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The research was supported by the Russian Science Foundation (project 16-12-10004). The authors are grateful for the contributions made by our colleagues G. S. Zakharova, A. S. Konev, K. I. Borodin, Z. A. Phatakhova, A. M. Murzakaev, and V. S. Gaviko. The X-ray investigation and magnetic measurements have been performed in the Collaborative Access Center of M. N. Mikheev Institute of Metal Physics of the Ural Branch of the Russian Academy of Sciences, Yekaterinburg, Russia.

Anodic aluminum oxide (AAO) membranes are versatile nanomaterials that combine the chemically stable and mechanically robust properties of ceramics with homogeneous nanoscale organization that can be tuned to desirable pore diameters and lengths. The AAO substrates feature high surface area that is readily accessible to large and small molecules, making these nanostructures uniquely suited for many possible applications. Examples include templated self-assembly of macroscopically aligned biological membranes and substrates for heterogeneous catalysis. For further development of such applications, one would like to characterize and tune the electrostatic properties of the inner pore surface as well as the local acidity within the nanochannels. Here, we employed electron paramagnetic resonance (EPR) spectroscopy of a small molecule – ionizable nitroxide – as a reporter of the average local acidity in the nanochannels and the local electrostatic potential in the immediate vicinity of the pore surface. The former was achieved by measuring EPR spectra of this molecular probe diffusing in an aqueous phase confined in the AAO nanochannels while for the latter the nitroxide was covalently attached to the hydroxyl group of the alumina surface. We show that the local acidity within the nanochannels is increased by as much as ≈1.48 pH units vs. the pH of bulk solution by decreasing the pore diameter down to ca. 31 nm. Furthermore, the positive surface charge of the as-prepared AAO could be decreased and even switched to a negative surface charge upon annealing the membranes first to 700 °C and then to 1200 °C. For as-prepared AAO, the local electrostatic potential reaches ψ= (163 ± 5) mV for the nitroxide label covalently attached to AAO and located about 0.5 nm away from the surface. Overall, we demonstrate that the acid-based properties of the aqueous volume confined by the AAO nanopores pores can be tuned by either changing the pore diameter from ca. 71 to 31 nm or by thermal annealing to switch the sign of the surface charge. These observations provide a simple and robust means to tailor these versatile high-surface-area nanomaterials for specific applications that depend on acid-base equilibria. © 2020 Elsevier B.V. E.G.K., L.S.M., D.P.T. acknowledge the financial support of the Program 211 of the Government of the Russian Federation no. 02.A03.21.0006 , RFBR grant 18-29-12129mk , and the State Task from the Ministry of Science and Higher Education of the Russian Federation no. 0836-2020-0058 . Fabrication and SEM characterization of AAO, least-squares fitting of EPR spectra and the final preparation of the manuscript were supported by U.S. DOE Contract DE-FG02-02ER15354 to AIS. IAK acknowledges support from the Ministry of Science and Higher Education of the Russian Federation grant No. 14.W03.31.0034 for the nitroxide synthesis. NR-dimethylamine derivative has been synthesized in the context of State Task of the Institute of Organic Synthesis named after Academician I. Ya. Postovsky of the Ural Branch of the Russian Academy of Sciences (Pr. AAAA- A19-119012490006-1 ).

Nanocrystalline TiO2 samples of various compositions (up to 5 at.% Fe) with anatase structure and an average particle size of about 20 nm were synthesized using sol-gel technology. The magnetic properties of nano-TiO2: Fe was studied by electron paramagnetic resonance (EPR) and Faraday balance. The existence of an inhomogeneous magnetic state in TiO2: Fe samples of different compositions were revealed by EPR spectroscopy in a wide temperature range. The analysis of the EPR spectra in the L -, X - and Q-bands allowed us to calculate the quadratic fine structure (D, E) parameters, “axial” and “rhombic” ones, respectively. The value of D turned out to be quite small, which indicates an insignificant anisotropy, which can be ignored describing the magnetic properties of TiO2:Fe. It was shown that the temperature behavior of different separate components of the integral EPR spectra can be qualitatively interpreted in the model of coexistence in the TiO2: Fe system, mainly, dimers with a strong negative exchange interaction and isolated paramagnetic centers. No ferromagnetic state in TiO2: Fe-based samples after etching of aE-prepared state were detected.

