Properties Of Silica Nanoparticles Research Articles

Single step polyol synthesis of highly stable Pt/C/SiO2 catalysts for use in PEMFCs: effects of pH, temperature and W/EG ratio

Hybrid supports have been proposed as a new alternative to increase the stability of ORR catalysts used in PEMFCs for automotive applications since they are known to be stable under harsh conditions. In this work, Pt nanoparticles were deposited over C/SiO2, via single-step polyol method, to take advantage of the corrosion-resistance properties of silica nanoparticles. In fact, the synthesis parameters, namely, pH, temperature, and glycol concentration had a remarkable impact on the Pt size-distribution, crystallinity, and dispersion over the C/SiO2 supports. A maximum ORR activity and stability was obtained for Pt/C/SiO2 catalysts produced at 1:6 W/EG (v/v). The addition of SiO2 nanoparticles to the carbon structure showed their ability to effectively inhibit support corrosion and Pt nanoparticles detachment and/or growth, with the pH adjustments being critical for obtaining highly stable C/SiO2 supports. Pt/C/SiO2 synthetized under acidic conditions revealed the highest stability when subjected to accelerated stress tests (ASTs), losing only 30 % of the initial electrochemically active surface area (ECSA) of Pt after 4 000 cycles from 0.6 to 1 V (vs RHE), whereas the commercial Pt/C revealed > 50 % of ECSA loss.

Study of the synergistic effects between different surfactant types and silica nanoparticles on the stability of liquid foams at elevated temperature

In recent years, there has been an increasing interest in the application of foam-based fluids in the field of hydrocarbon recovery. The combination of nanoparticles (NP) and surfactant has been intensively studied to improve the thermal stability and optimize the performance of foams. However, the synergistic interactions between NP and surfactants, and their impacts on foam stabilization at elevated temperature have yet to be clearly understood. This paper studies the effects of three types of surfactants with varied concentrations on the properties of silica nanoparticles (SNP) and on the stability of nano-stabilized foams at ambient and elevated temperatures. The experiments involved the zeta potential, particle size and contact angle measurements of SNP in surfactant solutions as well as the foamability and bulk static stability tests. The results showed that among three surfactant types, cationic surfactant had some unique impacts on SNP such as converting the surface charge, promoting particle aggregation and increasing the hydrophobicity of SNP. The aggregation behaviour and hydrophobization of SNP were found to delay liquid drainage and affect the foam stability positively. At elevated temperature, SNP in surfactant dispersions were observed to have lower magnitude of zeta potential and larger particle sizes. In comparison with ionic surfactants, non-ionic surfactant demonstrated considerably smaller effects on generating and stabilizing nano-foams. At sufficient surfactant concentration, the electrostatic attraction between cationic surfactant and SNP promoted higher foam stability than the electrostatic repulsion between anionic surfactant and SNP. This research provides a better insight into the synergistic interactions between surfactants and SNP, and their influences on the stability of foams at reservoir temperature.

Dehydration of Natural Gas Using Polyether Sulfone (PES) Membrane and Its Nanocomposite with Silica Particles and Nitrogen Sweeping Gas

Natural gas must be dehydratedbefore being sent to the distribution network to control corrosion and prevent the formation of solid hydrates. Membrane technology is a viable alternative to conventional glycol absorbents and adsorbent solids. This study was performed to evaluate the dehydration of crude natural gas by membrane separation process. Various operating conditions such as the effect of silica nanoparticles, pressure and sweeping gas on the removal of water vapor dissolved in natural gas were investigated using PES membrane and its nanocomposite. PES membranes and their nanocomposites with silica was made by solution mixing method in solvent dimethyl formamide. The properties of silica nanoparticles and fabricated nanocomposite membranes were evaluated by Fourier transfer spectroscopy and scanning electron microscopy. The dehydration rate was from natural gas in the pressure range of 2 to 10 bar and temperature of 30 °C in the presence of nitrogen sweeping gas. The addition of silica nanoparticles to the PolyetherSulfonemembrane significantly reduced the moisture content of natural gas. Also, with increasing feed pressure, the amount of water permeation from the membrane improved. The use of nitrogen sweeping gas reduced the amount of water in natural gas in pure Polyether Sulfone membranes by more than 80% and in nanocomposite membranes by more than 100%.

