Hydrophobic Fumed Silica Research Articles

Superhydrophobic and superoleophilic nickel foam for oil/water separation

Superhydrophobic and superoleophilic Ni foam was fabricated by immersion coating and drying method. The Ni foam was immersed in a mixture containing polytetratluoroethylene (PTFE) and hydrophobic fumed silica (R805). The mixture was dispersed in a poly(vinylidene fluoride) (PVDF) solution and the PVDF was used as a binder. The as-prepared Ni foam showed superhydrophobic and superoleophilic properties simultaneously and had a water contact angle (WCA) of 155° for water and an oil contact angle (OCA) of 0° for oil. The PTFE-coated Ni foam maintained high separation efficiency after repeated separations (40 times) above 96% for the more viscous olive oil/water mixture and above 99% for the hexane/water mixture. The as-prepared nickel foam proved to be an excellent candidate for the separation of oil and water mixtures.

Superhydrophobic Electrically Conductive Paper for Ultrasensitive Strain Sensor with Excellent Anticorrosion and Self-Cleaning Property.

Recently, a paper-based (PB) strain sensor has turned out to be an ideal substitute for the polymer-based one because of the merits of renewability, biodegradability, and low cost. However, the hygroexpansion and degradation of the paper after absorbing water are the great challenges for the practical applications of the PB strain sensor. Herein, the superhydrophobic electrically conductive paper was fabricated by simply dip-coating the printing paper into the carbon black (CB)/carbon nanotube (CNT)/methyl cellulose suspension and hydrophobic fumed silica (Hf-SiO2) suspension successively to settle the problem. Because of the existence of ultrasensitive microcrack structures in the electrically conductive CB/CNT layer, the sensor was capable of detecting an ultralow strain as low as 0.1%. During the tension strain range of 0-0.7%, the sensor exhibited a gauge factor of 7.5, almost 3 times higher than that of the conventional metallic-based sensors. In addition, the sensor displayed frequency-independent and excellent durability and reproductivity over 1000 tension cycles. Meanwhile, the superhydrophobic Hf-SiO2 layer with a micro-nano structure and low surface energy endowed the sensor with outstanding waterproof and self-cleaning properties, as well as great sustainability toward cyclic strain and harsh corrosive environment. Finally, the PB strain sensor could effectively monitor human bodily motions such as finger/elbow joint/throat movement and pulse in real time, especially for the wet or rainy conditions. All these pave way for the fabrication of a high-performance PB strain sensor.

Scalable Solid-State Synthesis of Self-Assembled Si Nanoparticles in Spherical Carbons through Relative Miscibility for Li-Ion Batteries

Nanosized Si-based materials have been extensively investigated because of their high gravimetric capacity and stable cycle performance. However, the tap density of nanosized materials is poor, leading to poor volumetric capacity. In this regard, micrometer-sized Si nanoparticles and carbon composites have been introduced to improve the volumetric energy density of Li-ion cells. However, most synthesis methods for these Si/C composites are complex, and thus, only a few methods among them are scalable for mass production. Herein, a scalable solid-state synthesis through self-assembly due to the relative miscibility of hydrophobic and hydrophilic precursors is introduced to obtain micrometer-sized porous carbon spheres containing nanosized Si particles. The self-assembly synthesis uses hydrophilic Si/SiO2 core-shell nanoparticles, hydrophilic phenolic resins, and hydrophobic fumed silica. Because phenolic resin melts and Si/SiO2 core-shells are miscible, the Si/SiO2 core-shells are embedded in the phenolic resins. Immiscible phenolic resin melts and fumed silica lead to the formation of spherical resins. Eventually, the self-assembled micrometer-sized Si/C composite spheres are obtained after heating and HF etching. The tap density of the self-assembled Si/C spheres is much higher than that of the bare Si nanoparticles. In addition, the self-assembled Si/C composite shows excellent cycle performance because of voids in the composite.