Chemical and physical processes occurring within the nanochannels of mesoporous materials are known to be determined by both the chemical nature of the solution inside the pores/channels as well as the channel surface properties, including surface electrostatic potential. Such properties are important for numerous practical applications such as heterogeneous catalysis and chemical adsorption including chromatography. However, for solute molecules diffusing inside the pores, the surface potential is expected to be effectively screened by counter ions for the distances exceeding the Debye length. Here, we employed electron paramagnetic resonance spectroscopy of ionizable nitroxide spin probes to experimentally examine the conditions for the efficient electrostatic surface potential screening inside the nanochannels of chemically similar silica-based mesoporous molecular sieves (MMS) filled with water at ambient conditions and a moderate ionic strength of 0.1 M. Three silica MMS having average channel diameters of D = 2.3, 3.2, and 8.1 nm (C 12 MCM-41, C 16 MCM-14, and SBA-15, respectively) were chosen to investigate effects of the channel diameter at the nanoscale. The results are compared with the classical Poisson-Boltzmann (PB) double layer theory developed for diluted electrolytes and applied to a cylindrical capillary of infinite extent. While the surface electrostatic potential was effectively screened by the counter ions inside the largest channels of 8.1 nm in diameter (SBA-15), the effect of the surface electrostatic potential on local effective pH was significant for the 3.2 nm channels (C 16 MCM-14). The smaller channels of C 12 MCM-41 (2.3 nm in diameter) provided the most critical test for the PB equation that is based on a continuum electrostatic model and demonstrated its inapplicability likely due to the discrete nature of molecular systems at the nanoscale and nanoconfinement effects, leading to larger spatial heterogeneity. © 2018 American Chemical Society. *E-mail: gek1969@bk.ru (E.G.K.). *E-mail: Alex_Smirnov@ncsu.edu (A.I.S.). ORCID Alex I. Smirnov: 0000-0002-0037-2555 Author Contributions The manuscript was written through contributions from all the authors. All authors have given approval to the final version of the manuscript. Funding E.G.K., L.S.M., D.O.A., D.P.T., and A.N.T. acknowledge the financial support of the Program 211 of the Government of the Russian Federation no. 02.A03.21.0006, RFBR grants 17-03-00641 and 18-29-12129mk, and the State Task from the Ministry of the Education and Science of the Russian Federation nos. 4.9514.2017/8.9 and 4.7772.2017/8.9. A.M. and A.I.S. acknowledge the financial support of the U.S. DOE Contract DE-FG02-02ER15354 (modeling of electrostatic phenomena in the nanochannels and the final preparation of the manuscript). Notes The authors declare no competing financial interest.

Products of polymer-analogous transformations of chitosan, aminopolystyrene, and polyallylamine containing dihydroxypropylamine fragments were used as sorbents of boric acid. A dependence of their sorption properties on the structure of the main polymeric chain and its functionalization degree was found.

Cobalt-doped anatase Ti1–xCoxO2 (0 < x ≤ 0.04) nanopowders (with a particle size of 30–40 nm) were produced by the hydrothermal synthesis method. Morphology, structure, and thermal stability of the synthesized compounds were examined using transmission electron microscopy, infrared spectroscopy, and X-ray diffraction analysis. Using X-ray photoelectron spectroscopy, cobalt ions are shown to have an oxidation state of 2+, with titanium ions having a tetravalent state of Ti4+. In the as-prepared state, all investigated compounds of Ti1–xCoxO2 are paramagnetic, with the value of paramagnetic susceptibility growing in proportion to cobalt content; with the spin of cobalt ion equal to S = 3/2. Analysis of the electron paramagnetic resonance spectra reveals that doping TiO2 with cobalt (up to 2%) is accompanied by a significant increase in the concentration of F+ centers. Further growth of the cobalt content results in a relatively wide line (nearly 600 Oe) in the spectrum, with a g-factor of about 2.005, demon...

