Determination Of Contact Angle Research Articles

Zwitterionic Cysteine Drug Coating Influence in Functionalization of Implantable Ti50Zr Alloy for Antibacterial, Biocompatibility and Stability Properties.

The present paper aims atincreasing the bioperformance of implantable Ti50Zr alloy using zwitterionic cysteine drug coating. Aspects such as stability, biocompatibility, and antibacterial effects were investigated with the help of various methods such as infrared spectroscopy (FT-IR), scanning electronic microscopy (SEM), electrochemical methods, contact angle determinations and cell response. The experimental data of zwitterionic cysteine coating indicate the existence of a hydration layer due to hydrophilic groups evidenced in FT-IR which is responsible for the decrease of contact angle and antibacterial capabilities. The electrochemical stability was evaluatedbased on Tafel plots and electrochemical impedance spectroscopy (EIS). The cell response to cysteine was determined with gingival fibroblasts measuring lactate dehydrogenase (LDH) activity, concentrations of nitric oxide (NO) and intracellular level of reactive oxygen species (ROS). All experimental results supported the increase of stability and better cells response of implantable Ti50Zr alloy coated with zwitterionic cysteine drug. The antibacterial index was measured against Staphylococcus aureus and Escherichia coli. It was demonstrated that the coating enhanced the production of intracellular ROS in time, which subsequently caused a significant increase in antibacterial index.

Removal of coke powders in coking diesel distillate using recyclable chitosan-grafted Fe3O4 magnetic nanoparticles

Coking is an important process for heavy or residual oil treatment as coke powders carried by coking diesel distillate (CDD) could seriously affect the steady operation of downstream devices. In this work, chitosan (CS)-grafted Fe3O4 was used to prepare magnetic nanoparticles (MNPs), and characterization analyses, including X-ray diffractometry (XRD), Fourier-transform infrared spectrometry (FTIR), transmission electron microscopy (TEM), dynamic light scattering analysis (DLS), thermogravimetric analysis (TG), vibrating sample magnetometry (VSM), and water contact angle determination, were performed on the coking powders and MNPs. The mechanism of coke powder removal was determined through an experimental study on coke powder removal in CDD by using the MNPs. Grafting CS onto oleic acid (OA)-modified Fe3O4 yields Fe3O4@OA-CS nanoparticles with superparamagnetism, and the CS grafting quantity is an important factor influencing whether Fe3O4@OA-CS has high efficiency for coke powder removal. CS can enhance the hydrophilicity of Fe3O4@OA (water contact angle = 112°), and Fe3O4@OA-CS with some hydrophobicity (water contact angle = 105°) could satisfactorily remove coke powders (removal rate ≥96%) from the distillate. In addition, Fe3O4@OA-CS could be recycled and reused using light petroleum (LP). The new coke removal process involves the following principles: spatial distribution of CDD is taking coke powders as the core, coating with non-hydrocarbon compounds (polar layer), and dispersing into arenes and alkanes (non-polar layer). Fe3O4@OA-CS may show interfacial activity and could be directionally arranged on the interface between the polar and non-polar layers. Thus, non-hydrocarbon compounds may come into direct contact with the Fe3O4@OA-CS nanoparticles. When rinsed with LP, Fe3O4@OA-CS can enter the LP phase, together with these non-hydrocarbon compounds, and be effectively separated from the coke powders.

Synthesis and characterization of fluoro-silicone polyacrylate latex emulsified with novel green surfactants

The novel fluoro-silicone polyacrylate latex was successfully synthesized in the presence of a novel green mixed emulsifier of β-cyclodextrin ( β-CD) and sodium lauroyl glutamate (SLG) by semi-continuous seeded emulsion polymerization, which was initiated with potassium persulphate. Methyl methacrylate (MMA) and butyl acrylate (BA) were used as the main monomers, while hexafluorobutyl methacrylate (HFMA) and vinyltriethoxysilane (VTES) were used as the functional monomers. The resultant latex and its film were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry and contact angle determinator, respectively. The optimum conditions of preparing the fluoro-silicone polyacrylate latex are as follows: the amount of compound emulsifiers are 7.0%; β-CD: SLG = 1:2; the amount of initiator is 0.7%; the appropriate proportion of main monomer of MMA: BA = 1:1; and the amounts of HFMA and VTES are 6.0% and 4.0%, respectively. In this case, the resultant latex has high conversion rate, low gel rate and good stability. Results showed that both thermal stability and hydrophobic property of the latex are improved with the incorporation of a small amount of HFMA and VTES.

