Justyna Grzonka

Sonication‐Assisted Low‐Temperature Routes for the Synthesis of Supported Fe–TiO2 Econanomaterials: Partial Photooxidation of Glucose and Phenol Aqueous Degradation

Fe‐doped TiO2‐supported photocatalytic materials prepared by the use of a mild ultrasound‐assisted protocol have been found to possess excellent selectivities in glucose oxidation and total phenol mineralization. These materials were characterized by a number of techniques such as XRD, diffuse reflectance UV/Vis spectroscopy, N2 physisorption, X‐ray photoelectron spectroscopy, SEM with X‐ray microanalysis, HRTEM, and flame atomic absorption spectroscopy. The proposed synthesis method was found to have a significant effect on textural properties, morphology, and visible‐light responsiveness of nanophotocatalysts. The dopant agent was found to be in the form of Fe3+ ions. The effects of the textural properties, together with the Fe presence and the adsorption ability of the material (acidic properties), seem to be involved in the optimum photocatalytic activities found for Fe–TiO2 supported on zeolite. In phenol photodegradation, although Fe doping demonstrated the detrimental effect on the conversion rate, an improvement in the direct mineralization of phenol to CO2 and water, particularly for the SiO2‐supported photocatalyst, with a negligible content of toxic byproducts in water has been observed in comparison with commercially available Evonik P25.

Fabrication and applications of multi-layer graphene stack on transparent polymer

In this report, we demonstrate the preparation method of a multi-layer stack with a pre-defined number of graphene layers, which was obtained using chemical vapor deposition graphene deposited on a copper substrate and subsequently transferred onto a poly(methyl methacrylate) (PMMA) substrate. The prepared multi-layer stack can also be transferred onto an arbitrary substrate and in the end, the polymer can be removed, which in consequence significantly increases the range of possible graphene applications. The multi-layer character was confirmed by optical transmittance measurements and Raman spectroscopy, whereas the microstructure of the multi-layer graphene stack was investigated using Scanning Electron Microscopy. The electrical properties in the function of the number of graphene layers were assessed with standard Hall Effect measurements. Finally, we showed the practical application of the multi-layer graphene stack as a saturable absorber of a mode-locked Er-doped fiber laser.

Iron‐Containing Titania Photocatalyst Prepared by the Sonophotodeposition Method for the Oxidation of Benzyl Alcohol

The sonophotodeposition method was applied in the synthesis of an iron‐containing titania photocatalyst. This procedure enables the use of sustainable energy sources, such as sonication and light, and eliminates the use of hazardous reducing agents. For the first time an ultrasonic horn and sun‐imitating Xenon lamp were used in this method. The following techniques: diffuse reflectance UV/Vis spectroscopy, high‐resolution transmission electron microscopy with X‐ray microanalysis (HRTEM‐EDS), X‐ray photoelectron spectroscopy (XPS) and energy‐dispersive X‐ray fluorescence (EDXRF) were applied for the characterization of the prepared material. The photocatalytic oxidation of benzyl alcohol into benzaldehyde under sun‐imitating Xenon lamp irradiation was applied as a test reaction. The photocatalyst prepared by the sonophotodeposition method showed better results, in terms of alcohol conversion and yield of benzaldehyde, in comparison with the photocatalyst prepared by an ordinary wet‐impregnation method.

Catalytic Properties of Platinum Nanoparticles Obtained in a Single Step Simultaneous Reduction of Pt(IV) Ions and Graphene Oxide

A composite material consisting of metallic platinum nanoparticles and reduced graphene oxide was successfully obtained in microflow reactor. Moreover, subnanometric platinum particles were observed. Reduced graphene oxide plays an important role as a stabilizing agent for platinum nanoparticles. Reduced graphene oxide coverage and platinum particle size as well as size distribution depend mainly on initial concentration of platinum(IV) ions. High level of reduced graphene oxide coverage by platinum nanoparticles (PtNPs) was obtained and is equal to 71%. This in turn effects significantly the mass ratio of reduced graphene oxide to PtNPs which is equal to 49% (w/w). Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) analysis of the obtained materials were performed. Also, catalytic properties of the obtained composite material consisting of PtNPs at reduced graphene oxide surface, towards electrochemical glucose oxidation, were investigated. It was found that the studied materials exhibit high catalytic activity for glucose electro-oxidation process.

Insight into the synthesis procedure of Fe3+/TiO2-based photocatalyst applied in the selective photo-oxidation of benzyl alcohol under sun-imitating lamp

Fe3+/TiO2/zeolite Y photocatalyst synthesized by using sonophotodeposition method was compared with photocatalysts prepared by simple photodeposition and sonodeposition methods in order to clarify the role of light irradiation and ultrasounds while they are used simultaneously. To gain an insight into the mechanism of this method a detailed characterization of the photocatalysts was carried out by means of the following techniques: UV-vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, Mössbauer measurements and photocatalytic test reaction. Basing on the results from these techniques the chemical role of light and mainly mechanical role of ultrasound were observed. The selective photocatalytic oxidation of benzyl alcohol into benzaldehyde in liquid phase was a test reaction verifying the utility of the prepared materials. The best photocatalytic efficiency in this reaction was performed by photocatalyst synthesized using compilation of ultrasound energy with photoexcitation.

