Strong Hydrophobic Surface Research Articles

Hybrid coating of polydimethylsiloxane with nano-ZrO2 on magnesium alloy for superior corrosion resistance

To enhance the corrosion resistance of magnesium alloys, an organic-inorganic coating of polydimethylsiloxane (PDMS) hybridized with ZrO2 nanoparticles is developed, where the PDMS is selected as the polymeric matrix for superhydrophobic surface, and nano-ZrO2 particles as a physical barrier to strengthen and densify the polymeric matrix. The nanocomposite materials were characterized by field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectrophotometry (FT-IR), and X-ray diffraction (XRD). Electrochemical, dropping corrosion, and salt spray tests were carried out to evaluate the effect of the amount of ZrO2 on the corrosion property of the PDMS-ZrO2 coatings. Thermal stability, hydrophobicity, and corrosion resistance of the composite coatings are substantially improved by the introducing ZrO2 modifier into PDMS matrix. Depending on the ZrO2 content, the PDMS-ZrO2 hybrids exhibit superior corrosion resistance, where the corrosion current density of PDMS-ZrO2 coatings containing 10% (wt.%) ZrO2 decreases about five orders of magnitude compared with Mg alloy substrate. Furthermore, it is noteworthy that ZrO2 nanoparticles are filled in the PDMS matrix to provide a long-term protection in the salt spray test up to 210 h. The PDMS-ZrO2 coatings demonstrate an excellent shielding ability for the Mg alloy, which is attributed to the strong hydrophobic surface of PDMS and compact network structure separated by the physical barrier of ZrO2 nanoparticles in the PDMS chains. The proposed mixed matrix membrane guides a design direction for highly water-repellent coating with a long-term corrosion protection performance.

Facile preparation of uniform-sized covalent organic framework nanoflowers as versatile sample-pretreatment platforms for sensitive and specific determination of hazardous substances

Covalent-organic frameworks (COFs) have lately received extensive interest for their outstanding performance, especially to adsorption of hazards, while easy-preparation of uniform-sized COFs hold a great challenge. This research presented a simple synthesis method of flower-shaped COF (nanoflower) with strong hydrophobic surface at room temperature. Taking advantage of its easy-prepared and uniform-sized features, we proposed a versatile and efficient sample-pretreatment platform by employing the nanoflower COF for affinity adsorption of various hydrophobic biotoxins and further surface imprinting for selective enrichment of specific biotoxin (COF@MIP), respectively. The COF@MIP was integrating COF with molecular imprinting technique to achieve selective identification of sterigmatocystin (ST) with high specificity and sensitivity. They both exhibited well reusability, preserving 81% of initial activity after being used for six cycles. The as-prepared materials coupled with offline solid phase extraction (SPE) and high performance liquid chromatography (HPLC) were successfully applied to five common cereals with good recoveries in the range of 70.3–100.7%. Moreover, the principle of versatile sample pretreatment and detection platform based on the facile-prepared and uniform-sized COF nanoflower would be easily extended to other hazards. It provided a prospective approach for the pretreatment and determination of hazardous substances with low level in complex sample matrix.

Interfacial nanobubbles on different hydrophobic surfaces and their effect on the interaction of inter-particles

To develop interfacial nanobubbles (INBs) into application fields, it is of great significance to understand the properties of INBs and their effect on the interaction of inter-particles. In this paper, the morphology of INBs on different hydrophobic surfaces was researched by total internal reflection fluorescence microscopy (TIRF) and atomic force microscope (AFM). A hydrophobic AFM colloid cantilever was used to measure the interaction of inter-particles in the absence and presence of INBs. The results confirm that the formation of INBs is closely related to the hydrophobicity of substrates, more large INBs form on the strong hydrophobic surface (SS). Furthermore, the magnitude and range of the hydrophobic interaction force are positive related to the dimension of INBs. Besides, multiple approaches of hydrophobic colloid to SS, the hydrophobic interaction is further enhanced due to the merging and cavitation of INBs. Therefore, the results presented here provide the relationship between INBs formation and surface hydrophobicity, as well as the effect of INBs on particles interaction. The formation of INBs should be responsible for the hydrophobic interaction of inter-particles, which is a basic insight into the hydrophobic interaction between particles.

