Hydrophobic Silica Nanoparticles Research Articles

Scalable Jet‐Based Fabrication of PEI‐Hydrogel Particles for CO2 Capture

The capture, regeneration, and conversion of CO2 from ambient air and flue gas streams are critical aspects of mitigating global warming. Solid sorbents for CO2 absorption are very promising as they have high mass transfer areas without energy input and reduce emissions and minimize corrosion as compared to liquid sorbents. However, precisely tunable solid CO2 sorbents are difficult to produce. Here, we demonstrate the high‐throughput production of hydrogel‐based CO2‐absorbing particles via liquid jetting. By wrapping a liquid jet consisting of an aqueous solution of cross‐linkable branched polyethylenimine (PEI) with a layer of suspension containing hydrophobic silica nanoparticles, monodisperse droplets with a silica nanoparticle coating layer was formed in the air. A stable Pickering emulsion containing PEI droplets was obtained after these ejected droplets were collected in a heated oil bath. The droplets turn into mm‐sized particles after thermal curing in the bath. The diameter, PEI content, and silica content of the particles were systematically varied, and their CO2 absorption was measured as a function of time. Steam regeneration of the particles enabled cyclic testing, revealing a CO2 absorption capacity of 6.5 ± 0.5 mol kg−1 solid PEI in pure CO2 environments and 0.7 ± 0.3 mol kg−1 solid PEI for direct air capture. Several thousands of particles were produced per second at a rate of around 0.5 kg per hour, with a single nozzle. This process can be further scaled by parallelization. The complete toolbox for the design, fabrication, testing, and regeneration of functional hydrogel particles provides a powerful route toward novel solid sorbents for regenerative CO2 capture.

Intelligent responsive self-assembled micro-nanocapsules: Used to delay gel gelation time

In the application of polymer gels to profile control and water shutoff, the gelation time will directly determine whether the gel can “go further” in the formation, but the most of the methods for delaying gel gelation time are complicated or have low responsiveness. There is an urgent need for an effective method for delaying gel gelation time with intelligent response. Inspired by the slow-release effect of drug capsules, this paper uses the self-assembly effect of gas-phase hydrophobic SiO2 in aqueous solution as a capsule to prepare an intelligent responsive self-assembled micro-nanocapsules. The capsule slowly releases the cross-linking agent under the stimulation of external conditions such as temperature and pH value, thus delaying gel gelation time. When the pH value is 2 and the concentration of gas-phase hydrophobic SiO2 particles is 10%, the gelation time of the capsule gel system at 30, 60, 90, and 120 °C is 12.5, 13.2, 15.2, and 21.1 times longer than that of the gel system without containing capsule, respectively. Compared with other methods, the yield stress of the gel without containing capsules was 78 Pa, and the yield stress after the addition of capsules was 322 Pa. The intelligent responsive self-assembled micro-nanocapsules prepared by gas-phase hydrophobic silica nanoparticles can not only delay the gel gelation time, but also increase the gel strength. The slow release of cross-linking agent from capsule provides an effective method for prolongating the gelation time of polymer gels.

Design of fluorine-free superhydrophobic silk fabrics with mechanical durability and self-cleaning properties for oil-water separation

The separation of oil and water can be effectively addressed through the application of superhydrophobic coatings. This method, known for enhancing the self-cleaning, anti-corrosive, and friction-reducing properties of materials, typically employs fluorine reagents to ensure the durability of the coating nanostructure. However, the use of fluorine reagents raises concerns related to health and the environment. We present a straightforward and efficient approach to fabricate a robust, fluorine-free superhydrophobic composite coating. The coating solution, comprised of hydrophobic silica nanoparticles and polydimethylsiloxane (PDMS), is formed through sonication. The resulting superhydrophobic coating is effortlessly applied to silk fabric through immersion and subsequent drying/curing. micrograph confirms the creation of porous micro/nanostructures on the silk fabric's surface. Exceptional superhydrophobicity is demonstrated with a water contact angle (WCA) of 161 °±1.5 ° and a small sliding angle (SA) of 5 °±0.5 °. The coating's firmness, durability, and UV resistance are assessed through 20 cycles of sandpaper friction (load 200 g) and repeated tape peeling tests. Furthermore, the modified silk fabrics exhibit excellent capabilities in oil-water separation. This fluorine-free superhydrophobic coating, characterized by its robustness, environmental friendliness, and ease of manufacture, holds promising applications in the textile industry.