Mechanical, dielectric, and thermal properties of polydimethylsiloxane/polysilsesquioxane nanocomposite for sealant application

ABSTRACTPolysilsesquioxanes (PS) powder was synthesized from methyltrimethoxysilane and vinyltrimethoxysilane by hydrolytic condensation method in aqueous phase. The prepared PS powder was characterized using Fourier transform infrared spectroscopy, particle size, and polydispersity of the powders was determined using dynamic light scattering technique. Polydimethylsiloxane (PDMS) nanocomposites and the sealant were synthesized using different weight percentage (1–4 wt %) of PS powder and hydrophobic fumed silica. Tensile strength and thermal stability of the nanocomposites showed perceptible enhancement on increasing the filler ratio when compared to pristine PDMS composites. The surface morphology and the extent of filler dispersion were visualized from the scanning electron microscopy images. Dielectric strength of the composites also showed significant improvement on increasing the filler loading. Poly(methyl/vinyl)silsesquioxane (PMVS) (4 wt %) reinforced composites showed a considerable enrichment in properties when compared to other formulations. Adhesive strength of silicone sealant on both the alumina and mild steel substrate was studied by conducting lap shear test. PMVS‐loaded nanocomposites exhibited more adhesive strength on both the substrates and hence it can be used as a sealant in electronic assemblies. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47228.

Preparation of partially neutralized poly(acrylic acid) microspheres via inverse pickering suspension polymerization

Partially neutralized poly(acrylic acid) (PAA) microspheres have been prepared by Inverse Pickering Suspension Polymerization (IPSP) using 1,2‐dichlorobenzene (DCB) and hydrophobic fumed silica nanoparticles (HFSi‐NPs) as organic dispersing media and dispersing agent respectively. As crosslinker N,N'‐methylene bisacrylamide (MBAc), as initiator potassium persulfate (KPS) and sodium metabisulfite (SMBS) redox couple were used. Neutralization degrees were adjusted using 8N NaOH solution and polymerizations were initiated at 34°C. Water/oil phase ratio was set to 1/7 for all polymerizations. Morphology of prepared dry poly(acrylic acid) beads was examined by two microscopic methods, scanning electron microscopy (SEM) and optical microscopy. Prepared microsized polymer beads were observed as smooth and spherical in shape. Effect of neutralization degree (α) varied from 70% to 90% on absorptions in both distilled water and saline solutions, absorption under load (AUL) and crosslink density (CD) results were also investigated. POLYM. ENG. SCI., 59:162–169, 2019. © 2018 Society of Plastics Engineers

Flexural strength and modulus of autopolimerized poly (methyl methacrylate) with nanosilica

Background/Aim. Autopolymerized, or cold polymerized poly(methyl methacrylate) class of materials have a lower mechanical properties compared to hot polymerized poly(methyl methacrylate), due to a limited time of mixing before the polymerization process begins. The aim of this study was to test the effect of different relatively low nanosilica contents, in improving mechanical properties of the cold polymerized poly(methyl methacrylate). Methods. A commercially available autopolymerized poly(methyl methacrylate) denture reline resin methyl methacrylate liquid component was mixed with 7 nm after treated hydrophobic fumed silica and subsequently mixed with poly(methyl methacrylate) powder. Three nanosilica loadings were used: 0.05%, 0.2% and 1.5%. Flexural modulus and strength were tested, with one way ANOVA followed by Tukey?s test. Furthermore, zeta potential, differential scanning calorimetry, scaning electrone microscopy and energy dispersive X-ray analyses were performed. Results. Flexural modulus and strength of poly(methyl methacrylate) based nanocomposites were statistically significantly increased by the addition of 0.05% nano-SiO2. The increase in nanosilica content up to 1.5% does not contribute to mechanical properties tested, but quite contrary. The main reason was agglomeration, that occurred before mixing of the liquid and powder component and was proved by zeta potential measurement, and after mixing, proved by scanning electrone microscopy and energy dispersive x-ray analyses. Conclusions. Addition of 7 nm 0.05% SiO2 is the most effective in increasing flexural modulus and strength of autopolimerized poly(methyl methacrylate).

Robust, self-healing, superhydrophobic coatings highlighted by a novel branched thiol-ene fluorinated siloxane nanocomposites

In this work, we present one-step dip-coating strategy for fabricating robust, self-healing and superhydrophobic coatings using a coating solution that contains a novel branched thiol-ene fluorinated siloxane (T-FAS), polydimethylsiloxane (PDMS) elastomer and hydrophobic fumed silica nanoparticles (SiO2 NPs). The novel branched T-FAS, with low fluorinated surface energy and high sol-gel reactivity, was prepared by introducing (N-methyl-perfluorohexane-1-sulfonamide) ethyl acrylate (FSA) and γ-methacryloxypropyltrimethoxysilane (MPS) into pentaerythritol tetra (3-mercaptopropionate) (PETMP) via thiol-ene click reaction. The superhydrophobic coating, being high stable to strong acid, UV, thermal and smudge treatment, has a water contact angle of 165 ± 2° and shedding angle of 4 ± 1°. It can withstand at least 100 cycles of abrasion with 1500 grit sandpaper under 45 KPa due to the interpenetrating polymer networks (IPN) constructed by T-FAS/PDMS. The IPN is also self-healing to chemically etching using long perfluoro-terminated chains of T-FAS which can spontaneously reorient to new air interfaces. The robust self-healing IPN may lead to the development of new efficient strategies for durable protective coatings in various applications.