Morphological and biological properties of silica nanoparticles for CRTC3-siRNA delivery and downregulation of the RGS2 expression in preadipocytes.

The aim of this study was to characterize the morphological properties of amorphous silica nanoparticles (SiO2 NPs), their cytotoxicity and intracellular location within Human Osteoblasts (HOB). Additionally, SiO2 NPs were explored for their effectivity as carriers of CRTC3-siRNA on Human Preadipocytes (HPAd), and thus downregulate RGS2 gene expression. SiO2 NPs were synthesized using the method of Stöber at 45 °C, 56 °C, and 62 °C. These were characterized via TEM with EDS, Zeta Potential and FT-IR. Cytotoxicity was evaluated by XTT at three concentrations 50, 100 and 500 µg/mL; SiO2 NPs intracellular localization was observed through Confocal Laser Scanning Microscope. Delivering siRNA effectivity was measured by RT-qPCR. Morphology of SiO2 NPs was spherical with a range size from 64 to 119 nm; their surface charge was negative. Confocal images demonstrated that SiO2 NPs were located within cellular cytoplasm. At a SiO2 NPs concentration of 500 µg/mL HOB viability decreased, while at 50 µg/mL and 100 µg/mL cell viability was not affected regardless SiO2 NPs size. SiO2 NPs-CRTC3-siRNA are effective to down-regulate RGS2 gene expression in HPAd without cytotoxic effects. The developed SiO2 NPs-CRTC3-siRNA are a promising tool as a delivery vehicle to control obesity.

Polymer/inorganic hybrids containing silver nanoparticles and their activity in the disinfection of fish aquariums/ponds

ABSTRACT A grafted polymer/inorganic hybrid combining the properties of silica nanoparticles (Rav = 7.7 nm) and polyacrylamide (SiO2-g-PAAm) was synthesized, characterized and used as a matrix for in situ synthesis of silver nanoparticles (AgNPs). In the “core”-“corona” hybrid nanostructures, PAAm grafts were additionally bonded to the silica surface by H-bonds. The reduction of Ag+-ions in SiO2-g-PAAm solutions occurred in PAAm “coronas” with a high rate and yield. This led to the formation of spherical AgNPs of 3–9 nm in size in swollen hybrid nanostructures. Various aspects of the possible use of the AgNPs/SiO2-g-PAAm composition for disinfecting fish aquariums/ponds, including biological risks, were studied.

A Systematic Investigation on the Properties of Silica Nanoparticles "Multipoint"-Grafted with Poly(2-acrylamido-2-methylpropanesulfonate-co-acrylic Acid) in Extreme Salinity Brines and Brine-Oil Interfaces.

Nanoparticles (NPs) may have great potential for various subsurface applications, including oil and gas recovery, reservoir imaging, and environmental remediation. One of the important challenges for these downhole applications is to achieve colloidal stability in subsurface media at high salinity and high temperature. It has been previously shown that several functional NPs "multipoint"-grafted with anionic poly(2-acrylamido-2-methyl-1-propanesulfonate-co-acrylic acid; AMPS-co-AA) exhibited remarkable colloidal stabilities in specific environments mimicking the harsh subsurface aquatic media, such as the American Petroleum Institute (API) brine. However, many important properties of such particles, other than the colloidal stabilities, must be studied in a more systematic fashion for a wide range of salt concentrations (Cs). Herein, we investigate various properties of the silica (SiO2) NPs multipoint-grafted with poly(AMPS-co-AA), SiO2-g-poly(AMPS-co-AA), in NaCl and CaCl2 solutions across a range of salinities. The brush behavior of the grafted random copolymers was investigated in both salt solutions from salt-free conditions up to extreme salinities. The particles displayed brine-oil interfacial activity with increasing Cs, stabilizing oil-in-brine emulsions as Pickering emulsifiers. A high internal phase emulsion (HIPE) with an internal oil phase of up to 80 vol % could be formed in CaCl2 solutions at high Cs, which exhibited gel-like behaviors.

