Kristina Zagar

Jožef Stefan Institute | IJS · Department of Nanostructured Materials

A reagentless third generation electrochemical glucose biosensor was fabricated based on wiring the template enzyme glucose oxidase (GOx) with graphene nanoribbons (GN) in order to create direct electron transfer between the co-factor (flavin adenine dinucleotide, FAD) and the electrode. The strategy involved: (i) isolation of the apo-enzyme by sep...

We report on synthesis and characterization of a novel group of compounds based on copper, gadolinium, and calcium. Cu-Ca and Cu-Gd binaries were previously studied while Ca and Gd are known to be immiscible themselves. The effects of substituting Gd with Ca in Cu 5 Gd 1−í µí±¥ Ca í µí±¥ compounds (0 ≤ í µí±¥ ≤ 1) were studied by investigating the...

We studied the effects of substituting gadolinium in the compound Cu5Gd with Ca by investigating the phase stability and crystal structure of the resulting new compounds. For rapidly quenched materials produced by melt spinning, the crystal structure was always hexagonal P6/mmm, irrespective of the Ca addition (x) in alloys with the formula Cu5Gd1-...

To understand developmental processes it is essential to consider both, molecular / genetic data and structural aspects of morphogenesis and differentiation. Integration of both approaches is beneficial to interpret the data obtained and unravel tissue and organism formation. Sequential morphological changes during animal development can be followe...

A continuous-flow, coil-type photoelectrocatalytic microreactor for the degradation of caffeine was designed, assembled and characterized. Its main components are the photocatalytically active anode and the cathode coils, which are wrapped around a silica-glass rod and placed into a UV-transparent housing. The anode coil was prepared by anodic oxid...

Skeletal elements that are exposed to heavy mechanical loads may provide important insights into the evolutionary solutions to mechanical challenges. We analyzed the microscopic architecture of dactylus claws in the woodlice _Porcellio scaber_ and correlated these observations with analyses of the claws’ mineral composition with energy dispersive X...

Self-ordered, vertically aligned, titanium oxide (TiO2) nanotubes were grown on an electropolished titanium foil by anodic oxidation in a viscous organic electrolyte. We chose two different anodization times to obtain nanotubes of approximately 9 and 17 μm in length. Some of the TiO2 nanotubes were post-treated with TiCl4 or hydrothermally with TiO...

Several Cu-Gd-Ca alloys were prepared by arc-melting and melt-spinning in order to find quasicrystals or complex approximants. Up to date no complex structure was identified in our Cu-Gd-Ca samples, but we rather report on novel high temperature phases, which serve as a framework for ternary phase diagram. To the best of our knowledge we are the fi...

This is a draft of a paper, which describes the mechanism of coercivity improvement of MQ-II-type permanent magnets by the reaction between DyF3 and Nd2Fe14B, diffusion of Dy and formation of (Nd,Dy)2Fe14B phase..

This volume of the IOP Conference Series: Materials Science and Engineering contains papers from the 14th Workshop of the European Microbeam Analysis Society (EMAS) on Modern Developments and Applications in Microbeam Analysis which took place from the 3rd to the 7th of May 2015 in the Grand Hotel Bernardin, Portorož, Slovenia. The primary aim of t...

The effects of carbon nanotubes (CNTs) and gold nanoparticles (AuNPs) for the detection of ascorbic acid (AA) were elucidated and their performance as modifiers in carbon paste and screen printed carbon electrodes was compared to unmodified electrodes. The studies were made with cyclic voltammetry (CV) and flow injection analysis (FIA). As a suppor...

An ethanol biosensor based on alcohol dehydrogenase (ADH) attachedto Au seeds decorated on magnetic nanoparticles (Fe3O4@Au NPs) is presented. ADH was immobilized on Fe3O4@Au NPs, which were subsequently fixed by a magnet on a carbon paste electrode modified with 5 % (m:m) MnO2. Optimum conditions for the amperometric determination of ethanol with...

The rare-earth crisis, which peaked in the summer of 2011 with the prices of both light and heavy rare earths soaring to unprecedented levels, brought about the widespread realization that the long-term availability and price stability of rare earths could not be guaranteed. This triggered a rapid response from manufacturers involved in rare earths...

Powder ZnAl2O4 (gahnite) samples doped with 0, 4.3, 7.6 and 11.7 at.% Mn (in relation to Zn) were prepared by a sol-gel technique followed by thermal treatment. The effect of manganese doping on microstructure of the samples has been investigated by transmission electron microscopy and X-ray diffraction. Diffraction patterns showed that all samples...

itanium dioxide (TiO2) rutile nanoparticles were synthesized at temperatures below 100 °C using a gel-sol process that provides control of the final particles' characteristics, such as the nanoparticle size, morphology, crystal structure and crystallinity. The synthesized rutile nanoparticles were analyzed using X-ray powder diffraction (XRD), scan...