Nanopowder TiO2-0.73 % Mn was synthesized by the sol-gel method. Thermal treatment of the samples was carried out in vacuum at a temperature of 500°C. Magnetic properties were studied in the temperature range from 2 to 850 K. The effects of electron irradiation and vacuum annealing on the EPR spectra and magnetic properties of TiO2-Mn powder are discussed. It was established that a part of manganese ions in the anatase crystal lattice interacts antiferromagnetically, which causes a decrease in magnetization as compared to the result of the calculation for non-interacting ions. Vacuum annealing leads to the formation of oxygen vacancies and, at the same time, to a noticeable increase in the ferromagnetic contribution to magnetization, especially, after preliminary electron irradiation. We assume that the ferromagnetic contribution to the magnetization appears either due to incomplete compensation of antiferromagnetically directed moments of manganese ions, or due to positive exchange interactions of Mn ions via defects in the TiO2 lattice. It is shown that the temperature of magnetic disordering in samples with a spontaneous magnetic moment exceeds 600°C. © 2019, Institute for Metals Superplasticity Problems of Russian Academy of Sciences. All rights reserved.

In this paper, we performed a qualitative assessment of the surface electrical potential for individual and binary xerogels based on silica and zirconia which were synthesized by hydrolysis in aqua ammonia medium. The effect of surface charge on near surface local acidity of solid-phase compositions was studied. © 2019 Author(s). We acknowledge the financial support of the Program 211 of the Government of the Russian Federation № 02.A03.21.0006, RFBR grants 17-03-00641 and 18-29-12129mk, the State Task from the Ministry of the Education and Science of the Russian Federation № 4.9514.2017/8.9.

The report is devoted to an analysis of the structural and magnetic state of the nanocrystalline diluted magnetic semiconductors based on TiO2 doped with Fe and Co atoms. Structural and magnetic characterization of samples was carried out using X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM), X-ray absorption spectroscopy (XAS), electron paramagnetic resonance (EPR) spectroscopy, SQUID magnetometry, and the density functional theory (DFT) calculations. Analysis of the experimental data suggests the presence of non-interacting paramagnetic Fe3+ and Co2+ ions in the high-spin state and negative exchange interactions between them. The important conclusions is that the distribution of dopants in the TiO2 matrix, even at low concentrations of 3d-metal dopant (less than one percent), is not random, but the 3d ions localization and dimerization is observed both on the surface and in the nanoparticles core. Thus, in the paper the quantum mechanical model for describing the magnetic properties of TiO2:(Fe, Co) was suggested. The model operates only with two parameters: paramagnetic contribution of non-interacting 3d-ions and dimers having different exchange interactions between 3d magnetic carriers.

Acid-base equilibria and interfacial electrostatic properties of hydrated mesoporous and nanostructured alumina powders are determining factors for the use of these materials in heterogeneous catalysis and as a sorption media for filtration and chromatographic applications including life sciences. Here spin probe electron paramagnetic resonance spectroscopy of pH-sensitive nitroxides was employed to evaluate the surface charge and interfacial acid-base equilibria at the pore surface of mesoporous powders of α-Al2O3, γ-Al2O3, Al2O3 × nH2O, and basic γ-Al2O3 and nanostructured Al2O3 in the form of pristine materials and modified with aluminum-tri-sec-butoxide, hydroxyaluminum glycerate, and several phospholipids. A new pH-sensitive nitroxide probe, 4-dimethylamino-5,5-dimethyl-2-(4-(chloromethyl)phenyl)-2-ethyl-2,5-dihydro-1H-imidazol-1-oxyl hydrochloride semihydrate (nitroxide R1), has been synthesized and characterized. It was found that conditions of preparation of alumina powders exert strikingly large effects on the apparent pK a of nitroxides measured from electron paramagnetic resonance titration curves. Specifically, while the electron paramagnetic resonance titrations curves for the nitroxide R1 in mesoporous powders prepared from basic γ-Al2O3 and Al2O3 × nH2O were shifted by ΔpK a≈ +0.6 and up to ≈ +1.2 pH units respectively, the shift for γ-Al2O3 was found to be much higher: ΔpK a = +3.5. Assuming approximately the same ∆pH = 0.5–1.0 arising from a difference in the hydrogen ion activity between the bulk solution phase and that in a confined pore volume, the samples were ranked in the following order of descending magnitude of the effective surface electrostatic potential Ψ: mesoporous γ-Al2O3 > Al2O3 × nH2O > basic γ-Al2O3 > α-Al2O3. Conditions of the Al2O3 synthesis as well as the surface modification procedures were found to have profound effects on the interfacial electrostatic properties of hydrated samples that are likely related to the nature and concentration of the active sites on the alumina surfaces.