Direct Evidence for Percolation of Immobilized Polymer Layer around Nanoparticles Accounting for Sol-Gel Transition in Fumed Silica Dispersions.

Immobilized polymer fractions have been claimed to be of vital importance for sol-gel transitions generally observed in nanoparticle dispersions but remain a matter of debate regarding mechanism and difficulty for prediction. Here we investigate the immobilized layer structures of trifunctionality polyether polyol (PPG) near the surfaces of hydrophilic and hydrophobic fumed silica (FS) nanoparticles to reveal the role of surface chemistry on the molecular dynamics and sol-gel transitions of the dispersions. Using modulated differential scanning calorimetry, we measure the specific heat capacity during glass transition and the enthalpy during cold-crystallization. Comparing with hydrophobic FS that forms a fully immobilized (glassy) layer, we find that hydrophilic FS immobilizes more PPG, forming a partially immobilized outer layer being unable to crystallize next to the inner glassy layer. By correlating the thickness of the glassy layer with half of the minimum spacing between nanoparticles, we directly evidence the percolation of this layer along the nearest neighbor nanoparticles responsible for the sol-gel transition. Using effective volume fraction including the glassy layer, we successfully construct master curves of relative viscosity of both hydrophilic and hydrophobic FS dispersions, pointing to a common sol-gel transition mechanism mediated by the surface chemistry.

Inorganic-Organic Thiol-ene Coated Mesh for Oil/Water Separation.

A highly efficient mesh for oil/water separation was fabricated by using a superhydrophobic and superoleophilic coating of thiol-ene hybrid, consisting of pentaerythritol tetra(3-mercaptopropionate) (PETMP), 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (TMTVSi), and hydrophobic fumed silica nanoparticles, via a simple two-step fabrication process. Spray deposition and UV curing photopolymerization were sequentially performed, during which solvent evaporation provides microscale roughness while nanoparticle aggregation forms nanoscale roughness. The hierarchical morphologies were stabilized after UV curing photopolymerization. High contact angle (>150°) and low roll-off angle (<5°) were achieved due to the multiscale roughness structure of the hierarchical morphologies. These coatings also have excellent chemical resistance, as well as temperature and pH stability, after curing.

Superhydrophobic and oleophobic surfaces obtained by graft copolymerization of perfluoroalkyl ethyl acrylate onto SBR rubber

Abstract Superhydrophobic and oleophobic rubbery coatings were prepared by spraying perfluoroalkyl ethyl acrylate (Zonyl TA-N) grafted styrene butadiene rubber (SBR) solution in toluene after addition of hydrophilic and hydrophobic fumed silica powders onto glass. Grafting onto SBR has been performed by free radical copolymerization in toluene using different Zonyl TA-N feed compositions. Molecular weights of the graft copolymers were determined by GPC and intrinsic viscosity measurements. Thin films of Zonyl TA-N grafted SBR copolymers were prepared by dip coating glass slides into toluene solutions of SBR- g -Zonyl TA-N with varying fluoromonomer contents and their surface free energies were determined by contact angle measurements. The increase in Zonyl TA-N content resulted in a considerable decrease of the total surface free energy of the grafted SBR film. Later, superhydrophobic and oleophobic surfaces were prepared by adding hydrophilic and hydrophobic fumed silica powders into graft copolymer solutions and spraying onto glass. The effect of the Zonyl TA-N content in the graft copolymer, type of silica and its weight concentration in the solution on the water and hexadecane contact angle values, on the surface morphology and mechanical durability of the coatings were investigated. The highest water contact angle of the SBR- g -Zonyl TA-N/SiO 2 hybrid coatings was determined to be 162° and hexadecane contact angle 147° after adjusting the silica type, solids content and fluoroacrylate/SBR composition of the graft copolymer spray solution.

