Rough Silica Research Articles

Ice-grain impact on a rough amorphous silica surface

Ice-grain impact on a rough amorphous silica surface

Dual-stimuli-responsive silica-based emamectin benzoate nanodelivery system for effective control of Spodoptera frugiperda and safety assessment toward Microplitis manilae

The utilization of highly efficient and ecofriendly stimulus-responsive delivery systems for pesticides represents a powerful strategy for enhancing their efficacy and environmental safety. In this study, the application of emamectin benzoate (EB)-loaded amino-functionalized rough mesoporous silica (KMSNs)@poly(glycidyl methacrylate-co-acrylic acid) (PMA) composites (KMSNs@PMA@EB, 6.52 % loading capacity for EB) to control efficacy for Spodoptera frugiperda was investigated in detail. The results showed that, KMSNs@PMA@EB rapidly released EB under acidic and high-temperature conditions. compared with EB and commercial formulations, a solution of KMSNs@PMA@EB with the agricultural organosilicon additive exhibited excellent wetting. Compared with MSNs, KMSNs@PMA significantly enhanced the effective deposition. Moreover, the photostability of KMSNs@PMA@EB was improved by 1.87-fold and 2.25-fold compared to EB and an EB suspension concentrate (EB SC). S. frugiperda larvae preferred corn leaves with low concentrations (0.125 mg/L) of KMSNs@PMA@EB than EB-treated. Bioassays revealed that KMSNs@PMA@EB maintained > 37 % control efficiency after 21 d of spraying, KMSNs@PMA@EB exhibited significantly greater insecticidal activity and persistence against S. frugiperda than commercial formulations. After 21 days of application, the final deposition rates of KMSNs@PMA@EB were lower than the maximum residual limit of EB, spraying KMSNs@PMA@EB has a lower impact on corn plants. Furthermore, biological safety assessments confirmed that KMSNs@PMA@EB did not affect the maize seed germination and growth and posed a low risk to Microplitis manilae. Those results highlight that the advantages of KMSNs@PMA@EB nanoparticles multidimensional enhancement of pesticide efficacy, persistence, and safety to parasitic wasps and has great potential to be used in pest control combining parasitoid and nanopesticides.

Mechanical, fracture, and environmental performance of greener polymer composites containing low to high micro fillers with recycled and byproduct origins

AbstractPolymer adhesives have considerable mechanical and environmental privileges; however, their high price makes them uncommercial for common uses. This study investigates the incorporation of recycled or byproduct fillers in epoxy resin‐based composites to assess their mechanical properties, environmental impacts, and cost efficiency. The fillers examined include fly ash, glass powder, slag, silica powder, and limestone powder. Tensile, compressive, and fracture tests were conducted on composites with various filler proportions (0%–80% by weight). From microstructure observations, round (fly ash, glass powder) and rough (slag, silica, and limestone powder) morphologies are seen. Also, it is seen that all the fillers are well distributed in the matrix; with the increase of filler content, the air voids increase. The tensile and compressive results indicate that adding fillers improves the composite's strengths, with up to a 20% increase compared to neat epoxy resin. However, when filler contents exceed 40%, the strengths decrease. Fracture toughness values also decrease with increasing filler content. Comparing the results with those of other studies indicates the similarity of trends. Cost‐strength and CO2eq‐strength curves were evaluated to assess the financial and environmental aspects. The composites show potential for cost efficiency but may have some environmental drawbacks compared to traditional construction materials like cement concrete.Highlights The incorporation of recycled or byproduct fillers in epoxy resin composites. Examined fillers include fly ash, glass, slag, silica, and limestone powder. Tensile, compressive, flexural, and fracture tests were conducted. SEM and failure patterns were analyzed, and similar studies were compared. Cost‐strength and CO2eq‐strength data evaluated.

PH-responsive interface conversion efficient oral drug delivery platform for alleviating inflammatory bowel disease.

