Density functional study of gallium clusters on graphene: electronic doping and diffusion

Motivated by experimental results on transport properties of graphene covered by gallium atoms, the density functional theory study of clustering of gallium atoms on graphene (up to a size of 8 atoms) is presented. The paper explains a rapid initial increase of graphene electron doping by individual Ga atoms with Ga coverage, which is continually reduced to zero, when bigger multiple-atom clusters have been formed. According to density functional theory calculations with and without the van der Waals correction, gallium atoms start to form a three-dimensional cluster from five and three atoms, respectively. The results also explain an easy diffusion of Ga atoms while forming clusters caused by a small diffusion barrier of 0.11 eV. Moreover, the calculations show this barrier can be additionally reduced by the application of an external electric field, which was simulated by the ionization of graphene. This effect offers a unique possibility to control the cluster size in experiments only by applying a gate-voltage to the graphene in a field-effect transistor geometry and thereby without growth temperature assistance.Grant Agency of the Czech RepublicGrant Agency of the Czech Republic [17-21413S]; Ministry of Education, Youth and Sports from the Large Infrastructures for Research, Experimental Development and Innovations project 'IT4 Innovations National Super-computing Center' [LM2015070

Mechanism and Suppression of Physisorbed-Water-Caused Hysteresis in Graphene FET Sensors

Hysteresis is a problem in field-effect transistors (FETs) often caused by defects and charge traps inside a gate isolating (e.g., SiO2) layer. This work shows that graphene-based FETs also exhibit hysteresis due to water physisorbed on top of graphene determined by the relative humidity level, which naturally happens in biosensors and ambient operating sensors. The hysteresis effect is explained by trapping of electrons by physisorbed water, and it is shown that this hysteresis can be suppressed using short pulses of alternating gate voltages.Grant Agency of the Czech RepublicGrant Agency of the Czech Republic [17-21413S]; H2020 Twinning Programme (Project SINNCE) [810626]; MEYS CR [LQ1601 CEITEC 2020, LM2015041

Correlative Raman imaging and scanning electron microscopy: The role of single Ga islands in surface-enhanced Raman spectroscopy of graphene

Surface-enhanced Raman spectroscopy (SERS) is a perspective nondestructive analytic technique enabling the detection of individual nanoobjects, even single molecules. In this paper, we have studied the morphology of Ga islands deposited on chemical vapor deposition graphene by ultrahigh vacuum evaporation and local optical response of this system by the correlative Raman imaging and scanning electron microscopy (RISE). Contrary to the previous papers, where only an integral Raman response from the whole ununiformed Ga nanoparticles (NPs) ensembles on graphene was investigated, the RISE technique has enabled us to detect graphene Raman peaks enhanced by single Ga islands and particularly to correlate the Raman signal with the shape and size of these single particles. In this way and by a support of numerical simulations, we have proved a plasmonic nature of the Raman signal enhancement related to localized surface plasmon resonances. It has been found that this enhancement is island-size-dependent and shows a maximum for medium-sized Ga islands. A reasonable agreement between the simulations of the plasmon enhancement of electric fields in the vicinity of Ga islands and the experimental intensities of corresponding Raman peaks proved the plasmonic origin of the observed effect known as SERS. © 2022 American Chemical Society.European Commission, EC: 71020004, 810626; Grantová Agentura České Republiky, GA ČRCzech Science FoundationGrant Agency of the Czech Republic [20-28573S]; European Commission (H2020-Twininning project)European Commission [810626.SINNCE, M-ERA NET HYSUCAP/TACR-TH71020004]; *BUT*.specific research [*FSI-S-20-648*5]; Ministry of Education, Youth and Sports of the Czech Republic (CzechNanoLab Research Infrastructure) [LM2018110

Effect of pomiferin administration on kidney ischaemia-reperfusion injury in rats

The aim of the study was to analyse protective effects of different doses of pomiferin in therapy of reperfusion injury. Rats were randomly divided into five groups (n=10). One group was intact. Three medicated groups and one placebo group were subjected to ischaemia and reperfusion of the left kidney. Pomiferin was administrated by single gastric gavage in 2 ml of 0.5% Avicel solution in doses of 5, 10 and 20 mg/kg. The placebo group was given only Avicel solution. On day 15, all the animals were exsanguinated and the reperfused kidneys were recovered. Selected biochemical markers were assessed in blood: antioxidative enzymes, total antioxidative capacity, malondialdehyde, creatinine, urea and uric acid. Creatinine, urea and total proteins were analysed in urine and 24-hour diuresis was recorded. The kidney tissue samples were used for histopathological examination

Guided assembly of nanoparticles on electrostatically charged nanocrystalline diamond thin films

We apply atomic force microscope for local electrostatic charging of oxygen-terminated nanocrystalline diamond (NCD) thin films deposited on silicon, to induce electrostatically driven self-assembly of colloidal alumina nanoparticles into micro-patterns. Considering possible capacitive, sp2 phase and spatial uniformity factors to charging, we employ films with sub-100 nm thickness and about 60% relative sp2 phase content, probe the spatial material uniformity by Raman and electron microscopy, and repeat experiments at various positions. We demonstrate that electrostatic potential contrast on the NCD films varies between 0.1 and 1.2 V and that the contrast of more than ±1 V (as detected by Kelvin force microscopy) is able to induce self-assembly of the nanoparticles via coulombic and polarization forces. This opens prospects for applications of diamond and its unique set of properties in self-assembly of nano-devices and nano-systems