ZrO2–SiO2 xerogels have been synthesized through hydrolysis of a mixture of tetrabutoxyzirconium and tetraethoxysilane in a desiccator in a vapor of a 15% aqueous NH3 atmosphere. ZrO2–SiO2–Cu(II) xerogels were synthethized analogously through joint hydrolysis of a mixture of the organometallic precursors and copper(II) chloride. The effect of synthesis conditions on the physical and chemical properties of the resulting material has been studied. © 2016, Pleiades Publishing, Ltd.

Anodic aluminum oxide (AAO) ceramic membranes with macroscopically aligned and hexagonally packed nanopore architecture are attractive substrates for forming nanotubular lipid bilayers as well as sorption and catalytic media because of a tunable pore diameter, robust pore structure, and low fabrication cost. Here we employed continuous wave X-band (9 GHz) EPR of two pH-sensitive nitroxide radicals to assess acid–base properties AAO membranes prepared from low-cost commercial grade aluminum and compared those with commercial Anodisc membranes from Whatman, Ltd. The AAO membranes with pore diameters ≥58 ± 8 nm showed essentially the same pH inside the pores, pHint, as the bulk external solution, pHext, over the 0.1–3.0 M range of ionic strength. However, the apparent pKa of nitroxide probes inside the pores deviated from the bulk values for the nanopores of smaller diameters of ca. 29 and 18 nm. Specifically, for the latter nanopores the values of pHint were found to be 0.5–0.8 pH unit lower than the bulk p...

High-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) analysis, electron paramagnetic resonance (EPR), X-ray absorption spectroscopy (XAS), magnetic methods, and density-functional theory (DFT) calculations were applied for the investigations of Co-doped anatase TiO2 nanoparticles ( ∼ 20 nm). It was found that high-spin Co2+ ions prefer to occupy the interstitial positions in the TiO2 lattice which are the most energetically favourable in compare to the substitutional those. A quantum mechanical model which operates mainly on two types of Co2+ – Co2+ dimers with different negative exchange interactions and the non-interacting paramagnetic Co2+ ions provides a satisfactorily description of magnetic properties for the TiO2:Co system.

Some of the most important parameters of mesoporous materials are Stern potential of double electrical layer (DEL) and surface charge because of the pivotal role they play in the adsorption of charged molecular species. There are not any conventional and easy-to-perform techniques used to measure Stern potential in porous systems. The purpose of this work is to measure Stern potential in a specific case, i.e., practically cylindrical nanosized hydrated channels of the mesoporous molecular sieves (MMS) MCM-41 and SBA-15 with channel diameters ranging from 2.3 to 8.1 nm using pH-sensitive nitroxide radicals (NR). A technique for direct measurement of the near-surface (Stern) potential using pH-sensitive NR was developed. Negative and positive values of Stern potential for the positively and negatively charged surface of MMS channels were found. The ranges of pH of external solution for the near-zero charge, boost-charging of the channel surface and for dissociation of functional groups in the MMS studied were found.

Materials capable of sorbing boron(III) ions were obtained from chitosan and N,O-(2,3-dihydroxy)propylchitosan (HPC). The maximum amount of boron (3.52 mmol g−1) is extracted by chitosan at pH 4, whereas the sorption capacity for HPC at pH 4 and 13 is 1.52 and 1.97 mmol g−1, respectively.

A spin pH probe technique was used to study the influence of the channel diameter on the EPR spectra of pH-sensitive nitroxide radicals (NR) located in the channels of the mesoporous molecular sieves MCM-41 and SBA-15 with diameters ranging from 2.3 to 8.1 nm. From EPR spectra analysis and the results of the NR retention by the mesoporous molecular sieves upon washing with an aqueous KCl solution, the regularities of NR molecular location inside the channels were studied. The obtained dependence of the fraction of the radical molecules in the fast motional regime (with the rotational correlation times, τc = 2 × 10-11 s-9 × 10-11s) in the channels of the mesoporous molecular sieves as a function of pH indicates that both NR in the fast and slow motional regime (with τc = 8 × 10 -9s-7 × 10-10s) may be used for estimation of the solution acidity inside the channels and of the near-surface electrical potential. © 2013 Elsevier Inc. All rights reserved. This work was supported by the Research Program of the Ministry of the Education of the Russian Federation (2007-2011). E.G.K. thanks the Program of Cooperation “Mikhail Lomonosov” between the Ministry of Education of Russian Federation and the German Service of Academic Exchanges (DAAD). We are grateful to Dr. G. Chandrasekar for assistance in the synthesis of MMS and their characterization. Appendix A

