Hydrophobic SiO2 Nanoparticles Research Articles

Co-hydrolysis of TEOS and DDS to obtain a modified hydrophobic SiO2 insulation layer for FeSiBC amorphous magnetic powder core with low energy loss

The hysteresis effect and eddy currents caused by alternating magnetic fields greatly impede the improvement of the working efficiency and performance stability of soft magnetic powder cores. In this work, modified hydrophobic SiO2 nanoparticles were prepared by tetraethyl orthosilicate (TEOS) and dimethyl-diethoxy-silane (DDS) as co-precursors through sol–gel methods. The effect of different proportions of DDS and TEOS on the amorphous magnetic powder cores performance was studied. It was demonstrated that the insulation layer in DDS and TEOS co-precursors hydrolyzed composite powders exhibited more uniform distribution compared with TEOS hydrolyzed alone counterpart. The introduction of methyl groups reduced the accumulation of hydrolysis intermediates on the surface of FeSiBC powders. Furthermore, the addition of DDS reduced eddy current loss significantly with a low hysteresis loss. The total energy loss of the DDS and TEOS co-hydrolysis powder core were reduced by 16.1 % and 7.7 % at 1 MHz, 0.05 T compared to the uncoated powder core and the TEOS hydrolysis alone counterpart, respectively. The presented results provide insights into improving the application range and energy utilization efficiency for the magnetic powder cores.

Fabrication of a Janus Copper Mesh by SiO2 Spraying for Unidirectional Water Transportation and Oil/Water Separation.

Massive discharge of oily wastewater and frequent occurrence of offshore oil spills have posed an enormous threat to the socioeconomic and ecological environments. Janus membranes with asymmetric wettability properties have great potential for oil/water separation applications and have attracted widespread attention. However, existing Janus membranes still suffer from complex and costly manufacturing processes, low permeability, and poor recyclability. Herein, a novel and facile strategy was proposed to fabricate a Janus copper mesh with opposite wettability for unidirectional water transport and efficient oil/water separation. The hydrophilic side of the Janus copper mesh was prepared by coating it with Cu(OH)2 nanoneedles via a chemical oxidation method. The hydrophobic side was fabricated by coating it with hydrophobic SiO2 nanoparticles via a facile spraying method. The as-prepared Janus copper mesh showed asymmetric surface wettability, which can achieve unidirectional water transport and efficient oil/water separation with excellent recyclability, exhibiting great application potential for droplet manipulation and wastewater purification.

Durable, multifunctional cotton fabrics with in situ deposited micro/nanomaterials for effective self–cleaning, oil–water separation and antibacterial activity

The facile modification of cotton fabrics for excellent self–cleaning, oil–water separation, and antibacterial activity is of great interest for multifunctional requirements. Herein, a durable, robust, fluorine–free multifunctional cotton fabric was fabricated via in-situ growing zeolitic imidazolate framework-67 (ZIF-67) on the cotton surface, followed by depositing hydrophobic SiO2 (H-SiO2) nanoparticles synthesized via an improved Stöber reaction. Meanwhile, the abundant hydroxyls of the cotton fabrics provided the necessary ion interaction sites for the uniform deposition of micro/nanomaterials, confirmed by the visualized Raman imaging technology. The resultant H-SiO2/ZIF-67@cotton fabric exhibited superhydrophobicity with a water contact angle of 159° and versatile self–cleaning, antifouling, oil–water separation, as well as prominent antibacterial activity against S. aureus and E. coli. At the same time, the superhydrophobic cotton fabric possessed excellent durability and stability against harsh environments, including abrasion, washing, acid, base, salt, and organic solvents. This facile technique can be applied for large-scale production of multifunctional superhydrophobic cotton fabrics due to its easy operation, low cost, and environmental friendliness.

Study on the superhydrophobic coatings with antifouling and anticorrosion properties

The corrosion caused by marine organisms adhering to the wall surface is one of the main reasons for the failure of ships and equipment, and leads to shortened life and increased maintenance costs, and this has seriously affected the development of the national economy. Therefore, it is very important to develop a new composite material to protect the metal substrate from biological corrosion. In this article, a superhydrophobic surface was prepared by simply spraying silicone rubber emulsion containing hydrophobic SiO2 nanoparticles onto a graphene silicone rubber (GSR) pre-coated substrate (SiO2-GSR). The antifouling ability was investigated under laboratory conditions and real marine environments, and the results show that the SiO2-GSR coating has good antiadhesion effect and longer antifouling ability. The anticorrosion performance was evaluated by electrochemistry methods, and the SiO2-GSR has good corrosion resistance ability. Additionally, the SiO2-GSR film still exhibited a strong antifouling and anticorrosion ability after immersed in marine environment for 6 months. Therefore, SiO2-GSR can be applied to the maritime field as an effective antifouling and anticorrosion coating.