A key challenge for the effective treatment of intestinal diseases, including inflammatory bowel disease (IBD), is to develop an oral drug delivery system that can resist gastric acid erosion and efficiently release drugs after rapid entry into the intestine. In the present work, we developed oral composite nanoparticles (MSZ@PRHS) consisting of a rough mesoporous silica (RHS) loaded with Mesalazine (MSZ) and a CAP polymer membrane for targeted relief of inflammation in colitis. At the pH values of the simulated stomach and small intestine, the release rate of MSZ from MSZ@PRHS was low, while at the pH values of the simulated colon, the release rate of MSZ was high. In dextran sulfate sodium salt (DSS)-induced acute colitis mouse model, compared with oral administration of the drug Mesalazine in the equivalent solution form, oral administration of PRHS loaded with drug-loaded nanoparticles can significantly alleviate the symptoms of inflammatory bowel disease, and improve the therapeutic effect. We propose that the intestinal microenvironment provides an interface for nanocomposites switch and a promising drug delivery platform for the management and treatment of many intestinal diseases, where controlled drug release and prolonged residence time are required.

Toughening colloidal gels using rough building blocks

Colloidal gels, commonly used as mesoporous intermediates or functional materials, suffer from brittleness, often showing small yield strains on the order of 1% or less for gelled colloidal suspensions. The short-range adhesive forces in most such gels are central forces—combined with the smooth morphology of particles, the resistance to yielding and shear-induced restructuring is limited. In this study, we propose an innovative approach to improve colloidal gels by introducing surface roughness to the particles to change the yield strain, giving rise to non-central interactions. To elucidate the effects of particle roughness on gel properties, we prepared thermoreversible gels made from rough or smooth silica particles using a reliable click-like-chemistry-based surface grafting technique. Rheological and optical characterization revealed that rough particle gels exhibit enhanced toughness and self-healing properties. These remarkable properties can be utilized in various applications, such as xerogel fabrication and high-fidelity extrusion 3D-printing, as we demonstrate in this study.

Study on the mechanical mechanism of dynamic wetting of sodium dodecyl sulfonate solutions containing inorganic salt additives

Wettability is an important factor that influences surfactant oil displacement efficiency, where surfactant solutions wet rock surfaces better and have lower interfacial tensions with crude oil, thus enhancing the oil recovery rate. Therefore, understanding the wetting of rock surfaces and selecting suitable surfactant solutions are essential for enhanced oil recovery. In this paper, a self-built system to measure the lateral friction at solid and liquid interfaces was established, and the effects of different types and concentrations of inorganic salt additives on the dynamic wettability of the surfactant solution on the solid surface were studied. A rough silica surface was used to simulate the reservoir environment, and methylene chloride was used as the simulation oil. The experimental results show that when the concentration of sodium dodecyl sulfonate is lower than the critical micelle concentration, the inorganic salt additives (NaCl, Na2SO4, and KCl) affect the surface tension, contact angle, and lateral friction of the solution. As the concentration of the inorganic salt additives increased, the surface tension and contact angle of the solution continuously decreased, the lateral friction of the solution on the simulated silica surface increased, and the wettability of the surfactant solution on the solid surface improved.

Simulation on oily contamination removal by ozone using molecular dynamics

Ozone (O3) is characteristic of high oxidative activity. It displays a high potential value in sterilization and decontamination. Although O3 has been widely investigated for its efficiency and environmentally friendly effectiveness, the fundamental issue regarding the complicated microscopic interaction mechanism between O3 and contaminant molecules remains largely unaddressed. We addressed this knowledge gap through molecular dynamics (MD) simulation at the molecular scale. Results indicated that five representative hydrocarbon molecules (n-hexadecane, phytane, terpane, naphthalin and acenaphthylene) on a rough silica (SiO2) surface were almost removed after about 300 ps simulation. And the aromatic molecules were easier to be removed than aliphatic ones. The hydroxyl oxidation reaction was demonstrated as a predominant mechanism. As the large dose of O3 was supplied by atmospheric air dielectric barrier discharge (DBD) plasma, this work provided an important theoretical reference for better using plasma technology for oily contaminant removal.