Three-dimensional mesoporous silica networks with improved diffusion and interference-abating properties for electrochemical sensing

One of the key issues of electrochemical sensing in complex matrices is the presence of interferents which can foul the electrode and block the access to the active surface. A possible strategy to promote selectivity is based on the use of interference-abating layers, which can however significantly hamper the sensor response by limiting the analyte diffusion. Here, hard template mesoporous silica films with pore size in the 20–75 nm range and tuneable thickness, deposited onto conductive ITO substrates, were prepared and studied from the physicochemical (FE-SEM, SEM, AFM, water contact angle determinations, UV–vis spectroscopy) and the electrochemical (CV, EIS) point of view. Pore size dependent diffusion phenomena were observed, giving rise to enhanced electrochemical performance for 20–40 nm pores despite the presence of an insulating layer at the electrode surface. The tuneable morphology of the samples together with the wetting properties were found to be pivotal for the understanding of the electrochemical behaviour. The best performance was obtained for the samples with the 20-nm porosity and the highest film thickness. These results were also confirmed by EIS data elaboration, able to provide quantitative measurements about the mass transport resistance of the pores. The modified electrodes were tested for dopamine detection in the presence of a large interfering protein (mucin). The porous and charged network allowed the interfering macromolecule to be excluded, preventing the electrode biofouling and enhancing the performances of the device towards dopamine detection.

Graphene oxide/PVDF VIPS membranes for switchable, versatile and gravity-driven separation of oil and water

In what follows, we incorporated graphene oxide (GO) into poly(vinylidene fluoride) (PVDF) membranes prepared by vapor-induced phase separation (VIPS), in order to achieve gravity-driven separation of versatile water-in-oil (W/O) and oil-in-water (O/W) emulsions. Membranes were first fully characterize to evidence the presence of GO at the interface, using XPS, FT-IR, Raman, and XRD spectroscopy, while SEM permitted to describe the porous structure of the microfiltration (MF) membranes. An in-depth study of the wettability of the membranes was carried out through the determination of water contact angles in air and oil, and oil contact angles in air and water, using 4 different oils including toluene, hexane, diesel and soybean oil. It was found that GO did not significantly affect the wettability of the membranes. However, gravity-driven filtration tests performed after pre-wetting the membranes with the dispersing phase forming the emulsion at play revealed that GO could accelerate 8–10 times the separation of both O/W and W/O emulsions. The nature of the dispersing phase probably dictates the selective wetting of the functional groups of the GO particles, which in turn favors the permeation of the dispersing phase and accelerates the whole separation. Besides, GO strengthens the interactions with the wetting liquid contributing to totally eliminate air pockets, which prevents the dispersed phase in complex emulsions (involving diesel or soybean oil) to permeate through the pores, and so, improves the separation efficiency despite larger pores.

The influence of alumina particle modification on the adhesion of the polyacrylate matrix composite films and the metal substrate

ABSTRACTAdhesion behavior between the composite films, consisting of UV cured Bis-GMA (Bisphenol A glycidylmethacrylate)/TEGDMA (triethylene glycol dimethacrylate) as a matrix and the ferrous oxide doped alumina particles, Al2O3 Fe, modified with 3-aminopropyl)tri – methoxysilane (AM) and methyl esters of linseed oil fatty acids (biodiesel – BD) used as a reinforcement, and metallic surface was investigated in this study. Al2O3 Fe-BD particles showed pronounced hydrophobicity and hydrolytic stability of alumina surface. Adhesive and mechanical properties of prepared composites, containing 0.5, 1.5 and 3 wt. % of surface modified Al2O3 Fe-AM and Al2O3 Fe-BD particles, were compared to the neat polymer matrix. Adhesion parameter was evaluated using the micro hardness testing method. The comparison of determined contact angle with adhesive parameter, obtained from micro hardness measurements, was discussed in relation to structural effect of reinforcement used.

