Dispersion Of Silica Nanoparticles Research Articles

Nanostructured composite membrane with cross-linked sulfonated poly(arylene ether ketone)/silica for high-performance polymer electrolyte membrane fuel cells under low relative humidity

Proton exchange membranes (PEMs) consisting of cross-linked sulfonated poly(arylene ether ketone) with silica nanoparticles (CL-SPAEK/silica) are developed for fuel cell applications under low relative humidity (RH). CL-SPAEK/silica is prepared by the reduction reaction of the synthesized SPAEK, followed by a sulfonation reaction between the benzophenone moieties of SPAEK and the hydroxyl groups of silica nanoparticles. The cross-linked structure of CL-SPAEK/silica enhanced proton conductivity that attributed to the synergistic effect of well-connected hydrophilic proton channels and improved the dispersion of silica nanoparticles in the polymer matrix. The nanostructure of the membranes was investigated by field-emission transmission electron microscopy (FE-TEM), atomic force microscopy (AFM) and small angle X-ray scattering (SAXS). Furthermore, CL-SPAEK/silica exhibited enhanced mechanical stability due to the effectively cross-linked networks between SPAEK and silica.

BS12-assisted flotation for the intensification of SNPs separation from CMP wastewater using a novel flotation column

In view of the extremely small size, high stable dispersion and intricate colloidal nature of silica nanoparticles (SNPs) in chemical mechanical polishing (CMP) wastewater, they might not only have hazards for environment and human health, but also cause low separation efficiency by classical water-treatment processes. Thus, it would be an important challenge to develop an efficient flotation technology for the separation SNPs. For this propose, this paper firstly presented the interaction between SNPs and dodecyl dimethyl betaine (ambient-friendly surfactant). Secondly, a novel flotation column was developed for strengthening interfacial adsorption by micro-bubbles and enhancing foam drainage by internal of regular-decagonal hollow frustum (RHF). One vital finding was that the mixture of micro-bubbles and macro-bubbles was conducive to improving the flotation performance. Under the suitable operating conditions, the enrichment ratio (E) and recovery percentage (R) of SNPs could reach 30.4±1.5 and 90.8±4.5%, respectively. The great E and R were obtained simultaneously, revealing a good participation of RHF in the flotation. Without a doubt, owing to the low chemical reagent addition and the high flotation performance, it was clear that our flotation has huge implications for the separation of nanoparticles from their wastewaters.

Impact of silica nanoparticles dispersion on the dielectric and electro-optical properties and absorption spectra of host ferroelectric liquid crystal

ABSTRACTThe present work concerns with the investigation of the effect of dispersion of Silica (SiO2) nanoparticles (NPs) in host ferroelectric liquid crystal (FLC) KCFLC10S on the dielectric and electro-optical properties and ultraviolet-visible (UV-VIS) absorption spectra of the pristine and dispersed systems. We have found that the dispersion of SiO2 NPs in the host FLC strongly influences the various properties of dispersed systems. No evidence of aggregates and clumps in the dispersed system has been observed. Due to SiO2 NPs dispersion, a rapid decrease in dielectric permittivity ε’, increase in conductivity σ with frequency, increase in spontaneous polarisation Ps and decrease in switching time with bias voltage have been observed. Based on the absorption spectra, we have also made an attempt to link the electro-optical and dielectric response with the mechanism of FLC–NPs interactions.

Ionic liquid‐based organic–inorganic hybrid electrolytes: Impact of in situ obtained and dispersed silica

ABSTRACTOrganic–inorganic hybrid electrolytes based on PEO‐NaTFSI‐ionic liquid (HMIMTFSI)‐silica (in situ production via sol gel process) are being reported in this article. The variation in conductivity with ionic liquid (IL) addition has been explained on the basis of number of free TFSI anions evaluated using ATR‐IR data. The deconvolution of the IR spectra of these hybrid electrolytes has given evidence of ion‐pair formation which has been compared vis‐á‐vis the conductivity variation. The hybrid electrolyte with maximum conductivity comprises the highest number of free imide ions and has lowest glass transition temperature. FESEM has displayed a porous and layered surface morphology with dispersed silica nanoparticles. In addition, the optimized hybrid electrolyte has been compared with 5 wt% (limit of mechanical stability) ex situ silica added composite where the temperature cycling of conductivity has shown that the ex situ dispersed hybrid electrolytes do not retrace their conductivity path contrary to the in situ prepared hybrid electrolytes. This behavior has been explained to be due to the hindrance offered by the ex situ added silica in the recrystallization kinetics of PEO. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 207–218

