Klaus-Peter DinseFreie Universität Berlin | FUB · Department of Physics
Klaus-Peter Dinse
Prof. Dr.
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247
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Introduction
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April 1992 - March 2008
March 1984 - March 1992
January 1982 - December 1983
Publications
Publications (247)
Electron paramagnetic resonance–on-a-chip (EPRoC) devices use small voltage-controlled oscillators (VCOs) for both the excitation and detection of the EPR signal, allowing access to unique sample environments by lifting the restrictions imposed by resonator-based EPR techniques. EPRoC devices have been successfully used at multiple frequencies (7 t...
The Vanadium redox flow battery (VRFB) is considered a promising candidate for large-scale energy storage in the transition from fossil fuels to renewable energy sources. VRFBs store energy by electrochemical...
In this study, first-row transition metal-doped calcium oxide materials (Mn, Ni, Cr, Co., and Zn) were synthesized, characterized, and tested for the OCM reaction. Doped carbonate precursors were prepared by a co-precipitation method. The synthesis parameters were optimized to yield materials with a pure calcite phase, which was verified by XRD. EP...
Electron paramagnetic resonance (EPR) spectroscopy is the method of choice to investigate and quantify paramagnetic species in many scientific fields, including materials science and the life sciences. Common EPR spectrometers use electromagnets and microwave (MW) resonators, limiting their application to dedicated lab environments. Here, novel asp...
Electron paramagnetic resonance (EPR) spectroscopy is the method of choice to investigate and quantify paramagnetic species in many scientific fields, including materials science and the life sciences. Common EPR spectrometers use electromagnets and microwave (MW) resonators, limiting their application to dedicated lab environments. Here, we presen...
Using pulsed electron paramagnetic resonance (EPR) techniques, the low-temperature magnetic properties of the NO radical being confined in two different modified open C60-derived cages are determined. It is found that the smallest principal g value g3, being assigned to the axis of the radical, deviates strongly from the free electron value. This b...
Abstract. Using pulsed EPR techniques, the low temperature magnetic properties of the NO radical being confined in a C60 derived cage are determined. It is found that the smallest principal g value g <sub>3</sub>, being assigned to the axis of the radical, deviates strongly from the free electron value. This behavior results from partial compensati...
The magnetic properties of Mn-Na2WO4/SiO2, a promising catalyst for the oxidative coupling of methane (OCM), were investigated in two states: reduced with CH4 until reactivity ceased and re-oxidized with O2 to probe for state-specific magnetic species and their involvement in the oxygen storage of the catalyst. Employing temperature and frequency d...
A series of Na2WO4/Mn/SiO2 catalysts supported on mesoporous silica were prepared and tested for the oxidative coupling of methane in chemical looping experiments. The parameter variations were done for specific surface area, Mn-loading and support material. Chemical looping experiments reveal that highest catalytic activity is observed at 2 wt% Mn...
Our recent studies revealed that the role of Li in Li/MgO as a catalyst for oxidative coupling of methane (OCM) is to promote MgO surface morphology change rather than serve as a constituent of catalytically active sites. Indeed, while Li/MgO is unstable at realistic conditions with respect to the loss of Li, the resulting samples show enhanced sel...
The time-window for processing electron spin information (spintronics) in solid-state quantum electronic devices is determined by the spin-lattice and spin-spin relaxation times of electrons. Minimizing the effects of spin-orbit coupling and the local magnetic contributions of neighbouring atoms on spin-lattice and spin-spin relaxation times at roo...
Supplementary Figures 1-12, Supplementary Table 1, Supplementary Notes 1-4 and Supplementary References
The effective spin of paramagnetic centers generated during the reaction of a mixture of CH4 and O2 on activated MgO was determined with Transient-Nutation EPR (TN-EPR). For the first time it could be shown that apart from the generation of surface-trapped superoxide radicals O2-, a significant amount of paramagnetic centers are formed with an effe...
In the course of an investigation of electrolytically generated radical ions in the nematic mesophase of liquid crystals, we studied the influence of supporting electrolyte on the degree of molecular ordering. In the case of the radical anion of tetracyanoethylene (TCNE-) electrolytic generation results in a lower degree of ordering than chemical g...
The proton ENDOR spectra of various phenyl substituted hydrocarbon radicals in solution show a marked temperature dependence of the positions, widths, and amplitudes of particular lines. These effects are analyzed in terms of three relaxation mechanisms: (i) internal hindered rotation and (ii) torsional oscillations of the phenyl rings, and (iii) m...
Electrolytically generated semiquinone radical ions have been studied in the nematic mesophase of p-azoxyanisole by EPR methods. The degree of molecular ordering of benzo-, naphtho-, and anthrasemiquinones varied from 0.085, 0.18 to 0.20, respectively. The observed shifts of the hfs splitting constants and the g factors are in reasonable agreement...