Transport of uncharged organics in ion-exchange membranes: experimental validation of the solution-diffusion model

The concentration-gradient transport of uncharged organics in ion-exchange membranes (IEMs) and the experimental validation of the solution-diffusion model were investigated. Free interaction energies between organics (paracetamol, theophylline, phenazone) and IEMs were above 0, indicating potential solute resistance against partitioning into the membrane phase. Experiments performed in diffusion cells showed a linear increase in the organics concentration in the receiving solution as a function of time, suggesting a purely diffusion-driven transport. A higher organics transport was observed in anion-EMs (AEMs) than in cation-EMs (CEMs), possibly due to the higher cross-linking and lower affinity to organics of CEMs. A correlation between transport and molecular weight was observed in all IEMs following the trend: paracetamol > theophylline > phenazone. The experimental validation of the solution-diffusion model showed that the model underestimated the solutes transport in IEMs. Monte Carlo analysis indicated that the discrepancy between modeled and measured fluxes could not be eliminated even after considering experimental errors. The method for determining contact angle would influence the modeled fluxes. Moreover, the definition of diffusive hindrance factor may lead to these discrepancies, requiring further investigation. This study contributes to the field of selective organics/inorganics separation in the treatment and resource recovery of organics-rich industrial wastewater.

Graphene Translucency and Interfacial Interactions in the Gold/Graphene/SiC System.

Integration of graphene into electronic circuits through its joining with conventional metal electrodes (i.e., gold) appears to be one of the main technological challenges nowadays. To gain insight into this junction, we have studied the physicochemical interactions between SiC-supported graphene and a drop of molten gold. Using appropriate high-temperature experimental conditions, we perform wetting experiments and determine contact angles for gold drops supported on graphene epitaxially grown on 4H-SiC. The properties of the metal/graphene interface are analyzed using a wide variety of characterization techniques, along with computational simulations based on density functional theory. In contrast with the established literature, our outcomes clearly show that graphene is translucent in the gold/graphene/SiC interface, and therefore its integration into electronic circuits primarily depends on the right choice of the support to produce favorable wetting interactions with liquid gold.

Stability facilitation of nanoparticles prepared by ultrasound assisted solvent-antisolvent method: Effect of neem gum, acrylamide grafted neem gum and carboxymethylated neem gum over size, morphology and drug release

In present research, etoricoxib nanoparticles were prepared using newly developed ultrasonication assisted solvent-antisolvent method. Neem gum (NGP) and their semisynthetic derivatives NGP-g-Am (acrylamide graft copolymer of neem gum) and CMNGP (carboxymethylated neem gum) were used to provide stability to drug nanoprecipitates. In this research response surface methodology based on 32 factorial design was utilized to evaluate the effect of two independent variables (concentration of drug and polymer) over size and entrapment efficiency of nanoparticles (dependent variables). When compared with pure drug nanocrystals, polymer stabilized molecular composite nanoparticles were of smaller size and spherical shape. CMNGP stabilized composite nanoparticles shown smaller size hence better performance in terms of solubility and dissolution rate as compared to NGP and NGP-g-Am. As shown by zeta seizer analysis for the same concentration of drug and stabilizer, size of nanoparticles were found in the range of NGP-g-Am > NGP > CMNGP and reverse case was observed for dissolution rate. Contact angle determination easily predict better hydrophilicity of CMNGP than NGP followed by NGP-g-Am. DSC thermogram predict the amorphous nature of CMNGP than NGP and NGP-g-Am. SEM revealed spherical shaped and non-aggregation of nanoparticles. Prepared nanosuspension show no aggregation and Ostwald repining after 45 days when ultrasonicated for 5 s. t90% of optimized formulations of NGP (N9), NGP-g-Am (A8) and CMNGP (C1) was found to be 249.46 min, 296.63 min and 223.39 min and followed 1° order, Higuchi and 1° order kinetics of drug, respectively. Similarity factor analysis predict that release pattern of drug from three different polymer stabilized nanoparticles are significantly differ to each other. Particle size of nanoparticles was studied in presence of solvent and findings showed no change in size after 45 days.

