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Emergence of dark ZnO nanorods by hydrogen plasma treatment
Remeš, Zdeněk ; Buryi, Maksym ; Sharma, Dhananjay K. ; Artemenko, Anna ; Mičová, J. ; Rezek, B. ; Poruba, A. ; Hsu, H.S. ; Potocký, Štěpán ; Babin, Vladimir
We employed a custom-built inductively coupled plasma (ICP) 13.56 MHz reactor with up to 300 W RF discharge power. Hydrothermally grown ZnO nanorods were exposed to the ICP plasma with a mixture of hydrogen and argon for up to 30 min, followed in-situ by plasma oxidation. Plasma properties were monitored by optical emission spectroscopy (OES) and by measuring the self-bias potential of the stainless steel sample holder separated from the ground by a blocking capacitor. The exciton-related UV photoluminescence of ZnO nanorods and optical absorption increases significantly after the plasma treatment. We attribute it to the complex changes of ZnO surface electronic states that also give rise to its black color visually.
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Lead soaps in paintings: symptoms and the role of humidity
Garrappa, Silvia ; Švarcová, Silvie ; Kočí, Eva ; Hradilová, J. ; Bezdička, Petr ; Hradil, David
In this study, an overview of the symptoms of lead soaps reported in artworks in combination\nwith the study of the role of humidity on the formation of these degradation products have\nbeen thoroughly investigated. The use of optical microscopy, scanning electron microscopy\n(SEM) in combination with Fourier-transform infrared spectroscopy (FTIR) proved to be an\nefficient analytical approach to highlight both the saponified area of artworks’ samples and the\nformation of metal carboxylates within mock-up model systems. Optical microscopy revealed\nto be very useful for the first screening of samples embedded in resin, while SEM helped in\nthe detection and distribution of elements within the cross-sections. On the other hand, FTIR\nmicroscope proved to be a very powerful instrument for high-resolution point measurements\nperformed in the attenuated total reflection mode (ATR) mode with mercury-cadmium-telluride\n(MCT) detector, as well as for chemical imaging of larger area of both artworks’ and mock-up\nsamples performed in the ATR mode with focal plane arrays (FPA) detector. This study provides\nnew useful insights contributing to better understanding of factors affecting the paints‘ stability,\nwhich is neccesary for developing new efficient strategies for preservation and restoration of\nfatty-based painted artworks.
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