I. Koptyug | Siberian Branch of the Russian Academy of Sciences (original) (raw)

Papers by I. Koptyug

Journal of Physics: Conference Series

The Journal of Physical Chemistry C, 2016

Nature Communications, 2015

Supplementary Figure 1 | Ultrafast D-T 2 correlation experiment for the mixture of hexane and pen... more Supplementary Figure 1 | Ultrafast D-T 2 correlation experiment for the mixture of hexane and pentadecane. (a) Experimental data after the Fourier transform in the spatial frequency (k) dimension, the compensation of the spatial variations of the measurement coil sensitivity and the removal of the data not affected by the frequency sweep pulse. (b) The first row along the t direction. (c) The first column along the q direction (q = g/2, where  is the gyromagnetic ratio,  is the effective length of the diffusion gradient and g is the amplitude of the diffusion gradient). (d) The end portion of the last row, illustrating the noise level. SNR was estimated to be 8000. (e) 1D Laplace inversion of the first row. The resulting T 2 distribution includes only a single peak. (f) 1D Laplace inversion of the first column. The resulting D distribution includes only a single main peak (and an artificial peak at long D).

Angewandte Chemie International Edition, 2014

The development of microfluidic processes requires information-rich detection methods. Here we in... more The development of microfluidic processes requires information-rich detection methods. Here we introduce the concept of remote detection exchange NMR spectroscopy (RD-EXSY), and show that, along with indirect spatial information extracted from time-of-flight data, it provides unique information about the active regions, reaction pathways, and intermediate products in a lab-on-a-chip reactor. Furthermore, we demonstrate that direct spatial resolution can be added to RD-EXSY efficiently by applying the principles of Hadamard spectroscopy.

The Journal of Physical Chemistry B, 2008

To gain a better understanding of the advection of reaction fronts in a porous medium, we conside... more To gain a better understanding of the advection of reaction fronts in a porous medium, we consider the similarities and the differences between the advection of wavefronts in a packed bed and in a flat gap or a pipe. The model calculations are based on the reaction-diffusion-advection equation for cubic autocatalysis, with the flow field in a gap taken into account explicitly. The analysis performed allows us to conclude that, in the "wide gap" limit, i.e., when the ratio of the gap (or pore) width to the front width is large, for the adverse flow in a porous medium one can expect the formation of stationary wavefronts for a wide range of flow velocities, if one takes into account that advection in a porous medium can effectively quench the axial diffusion of an autocatalyst. These predictions are verified experimentally for a non-oscillatory autocatalytic reaction, viz., the oxidation of thiosulfate with chlorite, carried out in a packed bed of glass beads. It is demonstrated for the first time that, in the case of an adverse flow, the stationary wavefronts in the "wide gap" limit are indeed observed for this reaction, and this limit can be achieved by, e.g., increasing the concentrations of the key reactants. We suggest that the observations of stationary wavefronts in the oscillatory Belousov-Zhabotinsky reaction reported earlier can be accounted for in similar terms. The formation of stationary wavefronts in a packed bed is favored owing to the much larger flow dispersion effects (the ratio of the largest flow velocity to the average flow velocity) in a porous medium as compared to flow in a gap or a pipe. Nevertheless, for a correct description of the effects of advection on the wavefront propagation, it is not appropriate to substitute the dispersion coefficient for diffusivity in the reaction-diffusion-advection equation.

The Journal of Physical Chemistry A, 2007

Magnetic resonance imaging was used for two-dimensional temperature visualization of chemical wav... more Magnetic resonance imaging was used for two-dimensional temperature visualization of chemical waves propagation in the autocatalytic exothermal reaction of thiosulfate oxidation by chlorite. The technique presented is based on the temperature dependence of the water chemical shift. Temperature maps were acquired by employing the TurboFLASH imaging method. The results obtained allow one to judge about directions of buoyancy flows. Two types of convection critical modes in a vertical tube during the wave propagation were detected.