Determination of dynamic contact angles within microfluidic devices

Here, we report a single-point detection method for the determination of dynamic surface conditions inside microfluidic channels. The proposed method is based on monitoring fluorescence amplitude as a function of the convolution of a laser beam with segmented flow consisting of two immiscible liquids, one containing fluorescent dye. The fluorescence amplitude is determined by the flow rate and the droplet shape, which is affected by the channel surface properties. We modeled the interaction of a droplet and a laser beam via computer-aided design software, using the laser beam location in relation to the droplet shape as a parameter. The method was applied to fused silica capillaries with both unmodified and modified surfaces, with segmented flow exhibiting water contact angles of ≈ 30° and ≈ 100°, respectively. The method allows discrimination between hydrophillic and hydrophobic surfaces, as well as the quality of the treatment. The results were verified using fluorescence imaging of the droplets via a stroboscopic technique. We also applied this method to the analysis of microfabricated channels with non-circular cross sections. We demonstrated that the technique enables the determination of the hydrophobicity of channel surfaces, a crucial property required for the generation of segmented flow or emulsions for applications such as digital PCR.

Preparation and characterization of modified polyphenylsulfone membranes with hydrophilic property for filtration of aqueous media

In the present research, the low water flux of polyphenylsulfone membranes was addressed, and a novel improvement in their water permeation and fouling resistance was achieved using polyethylene glycol (PEG) as the hydrophilic additive. Scanning electron microscopy and field emission scanning electron microscopy, atomic force microscopy, attenuated total reflection Fourier‐transform infrared spectroscopy, thermogravimetric analysis, and tensile test were applied for the investigation of membrane morphology, surface topography, surface chemical structure, thermal stability, and mechanical properties, respectively. Moreover, the relative hydrophilicity/hydrophobicity of the membranes was assessed via determination of membrane water uptake capacity and water contact angle. The membrane performance was studied and compared by determination of pure water flux and filtration of canned beans production wastewater as well as bovine serum albumin solution. The filtration results indicated a remarkable pure water flux and 100% turbidity rejection provided by the polyphenylsulfone/PEG 20 000 membrane. In addition, it was confirmed that the amount of residual PEG within the membrane was increased with increasing PEG molecular weight and concentration.

Collagen Hydrolysate as Sustainable Additive for Cereal Seed Treatment

The paper presents new results on the application of collagen hydrolysates characterised in terms of molecular weight, polydispersity (GPC/ SEC), chemical composition and free amino acid composition (GC-MS) for the treatment of cereal seeds. Surface tension and contact angle determinations (VGA Optima XE) have highlighted an improvement in the hydrophilicity of collagen hydrolysates in pesticide mixtures as premises for the adherence of wheat seeds onto the surface. The identification of a 39% higher gibberellic acid concentration (RP-HPLC) in germinated seeds in the collagen hydrolysate, and the presence of free amino acids and low molecular weight fractions were correlated with the biofertilizing and biostimulating effects registered in field experiments on wheat crops.

Water wettability of graphene: interplay between the interfacial water structure and the electronic structure.

Wetting phenomena are ubiquitous and impact a wide range of applications. Simulations so far have largely relied on classical potentials. Here, we report the development of an approach that combines density-functional theory (DFT)-based calculations with classical wetting theory that allows practical but sufficiently accurate determination of the water contact angle (WCA). As a benchmark, we apply the approach to the graphene and graphite surfaces that recently received considerable attention. The results agree with and elucidate the experimental data. For metal-supported graphene where electronic interactions play a major role, we demonstrate that doping of graphene by the metal substrate significantly alters the wettability. In addition to theory, we report new experimental measurements of the WCA and the force of adhesion that corroborate the theoretical results. We demonstrate a correlation between the force of adhesion and WCA, and the use of the atomic force microscope (AFM) technique as an alternative measure for wettability at the nanoscale. The present work not only provides a detailed understanding of the wettability of graphene, including the role of electrons, but also sets the stage for studying the wettability alteration mechanism when sufficiently accurate force fields may not be available.