The direct addition of glycidol to chitosan in a gel medium under exposure to ultrasound afforded the chelating aminopolymer N,O-(2,3-dihydroxy)propylchitosan with a degree of substitution up to 2.3. The sorption characteristics of the crosslinked aminopolymers with respect to boron-containing ions were estimated.

It is known that the main source of chitin and chitosan are shells of shrimp and other sea crustaceans. Alternative row sources of chitin, chitosan and its complexes are the lowest plants - mushrooms and insects. Also industrial wastes, especially from brewing of beer and manufacture of wine and ethanol can be used for extracting chitosan-containing products. The present research is aimed to the extraction of chitin and its complexes from alternative row sources, such as insects (cockroaches Pariplaneta Americana linnaeus and bees Apis mellifera lineaus), mushrooms (Amanita phalloides and Lactarius subdulius), waste banana wine (Kovibar and Urwibutso Inc.) and beer products (Bralirwa Inc., traditional sorghum) characteristic for Rwanda and their characterization using FTIR spectroscopy and elementary analysis. In chitin and its complexes extraction from all used raw sources, conditions for deproteinization were: 8% NaOH at 95 °C for 1 h and demineralization involved treatment with 6.7 % HCl at room temperature. Chitin and its complexes in the extracted samples were identified by FTIR spectroscopy using reference sample of Aspegillus Niger mushrooms. The presence of chitin parts causes the absorption band at 1650, 1552 and 1376 cm-1, which correspond to vibrations of amide groups amide I amide II and amide III, respectively. Using elemental analysis, the ratios of chitin and glucan parts were estimated and the percentage of chitin composition of all species was determined. For most of raw sources a fraction of chitin part was greater than that of glucan part. The chitin content of the samples studied ranged between 0.7-0.8 % of DM (dried mass) for wine (beer) waste products and 38% of dried mass (DM) for cockroaches. © 2016 Author(s). 2014/239, 4.1626.2014/K Russian Foundation for Basic Research, RFBR: 14-03-00898 Government Council on Grants, Russian Federation This work was supported by the Russian Foundation for Basic Research (Grant 14-03-00898), the Program 211 of the Government of the Russian Federation No 02.A03.21.0006 and the State Tasks of the Ministry of Education (Russian Federation) No. 4.1626.2014/K and No. 2014/239 and the local Grant of University of Rwanda "Chitosancontaining materials of multifunctional application for needs of Rwanda". The authors are thankful to J.P. Intwali (Rwanda), E.V. Habumugisha (Rwanda), Ch. Ukundineza (Rwanda) and D. Niyoyita (Rwanda) for capturing insects and gathering mushrooms and their initial preparation for chitin extraction.

Hydroxyalkyl derivatives of polyaminostyrene (PAS), polyallylamine (PAA), and polyethyleneimine (PEI) containing a 2,3-dihydroxypropyl moiety with a high degree of modification were synthesized. The chemical structures of the polymer transformation products were characterized with elemental analysis, Fourier transform infrared spectroscopy, 1H-NMR spectroscopy, and 13C-NMR spectroscopy in the solid state. PAS reacted with glycidol and formed poly[N-(2,3-dihydroxypropyl)aminostyrene] with a high degree of functionalization. PAA revealed primarily the graft polymerization of glycidol. In the case of PEI, primary amino groups allowed the formation of an N-derivative of 3-aminopropanediol-1,2. The PAA-based sorbent showed a high sorption capacity toward boron ions in both acidic and alkaline media. From the sorption isotherm data, the maximum sorption capacity of this sorbent at pH 4 was determined to be 3 mmol/g. The PAS-based resin maintained a high capacity between pH 9 and 12; the optimum pH was 12. The sorption capacity was 1.7 mmol/g. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43939. © 2016 Wiley Periodicals, Inc.