Influence of the coating method on the formation of superhydrophobic silicone–urea surfaces modified with fumed silica nanoparticles

Abstract Effect of the coating method on the formation of superhydrophobic polydimethylsiloxane–urea copolymer (TPSC) surfaces, modified by the incorporation of hydrophobic fumed silica nanoparticles was investigated. Four different coating methods employed were: (i) layer-by-layer spin-coating of hydrophobic fumed silica dispersed in an organic solvent onto TPSC films, (ii) spin-coating of silica–polymer mixture onto a glass substrate, (iii) spray coating of silica/polymer mixture by an air-brush onto a glass substrate, and (iv) direct coating of silica–polymer mixture by a doctor blade onto a glass substrate. Influence of the coating method, composition of the polymer/silica mixture and the number of silica layers applied on the topography and wetting behavior of the surfaces were determined. Surfaces obtained were characterized by scanning electron microscopy (SEM), white light interferometry (WLI) and advancing and receding water contact angle measurements. It was demonstrated that superhydrophobic surfaces could be obtained by all methods. Surfaces obtained displayed hierarchical micro-nano structures and superhydrophobic behavior with static and advancing water contact angles well above 150° and fairly low contact angle hysteresis values.

Influence of the average surface roughness on the formation of superhydrophobic polymer surfaces through spin-coating with hydrophobic fumed silica

Formation of superhydrophobic polymer surfaces were investigated through successive spin-coating of hydrophobic fumed silica dispersed in an organic solvent onto polymer films. Two different polymers, a hydrophobic segmented silicone-urea copolymer (TPSC) and hydrophilic poly(methyl methacrylate) (PMMA) were used as model substrates. Influence of the polymer type and structure, silica concentration and the number of silica layers applied on the topography, average roughness and the wetting behavior of the surfaces were determined. Polymer surfaces obtained were characterized by scanning electron microscopy, white light interferometry, atomic force microscopy and advancing and receding water contact angle measurements. It was possible to obtain superhydrophobic surfaces displaying hierarchical micro/nano features both for TPSC and PMMA. A close correlation was observed between the number of silica layers applied and average surface roughness obtained. It was demonstrated that an average surface roughness value of 125–150 nm was necessary for the formation of superhydrophobic surfaces, both for TPSC and PMMA. Chemical structure and nature of the polymeric substrate seem to play a significant role on the topography and average roughness of the silica coated surfaces formed. Superhydrophobic surfaces displayed static and advancing water contact angles well above 150° and fairly small contact angle hysteresis.

Superhydrophobic nanocomposites from biodegradable thermoplastic starch composites (Mater-Bi®), hydrophobic nano-silica and lycopodium spores

Due to increasing environmental concerns related to bio-persistence of petroleum based polymers, research efforts have intensified towards developing biodegradable materials with equivalent performance properties. Among these properties liquid repellence is one of the most challenging to obtain due to the fact that most biopolymers such as polysaccharides or bio-polyesters are hygroscopic or hydrophilic. One possible approach is to formulate biopolymer nanocomposites with water repellent properties. Here, we demonstrate such an approach using a commercial thermoplastic starch composite, Materi-Bi®, hydrophobic fumed silica nanoparticles and lycopodium spores. We found that both hydrophobic fumed silica and Materi-Bi® have excellent colloidal stability and solubility in chloroform and they can be spray coated onto various surfaces like paper, metals and semiconductors. By varying the concentration ratio of biopolymer to hydrophobic fumed silica, the wetting properties of the nanocomposites could be tuned. Superhydrophobic nanocomposites displayed raspberry-like surface roughness with water contact angles exceeding 160° with very low water droplet roll-off angles (∼1°). On the other hand, composites of Materi-Bi® and lycopodium spores displayed sticky superhydrophobicity (rose petal effect). Superhydrophobic nanocomposites were found to withstand thermal aging at 250 °C without loss of properties. Due to the resultant micro-morphology of the nanocomposites, certain coatings were rendered superoleophobic by functionalizing with a dilute fluoroacrylic polymer solution in acetone. Oil droplet contact angles reached 166° with droplet roll-off angles of approximately 15°.

Wood surfaces protected with transparent multilayer UV-cured coatings reinforced with nanosilica and nanoclay. Part I: morphological study and effect of relative humidity on adhesion strength