Silicone/Ag@SiO2 core-shell nanocomposite as a self-cleaning antifouling coating material.

The effects of Ag@SiO2 core–shell nanofiller dispersion and micro-nano binary structure on the self-cleaning and fouling release (FR) in the modelled silicone nano-paints were studied. An ultrahydrophobic polydimethylsiloxane/Ag@SiO2 core–shell nanocomposite was prepared as an antifouling coating material. Ag@SiO2 core–shell nanospheres with 60 nm average size and a preferential {111} growth direction were prepared via a facile solvothermal and a modified Stöber methods with a controlled shell thickness. Ag@SiO2 core–shell nanofillers were inserted in the silicone composite surface via solution casting technique. A simple hydrosilation curing mechanism was used to cure the surface coating. Different concentrations of nanofillers were incorporated in the PDMS matrix for studying the structure–property relationship. Water contact angle (WCA) and surface free energy determinations as well as atomic force microscopy and scanning electron microscope were used to investigate the surface self-cleaning properties of the nanocomposites. Mechanical and physical properties were assessed as durability parameters. A comparable study was carried out between silicone/spherical Ag@SiO2 core–shell nanocomposites and other commercial FR coatings. Selected micro-foulants were used for biological and antifouling assessments up to 28 days. Well-distributed Ag@SiO2 core–shell (0.5 wt%) exhibited the preferable self-cleaning with WCA of 156° and surface free energy of 11.15 mN m−1.

Особливості оцінки контактного кута на наномасштабі

The information regarding the wetting characteristic is important in various aspects of surface science. One of the markers that more frequently uses for describing of wetting characteristics is the wetting angle. Even an estimation of the wetting at the macroscale is a tricky issue, because of the hysteresis between receding and advancing values presence. In the same time, the situation is more complicated for a nanoscopic droplet due to the tangible thickness of the interphase region, what causes an uncertainty of the dividing surface determination, as a consequence it causes an uncertainty of the contact angle determination. In this work using methods molecular dynamics we performed simulations of the cylindrical nanodprolet and the layer of the argon fluid. The density maps and the maps of tension tensor were also measured. Basing on the analysis of the maps within the framework of the Gibbs approach, the equimolar surfaces and the surfaces of tension on the liquid-gas interface and the liquid-solid interface was determined. For the cylindrical nanodroplet, the equilibrium contact wetting angles formed by the corresponding dividing surfaces were estimated. The measured angles differ by more than 10%.

Adsorption of cationized xylans onto polyethylene terephthalate fabrics for antimicrobial medical textiles

The main aim of this research was development of thin functional xylan layers on polyethylene terephthalate (PET) fabric surfaces. Xylans, derived from hard wood and oat spelt, were modified chemically in order to introduce cationic functional groups. Cationization of xylans was proved by elemental analysis, total bound nitrogen determination, and Raman techniques, as well as by polyelectrolyte titrations. The antimicrobial activity of xylans was investigated by the determination of Minimal Inhibitory Concentration against bacteria S. aureus and E. coli, and fungi C. albicans. Xylan solutions were then applied onto PET fabric using the spray coating technique. Charging behavior of the treated PET fabric samples was evaluated by potentiometric titration supported by X-ray electron spectroscopy. Hydrophilicity was examined by the water contact angle determination. The morphology of coated fabrics was analyzed using Scanning Electron Microscopy. The results of microbial testing showed that PET fabrics functionalized by cationic xylans act antimicrobially against S. aureus and E. coli. The presented work suggests that cationized xylans, originally derived from hard wood and/or oat spelt, could be applied successfully as a coating material for PET fabrics in order to introduce hydrophilicity and antimicrobial properties.