Cobalt-containing hybrid organo-inorganic materials based on the chitosan-SiO2, chitosan-Al2O3, and chitosan-cellulose systems were obtained. The surface structure and processes that occur during the formation of metal-containing materials, the catalytic properties of which were studied in the oxidation reactions of alkene, were investigated by EPR spectroscopy using a stable pH-sensitive nitroxyl radical, 4-dimethylamino-2-ethyl-5,5-dimethyl-2-(pyridin-4-yl)-2,5-dihydro-1H-imidazole-1-oxyl, as the adsorbed probe molecules.

Hybrid organo-inorganic materials based on the chitosan-SiO2, chitosan-Al2O3, and chitosancellulose systems are prepared. The structure of the surface is studied by means of EPR spectroscopy using the stable pH-sensitive nitroxyl radical, 4-dimethylamino-2-ethyl-5,5-dimethyl-2-pyridine-4-yl-2,5-dihydro-1H-imidazole-1-oxyl as adsorbed probe molecules, and the processes that occur during the formation of hybrid materials are considered.

N-(3-Hydroxypropyl)-β-alanine was synthesized by the reacti on of 3-aminopropanol with acrylic acid. From this ligand and basic copper carbonate, bis(N-(3-hydroxypropyl)-β-alaninato)dicopper(II) [Cu2 (C6H11NO3)2] was obtained. The structures of the chelating agent and the copper complex were studied by X-ray diffraction. The Cu(II) coordination polyhedron is a distorted square pyramid. Each ligand forms six-membered β-alaninate and propanolamine chelate rings. The propoxy group functions as a bridge. In the crystal structure, the molecules form intermolecular coordination bonds C=O→Cu, which are perpendicular to the layers. The EPR signal typical of dimeric copper complexes is not observed due to low occupancy of the excited paramagnetic triplet state. The weak paramagnetic signal from monomeric copper complex allowed recording of the 1H NMR spectrum of [Cu2 (Pro-ala) 2] with characteristic line broadening and contact shift. It follows from the obtained data that on dissolution, the complex dissociates by 40% to give monomeric copper complexes.

A comparative study of the copper metallocenter coordination sphere is carried out for a series of N-substituted β-alaninate ligands in condensed phase. For the elucidation of the effect of regular changes in dentate properties of a ligand on the complex structure, N-(bis(hydroxymethyl)methyl)-β-alanine and its copper(II) complex are specially synthesized and the complex structure is studied by the method of X-ray structural analysis. For determination of structure of the complexes in aqueous solution is applied electron spin resonance spectroscopy. Structural characteristics of β-alaninate and glycinate complexes are compared. The factors promoting formation of polynuclear complexes are considered.

The sorptivity for ions of the Irving-Williams series (Zn2+, Cu2+, Co2+, Ni2+) was estimated for the chelate sorbent N-(2-carboxyethyl)chitosan cross-linked by nanosecond electron-beam irradiation. The maximum capacity reaches 3.7 mmol/g using a mixture of the appropriate sulfates at pH 4.5. The selectivity of copper sorption is 80%. The structure of the coordination sphere of the copper complexes with N-(2-carboxyethyl)chitosan was investigated by ESR spectroscopy.

Acidic characteristics of various inorganic materials, such as silica gel, aluminum, and titanium(IV) oxides, original and modified with F− and SO 4 2− ions, in the form of hydrogels and nanostructured powders doped by copper(II) ions, are studied. It is shown that pH values inside pores of the studied sorbents (pHintr) differ from the pH of external solutions by 0.5–1.1 units. In the pores of original γ-Al2O3, the pHintr values are higher, while, in pores of γ-Al2O3 samples modified with F− и SO 4 2− , as well as nonmodified α-Al2O3, SiO2 gel, and TiO2 hydrogels, pHintr are lower compared to the pH of the external solution. It is found that pHintr decreases, as the content of Cu2+ ions in the TiO2 phase grows, and, beginning with a certain moment, it coincides with pH of an equilibrium solution. The pK a values of functional group dissociation in some materials are determined. It is shown that, using spin probes, that is, pH-sensitive nitroxyl radicals, the electrostatic potential of the surface of nanostructured TiO2 can be estimated.