Wettability alteration of sandstones by silica nanoparticle dispersions in light and heavy crude oil

Unlike conventional oil production methods, enhanced oil recovery (EOR) processes can recover most oil products from the reservoir. One method, known as wettability alteration, changes the hydrophilicity of the reservoir rock via decreased surface interactions with crude oils. The mitigation of these attractive forces enhances petroleum extraction and increases the accessibility of previously inaccessible rock deposits. In this work, silica nanoparticles (NPs) have been used to alter the wettability of two sandstone surfaces, Berea and Boise. Changes in wettability were assessed by measuring the contact angle and interfacial tension of different systems. The silica NPs were suspended in brine and a combined solution of brine and the Tween®20 nonionic surfactant at concentrations of 0, 0.001, and 0.01 wt% NP with both light and heavy crude oil. The stability of the different nanofluids was characterized by the size, zeta potential, and sedimentation of the particles in suspension. Unlike the NPs, the surfactant had a greater effect on the interfacial tension by influencing the liquid-liquid interactions. The introduction of the surfactant decreased the interfacial tension by 57 and 43% for light and heavy crude oil samples, respectively. Imaging and measurements of the contact angle were used to assess the surface-liquid interactions and to characterize the wettability of the different systems. The images reflect that the contact angle increased with the addition of NPs for both sandstone and oil types. The contact angle in the light crude oil sample was most affected by the addition of 0.001 wt% NP, which altered both sandstones’ wettability. Increases in contact angle approached 101.6% between 0 and 0.001 wt% NPs with light oil on the Berea sandstone. The contact angle however remained relatively unaffected by addition of higher NP concentrations, thus indicating that low NP concentrations can effectively be used for enhancing crude oil recovery. While the contact angle of the light crude oil plateaued, the heavy crude oil continued to increase with an increase in NP concentration; therefore indicating that a maximum contact angle in heavy crude oil was not yet achieved. The introduction of NPs in light and heavy crude oil samples altered both the Berea and Boise sandstone systems’ wettability, which in turn indicated the efficacy of the silica NPs and surfactants in generating a more water-wet reservoir. Consequently, silica NPs and surfactants are most promising for EOR across the range of oil types.

The agglomeration state of nanoparticles can influence the mechanism of their cellular internalisation

BackgroundSignificant progress of nanotechnology, including in particular biomedical and pharmaceutical applications, has resulted in a high number of studies describing the biological effects of nanomaterials. Moreover, a determination of so-called “critical quality attributes”, that is specific physicochemical properties of nanomaterials triggering the observed biological response, has been recognised as crucial for the evaluation and design of novel safe and efficacious therapeutics. In the context of in vitro studies, a thorough physicochemical characterisation of nanoparticles (NPs), also in the biological medium, is necessary to allow a correlation with a cellular response. Following this concept, we examined whether the main and frequently reported characteristics of NPs such as size and the agglomeration state can influence the level and the mechanism of NP cellular internalization.ResultsWe employed fluorescently-labelled 30 and 80 nm silicon dioxide NPs, both in agglomerated and non-agglomerated form. Using flow cytometry, transmission electron microscopy, the inhibitors of endocytosis and gene silencing we determined the most probable routes of cellular uptake for each form of tested silica NPs. We observed differences in cellular uptake depending on the size and the agglomeration state of NPs. Caveolae-mediated endocytosis was implicated particularly in the internalisation of well dispersed silica NPs but with an increase of the agglomeration state of NPs a combination of endocytic pathways with a predominant role of macropinocytosis was noted.ConclusionsWe demonstrated that the agglomeration state of NPs is an important factor influencing the level of cell uptake and the mechanism of endocytosis of silica NPs.