Uporaba naravnih olj za površinsko zaščito lesa navadne bukve

Different natural drying oils were used for surface finishing of common beech wood (Fagus sylvatica L.). Surface performances and properties of the oiled surfaces were investigated according to the standard tests. Drying time, colour and gloss changes, uptake of oils into wood and uptake of liquid water into oiled wood, were determined, and the wettability of oiled wood surfaces was investigated by determination of the apparent contact angles of water. The results of the standard resistance tests showed that tung oil, the commercial decking and linseed oil had the best water repellent and protective properties. Worse properties were determined for those surfaces finished with walnut, hemp and coconut oils.

Antibacterial silver nanoparticle coating on oxo-biodegradable polyethylene film surface using modified polyethylene and corona discharge

This work compares the deposition of antimicrobial silver nanoparticles (AgNP) on oxo-biodegradable polyethylene (OB-PE) film surface by two methods: one by using blends of polyethylene (OB-PE) with maleic anhydride-modified PE (PEgMA) with two different molecular weights at various blend ratios and other by the OB-PE surface treatment with corona discharge at various treatment conditions. The surface of OB-PE film was treated by corona discharge and then both corona-treated film and OB-PE/PEgMA blend film were immersed in a colloidal solution of silver nanoparticles that were synthesized by chemical reduction of silver nitrate using ultrasound radiation. The efficiency of each surface treatment for surface modification was evaluated by FTIR-ATR spectrometry and contact angle determinations. The attachment of AgNP on OB-PE films was evaluated by UV–Vis and atomic absorption spectroscopy, STEM, XRD and antifungal efficiency. Both surface modifications induced the formation of polar groups that attached more AgNP on the OB-PE surface. Corona-treated films showed better silver attachment and antimicrobial activity but with lower mechanical properties apparently attributed to the initiation of polymer degradation by the corona discharge. The antimicrobial determinations indicated that these nanocomposite films could have different antimicrobial activity against Aspergillus niger depending on the PEgMA used and corona discharge conditions. The observed results could be applied to the design of industrial OB-PE films for packaging.

Study of pool boiling process for the refrigerant R11, isopropanol and isopropanol/Al2O3 nanofluid

This paper presents the results of experimental study of the pool boiling process for the nanofluids isopropyl alcohol (isopropanol)/Al2O3. The test experiments on pool boiling of the isopropanol (C3H8O) and refrigerant R11 (CCl3F) were conducted to verify the reliability of developed experimental setup. The experimental values of the determined heat transfer coefficients and bubble departure diameters have been compared with several models reported in the literature. An effect of Al2O3 nanoparticles on the heat transfer coefficient and bubble departure diameter during isopropanol boiling was measured and analysed.Moreover, the experiments for determination of the isopropanol contact angle on the bare surface and surface coated by nanoparticles after nanofluid boiling have been performed in order to evaluate its effect on the boiling process.Finally, obtained experimental data for the heat transfer coefficient of isopropanol, refrigerant R11 and nanofluids isopropanol/Al2O3 using RPI heat flux partitioning model have been fitted with an uncertainty less than 10%.

Transparent, abrasion-insensitive superhydrophobic coatings for real-world applications

Superhydrophobic surfaces and surface coatings are of high interest for many applications in everyday life including non-wetting and low-friction coatings as well as functional clothing. Manufacturing of these surfaces is intricate since superhydrophobicity requires structuring of surfaces on a nano- to microscale. This delicate surface structuring makes most superhydrophobic surfaces very sensitive to abrasion and renders them impractical for real-life applications. In this paper we present a transparent fluorinated polymer foam that is synthesized by a simple one-step photoinitiated radical polymerization. We term this material “Fluoropor”. It possesses an inherent nano-/microstructure throughout the whole bulk material and is thus insensitive to abrasion as its superhydrophobic properties are not merely due to a thin-layer surface-effect. Due to its foam-like structure with pore sizes below the wavelength of visible light Fluoropor appears optically transparent. We determined contact angles, surface energy, wear resistance and Vickers hardness to highlight Fluoropor’s applicability for real-word applications.