Lab on a Chip, 2013

The heterogeneous hydrogenation reaction of propene into propane in microreactors is studied by r... more The heterogeneous hydrogenation reaction of propene into propane in microreactors is studied by remote detection (RD) nuclear magnetic resonance (NMR). The reactors consist of 36 parallel microchannels (50 × 50 μm(2) cross sections) coated with a platinum catalyst. We show that RD NMR is capable of monitoring reactions with sub-millimeter spatial resolution over a field-of-view of 30 × 8 mm(2) with a steady-state time-of-flight time resolution in the tens of milliseconds range. The method enables the visualization of active zones in the reactors, and time-of-flight is used to image the flow velocity variations inside the reactor. The overall reaction yields determined by NMR varied from 10% to 50%, depending on the flow rate, temperature and length of the reaction channels. The reaction yield was highest for the channels with the lowest flow velocity. Propane T1 relaxation time in the channels, estimated by means of RD NMR images, was 270 ± 18 ms. No parahydrogen-induced polarization (PHIP) was observed in experiments carried out using parahydrogen-enriched H2, indicating fast spreading of the hydrogen atoms on the sputtered Pt surface. In spite of the low concentration of gases, RD NMR made imaging of gas phase hydrogenation of propene in microreactors feasible, and it is a highly versatile method for characterizing on-chip chemical reactions.

Journal of the American Chemical Society, 2014

To date, only metal-containing hydrogenation catalysts have been utilized for producing substanti... more To date, only metal-containing hydrogenation catalysts have been utilized for producing substantial NMR signal enhancements by means of parahydrogen-induced polarization (PHIP). Herein, we show that metal-free compounds known as molecular tweezers are useful in this respect. It is shown that ansa-aminoborane tweezers QCAT provided (20-30)-fold signal enhancements of parahydrogen-originating hydrogens in (1)H NMR spectra. Nuclear polarization transfer from the polarized hydrogens to (11)B nuclei leads to a 10-fold enhancement in the (11)B NMR spectrum. Moreover, our results indicate that dihydrogen activation by QCAT and CAT tweezers is carried out in a pairwise manner, and PHIP can be used for understanding the activation mechanism in metal-free catalytic systems in general.

Applied Magnetic Resonance, 2013

Immobilized iridium complexes synthesized using [Ir(COD)Cl] 2 by anchoring on hydrous and anhydro... more Immobilized iridium complexes synthesized using [Ir(COD)Cl] 2 by anchoring on hydrous and anhydrous silica gels were studied in terms of generating parahydrogen-induced polarization (PHIP) in the gas-phase hydrogenation of propylene and propyne. Distinguishing differences in the hydrogenations of carboncarbon double and triple bonds were found. It has been shown that in the double bond hydrogenation both catalysts are very active even at 25°C. The reaction yield in continuous flow experiments is more than 70 %, whereas the obtained PHIP degrees are very low. In the case of the triple bond hydrogenation, a more or less active hydrogenation reaction was observed at relatively high temperatures (&70-80°C) for the catalyst immobilized on anhydrous silica, while the catalyst immobilized on hydrous silica was inactive at these temperatures. Contrary to the double bond hydrogenation, the triple bond hydrogenation provided significant signal enhancements observed in 1 H nuclear magnetic resonance spectra for the signals corresponding to protons of vinyl fragments of product propylene in both PASADENA and ALTADENA experiments. The catalyst, however, is not stable under the triple bond hydrogenation reaction conditions, and deactivates within several minutes. It was also found that at higher temperatures (100-120°C), this

Angewandte Chemie International Edition, 2012

This work was supported by the Russian Government (grant 11.G34.31.0045), RFBR (11-03-93995-CSIC_... more This work was supported by the Russian Government (grant 11.G34.31.0045), RFBR (11-03-93995-CSIC_a, 11-03-00248-a, 12-03-00403-a), the program of support of leading scientific schools (NSh-7643.2010.3), and the Academy of Finland (123847 and 139839). We thank Dr. J. Lounila for fruitful discussions. I.V.K. thanks Prof. C. Bianchini and Dr. P. Barbaro (ICCOM-CNR, Sesto Fiorentino, Firenze, Italy) for providing the sample of catalyst [Rh(cod)(sulfos)]/ SiO 2. V.V.Z. thanks I. E. Beck for providing the sample of catalyst Rh/ TiO 2 .

