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SERS-TAGS: Selective immobilization and detection of bacteria using specific antibodies and surface-enhanced Raman scattering
Benešová, Markéta ; Bernatová, Silvie ; Samek, Ota ; Pokorná, Zuzana ; Mika, Filip ; Kizovský, Martin ; Pilát, Zdeněk
Raman spectroscopy is a non-destructive instrumental analytical technique based on Raman scattering, which is the inelastic scattering of photons that occurs when interacting with electrons in chemical bonds. With the help of Raman spectroscopy, chemical compounds, their mixtures and biological samples, including living organisms, can be analyzed very quickly, non-contactly and non-destructively. The performed measurements can be compared with spectra databases. A problem with Raman spectroscopy is that samples sometimes give a weak signal that is often overlaid by intense fluorescence. SERS (surface-enhanced Raman spectroscopy) is used to amplify Raman scattering.
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Microstructure modifications of Al-Si-coated press-hardened steel 22MnB5 by laser welding
Šebestová, Hana ; Horník, Petr ; Mika, Filip ; Mikmeková, Šárka ; Ambrož, Ondřej ; Mrňa, Libor
Weld microstructure depends on the characteristics of welded materials and parameters of welding technology, especially on the heat input that determines the peak temperature and the cooling rate. When the coated sheets are welded, the effect of the chemical composition of the coating must be also considered even though its thickness is only a few tens of microns. During 22MnB5+AlSi laser welding experiments, the ferrite-stabilizing elements of coating modified the weld metal microstructure. Ferrite appeared in a quenched weld metal. The rapid cooling rate accompanying welding with a focused beam limited the homogenization of the weld metal which resulted in the formation of ferritic bands in the regions rich in Si and especially in Al. On the other hand, a high level of homogenization was reached when welding with the defocused beam. The ferritic islands uniformly distributed in the weld metal were formed at 0.4 wt% and 1.6 wt% of Si and Al, respectively. The doubled heat input reduced the Al content to 0.7 wt% insufficient for the ferrite formation at still relatively high cooling rates. Predicting the distribution of ferrite in the weld metal is challenging due to its dependence on various factors, such as cooling rate and the volume of dissolved coating, which may vary with any modifications made to the welding parameters.
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