Polymer-Templated Durable and Hydrophobic Nanostructures for Hydrogen Gas Sensing Applications

A simple and hands-on one-step process has been implemented to fabricate polymer-templated hydrophobic nanostructures as hydrogen gas sensing platforms. Topographic measurements have confirmed irregular hills and dips of various dimensions that are responsible for creating air bubble pockets that satisfy the Cassie–Baxter state of hydrophobicity. High-resolution field-emission scanning electron microscopy (FESEM) has revealed double-layer structures consisting of fine microscopic flower-like structures of nanoscale petals on the top of base nanostructures. Wetting contact angle (WCA) measurements further revealed the contact angle to be ~142.0° ± 10.0°. Such hydrophobic nanostructures were expected to provide a platform for gas-sensing materials of a higher surface area. From this direction, a very thin layer of palladium, ca. 100 nm of thickness, was sputtered. Thereafter, further topographic and WCA measurements were carried out. FESEM micrographs revealed that microscopic flower-like structures of nanoscale petals remained intact. A sessile drop test reconfirmed a WCA of as high as ~130.0° ± 10.0°. Due to the inherent features of hydrophobic nanostructures, a wider surface area was expected that can be useful for higher target gas adsorption sites. In this context, a customized sensing facility was set up, and H2 gas sensing performance was carried out. The surface nanostructures were found to be very stable and durable over the course of a year and beyond. A polymer-based hydrophobic gas-sensing platform as investigated in this study will play a dual role in hydrophobicity as well as superior gas-sensing characteristics.

Impregnation of Wood with Waste Engine Oil to Increase Water- and Bio-Resistance

Impregnation is a common method of protecting wood from external influences. This study proposes the use of spent engine oil as an impregnating composition for modifying birch wood to make it resistant to biological degradation and water. The indicators of water resistance and dimensional stability of wood such as wetting contact angle, thermogravimetric analysis, Fourier transform infrared spectroscopy (FTIR), and biodegradation tests have been determined. It has been found that treatment with spent engine oil significantly increases the dimensional stability (56.8% and 45.7% in tangential and radial directions) and water-resistant indicators of wood. Thermogravimetric analysis has showed that the curves for the impregnated specimens were different from the control group and had two sharp peaks at 302 and 357 °C. However, FTIR indicated that no clear chemical reactions occur between spent engine oil and wood. A study on wood resistance to biological degradation has showed a significant increase in resistance against brown rot (Poria placenta fungi) in the treated specimens, in contrast to the control group. Thus, impregnation of wood with spent engine oil makes it possible to increase wood resistance to water and biological degradation.

New Approaches to Increasing the Superhydrophobicity of Coatings Based on ZnO and TiO2

The work presented is devoted to new approaches to increasing the superhydrophobic properties of coatings based on zinc oxide (ZnO) and titanium dioxide (TiO2). There is an innovation in the use of inorganic coatings with a non-polar structure, high melting point, and good adhesion to ZnO, in contrast to the traditionally used polymer coatings with low performance characteristics. The maximum superhydrophobicity of the ZnO surface (contact angle of 173°) is achieved after coating with a layer of hematite (Fe2O3). The reason for the abnormally high hydrophobicity is a combination of factors: minimization of the area of contact with water (Cassie state) and the specific microstructure of a coating with a layer of non-polar Fe2O3. It was shown that the coating of ZnO structures with bimodal roughness with a gold (Au) layer that is 60-nm thick leads to an increase in the wetting contact angle from 145° to 168°. For clean surfaces of Au and hematite Fe2O3 films, the contact angle wets at no more than 70°. In the case of titanium oxide coatings, what is new lies in the method of controlled synthesis of a coating with a given crystal structure and a level of doping with nitrogen using plasma technologies. It has been shown that the use of nitrogen plasma in an open atmosphere with different compositions (molecular, atomic) makes it possible to obtain both a hydrophilic (contact angle of 73°) and a highly hydrophobic surface (contact angle of 150°).

Influence of plasma treatment on SiO2/Si and Si3N4/Si substrates for large-scale transfer of graphene

One of the limiting factors of graphene integration into electronic, photonic, or sensing devices is the unavailability of large-scale graphene directly grown on the isolators. Therefore, it is necessary to transfer graphene from the donor growth wafers onto the isolating target wafers. In the present research, graphene was transferred from the chemical vapor deposited 200 mm Germanium/Silicon (Ge/Si) wafers onto isolating (SiO2/Si and Si3N4/Si) wafers by electrochemical delamination procedure, employing poly(methylmethacrylate) as an intermediate support layer. In order to influence the adhesion properties of graphene, the wettability properties of the target substrates were investigated in this study. To increase the adhesion of the graphene on the isolating surfaces, they were pre-treated with oxygen plasma prior the transfer process of graphene. The wetting contact angle measurements revealed the increase of the hydrophilicity after surface interaction with oxygen plasma, leading to improved adhesion of the graphene on 200 mm target wafers and possible proof-of-concept development of graphene-based devices in standard Si technologies.