Angewandte Chemie International Edition, 2010

, SB RAS (67, 88), the program of support of leading scientific schools (NSh-7643.2010.3) and FAS... more , SB RAS (67, 88), the program of support of leading scientific schools (NSh-7643.2010.3) and FASI (state contract 02.740.11.0262). I.V.K. thanks Prof. C. Bianchini and Dr. P. Barbaro (ICCOM-CNR, Sesto Fiorentino, Firenze, Italy) for providing the sample of catalyst [Rh(cod)(sulfos)]/SiO 2 .

Angewandte Chemie International Edition, 2008

Journal of the American Chemical Society, 1996

Two modifications of a conventional inversion-recovery experiment which exclude the effect of spe... more Two modifications of a conventional inversion-recovery experiment which exclude the effect of spectral diffusion on the measured spin-lattice relaxation times of rapidly tumbling nitroxide spin labels are described. In the first approach an almost uniform inversion is achieved by means of specially designed pulse trains with excitation patterns which match the three-line nitroxide ESR spectrum. In the second approach we essentially combine an inversion-recovery for the M I ) 0 line with an analog of a pulsed ELDOR technique for M I ) (1 lines in a single experiment. This allows us to reconstruct the recovery of the total magnetization of the ensemble of radicals which is not affected by spectral diffusion. The spin-lattice relaxation times of several nitroxide spin labels in different homogeneous and microheterogeneous environments are measured and compared. The temperature dependence of T 1 times is compared for two solvents, methylcyclohexane and carbon disulfide, which differ in nuclear spin concentration by almost a factor of 1000. The reported experimental evidence suggests that interactions with the nuclear spins of a solvent do not significantly contribute to the spin-lattice relaxation of nitroxide spin labels.

Russian Journal of Applied Chemistry, 2011

Methodological foundations of a physical analysis of the structure of a crystallized binary syste... more Methodological foundations of a physical analysis of the structure of a crystallized binary system constituted by 5,6-(3′,4′-furazano)-1,2,3,4-tetrazine-1,3-dioxide and 2,4-dinitro-2,4-diazapentane by optical microscopy, NMR tomography, and X-ray diffraction analysis were developed. First results were obtained, which characterize specific features of the crystallization process and parameters of crystals being formed in a eutectic mixture and molecular compound.

NATO Science Series II: Mathematics Physics and Chemistry, 2006

ABSTRACT Development and study of novel nanoporous adsorbents is a very challenging goal of curre... more ABSTRACT Development and study of novel nanoporous adsorbents is a very challenging goal of current material science research. Among these materials are new alumosilicates, alumo- and iron phosphates, MCMs, SBAs, MOFs, carbon sieves, etc., with the pore size of few nanometers. Less progress is made in developing new adsorbents with relatively large pores of 7-20 nm.

Journal of Engineering Physics and Thermophysics, 1999

We present results on acoustic drying of wood (pine). By use of a tomograph, we obtained the dist... more We present results on acoustic drying of wood (pine). By use of a tomograph, we obtained the distribution of moisture in the cross section of a specimen before and after acoustic action exerted on it. It is found that in the direction of the normal to the annual rings this action is not monotonic, but rather it varies periodically. Affected

NATO Science Series II: Mathematics Physics and Chemistry, 2006

Modern magnetic resonance is an extremely broad field of scientific research, which embraces a va... more Modern magnetic resonance is an extremely broad field of scientific research, which embraces a vast variety of experiments and techniques. To better define the place of NMR imaging in magnetic resonance, it might be advantageous to consider the majority of the magnetic resonance (MR) experiments as being performed in a multidimensional space of frequencies, spatial coordinates and time. Each particular

