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Your search keyword '"Čeppan, Michal"' showing total 42 results
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42 results on '"Čeppan, Michal"'

28. Analysis of laser and inkjet prints using spectroscopic methods for forensic identification of questioned documents

Author

Gál, Lukáš, Belovičová, Michaela, Oravec, Michal, Palková, Miroslava, and Čeppan, Michal

Subjects
spectroscopy, inkjet, document, laser
Abstract

The spectral properties in UV-VIS-NIR and IR regions of laser and inkjet prints were studied for the purposes of forensic analysis of documents. The procedures of measurements and processing of spectra of printed documents using fibre optics reflectance spectroscopy in UV-VIS and NIR region, FTIR-ATR with diamond/ZnSe and germanium crystals were optimized. It was found that the shapes of spectra of various black laser jet prints and inkjet prints generally differ in the spectral regions UV-VIS-NIR and IR. However, the resolution of individual spectra, and hence of individual printers, based on the simple visual comparison is not reliable enough. However, using of these spectra for identification of individual printers should be enhanced by computational chemometric methods.

Published
2013

29. Study of surface-enhanced infrared absorption spectroscopy (SEIRAS) of black inkjet prints using silver colloid.

Author

Oravec, Michal, Miura, Katsuya, and Čeppan, Michal

Subjects
INFRARED absorption, SILVER nanoparticles, FOURIER transform infrared spectroscopy, INFRARED spectroscopy, SCANNING electron microscopy, COLLOIDS
Abstract

Only black inkjet prints were studied with regard to forensic examination of documents. We analysed twenty-one inkjet prints using surface-enhanced infrared absorption spectroscopy (SEIRAS). The present paper deals with micro-destructive document analysis based on silver nanoparticles (AgNPs) use to obtain surface enhanced ATR-FTIR (attenuated total reflection -- Fourier transform infrared) spectra directly from the document. For this experiment, AgNPs in colloid form was applied. AgNPs for SEIRAS analyses were synthesised and afterwards analysed by scanning electron microscopy (SEM). The purpose of the enhancement of colloids was to improve the resolution of the absorption signal of the analysed samples from noise. In the experiment, the obtained ink ATR-FTIR spectra, with and without silver treatment, were significantly affected by the paper base. [ABSTRACT FROM AUTHOR]

Published
2017
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39. Photoelectrochemical properties of TiO x layers prepared by DC pulsed unbalanced reactive magnetron sputtering.

Author

Mikula, Milan, Čeppan, Michal, Kindernay, Juraj, and Búc, Dalibor

Abstract

Three sets of titanium oxide layers with different oxygen content were prepared by DC pulsed reactive magnetron sputtering. The layers were characterised by their thickness, conductivity, refractive index, band-gap and flat band potential. The photoelectric and photocatalytic activities of the layers irradiated by Xe discharge lamp were tested in NaOH and phenol water solution, respectively. Rather high activity of prepared layers was found; no expressive activity increase was, however, observed in contrary to the expectation connected with suboxide forms of TiO x. [ABSTRACT FROM AUTHOR]

Published
1999
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40. Effect of Ti pretreatment on photoelectric properties of TiO2 layers prepared by plasma-anodic oxidation

Author

Mikula, Milan, Blecha, Jozef, Čeppan, Michal, and Panák, Ján

Abstract

Photoactive TiO2 layers were formed by anodic oxidation of Ti in O2 RF plasma under various conditions and Ti surface pretreatment. The photocurrent spectrum in 1M NaOH was used to calculate the quantum efficiency of the photocurrent production and the band-gap energy for indirect transitions. Photoelectrochemical properties of TiO2 layers were studied on the decomposition of p-cresol water solution. The method of Ti surface pretreatment (mechanical polishing or chemical etching) has a decisive influence on the photoelectrochemical properties and the structure of the polycrystalline oxide, rutile, anatase or amorphous phase content.

Published
1995
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