Репозиторий Университета

© 2021 Elsevier Ltd The functionalization of the bacterial cellulose (BC) surface with a chitosan biopolymer to expand the areas of possible applications of the modified BC is an important scientific task. The creation of such composites in the carbonic acid solutions that were performed in this work has several advantages in terms of being biocompatible and eco-friendly. Quantitative analysis of chitosan content in the composite was conducted by tritium-labeled chitosan radioactivity detection method and this showed three times increased chitosan loading. Different physicochemical methods showed successful incorporation of chitosan into the BC matrix and interaction with it through hydrogen bonds. Microscopy results showed that the chitosan coating with a thickness of around 10 nm was formed in the bulk of BC, covering each microfibril. It was found that the inner specific surface area increased 1.5 times on deposition of chitosan from the solutions in carbonic acid.

© 2020 Elsevier B.V. In this work, we study the effect of RF magnetron oblique angle deposition (OAD) on morphology, structure, and elemental composition of as-deposited and heat-treated Cu containing calcium phosphates. The control over the surface morphology and nano roughness provided by OAD is of great interest as both Mesenchymal Stem Cells and various types of bacteria respond strongly to nanoscale topography. A Cu substituted hydroxyapatite target was used to deposit coatings on the surface of titanium (Ti) and silicon (Si) substrates. The samples were placed at an oblique angle of 80° relative to the surface of the sample holder and in a normal configuration with respect to the flux direction and, therefore, parallel to the target. The dense homogeneous coatings with globular surface features deposited at normal flux incidence (NFI) configuration changed to elliptical, highly oriented structures with the direction dictated by the atomic shadowing effect when the substrate was deposited at an oblique angle. As-deposited thin films were subjected to post-deposition-heat-treatment at 700 °C in an Ar atmosphere. This led to a drastic change in the surface morphology and, namely, lost the directionality of the nanostructures. According to the X-ray diffraction data, the samples deposited obliquely showed preferential growth in the (002) plane and lower internal stress, than samples coated at NFI for both the Si and Ti substrates. The RMS roughness of the films deposited obliquely on Si was twice that of the films deposited at NFI (860 ± 80 pm and 408 ± 60 pm, respectively). However, it was not the case for the Ti substrate, the RMS roughness decreased from 42 ± 4 nm for coatings deposited at normal flux geometry to 33 ± 2 nm for coatings deposited obliquely. The heat-treatment of the samples deposited at 80° resulted in a significant increase in the surface roughness: 8 ± 0.7 nm for Si and 71 ± 4 nm for Ti substrates. The obtained results demonstrate that the oblique angle deposition can be used to fabricate nano-rough surface morphologies.

© 2020 Elsevier B.V. In this work, we study the effect of RF magnetron oblique angle deposition (OAD) on morphology, structure, and elemental composition of as-deposited and heat-treated Cu containing calcium phosphates. The control over the surface morphology and nano roughness provided by OAD is of great interest as both Mesenchymal Stem Cells and various types of bacteria respond strongly to nanoscale topography. A Cu substituted hydroxyapatite target was used to deposit coatings on the surface of titanium (Ti) and silicon (Si) substrates. The samples were placed at an oblique angle of 80° relative to the surface of the sample holder and in a normal configuration with respect to the flux direction and, therefore, parallel to the target. The dense homogeneous coatings with globular surface features deposited at normal flux incidence (NFI) configuration changed to elliptical, highly oriented structures with the direction dictated by the atomic shadowing effect when the substrate was deposited at an oblique angle. As-deposited thin films were subjected to post-deposition-heat-treatment at 700 °C in an Ar atmosphere. This led to a drastic change in the surface morphology and, namely, lost the directionality of the nanostructures. According to the X-ray diffraction data, the samples deposited obliquely showed preferential growth in the (002) plane and lower internal stress, than samples coated at NFI for both the Si and Ti substrates. The RMS roughness of the films deposited obliquely on Si was twice that of the films deposited at NFI (860 ± 80 pm and 408 ± 60 pm, respectively). However, it was not the case for the Ti substrate, the RMS roughness decreased from 42 ± 4 nm for coatings deposited at normal flux geometry to 33 ± 2 nm for coatings deposited obliquely. The heat-treatment of the samples deposited at 80° resulted in a significant increase in the surface roughness: 8 ± 0.7 nm for Si and 71 ± 4 nm for Ti substrates. The obtained results demonstrate that the oblique angle deposition can be used to fabricate nano-rough surface morphologies.

© 2018 WILEY-VCH Verlag GmbH  &  Co. KGaA, Weinheim Nature has long inspired scientists and engineers. As one ubiquitous example of this, nature has provided all with several clever methods to absorb, repel, and/or allow both sunlight and water to pass through surfaces. Moth's eyes (highly antireflective) and lotus leaves (highly hydrophobic and self-cleaning) represent durable natural surfaces which exhibit nearly ideal physical and optical properties. Man-made transparent surfaces must also be able to cope with water and dust while reaching the maximum possible light transmission for solar collectors, displays, and other optical devices. To explore the link between these – particularly for transparent surfaces – this review puts the physics, progress, and limitations of synthetic materials in context with natural materials. This perspective reveals that there is still much more to learn (and implement) if it is hoped to match the multifunctionality and resilience of natural materials.