Application of nano silica to improve self-healing of asphalt mixes

Nano silica due to its spherical shape, tiny size and higher density compared to bitumen, may have an inherent potential to improve hot mix asphalt (HMA) self-healing. In this research scanning electron microscopy (SEM) images were used to investigate size, morphology and dispersion of nano silica particles. Additionally, HMA self-healing mechanism was also examined by SEM. Furthermore, dynamic indirect tensile test (IDT) was used to evaluate HMA self-healing index. The SEM results indicated that bitumen mortar flowing into micro cracks may be one of the most important mechanisms of HMA self-healing. The experiment results also showed that modification of bitumen by nano silica promotes the ability of the HMA self-healing.

High Ion Conducting Nanohybrid Solid Polymer Electrolytes via Single-Ion Conducting Mesoporous Organosilica in Poly(ethylene oxide)

A novel mesoporous silica-based single-ion conductor for lithium-ion batteries was prepared via two-step selective functionalization of designated silica precursors into the inner pore wall of mesoporous silica. 2-[(Trifluoromethanesulfonylimido)-N-4-sulfonylphenyl]ethyl (TFSISPE) group was first incorporated as a silica precursor having an anionic weak-binding imide group, and a dense brush of oligo-poly(ethylene glycol) (oligo-PEG) moieties, solvating Li+, was cografted to produce functionalized mesoporous silica (FMS-TFSISPE) nanoparticles. FMS-TFSISPE showed a 2D hexagonal nanopore structure and a regular spherical shape with an average diameter of 50 nm. Poly(ethylene oxide) (PEO) was used to form a dispersion of the mesoporous silica nanoparticles into the polymer matrix. This new polymer–mesoporous silica nanohybrid solid electrolyte with the sole mobile Li ions (FMS-TFSISPE-PEO) exhibits attractive electrical, mechanical, and electrochemical properties. The ionic conductivity and storage modulus b...

Thermal rheology and microstructure of shear thickening suspensions of silica nanoparticles dispersed in the ionic liquid [C4mim][BF4

A stable dispersion of silica nanoparticles in a common ionic liquid [C4mim][BF4] that exhibits significant shear thickening is formulated by controlling the strength of hydrogen bonding between the nanoparticle surface and the anion of [C4mim][BF4]. Colloidal stability is demonstrated to be due to the formation of solvation layers, the properties of which are determined by scattering measurements. Time-temperature superposition measurements and the onset of yielding behavior in steady shear indicate the increase of particle-particle attraction and loss of stability of colloidal dispersions above 30 °C. Small angle neutron scattering and dynamic light scattering measurements confirm the reduction in solvation layering at elevated temperatures, leading to a transition from stable dispersion to unstable, attractive gel with increasing temperature (i.e., an inverse melting transition). It is demonstrated how controlling specific surface-anion interactions through chemical functionality can be used to formula...

Statement of Removal

ABSTRACTChemical flooding is an attractive approach to improve both microscopic and macroscopic sweep efficiencies due to the synergistic effects of interfacial tension reduction and mobility control improvement. In this study, the effect of two hydrophilic silica nanoparticles with different particle sizes of 7 and 25 nm on the phase behavior of surfactant solution and rheological behavior of polymer solution was investigated. Oil recovery experiments for the formulations with high viscosity and low interfacial tension were also conducted in a quarter five-spot glass micromodel. Phase behavior tests indicated that interfacial tension decreased dramatically (0.002 mN/m) due to the presence of smaller dispersed silica nanoparticles in surfactant solution. Rheological experiments showed that larger silica nanoparticles improve the viscosity of low molecular-weight polymer solution more than 20 cP in a wide range of shear rates. Oil recovery experiments revealed that dispersed silica nanoparticles in both surfactant and polymer solutions can improve heavy oil recovery significantly.