Multilayer coatings that are used to protect surfaces of wood components constituting ready to assemble furniture must have good adhesion to the substrate, particularly for wood furniture used in high humidity environments like bathrooms. It is not known whether adding nanoparticles to such coatings will change their properties. Surfaces of yellow birch wood (Betula alleghaniensis Britton) were protected with six different types of multilayer coatings (MCs). Prepared primer and topcoat UV-curable formulations constituting these MCs contained, respectively, hydrophobic-fumed silica (NS) and nanoclays (NC). They were added at 0 and 0.5 wt% for NS and at 0, 1, and 3 wt% for NC. The viscosity behavior of these formulations was evaluated as a function of shear rate. The morphology of the cross-section of coated wood samples was qualitatively studied by means of both scanning and transmission electron microscopy (SEM and TEM analysis). The adhesion strength of these MCs on wood surfaces was assessed as a function of relative humidity (RH). TEM images have revealed that topcoats reinforced with NC appear to have an intercalated (micro and nanoparticles) morphology. Statistical results have shown that NS and NS × NC do not significantly confer additional adhesion strength of MCs on wood surfaces, whereas the effect of NC is significant. The adhesion strength of coated wood samples conditioned at 80% RH was higher than that obtained on those conditioned at 40% RH. Multilayer coating # 5 ([0.5 wt% NS—1 wt% NC] combination) has been chosen as the ideal protection system for two reasons: (i) high adhesion strength at low RH and (ii) good barrier properties.

Suppression of Aluminum Corrosion in Lithium Bis(trifluoromethanesulfonyl)imide-based Electrolytes by the Addition of Fumed Silica

The corrosion property of aluminum by lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt is investigated in liquid and gel electrolytes consisting of ethylene carbonate/propylene carbonate/ethylmethyl carbonate/diethyl carbonate (20:5:55:20, vol %) with vinylene carbonate (2 wt %) and fluoroethylene carbonate (5 wt %) using conductivity measurement, cyclic voltammetry, scanning electron microscopy, and energy dispersive X-ray spectroscopy. All corrosion behaviors are attenuated remarkably by using three gel electrolytes containing 3 wt % of hydrophilic and hydrophobic fumed silica. The addition of silica particles contributes to the increase in the ionic conductivity of the electrolyte, indicating temporarily formed physical crosslinking among the silica particles to produce a gel state. Cyclic voltammetry also gives lower anodic current responses at higher potentials for repeating cycles, confirming further corrosion attenuation or electrochemical stability. In addition, the degree of corrosion attenuation can be affected mainly by the electrolytic constituents, not by the hydrophilicity or hydrophobicity of silica particles.

Superhydrophobic Hybrid Inorganic–Organic Thiol-ene Surfaces Fabricated via Spray-Deposition and Photopolymerization

We report a simple and versatile method for the fabrication of superhydrophobic inorganic-organic thiol-ene coatings via sequential spray-deposition and photopolymerization under ambient conditions. The coatings are obtained by spray-deposition of UV-curable hybrid inorganic-organic thiol-ene resins consisting of pentaerythritol tetra(3-mercaptopropionate) (PETMP), triallyl isocyanurate (TTT), 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (TMTVSi), and hydrophobic fumed silica nanoparticles. The spray-deposition process and nanoparticle agglomeration/dispersion provide surfaces with hierarchical morphologies exhibiting both micro- and nanoscale roughness. The wetting behavior, dependent on the concentration of TMTVSi and hydrophobic silica nanoparticles, can be varied over a broad range to ultimately provide coatings with high static water contact angles (>150°), low contact angle hysteresis, and low roll off angles (<5°). The cross-linked thiol-ene coatings are solvent resistant, stable at low and high pH, and maintain superhydrophobic wetting behavior after extended exposure to elevated temperatures. We demonstrate the versatility of the spray-deposition and UV-cure process on a variety of substrate surfaces including glass, paper, stone, and cotton fabric.

Fractionated crystallization and morphology of PP/PS blends in the presence of silica nanoparticles with different surface chemistries

The fractionated crystallization behavior of polypropylene (PP) droplets in its 20/80 blends with polystyrene (PS) in the presence of hydrophilic or hydrophobic fumed silica nanoparticles was studied by using differential scanning calorimetry, scanning electron microscopy, and transmission electron microscopy. It was found that the fractionated crystallization of PP droplets in the PS matrix was promoted by adding a low content of hydrophobic or hydrophilic nanoparticles due to their morphological refinement effect. However, discrepancies in the fractionated crystallization behavior of PP droplets occurred as the nanoparticle content increased. The crystallization became dominated by the heterogeneous nucleation effect of high content of hydrophilic nanoparticles, which possibly migrated into PP droplets during mixing and significantly suppressed their fractionated crystallization. In contrast, the morphological refinement effect still played a dominated role in promoting the fractionated crystallization of PP droplets in PP/PS blends filled with higher content hydrophobic nanoparticles as a result of the efficiently morphological refinement effect.