Preparation and characterization of silica nanoparticles from sugarcane bagasse ash for using as a filler in natural rubber composites

Silica nanoparticles from sugarcane bagasse ash (SBA) were prepared from sol–gel process. Particle size, specific surface area, morphology, chemical composition and chemical structure of SBA and prepared silica nanoparticles were characterized. The effect of drying techniques such as freeze drying (FD) and heat drying (HD) on the properties of silica nanoparticles was investigated. High purity of silica nanoparticles in size range of 90 ± 10 nm were successfully prepared. FD provided silica nanoparticles with high specific surface area and high porosity compared to conventional HD. The effect of silica nanoparticle contents on cure characteristics, mechanical properties, and morphology of natural rubber (NR) composites was studied. Scorch time of NR composites was increased with an increase in silica nanoparticle content due to the disturbance of vulcanization process by silica surface. FD-silica/NR composites provided longer scorch time and cure time compared to HD-silica/NR composites due to higher active surface area of FD-silica. Modulus and hardness of NR composites were increased while elongation at break was decreased with an increase in silica nanoparticle content. Tensile strength of the composites increased with silica nanoparticle content and tended to reduce at high silica nanoparticle content. FD-silica/NR composites exhibited better mechanical properties than HD-silica/NR composites due to better filler-rubber interaction.

The Tribological Properties of Water Lubricated Ceramics with Silica Nanoparticle Additives

Water lubricated ceramics exhibited excellent tribological properties such as super lubricity and good thermal stability. However, long running-in period and low load-carrying capacity limited the application of water lubricated ceramics. Silica nanoparticles have been shown to be highly effective additives for oil lubrication. And because of their economic efficiency, eco-friendliness and excellent tribological properties, silica nanoparticles are considered to be great potential additives for water-based lubricant, especially for ceramic lubrication. Here, we present an exploratory study on silica nanoparticles as water-based lubricant additives for ceramic lubrication. Different silica nanoparticles were synthesized, characterized and added into water as additives. The tribological properties of silica nanoparticles as water based lubricant additives were tested. The tribological mechanism of silica nanoparticles was analyzed. It was found that silica nanoparticles dispersed well and kept stable in water. Both the running-in period and the stable period were influenced by silica nanoparticles. With the optimal 5 wt. % amino modified silica nanoparticles added into the water lubricant, the running-in time dropped by 97.0% and the average friction coefficient by 86.6% compared with the pure water.

Rheological Properties of Silica Nanoparticles in Brine and Brine-Surfactant Systems

Rheological Properties of Silica Nanoparticles in Brine and Brine-Surfactant Systems

Synthesis and Characterization of Superhydrophobic, Self-cleaning NIR-reflective Silica Nanoparticles.

Multifunctional coatings offer many advantages towards protecting various surfaces. Here we apply aggregation induced segregation of perylene diimide (PDI) to control the surface morphology and properties of silica nanoparticles. Differentially functionalized PDI was incorporated on the surface of silica nanoparticles through Si-O-Si bonds. The absorption and emission spectra of the resultant functionalised nanoparticles showed monomeric or excimeric peaks based on the amounts of perylene molecules present on the surface of silica nanoparticles. Contact angle measurements on thin films prepared from nanoparticles showed that unfunctionalised nanoparticles were superhydrophilic with a contact angle (CA) of 0°, whereas perylene functionalised silica particles were hydrophobic (CA > 130°) and nanoparticles functionalised with PDI and trimethoxy(octadecyl)silane (TMODS) in an equimolar ratio were superhydrophobic with static CA > 150° and sliding angle (SA) < 10°. In addition, the near infrared (NIR) reflectance properties of PDI incorporated silica nanoparticles can be used to protect various heat sensitive substrates. The concept developed in this paper offers a unique combination of super hydrophobicity, interesting optical properties and NIR reflectance in nanosilica, which could be used for interesting applications such as surface coatings with self-cleaning and NIR reflection properties.