Statement of Removal

ABSTRACTPolymer flooding is an attractive branch of chemical enhanced oil recovery techniques. Regrettably, chemical and mechanical degradation reduces the effectiveness of polymer flooding. This paper explores the effects of silica nanoparticles on flow behavior of polymer solution in porous media by employing both rheological experiments and numerical simulations. Experimental results indicate that dispersed silica nanoparticles in polymer solution are responsible for polymer adsorption reduction and the solution viscosity improvement. Simulation results revealed that if the injectant has some dispersed silica nanoparticles, the cumulative heavy oil recovery and breakthrough time will be bettered compared to the conventional polymer flood.

The Effect of Nanoparticle Functionalization on Lubrication Performance of Nanofluids Dispersing Silica Nanoparticles in an Ionic Liquid

Recently, ionic liquids (ILs) have received an increasing attention as lubricants owing to their intriguing properties such as tunable viscosity, high thermal stability, low emissions, nonflammability, and corrosion resistance. In this work, we investigate how the incorporation of octadecyltrichlorosilane (OTS) functionalized silica nanoparticles (NPs) in 1-butyl-3-methylimidazolium (trifluoromethysulfony)imide influences the tribological properties and rheological properties of IL under boundary lubrication and elastohydrodynamic conditions, respectively. It was found that the coefficient of friction was depended on the concentration of NPs in IL with a concave upward functional trend with a minimum at 0.05 wt.% for bare silica NPs and at 0.10 wt.% for OTS-functionalized silica NPs. For steel–steel sliding contact, the presence of functionalized NPs in IL at the optimum concentration decreased the coefficient of friction by 37% compared to IL and 17% compared to IL with bare silica NPs. While IL with bare NPs demonstrated a shear thinning behavior for all concentrations, IL with functionalized NPs showed a Newtonian behavior at low concentrations and shear thinning behavior at high concentrations. Overall, this study provides new insights into the antifriction and antiwear additives for lubrication systems involving ILs.

Shape-Memory Behavior of Polylactide/Silica Ionic Hybrids

Commercial polylactide (PLA) was converted and endowed with shape-memory properties by synthesizing ionic hybrids based on blends of PLA with imidazolium-terminated PLA and poly[e-caprolactone-co-d,l-lactide] (P[CL-co-LA]) and surface-modified silica nanoparticles. The electrostatic interactions assist with the silica nanoparticle dispersion in the polymer matrix. Since nanoparticle dispersion in polymers is a perennial challenge and has prevented nanocomposites from reaching their full potential in terms of performance we expect this new design will be exploited in other polymers systems to synthesize well-dispersed nanocomposites. Rheological measurements of the ionic hybrids are consistent with the formation of a network. The ionic hybrids are also much more deformable compared to the neat PLA. More importantly, they exhibit shape-memory behavior with fixity ratio Rf ≈ 100% and recovery ratio Rr = 79%, for the blend containing 25 wt % im-PLA and 25 wt % im-P[CL-co-LA] and 5 wt % of SiO2–SO3Na. Dielectr...

Effect of nano-dispersed silica on the ion-conducting behavior of PMMA-based polymer gel electrolytes containing LiPF6

Nano-sized silica poly(methylmethacrylate)-based gel electrolyte containing lithium hexafluorophosphate (LiPF6) was synthesized by using different binary solvent mixture (propylene carbonate(PC) and dimethylformamide (DMF) in different volume ratio). Role of DMF in PC: Higher DMF content in PC-based electrolyte shows higher ionic conductivity at all polymer content and at wide temperature regions (10-70 °C). A small increment in ionic conductivity at lower content of polymer in liquid/gel electrolyte was observed and having maximum conductivity of 13.12 mS/cm at 25 °C. Stability (mechanically and electrically), viscosity and ionic conductivity of gel electrolytes were improved with the addition of nano-sized silica at ambient temperature. Ionic conductivity of nano-sized silica-based gel electrolyte does not change much over 5o–70 °C temperature range and is factor-wise only which make indispensable in different electrochemical devices. Also polymer gel electrolyte membranes as such and with dispersed silica nano-particles were characterized through scanning electron microscope to study the morphology of gel matrix.