Highly Effective Lead Ion Adsorption by Manganese-Dioxide-Supported Core-Shell Structured Magnetite

In this research, a magnetic core-shell composite, consisting of a Fe3O4 core and a silica shell (called Fe3O4@SiO2), was developed and then functionalized via MnO2 grafting at different MnO2 deposition levels (termed Fe3O4@SiO2-MnO2). The resulting materials were characterized by X-ray fluorescence, X-ray diffraction, a vibration sample magnetometer, transmission electron microscopy, N2 adsorption-desorption, zeta-potential studies and X-ray photoelectron spectroscopy. Visualizations showed that Fe3O4@SiO2-MnO2 had a magnetite core with size of 100 nm, overlaid by a rough silica shell and a relatively loose MnO2 deposition. The Pb(II) adsorption onto the composites was also assessed. It was found that MnO2 deposition on the Fe3O4@SiO2 surface enhanced Pb(II) adsorption, and the Pb(II) adsorption amount was highly correlated to the MnO2 deposition level. The adsorption kinetics of Pb(II) followed pseudo-second-order kinetics, and the adsorption rate could be decreased by increasing the initial concentration of Pb(II). A higher pH resulted in enhanced Pb(II) adsorption, which slightly increased with the coexistence of Na+ and Ca2+, along with the presence of dissolved humic acid. The adsorbent could easily be separated and recovered under the action of the external magnetic component and it displayed stable adsorption behaviour over four adsorption-desorption periods. The results emphasize the high potential of Fe3O4@SiO2-MnO2 materials for the adsorptive removal of Pb(II) in water.

Omniphobic membrane via bioinspired silicification for the treatment of RO concentrate by membrane distillation

Membrane distillation (MD) is promising for the reclamation of reverse osmosis (RO) concentrate ascribed to the advantages of moderate membrane fouling, space-saving and theoretical 100% rejection to non-volatile substances. However, wetting issues remain great challenges for the hydrophobic porous membrane in the treatment of industrial wastewater by MD. In this study, a novel omniphobic membrane is developed via bioinspired silicification and fluorosilanization. The effects of polydopamine/polyethylenimine (PDA/PEI) co-deposition and silicification time on the morphology, pore structure, wettability and separation performance of the membrane are systematically investigated. The results show that the membrane surface is evenly covered by a rough silica layer after bioinspired silicification. The omniphobic membrane exhibits excellent anti-wetting properties with high liquid entry pressure (326.4 kPa) and contact angles to liquids with various surface tensions such as water (162.50°), diiodomethane (149.20°), mineral oil (135.97°), etc. The omniphobic modification has little effect on the pore structure but increases the mechanical strength of membranes significantly. The MD operation results reveal that the virgin membrane is rapidly wetted by a feed solution of 0.1 mM sodium dodecyl sulfate (SDS) in 35 g/L NaCl, while the omniphobic membranes maintain stable MD performance over a 420 min operation against the feed with a SDS concentration of up to 0.3 mM. The omniphobic membrane shows a superior separation performance in the treatment of RO concentrates from dyeing and printing industry without wetting and fouling observed. Meanwhile, high rejections to salts, SDS, metals, water quality indexes (COD, TOC, TN, NH3–N) and organic matters are achieved, demonstrating a high efficiency of the omniphobic membrane for the reclamation of RO concentrates.

In-situ synthesis of Drug-Containing bactericidal rough silica nanoparticles for antibacterial coating

Biomimetic rough silica nanoparticles (RNPs) have emerged as a promising drug delivery platform for antimicrobial applications, featuring unique adhesive property towards pathogens and enabling efficient bacterial killing. However, bare silica has an inert nature, thus requiring post-loading of antimicrobial agents. The in-situ synthesis of bioactive RNPs containing antibacterial agents is highly desired but remains challenging. Herein, we report the designed synthesis of bactericidal RNPs templated by an antibacterial drug of benzalkonium chloride (BAC). Compared to the counterpart with a smooth surface, RNPs-BAC exhibit enhanced antibacterial performance. Moreover, the RNPs-BAC nanocomposites allow ease of functionalization of substrates and fabric masks, providing an antibacterial coating strategy with durable pathogen-killing performance that cannot be achieved by the antibacterial drug itself. This proof-of-concept study demonstrates the potential of the innovative RNPs-based nanocomposites in antibacterial applications such as medical and wearable devices.