Hyaluronic acid–conjugated silica nanoparticles for breast cancer therapy

ABSTRACTNovel silica nanoparticles (SLN) chemically modified with hyaluronic acid (HA) were developed by exploiting the drug loading property of SLN and the tumor-targeting ability of HA to construct a tumor-targeting paclitaxel (PTX) delivery system (HA-SLN) for potential breast cancer therapy. The experimental results indicated that PTX loading into the HA-SLN was favorable to cancer therapy. PTX-loaded HA-SLN nanoparticles increased the accumulation of PTX in MCF-7 breast cancer cells via CD44 receptor–mediated endocytosis and exhibited superior anticancer activity in vitro. In vivo anticancer efficacy assay revealed that HA-SLN possessed preferable anticancer ability that exhibited minimal toxic side effects of PTX and strong tumor-suppression potential.

Influence of Surfactants on the Physical Properties of Silica Nanoparticles Synthesis via Sol-Gel Method

Silica nanoparticles (n-SiO2) have been synthesized using hydrolysis of Tetraethyl orthosilicate (TEOS) as starting material and ethanol as solvent by sol-gel method. The effect of different surfactants such as non-ionic surfactants sorbitan tristearate (Span 65) and sorbitan trioleate (Span 85) and anionic surfactants Sodium dodecyl sulfate (SDS) and emulsifier T-80 (Tween-80) on morphology and size of the particles was investigated. The role of these surfactants in controlling the size and properties of silica nanoparticles has been discussed. The particles size of silica nanoparticles is controlled also using Ammonia as base catalyst. Silica nanoparticles with average particles size 18 nm have been synthesized with span 65. Various analytical methods, i.e., scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV- visible absorption spectroscopy and X-ray diffraction (XRD) were used to comprehensively characterize the obtained silica nanoparticles. The synthesized Si NPs has been used for adsorption of uranium from aqueous waste solution and the best conditions were achieved at pH 4.0. The adsorption isotherms were described by means of Langmuir and Freundlich isotherm models. The maximum sorption capacity of the prepared Si NPs and experimental results showed this to be 20.6 mg.g-1.

The properties of silica nanoparticles with high monodispersity synthesized in the microreactor system

A new combined micromixer/microreactor/batch reactor system for the synthesis of monodisperse silica particles was demonstrated, which showed superiorities over the batch reactor. The silica nanoparticles with different sizes (ranging from 20 nm to 2 μm) and size distributions could be controllably synthesized by varying the reaction temperature and reaction time. The narrowest size distribution of the silica particles was synthesized at 60 °C. The transmission electron microscopy characterization showed that the sphericities of silica particles got better as the particle size increased. Thermal gravimetry–differential thermal analysis and Fourier transform infrared characterization indicated that the amount of ethoxy groups of silica particles decreased and the hydroxyl groups increased with the reaction time increasing. And the hydroxyl groups in silica particles increased with the reaction temperature rising.

Synthesis and characterization of uniform silica nanoparticles on nickel substrate by spin coating and sol–gel method

Spin coating and sol–gel methods are proposed for the preparation of silica nanoparticles on a nickel substrate using silicon tetrachloride, 2-methoxyethanol, and four different types of alkaline solutions. The effects of the type of alkaline solution, concentration of silica solution, and speed of spin coating on the properties of silica nanoparticles are investigated systematically. Uniform spherical shape of silica nanoparticles on Ni with the smallest size are obtained with sodium carbonate among the alkaline solutions after stirring at 70°C for 6h and spin-coating at 7000rpm. Physical and electrochemical properties of the silica particles are investigated.

Sol-Gel Derived Mesoporous Silica Nanoparticles under Base Catalysis for Uses as Anti-Reflective Coating Layers

In this study, mesoporous silica nanoparticles were synthesized through sol-gel method, employing tetraethylorthosilicate (TEOS) as a precursor under base-catalyzed condition. The reaction temperature was kept constant at 50→C. The results indicated that the properties of silica nanoparticles could be controlled by altering the calcination temperatures. It has been found that silica nanoparticles synthesized under base-catalyzed and calcined at 600→C are uniform, well-dispersed and spherical-shaped. The anti-reflective behavior and the methylene blue adsorption capacity are optimized when calcined at this temperature.

