Radim Hrdy

Preparation and properties of various magnetic nanoparticles.

The fabrications of iron oxides nanoparticles using co-precipitation and gadolinium nanoparticles using water in oil microemulsion method are reported in this paper. Results of detailed phase analysis by XRD and Mössbauer spectroscopy are discussed. XRD analysis revealed that the crystallite size (mean coherence length) of iron oxides (mainly γ-Fe2O3) in the Fe2O3 sample was 30 nm, while in Fe2O3/SiO2 where the ε-Fe2O3 phase dominated it was only 14 nm. Gd/SiO2 nanoparticles were found to be completely amorphous, according to XRD. The samples showed various shapes of hysteresis loops and different coercivities. Differences in the saturation magnetization (MS) correspond to the chemical and phase composition of the sample materials. However, we observed that MS was not reached in the case of Fe2O3/SiO2, while for Gd/SiO2 sample the MS value was extremely low. Therefore we conclude that only unmodified Fe2O3 nanoparticles are suitable for intended biosensing application in vitro (e.g. detection of viral nucleic acids) and the phase purification of this sample for this purpose is not necessary.

OCCURRENCE OF GLOBULE OF DEBRIS ON SURFACES MACHINED BY WEDM

e-mail:mouralova@fme.vutbr.cz Wire electrical discharge machining (WEDM) cuts material using the principles of electroerosion, which conclusively defines the resulting morphology of the machined surface. During the erosion process, removal of tiny particles of material (tiny globules) is achieved using a stream of dielectric. On certain surfaces, these tiny globules get stuck during the thermaltreatment and remain on the machined surface. This thesis studies these globules of debris on foursamples of two metallic materials with various heat treatment using electron microscopy.Furthermore, a part of the globule was removed using a focused iont beam, which allowed for studying its inside and analyzing the chemical composition in its individual parts.

Cu 2 O based electrochemical sensor for direct glucose detection

Two types of working electrodes of electrochemical sensors were fabricated using screen-printing and spray-coating deposition methods and previously synthetized Cu2O micro/nanoparticles and used for direct electrochemical glucose detection. Glucose was successfully electrochemically detected against conventional Ag/AgCl reference electrode and platinum auxiliary electrode at potential of 0.5 V and 0.75 V for spray-coated and screen-printed electrode, respectively. Better sensitivity was observed using spray-coated electrode. For both electrodes types we obtained linear calibration curve in physiological range of concentrations from 0.5 to 10 mmol/L. Furthermore, the limit of detection lower than 100 μmol/L was achieved.

Electrochemical transducer utilizing nanowires surface

Recent research showed the availability of atmospheric pollutant monitoring using a gas sensor with nanostructured surface of sensing electrode which can be prepared through an anodization process. [1, 2] The use of anodization technique for obtaining oxide porous material which can be used e. g. as nano-template was firstly reported in the work of Masuda et al. The aim of presented work is the fabrication of Au nanowires further modified with TiO2 layer to improve the electrode sensing properties due to increasing its specific surface.

Simultaneous detection of purine bases on Cu 2 O nanoparticles based electrochemical biosensor

Electrochemical determination of purine bases using screen-printed and spray-coated working electrodes on alumina substrate based on Cu2O nanoparticles is described in this work. Cu2O nanoparticles were synthetized using simple precipitation method and used for thick-film planar microelectrodes fabrication. The Cu2O nanoparticles were characterized by SEM and XRD analysis, which showed the presence of spherical aggregations with diameter of 1000 nm. Fabricated working electrodes based on these Cu2O nanoparticles were successfully used for adenine and guanine determination. The purine bases were detected indirectly by reduction of Cu ions. The current response of both electrodes types decreased with increasing adenine or guanine concentration. More sensitive detection was achieved with spray-coated electrodes with higher active surface area.

Advanced templates-base technique for preparation of nanomechanized sensors surface

This work presents actual modern technique for preparation of nanomechanized surface for sensors application. One of them is metal electrodes which are covered by metal nanowires the second one is array of separated metal nanoelectrods. Central to this issue is the development sensors for high sensitivity, high selectivity, high stability and rapid detection in field chemical and bio-chemical application. With special geometry and chemical and physical properties, one-dimensional metal oxide nanostructures have become the promising candidates. The nanowires were successfully prepared by electroplating to the anodized alumina template. Scanning electron microscopy (SEM) images elemental analysis provides morphological and compositional information of the metal and metal oxide nanowires.