Study on the hydrophobic nano silica particles as flow-enhancing additives for ultrafine dry powder fire extinguishing agent

Sodium bicarbonate-based ultrafine dry powder fire extinguishing agents (UDEAs) exhibit high hygroscopicity and a tendency to agglomerate, which result in poor flowability and diminished extinguishing efficiency, thus proving to be crucial concerns in the UDEA design. The integration of hydrophobic nano silica (HNS) has been recognized as an effective strategy to tackle these challenges, but the precise optimal quantity of HNS in UDEA has been a subject of confusion. Consequently, the impact of HNS as an additive on the flowability of sodium bicarbonate UDEA was thoroughly examined. Through high-speed stirring, the surface of UDEA was evenly coated with HNS particles, resulting in a notable increase in the contact angle of the modified extinguishing agent to approximately 135.4°. Notably, the UDEA formulation with an 8% HNS addition exhibited the least cohesion, the highest flow function value, and the lowest spray resistance. Moreover, the study unveiled the underlying flow mechanism of sodium bicarbonate UDEA influenced by the HNS additive. The findings indicated that the most effective incorporation of HNS into sodium bicarbonate UDEA was 8%, considering both its hydrophobic properties and flow characteristics.

Hydrophobically modified nano‐SiO2 in situ loaded on polyurethane foam as a potential carrier for marine oil spill

AbstractIn order to enhance the oil–water separation properties of polyurethane foam (PFU), hydrophobic silica nanoparticles (H‐SiO2 NPs) were firstly prepared by incorporating long alkyl chains into silica nanoparticles, and then, it was combined with PFU by in situ loading to fabricate a hydrophobic PFU (H‐SiO2 NPs/PUF). When the loading amount of H‐SiO2 NPs was 10%, the water contact angle of the modified foam H‐SiO2 NPs/PUF‐10 reached 147 ± 1°, which proved it was highly hydrophobic. The elongation at break of the foam was increased by 202%, which indicated that it had better resilience and recyclability. In addition, the total pore area and porosity were increased to 16.24 m2/g and 88.43% from 5.46 m2/g and 2.11%, which provided more storage space for adsorption. The oil–water separation experiment showed that the adsorption capacity for most light oils was 11–13 g/g, and that for dichloromethane was as high as 40.5 g/g. After 10 adsorption–desorption cycles, the adsorption capacity only decreased from 15.6 to 14.5 g/g, which was still 93% of the initial adsorption capacity. H‐SiO2 NPs/PUF represents good adsorption capacity, recyclability, and recyclability, so it as a carrier has a potential application in the treatment of marine oil spills.

Kinetic promotion of gas hydrate formations using dispersions

CO2 hydrate has promising applications like carbon capture and storage (CCS). However, the slow formation kinetics hinders these large-scale applications. Dry water, a water-in-gas dispersion stabilized by a Pickering agent (usually partially hydrophobized silica nanoparticles) has been used to enhance CO2 hydrate formation kinetics by massively increasing the water – gas interfacial area for a given volume of water. We investigated CO2 hydrate nucleation and crystal growth kinetics in dry water in the presence of sodium dodecyl sulfate (SDS) and seven water-insoluble nucleation promoters. Doping a small amount of nucleation promoters did not ruin the stability of dry water or weaken the promoting effect of dry water on CO2 hydrate nucleation kinetics. Dispersing water in CO2 as dry water promoted hydrate nucleation kinetics and doping of the additives promoted hydrate crystal growth kinetics. This synergistic effect could be utilized to store more CO2 in a hydrate form at a faster rate.

Investigation of the interfacial phenomena in the presence of nonionic surfactants and a silica nanoparticle at the n-decane-water interface: Insights from molecular dynamics simulation