Nanofluid Drop Impact on Heated Surfaces.

We experimentally elucidate the impact dynamics of ethylene glycol (EG) droplets laden with both hydrophilic and hydrophobic SiO2 nanoparticles (NPs) onto a flat heated surface in non-boiling, boiling, and Leidenfrost regimes. We use seven nanofluid concentrations (Cp), ranging from 0.89 to 64.3 wt %, and control the surface temperature (Ts) between 100 and 400 °C, while the nanofluid droplet's impact velocity is constant at 0.22 ± 0.02 m/s. Phase diagrams of impact outcomes are established to illustrate the effect of the additive nanoparticles on the droplets' impact dynamics, revealing that nanoparticles modify droplet impact behaviors differently in each regime. In the non-boiling regime, the droplet spreading profile remains unaffected by nanoparticles up to Cp < 11.9 wt % before reaching the maximum spreading diameter (βmax). For nanofluid drops with higher nanofluid concentration, the increasing viscosity with concentration is likely to be the primary factor that affects the droplets' spreading profile in the non-boiling regime Ts ≲ Tsat ≈ 200 °C, as the saturation temperature. In the boiling regime 200 °C < Ts ≲ 350 °C, a small amount of nanoparticle addition (Cp = 0.89 wt %) promotes atomization regardless of nanoparticle wettability. Finally, manifested in a complete rebound due to an intervening vapor layer, the Leidenfrost temperature (TL) of the nanofluid droplets is affected by both nanofluid concentration and nanoparticles' wettability. The nanofluid droplets' TL increases with higher nanofluid concentration; moreover, this Leidenfrost temperature increment is more significant for EG droplets laden with hydrophobic nanoparticles. Our results quantitatively reveal the significant influence of nanoparticle concentrations and wettability on drop spreading, impact outcome, and Leidenfrost temperature on heat surfaces, potentially benefiting applications in coating, spraying, and cooling.

Fabrication and Characterizations of Superhydrophobic Surface with Superior Corrosion Inhibition on Q345b Steel Substrate

AbstractIn this work, a coherent and cost‐effective method is developed to achieve superhydrophobicity and excellent corrosion resistance on Q345B steel surfaces. The method involves sequential etching with hydrochloric acid and hydrofluoric acid, passivation with potassium permanganate, treatment with bis‐(γ‐triethoxysilylpropyl)‐tetrasulfide (KHSi69，BT), and modification with hydrophobic SiO2 nanoparticles. The effects of etching and passivation time, including SiO2 doping ratio on the wettability and corrosion resistance of the prepared surfaces are investigated. The results demonstrate that the surface exhibits a micro–nano multilayer and modified nano‐multiscale cluster structure which has a contact angle (CA) of 155.8 ± 1.7° and a sliding angle (SA) of 5 ± 0.5° by employing the following conditions: hydrochloric acid etching time of 10 min, hydrofluoric acid etching time of 25 min, passivation time of 300 min, and a 3 wt% SiO2 doping ratio. Moreover, the surface displays extremely weak droplet adhesion and excellent self‐cleaning properties. Furthermore, the corrosion inhibition of the prepared steel surface is evaluated using potentiodynamic polarization curves and electrochemical impedance spectroscopy. The results indicate that the corrosion inhibition efficiency of the superhydrophobic surface is enhanced by about 89.95% compared to the traditional two‐step processing involving etching and modification. These findings expand the potential applications of steel.