Exoskeletal crustacean cuticle is a calcified apical extracellular matrix of epidermal cells, illustrating the chitin-based organic scaffold for biomineralization. Studies of cuticle formation during molting reveal significant dynamics and complexity of the assembly processes, but cuticle formation during embryogenesis is poorly investigated. This...

Titanate nanotubes (TiNTs) and silver-decorated titanate nanotubes (TiNTs@Ag) were synthesized using the hydrothermal method. In the decorated nanotubes the silver particles were obtained by the photoreduction of AgNO3 under UV light. Pure and Ag-decorated nanotubes were high-temperature heat treated at 550 °C in a hydrogen atmosphere and the “core...

A photocatalytic, TiO2-based microreactor is designed and fabricated on a metal-titanium foil. The microchannel is mechanically engraved in the substrate foil and a double-layered TiO2 anatase film is immobilized on its inner walls with a two-step synthesis, which included anodization and a hydrothermal treatment. X-ray diffraction (XRD) and scanni...

Titanates are suitable for many applications such as oxygen sensing and tunable HTS (high temperature superconducting) microwave filters. The potential advantages of the nanostructured forms have been however scarcely explored compared to other oxides. In this work, the structural and electrical properties of individual iron-doped strontium titanat...

Description of laboratory work and results on coercivity enhancement of commercial rapidly quenched Nd-Fe-B powders (MQ-II magnets from Molycorp, Singapore) by reaction with DyF3 during spark-plasma sintering. The maximum 33% Hci improvement compared to raw material was achieved at 2.6 wt.% Dy addition after 10 hours of annealing in highly pure (99...

In the present work, multiphase polycrystalline BTO nanorods were synthesized using template-assisted sol–gel deposition and their structural evolution was studied using thermo Raman spectroscopy, X-ray diffractometry and high-resolution transmission electron microscopy (HRTEM). In the BTO nanorods, the tetragonal phase was the dominant one, while...

Crustaceans form a variety of calcium deposits in which they store calcium necessary for the mineralization of their exoskeletons. Calcium bodies, organs containing large amounts of calcium, have been reported in some terrestrial isopod crustaceans, but have not yet been extensively studied. We analyzed the architecture of these organs during the m...

We report on an improved sol-gel method for the production of highly photocatalytic titanium dioxide (TiO 2) anatase nanoparticles which can provide appropriate control over the final characteristics of the nanoparticles, such as particle size, crystallinity, crystal structure, morphology, and also the degree of agglomeration. The synthesized anata...

In this work, we report on the integration of individual BaTiO(3) nanorods into simple circuit architectures. Polycrystalline BaTiO(3) nanorods were synthesized by electrophoretic deposition (EPD) of barium titanate sol into aluminium oxide (AAO) templates and subsequent annealing. Transmission electron microscopy (TEM) observations revealed the pr...

A series of intergrowth bismuth-layered ferroelectric Bi7Ti4NbO21 materials are reactive-sintered at 1050 to 1150°C from Bi3TiNbO9 and Bi4Ti3O12 parent phases to infer their structural characters and microstructure relations. Various types of stacking faults are revealed in the intergrowth structure with extra Bi3TiNbO9 or Bi4Ti3O12 layer(s) by hig...

An electron-microscopy investigation was performed on BaTiO3 nanorods that were processed by sol–gel electrophoretic deposition (EPD) into anodic aluminium oxide (AAO) membranes. The BaTiO3 nanorods grown within the template membranes had diameters ranging from 150 to 200nm, with an average length of 10–50μm. By using various electron-microscopy te...

The full text of the corrigendum is available in the pdf provided.

We report on an unusual crystallization phenomenon that results in the self-assembly of sub-micron tubules of crystalline SrTiO3. The deposition of the tubular structures was done in the pores of anodized aluminum oxide templates by the electrophoretic deposition of SrTiO3 sols and subsequent annealing. Homogeneous nucleation inside the pores produ...

A Transient Current Technique (TCT) utilizing an IR laser with 100 ps pulse width and beam diameter of FWHM = 8 m was used to evaluate non-irradiated and irradiated p-type silicon micro-strip detectors. The beam was parallel with the sur-face and perpendicular to the strips (Edge-TCT) so that the elec-tron hole pairs were created at known depth in...

Bismuth ferrite, BiFeO3 (BFO), was synthesized in a hydrothermal process without the introduction of any metal cations, other than Fe3+ and Bi3+. For this purpose, a strong organic hydroxide was used for the precipitation of the bismuth and iron salts. With the aim to study the molar range for the production of BFO in the Bi–Fe–O system under hydro...

Complex metal oxides with perovskite structure are important materials for various applications in microelectronics industry and technology. They can be used as sensors, catalysts and composites with defined electrical properties. For many applications the physical properties of these perovskite ceramics strongly depend on their surface/volume rati...