In chemical enhanced oil recovery (EOR), the nanoparticles can be employed as conveyors to transfer the surfactants and impede the reduction of surfactant concentration. Here, a set of molecular dynamic simulations were carried out to examine the ability of hydrophobic silica nanoparticle (NP) to deliver the nonionic surfactant (Triethylene glycol monododecyl ether; C12E3) into the n-decane-water interface. Another set of simulations in which only surfactant molecules are initially located at the interface was performed in order to better characterize the influence of NP on the surfactant adsorption film.The NP exhibited high efficiency in delivering surfactant molecules to the n-decane-water interface. In addition, for the C12E3-NP and n-decane-NP, the Coulombic interactions are weaker than the van der Waals interactions confirming the nonpolar property of the silica nanoparticle. The density profiles indicate that as the concentration of surfactants increases at the interface, NP separates more from the surfactant layer. The interfacial tension (IFT) of n-decane-water systems containing only surfactants decreases as the surface coverage of the surfactants increases. Moreover, it was also proved that the intrinsic width of the interface increases with an increment in the surface coverage of surfactants. The surfactant molecules exhibit a great tendency to contribute as acceptors to the formation of hydrogen bonds with water molecules. With an increment in the surface coverage of surfactant molecules, the 2D radial distribution functions between the centers of mass (COMs) of surfactant tails show oscillations. Appeared oscillations represent the correlation between the surfactant tails. Presence of NP causes the oscillations start at lower surfactant coverage than without NP. The surfactant tails choose a random distribution at the low surface coverage of surfactants. In addition, they tend to be oriented partially perpendicular to the interface with an increase in surfactant surface coverage. Besides, NP causes the surfactant tails to orient more perpendicular to the interface than surfactants alone.

Robust Superhydrophobicity through Surface Defects from Laser Powder Bed Fusion Additive Manufacturing.

The robustness of superhydrophobic objects conflicts with both the inevitable introduction of fragile micro/nanoscale surfaces and three-dimensional (3D) complex structures. The popular metal 3D printing technology can manufacture robust metal 3D complex components, but the hydrophily and mass surface defects restrict its diverse application. Herein, we proposed a strategy that takes the inherent ridges and grooves' surface defects from laser powder bed fusion additive manufacturing (LPBF-AM), a metal 3D printing process, as storage spaces for hydrophobic silica (HS) nanoparticles to obtain superhydrophobic capacity and superior robustness. The HS nanoparticles stored in the grooves among the laser-melted tracks serve as the hydrophobic guests, while the ridges' metal network provides the mechanical strength, leading to robust superhydrophobic objects with desired 3D structures. Moreover, HS nanoparticles coated on the LPBF-AM-printed surface can inhibit corrosion behavior caused by surface defects. It was found that LPBF-AM-printed objects with HS nanoparticles retained superior hydrophobicity after 150 abrasion cycles (~12.5 KPa) or 50 cycles (~37.5 KPa). Furthermore, LPBF-AM-printed ships with superhydrophobic coating maintained great water repellency even after 10,000 cycles of seawater swashing, preventing dynamic corrosion upon surfaces. Our proposed strategy, therefore, provides a low-cost, highly efficient, and robust superhydrophobic coating, which is applicable to metal 3D architectures toward corrosion-resistant requirements.

Phase behavior-microstructure-crystallization kinetics correlations in semi-crystalline/amorphous PCL/SAN mixtures filled with nanosilica

In this study, the effects of poly(ε-caprolactone) (PCL) molecular weight and the type and presence of nanosilica on the non-isothermal crystallization behavior of PCL in the PCL/poly(styrene-co-acrylonitrile) (SAN)/nanosilica systems have been quantitatively investigated. The PCL/SAN system have been chosen as an ideal model system because of the special phase behavior of the blends, which include a lower-critical solution temperature (LCST) phase diagram over a virtual upper-critical solution temperature. By this choose, the great importance of phase separation, mutual phase dissolution and preferential nanoparticle migration to one of the polymeric phases on the crystallization behavior during a commercial production process has been highlighted. The addition of both hydrophilic (Si) and hydrophobic (SiR) silica nanoparticles to virgin PCLs with different molecular weights retards the crystallization process. However, the presence of these nanoparticles in PCL/SAN blends impacts the PCL crystallization kinetics in opposite ways, depending on the nanosilica type, PCL molecular weight and melt cooling rate. The reasons for the observed opposite trends are the changes in the LCST-type phase diagram position by altering the PCL molecular weight and nanosilica type, the selective migration of nanoparticles as well as the dispersion state of nanofillers. The presence of both Si and SiR nanosilicas increases the crystallization activation energy, respectively, by 4.2% and 2.4% for the PCL/SAN blend conatining the PCL with lower molecular weight. While the addition of both Si (11%) and SiR (6.7%) reduces this energy for the blend conatining the PCL with higher molecular weight.