Journal of Physics: Conference Series

The Journal of Physical Chemistry C, 2016

Nature Communications, 2015

Supplementary Figure 1 | Ultrafast D-T 2 correlation experiment for the mixture of hexane and pen... more Supplementary Figure 1 | Ultrafast D-T 2 correlation experiment for the mixture of hexane and pentadecane. (a) Experimental data after the Fourier transform in the spatial frequency (k) dimension, the compensation of the spatial variations of the measurement coil sensitivity and the removal of the data not affected by the frequency sweep pulse. (b) The first row along the t direction. (c) The first column along the q direction (q = g/2, where  is the gyromagnetic ratio,  is the effective length of the diffusion gradient and g is the amplitude of the diffusion gradient). (d) The end portion of the last row, illustrating the noise level. SNR was estimated to be 8000. (e) 1D Laplace inversion of the first row. The resulting T 2 distribution includes only a single peak. (f) 1D Laplace inversion of the first column. The resulting D distribution includes only a single main peak (and an artificial peak at long D).

Angewandte Chemie International Edition, 2014

The development of microfluidic processes requires information-rich detection methods. Here we in... more The development of microfluidic processes requires information-rich detection methods. Here we introduce the concept of remote detection exchange NMR spectroscopy (RD-EXSY), and show that, along with indirect spatial information extracted from time-of-flight data, it provides unique information about the active regions, reaction pathways, and intermediate products in a lab-on-a-chip reactor. Furthermore, we demonstrate that direct spatial resolution can be added to RD-EXSY efficiently by applying the principles of Hadamard spectroscopy.

The Journal of Physical Chemistry B, 2008

To gain a better understanding of the advection of reaction fronts in a porous medium, we conside... more To gain a better understanding of the advection of reaction fronts in a porous medium, we consider the similarities and the differences between the advection of wavefronts in a packed bed and in a flat gap or a pipe. The model calculations are based on the reaction-diffusion-advection equation for cubic autocatalysis, with the flow field in a gap taken into account explicitly. The analysis performed allows us to conclude that, in the "wide gap" limit, i.e., when the ratio of the gap (or pore) width to the front width is large, for the adverse flow in a porous medium one can expect the formation of stationary wavefronts for a wide range of flow velocities, if one takes into account that advection in a porous medium can effectively quench the axial diffusion of an autocatalyst. These predictions are verified experimentally for a non-oscillatory autocatalytic reaction, viz., the oxidation of thiosulfate with chlorite, carried out in a packed bed of glass beads. It is demonstrated for the first time that, in the case of an adverse flow, the stationary wavefronts in the "wide gap" limit are indeed observed for this reaction, and this limit can be achieved by, e.g., increasing the concentrations of the key reactants. We suggest that the observations of stationary wavefronts in the oscillatory Belousov-Zhabotinsky reaction reported earlier can be accounted for in similar terms. The formation of stationary wavefronts in a packed bed is favored owing to the much larger flow dispersion effects (the ratio of the largest flow velocity to the average flow velocity) in a porous medium as compared to flow in a gap or a pipe. Nevertheless, for a correct description of the effects of advection on the wavefront propagation, it is not appropriate to substitute the dispersion coefficient for diffusivity in the reaction-diffusion-advection equation.

The Journal of Physical Chemistry A, 2007

Magnetic resonance imaging was used for two-dimensional temperature visualization of chemical wav... more Magnetic resonance imaging was used for two-dimensional temperature visualization of chemical waves propagation in the autocatalytic exothermal reaction of thiosulfate oxidation by chlorite. The technique presented is based on the temperature dependence of the water chemical shift. Temperature maps were acquired by employing the TurboFLASH imaging method. The results obtained allow one to judge about directions of buoyancy flows. Two types of convection critical modes in a vertical tube during the wave propagation were detected.