The electronic structure of endohedral Sc@C82 with a C82 cage of C2v symmetry has been studied by ab initio Hartree-Fock (HF) calculations. The optimized position of Sc in the configuration of minimum energy is predicted to be on the two-fold axis of the fullerene cage. In the corresponding configuration Sc is above the center of a hexagon of site...
From the triatomic molecule SO2 with 18 valency electrons we generated the mononegative radical ion with the aid of electrolytic techniques. In this way we could vary the radical concentration over a wide range and could also study the influence of counter ions and solvent molecules. The semiempirical LCAO-MO theory of Walsh was used to calculate t...
The electronic triplet state sublevels of aromatic molecules generally have different energies already at zero external magnetic field. This zero field splitting usually is too small to be resolved by a high resolution optical spectrometer, and only a high magnetic field (typically 30 kG) yields enough Zeeman-splitting to allow full resolution. Fro...
Using pulsed EPR and ENDOR, the full set of g matrix and vanadium hyperfine parameters of the persistent paramagnetic V4+ center in "as prepared" and H-2 reduced SBA-15 supported VOx catalysts has been measured. The determination of relative signs of the vanadium hyperfine tensor elements by ENDOR using orientation selection allowed an unambiguous...
Paramagnetic centers generated by swift heavy ion irradiation of LiF crystals could be identified as electrons trapped at regular anion vacancy sites (F centers). Well-resolved electron-nuclear double resonance (ENDOR) spectra resulting from the hyperfine interaction with 7Li and 19F nuclei located in six different shells could be recorded. In orde...
VOx (1.41.7 V?nm-2) supported on SBA-15, Al2O3, or TiO2 was studied before and after exposure to oxidative dehydrogenation of propane (ODP), and pure hydrogen or propane. After treatment, samples were quenched and frozen in quartz vials and characterized by using high-frequency electron paramagnetic resonance (HF-EPR). For SBA-15- and Al2O3-support...
IntroductionBasic PrinciplesExperimental Methods
Case StudiesConclusions and PerspectivesSupplementary MaterialReferences
Co-doping of Li/MgO, a well-known catalyst for the oxidative coupling of methane, was investigated. It is demonstrated that Gd3+ and Fe3+ can be used as spin sensors in these solids to investigate the structure via EPR spectroscopy. These aliovalent ions occupy Mg2+ sites in the lattice; the expected coupling with charge-compensating neighboring Li...
Defect rich MgO nanocrystals arranged in a hierarchic three-dimensional pore network were synthesized by using gel combustion synthesis (GCS). By adding Li to the combustion precursor, Li-induced changes in the morphology and defect structure of MgO could be studied systematically. At low Li loadings (up to 1 wt?parts per thousand), the three-dimen...
Li-doped MgO is a potential catalyst for the oxidative coupling of methane, whereby surface Li+ O- centers are suggested to be the chemically active species. To elucidate the role of Li in the MgO matrix, two model systems are prepared and their morphological, optical and magnetic properties as a function of Li doping are investigated. The first is...
Spatially resolved (19)F and (7)Li spin-lattice relaxation rates are measured for LiF single crystals after irradiation with two kinds of swift heavy ions ((12)C of 133 MeV and (208)Pb of 1.78 GeV incident energy). Like in earlier studies on (130)Xe and (238)U irradiated LiF crystals, we found a strong enhancement of the nuclear spin-lattice relaxa...
We present an electron paramagnetic resonance (EPR) study of ErSc2N@C80 fullerene in which there are two Er3+ sites corresponding to two different configurations of the ErSc2N cluster inside the C80 cage. For each configuration, the EPR spectrum is characterized by a strong anisotropy of the g factors (gx,y = 2.9, gz = 13.0 and gx,y = 5.3, gz = 10....
We herein report the investigation of N@C(60) exposed to laser flash excitation to exhibit the acceleration of the decay of (N@C(60))* by the encased N atom.
Sealed, deoxygenated single-wall carbon nanotubes show two characteristic electron paramagnetic resonance (EPR) signals at
g=2.07 and g=2.00 in the temperature range from 300 to 50K. Reversible interconversion between both components was observed. The large g-shift and the temperature dependence of the EPR susceptibility of the g=2.07 signal indica...
Using a resonator-free setup, pulsed high-frequency (240GHz) electron paramagnetic resonance (EPR) experiments on gadolinium-doped
PbTiO3 and PbZrO3 samples have been performed. It could be demonstrated that echo-detected EPR spectra can be recorded routinely from these
materials. These compounds are highly absorptive at microwave frequencies, thus...