Enhancement of antibacterial and wound healing capabilities of cotton fabric through the covalent bonding of antibiotic-loaded hydrophobized mesoporous silica nanoparticles

Wound dressings are highly desirable for mitigating pathogenic bacterial infections. Sterilized cotton fabric is a widely used medical dressing, facilitating wound healing, mitigating pathogenic infections, and reducing treatment expenses. Nevertheless, untreated cotton fabric lacks intrinsic antibacterial properties. In this study, we introduced antibiotics-loaded aminopropyl and octadecyl grafted mesoporous silica nanoparticles onto the surface of hydrophobized cotton fabric. The obtained wound dressing exhibited remarkable antibacterial efficacy against Escherichia coli and Staphylococcus aureus through sustained antibiotic release. In vivo assessments verified that this intelligent cotton fabric dressing accelerates wound healing and prevents adhesion to skin tissues. Additionally, the reusability, hydrophobic nature, and straightforward synthesis methodology collectively provide an alternative solution to smart wound dressings for biomedical applications.© 2014 xxxxxxxx. Hosting by Elsevier B.V. All rights reserved.

Development of self-cleaning superhydrophobic cotton fabric through silica/PDMS composite coating

The lotus effect informs that self-cleaning superhydrophobic surfaces can be obtained by creating rough surface structures and modifying them with chemicals that have low surface energy. Herein, the composite of hydrophobic silica nanoparticles (SNPs) and polydimethylsiloxane (PDMS) was deposited on cotton fabric by multiple dip cycles. At optimal condition, the agglomerated SNPs in PDMS produces a hierarchical rough surface, as a result the coated cotton fabric has revealed a water contact angle (WCA) of 158.41 ± 1.58° and 4° of sliding angle. Due to negligible water adhesion to a superhydrophobic surface, coated cotton fabric reveals excellent self-cleaning behavior, which was tested by dust particles, muddy water and tea droplets. Furthermore, coated cotton fabric sustains superhydrophobicity over the mechanical robustness tests including adhesive tape peeling test, sandpaper abrasion test, and ultrasonication. Therefore, such an approach may be applicable in textile industries for self-cleaning purposes.

Evaluating the Influence of Hydrophobic Nano-Silica on Cement Mixtures for Corrosion-Resistant Concrete in Green Building and Sustainable Urban Development

The use of hydrophobic nano-silica particles in concrete for improved corrosion resistance and durability has been explored in recent years, and its potential impact on sustainable urban development and green building practices has been studied. The impact of substituting hydrophobic nano-silica particles for 2% of the cement weight in high-strength concrete mixes was investigated in this research. The study focuses on evaluating the physical-mechanical properties, including compressive strength, tensile strength, modulus of elasticity, and Poisson’s ratio. Additionally, the influence of these mixes on corrosion resistance is examined. The concrete designs feature a high strength of 42 MPa, and the hydrophilic nano-silica particles undergo functionalization processes to obtain hydrophobic properties. Contact angle measurements and water absorption tests confirm the hydrophobicity of the material. Physical, electrochemical, and electrical tests were conducted to determine the corrosion resistance contribution of the nano-silica particles when substituted at 2% of the cement weight. The research findings reveal that concrete containing nano-silica particles demonstrates improved physical-mechanical properties compared to other mixes. Incorporating nano-silica enhances concrete by accelerating hydration, increasing early-age strength, and providing hydrophobicity, resulting in improved physical-mechanical properties over other mixes. However, it was observed that the addition of hydrophobic and non-hydrophobic nano-silica tends to reduce corrosion resistance compared to concrete without these particles, despite exhibiting greater compactness. This suggests a direct influence of nano-silica on the corrosion phenomenon.

Puncture Resistance and UV aging of Nanoparticle-Loaded Waterborne Polyurethane-Coated Polyester Textiles.