Lab on a Chip, 2013

The heterogeneous hydrogenation reaction of propene into propane in microreactors is studied by r... more The heterogeneous hydrogenation reaction of propene into propane in microreactors is studied by remote detection (RD) nuclear magnetic resonance (NMR). The reactors consist of 36 parallel microchannels (50 × 50 μm(2) cross sections) coated with a platinum catalyst. We show that RD NMR is capable of monitoring reactions with sub-millimeter spatial resolution over a field-of-view of 30 × 8 mm(2) with a steady-state time-of-flight time resolution in the tens of milliseconds range. The method enables the visualization of active zones in the reactors, and time-of-flight is used to image the flow velocity variations inside the reactor. The overall reaction yields determined by NMR varied from 10% to 50%, depending on the flow rate, temperature and length of the reaction channels. The reaction yield was highest for the channels with the lowest flow velocity. Propane T1 relaxation time in the channels, estimated by means of RD NMR images, was 270 ± 18 ms. No parahydrogen-induced polarization (PHIP) was observed in experiments carried out using parahydrogen-enriched H2, indicating fast spreading of the hydrogen atoms on the sputtered Pt surface. In spite of the low concentration of gases, RD NMR made imaging of gas phase hydrogenation of propene in microreactors feasible, and it is a highly versatile method for characterizing on-chip chemical reactions.

Journal of the American Chemical Society, 2014

To date, only metal-containing hydrogenation catalysts have been utilized for producing substanti... more To date, only metal-containing hydrogenation catalysts have been utilized for producing substantial NMR signal enhancements by means of parahydrogen-induced polarization (PHIP). Herein, we show that metal-free compounds known as molecular tweezers are useful in this respect. It is shown that ansa-aminoborane tweezers QCAT provided (20-30)-fold signal enhancements of parahydrogen-originating hydrogens in (1)H NMR spectra. Nuclear polarization transfer from the polarized hydrogens to (11)B nuclei leads to a 10-fold enhancement in the (11)B NMR spectrum. Moreover, our results indicate that dihydrogen activation by QCAT and CAT tweezers is carried out in a pairwise manner, and PHIP can be used for understanding the activation mechanism in metal-free catalytic systems in general.

Applied Magnetic Resonance, 2013

Immobilized iridium complexes synthesized using [Ir(COD)Cl] 2 by anchoring on hydrous and anhydro... more Immobilized iridium complexes synthesized using [Ir(COD)Cl] 2 by anchoring on hydrous and anhydrous silica gels were studied in terms of generating parahydrogen-induced polarization (PHIP) in the gas-phase hydrogenation of propylene and propyne. Distinguishing differences in the hydrogenations of carboncarbon double and triple bonds were found. It has been shown that in the double bond hydrogenation both catalysts are very active even at 25°C. The reaction yield in continuous flow experiments is more than 70 %, whereas the obtained PHIP degrees are very low. In the case of the triple bond hydrogenation, a more or less active hydrogenation reaction was observed at relatively high temperatures (&70-80°C) for the catalyst immobilized on anhydrous silica, while the catalyst immobilized on hydrous silica was inactive at these temperatures. Contrary to the double bond hydrogenation, the triple bond hydrogenation provided significant signal enhancements observed in 1 H nuclear magnetic resonance spectra for the signals corresponding to protons of vinyl fragments of product propylene in both PASADENA and ALTADENA experiments. The catalyst, however, is not stable under the triple bond hydrogenation reaction conditions, and deactivates within several minutes. It was also found that at higher temperatures (100-120°C), this

Angewandte Chemie International Edition, 2012

This work was supported by the Russian Government (grant 11.G34.31.0045), RFBR (11-03-93995-CSIC_... more This work was supported by the Russian Government (grant 11.G34.31.0045), RFBR (11-03-93995-CSIC_a, 11-03-00248-a, 12-03-00403-a), the program of support of leading scientific schools (NSh-7643.2010.3), and the Academy of Finland (123847 and 139839). We thank Dr. J. Lounila for fruitful discussions. I.V.K. thanks Prof. C. Bianchini and Dr. P. Barbaro (ICCOM-CNR, Sesto Fiorentino, Firenze, Italy) for providing the sample of catalyst [Rh(cod)(sulfos)]/ SiO 2. V.V.Z. thanks I. E. Beck for providing the sample of catalyst Rh/ TiO 2 .

