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Spectroscopic ellipsometry of interfacial phase transitions in fluid metallic systems: KxKCl1-x and Ga1-xBix [online]

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ISBN: 3937300082 Year: DOI: 10.5445/KSP/812004 Language: ENGLISH
Publisher: KIT Scientific Publishing
Subject: Chemistry (General)
Added to DOAB on : 2019-07-30 20:01:59

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Abstract

The investigation of the interfacial phase transitions in fluid systems with short-range intermetallic interactions are of great interest. The phenomena were studied in two systems exhibiting a liquid-liquid miscibility gap: at the fluid/wall interface in fluid KxKCl1-x and at the fluid/vacuum interface of the Ga1 xBix alloys. To characterize the interfacial changes of the ultra thin films (composition, thickness and their evolution with time) the spectroscopic ellipsometry was performed over a wide spectral range. Whereas in the experiments on KxKCl1-x an existing ellipsometer could be used, a completely new UHV-apparatus including the in-situ phase modulation ellipsometer had to be developed for Ga1 xBix alloys. For the KxKCl1-x system new results on complete wetting at solid-liquid coexistence as well as in the homogenous liquid phase (prewetting) are presented. The spectra show the typical F center absorption which indicates that the film is a salt-rich phase. The thickness strongly increases approaching the monotectic from 30 to 440 nm, which is in agreement with the tetra point wetting scenario. For this interpretation a quantitative description of the excess Gibbs energy has been developed. For the Ga1 xBix system the results on complete wetting, surface freezing and oscillatory interfacial instabilities are presented. The high-precision spectra have been recorded approaching the liquid-liquid miscibility. These spectra have been modeled using a Ga-Bi effective medium approximation for the substrate covered by a film of liquid Bi. The measurements give evidence of tetra point wetting in the Ga-Bi system. First ellipsometric study of the surface freezing in Ga-Bi has been performed. Within the miscibility gap a very interesting effect of surface and bulk oscillatory instability was observed. The details of this process at present are not well understood, but a qualitative description is given.

Molecular Magnets

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ISBN: 9783038977100 Year: Pages: 166 DOI: 10.3390/books978-3-03897-711-7 Language: eng
Publisher: MDPI - Multidisciplinary Digital Publishing Institute
Subject: Science (General) --- Chemistry (General)
Added to DOAB on : 2019-03-21 14:08:22
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Molecular magnets show many properties not met in conventional metallic magnetic materials, i.e. low density, transparency to electromagnetic radiation, sensitivity to external stimuli such as light, pressure, temperature, chemical modification or magnetic/electric fields, and others. They can serve as “functional” materials in sensors of different types or be applied in high-density magnetic storage or nanoscale devices. Research into molecule-based materials became more intense at the end of the 20th century and is now an important branch of modern science. The articles in this Special Issue, written by physicists and chemists, reflect the current work on molecular magnets being carried out in several research centers. Theoretical papers in the issue concern the influence of spin anisotropy in the low dimensional lattice of the resulting type of magnet, as well as thermodynamics and magnetic excitations in spin trimers. The impact of external pressure on structural and magnetic properties and its underlying mechanisms is described using the example of Prussian blue analogue data. The other functionality discussed is the magnetocaloric effect, investigated in coordination polymers and high spin clusters. In this issue, new molecular magnets are presented: (i) ferromagnetic high-spin [Mn6] single-molecule magnets, (ii) solvatomagnetic compounds changing their structure and magnetism dependent on water content, and (iii) a family of purely organic magnetic materials. Finally, an advanced calorimetric study of anisotropy in magnetic molecular superconductors is reviewed.

Advances in Chitin/Chitosan Characterization and Applications

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ISBN: 9783038978022 9783038978039 Year: Pages: 414 DOI: 10.3390/books978-3-03897-803-9 Language: eng
Publisher: MDPI - Multidisciplinary Digital Publishing Institute
Subject: Science (General) --- Biology --- Biochemistry
Added to DOAB on : 2019-04-25 16:37:17
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Functional advanced biopolymers have received far less attention than renewable biomass (cellulose, rubber, etc.) used for energy production. Among the most advanced biopolymers known is chitosan. The term chitosan refers to a family of polysaccharides obtained by partial de-N-acetylation from chitin, one of the most abundant renewable resources in the biosphere. Chitosan has been firmly established as having unique material properties as well as biological activities. Either in its native form or as a chemical derivative, chitosan is amenable to being processed—typically under mild conditions—into soft materials such as hydrogels, colloidal nanoparticles, or nanofibers. Given its multiple biological properties, including biodegradability, antimicrobial effects, gene transfectability, and metal adsorption—to name but a few—chitosan is regarded as a widely versatile building block in various sectors (e.g., agriculture, food, cosmetics, pharmacy) and for various applications (medical devices, metal adsorption, catalysis, etc.). This Special Issue presents an updated account addressing some of the major applications, including also chemical and enzymatic modifications of oligos and polymers. A better understanding of the properties that underpin the use of chitin and chitosan in different fields is key for boosting their more extensive industrial utilization, as well as to aid regulatory agencies in establishing specifications, guidelines, and standards for the different types of products and applications.

Keywords

aerogels --- chitosan --- ionic liquids --- ionogels --- zinc–chitosan complexes --- characterization --- bio-sorbent --- phosphate --- adsorption --- mechanism --- thermodynamic --- chitosan --- hydrogel --- phase transition --- gelation mechanism --- chitosan --- defense responses --- fruits --- nanoparticles --- plant growth --- pesticides --- Boron --- chitosan --- iron(III) hydroxide --- neodymium --- sorption --- chitin --- chitosan --- chitosan derivative --- chitin derivative --- oral care --- skin care --- hear care --- marine resources --- over-the counter-drug --- polymer carrier --- chitin --- chitosan --- nanostructured biomaterial --- polymer --- self-masking nanosphere lithography --- cicada --- chitosan --- self-assembled --- polyelectrolyte complex --- nanoparticle --- drug delivery --- Citrobacter --- biosynthesis --- bioflocculant --- chitosan --- metabolic pathway --- PEO/chitosan blend --- swelling --- mechanical properties --- wet and dried states --- chitosan --- biological activity --- medical applications --- chitosan --- PCL --- strontium --- scaffolds --- craniofacial engineering --- chitin --- chitosan --- derivatization --- controlled functionalization --- click chemistry --- graft copolymer --- cyclodextrin --- dendrimer --- ionic liquids --- chitin deacetylases --- chitosan --- chitooligosaccharides --- carbohydrate esterases --- structure --- substrate specificity --- deacetylation pattern --- binary --- chitosan --- desorption --- iron --- lead --- mercury --- salt effects --- single --- sorption competition --- chitosan supported copper --- heterogeneous catalyst --- organosilicon compound --- easily recyclable --- chitosan --- papermaking --- wet-end --- coating --- wastewater --- ionic cross-linking --- eco-friendly formulations --- thermal transition sol-gel --- drug delivery systems --- MTDSC --- DSC --- gene delivery --- non-viral vectors --- chitosan structure --- pDNA --- siRNA --- TEOS --- methylene blue --- chitosan --- modelling --- cross-linking --- interpenetrating --- XRD --- FTIR

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