Vytápění se zajištěním ohřevu teplé vody a vnitřní kanalizace ve výrobně-administrativním objektu

Import 20/09/2006Prezenční225 - Katedra pozemního stavitelstv

Fixed Fire Extinguishing Systems in Civic Facilities

Import 01/09/2009BARTOŠÍK, Martin. SHZ v objektech občanské výstavby: diplomová práce. Ostrava: VŠB TU, Fakulta bezpečnostního inženýrství, 2009. 81 str. Vedoucí diplomové práce Ing. Isabela Bradáčová Csc. V diplomové práci jsem se zaměřil na specifikaci a obecné zásady stabilního hasicího zařízení, jeho činnost, statistiku a úspěšnost při hašení, a samotný návrh jsem aplikoval na vybrané obchodní centrum. Teoretická část je věnována požární ochraně, úkolům požární bezpečnosti staveb, požáru, jeho vlastnostem, procesu hoření a způsob hašení při aplikaci stabilního hasicího zařízení. Obsahuje legislativní informace, rozdělení, obecné zásady a funkci stabilního hasicího zařízení. V praktické části jsem aplikoval obecné zásady na návrh stabilního hasicího zařízení do obchodního centra Olympia Brno. Diplomová práce bude sloužit pro zdokonalení praktických návrhů SHZ v projektování.BARTOŠÍK, Martin. Fixed Fire Extinguishing Dystems in Civil Facilities : thesis. Ostrava: VŠB TU, Faculty of safety Engineering, 2009. 81 s. Thesis supervisor Ing. Isabela Bradáčová Csc. In the thesis I focused on the specification and the general principles of a stable fire-fighting equipment, its activities, statistics and success in fighting, and the proposal itself, I applied to the selected business center. The theoretical part is devoted to fire protection, fire safety challenges of buildings, fire, it is characteristics, the process of burning and extinguishing method for the application of a stable fire-fighting equipment. Includes legislative information, distribution, general principles and function of a stable fire-fighting equipment. In the practical part, I applied the general principle to the proposal from a stable fire-fighting equipment in the shopping center Olympia Brno. Thesis will serve to improve the practical suggestions in designing SHZ.Prezenční030 - Katedra požární ochrany a ochrany obyvatelstvavýborn

Side charge propagation in simultaneous KPFM and transport measurement of humidity exposed graphene FET sensor

The surface diffusion (dissipation) of charge carriers enhanced by water molecules in solution-based biosensors and ambient operating gas sensors strongly influence their resistance response, sensitivity, and stability in time. Therefore, the information on the charge distribution at interfaces of conductive and insulating parts is essential for the operating sensors. This work presents the simultaneous measurement of the longitudinal macroscopic resistance response and local surface potential (SP) mapping by Kelvin probe force microscopy (KPFM) on a graphene Hall bar sensor. The results show the propagation of an electric charge from the main graphene channel onto the neighboring SiO2 surface. The charge propagation strongly increases with the relative humidity and can be controlled by a bottom-gate voltage used in most sensors based on a field effect transistor (FET) architecture. As proved by the longitudinal resistance measurements, the resulting side charge accumulation has a very small impact on the 2D resistivity of the graphene channel. It has been explained by an application of the Thomas-Fermi theory, proving an efficient screening of side accumulated charge potential caused by a redistribution of the charge inside the wide graphene channel. The combination of a transport resistance response and KPFM provides a deeper understanding of sensors/biosensors functionality and their design features than a simple resistance response usually observed. © 2023 Elsevier LtdMinisterstvo Školství, Mládeže a Tělovýchovy, MŠMT, (LM2023051, LQ1601 – CEITEC 2020); Grantová Agentura České Republiky, GA ČR, (23-07617S); European Regional Development Fund, ERDF, (CZ.1.05/1.1.00/02.0068

DFT study of water on graphene: Synergistic effect of multilayer p-doping

Recent experiments related to a study concerning the adsorption of water on graphene have demonstrated the p-doping of graphene, although most of the ab initio calculations predict nearly zero doping. To shed more light on this problem, we have carried out van der Waals density functional theory calculations of water on graphene for both individual water molecules and continuous water layers with coverage ranging from one to eight monolayers. Furthermore, we have paid attention to the influence of the water molecule orientation toward graphene on its doping properties. In this article, we present the results of the band structure and the Bader charge analysis, showing the p-doping of graphene can be synergistically enhanced by putting 4-8 layers of an ice-like water structure on graphene having the water molecules oriented with oxygen atoms toward graphene.AMISPEC, (TE01020233); INCHAR, (FW03010504); Technology Agency of the Czech Republic, TACR; Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT; Grantová Agentura České Republiky, GA ČR, (23-07617S); Vysoké Učení Technické v Brně, BUT, (FSI-S-23-8324)Grant Agency of the Czech Republic; Ministry of Education, Youth and Sports from the Large Infrastructures for Research; Technology Agency of the Czech Republic [TE01020233]; Specific Research grant of the Brno University of Technology [FSI-S-23-8324]; [23-07617S]Grant Agency of the Czech Republic; Ministry of Education, Youth and Sports from the Large Infrastructures for Research; Technology Agency of the Czech Republic [TE01020233]; Specific Research grant of the Brno University of Technology [FSI-S-23-8324]; [23-07617S