Superhydrophobic–superhydrophilic binary micropatterns by localized thermal treatment of polyhedral oligomeric silsesquioxane (POSS)–silica films

Surfaces patterned with alternating (binary) superhydrophobic-superhydrophilic regions can be found naturally, offering a bio-inspired template for efficient fluid collection and management technologies. We describe a simple wet-processing, thermal treatment method to produce such patterns, starting with inherently superhydrophobic polysilsesquioxane-silica composite coatings prepared by spray casting nanoparticle dispersions. Such coatings become superhydrophilic after localized thermal treatment by means of laser irradiation or open-air flame exposure. When laser processed, the films are patternable down to ∼100 μm scales. The dispersions consist of hydrophobic fumed silica (HFS) and methylsilsesquioxane resin, which are dispersed in isopropanol and deposited onto various substrates (glass, quartz, aluminum, copper, and stainless steel). The coatings are characterized by advancing, receding, and sessile contact angle measurements before and after thermal treatment to delineate the effects of HFS filler concentration and thermal treatment on coating wettability. SEM, XPS and TGA measurements reveal the effects of thermal treatment on surface chemistry and texture. The thermally induced wettability shift from superhydrophobic to superhydrophilic is interpreted with the Cassie-Baxter wetting theory. Several micropatterned wettability surfaces demonstrate potential in pool boiling heat transfer enhancement, capillarity-driven liquid transport in open surface-tension-confined channels (e.g., lab-on-a-chip), and select surface coating applications relying on wettability gradients. Advantages of the present approach include the inherent stability and inertness of the organosilane-based coatings, which can be applied on many types of surfaces (glass, metals, etc.) with ease. The present method is also scalable to large areas, thus being attractive for industrial coating applications.

Gamma-ray sterilization effects in silica nanoparticles/γ-APTES nanocomposite-based pH-sensitive polysilicon wire sensors.

In this paper, we report the γ-ray sterilization effects in pH-sensitive polysilicon wire (PSW) sensors using a mixture of 3-aminopropyltriethoxysilane (γ-APTES) and polydimethylsiloxane (PDMS)-treated hydrophobic fumed silica nanoparticles (NPs) as a sensing membrane. pH analyses showed that the γ-ray irradiation-induced sensitivity degradation of the PSW pH sensor covered with γ-APTES/silica NPs nanocomposite (γ-APTES+NPs) could be restored to a condition even better than prior to γ-ray irradiation by 40-min of post-sterilization room-temperature UV annealing. We found that the trapping charges caused by γ-ray sterilization primarily concentrated in the native oxide layer for the pH sensor covered with γ-APTES, but accumulated in the γ-APTES+NPs layer for the γ-APTES+NPs-covered sensor. It is believed that mixing the PDMS-treated silica NPs into γ-APTES provides many γ-APTES/SiO2 interfaces for the accumulation of trapping charges and for post-sterilization UV oxidation, thus restoring γ-ray-induced sensor degradation. The PDMS-treated silica NPs not only enhance the sensitivity of the pH-sensitive PSW sensors but are also able to withstand the two-step sterilization resulting from γ-ray and UV irradiations. This investigation suggests γ-ray irradiation could be used as a highly-efficient sterilization method for γ-APTES-based pH-sensitive biosensors.

Characteristics of Polysilicon Wire Glucose Sensors with a Surface Modified by Silica Nanoparticles/γ-APTES Nanocomposite

This report investigates the sensing characteristics of polysilicon wire (PSW) glucose biosensors, including thickness characteristics and line-width effects on detection limits, linear range and interference immunity with membranes coated by micropipette/spin-coating and focus-ion-beam (FIB) processed capillary atomic-force-microscopy (C-AFM) tip scan/coating methods. The PSW surface was modified with a mixture of 3-aminopropyl-triethoxysilane (γ-APTES) and polydimethylsiloxane (PDMS)-treated hydrophobic fumed silica nanoparticles (NPs). We found that the thickness of the γ-APTES+NPs nonocomposite could be controlled well at about 22 nm with small relative standard deviation (RSD) with repeated C-AFM tip scan/coatings. The detection limit increased and linear range decreased with the line width of the PSW through the tip-coating process. Interestingly, the interference immunity ability improves as the line width increases. For a 500 nm-wide PSW, the percentage changes of the channel current density changes (ΔJ) caused by acetaminophen (AP) can be kept below 3.5% at an ultra-high AP-to-glucose concentration ratio of 600:1. Simulation results showed that the line width dependence of interference immunity was strongly correlated with the channel electrical field of the PSW biosensor.