Rene Pfeifer

Czech Academy of Sciences, Institute of Physics

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Alexander Kromka

Czech Academy of Sciences, Institute of Physics

Vlastimil Vyskočil

Charles University

Jiřı́ Barek

Charles University

Ondrej Szabó

Czech Academy of Sciences, Institute of Physics

ŠS

Štěpán Stehlík

Czech Academy of Sciences, Institute of Physics

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Štěpán Potocký

Czech Academy of Sciences, Institute of Physics

Célia Regina Sousa da Silva

Universidade Federal do Rio de Janeiro

Michal Augustín

Charles University

Uwe Hartmann

Saarland University

Josino Costa Moreira

Fundação Oswaldo Cruz

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Czech Academy of Sciences

Czech Academy of Sciences, Institute of Physics

Czech Technical University in Prague

Charles University

Universidade Federal do Rio de Janeiro

Universidade do Estado do Rio de Janeiro

Saarland University

Slovak University of Technology in Bratislava

Centre National de la Recherche Scientifique

Technical University of Munich

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Reply to comments by S. A. Ryce

Rene Pfeifer

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DNA-modified silver amalgam sensor for electrochemical determination of 1-nitropyrene

Jenna T Swenson Vlastimil Vyskočil Rene Pfeifer

Amalgam (chemistry)

10.1021/scimeetings.0c02208

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Assessment of the Factors Influencing the Recording Performance of Circumneural Electrodes

2022 44th Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC) (2023)

Vera Oppelt Friedhelm Pfeiffer Rene Pfeifer Martin Schüettler Thomas Stieglitz

The quality of recorded peripheral nerve signals is decisive for their application in therapies. The electroneurogram can be recorded via implantable circumeural electrodes that are wrapped around the peripheral nerve. The shape and amplitude of the signal recorded by the electrode are influenced by the design and contact configuration of the electrode. In this paper, the impact of the number of contacts, contact size and electrical insulation to the outside is investigated to predict the single fiber action potential based on the measured impedance data.

SIGNAL (programming language)

Focused Impedance Measurement

10.1109/embc40787.2023.10341201

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Enhanced Electrochemical Performance of Polyaniline‐Boron Doped Diamond Electrode for Supercapacitor Applications

Small Methods (2025)

Elena Tomšík Stephen Boahene Kateřina Dragounová Rene Pfeifer Dhananjay K. Sharma

Abstract Understanding how to tune the properties of electroactive materials is a key parameter for their applications in energy storage systems. This work presents a comprehensive study in tailoring polyaniline (PANI) suspensions by acid‐assisted polymerization method and their subsequent deposition on boron‐doped diamond (BDD) supports with low/high B concentrations. The porous or densely packed morphology of PANI is successfully controlled by varying the monomer‐to‐initiator ratio. The interaction between PANI and BDDs leads to the shift in oxidation and reduction potentials, and the high B doping resulted in the reduction of the oxidation potentials. Notably, the highest specific capacitance of 958 F g −1 , which represents 90% of the theoretical capacitance, is recorded for the support with relatively low B content. Moreover, PANI obtained by slow kinetic has a stronger interaction with the B‐doped diamond support, which is confirmed by electrochemical impedance spectroscopy. This study provides valuable insights for optimizing PANI suspension preparation methods and selecting appropriate boron doping concentrations in nanodiamond supports for composite electrodes in energy storage applications.

Nanodiamond

10.1002/smtd.202401523

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HF-MFM imaging of stray fields from perpendicular write heads

Journal of Physics Conference Series (2010)

M.R. Koblischka Rene Pfeifer A. Cazacu Robert Lamberton Uwe Hartmann

The high-frequency magnetic force microscopy (HF-MFM) technique has been employed for the measurement of stray fields emanating from traditional longitudinal write heads. Here, we show that it is also possible to apply the HF-MFM technique to perpendicular write heads. The situation is different in so far, that there is no magnetic flux between two poles. In contrast, there is only one pole and the flux closure is obtained in combination with the writing medium. An ac current of 50 mA with a carrier frequency ranging between 200 MHz and 2 GHz fed in into the write head causes an observable contrast in the HF-MFM image. Not only the write pole itself but also the magnetic shielding around the pole are strongly influenced by the HF-current.

Ranging

Perpendicular recording

10.1088/1742-6596/200/11/112004

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Size Effects on Surface Chemistry and Raman Spectra of Sub-5 nm Oxidized High-Pressure High-Temperature and Detonation Nanodiamonds

The Journal of Physical Chemistry C (2021)

Štěpán Stehlík Michel Mermoux Bernhard Schummer Ondřej Vaněk Kateřina Kolářová

Understanding materials with dimensions down to a few nanometers is of major importance for fundamental science as well as prospective applications. Structural transformation and phonon-confinement effects in the nanodiamonds (NDs) have been theoretically predicted below 3 nm in size. Here, we investigate the effect of size on the surface chemistry, microscopic structure, and Raman scattering of high-pressure high-temperature (HPHT) and detonation nanodiamonds (DNDs) down to 2–3 nm. The surface and size of NDs are controlled by annealing in air and ultracentrifugation resulting in three ND fractions. Particle size distribution (PSD) of the fractions is analyzed by combining dynamic light scattering, analytical ultracentrifugation, small-angle X-ray scattering, X-ray diffraction, and transmission electron microscopy as complementary techniques. Based on the obtained PSD, we identify size-dependent and synthesis-dependent differences of ND properties. In particular, interpretation of Raman scattering on NDs is revisited. Comprehensive comparison of detonation and pure monocrystalline HPHT NDs reveals effects of diamond core size and defects, chemical and temperature (in)stability, and limitations of current phonon confinement models. In addition, low-frequency Raman scattering in the 20–200 cm–1 range is experimentally observed. The size dependence of this signal for both HPHT NDs and DNDs suggests that it may correspond to confined acoustic vibrational, "breathing-like" modes of NDs.