Using good vibrations: Melting and controlled shear jamming of dense granular suspensions

Flows of suspensions can be blocked when the suspended particles are densely packed. This makes their formulation and their transport challenging in the industry. In this paper, we study the impact of vibrations on the behavior of dense granular suspensions prepared at a volume fraction above their jamming volume fraction but below the particle assembly random close packing. Vibrations are shown to have a strong effect on their rheological properties and to tune their transition from solidlike to liquidlike behavior. We study suspensions of rough silica particles in a Newtonian fluid. In the absence of vibrations, they have a solidlike behavior: they flow only above a yield stress. Particles are confined by the liquid interface, and the yield stress is of the frictional origin. When vibrations are applied, the yield stress vanishes to give rise to a liquidlike pseudo-Newtonian behavior at a low shear rate. Using shear-reversal experiments, we show that these liquidlike vibrated suspensions of frictional particles behave like nonvibrated suspensions of frictionless particles. As the shear rate is increased, we observe a shear thickening of the vibrated suspensions, eventually leading to shear-jamming. The yield stress behavior is recovered, and vibrations have no more impact. We show that this shear thickening can be tuned by changing the vibration energy injected into the system. We, finally, propose a physical picture based on the competition between contact opening by vibration and contact formation by shear to account for these behaviors. In the framework of the Wyart and Cates [Phys. Rev. Lett. 112, 098302 (2014)] model, vibrations can be seen as introducing a thermal-like repulsive force, yielding a critical stress proportional to the vibration stress introduced by Hanotin et al. [J. Rheol. 59, 253–273 (2015)].

Molecular insight into oil displacement by CO2 flooding on rough silica surface

Rough characteristics of solid surfaces play an important role in fluid-solid interactions. In the present work, molecular dynamics (MD) simulation was used to study the oil displacement by CO2 flooding on the rectangular rough silica surface. Particular attention was given to the influence of rock roughness on oil recovery. The results showed that CO2 molecules could closely adsorb on the silica surface and drive the oil into the flooding. In the rough silica slit, the wider and deeper grooves would trap more oil molecules, and they needed a longer time to escape from the grooves. It was also pointed that the oil recovery-time relationship could be quantified using the compressed exponential function. The displacement front transformed from a concave-type meniscus to a convex-type meniscus when the groove became deeper and narrower. The study could help understand the fluid-solid interactions at the molecular level and be beneficial to more sustainable exploitation of oil.

Synergistic effect of nano-silica and eco-friendly hydrogel for the cost-effective and highly efficient oil-water separation

Reported herein is a novel eco-friendly and low-cost oil-water separation mesh that can achieve a high separation efficiency up to 99%, while the prepared mesh maintained excellent performance even after immersion in salty water for 5 days, or cycle use for 20 times. The superhydrophilic and underwater superoleophobic mesh was modified with a layer of rough nano silica by soot template method firstly, and then the mesh was covered with the calcium alginate hydrogel coating via a simple dip-coating method. The synergistic effect of the low-cost nano-silica and environmentally friendly calcium alginate hydrogel not only endowed the mesh with outstanding oil-water separation performance but also overcame the shortcoming of high-cost and pollutive in the fabrication of oil-water separation materials. The prepared mesh maintained excellent oil-water separation efficiency and water permeation flux, even after treatment in various harsh environments. The cost-effective and eco-friendly oil-water separation mesh holds great potential in the treatment of industrial and domestic waste oil.

Comparative study on wetting of smooth and rough silica surface by molten Sn–3.5Ag–2Ti alloys

Whether the rough surface is beneficial or harmful in promoting wettability for a reactive wetting system at high temperatures remains an open question. The comparative study on the wetting of smooth and rough silica by Sn-3.5Ag–2Ti solders were carried out at 650–800 °C. Although the precipitation of wettable reaction products promotes wettability, the decrease in interfacial roughness by the precipitates makes the improvement in wettability does not reach the degree of inert system. Therefore, the rough surface is harmful in promoting wettability for a reactive wetting system. The wetting behavior can be divided into two types by temperatures: the linear spreading (650–700 °C) and the non-linear spreading (750–800 °C) which correspond to the reaction rate control mechanism and the diffusion control of Ti transport mechanism, respectively. The spreading is enhanced by using the rough substrate due to the strengthening interfacial reactivity.