Optimizing a fabricating program for wearable super-hydrophobic cotton by clean production technology of plasma and reducing chemical consumption

The atmospheric-pressure cold plasma jet was used as a clean production technology together with fluorine-free water repellent agent (FfWRA) to optimize the fabricating program for wearable super-hydrophobic cotton. By the contrasting test of sample surfaces treated via FfWRA and by plasma in advance with fluorine-free agent (P-FfWRA), it was concluded that the plasma can evidently strengthen the hydrophobic finishing effect. Hydrophobicity study indicates the contact angle on sample treated by P-FfWRA reached 153°. Even more important, meantime a 44.4% reduction in the chemical consumption can be achieved with the optimization method. Scanning electron microscope (SEM) and atomic force microscope (AFM) observations verified that large amounts of nano-scaled roughness uniformly presented on the modified fiber surface. X-ray photoelectron spectroscopy (XPS) measurements reveals that there was a reduction of up to 40% in oxygenous groups on the cotton fabric processed by P-FfWRA. The washing test show that the P-FfWRA treated sample still have a strong hydrophobic surface with a contact angle of 147°even after washing 25 times. The breathability of the modified sample even has a small increase due to the variation in fiber diameter after the modification. The optimized fabricating program has been proved to be an environmentally friendly, high efficiency production technology. This paper provides theoretical support and practical significance for further research on the saving of the chemical consumption.

Effects of mole fraction and surface wettability on evaporation of Ar/Kr mixtures: A molecular dynamics study

The phase transition of fluid on the solid surface plays an important role in engineering, while the mechanism of phase transition is still need to be studied in depth. Therefore, molecular dynamics simulations were employed to investigate the evaporation of different mole fraction of Ar/Kr mixtures on several wettability Pt substrates (weak hydrophobic surface, hydrophilic and weak hydrophobic mixed surface, hydrophilic and strong hydrophobic mixed surface, hydrophilic surface) at 200 K. The kinetic energy of fluid atoms and the interaction energy between Pt and fluid atoms were employed to understand the evaporation process. The vapor film boiling was observed in the systems with the mole fraction of Ar to be 100%, 75% and 50%. This leads to the heat flux significantly decreasing and heat transfer deterioration. The addition of Kr atoms will alleviate and prevent vapor film boiling of Ar atoms. Besides, the more the mole fraction of Kr in the system, the less possibility of Kr atoms can evaporate from the evaporation region. The strong hydrophobic surface would lead to the bubble generated earlier than weak hydrophobic surface. And the earlier generated bubble on hydrophilic and strong hydrophobic mixed surface will enhance the evaporation process than that on hydrophilic and weak hydrophobic mixed surface.

Clay/au nanoparticle composites as acetylcholinesterase carriers and modified-electrode materials: A comparative study

This work presents the first comparative study on syntheses, characterization, and applications of different clay/gold nanoparticle composites (clay/AuNPs) as acetylcholinesterase (AChE) carriers and modified-electrode materials to detect chlorpyrifos, an organophosphate pesticide. The selected based-clays were plate-like kaolinite (Kaol; 1:1 aluminum phyllosilicate), globular montmorillonite (Mt; 2:1 aluminum phyllosilicate), globular bentonite (Bent; 2:1 aluminum phyllosilicate), and fibrous sepiolite (Sep; 2:1 inverted ribbons of magnesium phyllosilicate). The clay/AuNPs were synthesized using in situ chemical reduction of the gold precursor with anchoring 3-aminopropyl triethoxysilane (APTES) on the clay surfaces. The studied materials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), nitrogen adsorption/desorption, Fourier transformed infrared (FTIR) spectroscopy, thermogravimetric analyzer (TGA), zeta-potential analysis, and electrochemical impedance spectroscopy (EIS). Surface area, surface charges, and hydrophilic/hydrophobic nature of based-clays and the clay/AuNPs played major roles on AChE loading, residual activity, and sensor storage stability. The Mt/AuNPs was determined, among the studied clays, as the best supports for AChE loading and residual activities due to its high specific surface area and weak electrostatic interaction with the immobilized enzyme. Since apparent catalytic efficiencies kcatapp/KMappof the immobilized AChE in the four clay/AuNPs were found statistically similar, Mt/AuNPs which contained the highest enzyme loading was the favorite modified-electrode material. For chlorpyrifos detection, Kaol/AuNPs-based sensors resulted in the lowest detection limit, presumably due to the strong hydrophobic surface that helps to concentrate the nonpolar pesticide to the vicinity of the immobilized enzyme. Unfortunately, the highest electrostatic repulsion between the Kaol/AuNPs and AChE, and the dehydrated Kaol surface resulted in the lowest storage stability of the AChE pesticide sensors. Overall, Mt/AuNPs showed the highest potential as the AChE carrier and the modified electrode material for chlorpyrifos determination.