Three techniques of spin labeling have been applied to nanostructured SiO2 and have been tested by electron paramagnetic resonance spectroscopy of pH-sensitive nitroxide radicals (NRs). The best technique was based on preliminary interaction of the pH-sensitive NR bromomethyl-2,2,3,5,5-pentamethylimidazoline-1-oxyl with aminopropyltriethoxy-silane (APTES) in the presence of trioctylamine and further treatment of the nanostructured SiO2 with the hydrolyzed product and acetic anhydride. It was found that there are two types of location of the pH-sensitive NRs (spin labels) on the surface of nanostructured silica. The spin labels of the first type located near the surface of nanostructured SiO2 (“slow-motional” NR) have been used to measure near-surface electrical potential at the site of NR N–O• fragment location, q equal to −90 mV. The NR molecules of the second type which were positioned well far from the nanostructured SiO2 surface (“fast-motional” NRs) were employed to establish the regularities of mutual changes in the NR form and nanoparticle surface charge with variations in pH of external bulk solution (pHext). The pH-sensitive NRs covalently attached to the SiO2 surface were successfully employed for the study of surface charge in the drying process with a rise of temperature up to 375 K. A negative surface charge was shown to decrease due to reducing an ionization degree of the surface silanol groups. This process was found to be reversible at re-adsorption of water molecules. © 2015, Springer-Verlag Wien.

V2 − yTiyO5 − δ · nH2O (0 < y < 1.33, layered structure) and Ti1 − yVyO2 + δ · nH2O (0 < y < 0.25, anatase structure) solid solutions are synthesized by a sol-gel process. ESR spectra are used to assess the state of tetravalent vanadium in the solid solutions before and after calcination at 350°C and after intercalation with K+. Six types of ESR signals arising from paramagnetic ions in different environments are identified. Computer simulation is used to evaluate the ESR parameters of the materials studied.

The distribution of Cu2+ ions in ZrO2 and sulfated ZrO2 hydrogel phases was studied by EPR spectroscopy and voltammetry. The formation of the following three types of copper structures was observed: mononuclear Cu2+ complexes (A), magnetic associates (B), and Cu2+ compounds (C) that gave no EPR signals under the conditions used in the spectroscopic measurements. The specific catalytic activity of various Cu2+ compounds in the liquid-phase reaction of 2,3,5-trimethyl-1,4-hydroquinone oxidation was determined. The copper complexes C were found to exhibit the highest catalytic activity.

Composite materials (CMs) based on zirconia xerogels and powdered cellulose (PC) were synthesized. The effect of the CM surface charge on their complexing properties with respect to Cu2+ ions and on the catalytic activity of the samples in model reactions of the decomposition of H2O 2 and the oxidative dehydrogenation of trimethylhydroquinone with atmospheric oxygen was analyzed. It was experimentally proved that the use of PC for the synthesis of ZrO2-based CMs, as in the case of previously studied CMs based on SiO2 and TiO2, leads to an increase in the specific surface area Ssp and a decrease in the negative electric potential of their surface. The surface charge, sorption method, and the composition of the buffer solution used for sorption have a significant effect on the copper(II) content in the CM phase, the distribution pattern, and the composition of the sorbed copper(II) compounds and on the catalytic activity of the synthesized Cu2+-containing CMs. © Pleiades Publishing, Ltd., 2014. This work was supported by the Russian Foundation for Basic Research, (project no. 14 03 00898) and Program 211 of the Government of the Russian Federation (grant no. 02.03.21.0006).

Cohydrolysis of tetrabutoxytitanium and tetraethoxysilane in a desiccator in the presence of water vapor produced a TiO2-SiO2 binary xerogel and its Cu(II)-containing analog. The hydrolysis was performed without using either a solvent, or redox catalysts. The effect of the synthesis conditions on the physicochemical properties of the obtained material was studied. © 2014 Pleiades Publishing, Ltd.

The influence of synthesis conditions of adjusted sorbents based on polyethylenepolyamine on catalytic properties of their Cu(II)-containing samples has been studied. It was shown that adjustment of sorbents leads to a significant increase in activity of Cu(II)-containing catalysts on their base.