Fiber template approach toward preparing one-dimensional silica nanostructure with rough surface

Silica nanofibers were grown on the surface of chitosan nanofibers used as templates by coating the surface with silica derived from the hydrolysis and condensation of tetraethoxysilane using ammonium hydroxide as a catalyst. This was followed by the decomposition of the chitosan template. The relationship between different processing factors (type of templates as well as amounts of catalyst and template) and the formation of silica nanofibers was examined. Varying the processing factors was found to be effective in controlling the morphology of the silica nanofibers. The use of chitosan nanofibers effectively led to the formation of one-dimensional silica nanofibers as the positively charged chitosan nanofibers promoted the deposition of the negatively charged silica nanoparticles through electrostatic attractive forces. Therefore, the chitosan nanofibers acted as good deposition sites for interacting with silica nanoparticles. Although a large amount of catalyst promoted the sol-gel reaction, the silica nanoparticles grew excessively in the solvent. Therefore, the surface structure of the prepared silica nanofibers could be controlled by varying the amount of chitosan template as this also varied the formation mechanism of the silica nanofibers. The resultant samples had a rough silica wall composed of densely assembled silica nanoparticles, with a high specific surface area (338 m2/g).

On the shear thinning of non-Brownian suspensions: Friction or adhesion?

Shear thinning is fundamental to a broad range of particle suspensions, both in nature and in industrial applications. Yet the mechanisms governing it remain unclear. In particular, the distinct, and often competing, roles of the interparticle, particle-fluid interactions and the particle surface morphology need clarity. By using non-Brownian silica particles with different morphologies, surface functional groups and suspending media, here we reveal two different shear thinning mechanisms, controlled either by frictional or adhesion forces between particles. Smooth glass sphere suspensions in a polar medium (glycerol), where particles interact strongly with the solvent, showed no shear thinning even at high volume fractions (φ ≥ 0.5), while rough silica particles, with similar size distribution, induced shear thinning behaviour at φ values of 0.25 and above. The latter is attributed to the increased frictional contacts in the rough and irregular particles. Considering surface irregularity as elastically deformable asperities enabled us to estimate the critical load above which two neighbouring rough particles experience frictional contacts giving rise to shear thinning. In contrast, in a non-polar solvent (mineral oil), with which the particles do not interact strongly, both glass spheres and the rough silicas showed a pronounced shear thinning response and yield stress behaviour at volume fractions as low as 2% v/v. The rheology of these suspensions is dictated by the adhesion forces between the particles that lead to the formation of large agglomerates, which breakdown under increasing shear. The evolution of the sheared suspensions microstructure was captured using an optical shearing cell, which also enabled us to quantify the particle agglomeration characteristics using an aggregation index. To demonstrate the generality of our approach, we modified the surface chemistry of the glass spheres by introducing hydrophobic groups (e.g. a fluorosilane or palmitic acid) to inhibit inter-particle interactions and improve the dispersion of the otherwise inherently hydrophilic glass spheres in mineral oil; as expected, this suppressed the shear thinning behaviour of the suspensions. The present results clearly elucidate alternative design routes to control suspension rheology, whether to promote or suppress shear thinning, offering new insights for manufacturing and applications of complex particle suspensions.

Enhancement of Adhesion Strength of Perfluoroalkylpolyethers on Rough Glassy Silica for Antismudge Coatings

The adhesion behavior of perfluoropolyether (PFPE) on rough silica surfaces is investigated by steered molecular dynamics simulations. To reproduce bond breakage during sliding of PFPE, a dynamic bond breaking method is developed and applied to the PFPE–silica interface. Calculated results reveal that nanoscale roughness is a critical parameter that affects the adhesion strength due to the PFPE film thickness of 1 nm, and the adhesion strength also depends on the molecular density of PFPE on the silica surface. The effect of roughness amplitude, spacing, and molecular weight of PFPE are individually analyzed to find a key parameter for adhesion enhancement. Adhesion strength on a flat surface is highest and decreases with increasing roughness within the considered conditions. When Ra = 17.5 A, adhesion strength is 3 times lower than the flat surface, and vacant pores at the interface are observed, which implies a reduced molecular density of PFPE from 0.31 to 0.27 molecules/nm2. Increasing the roughness s...

