Andriy P. Budnyk

Copper-based nanoparticles prepared from copper(II) acetate bipyridine complex

The syntheses of CuO, Cu/Cu2O and Cu2O/CuO nanoparticles (NPs) from a single copper(II) acetate bipyridine complex by three different methods, microwave-assisted, solvothermal and borohydride, are reported. The presence of the bipyridine ligand in the copper complex would impose no necessity for additional stabilization during synthesis. The phases of formed NPs were ident- ified by X-ray diffraction. The CuO NPs obtained via solvothermal synthesis from alkaline solution at 160 °C were of ≈11 nm in size. Cu/Cu2O NPs of ≈80 nm were produced via a microwave-assisted polyol procedure at 185-200 °C, where ethylene glycol could play a triple role as a solvent, a reducing agent and a surfactant. Cu2O/CuO NPs of ≈16 nm were synthesized by a borohydride method at room temperature. The interplanar spacing calculated from selected- -area electron diffraction data confirmed the formation of Cu, CuO and Cu2O phases in the respective samples. All NPs were stable and could be used for various applications, including biomedicine.

Synthesis and structure modeling of ZnS based quantum dots

Quantum dots (QDs) based on zinc sulfide are synthesized by a microwave method in an aqueous medium using dioctyl sodium sulfosuccinate (DS) or 4,4′-bipyridine (BP). Based on the analysis of X-ray diffraction profiles the conclusion is drawn that QDs obtained have a structure of cubic zinc blende with an average particle size of 5.6 nm for the ZnSDS sample and 4.8 nm for ZnSBP. Transmission electron microscopy images show the presence of spherical aggregates of particles only for ZnSDS. FTIR data indicate the presence of sulfate ions in both samples; DS remains in the sample, facilitating the QD agglomeration, while BP is effectively washed out. From the optical diffuse reflectance spectra the band gap is estimated, which turns out to be larger than the expected one due to the presence of elemental sulfur in the samples and partial oxidation of the QD surface. The QD structure based on ZnS particles is also modeled in the work. The possibility to employ X-ray absorption near-edge spectroscopy for the verification of atomic structural parameters around zinc sites in QDs based on zinc sulfide is demonstrated.

Spectroscopic Methods in Catalysis and Their Application in Well-Defined Nanocatalysts

Abstract The first part of this chapter provides a simple, but general, description on the physical phenomena that are behind the interaction of probe beams (photons, electrons, or neutrons) with condensed matter. The differences in penetration depth, de Broglie wavelength, and requested sample environment for the three kinds of beams are stressed. The different photon-, electron-, and neutron-based techniques will be briefly listed and classified in terms of absorption, scattering, photoemission, and decay spectroscopies. The advantages and the drawbacks of each of those spectroscopies once applied to catalysts in working conditions will be emphasized. The second part provides selected examples when combination of different spectroscopies resulted in the determination of the structural, electronic, and vibrational features of well-defined nanocatalysts and in the understanding of their reactivity. The relevance of quantum mechanics-based theories in supporting the interpretation of spectroscopic results is stressed. The huge and growing impact that spectroscopies have in the field of catalysis is well testified by a bibliometric study showing that more than 150,000 papers have been published in 30 years reporting the use of at least one spectroscopic technique in the catalyst characterization, representing more than 5000 per year, that becomes more than 11,000 per year from 2010.

Platinum-free catalysts for low temperature fuel cells

In this work, we have successfully prepared Zn/Co-N/C and Zn/Co-Fe/N/C composites, both derived from single zeolitic imidazolate framework (ZIF) precursor Zn/Co-ZIF containing equivalent quantities of Zn and Co metal sites. The composites were formed by pyrolysis of the precursor at 700 °C in inert gas atmosphere as such and after mixing it with Fe(II) salt and 1,10-phenontraline in ethanol. Catalytic tests for oxygen reduction reaction (ORR) in electrochemical cell demonstrated promising results allowing us to consider these composites as potential Pt-free catalysts for low temperature fuel cells.