Development of a high flux Janus PVDF membrane for oily saline water desalination by membrane distillation via PDA-TEOS-APTES surface modification

Membrane distillation (MD) is a promising approach for water desalination. However, in practice, this process is hindered by poor water flux and severe membrane fouling. In this study, a series of Janus membranes were designed for the desalination of oily saline water via direct contact membrane distillation (DCMD). Janus membranes were fabricated by a simple and facile method, direct deposition of dopamine (DA), tetraethylorthosilicate (TEOS), and aminopropyltriethoxysilane (APTES) on one side of the polyvinylidene fluoride (PVDF) membrane, which was modified by hydrophobic SiO2 nanoparticles. In brief, one side of the optimum Janus membrane was strongly hydrophobic (WCA: 149.7 ± 1°) while another side exhibited in air hydrophilicity (WA: 36.3 ± 1.2°) and underwater superoleophobicity. Additionally, the optimum Janus membrane experienced a remarkable enhancement in water flux, reaching an impressive value of 52.6 kg/m2h, (69.2 % increment compared to the pristine PVDF). Notably, the optimal Janus membrane demonstrated long-term stability and significant resistance toward oil fouling during the DCMD desalination of oily saline water while preserving its rejection and high vapor flux. The applied strategies may offer a fresh perspective on membrane design with efficient performance for MD by a facile method.

A Computational Chemistry Approach to the Molecular Design of SiO2 Nanoparticles Coated with Stearic Acid and Sodium Stearate in Ethanol Solvent.

Preparation of hydrophobic SiO2 nanoparticles (NPs) coated with different surfactants is important due to their potential application in different fields of chemistry. In this work, a combined experimental and Molecular Dynamics (MD) simulation approach, is advanced to characterize the adsorption process, in ethanol as a solvent, of stearic acid and sodium stearate on SiO2 spherical NPs with different ionization degrees (0%, 10%, and 23.3%). The main objective is to gain molecular insight into the factors involved in the preparation of hydrophobic coated NPs, which involves the intervention of ion-dipole, electrostatic, and hydrogen bond-type interactions depending on the surfactants and the nature SiO2 NPs. Our results demonstrate that the SiO2 NPs have a good affinity for ethanol solvent medium., as confirmed through the analysis of the Radial Distribution Functions (RDFs)), which indicates that hydrogen bonds are formed at a distance of ∼0.192 nm between ethanol and SiO2 NPs. The presence of Na+ ions reduce the electrostatic repulsion between the -COO- and -SiO- groups in NPs with degrees of ionization of 10% and 23.3%, because it acts as a bridge and thus favors the adsorption between the silanol and carboxylic groups. The investigation of the Potentials of Mean Force (PMFs) suggests that the adsorption on these NPs, is a spontaneous process compared with the case with 0% ionization degree. The experimental coating of the NPs was studied using Atomic Force Microscopy (AFM), a technique that allows the indirect measure of the Work of Adhesion (Wadh), a key quantity to estimate the energy needed to separate the interfaces AFM tip-sample. The experimental values of Wadh for the pure SiO2 NPs and two modified SiO2 NPs correspond to 2.01 J/m2, 1.72 J/m2 and 1.43 J/m2, respectively. The main conclusion is that the interaction energies between surfactants and SiO2 NPs, estimated from MD simulations, and the Wadh obtained from AFM measurements are correlated, in the sense that the reduction in the Wadh, in a solvent-free environment, corresponds to an increment of the interaction energy in the presence of the solvent. This reduction in Wadh is also associated with the fact that the nature of the coating of the SiO2 NPs surfaces increases the NPs hydrophobicity. Our analysis provides a path for the computational design and the prediction of hydrophobicity of coated NPs, which is the main focus of our work.

Waste oleaster seed-derived activated carbon mixed with coarse particles of fluid catalytic cracking as a highly-efficient CO2 adsorbent at low temperatures

Activated Carbon (AC) derived from low-priced biomass materials has been identified as the efficient and cost-effective candidate for low-temperature CO2 adsorption technique performed, though suffering from limited CO2 capture capacity and heterogeneous fluidization in fluidized-bed systems have remained the main challenges for the industrialization of carbonaceous sorbents. Herein, for the first time, the novel, low-cost, and highly fluidizable carbonaceous sorbent derived from waste-based oleaster seed (OS) has been developed through mixing with cost-effective coarse fluid catalytic cracking (FCC) particles. Hydrophobic SiO2 nanoparticles (NPs) which are well-known as highly efficient assistant materials for enhanced fluidization of hard-to-fluidize particles was also tested for the comparison. To determine the best activator and activator/precursor weight ratio, AC sorbent obtained from the pyrolysis of OS was prepared with two disparate activators of KOH and ZnCl2, and the activator/precursor weight ratios of 2, 3, 4, and the outcomes reveal the highest average CO2 capture capacity of 2.78 mmol/g over three successive cycles for KOH-activated sorbent with activator/precursor weight ratio of 2. This great OS-derived sorbent was mixed with different wt% of coarse FCC and SiO2 NPs to boost its fluidity; for which, the bed expansion reached from 1.6 to 3.5, at the gas velocity of 5 cm/s by mixing with 2.5 wt% FCC, similar to 2.5 wt% SiO2 NPs-assisted sample. In addition to homogeneous fluidizability, a superior multicyclic stability of 95.5% during 25 multiple adsorption/desorption cycles was also assessed. The highly cost-effective FCC-mixed OS-derived activated carbon with both enhanced fluidity and multicyclic CO2 capture activity is introduced as the low-temperature CO2 capture candidate.