Demonstrating spray deposition of self-regulated nanorough layers for stable transparent superhydrophobic film coatings

To make large-scale onsite fabrication of transparent superhydrophobic films practical, the deposition technique should involve mechanisms that allow self-limitation of layer thickness within nanoscale level. Here, we propose a rapid and scalable deposition strategy that allows uniform placement of a nanorough layer, sufficient to generate superhydrophobic properties with enhanced optical clarity. The coating processes involved ionic spray-assisted layer-by-layer assembly to deposit a single layer of dual-scale rough silica particles with much improved kinetics, followed by rapid surface passivation using hot steam deposition of alkylsilane mixture in open air conditions. The whole processing can be finished within a few minutes with self-termination of film growth, producing well-controlled thicknesses within the range 200–400 nm. The fabricated films exhibited excellent superhydrophobic properties with water contact angle as high as 173 ± 2° and droplet roll-off angle as small as 2 ± 1°. Instead of being a hindrance, the nanorough layers increased the optical transmission in all cases, due to negligible scattering loss and the emergence of antireflection property. The fabrication of transparent superhydrophobic film was accomplished over broad ranges of coating conditions, indicating high tolerances in the input parameters. Additionally, the resulting films also showed acceptable stability in tests of droplet compression, water jet erosion, and degradation induced by ultraviolet irradiation, which is promising for outdoor implementations.

Design of Hierarchical Beads for Efficient Label-Free Cell Capture.

Defined hierarchical materials promise cell analysis and call for application-driven design in practical use. The further issue is to develop advanced materials and devices for efficient label-free cell capture with minimum instrumentation. Herein, the design of hierarchical beads is reported for efficient label-free cell capture. Silica nanoparticles (size of ≈15 nm) are coated onto silica spheres (size of ≈200 nm) to achieve nanoscale surface roughness, and then the rough silica spheres are combined with microbeads (≈150-1000 µm in diameter) to assemble hierarchical structures. These hierarchical beads are built via electrostatic interaction, covalent bonding, and nanoparticle adherence. Further, after functionalization by hyaluronic acid (HA), the hierarchical beads display desirable surface hydrophilicity, biocompatibility, and chemical/structural stability. Due to the controlled surface topology and chemistry, HA-functionalized hierarchical beads afford high cell capture efficiency up to 98.7% in a facile label-free manner. This work guides the development of label-free cell capture techniques and contributes to the construction of smart interfaces in bio-systems.

Facile synthesis of flower-like Ag nanocube@mesoporous SiO2 and their sensitive SERS performance

Developing facile strategy to synthesize novel nanostructure substrate with superior surface enhanced Raman scattering (SERS) efficiency and identifying the optimal geometry parameter for high enhancement factor (EF) and perfect absorption status of molecules are significant aspects for the intended application of SERS. In the present work, flower-like Ag nanocube@mesoporous SiO2 (AgNC@MSiO2) nanostructure with highly rough surface was designed and prepared by restricting the nucleation region of silica on the surface of Ag nanocube modified with two different kinds of molecules (4MPAA and PAA). The novel hybrid nanostructure exhibited outstanding optical performance. Attributing to the efficient anchor of 2-naphthalenethiol (2NT) on rough silica surface and migration of the molecules through the numerous pores, a large EF of about 5.85 × 106 was achieved. It was found that the limit of detection for 2NT by the as-prepared AgNC@MSiO2 could be as low as 10−8 M with a linear dynamic region from 10−6 to 10−4 M. These results show that the AgNC@MSiO2 nanostructure presented here could be a promising candidate for classical SERS sensors.