Nanometre

10.1021/acs.jpcc.0c09190

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Citations (37)

Activation Energies of the Proton‐exchange Reactions in Water Measured with the ¹H‐NMR Spin Echo Technique

Berichte der Bunsengesellschaft für physikalische Chemie (1990)

Rene Pfeifer H. G. Hertz

Abstract From the pH‐dependence of the transverse relaxation‐time T 2 of protons in 17 O‐enriched water we have determined the rate constants k 1 und k 2 of the two proton‐exchange processes (I) and (II) magnified image in the temperature range from +5°C to +60°C. – Modified Bloch equations including exchange between the different states of the proton‐septett are used to fit the experimental data yielding directly the rate constants k 1 and k 2 . Classical and quantum mechanical relations connecting the limiting ionic equivalent conductivities λ H+ and λ OH− with the rate constants k 1 and k 2 are discussed.

Limiting

10.1002/bbpc.199000030

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Citations (36)

DNA-modified silver amalgam sensor for electrochemical determination of 1-nitropyrene

Jenna T Swenson Vlastimil Vyskočil Rene Pfeifer

Amalgam (chemistry)

10.1021/scimeetings.0c02209

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High-Yield Production of SiV-Doped Nanodiamonds for Spectroscopy and Sensing Applications

ACS Applied Nano Materials (2024)

Alexander Kromka M. Varga Kateřina Dragounová Oleg Babčenko Rene Pfeifer

Nanodiamonds (NDs) containing optically active centers have gained significant relevance as the material of choice for biological, optoelectronic, and quantum applications. However, current production methods lag behind their real needs. This study introduces two CVD-based approaches for fabricating NDs with optically active silicon-vacancy (SiV) color centers: bottom-up (BU) and top-down (TD) methods. The BU approach generates nanoporous diamond films with a core-shell structure, while the TD method employs molten-salt thermal etching to create uniform porous structures from nanocrystalline diamond films. Comprehensive characterization using advanced techniques revealed distinct morphologies and optical properties for each approach. The BU method yielded higher-quality diamond phases with top-surface incorporation of SiV centers, while the TD method demonstrated efficient nondiamond phase removal. Ultrasonic disintegration of both porous films produced NDs ranging from 40 to 500 nm, with unique morphologies characteristic of each approach. Photoluminescence measurements confirmed SiV centers (738 nm) in all NDs, exhibiting sensitivity to surface terminations, particularly in BU samples. Temperature-resolved spectroscopy shows the potential of the fabricated NDs for nano thermometry over a wide range of temperatures up to 100 °C. The zero-phonon line shows 0.022 ± 0.003 nm/K sensitivity, while the line width exhibits 0.068 ± 0.004 nm/K broadening. The presented BU and TD methods offer significant advantages over existing techniques, including streamlined production processes, high-yield ND synthesis with tailored properties, and the potential for scalable, cost-effective manufacturing.

10.1021/acsanm.4c04676

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Citations (1)

Size Effects on Surface Chemistry and Raman Spectra of Sub-5 nm Oxidized High-Pressure High-Temperature and Detonation Nanodiamonds

The Journal of Physical Chemistry (2021)

Štěpán Stehlík Michel Mermoux Bernhard Schummer Ondřej Vaněk Kateřina Kolářová

Understanding materials with dimensions down to a few nanometers is of major importance for fundamental science as well as prospective applications. Structural transformation and phonon-confinement effects in the nanodiamonds (NDs) have been theoretically predicted below 3 nm in size. Here, we investigate the effect of size on the surface chemistry, microscopic structure, and Raman scattering of high-pressure high-temperature (HPHT) and detonation nanodiamonds (DNDs) down to 2–3 nm. The surface and size of NDs are controlled by annealing in air and ultracentrifugation resulting in three ND fractions. Particle size distribution (PSD) of the fractions is analyzed by combining dynamic light scattering, analytical ultracentrifugation, small-angle X-ray scattering, X-ray diffraction, and transmission electron microscopy as complementary techniques. Based on the obtained PSD, we identify size-dependent and synthesis-dependent differences of ND properties. In particular, interpretation of Raman scattering on NDs is revisited. Comprehensive comparison of detonation and pure monocrystalline HPHT NDs reveals effects of diamond core size and defects, chemical and temperature (in)stability, and limitations of current phonon confinement models. In addition, low-frequency Raman scattering in the 20–200 cm–¹ range is experimentally observed. The size dependence of this signal for both HPHT NDs and DNDs suggests that it may correspond to confined acoustic vibrational, “breathing-like” modes of NDs.

Nanometre

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