Angewandte Chemie International Edition, 2010

, SB RAS (67, 88), the program of support of leading scientific schools (NSh-7643.2010.3) and FAS... more , SB RAS (67, 88), the program of support of leading scientific schools (NSh-7643.2010.3) and FASI (state contract 02.740.11.0262). I.V.K. thanks Prof. C. Bianchini and Dr. P. Barbaro (ICCOM-CNR, Sesto Fiorentino, Firenze, Italy) for providing the sample of catalyst [Rh(cod)(sulfos)]/SiO 2 .

Angewandte Chemie International Edition, 2008

Journal of the American Chemical Society, 1996

Two modifications of a conventional inversion-recovery experiment which exclude the effect of spe... more Two modifications of a conventional inversion-recovery experiment which exclude the effect of spectral diffusion on the measured spin-lattice relaxation times of rapidly tumbling nitroxide spin labels are described. In the first approach an almost uniform inversion is achieved by means of specially designed pulse trains with excitation patterns which match the three-line nitroxide ESR spectrum. In the second approach we essentially combine an inversion-recovery for the M I ) 0 line with an analog of a pulsed ELDOR technique for M I ) (1 lines in a single experiment. This allows us to reconstruct the recovery of the total magnetization of the ensemble of radicals which is not affected by spectral diffusion. The spin-lattice relaxation times of several nitroxide spin labels in different homogeneous and microheterogeneous environments are measured and compared. The temperature dependence of T 1 times is compared for two solvents, methylcyclohexane and carbon disulfide, which differ in nuclear spin concentration by almost a factor of 1000. The reported experimental evidence suggests that interactions with the nuclear spins of a solvent do not significantly contribute to the spin-lattice relaxation of nitroxide spin labels.

Russian Journal of Applied Chemistry, 2011

Methodological foundations of a physical analysis of the structure of a crystallized binary syste... more Methodological foundations of a physical analysis of the structure of a crystallized binary system constituted by 5,6-(3′,4′-furazano)-1,2,3,4-tetrazine-1,3-dioxide and 2,4-dinitro-2,4-diazapentane by optical microscopy, NMR tomography, and X-ray diffraction analysis were developed. First results were obtained, which characterize specific features of the crystallization process and parameters of crystals being formed in a eutectic mixture and molecular compound.

NATO Science Series II: Mathematics Physics and Chemistry, 2006

ABSTRACT Development and study of novel nanoporous adsorbents is a very challenging goal of curre... more ABSTRACT Development and study of novel nanoporous adsorbents is a very challenging goal of current material science research. Among these materials are new alumosilicates, alumo- and iron phosphates, MCMs, SBAs, MOFs, carbon sieves, etc., with the pore size of few nanometers. Less progress is made in developing new adsorbents with relatively large pores of 7-20 nm.

Journal of Engineering Physics and Thermophysics, 1999

We present results on acoustic drying of wood (pine). By use of a tomograph, we obtained the dist... more We present results on acoustic drying of wood (pine). By use of a tomograph, we obtained the distribution of moisture in the cross section of a specimen before and after acoustic action exerted on it. It is found that in the direction of the normal to the annual rings this action is not monotonic, but rather it varies periodically. Affected

NATO Science Series II: Mathematics Physics and Chemistry, 2006

Modern magnetic resonance is an extremely broad field of scientific research, which embraces a va... more Modern magnetic resonance is an extremely broad field of scientific research, which embraces a vast variety of experiments and techniques. To better define the place of NMR imaging in magnetic resonance, it might be advantageous to consider the majority of the magnetic resonance (MR) experiments as being performed in a multidimensional space of frequencies, spatial coordinates and time. Each particular