Synthesis of High-purity Spherical Silica Nanoparticles from Powder Quartz by Improved Sol–Gel Method

Abstract High-purity spherical silica nanoparticles have been successfully synthesized using powder quartz as silica sources in an improved sol–gel method. The effects of the modulus (molar ratio SiO2/Na2O) of sodium silicate and poly(ethylene glycol) (PEG) on the properties of silica nanoparticles were investigated. The results suggested that with the increase of modulus, the purity of silica nanoparticles increased. The higher purity (99.92 wt %) products can be obtained from the modulus of 3. Moreover, it was also found that the particle size, distribution, and dispersion significantly depend on the concentration of PEG. The silica nanoparticles with average size of 60 nm are well-dispersed and show a narrow size distribution when the PEG concentration is 2 wt %. The results suggest that it is feasible to prepare high-purity spherical silica nanoparticles using powder quartz as silica sources.

Preparation of silica nanoparticles using silicon tetrachloride for reinforcement of PU

A facile and economic method was proposed for the preparation of silica nanoparticles by the hydrolysis of silicon tetrachloride in alkaline solution. The starting material silicon tetrachloride was inexpensive and obtained from the by-product of polysilicon industry. The effects of the type of alkaline, alkaline concentration, reaction time, surfactant and post processing on the properties of silica nanoparticles were investigated. The morphology and size of silica nanoparticles were characterized by transmission electron microscopy and scanning electron microscopy. Spherical silica nanoparticles with narrow size distribution, high specific surface area, high dibutyl phthalate (DBP)-absorption and low density were obtained at the optimal conditions. Afterwards, silica nanoparticles were dispersed in polyurethane (PU) coatings via solution blending to reinforce PU. The mechanical properties of PU films were measured using universal testing machine and sclerometer. The results showed that the mechanical properties of PU films were obviously improved with the addition of the silica nanoparticles.

Synthesis and photophysical properties of silica nanoparticles based on europium(iii) complexes

Monodisperse 280–480 nm silica particles doped with europium complexes with thenoyltrifluoroacetylacetone and adducts with some phosphine oxides as luminophores were prepared for the first time by the optimized Stober procedure using surfactants. The size and the polydispersity of the obtained particles depend on the luminophore incorporated in the polymer template. The photophysical properties of aqueous dispersions of the europium(iii)-doped silica particles were studied by the luminescence method.

Thermoplastic polyurethane/silica nanocomposite fibers by electrospinning

AbstractThermoplastic polyurethane/silica nanocomposite fibers with good mechanical properties were prepared by electrospinning, using colloidal silica as the source of silica and dimethyl formamide as the solvent. The fiber morphology was examined by field emission scanning electron microscopy. The average fiber diameter is about 0.8 μm with 0–10 wt % silica, and silica nanoparticles were observed on all fiber surfaces. X‐ray photoelectron spectroscopy analysis of Si in combination with transmission electron microscopy observation suggest that silica nanoparticles have a fairly uniform distribution in the fibers rather than enriching on the fiber surfaces. Tensile tests show that the incorporation of silica nanoparticles can bring about a significant reinforcing effect without decreasing the ductility. The reinforcing effect is further confirmed by dynamic mechanical analysis. The thermoplastic polyurethane/silica composite fiber mats can adsorb gold nanoparticles after further treatment with 3‐aminopropyltriethoxysilane, demonstrating that the composite fibers could be used as functional fibers by using the properties of silica nanoparticles. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011

Preparation and properties of silica nanoparticles from oil shale ash

The method of preparing spherical silica nanoparticles from the oil shale ash (OSA) via the ultrasonic technique in the hydrolysis-condensation stage followed by azeotropic distillation, was reported. The effects of ultrasonic and azeotropic distillation on the particle size and distribution have been investigated. Further, the morphology and properties of the silica particles were examined. The X-ray fluorescence spectroscopy (XRF) and Brunauer Emmett Teller (BET) analysis confirmed that the powders consist of silica nanoparticles with high purity, 99.90% and specific surface area of 697 m 2/g. X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) analysis indicate that the silica nanoparticles are amorphous and that the surface of silica nanoparticles is modified by the organics. The transmission electron microscopy (TEM) images of the sample show that good dispersion and uniform silica particles with an average diameter of about 10 nm are prepared. The results obtained in the mentioned method prove that the oil shale ash (OSA) can be used for production of silica nanoparticles.