The goal of this research was to investigate the effect of different types of nanoparticles on the UV weathering resistance of polyurethane (PU) treatment in polyester-based fabrics. In this regard, zinc oxide nanoparticles (ZnO), hydrophilic silica nanoparticles (SiO2 (200)), hydrophobic silica nanoparticles (SiO2 (R812)), and carbon nanotubes (CNT) were mixed into a waterborne polyurethane dispersion and impregnated into textile samples. The puncturing resistance of the developed specimens was examined before and after UV-accelerated aging. The changes in chemical structure and surface appearance in nanoparticle-containing systems and after UV treatments were documented using microscopic pictures and infrared spectroscopy (in attenuated total reflectance mode). Polyurethane impregnation significantly enhanced the puncturing strength of the neat fabric and reduced the textile's ability to be deformed. However, after UV aging, mechanical performance was reduced both in the neat and PU-impregnated specimens. After UV treatment, the average puncture strength of all nanoparticle-containing systems was always greater than that of aged fabrics impregnated with PU alone. In all cases, infrared spectroscopy revealed some slight differences in the absorbance intensity of characteristic peaks for polyurethane polymer in specimens before and after UV rays, which could be related to probable degradation effects.

Fabrication and characterization of hydrophobic/hydrophilic dual-layer polyphenyl sulfone Janus membrane for application in direct contact membrane distillation

In this study, single-layer (SL) and dual-layer (DL) polyphenyl sulfone (PPSU) flat sheet nanocomposite Janus membranes were fabricated via a combination of VIPS and NIPS techniques for direct contact membrane distillation (DCMD) for the first time. Hydrophobic silica nanoparticles (SiNP-B) were incorporated into the SL membranes and the top layer of the DL membranes, while hydrophilic silica nanoparticles (SiNP-L) were added into the down layer of the DL membranes. The effect of the SiNP-B concentration (1–5 wt%) and the top layer thickness (50 and 100 μm) on the morphology, mean pore size (MPS), thickness, porosity, surface roughness, water contact angle (WCA), liquid entry pressure, mechanical strength, and thermal conductivity were investigated. All of the membranes showed a finger-like structure surrounded by a sponge-like structure. The membranes were examined in the DCMD of a 35,000 ppm saline solution at different feed temperatures (50–70 °C) and flow rates (250–1000 mL/min). The DL membranes possessed higher fluxes than the SL membranes through increasing MPS and WCA. The DL membrane with a SiNP-B concentration of 2 wt% and a hydrophobic thickness of 50 μm (DL- 2,50) achieved the highest flux (42.68 ± 0.35 kg/m2h) and salt rejection (94.90 %) during 5 h. This membrane has an MPS of 0.22 ± 0.03 μm, a thickness of 201 ± 4 μm, and a porosity of 76 ± 2 %. It could be concluded the proper pore size distribution is the most important factor in achieving a successful DCMD operation.

In Ukrainian

Efficient and environmentally friendly means for fire extinguishing can reduce extreme economic losses from fires and protect people's lives and property. A separate problem is extinguishing oil products on the water surface. Dry water is a new type of environmentally friendly fire extinguishing agent. It is a powder with a water content of more than 90 %, so it has excellent fire extinguishing properties. The purpose of this work was to obtain dry water fire extinguishing powders based on pyrogenic hydrophobic methyl silica with bentonite and to study their fire extinguishing properties in case of extinguishing gasoline on water surface. To obtain dry water fire extinguishing powders, there were used distilled water, Dashukovsky bentonite (Ukraine), and pyrogenic methyl silica (AM-300 brand, Ssp = 300 m2/g, particle size 5–7 nm) (Kalush, Ukraine). Dry water fire extinguishing powder was prepared by mixing the components at a speed of 15000 rpm for 10 s. Were made samples containing 10 wt. % methyl silica, 3, 6, 10, and 15 wt. % bentonite and the corresponding amount of water. The bulk density was 0.423, 0.453, 0.459, and 0.464 g/cm3 for samples of 3, 6, 10, and 15 wt. % bentonite, respectively. Optical microscopy has shown that the particles of the dry water powder have a clearly visible core-shell structure. Dry water fire extinguishing powder is a polydisperse system - most of the particles are single fine particles with a size of 1 micron or less, and there are also agglomerates with a size of more than 5 microns. As a result of the mechanical destruction of individual bentonite particles during high-speed mixing of components, bentonite particles are destroyed, therefore, individual bentonite particles are surrounded by a hydrophobic-hydrophilic mixture of hydrophobic silica nanoparticles and bentonite nanoparticles formed during exfoliation. The study of the fire-extinguishing properties of the dry water powder was carried out by spraying it onto a layer of burning gasoline A92 on water surface. The time to complete extinguishing of the fire and the consumption of the substance per unit area of burning were determined. It has been determined that the time for extinguishing gasoline and the consumption of dry water fire extinguishing powder for extinguishing it depend on the concentration of bentonite and are for 3, 6, 10, and 15 wt. % 9, 7, 6, and 9 s and 0.333, 0.309, 0.284, and 0.260 g/cm3, respectively. The developed dry water fire extinguishing powders are environmentally friendly, have good fire extinguishing properties, and can be used to extinguish oil products on the surface of water bodies.