Nanoparticle Diffusion and Fixation for the Preparation of Durable Transparent Superhydrophobic Coatings

Due to the size limitation of nanostructures in transparent superhydrophobic (TS) coatings, it is a formidable challenge to construct a TS coating with acceptable mechanical durability. The matrix should connect with nanoparticles and the substrate with more chemical bonds to provide the essential mechanical robustness of the coating layer. In this study, methylacryloxypropyltrimethoxysilane (MEMO) that has three Si–OCH3 groups was polymerized to PMEMO and used as an “ideal” adhesive for the fabrication of durable transparent superhydrophobic (DTS) coatings. Hydrophobic SiO2 nanoparticles were fixed through diffusion into the swollen PMEMO network to avoid the micro-roughness caused by agglomeration. The light transmission of the glass slide after coating with PMEMO/SiO2 was 89.24%. The coating layer maintained its superhydrophobicity with the impact resistance of 160 g of sand and 4.6 m/s water jet for 360 s and heat treatment under 200 °C. The green, non-toxic, and non-fluorinated coating preparation method is universal and scalable, which has promising and large-scale application prospects.

Hydrophobic modification of pyrite with a composite of sodium oleate and SiO2 nanoparticles to inhibit its oxidation for controlling acid mine drainage

The formation of acidic mine drainage (AMD) is mainly due to the oxidation of pyrite in the presence of water. In this study, the environmentally friendly Sodium oleate (SO) was used as hydrophobic agent and SiO2 nanoparticles were added as a filler material to modify pyrite. Na-oleate and nano-SiO2 nanoparticles form a hydrophobic passivation film directly on the pyrite surface in a very simple process.Excellent antioxidant capacity was achieved with the addition of 6% SO and 1 wt% SiO2 at a reaction temperature of 70 °C. Chemical leaching experiments and electrochemical experiments were used to characterise the antioxidant properties of this hydrophobic passivated film. The results showed that the pH of the leachate could be maintained above 5.7, a 2.6 increase over raw pyrite. In addition, the reduction rate of SO42- and total Fe concentration could reach over 83.69% and 97.91%, respectively. SO-SiO2-treated pyrite exhibits lower oxidation rates in electrochemistry and an increased contact angle of 70.1° compared to pristine pyrite. Finally, this paper details the mechanism of the action of SO-SiO2 on the surface of pyrite by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis. The results show that sodium oleate can combine with iron ions to form iron oleate wrapped on the surface of pyrite, while silica nanoparticles attach to pyrite by physical adsorption, filling the pores on the surface of hydrophobic film layer and effectively protecting pyrite from oxidation.

Experimental investigation of hydrophobic and hydrophilic silica nanoparticles on extended surfactant properties: Micro-emulsion, viscosity, and adsorption behaviors

