Ing. Mgr. Ondřej Kaman, Ph.D.
Our laboratory has been traditionally focused on complex studies of magnetic nanomaterials, including their synthesis and comprehensive characterization, analysis of their fundamental properties, structural peculiarities and magnetic behavior, and evaluation of their performance in selected applications. However, we have been shifting our attention in recent years, to a large extent, to magnetically interesting molecular systems based on coordination compounds of d and f metals. Both coordination compounds and magnetic nanomaterials are now equally important for us.
Magnetic nanoparticles and other nanostructures: We develop new synthesis methods for nanomaterials and improve existing procedures, including synthesis of magnetic nanoparticles, their coating, decoration and surface functionalization. We pay close attention to thorough structural, morphological and magnetic characterizations and tailor the prepared nanomaterials to applications in medicine, sensing and inkjet-printed electronics with a particular emphasis on their use as contrast agents for magnetic resonance imaging (MRI), tracers for magnetic particle imaging (MPI) and hyperthermia agents for cancer therapy. Other applications of our recent interest include the application of complex magnetic particles with plasmonic structures for sensing.
Molecular systems: We explore the magnetic properties of molecular complexes at the fundamental level, taking advantage of the immense structural and chemical variety impacting coordination environment of magnetic ions.
Low-dimensional magnetism: We extend the studies of nanomaterials and molecular systems towards magnetic properties of compounds with reduced-dimensional magnetic motifs, such as magnetic chains, layers, and clusters, to understand the impact of dimensionality on magnetic behavior.
Additionally, we have recently expanded our portfolio to include the following topics:
Magneto-electric nanomaterials: We develop magneto-electric core-shell heterostructures, which exhibit coupled magnetic and electric order, and explore potential applications of these new multifunctional materials.
Frustrated magnetism: We target frustrated magnetic systems, where competing magnetic interactions lead to complex and often exotic magnetic ground states. In addition to their fundamental significance, these systems present unique opportunities, such as magnetic cooling down to the millikelvin range.
Our laboratory, in close collaboration with other laboratories of the Department of Magnetics and Superconductors as well as other research groups at FZU, employs state-of-the-art techniques for the synthesis, characterization, and investigation of magnetic materials. Our synthesis methods for nanomaterials encompass a range of techniques, including hydrothermal and solvothermal procedures, molten salt syntheses, thermal decomposition of organic metal complexes, sol-gel routes, etc. A glovebox and a Schlenk line allow us to work under oxygen- and moisture-free conditions and synthesize and study highly air-sensitive molecular compounds. We routinely employ SQUID and VSM magnetometry, powder X-ray diffraction and neutron diffraction, UV-Vis and FT-IR spectroscopy, Mössbauer spectroscopy and DFT calculations, as well as TEM (transmission electron microscopy), DLS (dynamic light scattering) and ELS (electrophoretic light scattering). By combining experimental and theoretical approaches, we aim to gain a deeper understanding of the fundamental properties of magnetic materials across length scales and, eventually, to develop innovative materials for future technologies.
Thermal decomposition of organic metal complexes represents one of our routinely employed methods of nanoparticle synthesis. TEM micrographs of Co-Zn ferrite nanoparticles prepared by thermal decomposition are shown on the right.
Sensing of fluorine ions by a urea-based sensor was first demonstrated by a dramatic change of Raman spectra in solution (left; from red spectra with no F- to purple ones with excess of F-) and then by changes in surface-enhanced Raman spectra collected from the molecules of the sensor attached to the surface of gold nanoshells (middle; the graph shows intensity change of selected peaks dependent on concentration of F-). TEM micrograph of gold nanoshells – magnetic nanoparticles coated subsequently with silica and gold – is shown on the right. For more details see Bui et al.
In the dinuclear organometallic complex [Cp‴Cr(μ-H)]2, where Cp‴ = tri(tert-butyl)-cyclopentadienide, CrII ions interact through hydride bridges and a direct metal-metal bond, which results in a very strong antiferromagnetic coupling of J12 = −206(1) cm–1. The fit of temperature-dependent product of DC magnetic susceptibility and temperature, decomposed into components of the complex (AFM), paramagnetic impurity (PAR) and temperature-independent paramagnetism (TIP) is shown on the right, the measured susceptibility is shown in the inset. The magnetic study was performed in collaboration with Prof. Dr. Helmut Sitzmann (University of Kaiserslautern-Landau), for more details see Smytschkow et al.
Contact person: Ondřej Kaman