Wettability of organic-rich source rocks: case study on Bazhenov Formation (Abalak-Bazhenov group)

In this work, we have investigated the wettability of Bazhenov Formation rock samples using a nuclear magnetic resonance (NMR), the methods of vapor adsorption, and wetting contact angle. We have conducted the petrographic description of rocks using ultra-thin sections and scanning electron microscopy (SEM). In addition, we used data on the organic content (TOC) obtained by the Rock-Eval method and the results of lithological typing on thin sections for detailed analysis of NMR and contact angle methods results. Thus, for target rock, the groups with a similar rock wettability were highlighted by the lithological description of thin sections. The calculation of the wetting angle provided an initial assessment of the surface wettability of the rock and made it possible to establish the relationship between the wetting angle and the TOC, which is relevant for rocks of the Abalak-Bazhenov group. The NMR method described the core plug wettability proved to be less sensitive to the rock lithotype and organic matter (OM) texture in the rock and, therefore, used for the integral characterization of core plugs. Correlations of calculated wetting angle and adsorption wettability index vs. TOC and OM texture illustrated the dependence of rock wettability behavior on both the lithological specifics and the OM properties.

Biosynthesis and Characteristics of Polyhydroxyalkanoates. 1. Polyhydroxybutyrates of Azotobacter vinelandii N-15

The biosynthesis of cellular polymers of Azotobacter vinelandii N-15 strain using molasses as a carbon source has been optimized. The highest yield of polymer (25.8 % of cell mass) was obtained on a nutrient medium with a molasses concentration of 50 g/l. Using TL-chromatography and IR-spectroscopy the obtained product was identified as polyhydroxybutyrate (PHB), and its properties were investigated. The wetting contact angle was used to characterize the biopolymer film surface properties. According to the results of thermal and thermomechanical studies, it was found that the obtained РHB is characterized by a high thermal stability and heat resistance: the melting point is 462 K; deep destruction and thermooxidative processes begin at the temperatures above 567 K.

Crystal phase engineering of self-catalyzed GaAs nanowires using a RHEED diagram

It is well known that the crystalline structure of the III–V nanowires (NWs) is mainly controlled by the wetting contact angle of the catalyst droplet which can be tuned by the III and V flux.

Separating Wickability and Wetting Effects During Water Droplet Evaporation on Superhydrophilic Nanoporous Surfaces

The dynamic behavior of impinging water droplets is studied in the context of varying surface wettability and wickability on smooth and nanostructured superhydrophilic surfaces. This study distinguishes the separate effects of wetting (contact angle), wickability, and inertia on the spreading and vaporization of water droplets deposited on nanoporous surfaces by considering experimental results in tandem with axisymmetric, volume of fluid (VOF) simulations of droplet spreading. High speed videos were obtained for water droplets spreading on nanoporous surfaces which exhibit very low (< 15°) contact angle and high wickability. In this study, the effect of wickability was assessed by comparing the experimental results, which include the low contact angle and high wickability effects, to predictions of the VOF model, which include only the ultralow contact angle. While a droplet touched to the nanostructured surface demonstrates spreading driven by wicking, droplets which hit the surface with a non-zero impact velocity demonstrate spreading characteristics similar to the smooth surface, which are driven by inertia and ultra-low contact angle. The presence of the nanoporous layer impacts the equilibrium position of the contact line and the final spread radius changes with impact velocity on the nanostructured surface. These results provide fundamental input for modeling of spray cooling systems with nanostructured surfaces.

Functionalization of Polyethylene (PE) and Polypropylene (PP) Material Using Chitosan Nanoparticles with Incorporated Resveratrol as Potential Active Packaging

The present paper reports a novel method to improve the properties of polyethylene (PE) and polypropylene (PP) polymer foils suitable for applications in food packaging. It relates to the adsorption of chitosan-colloidal systems onto untreated and oxygen plasma-treated foil surfaces. It is hypothesized that the first coated layer of chitosan macromolecular solution enables excellent antibacterial properties, while the second (uppermost) layer contains a network of polyphenol resveratrol, embedded into chitosan nanoparticles, which enables antioxidant and antimicrobial properties simultaneously. X-ray photon spectroscopy (XPS) and infrared spectroscopy (FTIR) showed successful binding of both coatings onto foils as confirmed by gravimetric method. In addition, both attached layers (chitosan macromolecular solution and dispersion of chitosan nanoparticles with incorporated resveratrol) onto foils reduced oxygen permeability and wetting contact angle of foils; the latter indicates good anti-fog foil properties. Reduction of both oxygen permeability and wetting contact angle is more pronounced when foils are previously activated by O2 plasma. Moreover, oxygen plasma treatment improves stability and adhesion of chitosan structured adsorbates onto PP and PE foils. Foils also exhibit over 90% reduction of Staphylococcus aureus and over 77% reduction of Escherichia coli as compared to untreated foils and increase antioxidant activity for over a factor of 10. The present method may be useful in different packaging applications such as food (meat, vegetables, dairy, and bakery products) and pharmaceutical packaging, where such properties of foils are desired.

Effective complex hydrophobizators for self-cleaning facade materials

In the work presented here, we present the research results of the effect of self-cleaning of surfaces. The methods of its achievement such as photocatalytic and the method of hydrophobization are considered. The known methods for determining the contact angle of wetting are used. An installation for generating a low-temperature nonequilibrium plasma was used to modify a fine aggregate. The contact angles of wetting obtained as a result of the use of various formulations of hydrophobizing suspensions are determined experimentally. A modification of the quartz filling matter was also carried out. Experiments have confirmed the technical effectiveness of hydrophobisers and the enhancement of their properties when dispersed fillers are used. Even higher values of wetting contact angle were achieved using a plasma-modified filling matter.