Synthesis of novel chitosan-based flocculants with amphiphilic structure and its application in sludge dewatering: Role of hydrophobic groups

Natural polymeric flocculants as sludge conditioners have received great attention due to their non-toxic and biodegradable advantages. However, the application of amphiphilic natural flocculants as sludge conditioners is rarely reported. In this work, the novel chitosan-based flocculants (CS-g-PAO) with amphiphilic structure were synthesized by ultraviolet light initiated method for the enhancement of sludge dewatering performance. The solubility of CS-g-PAO was significantly improved in a wide pH range (2.0–10.0). Various characterization methods were used to investigate the structure, thermal stability and surface morphology of copolymers, suggesting the successful synthesis of CS-g-PAO. In dewatering experiments, CS-g-PAO showed superior dewatering performance, and filter cake moisture content could be decreased to 77.98% from 95.14%. Moreover, the results of extracellular polymeric substances (EPS) components indicated that hydrophobic effect of CS-g-PAO was beneficial to remove the protein in S-EPS and TB-EPS, which had the crucial influence on dewatering performance. Furthermore, the dewatering mechanism was discussed based on the effects of zeta potential, apparent viscosity, surface tension and flocs structure on dewaterability. Results revealed that CS-g-PAO had strong hydrophobic association effect and surface activity. In addition, enhanced charge neutralization and hydrophobic interaction played a synergetic role in improving the dewaterability of CS-g-PAO.

Study on the atmospheric cold plasma (ACP) treatment of zein film: Surface properties and cytocompatibility

The cell adhesion and proliferation of zein-based biomaterials in cell culture application are limited by the strong hydrophobic surface with low surface energy. In this study, atmospheric cold plasma (ACP) was developed as a modification approach in enhancing the surface hydrophilic and cytocompatibility of zein films. The results indicated that water contact angles decreased from 72.85° (untreated) to 47.43° under the voltage of 100 V. The improvement of the surface free energy (SFE) was mainly attributed to the polar component rather than dispersive component. X-ray photoelectron spectroscopy (XPS) results indicated the change of surface physicochemical properties was mainly due to the partially transformation of long-chain aliphatic hydrocarbons (CH and/or CC) to oxygen- and nitrogen-containing bonds (CO, CO and CN). Furthermore, the content of secondary structure demonstrated β-turn and α-helix were transformed into β-sheet and random coil after ACP treatment. Combining with the cell experiment results, plasma treatment could significantly improve the adhesion rate and proliferation activity of C2C12 cells on zein films. With better cytocompatibility, the potentials of zein in tissue engineering scaffold could be readily exploited.

Dispersion of Boron Nitride Nanotubes by Pluronic Triblock Copolymer in Aqueous Solution.

Boron nitride nanotubes (BNNTs) have been of interest for their excellent thermal, electrical, and mechanical properties, and they have a broad spectrum of potential applications, such as in piezoelectric materials, reinforcement of materials, and electrothermal insulation materials. For practical use of BNNTs, it is desirable to disperse them in aqueous solution, which improves convenience of handling. However, it is still difficult to make a homogenous and stable BNNT dispersion in aqueous solution, due to their strong van der Waals interactions and hydrophobic surface. To solve these problems, we used Pluronic P85 and F127, which have both hydrophilic groups and hydrophobic groups. Here, we report the wrapped structure of a Pluronic polymer-BNNT dispersion by using small-angle neutron scattering, UV–Vis spectroscopy, thermogravimetric analysis, and atomic force microscopy.

