane vs. olefin structure, respectively, on the progress and selectivity of the hydrosilylation process, was studied. Two alternative synthetic pathways for obtaining a variety of fluorine-functionalized silsesquioxanes were developed. As a result, a series of mono- and octa- T8 SQs, tri- 'open-cage' T7 SQs, in addition to di- and tetrafunctionalized double-decker silsesquioxane (DDSQ) derivatives, were obtained selectively with high yields. All products were characterized by spectroscopic (NMR, FTIR) techniques. Selected samples were subjected to the measurements revealing their dielectric permittivity in a wide range of temperatures (from -100 °C to 100 °C) and electric field frequencies (100-106 Hz).

Spectroscopic and Structural Study of a New Conducting Pyrazolium Salt.

The increase in conductivity with temperature in 1H-pyrazol-2-ium 2,6-dicarboxybenzoate monohydrate was analyzed, and the influence of the mobility of the water was discussed in this study. The electric properties of the salt were studied using the impedance spectroscopy method. WB97XD/6-311++G(d,p) calculations were performed, and the quantum theory of atoms in molecules (QTAiM) approach and the Hirshfeld surface method were applied to analyze the hydrogen bond interaction. It was found that temperature influences the spectroscopic properties of pyrazolium salt, particularly the carbonyl and hydroxyl frequencies. The influence of water molecules, connected by three-center hydrogen bonds with co-planar tetrameters, on the formation of structural defects is also discussed in this report.

Proton dynamics in superprotonic Rb3H(SeO4)2 crystal by broadband dielectric spectroscopy.

Broadband dielectric and AC conductivity spectra (1 Hz to 1 THz) of the superprotonic single crystal Rb3H(SeO4)2 (RHSe) along the c axis were studied in a wide temperature range 10 K < T < 475 K that covers the ferroelastic (T < 453 K) and superprotonic (T > 453 K) phases. A contribution of the interfacial electrode polarization layers was separated from the bulk electrical properties and the bulk DC conductivity was evaluated above room temperature. The phase transition to the superprotonic phase was shown to be connected with the steep but almost continuous increase in bulk DC conductivity, and with giant permittivity effects due to the enhanced bulk proton hopping and interfacial electrode polarization layers. The AC conductivity scaling analysis confirms validity of the first universality above room temperature. At low temperatures, although the conductivity was low, the frequency dependence of dielectric loss indicates no clear evidence of the nearly constant loss effect, so-called second universality. The bulk (intrinsic) dielectric properties, AC and DC conductivity of the RHSe crystal at frequencies up to 1 GHz are shown to be caused by the thermally activated proton hopping. The increase of the AC conductivity above 100 GHz could be assigned to the low-frequency wing of proton vibrational modes.

Toward a new type of proton conductor based on imidazole and aromatic acids.

A new approach towards achieving proton conducting materials based on aromatic acids and heterocyclic bases was proposed. It can lead to a new material in which all hydrogen bonding interactions are of medium or weak strength and rotations of the base and acid molecules are possible. If the above conditions are met, one can expect a high value of proton conductivity governed by the Grotthuss mechanism. Two salts of imidazole, one with benzoic acid having one carboxylic acid group and another with salicylic acid having a carboxylic and hydroxyl group located in the ortho position, were synthesized. Physical properties of these newly synthesized proton conducting salts were investigated using experimental and theoretical methods. The structures of these salts were studied by X-ray diffraction and 1H and 13C NMR techniques. The intermolecular interactions in the salts were analyzed by DFT calculations, within the QTAiM theory, and by Hirshfeld surface analysis. The π-π interactions, the proton conduction pathways, and the transport mechanism are also discussed.

First universality of conductivity spectra in superprotonic (NH4)3H(SO4)2 single crystal.

We present the frequency study of electric conductivity in the superprotonic single crystal in a wide temperature range covering the superprotonic phase I and the low conducting, ferroelastic phase II. The data below microwave frequencies are analyzed using the Summerfield scaling method to check for presence of the first universality. The scaled conductivity obtained from the raw experimental data plotted versus scaled frequency do not show the universality because it contains, in a low temperature range, steps related to relaxational dielectric contribution. The contribution, evidenced by a temperature study of frequency dependence of ε″, presumably comes from polar ammonia and therefore does not reflect properties of the hopping motion of mobile ions. To get rid of it, the conductivity is calculated using the impedance data obtained from the fitting procedure of the Nyquist plots. The resulting scaled ac conductivity plot forms a single curve in a wide temperature range. Thus, (NH4)3H(SO4)2 meets criteria for the first universality, despite the fact that it undergoes the structural, superionic phase transition in the temperature range studied.

Uncommon first universality of conductivity in superprotonic (NH4)3H(SeO4)2 single crystals.

The proton conducting crystal (NH4)3H(SeO4)2 is examined to check whether the first universality of conductivity spectra is sensitive to subtle changes in the crystal structure and proton dynamics caused by external pressure. The ac conductivity was measured along the trigonal c axis by means of impedance spectroscopy, in the frequency range from 100 Hz to 1 MHz, at temperatures 250 K < T < 330 K and pressures 0.1 < p < 380 MPa. The ac conductivity characteristics were analyzed using the Summerfield scaling procedure. In the temperature range of the experiment the master curve is strongly disturbed by the structural phase transition at Tc1 = 273 K but the scaled spectra superimpose within the temperature range of each individual phase (below and above Tc1). The effect of pressure on the scaled conductivity spectra considered separately for each of the studied phases is similar to that caused by temperature. This means that both stimuli give rise to an acceleration of the dynamics of protons and consequently to an increase in conductivity. The evolution of the scaled conductivity spectra with pressure close to the phase boundary between the triclinic, ferroelastic phase III (P1[combining macron]) and the trigonal, superionic phase II (R3[combining macron]) points to the mixing of phase III with inclusions of phase II.