Cytotoxicity of Nanoparticles in cultured THP-1 cells under the Standardized Condition of Size Distribution

Effect of nanoparticles on cellular toxicity can be influenced by size and/or size distribution of the tested nanoparticles. Therefore, it is necessary to fulfill the requirement of standardized dispersion when toxicity potencies of different types of nanoparticles are compared. In this study, probe-sonicator calibration for delivered acoustic power was performed according to the NANoREG protocol for standardized size-distribution of test nanoparticles including silica nanoparticles (SiNP), ceria nanopaaticles (CeNP), titania nanoparticles (TiNP), silver nanoparticles (AgNP) and zinc nanoparticles(ZnNP). Based on the protocol, the increase of water temperature by sonication power was monitored and Pac value was obtained. When the time of 8 minutes and 25% amplitude calculated from the Pac value was applied to the sonication of silica nanoparticles, size distribution reached to the effective level, 210 nm < size < 270 nm, Polydispersity index(PDI) < 0.46. The same acoustic power used in the dispersion of silica nanoparticles was applied to the other test nanoparticles, and cytotoxicity test was performed by MTS assay in cultured THP-1 cells treated with nanoparticles for 24 hrs. As results, Lethal Concentration 50% (LC50) of silver nanoparticles was 78.44 ppm, which was most toxic among the test nanoparticles. The toxicity compared by the LC50 seemed to be AgNP > SiNP > TiNP > ZnNP > CeNP.

Determination of the Exact Particle Radius Distribution for Silica Nanoparticles via Capillary Electrophoresis and Modeling the Electrophoretic Mobility with a Modified Analytic Approximation.

In this study, we use aqueous dispersions of amorphous silica nanoparticles of various sizes to investigate whether electropherograms recorded from capillary electrophoresis experiments can be converted directly into exact number-based particle radius distributions, provided that there is a relaxation effect-based size selectivity of the electrophoretic mobility and provided that the electrokinetic potential ζ of the particles can be regarded to be homogeneous over the surface of the particles, independent of the particle size. The results of this conversion procedure are compared with number-based particle radius distributions obtained from a large set of transmission electron microscopy (TEM) data. For this specific example, it is shown that the modified analytic approximation developed by Ohshima adequately describes the mobility-dependent relaxation effect and the electrophoretic mobility of the particle as a function of the reduced hydrodynamic radius and electrokinetic potential, which is a prerequisite for the presented procedure. Simultaneously, we confirmed that for the given Debye length/particle diameter ratio the electrokinetic surface charge density can be regarded to be size-invariant (including spherical geometry and planar limiting case). It is shown that the accuracy of the results of the developed method is comparable to that gained by a large set of TEM data, which is important when a precise description of the particle size distribution is needed to deduce conclusions regarding the underlying mechanism(s) of particle growth. The values obtained for the dispersion (width) of the distribution show only a small negative deviation, when compared with the TEM data (4-16%).

CO2 hydrogenation to methanol over CuO–ZnO–ZrO2–SiO2 catalysts: Effects of SiO2 contents

Catalytic CO2 hydrogenation to methanol is a powerful alternative for renewable energy, which can tackle both global warming through CO2 utilization and depletion of fossil fuels. However, the lack of efficient catalysts in terms of delivering sufficient activity and stability remains the major obstacles for practical application of such reaction. Herein, the introduction of silica as a promoter in a CuO-ZnO-ZrO2 catalytic system is reported. A series of CuO-ZnO-ZrO2-SiO2 catalysts were prepared by a reverse co-precipitation of Cu, Zn and Zr precursors with dispersed colloidal silica nanoparticles. The effect of silica content (0–5wt%) on the physicochemical properties of the resulting catalysts as well as their catalytic activity in CO2 hydrogenation were investigated. The catalysts were characterized by thermal gravimetric analysis (TG), X-ray diffraction (XRD), N2-sorption, N2O chemisorption, temperature programmed H2 reduction (H2-TPR), transmission electron microscope (TEM), time-resolved X-ray absorption spectroscopy (TRXAS), temperature programmed CO2 and H2 desorption (CO2 and H2-TPD). The promotional effect was characterized by a geometric modification which was most effective for low amounts of SiO2 (⩽1.5wt%). With the addition of 1wt% SiO2, an increase in methanol synthesis activity of 26% compared to the ternary SiO2-free system was observed. In addition to methanol synthesis activity, the stability—in terms of CO2 conversion-to-CO—was improved by the catalyst prepared with the presence of silica. Moreover, reaction mechanisms for CO2 hydrogenation to methanol and CO were discussed on the basis of correlations between microstructure and activity of the studied catalysts.