Theoretical and experimental study of mononuclear Cu(II) acetate-bipyridine complex

Cu(II) acetate-bipyridine complex has been synthesized. A series of experimental and theoretical spectroscopic studies was carried out for the freshly prepared sample. The local atomic and electronic structure was theoretically analyzed based on functional density theory and the structural models of the complex was obtained for various solvents. IR and XANES spectra were experimentally measured and modelled in the framework of functional density theory in a generalized gradient approximation to provide information on the chemical bond and local surroundings of copper. The powder X-ray pattern of the Cu(II) complex was obtained. The measured ESR spectra of the acetate-bipyridine complex at room temperature for the solid sample and solution in DMF confirms the formation of the mononuclear square planar complex.

Continuous Wave and Pulse EPR Characterization of Open-Shell Ti3+ Ions Generated in Hybrid SiO2–TiO2 Monoliths

Open-shell Ti3+ ions are generated within hybrid SiO2–TiO2 mesoporous monoliths by reaction with triethylaluminium vapors. Continuous wave and 2D pulse electron paramagnetic resonance techniques are used to investigate the local coordination environment of the Ti3+ species through detection of hyperfine interactions of the unpaired electron with magnetically active nuclei of the matrix, including natural abundant framework 29Si. The results provide evidence for the reducing power of triethylaluminium towards isolated Ti4+ ions through the formation of open-shell Ti3+ ions atomically dispersed and fully incorporated in the SiO2 framework with a local structure similar to that of titanium silicalite and no segregation of TiO2 phases at this level of Ti doping.

Gd3+-Doped Magnetic Nanoparticles for Biomedical Applications

Magnetic nanoparticles (MNPs) made of iron oxides with cubic symmetry (Fe3O4, γ-Fe2O3) are demanded objects for multipurpose in biomedical applications as contrast agents for magnetic resonance imaging, magnetically driven carriers for drug delivery, and heaters in hyperthermia cancer treatment. An optimum balance between the right particle size and good magnetic response can be reached by a selection of a synthesis method and by doping with rare earth elements. Here, we present a microwave-assisted polyol synthesis of iron oxide MNPs with actual gadolinium (III) doping from 0.5 to 5.1 mol.%. The resulting MNPs have an average size of 14 nm with narrow size distribution. Their surface was covered by a glycol layer, which prevents aggregation and improves biocompatibility. The magnetic hyperthermia test was performed on 1 and 2 mg/ml aqueous colloidal solutions of MNPs and demonstrated their ability to rise the temperature by 3°C during a 20–30 min run. Therefore, the obtained Gd3+ MNPs are the promising material for biomedicine.

The Atomic Structure of Cu(II) Acetate-Bipyridine Under Thermal Decomposition: An X-Ray Spectroscopy Study

A number of experimental techniques were used to study the changes in the atomic structure of copper(II) acetate-bipyridine under thermal decomposition between 25°C and 700°C to form copper-containing nanoparticles. The dynamics of structural changes during decomposition in a thermogravimetric chamber is compared with X-ray absorption spectra, IR spectra, and diffraction patterns for a sequence of annealing temperatures. The experimental results were used to construct theoretical structural models of the complex under thermal decomposition.

Characterization of local atomic structure in Co/Zn based ZIFs by XAFS

The local atomic structure in bimetallic Co/Zn zeolitic imidazolate frameworks (ZIFs) was studied using X-ray Absorption Fine Structure (XAFS) spectroscopy and theoretical calculations. The experimental Co K-edge and Zn K-edge XANES (X-ray Absorption Near Edge Structure) spectra of Zn1-xCoxC8H10N4 samples (x = 0.05, 0.25, 0.75) synthesized by microwave synthesis were compared with the data for the ZIF-67 (x=1) and ZIF-8 (x=0). Theoretical XANES spectra for the bimetallic ZIFs were calculated. It was shown that in bimetallic ZIFs the Co and Zn atoms have the similar local environment.

Mechanical activation and physical properties of Pb(Zr0.56Ti0.44)O3

ABSTRACT The Pb(Zr0.56Ti0.44)O3 (PZT) ceramics was subjected to a pressure-induced activation at 320 MPa in a Bridgman anvil, where a load pressure was combined with a shear deformation. The induced changes in the linear and angular parameters of a unit cell, in the ratio of coexisting rhombohedral (R3m) and tetragonal (P4mm) phases as well as in the dielectric properties were analyzed.