The novel applications of nanoparticles and surfactants are of interest for improving chemical oil recovery performance. In this study, two types of hydrophobic and hydrophilic SiO2 nanoparticles (NPs) were used in conjunction with a binary surfactant system (extended Carboxylate and Dioctyl sulfosuccinate (AOT) surfactants at the ratio of 0.6:0.4 by volume). An extensive series of experiments were performed in the presence of API brine containing NaCl: CaCl2 at the 8:2 wt ratio to study microemulsion phase behavior, interfacial tension (IFT), surfactant adsorption onto NP surfaces, solution and microemulsion viscosity, and oil recovery. The results indicate that the microemulsion phase behavior, optimum salinity (S*), and IFT were influenced by the concentrations and surface characteristics of the NPs. Hydrophobic or hydrophilic NPs at 500 ppm in the binary surfactant system could form Type III microemulsion and decrease the S* from 2 to 1.75 wt%. When the NP concentration reached 1000 ppm, the S* reduced to 1.5 wt%. The IFT value of the neat binary surfactant system at the S* was obtained in an ultralow range (0.0013 mN/m), and the IFT value of the hydrophobic NPs exhibited a more significant reduction than the hydrophilic NP systems. The adsorption result demonstrates that Carboxylate surfactant had lower adsorption onto hydrophilic NP than AOT. COSMO σ-profile and screened charge density illustrated that the low coverage of Carboxylate surfactant was from hydrogen bonding interaction, making the surfactant lie flat on the surface. The viscosity of the NP-surfactant solution was affected by the capacity of the surfactant adsorption onto the NP surface. In this regard, adding the hydrophobic NPs at 1000 ppm provided the highest solution viscosity over the entire shear rate and temperature range. The viscosity of the microemulsion formulated by hydrophobic NPs was higher than that of the microemulsion formulated by the hydrophilic NPs. The system with the lower NP concentration had higher microemulsion viscosity than the system with the higher NP concentration. The oil recovery results indicate that the appropriate NP type and concentration in the surfactant system could increase the displacing viscosity and decrease the microemulsion viscosity compared with the neat surfactant flooding system. The success in improving oil recovery was achieved with recovery efficiency of 88% original oil in place (OOIP).

Synergistic improvement of foam stability with SiO2 nanoparticles (SiO2-NPs) and different surfactants

Foam fluids are widely used in petroleum engineering, but long-standing foam stability problems have limited the effectiveness of their use. The study explores the synergistic effects and influencing factors of SiO2 nanoparticles (SiO2-NPs) with different wettability properties and three different surfactants. The paper investigates the foaming performance of different types of surfactants and analyzes and compares the stability of foam after adding hydrophilic and hydrophobic SiO2-NPs from macroscopic as well as microscopic perspectives, and the effects of temperature and inorganic salts on the stability of mixed solutions. The experimental results show that: 1) hydrophilic nanoparticles can significantly enhance the foam stability of amphoteric surfactants, with a small increase in the foam stability of anionic and cationic surfactants; 2) The concentration of nanoparticles did not have a significant effect on the stability of the cationic surfactants and this conclusion was verified in the experimental results of the surface tension measured below;3) The cationic surfactants showed better temperature resistance at temperatures of 50–90 °C. Both amphoteric surfactant solutions with the addition of hydrophilic SiO2-NPs or hydrophobic SiO2-NPs significantly improved the temperature resistance of the foam at high temperatures. The anionic surfactant solution with hydrophobic SiO2-NPs did not enhance the solution temperature resistance; 4) The surface tension of the surfactant solution gradually increases with increasing concentration of hydrophilic or hydrophobic SiO2-NPs and then levels off; 5) the hydrophilic SiO2-NPs had a significant effect on the salt tolerance of the anionic and amphoteric surfactant solutions. The salt tolerance of cationic surfactant solutions with hydrophobic SiO2-NPs was better than that of surfactants with hydrophilic SiO2-NPs.

A novel, green, cost-effective and fluidizable SiO2-decorated calcium-based adsorbent recovered from eggshell waste for the CO2 capture process

The reduction, storage, and reuse of greenhouse gas carbon dioxide (CO2) is a crucial concern in modern society. Bio-waste adsorbents have recently aroused the investigator's attention as auspicious materials for CO2 capture. However, the adsorption capacity decaying and poor fluidizability during carbonation/calcination cycles of all natural adsorbents used in the calcium-looping process (CaL) are important challenges. The current study explores the performance of a novel SiO2-decorated calcium-based adsorbent recovered from eggshell waste in terms of both CO2 capture capacity and fluidity. Two preparation methods of hydration and sol–gel were used to obtain Ca-based adsorbents with different pore configurations and volumes. Modification of the adsorbents was applied by dry physically mixing with different weight percentages of hydrophobic SiO2 nanoparticles (NPs), in order to maintain stability and fluidity. The adsorbent prepared by the sol–gel method exhibited a fluffier structure with smaller grain sizes and higher porosity than that of prepared by the hydration method, leading to a 6.9 % increase in conversion at the end of the 20th cycle. Also, with the optimal amount of SiO2 nanoparticles, i. e. 7.5 wt%, the amount of CaO conversion obtained by sol–gel derived adsorbent was 27.59 % higher than that by pristine eggshell at the end of the 20th carbonation/calcination cycles. The fluidizability tests showed that the highest bed expansion ratio (2.29) was achieved for sol–gel derived adsorbent in the presence of 7.5 wt% silica nanoparticles which was considerably higher than the amount of 1.8 and 1.6 belonged to sol–gel derived adsorbent and pristine eggshell without silica at the gas velocity of ≈ 6.5 cm/s, respectively. The high adsorption capacity and proper fluidity of this novel and green calcium-based adsorbent promise its wide application.