Enhancing saline water evaporation rates via floatable, conductive nanoparticles embedded in superhydrophobic cotton gauze at air-water interface

A significant portion of the earth's surface is composed of water, and all breathing organisms require freshwater to survive. Unfortunately, most of the water on earth's surface is saltwater, not freshwater, and very soon, freshwater will become short in supply in many locations. The principles of water evaporation for saltwater desalination play a crucial role in solving this crisis using renewable resources. Even though the implementation of this solution is hindered by several challenges, such as the delicate nature of solar thermal devices, intricate fabrication methods, and the high cost associated with these devices. This study demonstrates a model for enhancing saline water evaporation rates with an affordable and energy-efficient approach using floatable superhydrophobic cotton gauze with conductive nanoparticle inclusions. The fabrication process of the floatable superhydrophobic cotton gauze involves a multi-step process that begins with the application of spray coating a double layer of base coat homogenized with conductive nanoparticles—carbon black, pristine graphene, and carbon nanotubes (CNTs) and a subsequent layer with hydrophobic silica nanoparticles on cotton gauze, making the conductive nanoparticle-embedded superhydrophobic cotton gauze. This results in the cotton gauze floating on the air-water interface. The next step involves exposing the air-water interface to simulated solar infrared (IR) light, which has a power of 125 W and a light density of approximately 440 W/m2. In this study, the base coat layer adhesives were homogenized with 0.05 %, 0.1 %, and 0.5 % of conductive nanoparticles. As a result of this process, the whole incident light is converted into heat at the air-water interface of different types of base fluid, including saltwater, tap water, and deionized (DI) water. The water evaporation tests were carried out to assess the effectiveness of the air-water interface heating and evaluate its ability to transform light into heat under ambient pressure. Test results indicated that 0.1 % of carbon black, graphene, and CNT nanoparticle-embedded superhydrophobic cotton gauze offered superior water evaporation results than 0.05 % and 0.5 % of the same nanoparticles. The evaporation rate of saltwater is significantly improved by over 7.73 % when using 0.1 % of carbon black nanoparticles embedded in superhydrophobic cotton gauze. The temperature of the superhydrophobic cotton gauze, which contains 0.1 % of carbon black nanoparticles, increased from 18.5 °C to 72.8 °C during the evaporation process. This results in an evaporation rate of 4.4 mg/h.cm2, demonstrating the effectiveness of 0.1 % of carbon black nanoparticle-embedded superhydrophobic cotton gauze in enhancing the water evaporation rate. The higher temperature at the air-water interface, instead of heating the bulk quantity of the saltwater was exhibited in the floatable conductive nanoparticle-embedded superhydrophobic cotton gauze, providing a possible explanation for the enhanced evaporation and freshwater productions.

Design and fabrication of silicone-silica nanocomposites airway stent

Introduction: Due to the COVID-19 pandemic in recent years, many patients after extubation had stenosis in all tracheal areas because of long-term intubation. Therefore, tracheal stenosis in these patients is benign and can be treated using silicone stents, and many patients need silicone stents during recovery. A silicone stent is an artificial support that plays a significant role in managing airway obstruction.Methods: This research aims to fabricate an optimal silicone stent reinforced with Nanosilica by vacuumed injection molding. Materials-based nanocomposites are made of rtv2 silicone with 1wt%, 3wt%, and 5wt% of hydrophilic and hydrophobic Nanosilica particles. Hardness, tensile, and hydrophobicity properties have been performed for the experimental characterization of the nanocomposites.Results and Discussion: The uniform distribution of nanoparticles in the silicone matrix has been confirmed using SEM images. Adding Nano-silica increases hardness and tensile strength and improves the silicone matrix’s mechanical properties. Also, the addition of nanoparticles changes the surface hydrophobicity properties and roughness. Although the presence of nanoparticles improves the mechanical properties, it also reduces the transparency and increases the viscosity. Our results show that adding 1wt%. Hydrophobic Nano-silica improves nanocomposites’ mechanical properties and preserves transparency and viscosity (mold-ability) for stent construction. Adding 3wt%. Hydrophilic Nano-silica improves mechanical and hydrophobic properties, but moldability is not easy. Finally, the fabricated nanocomposite airway stents were successfully placed on the sheep trachea in the pilot animal study.