Safe-by-Design Ligand-Coated ZnO Nanocrystals Engineered by an Organometallic Approach: Unique Physicochemical Properties and Low Toxicity toward Lung Cells

The unique physicochemical properties and biocompatibility of zinc oxide nanocrystals (ZnO NCs) are strongly dependent on the nanocrystal/ligand interface, which is largely determined by synthetic procedures. Stable ZnO NCs coated with a densely packed shell of 2-(2-methoxyethoxy)acetate ligands, which act as miniPEG prototypes, with average core size and hydrodynamic diameter of 4-5 and about 12 nm, respectively, were prepared by an organometallic self-supporting approach, fully characterized, and used as a model system for biological studies. The ZnO NCs from the one-pot, self-supporting organometallic procedure exhibit unique physicochemical properties such as relatively high quantum yield (up to 28 %), ultralong photoluminescence decay (up to 2.1 μs), and EPR silence under standard conditions. The cytotoxicity of the resulting ZnO NCs toward normal (MRC-5) and cancer (A549) human lung cell lines was tested by MTT assay, which demonstrated that these brightly luminescent, quantum-sized ZnO NCs have a low negative impact on mammalian cell lines. These results substantiate that the self-supporting organometallic approach is a highly promising method to obtain high-quality, nontoxic, ligand-coated ZnO NCs with prospective biomedical applications.

Simonsenia aveniformis sp. nov. (Bacillariophyceae), molecular phylogeny and systematics of the genus, and a new type of canal raphe system.

The genus Simonsenia is reviewed and S. aveniformis described as new for science by light and electron microscopy. The new species originated from estuarine environments in southern Iberia (Atlantic coast) and was isolated into culture. In LM, Simonsenia resembles Nitzschia, with bridges (fibulae) beneath the raphe, which is marginal. It is only electron microscope (EM) examination that reveals the true structure of the raphe system, which consists of a raphe canal raised on a keel (wing), supported by rib like braces (fenestral bars) and tube-like portulae; between the portulae the keel is perforated by open windows (fenestrae). Based on the presence of portulae and a fenestrated keel, Simonsenia has been proposed to be intermediate between Bacillariaceae and Surirellaceae. However, an rbcL phylogeny revealed that Simonsenia belongs firmly in the Bacillariaceae, with which it shares a similar chloroplast arrangement, rather than in the Surirellaceae. Lack of homology between the surirelloid and simonsenioid keels is reflected in subtle differences in the morphology and ontogeny of the portulae and fenestrae. The diversity of Simonsenia has probably been underestimated, particularly in the marine environment.

Diatoms from isolated islands II: Pseudostaurosira diablarum, a new species from a mangrove ecosystem in the Galápagos Islands.

Identifying and describing biodiversity remains fundamental to developing a proper understanding of ecological and biogeographic processes. In this paper, we describe Pseudostaurosira diablarum Seddon & Witkowski sp. nov., a new diatom (Bacillariophyceae) species discovered from Las Diablas wetlands, a brackish water coastal lagoon on the Galápagos Islands. The taxon was observed in both the surface (i.e., extant) and core (i.e., sub-fossil) material from the lagoon, found on shaded mangrove substrata with salinities between 5.2 and 8 g L−1. These observations were confirmed by estimating the salinity tolerances of core samples from the palaeoecological record using a diatom salinity transfer function. We provide light and electron microscope images of P. diablarum sp. nov. Under the light microscope, the best diagnostic features are its lanceolate–elliptical shape, and the striae which are composed of a single row of areolae and do not occur all the way to the apices. Under the scanning/transmission electron microscope, the most distinctive features are the delicate closing plates which are less articulated and branched than in many of the other members of this genus, in addition to the simple, stunted spines which interrupt the striae on the valve margin. The taxon described here constitutes further evidence that the Diablas wetlands are an important site for diatom research, with the potential to provide insights into the processes resulting in the dispersal and evolution of its diatom species.

[Dental plaque as a biofilm - a risk in oral cavity and methods to prevent].

Bacteria living constantly in the oral cavity are in the form of a biofilm. The biofilm formed on a solid base such as the enamel of the teeth, fillings, restorations, orthodontic appliances or obturators is dental plaque. Disturbance of homeostasis of biofilm, excessive growth or increase in the number of acid-forming bacteria leads to the development of the most common diseases of the oral cavity, i.e. dental caries and periodontal disease. The presence of bacterial biofilm on the walls of the root canal or at the top of the root on an outer wall leads to complications and failure in endodontic treatment. The aim of the study was to present the latest information on the occurrence, development and the role of biofilm in the etiopathogenesis of oral diseases and its control. Based on the literature analyzed, it can be concluded that the biofilm, due to its complex structure and numerous mechanisms of bacteria adaptation, is an effective barrier against the traditional agents with antibacterial properties. There are now great hopes for nanotechnology as an innovative method for obtaining new structures of nanometric size and different properties than source materials. The use of antibacterial properties of nano-silver used in dentistry significantly reduces the metabolic activity and the number of colony forming bacteria and lactic acid production in the biofilm.

Characterization of Sc 2 O 3 &CeO 2 -Stabilized ZrO 2 Powders Via Co-Precipitation or Hydrothermal Synthesis

As the presence of Sc₂O₃ and CeO₂ is known to largely enhance the ionic conductivity in the temperature range of 600-800°C, compared with the conventional yttria-stabilized ZrO₂, Sc₂O₃&CeO₂-stabilized ZrO₂ provide its applicability as electrolytes in solid oxide fuel cells. The current study introduces the methodology to synthesize Sc₂O₃&CeO₂-stabilized ZrO₂ powders by using co-precipitation technique or high-temperature hydrothermal reaction, and further describes the structural characterization of the zirconia powders synthesized by the above-mentioned two methods. The co-precipitation technique was found to allow obtaining powders of cubic phase, whereas high-temperature hydrothermal synthesis results in the presence of a monoclinic phase as well. The scanning transmission electron microscope observations also confirm that the size of the synthesized ZrO₂ powders in this study is found to be much smaller than that of commercially available powders.