High-efficiency harmonic generation is observed in a semiconducting polymer RR-P3HT [regioregular poly(3-hexylthiophene)], which exhibits a high nonlinear susceptibility [ χ (2) > 10 −6 m V −1 ] under pumping by a pulsed fibre laser. The harmonic generation efficiency in RR-P3HT is comparable or higher than that observed for liquid crystals, which are used in reference experiments to estimate the susceptibility [the quadratic susceptibility of a nematic liquid crystal NLC 1289 is χ (2) ≈ 2 × 10 −6 m V −1 ]. No generation is observed in polythiophene with a random structure, RRa-P3HT [regiorandom poly(3-hexylthiophene)], at the same pump power. It is experimentally demonstrated that a necessary condition for generating the second and third harmonics in a polymer, along with a high pump power density, is the presence of a large power density gradient (exceeding 10 13 W m −3 ). Based on a preliminary theoretical analysis, we can suggest that the quadrupole mechanism, which is a consequence of the regularity of RR-P3HT structure in the thin near-wall layer, may contribute significantly to the nonlinear radiation conversion in semiconducting polymers.

Optical nonlinearity of semiconducting organic films based on regioregular polythiophene (RR-P3HT) was explored by means of laser frequency conversion in a fiber-coupled experimental setup. Features of harmonic generation in this medium were revealed and compared with other nonlinear media. Possible enhancement of nonlinear susceptibility of RR-P3HT in high-gradient light fields is discussed as well.

The nonlinear optical properties of a nematic liquid crystal (NLC 1289) were experimentally studied according to the intensity and polarization of the pump radiation at a wavelength of 1.56 mu m. It is shown that the maximum generation efficiencies of the second and third harmonics correspond to different polarization characteristics of the main radiance. In the investigated range (10(6) horizontal ellipsis 2 center dot 10(7)W cm(-2)) the nonmonotonic dependence of the second harmonic intensity on the pump radiance power was demonstrated for the first time. In addition to this, explanation of this effect is also proposed.

It is found that the sorption recovery of copper ions from water solutions in the phase of AN-31 low basicity anion exchanger has a mixed character. It is established via diffuse reflectance spectroscopy that ions are stabilized through complexation with the participation of the functional groups of the sorbent with the formation of structures [Cu(NR 3 ) 2 (OH) 2 (H 2 O) 2 ], [Cu(NR 3 ) 3 (OH)(H 2 O) 2 ], and as a result of the physical adsorption of oxide dimers and planar-squared copper clusters. It is shown that increasing the ionic strength of a solution by introducing sodium chloride into the system greatly improves the capacity of the sorbent and leads to the uniform distribution of copper ions in the resin matrix. The similarity between the ESR spectrum parameters of copper-containing samples of the ion exchanger, obtained in a wider range of pH, is determined via ESR and testifies to the homogeneity of the stabilization positions of Cu 2+ ions. The crystalline field of tetragonal-elongated octahedron is typical of all Cu 2+ ions. All of the complexes have Cu(NO 3 ) 2 coordination nodes with the covalent bonding of Cu 2+ ions and the amine groups of the sorbent.

Supported Cu/ZSM-5 catalysts have been synthesized by ion exchange and impregnation using aqueous ammonia solutions of copper nitrate containing orbital-ordered copper ions. The state of the copper-containing component in the pore space of the catalysts and copper sorption in the catalysts have been investigated by a complex of physicochemical methods. The catalytic properties of Cu/ZSM-5 in the selective catalytic reduction of NO with propane are reported. The catalytic properties depend on the copper precursor structure and deposition method, which determine the size of the copper oxide clusters on the outer surface of zeolite crystals.

Нанесенные катализаторы Cu/ZSM-5 синтезированы методами ионного обмена и пропитки с использованием водно-аммиачных растворов азотнокислой меди, содержащих орбитально упорядоченные ионы меди. Комплексом физико-химических методов исследовано состояние медьсодержащей компоненты в пористом пространстве катализаторов и изучена сорбция меди в них. Изучены каталитические свойства Cu/ZSM-5 в реакции селективного каталитического восстановления NO пропаном. Показано, что каталитические свойства зависят от структуры исходного прекурсора меди и способа его нанесения, которые определяют дисперсность медьоксидных кластеров на внешней поверхности кристаллов цеолита.

Методами ЭПР и электронной спектроскопии изучены особенности стабилизации ионов Cu2+ в концентрированных водно-аммиачных растворах азотнокислой меди при широкой вариации концентрации ионов аммония. Установлено образование трех типов ассоциатов ионов Cu2+ с различным типом орбитального упорядочения. Установлено, что концентрация ионов аммония в растворе оказывает определяющее влияние на тип орбитального упорядочения ионов Cu2+ в ассоциатах. Во всех случаях упорядочение ионов Cu2+ в ассоциатах обусловлено наличием мостиковых ОН-групп в аксиальном или экваториальном положении комплексов [Сu(NH3)n(H2O)6 - n]2+ (n < 6). При высокой концентрации ионов аммония в растворе формируются слабо связанные ассоциаты тетрааммиаката меди с основным состоянием dx2-y2, при низкой концентрации ионов аммония в растворе формируются объемные структуры с основными состояниями dy2 и dx2-z2и ассоциаты ионов Cu2+ с основным состоянием dx2-y2 с гидроксильными группами в экваториальной плоскости и молекулами воды в аксиальном положении.

It is stated that one-dimensional conductivity in amorphous microporous carbon material (AMCM) samples is associated with the considerable imperfection of graphene fragments in the carbon material rather than the presence of unshared electrons. It is likely that the graphene fragments are formed upon the carbonization of a carbon precursor accompanied by the partial or complete removal of precursor heteroatoms. It is hypothesized that the presence of localized unpaired electrons, which give EPR spectra, is due to the formation of local defects in carbene fragments. Thus, the effects of the value of conductivity and the concentration of unpaired electrons on the power output of a fuel cell cannot be distinguished based on the experimental data with the use of an AMCM as a catalyst support. The interaction of localized paramagnetic centers with electron gas can be interpreted in terms of the C-S relaxation model.

The paper is devoted to electron paramagnetic resonance investigation of nanoparticles and aggregates of nanoparticles formed by pyrolysis of propane as well as a mixture of propane and iron pentacarbonyl. The measurement showed that the pyrolysis of the C3H8 plus Ar mixture results in the formation of a carbonaceous phase (phase I), which is quite different from that formed by the C3H8 plus Fe(CO)(5) plus Ar mixture (phase II). In phase I there is a strong oxygen effect for as-prepared samples; 75% of spins are accessible to the environmental gas via the interconnected system of microvoids and microchannels. In phase II there was a weak oxygen effect for the as-prepared samples. However, after exposition of phase II to air for 160 h, the properties of phase II have become about the same as that of phase I. A strong oxygen effect was observed for the air-exposed phase II. The line width for phase II increases monotonically with the iron content in the sample. This increase is probably related to the dipole-dipole interactions between the radical centers and the iron atoms distributed throughout the carbon matrix.

The paper is devoted to the electron spin resonance and magnetic measurements of Fe3C nanoparticles covered by a carbon structure. There is a reversible modification of the magnetic properties by the chemisorption of CO and O-2. The CO chemisorption results in the transition of the majority of the Fe3C nanoparticles from the ferromagnetic to the superparamagnetic state. The O-2 chemisorption results in the backward transition.