One-step preparation of efficient SiO2/PVDF membrane by sol-gel strategy for oil/water separation under harsh environments

The environmental pollution and resource loss caused by oil-water emulsion bring a severe threat to human's life. Superhydrophobic/superoleophilic membranes are considered as a wise choice for separating water-in-oil emulsions. However, the large-scale production of acid and alkali resistant, sustainable and efficient membranes remains an enormous challenge. In this study, a superhydrophobic/superoleophilic SiO2/PVDF (SP) membrane was prepared through facile sol-gel strategy in one step. Hydrophobic SiO2 nanoparticles (NPs) were modified on PVDF membrane by hydrolysis and polycondensation reaction of tetraethyl orthosilicate (TEOS) and hexadecyltrimethoxysilane (HDTMS) as precursors. The low surface energy of the hydrophobic SiO2 NPs and the micro/nano rough structures similar to the waxy protuberances of lotus leaves constructed by nano-SiO2 played a crucial role in obtaining the superhydrophobic/superoleophilic property. The water contact angle (WCA) of the optimal SP membrane reached 152.4 ± 1.4°, while the oil droplets completely permeated the membrane in 1 s. Also, the fluxes of SP membrane for petroleum ether/water, n-hexane/water, and n-heptane/water were 3886 ± 140, 3551 ± 146 and 3763 ± 57 L m−2 h−1, respectively, and the separation efficiencies were stable above 99.7%. Moreover, the SP membrane showed excellent separation effects and stability under different chemical environments. Most significantly, it also displayed anti-fouling performance like lotus leaves. The results indicated that its separation efficiency still remained above 97% after 20 cycles. Therefore, these outstanding results ensured the possibility of large-scale production and practical application of the SP membrane.

Self-Transportation of Superparamagnetic Droplets on a Magnetic Gradient Slippery Surface with On/Off Sliding Controllability.

Recently, research about droplet self-transportation on slippery surfaces has become a hotspot. However, to achieve on/off sliding control during the self-transportation process is still difficult. Herein, we report a magnetic slippery surface, and demonstrate on/off sliding control during the self-transportation of superparamagnetic droplets. The surface is prepared through integrating a substrate that has a gradient magnetic region with a layer of paraffin infused hydrophobic SiO2 nanoparticles. On the surface, a superparamagnetic droplet is pinned at room temperature (about 25 °C), while it can self-transport directionally as the temperature is increased to about 70 °C. When the temperature is cooled down again, the droplet would return to the pinned state, indicating that on/off sliding control during the self-transportation process can be achieved. Furthermore, based on the excellent controllability, controllable coalescence of two droplets from opposite direction is displayed, demonstrating its potential application in numerous areas.

D-Cysteine Functionalized Superhydrophobic Nanocomposite Coating with Multiple-Action Antibacterial Property and Enhanced Mechanical Durability

In this study, a durable superhydrophobic antibacterial coating was developed by a facile spraying method. A mixture of bisphenol A diglycidyl ether (BADGE) and hydrophobic SiO2 nanoparticles was sprayed on carbon steel to provide a superhydrophobic substrate. D-cysteine (D-cys) functionalized SiO2/dopamine/silver nanoparticles with multilayer core-shell structure were then sprayed on superhydrophobic substrate to enhance antibacterial performance. The results of morphology observation and X-ray photoelectron spectroscopy (XPS) indicated the successful preparation of antibacterial nanoparticles and presented the hierarchical micro/nanostructures of coating surface. The as-prepared coating exhibited superhydrophobicity, with the water contact angle of ~153°. The coating was endowed with good mechanical durability, which maintained the water contact angle of ~150° after 180 cycles in tape-peel tests. The results of electrochemical impedance spectroscopy showed satisfactory corrosion resistance of this coating during 3 days of immersion in 3.5% NaCl solution. Furthermore, the coating showed excellent antibacterial performances against Escherichia coli and Pseudomonas aeruginosa, which benefited from the synergistic actions of low wettability of superhydrophobic surface, bactericidal behavior of Ag nanoparticles, and biofilm inhibition effect of D-cys.