Preparation and characterization of highly dispersed silica nanoparticles via nonsurfactant template for fabric coating

Highly dispersed silica nanoparticles used for fabric coating were synthesized via nonsurfactant template sol–gel reaction with tetraethoxysilane (TEOS) and γ-glycidyloxypropyltrimethoxysilane (GPTMS) in the presence of dodecanol, alkaline catalyzer, and ethanol. With the optimum conditions of 4 g of dodecanol, 3 mL of alkaline catalyzer, and 30 wt% GPTMS, the silica particle size was 305 nm and the polydispersity index was 0.022. FT-IR spectra confirmed that the alkyl chain and epoxy group of GPTMS had been bonded onto the surface of silica nanoparticles due to the characteristic peaks at 2980 and 910 cm−1. The GPTMS-modified silica nanoparticles presented higher dispersion compared with the unmodified particles from SEM micrographs. The anti-ultraviolet property and rubbing fastness of the coated fabrics were enhanced as the doped amount of modified silica nanoparticles were increased to 5 wt%. The nonsurfactant template sol–gel method presents simple, facile, and cost-effective potential on the promising application of preparing highly dispersed silica nanoparticles.

2D pair distribution function analysis of anisotropic small-angle scattering patterns from elongated nano-composite hydrogels.

Small angle scattering (SAS) on polymer nanocomposites under elongation or shear flow is an important experimental method to investigate the reinforcement effects of the mechanical properties by fillers. However, the anisotropic scattering patterns that appear in SAS are very complicated and difficult to interpret. A representative example is a four-spot scattering pattern observed in the case of polymer materials containing silica nanoparticles, the origin of which is still in debate because of the lack of quantitative analysis. The difficulties in the interpretation of anisotropic scattering patterns mainly arise from the abstract nature of the reciprocal space. Here, we focus on the 2D pair distribution function (PDF) directly evaluated from anisotropic scattering patterns. We applied this method to elongated poly(N,N-dimethylacrylamide) gels containing silica nanoparticles (PDAM-NP gel), which show a four-spot scattering pattern under elongation. From 2D PDFs, we obtained detailed and concrete structural information about the elongated PDAM-NP gel, such as affine and non-affine displacements of directly attached and homogeneously dispersed silica nanoparticles, respectively. We proposed that nanoparticles homogeneously dispersed in the perpendicular direction are not displaced due to the collision of the adsorbed polymer layer during elongation, while those in the parallel direction are displaced in an affine way. We assumed that this suppression of the lateral compression is the origin of the four-spot pattern in this study. These results strongly indicate that our 2D PDF analysis will provide deep insight into the internal structure of polymer nanocomposites hidden in the anisotropic scattering patterns.

Templated synthesis of nano-sized silica in confined amorphous space of polypropylene

A template method is a powerful technique to tailor the morphology of formed nanomaterials. The present paper for the first time demonstrated the sol-gel reaction templated by the higher-order structure of semi-crystalline polymer. Silicon alkoxide was impregnated into the amorphous space of polypropylene (PP) with the aid of supercritical CO2, and subsequently converted into uniformly dispersed silica nanoparticles. The size and anisotropy of silica nanoparticles were controlled through the amorphous thickness of PP that was preliminarily defined through the crystallization process. We also studied the impact of the silica morphology on physical properties of resultant PP/silica nanocomposites. The silica morphology was systematically varied, keeping relatively uniform dispersion. We revealed that the storage modulus of the nanocomposites was well correlated with the size and anisotropy of the nanoparticles.