Spatially resolved 19F
and 7Li
nuclear magnetic resonance (NMR) spin–lattice relaxation rates have been
measured in LiF crystals irradiated with 1.44 GeV Xe ions at fluences from
1010 to
1012 ions cm−2. In addition, the F-centre concentration has been measured by optical absorption
spectroscopy and the concentration of paramagnetic centres by ele...
Supported vanadium oxide catalysts were studied by high-frequency EPR for determination of the paramagnetic vanadium oxidation states vanadium(IV) and vanadium(III). TiO 2 -, γ-Al 2 O 3 -, and SiO 2 (SBA-15)-supported catalysts were investigated before and after being used for the oxidative dehydrogenation of propane. While the SBA-15-supported cat...
The 22nd Winterschool on Electronic Properties of Novel Materials (IWEPNM 2008) took place from 1 March to 8 March 2008. It continued the tradition of winterschools of this type in Kirchberg/Tirol in its well-known atmosphere of collegiality and emphasis on scientific exchange between young and experienced scientists.
The sessions at the IWEPNM 200...
In addition to g = 2.00 signals seen frequently in EPR spectra of SWNT, signals at g = 2.07 of SWNT prepared by CVD were detected, exhibiting a Pauli susceptibility temperature dependence. This Pauli magnetism in combination with the large g shift is taken as evidence that these signals originate from itinerant electrons of metallic nanotubes. At t...
Microwave absorption (MA) is applied to study the electromagnetic properties of bulk samples of single-walled carbon nanotubes (SWNT). Using resonant MA (electron paramagnetic resonance) and also its non-resonant variant (cavity perturbation) it was possible to reveal different electronic phases of SWNT. Besides the existence of doped semiconductin...
Single Wall Carbon Nanotubes (SWCNT) prepared by the "super growth" method and arc-grown material were used as templates for peapod preparation with La@C(82). A qualitative change of the electron paramagnetic resonance (EPR) properties of La@C(82) is observed after incorporation into SWNT. The loss of lanthanum hyperfine interaction in combination...
Single-wall carbon nanotubes (SWNT) prepared by the "super growth" method developed recently exhibit electron paramagnetic resonance (EPR) signals, which can be attributed to itinerant spins. EPR results indicate very low defect and catalyst concentrations in this superior material. Under these conditions EPR can be used to study details of charge...
The 21st Winterschool on Electronic Properties of Novel Materials (IWEPNM 2007) took place from 10 March to 17 March 2007. It continued the tradition of winterschools of this type in Kirchberg/Tirol in its well‐known atmosphere of collegiality and emphasis on scientific exchange between young and experienced scientists.
The sessions at the IWEPNM 2...
Single wall carbon nanotubes (SWNT) prepared by the “super growth” method exhibit electron paramagnetic resonance (EPR) signals, which originate from temperature activated detrapping of spins. Non-resonant microwave absorption in the temperature range below 20 K is indicative for the opening of a small gap at the Fermi level for tubes of metallic c...
The 19th Winterschool focused mainly on new nanostructured materials,
with data presented on functionalized fullerenes and carbon nanotubes,
filled and double-wall nanotubes, non-carbon nanotubes, such as BN and
MoS2 tubes, and other nanostructures. The direction of nanoelectronics
research was explored in depth, and advancements in composite techn...
Electron Paramagnetic Resonance (EPR) Volume 17 highlights major developments in this area reported up to the end of 1999, with results being set into the context of earlier work and presented as a set of critical yet coherent overviews. The topics covered describe contrasting types of application, ranging from biological areas such as EPR and ENDO...
Using multi frequency electron paramagnetic resonance (EPR) it was possible to determine the inherent fine structure (FS) interaction of nitrogen encapsulated in a C70 cage. Confinement of N@C70 in single wall carbon nanotubes (SWNT) of rather wide diameter does not significantly influence this value. The transition between isotropic molecular tumb...
The electromagnetic properties of a bulk sample of high quality single-wall carbon nanotubes with a mean diameter of 2.5 nm were investigated by noninvasive methods. The observed sudden increase in the microwave absorptivity below 12 K is taken as indicative of the formation of a superconducting phase of a small part of the sample. The increase in...
The electromagnetic properties of a bulk sample of high quality single-wall carbon nanotubes with a mean diameter of 2.5 nm were investigated by noninvasive methods. The observed sudden increase in the microwave absorptivity below 12 K is taken as indicative of the formation of a superconducting phase of a small part of the sample. The increase in...
Using multi frequency electron paramagnetic resonance (EPR) it was possible to determine the inherent fine structure (FS) interaction of nitrogen encapsulated in a C 70 cage. Confinement of N@C 70 in single wall carbon nanotubes (SWNT) of rather wide diameter does not significantly influence this value. The transition between isotropic molecular tu...