Fluorine-free superhydrophobic surface with micron-nanosized two-tiered structure for self-cleaning, anti-frosting, and anti-icing applications

Superhydrophobic surfaces with micron-nanosized two-tiered structures have huge potential in practical applications. However, the complex preparation process and low-stability of the versatile superhydrophobic surfaces restricted their wide application. Herein, a facile chemical etching process was applied to create a micron-sized rough structure on the 1060 aluminum alloy substrate, and the micron-sized rough structure surface (M-surface) was hydrophobic with a water contact angle of 113.50° ± 2.7°. Then, the M-surface was modified by hydrophobic SiO2 nanoparticles, and a superhydrophobic micron-nanosized two-tiered structure surface (MNSS-TMES/H-SiO2 coating) with a water contact angle of 161.20° ± 2.3° was constructed. The as-prepared MNSS-TMES/H-SiO2 coating can maintain superhydrophobicity after self-cleaning, sand impact, and anti-frosting tests. More importantly, the MNSS-TMES/H-SiO2 coating exhibited superior anti-icing performance and higher defrosting efficiency. The freezing delay time of a water droplet on the MNSS-TMES/H-SiO2 coating was prolonged to 4973.87 s at − 15 °C, and the frost layer on the resultant coating was melting speedily and turned into several isolated spherical water droplets in approximately 20 s. Therefore, the prepared durable fluorine-free superhydrophobic MNSS-TMES/H-SiO2 coating with self-cleaning performance, higher defrosting efficiency, and the ability to delay icing, which has great prospects in practical applications.

Designing triple-layer superhydrophobic/hydrophobic/hydrophilic nanofibrous membrane via electrohydrodynamic technique for enhanced anti-fouling and anti-wetting in wastewater treatment by membrane distillation

Developing high-performance membranes for membrane distillation (MD) to treat highly saline industrial wastewater is of great significance. In this work, a superhydrophobic/hydrophobic/hydrophilic triple-layer membrane combining an electrosprayed superhydrophobic top layer, an electrospun hydrophobic nanofibrous intermediate layer and a hydrophilic microporous membrane substrate was fabricated by using electrohydrodynamic techniques. The top superhydrophobic surface possesses a unique surface morphology composing of hydrophobic SiO2-polymer microbeads with nanoscaled protrusions and interconnected thin nanofibers, which contributed to the enhanced water flux for desalination in direct contact MD. By tuning the concentrations of hydrophobic SiO2 nanoparticles and polyvinylidene fluoride-co-hexafluoropropylene for electrospraying the top layer, the triple-layer membrane showed both enhanced anti-fouling and anti-wetting properties due to the reduced liquid-solid contact area and stable Cassie-Baxter state. The triple-layer membrane exhibited stable MD performances when using real seawater and industrial flue gas desulfurization wastewater as the feed solutions, while no obvious fouling and wetting being observed even at 60% water recovery. This study provides an effective approach for fabricating a high-performance triple-layer superhydrophobic/hydrophobic/hydrophilic membrane for potential practical MD applications for industrial wastewater treatment.

Hydrophilic/Hydrophobic SiO2 Nanoparticles Enabled Janus‐Type Paper through Commercial Glaco Spraying and Air‐Plasma Treatment

AbstractFunctional paper‐based microdevices have been receiving wide attention in the research areas of microfluidic chips, soft actuators, etc. This work introduces the design and fabrication of a Janus‐type paper in which one side of the paper remains hydrophilic and the other side is hydrophobic. Such Janus‐type paper is prepared by directly spraying hydrophobic Glaco solutions and following air plasma treatment. The former treatment can cover the paper fibers with numerous hydrophobic SiO2 nanoparticles. Through optimizing the fabrication parameters of the air plasma, it can penetrate the filter paper in a controllable depth, resulting in effectively regulating the hydrophobic particles into hydrophilic ones. Thereafter, the antirotation and interfacial stability of the Janus paper are investigated. Finally, a liquid storage and contamination‐free analysis devices are demonstrated on the Janus‐type paper platform. Noting that the commercially nonfluoride coating (Glaco) and mature plasma instrument together make the fabrication method simple, rapid, users/environmental‐friendly, and mass‐produced. The method provides a new route to fabricate Janus‐type paper for potential multifunctional applications in microfluidic chips and smart actuators, and may open up new avenue to prepare Janus films in a simple/rapid way.