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1.
Determination of iron in natural waters using DGT technique coupled to phototermal beam deflection spectroscopy
Hanna Budasheva, Arne Bratkič, Dorota Korte, Mladen Franko, 2018, published scientific conference contribution abstract

Found in: ključnih besedah
Summary of found: ...Beam deflection spectroscopy, diffusive gradients in thin-films, iron species, photothermal techniques,...
Keywords: Beam deflection spectroscopy, diffusive gradients in thin-films, iron species, photothermal techniques, natural waters.
Published: 09.11.2018; Views: 2624; Downloads: 0
.pdf Fulltext (40,53 KB)

2.
Determination of bioavailable Fe redox fractions of sediment pore waters by DGT passive sampling and BDS detection
Mladen Franko, Arne Bratkič, Dorota Korte, Hanna Budasheva, 2019, published scientific conference contribution abstract

Abstract: The bioavailability and toxicity of contaminants in sediments to benthic organisms depend on the speciation of the contaminant [1]. The level of iron supply to sediments creates contrasting chemical pathways, each producing distinctive mineral assemblag- es. Reliable measurement of Fe redox species (Fe2+ and Fe3+) in sediments is essential for studies of pollutants or trace-element cycling. This is, however, a difficult task, because the distribution of chemical species often changes during sampling and storage. In this work the Diffusive Gradients in Thin-films technique (DGT) is investigated as a passive sampling approach used in combination with photothermal beam deflection spectroscopy (BDS) as a detection method for determination of labile Fe-redox species in sediments and natural waters. DGT offers the advantage of pre-concentration of labile (i.e. bioavailable) Fe species from the total dissolved Fe pool in sediment pore waters [2]. The advantage of using BDS [3-4] is also in avoiding contamination by using additional steps as extraction or pre-concentration. Furthermore, combined DGT-BDS provides 2D information about distribution of Fe2+ and the total Fe content in the resin hydrogels [5]. The goal of this research is to show the repeatability of this technique for determining trace amounts of Fe redox species in environmental samples.
Found in: ključnih besedah
Summary of found: ...during sampling and storage. In this work the Diffusive Gradients in Thin-films technique (DGT) is investigated...
Keywords: beam deflection spectrometry, diffusive gradients in thin-films, iron species
Published: 16.07.2019; Views: 2305; Downloads: 0
.pdf Fulltext (29,60 MB)

3.
Effect of bead size in Chelex-based resin hydrogels in DGT on detection of Fe redox species by beam deflection spectroscopy
Dorota Korte, Arne Bratkič, Hanna Budasheva, Mladen Franko, 2019, published scientific conference contribution abstract

Found in: ključnih besedah
Summary of found: ... Diffusive Gradients in Thin Films, Beam Deflection Spectrometry,...
Keywords: Diffusive Gradients in Thin Films, Beam Deflection Spectrometry, iron species, resin hydrogels
Published: 25.09.2019; Views: 2185; Downloads: 0
.pdf Fulltext (1,28 MB)

4.
Developing DGT technique for determination of iron redox species by photothermal beam deflection spectrometry
Yue Gao, Dorota Korte, Chang Zhou, Arne Bratkič, Hanna Budasheva, Mladen Franko, Bruno Delille, 2019, published scientific conference contribution abstract

Found in: ključnih besedah
Summary of found: ... Diffusive Gradients in Thin Films, Beam Deflection Spectrometry,...
Keywords: Diffusive Gradients in Thin Films, Beam Deflection Spectrometry, iron redox species
Published: 25.09.2019; Views: 2220; Downloads: 0
.pdf Fulltext (1,28 MB)

5.
Determination of Fe(III) and Fe(II) in natural waters using passive DGT samplers and non-destructive BDS analysis
Arne Bratkič, Dorota Korte, Hanna Budasheva, Mladen Franko, 2019, published scientific conference contribution abstract