Enhanced Osseointegration Ability of Poly(lactic acid) via Tantalum Sputtering-Based Plasma Immersion Ion Implantation.

Poly(lactic acid) (PLA) is the most utilized biodegradable polymer in orthopedic implant applications because of its ability to replace regenerated bone tissue via continuous degradation over time. However, the poor osteoblast affinity for PLA results in a high risk of early implant failure, and this issue remains one of the most difficult challenges with this technology. In this study, we demonstrate the use of a new technique in which plasma immersion ion implantation (PIII) is combined with a conventional DC magnetron sputtering. This technique, referred to as sputtering-based PIII (S-PIII), makes it possible to produce a tantalum (Ta)-implanted PLA surface within 30 s without any tangible degradation or deformation of the PLA substrate. Compared to a Ta-coated PLA surface, the Ta-implanted PLA showed twice the surface roughness and substantially enhanced adhesion stability in dry and wet conditions. The strong hydrophobic surface properties and biologically relatively inert chemical structure of PLA were ameliorated by Ta S-PIII treatment, which produced a moderate hydrophilic surface and enhanced cell-material interactions. Furthermore, in an in vivo evaluation in a rabbit distal femur implantation model, Ta-implanted PLA demonstrated significantly enhanced osseointegration and osteogenesis compared with bare PLA. These results indicate that the Ta-implanted PLA has great potential for orthopedic implant applications.

Study on the Super Hydrophobic of Wood by ZnO Modification

This paper explores the difference of surface hydrophobicity between unmodified Chinese fir wood and Chinese fir wood modified by ZnO to demonstrate whether ZnO can effectively make the Chinese fir wood with hydrophobic capability. As an excellent furniture material, the specimens of Chinese fir wood was soaked using different concentrations of water acetic acid zinc (Zn (CH3COO)2 - 2H2O) and six methyl tetramine (C6H12N4) under heating conditions till the surface having ZnO thin film, the specimens of drying treatment were modified with stearic acid anhydrous ethanol and contact angle between Chinese fir surface and distilled water was measured by contact Angle measurement instrument. By comparing the change of the contact angle curve of the unmodified ZnO fir sample and the modified ZnO fir sample, it was found the surface of the unmodified contact angle of ZnO fir sample reduced from 102.93°to 62.36°, what’s more, the figure was continuing to decrease, indicating a strong fir wood surface hydrophilic .The contact angle reduced a little when fir wood surface treated with ZnO, then it stayed above 136°. There is no significant change of the contact angles obtained from the modification of the hydrophobic properties of the Chinese fir wood surface with different ZnO reaction solution. Experimental results showed that ZnO can effectively modify the surface of fir , which make it from strong hydrophilic into strong hydrophobic surface , and different concentrations of ZnO has little influence on the hydrophobic properties of fir surface

Arrangement of chromonic liquid crystals near hydrophobic and hydrophillic surfaces

The possibility of utilizing the lyotropic Chromonic Liquid Crystal (LCLC) in the detection of the biological cells, such as bacteria, virus etc. and biological macromolecules like protein, DNA etc. have attracted a number of researchers in recent time. The organization of the LCLC near surfaces is important to explore these applications. We have explored the time-dependent effects of surface re-arrangements of LCLCs (disodium chromo glycate (DSCG) and Sunset Yellow (SSY)) using the polarized microscope. It is found that the initial arrangement of DSCG and SSY depends on the hydrophobicity of the surface. A strong hydrophobic surface leads to the homeotropic arrangements of DSCG and SSY. However, the moderately hydrophobic surface cannot give the homeotropic arrangements of LCLCs. With the passage of time, the evolved texture of the LCLCs is independent of surface hydrophobicity. The effect of surfaces on DSCG is more pronounced compared to that on SSY.

