Synthesis of ZnO mesoporous powders and their application in dye photodegradation

ZnO materials have attracted considerable interest due to their large - scale potential applications for photodiodes, photocatalysis, sensing and others. For photocatalytical application, ZnO is usually prepared with a mesoporous structure, providing a large surface area for enhancing the system performance. Nowadays, various methods have been explored to prepare ZnO porous powders and films. Among them , the most important and more common techniques to synthetize mesoporous ZnO particles are wet chemical methods , including precipitation from inorganic or organic solution s and sol - gel, owing to their simplicity and low cost. Herein, we studied ZnO mesoporous powder synthesis based on preparation and further thermal decomposition of zinc hydroxide chloride hydrate precursor. The attention was given to the role of reaction medium in the formation of final products and to the photocatalytic activity of the synthesized ZnO.This work has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skło dowska - Curie grant agreement No 645662.publishe

Effect of fluoride-mediated transformations on electrocatalytic performance of thermally treated TiO2 nanotubular layers

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Electrocatalytic activity of Au nanoparticles onto TiO2 nanotubular layers in oxygen electroreduction reaction: size and support effects

Electrocatalytic activity of both bare high-ordered TiO2 nanotubes (TNTs) and gold nanoparticles (Au NPs) loaded TNTs toward oxygen reduction reaction (ORR) has been examined by cyclic voltammetry (CV). Cyclic voltammograms for Au NPs-TNT electrodes are characterized by an additional wave observed at less negative potentials which is responsible for oxygen electroreduction on the surface of gold NPs. The overpotential for O-2 reduction on the Au surface grows with increasing the temperature of TNT annealing and the Au NPs size. The nature of the effects observed was explained by peculiarities of the electron transport through Schottky barrier formed at the Au NPs - TiO2 interface. The width of the Schottky barrier, determined by semiconductor doping level and Au NPs size, plays a key role in the mechanism of electron transport through the space charge region. (C) 2016 Elsevier Ltd. All rights reserved

Electrocatalytic perfomance of nanostructured and compact titania films modified by gold nanoparticles

Основной целью настоящей работы является изучение влияния загрузки наночастиц Au на эффективность наноструктурированных и компактных пленок из диоксида титана

UV-assisted anchoring of gold nanoparticles into TiO2 nanotubes for oxygen electroreduction

Gold nanoparticles (AuNPs) have been deposited on titania nanotubular layers (TNT) via photocatalytic deposition, and the activity of the obtained AuNPs-TNT systems toward oxygen electroreduction reaction (ORR) in an alkaline medium has been studied and compared with the activity of AuNPs TNT composites prepared from Au colloidal solutions. Two photodeposition methods were utilized for anchoring of AuNPs: direct UV-irradiation of a TNT electrode immersed into a HAuCl4 containing solution (TNT-Au1 composites) and initial adsorption of AuCl4− ions on TNT followed by UV irradiation (TNT-Au2 composites). The size, spatial distribution, structure and surface of AuNPs deposited on TNT layers were studied via scanning and transmission electron microscopy, optical spectroscopy and underpotential deposition of lead ad-atoms on gold. It was found that these parameters depend on the photodeposition method. The TNT-Au2 composites have smaller size, higher surface concentration and more uniform distribution of AuNPs in the TNT layers as compared with the TNT-Au1 systems. The electrocatalytic efficiency of Au-TNT electrodes in ORR was found to depend on various factors such as doping level of TNT support (governed by annealing temperature), AuNPs size and their loading amount. The electroreduction of oxygen was observed at less negative potentials when Au nanoparticles were grown on the TNT surface by photoreduction in comparison with the TNT electrodes modified with AuNPs from sols. The enhanced activity of the photocatalytically prepared AuNPs-TNT composites can be explained by the consolidation of the interface between gold nanoparticles and TiO2 support and the absence of ligands on the AuNPs surface.publishe

One-step synthesis and growth mechanism of nitrate intercalated ZnAl LDH conversion coatings on zinc