Found in: ključnih besedah
Summary of found: ...Beam Deflection Spectrometry, iron species, Diffusive Gradients in Thin-films, frequency scanning...
Keywords: Beam Deflection Spectrometry, iron species, Diffusive Gradients in Thin-films, frequency scanning
Published: 30.09.2019; Views: 2294; Downloads: 0
.pdf Fulltext (19,45 MB)

6.
Towards a novel method for iron species determination in Antarctic sea ice
Hanna Budasheva, Arne Bratkič, Dorota Korte, Mladen Franko, 2021, published scientific conference contribution abstract

Abstract: Sea-ice borne iron has been found to be an important factor controlling Southern Ocean phytoplankton growth [1]. Knowing the amount and chemical speciation of its labile fraction in sea ice would advance our understanding of the involved processes. Unfortunately, it is rather difficult to perform their measurement because of limited access to the Antarctic. Thus there is a strong need for the development of a quick, simple and reliable technique for determination of iron and its speciation in sea-ice that ensures also low enough limits of detection. Recently, diffusive gradients in thin films (DGT) have been widely used as passive samplers for collecting time-averaged data on the concentrations of transition metals in different media [2]. DGTs are further coupled to an analytical technique that in case of detecting metals in passive sampler films primarily requires their extraction [3], which may potentially lead to changes of the metal specification. In the present study, the beam deflection spectrometry (BDS) is coupled to DGT and used to determine the average concentration of iron in the sea ice samples collected at the Davis Station in the Antarctic. Such a combined technique has been already successfully applied for detecting labile iron species in freshwater sediments [4]. The obtained BDS data were validated by thermal lens spectrometry (TLS) and UV-Vis spectrophotometry (SPEC). The distribution of iron species over a given ice surface area using the DGT-BDS technique revealed total iron concentrations in the range of 0.6 – 5.3 μgL-1, whereas the Fe2+ content was found to be in the range of 0.1 – 1.5 μgL-1. The range taking into account all of the measurement points (5×4), the precision of a single measured point is 0.2 μgL-1. The calculated 24 h-average concentration of total Fe labile species in the ice by using BDS is 2.3 ± 0.5 μgL-1, which coincides with data obtained by SPEC (2.5 ± 0.4 μgL-1) and TLS (2.39 ± 0.02 μgL-1). Our results indicate that it is possible to develop a robust, contamination-resilient detection method for measuring the labile iron species concentration in the sea ice. In opposite to TLS and SPEC, BDS-DGT provides reliable information not only about the speciation of iron but also about their distribution on the ice surface.
Found in: ključnih besedah
Summary of found: ...also low enough limits of detection. Recently, diffusive gradients in thin films (DGT) have been...
Keywords: beam deflection spectrometry, diffusive gradients, thin films, iron species, photothermal techniques, Antarctic sea ice
Published: 30.11.2021; Views: 922; Downloads: 0
.pdf Fulltext (216,61 KB)
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7.
NONDESTRUCTIVE THERMAL, OPTICAL, CHEMICAL AND STRUCTURAL CHARACTERIZATION OF ADVANCED MATERIALS BY OPTOTHERMAL TECHNIQUES
Hanna Budasheva, doctoral dissertation