Atomization of petroleum-coke sludge slurry using effervescent atomizer

Experimental investigations were carried out on a bench-scale atomization test facility to explore the atomization performance of petroleum coke sludge slurry (PCSS) which comprises pulverized petroleum coke, sewage sludge, water and a certain amount of chemical additives. In the experiments, effervescent atomizer was employed to spray the petroleum coke sludge slurry. And effects of air injection pressure, air-to-liquid mass flow rate ratio (ALR), exit orifice diameter and rheological properties of petroleum coke sludge slurry with different amount of sewage sludge on the Sauter Mean Diameter (SMD or D32) of the atomized droplets were investigated. Results suggest that petroleum coke particles have strong hydrophobic surface. Solid–liquid separation occurs between petroleum coke particles and water film during atomization. Sewage sludge is viscoelastic non-Newtonian fluids, which would influence the solid–liquid separation process when pulverized petroleum coke and sewage sludge are blended to prepare petroleum coke sludge slurry for atomization. SMD of atomized petroleum coke sludge slurry droplets decreases with ALR increase. However, SMD increases with spray axial distance downstream from the nozzle tip primarily and then decreases. Reduction of exit orifice diameter and increase of air injection pressure could improve the atomization performance, while sewage sludge would weaken the influence on variation of the atomized droplets diameters with increase of the spray axial distance and ALR.

Enhanced Wang Landau sampling of adsorbed protein conformations

Using computer simulations to model the folding of proteins into their native states is computationally expensive due to the extraordinarily low degeneracy of the ground state. In this paper, we develop an efficient way to sample these folded conformations using Wang Landau sampling coupled with the configurational bias method (which uses an unphysical "temperature" that lies between the collapse and folding transition temperatures of the protein). This method speeds up the folding process by roughly an order of magnitude over existing algorithms for the sequences studied. We apply this method to study the adsorption of intrinsically disordered hydrophobic polar protein fragments on a hydrophobic surface. We find that these fragments, which are unstructured in the bulk, acquire secondary structure upon adsorption onto a strong hydrophobic surface. Apparently, the presence of a hydrophobic surface allows these random coil fragments to fold by providing hydrophobic contacts that were lost in protein fragmentation.

Octadecyltrimethoxysilane functionalized ZnO nanorods as a novel coating for solid-phase microextraction with strong hydrophobic surface

In this paper, we have, for the first time, proposed an approach by combining self-assembled monolayers (SAMs) and nanomaterials (NMs) for the preparation of novel solid-phase microextraction (SPME) coatings. The self-assembly of octadecyltrimethoxysilane (OTMS) on the surface of ZnO nanorods (ZNRs) was selected as a model system to demonstrate the feasibility of this approach. The functionalization of OTMS on the surface of ZNRs was characterized and confirmed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The OTMS-ZNRs coated fiber exhibited stronger hydrophobicity after functionalization, and its extraction efficiency for non-polar benzene homologues was increased by a factor of 1.5-3.6 when compared to a ZNRs fiber with almost identical thickness and façade. In contrast, the extraction efficiency of the OTMS-ZNRs coated fiber for polar aldehydes was 1.6-4.0-fold lower than that of the ZNRs coated fiber, further indicating its enhanced surface hydrophobicity. The OTMS-ZNRs coated fiber revealed a much higher capacity upon increasing the OTMS layer thickness to 5 μm, leading to a factor of 12.0-13.4 and 1.8-2.5 increase in extraction efficiency for the benzene homologues relative to a ZNRs coated fiber and a commercial PDMS fiber, respectively. The developed HS-SPME-GC method using the OTMS-ZNRs coated fiber was successfully applied to the determination of the benzene homologues in limnetic water samples with recovery ranging from 83 to 113% and relative standard deviations (RSDs) of less than 8%.