Facile fabrication of extreme-wettability contrast surfaces for efficient water harvesting using hydrophilic and hydrophobic silica nanoparticles

Freshwater shortages threaten ecosystems and human communities around the world. Inspired by the ability of cacti and desert beetles to collect water from the atmosphere, we successfully fabricated a wettability contrast surface with efficient water harvesting using a simple and low-cost process. A solution of isopropyl alcohol and a mixture of hydrophobic and hydrophilic silica nanoparticles was sprayed on a laminating film of ethylene vinyl acetate and polyethylene terephthalate, after which sandpaper was laid on the dry-coated film for hot-press lamination. After peeling the film from the sandpaper, the fabricated surface exhibited random wettability contrast patterns with nano-microstructures formed by nanoparticles and the sandpaper surface. The highest water-harvesting efficiency of the prepared surface was approximately 446.7 mg/cm2/h when the mass ratio of the hydrophobic to hydrophilic silica nanoparticles in the spraying solution was 75/25 due to the optimal performance between the generation of water nucleation, coalescence, and the movement of water droplets. An analysis of the effect of ultraviolet irradiation and adhesive damage on the surface revealed that the efficiency of water collection was nearly unchanged in the face of the ultraviolet irradiation and decreased slightly after the tape test. The proposed fabrication method can make flexible and wettable contrast surfaces at large scales and low costs. In addition, superhydrophobic, or nearly superhydrophilic surfaces can be fabricated with the same process by using solely hydrophobic or hydrophilic silica nanoparticles. Therefore, this process is versatile and can be applied for creating surfaces with a range of wettability properties.

Transparent and superhydrophobic room temperature vulcanized (RTV) polysiloxane coatings loaded with different hydrophobic silica nanoparticles with self-cleaning characteristics

Superhydrophobic coatings based on room temperature vulcanized (RTV) polysiloxane matrix loaded with organically modified silica (ORMOSIL) nanoparticles were successfully prepared using the cost-effective and scalable one-step spraying coating approach. ORMOSIL nanoparticles were prepared by sol-gel treatment at ambient conditions through the reaction between the commercial hydrophilic silica (R200) and octyl-triethoxysilane (R200.OTS), (1H,1H,2H,2H-nonafluorohexyl)-triethoxysilane (R200.NFS) and a mixture of both (R200.OTS/NFS). The functionalization of the silica was followed by Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). Commercial hydrophobic silica particles functionalized with siloxane (R202) and octyl-silane (R805) were also used for comparison. The presence of 20 % of R202 and R200.NFS resulted in coatings with water contact angle (WCA) higher than 160°, sliding angle <5°, high transparency and an effective self-cleaning behavior. Increasing the amount of nanoparticles increased the superhydrophobic response but the translucence decreased. Coatings containing R200.OTS particles presented high translucence and high WCA, but the sliding angle was also high, which limits their use as self-cleaning material.

Thermodynamically-equilibrium LCST phase diagram of PCL/SAN mixtures determined by thermal analysis: Opposing effects of hydrophilic and hydrophobic silica nanoparticles

In this work, the isothermal crystallization kinetics of PCL in PCL/SAN blend and PCL/SAN/nanosilica nanocomposite systems has been applied as a useful and sensitive variable for determining the LCST phase diagram. By eliminating the impacts of kinetic variables, the variations in the equilibrium LCST phase boundary of PCL/SAN mixtures were evaluated. The presence of hydrophobic nanoparticles shifted the equilibrium LCST phase diagram to higher temperatures as expected owing to the compatibilization effect of nanoparticles, while the hydrophilic nanoparticles shifted it to lower temperature. The preferential migration of hydrophilic nanosilica into SAN-rich phase with slower molecular dynamics caused larger viscoelastic asymmetry of polymeric phases and consequently, lower area of phase miscibility window. In contrast, the addition of hydrophobic nanosilica with better dispersion state and no preferential localization in PCL/SAN blend resulted in a shift of LCST phase diagram to higher temperatures.