Abstract: Advanced materials are promising ones in application in fields where it is necessary to decrease energy consumption and ensure better performance at a lower cost. They are materials, which have enhanced properties compared to conventional materials in the field of their applications.1 The huge group of them contributes significantly to every aspect of our lives. Among them, chosen for the present study, are resins for passive sampling of iron species in natural water and sediments, anticorrosive coatings, and multilayered polysaccharide aerogels for medical applications. The composition and structure of each material determine its chemical, mechanical and physical properties, consequently their performance.2 The ability to use advanced materials in areas where their impact will be significant is largely dependent on the ability to precisely determine their characteristics to identify their properties that are either unique or has a better value. Therefore, the development of new methods or improvement of already known ones will make a great contribution to the development of the fields of application of the selected materials. The present study is focused on the examination of the chosen materials by determining their optical, chemical, thermal and structural properties for applying them further in the desired applications. To provide the needed characterization, optothermal techniques such as optothermal beam deflection spectrometry (BDS) and thermal lens spectrometry (TLS) are developed and applied. This dissertation is composed of the following chapters: introduction, theoretical background, optothermal techniques, research goal, part I (gels for passive sampling of iron species in natural water and sediments), part II (anticorrosive coatings), part II (polysaccharide aerogels), references. The core of this dissertation is presented in chapters 5 to 7. Each of the chapters separately covers the information about a selected group of advanced materials, including the sections describing sample preparation, developing the required characterization method, results, and conclusion. The connection link of these chapters is the study of the diffusion process of iron into different types of binding gels in passive samplers; external composites through the anticorrosive layers; drugs into the surrounding during the drug delivery process. In Part I, the BDS method for the study was chosen, it was optimized, and a detailed protocol was developed for the determination of iron in passive sampler gels. The iron residues in the initial solutions were checked by a suitably tuned TLS method. The developed technique was applied to get the iron species distribution in the gel samples deposited in the sediments in the Vrtojbica River. The method was applied to the gels applied on ice from Antarctica in order to obtain the iron species distribution on its surface as well. The obtained results were validated using the TLS, UV-Vis and ICP-MS methods. The chapter contains the analysis of the Fe diffusion depth into the resin sampler, which is presented for the first time. The information is obtained by using the mathematical model and applying it to the obtained practical results by frequency scanning of the gels. The crucial information about the thermal properties of their layers containing Fe-ions from the fitting procedure was extracted. On the basis of these results, information about the diffusion depth of Fe inside the gels was obtained, which has not been previously described in the literature. In Part II, the porosity in the anticorrosion coatings on the basis of their thermal parameters was determined. For the first time, the opened porosity was extracted from the total one. The analysis of Si/Zr-based hybrid sol-gel coatings has shown that the addition of cerium salts into the sol-gel matrix produces changes in its physical, chemical and corrosion properties. And it was found that the sample with the biggest amount of incorporated zirconium and loaded with cerium has the lowest values of porosity and, hence, the best barrier properties of the coating. The obtained thermal parameters of the Si/Zr-based hybrid sol-gel coatings by BDS were validated by the use of the photothermal radiometry method. On the other hand, the analysis of siloxane methacrylate coating has shown that the sol-gel hybrid methodology offers an important route for modification of thermal properties by a combination of inorganic to organic contents where the former than as an integral part of the coating network affects the thermal properties without the need for introducing fillers or nanoparticles. In Part III, the multilayered structure of the samples, containing hyaluronic acid, amoxicillin and fucoidan layers deposited on stainless support has been analyzed by the use of the BDS technique. The thermal parameters of each layer were determined, as well as their thickness. The results revealed the diffusion between neighboring layers and followed changes in the properties of the whole sample, which is reflected in its thermal properties. Such data for multilayered materials, which potentially can be used for drug delivery systems, are presented for the first time. Presented results indicated the ability of the BDS system for the chemical characterisation of the solid materials, the detection of their thermal parameters; investigation of total, opened and closed porosity; determining the thickness of layers in multilayered structures. The TLS method served as the validating one for the purpose of getting comprehensive information in liquid samples about their chemical composition. In summary, this dissertation explores alternative ways to apply optothermal methods to various areas of advanced materials to characterize them in order to improve their initial properties.
Found in: ključnih besedah
Summary of found: ...optothermal beam deflection spectrometry, thermal lens spectrometry, diffusive gradients in thin films, iron species, anticorrosive...
Keywords: optothermal beam deflection spectrometry, thermal lens spectrometry, diffusive gradients in thin films, iron species, anticorrosive layers, porosity, polysaccharide aerogels, multilayered structures
Published: 29.08.2022; Views: 314; Downloads: 23
.pdf Fulltext (5,46 MB)

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