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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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Decomposition kinetics of phenithrothion organophosphate in decontamination foam-forming mixtures
Míčová, Jitka ; Doležal, Pavel (advisor) ; Musilová, Marie (referee)
The work focuses on the investigation of the kinetics of the reactions of organophosphate fenitrothione with hydroperoxide anion in the environment of micelles made up by cationic and non-ionic tensides. The influence of the length of the alkyl lipophilic chain was observed using benzalconium type tensides and theinfluence of the length of alkyl chain and of an ethoxylation degree was evaluated using non-ionic tensides type ethoxylated linear alcohols. The influence of a weight proportion of both the tenside types in a reaction mixture was also investigated. The change of the evaluated parameters cause only little changes in reaction rate, not more than in one order rank. It was also found that the change of the concentration of peroxide is a parameter having much greater influence; it can change the reaction rate even in several orders rank. The reaction rate of fenitrothione depends on the hydroperoxide concentration in a linear pattern.
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Plasma hydrogenation of hydrothermally grown ZnO micropods
Remeš, Zdeněk ; Aubrechtová Dragounová, Kateřina ; Mičová, J.
The hydrothermally grown ZnO micropods have been placed on grounded stainless-steel holder and exposed to an inductively coupled plasma (ICP) monitored in-situ by optical emission spectroscopy (OES). OES shows the immediate release of oxygen during Ar ion bombardment. The prolonged exposure to hydrogen plasma leads to deterioration of the optical properties as well. The exposure, rf power and hydrogen pressure have been optimized to enhance UV-photoluminescence peak at the wavelength 384 nm related to surface bounded excitons and reduce the defect-related photoluminescence in red spectral range. The strong UV photoluminescence appears just after 1 minute of plasma hydrogenation in a radio frequency plasma discharge with power density 40 W/dm3 and hydrogen pressure 17 Pa.
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Mass production of hydrogenated ZnO nanorods
Chang, Yu-Ying ; Remeš, Zdeněk ; Míčová, J.
We have developed an inexpensive and efficient technology of hydrothermal growth of ZnO nanorods from zinc nitrate hexahydrate (Zn(NO3)2·6H2O), as a precursor and hexamethylenetetramine (HMTA) (C6H12N4), as a surfactant followed by plasma hydrogenation in a novel inductively coupled plasma (ICP) quartz reactor and equipped with the rotary sample holder to stir powder during plasma treatment. We have optimized the photoluminescence spectroscopy for measuring optical scattering samples with the high sensitivity, precise sample positioning and very low influence of the scattered excitation light. Here we present the latest results on the enhancement of the UV photoluminescence of the ZnO nanorods after plasma hydrogenation. The exciton-related photoluminescence has been significantly enhanced whereas the deep defect related yellow photoluminescence has been significantly decreased.\n
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Comparison of microbial interactions of zinc oxide nanomaterials in various size and shape
Rutherford, D. ; Jíra, J. ; Mičová, J. ; Remeš, Zdeněk ; Hsu, H.S. ; Rezek, B.
Zinc oxide nanoparticles (ZnO NP) have shown great potential as a novel antibacterial material at a time when resistance towards conventional antibiotics is becoming more prevalent. We report bacteria inactivation by ZnO NP with novel hedgehog-like morphology using model gram-negative (E. coli) and gram-positive (S. aureus) bacteria. E. coli exposed to the novel ZnO hedgehog NP during growth resulted in 4 orders of magnitude reduction in viable cell concentration after 24 h, which is more than 2 orders higher reduction compared to commercially available ZnO NPs with nominal sizes from 50 nm to 20 um. There was a positive correlation between hedgehog NP concentration and bacteria cell concentration reduction within the range tested 0.1 – 1.0 mg/mL. S. aureus was less sensitive to ZnO NP exposure and inactivation effect of various ZnO NP, was comparable. The effect can be thus attributed to direct mechanical damage of the bacterial mebrane that is the most effective for the novel hedgehog ZnO NP. This conclusion was corroborated also by disk diffusion assays.\n
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The photoluminescence and optical absorptance of plasma hydrogenated nanocrystalline ZnO thin films
Remeš, Zdeněk ; Chang, Yu-Ying ; Stuchlík, Jiří ; Mičová, J.
We have developed the technology of the deposition of the nominally undoped ZnO nanocrystalline thin films by DC reactive magnetron sputtering of Zn target in the gas mixture of argon and oxygen plasma. We have optimized the photoluminescence spectroscopy for measuring optically scattering thin layers with the high sensitivity, precise sample positioning and very low influence of the scattered excitation light. Here we present the latest results on the enhancement of the photoluminescence of the nanocrystalline ZnO thin films after plasma hydrogenation. The photoluminescence in near UV region has been enhanced whereas the deep defect related photoluminescence has been significantly decreased. We found good room temperature stability of the plasma hydrogenated ZnO nanocrystals in air, but fast degradation at elevated temperature\n
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Preparation of zinc oxide nanorods colloid from thin layers
Mičová, Júlia ; Remeš, Zdeněk ; Chang, Yu-Ying ; Neykova, Neda
The interest in ZnO (zinc oxide) nanoparticles is increasing due to low cost of their processing as well as the ability of fabricating ZnO nanostructures with controllable morphology such as size, shape and orientation. Our choice of method of the preparation of the nanostructured thin ZnO layers is the hydrothermal growth of ZnO nanorods on glass substrates coated by the nucleation layer deposited by the reactive magnetron sputtering. We have developed and optimized conditions of the thin layer growth with controllable dimensions of nanorods followed by the ultrasound peeling. The colloid of ZnO nanorods was characterized by measuring the size of particles using the dynamic light scattering (DLS) and the scanning electron microscopy (SEM). We found that the dynamic light scattering (DLS) can’t be directly used for size evaluation of ZnO nanorods due to their non- sperical shape. \n
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Decomposition kinetics of phenithrothion organophosphate in decontamination foam-forming mixtures
Míčová, Jitka ; Doležal, Pavel (advisor) ; Musilová, Marie (referee)
The work focuses on the investigation of the kinetics of the reactions of organophosphate fenitrothione with hydroperoxide anion in the environment of micelles made up by cationic and non-ionic tensides. The influence of the length of the alkyl lipophilic chain was observed using benzalconium type tensides and theinfluence of the length of alkyl chain and of an ethoxylation degree was evaluated using non-ionic tensides type ethoxylated linear alcohols. The influence of a weight proportion of both the tenside types in a reaction mixture was also investigated. The change of the evaluated parameters cause only little changes in reaction rate, not more than in one order rank. It was also found that the change of the concentration of peroxide is a parameter having much greater influence; it can change the reaction rate even in several orders rank. The reaction rate of fenitrothione depends on the hydroperoxide concentration in a linear pattern.
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