An approach for the synthesis of ZnAl-NO3 LDH conversion coatings on zinc in an aqueous acidic Al(NO3)3/NaNO3 solution is demonstrated for the first time. The growth mechanism has been investigated using time resolved structural, microstructural and analytical methods. A LDH growth model involving both electrochemical and chemical processes is suggested.publishe

Light-Induced Proton Pumping with a Semiconductor: Vision for Photoproton Lateral Separation and Robust Manipulation

Energy-transfer reactions are the key for living open systems, biological chemical networking, and the development of life-inspired nanoscale machineries. It is a challenge to find simple reliable synthetic chemical networks providing a localization of the time-dependent flux of matter. In this paper, we look to photocatalytic reaction on TiO2 from different angles, focusing on proton generation and introducing a reliable, minimal-reagent-consuming, stable inorganic light-promoted proton pump. Localized illumination was applied to a TiO2 surface in solution for reversible spatially controlled inorganic photoproton isometric cycling, the lateral separation of water-splitting reactions. The proton flux is pumped during the irradiation of the surface of TiO2 and dynamically maintained at the irradiated surface area in the absence of any membrane or predetermined material structure. Moreover, we spatially predetermine a transient acidic pH value on the TiO2 surface in the irradiated area with the feedback-driven generation of a base as deactivator. Importantly we describe how to effectively monitor the spatial localization of the process by the in situ scanning ion-selective electrode technique (SIET) measurements for pH and the scanning vibrating electrode technique (SVET) for local photoelectrochemical studies without additional pH-sensitive dye markers. This work shows the great potential for time- and space-resolved water-splitting reactions for following the investigation of pH-stimulated processes in open systems with their flexible localization on a surface

pH-Sensitive fluorescent sensor for Fe(III) and Cu(II) ions based on rhodamine B acylhydrazone: Sensing mechanism and bioimaging in living cells

Spirocyclic rhodamine derivatives have great potential to be used as fluorescent sensors. Rho- damine B hydrazide (RBH) and its derivatives have been employed to detect various analytes. The interactions of a sensor with an analyte might result in the protonation or hydrolysis of the sensor. Understanding these processes is useful for developing new sensors with improved characteristics. In this work, the performance of rhodamine B acylhydrazone (RBA) as a sensor for Fe3+ and Cu2+ ions is evaluated. In the presence of these ions, RBA undergoes protonation and the spirolactam ring opening. The ring opening renders the dye colored and fluorescent. RBA is then hydrolyzed to RBH leading to the decay of the absorbance in the visible range. The protonation and hydrolysis of RBA are acid-catalyzed, and metal ions contribute to these processes by lowering pH. Metal ions, unlike hydrogen ions, catalyze the transformation of RBH into rhodamine B and a phenanthrenone derivative. These products exhibit emission bands in the visible and near-infrared ranges, respectively. The obtained results can be applied to a variety of sensors based on rhodamines and Schiff bases. RBA can be employed for bioimaging. RBA quickly penetrates into cells, localizes in the organelles with acidic pH, probably in lysosomes, persists there for a long time, and gives bright fluorescence in the visible range. Cell incubation with Cu2+ ions produces fluorescence in the near-infrared range. RBA can be used as a multifunctional fluorescent biosensor to visualize cell compartments with acidic pH and detect Cu2+ ions in living cells.publishe

Zn-Al LDH growth on AA2024 and zinc and their intercalation with chloride: Comparison of crystal structure and kinetics

The dissimilarities and features of the crystal structure of ZnAl LDH-NO3 conversion layers grown directly on pure zinc and aluminum alloy 2024 were investigated in the present paper. Although the nature of the cations in the double hydroxides are the same in both cases (Al3+ and Zn2+), their sources differ according to the substrate. This leads to a difference in the cationic layers and interlayer structure, which consequently influences the anionic exchange reaction. In the frame of this work, the kinetics of the anion-exchange of nitrate by chloride was investigated as well as the crystal structure of the resulting ZnAl LDH-Cl on both substrates. Synchrotron high-resolution X-ray diffraction was the main method to obtain structural information and was supported by additional calculations and scanning electron microscopy.The current study revealed noticeable changes on the positioning of the interlayer atoms for the ZnAl-LDH-Cl on zinc in comparison with the ones on AA2024 substrate