A procedure was developed for preparation of poly[N-(2,3-dihydroxypropyl) aminostyrene] via successive stages of nitration, reduction, and glycidol treatment of polystyrene, which gives the polymer with a maximal degree of functionalization. The composition and structure of the intermediates and end products of the polymer-analogous reactions were characterized by elemental analysis, IR spectroscopy, and solid-state 13C NMR spectroscopy. The sorption characteristics of poly[N-(2,3-dihydroxypropyl)aminostyrene] toward boroncontaining ions were assessed. © 2013 Pleiades Publishing, Ltd. This study was financially supported by the Ural Division, Russian Academy of Sciences (project no. 12-S-3-1003) and by the Council of the President of the Russian Federation for Young Scientists and Leading Scientific Schools Supporting Grants (project no. МК-5745.2013.3).

© 2012 Kovaleva and Molochnikov, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. pH-Sensitive Nitroxide Radicals for Studying Inorganic and Organo-Inorganic Materials and Systems

Composite materials (CMs) were synthesized from silica and titania xerogels. The influence of the charged state of the CM surface on complexation with Cu2+ ions and the catalytic activity of the obtained samples in model oxidative dehydrogenation of trimethylhydroquinone with air oxygen was analyzed. Using powder cellulose in the synthesis of CMs increased the specific surface of inorganic dioxides and lowered the negative electric potential of the CM surface. This caused a redistribution of the ratio between different types of copper structures formed in the samples during the copper sorption and led to the catalytic activity of the CMs. © 2011 Pleiades Publishing, Ltd.

The character of the copper(II) distribution over the surface of titania gel modified with powder cellulose has been studied by EPR. Three types of copper(II) compounds have been identified: mononuclear complexes, magnetic associates, and copper(II) compounds that do not give rise to an observable EPR spectrum at the used frequency and temperature. The modification of titania gel has been shown to have an effect on the relative contents of these compounds. © Pleiades Publishing, Ltd., 2010.

The synthesis of heterogenized vanadyl acetylacetonate was accomplished by alkylation of a chloromethylated styrene—divinylbenzene copolymer via activation by Co(II) complexes. The effect of heterogenization on the structure of the complexes and their catalytic properties in the peroxide oxidation of anthracene was investigated by kinetic studies and EPR spectroscopy. Increased stability during oxidation of the catalytic centers of the polymer sample as compared with homogeneous vanadyl acetylacetonate was demonstrated.

Complex vanadium and titanium oxides modified by copper ions are studied by the electrochemical and ESR methods. Oxides Cu x V2-y Ti y O5-δ•nH2O (0

Liquid-phase oxidative dehydrogenation of 2,3,5-trimethyl-1,4-hydroquinone in the presence of titanium dioxide hydrogel was studied by a kinetic method. Associative interactions between the substrate, oxidant, and gel were detected by voltammetry and ESR and IR spectroscopy. Russian Foundation for Basic Research

ESR was used to examine special features of complex formation of copper (II) in aminophosphorus-containing ampholytes. It was shown in the resin phase, according to the pH value of the equilibrium solution, degree of hydration, phosphorylation and the type of ampholyte, various spectra with different parameters are observed. To obtain information about the composition of copper complexes in ampholytes, ESR spectra of Cu(II) were studied in dilute solutions of α-methylene phosphonic acids and anion-exchange resins, which were used to obtain the ampholytes examined. The most probable composition of complexes in the systems studied was determined and it was shown that stereochemistry of coordination centres in ion-exchange resins is comparatively slightly distorted, compared with low molecular weight analogues. A comparative evaluation was made of the strength of complexes formed in resin by adsorption from solutions with varying salt composition and pH value. The effect of hydration on the rearrangement of the coordination sphere of copper in ampholytes was explained.

1. Complexes of Cu(II) with polymeric Schiffs bases prepared by the reaction of the AN-20 ion-exchanger with aromatic and heterocyclic aldehydes can be used as heterogeneous catalysts of oxidation of 2,3,6-trimethylphenol by hydrogen peroxide. 2. Based on an analysis of the data from the IR and EPR spectra, a conclusion was drawn concerning the character of the change in the catalytic centers during the oxidation reaction.