The strong hydrophobic properties on nanoparticles adsorbed core surfaces

A compact hydrophobic nanoparticle (HNP) adsorption layer, which has miro- and nano-dual structural properties like lotus leaf, can be built by adsorbing HNP on core surfaces. A slip velocity on the surface can be produced with the purpose of reducing the water resistance and increasing water injection rate. The results are of significance for the study of HNP drag reduction technology. In this paper we give a briefing of the super hydrophobic properties of the lotus leaf, mosquito legs, and striders leg. The strong hydrophobic surface preparation method with HNP adsorption layer is presented, and physical mechanism of strong hydrophobic surfaces with regular arrangement of HNPs is given. According to the real HNP adsorption core samples, the contact angle range is given, the calculation results accord well with experimental data. Core displacement experimental results show that the average drag reduction rate can be up to 94%.

Heterogeneous condensation properties of ultrafine soot particles (20 nm < d p < 100 nm) after reaction with ozone

Publisher Summary This chapter investigates the condensation properties of carbon aerosols in the Aitken range and changes in the hygroscopicity due to the reaction with ozone. It provides the evidence of the strong influence of the chemical surface properties on the activation of soot particles in the condensation process. For these experiments, an in-situ technique was employed, using a variable supersaturation condensation nucleus counter coveting the range from 10 % up to over 200 % supersaturation. The Kelvin-equivalent diameter of an aerosol particle is defined as the diameter of a water droplet, which starts to grow at the same supersaturation as the particle under study. The theory for the condensation on insoluble particles used for the description of the investigated aerosols was introduced by Fletcher proposing the contact angle as measure for the hygroscopicity of an aerosol particle. The condensation properties of ultrafine carbon particles in the Aitken range were investigated by means of a variable supersaturation condensation nucleus counter. While untreated carbon aerosols exhibited an extraordinary strong hydrophobic surface, the ozone treatment resulted in a significant more hydrophilic behavior of the particles. As the same contact angle was found for all particle sizes and ozone concentrations, the change of the surface properties dominates the condensation properties of the particles, while the agglomerated particle structure is of minor importance for these particles. Critical supersaturations could not be lowered beneath 10 % by ozone treatment and therefore, it seems highly unlikely that these aerosols can act as condensation nuclei. The results indicate that the atmospheric residence time of soot is mainly determined by the surface chemistry of the particles.

Enterotoxigenicity, hemagglutination and cell-surface hydrophobicity in Aeromonas hydrophila, A. Sobria and A. Salmonicida

Thirty-one Aeromonas hydrophila, 13 A. sobria and two A. salmonicida strains of diverse sources were tested for enterotoxigenicity, hemagglutination and cell surface hydrophobicity. Although 93% of the culture supernatant fluids of the Aeromonas strains exhibited cytotoxic effects on Y1 adrenal and Chinese hamster ovary (CHO) cells, typical rounding of Y1 adrenal cells was reproducibly observed before cytotoxicity for 80% of the isolates within 1 h of exposure. Twenty-eight strains were positive for delayed permeability factor (DPF) activity in rabbit skin. Culture filtrates of 16 of 20 strains that were positive both in the Y1 adrenal cell test and for DPF activity elicited fluid accumulation in rabbit ileal loops. The DPF and ileal loop activities were neutralizable by cholera antitoxin. All, except two strains each of A. sobria and A. hydrophila, produced a heat-stable, rapid permeability factor (RPF) detected in rabbit skin. Heat-treated culture supernatant fluids of two A. hydrophila and one A. sobria isolate gave positive responses in the infant mouse assay. Nine other strains gave borderline reactions. When A. hydrophila and A. sobria isolates were grown in broth, approximately 90% agglutinated bovine, chicken, human group A and guinea-pig erythrocytes in the presence of mannose at 4°C and/or 20°C. The two A. salmonicida isolates produced mannose resistant hemagglutination (MRHA) of these four blood types. Hydrophobic interaction chromatography indicated adhesive potential in 61% A. hydrophila and 100% A. sobria strains expressing weak to strong hydrophobic cell surface properties. The results of these investigations strongly imply that the Aeromonas strains produce a cytotonic enterotoxin immunologically related to cholera toxin. Adhesive characteristics were commonly found in both clinical and routine isolates.