The 20th International Winterschool on Electronic Properties of Novel Materials (20th IWEPNM) was held in Kirchberg/Tirol on Molecular Nanostructures and extended from 4 to 11 March 2006. The first Winterschool of this type took place in March 1985. Except for the first two, all Winterschools were arranged in the lecture rooms of the Hotel Sonnalp...
Single Wall Carbon Nanotubes (SWNT) produced by “Super-Growth” CVD technique show no evidence for non-carbon impurities. At X-Band frequencies an EPR signal from conduction electrons is observed at room temperature. At low temperatures the conduction electrons get trapped, leading to a sharp EPR signal with long-lived spin states. Using multi pulse...
Multifrequency electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR) techniques were used to obtain structural information about the copper(II)-chelidamate complex. Well-resolved nitrogen ENDOR spectra could be recorded from solid solution samples by using selective excitation of spin packets. Evaluation of nuclear qua...
Immediately after the observation that fullerenes can act as cages for persistent trapping of ions or atoms, Electron Paramagnetic Resonance (EPR) was used for the investigation of these compounds. In contrast to group 15 atoms entrapped in C60 or C70, which are nearly perfectly decoupled from the cage and which at time average are found at the cen...
The double-bridged hemicarcerand [A,B-(CH2OH)2-cavitand]-(CH2NHCH2)2-[A,B-(CH2OH)2-cavitand] 23 (and several other related compounds) was synthesized by the condensation of the two complementary precursors A,B-(CH2NH2)2(CH2OH)2-cavitand and A,B-(CH2Br)2(CH2OAc)2-cavitand followed by hydrolysis of the acetate groups. This hemicarcerand has nitrogen...
A semiquantitative treatment of hyperfine sublevel correlation spectra of a S=1/2, I=1 spin system is presented. The derived closed analytical expressions allow the determination of components of the dipolar
and quadrupolar coupling tensors. The method is applicable if nonsecular terms can be neglected and if canonical orientations of the hyperfine...
A trans-2-linked molecular diad displays both σ-donor and π-acceptor interations (see picture). The crystal structure reveals linear stacking arrangements in which the fullerene moiety is located directly above the porphyrin moiety of the neighboring molecule.
By utilizing multifrequency electron paramagnetic resonance (EPR) spectroscopy, the iron functional center in Fe3+-modified polycrystalline lead zirconate (PbZrO3) was studied. The single phase polycrystalline sample remained orthorhombic and antiferroelectric down to 20 K as confirmed by high-resolution synchrotron powder diffraction. The Fe3+ ion...
Zwischen der C60- und der Cobalt(ii)-tetraphenylporphyrin-Einheit einer trans-2-verbrückten molekularen Diade treten sowohl σ-Donor- als auch π-Acceptor-Wechselwirkungen auf (siehe Bild). Im Kristall bildet die Diade Stapelanordnungen, indem sich der Fullerenteil eines Moleküls direkt über den Porphyrinteil des benachbarten Moleküls lagert.
Copper(II)- and iron(III)-modified Pb[ZrxTi1−x]O3 ferroelectrics were investigated by means of high-field/high-frequency EPR. The results obtained suggest that Cu2+ and Fe3+ both substitute as acceptor centers for [Zr,Ti]4+. Whereas for the iron-doped system the charge compensating oxygen vacancies (V) lead to the formation of charged (Fe′V)· defec...
A comparative study of C60-based endohedral fullerenes was performed. From an analysis of spin relaxation times of the recently characterized Cu@C60 metallo-endofullerene, it could be shown that the encased ion occupies a well-defined off-centre position even at room temperature. Localization on the timescale of an EPR experiment is combined with c...
Copper(II)-doped Pb[Zr0.54Ti0.46]O3 (PZT) ferroelectrics with a dopant concentration of 0.25mol% were investigated at high magnetic fields, enabling an enhanced resolution of the structural distortion at the dopant site. The results obtained suggest that Cu2+ substitutes as an acceptor centre for [Zr,Ti]4+ in oxygen octahedra with tetragonal, monoc...
Copper(II)- and iron(III)-modified Pb[ZrxTi1−x]O3 ferroelectrics were investigated by means of high-
field/high-frequency EPR. The results obtained suggest that Cu2+ and Fe3+ both substitute as acceptor
centers for [Zr,Ti]4+. Whereas for the iron-doped system the charge compensating oxygen vacancies (V··
lead to the formation of charged (Fe V··
Ti...
It is demonstrated that metallo‐endofullerenes can exhibit close‐lying electronic levels with different spin multiplicity, thus serving as sensitive spin probes for charge transfer in carbon nanotubes. In contrast, N@C60 is an inert spin label with exceptional sensitivity against local electric fields, which can probably be used to explore SWNT pro...