Kinds Of Silica Nanoparticles Research Articles

Roughness surface of raspberry-shaped silica nanoparticles effect on shear thickening colloidal suspensions

Control over the surface roughness of silica nanoparticles can offer exciting opportunities to increase the rheological properties of the silica-based shear thickening fluids. Designing surface roughness as a significant tool indicates the possibility of connecting distinct rheological phenomena and surface chemical functionalized materials. We have experimentally synthesized two kinds of silica nanoparticles with different particle size and different functional groups at the end, which can be combined via chemical covalent coupling to generate raspberry-shaped silica nanoparticles. The dynamic viscosity of the shear thickening fluids was evaluated by rheological experiments. And the maximum impact force of puncture and drop hammer experiments were performed for composite shear thickening materials with different factors. The results showed that the essential contribution of silica nanoparticles surface roughness and covalent force illustrate that stress-activated frictional contacts can play a key role in this shear thickening phenomena. We tried to propose a damage mechanism of the shear thickening materials. The results indicate that the roughness, morphology and diameter of particles, the thickening effect of shear thickening fluids with higher volume fraction, the increase of both the number of layers and the impregnation content can significantly improve the mechanical properties of the materials.

Waterborne polyurethane/silica nanocomposites based on electrostatic interaction: Interfacial interactions and properties

To study the effect of electrostatic interaction on the interface and mechanical properties of nano-composites, two kinds of silica nanoparticles with positive and negative charges were prepared and introduced into waterborne polyurethane (WPU) emulsion with negative charges to prepare composite emulsion and film. Molecular dynamics simulation and instrumental characterization were used to investigate the properties of nanoparticles and hybrid films. Molecular dynamics simulation results showed that WPU/SiO2(+) nanocomposite demonstrated higher interfacial free energy, lower free volume fraction and diffusion coefficient than those of WPU/SiO2(−) nanocomposite. The mechanical properties of the composite films indicated that there is no positive effect on the mechanical properties as the charges of SiO2 and WPU keep the same. Therefore, the mechanical properties of the composite films can be effectively enhanced by introducing positively charged SiO2, and the optimized introduction amount is 1 %. SEM images of the cross-section for the film show that SiO2(+) exhibits higher interfacial interaction strength with the WPU matrix than SiO2(−). Accordingly, molecular dynamics simulation and instrumental analysis afford similar results.

Exploration of synthesizing fluorescent silicon nanoparticles and label-free detection of sulfadiazine sodium

Herein, silica nanoparticles (SiNPs) with blue-fluorescence have been originally synthesized through one facile hydrothermal way, and this kind of SiNPs were water-soluble with the relative quantum yield of around 6%. Meanwhile, N-(triethoxysilylpropyl) urea severed as the silica source, while potassium hydrogen phthalate as the doping reagent. Also, SiNPs exhibited the acceptable stability and excitation-dependent fluorescence property. Moreover, their surfaces of the obtained SiNPs were equipped with multiple functional groups including -Si-O-Si-, -Si-H, –COOH, –NH2 and –OH. Importantly, the fluorescence of SiNPs could be specifically quenched by sulfadiazine sodium (SD-Na), thus achieving a label-free detection of SD-Na, which displayed a wide linear response in the range of 0.8 μM–800 μM with a detection limit of 1.02 μM. Additionally, we explored the mechanism of SiNPs sensing SD-Na on the basis of aggregation-induced quenching. To be specific, the particle size of SiNPs increased from 29.9 nm to 203.7 nm induced by the electrostatic interactions between SiNPs and SD-Na, which was further confirmed by high resolution transmission electron microscopy. Consequently, the proposed strategy here broadened the ways of assaying sulfadiazine sodium.

Improving Interaction at Polymer-Filler Interface: The Efficacy of Wrinkle Texture.

One of the main issues in preparing polymer-based nanocomposites with effective properties is to achieve a good dispersion of the nanoparticles into the matrix. Chemical interfacial modifications by specific coupling agents represents a good way to reach this objective. Actually, time consuming compatibilization procedures strongly compromise the sustainability of these strategies. In this study, the role of particles’ architectures in their dispersion into a poly-lactic acid matrix and their subsequent influences on physical-chemical properties of the obtained nanocomposites were investigated. Two kinds of silica nanoparticles, “smooth” and “wrinkled,” with different surface areas (≈30 and ≈600 m2/g respectively) were synthesized through a modified Stöber method and used, without any chemical surface pre-treatments, as fillers to produce poly-lactic acid based nanocomposites. The key role played by wrinkled texture in modifying the physical interaction at the polymer-filler interface and in driving composite properties, was investigated and reflected in the final bulk properties. Detailed investigations revealed the presence of wrinkled nanoparticles, leading to (i) an enormous increase of the chain relaxation time, by almost 30 times compared to the neat PLA matrix; (ii) intensification of the shear-thinning behavior at low shear-rates; and (iii) slightly slower thermal degradation of polylactic acid.

Fabrication of superhydrophobic and oleophobic thin films with high stability and self-healing property

We fabricated the superhydrophobic and oleophobic thin film via layer-by-layer assembling of three kinds of silica nanoparticles and chemical vapor depositing of 1H,1H,2H,2H-perfluorooctyl trichlorosilane (PFTS). The water contact angle of the thin film could reach to 170°, and the contact angle of ethylene glycol was 140°. The thin film could recover the superhydrophobic property after the oxygen plasma treatment. Meanwhile, the thin film could endure the xenon lamp irradiation and water impact experiments.

Cure Index demonstrates curing of epoxy composites containing silica nanoparticles of variable morphology and porosity

An image was taken by Cure Index on curability of epoxy with silica nanoparticles having variable morphology and porosity. Three kinds of silica nanoparticles with non-porous curved-rod, non-porous spherical, and mesoporous spherical microstructures were synthesized and characterized by Fourier-transform infrared spectroscopy, scanning electron microscopy (SEM) and Brunauer–Emmett–Teller analyses. Epoxy nanocomposites containing 0.1, 0.3, 0.5 wt.% of nanoparticles cured nonisothermally in differential scanning calorimetry (DSC) at different heating rates and the glass transition temperature (Tg) for fully-cured samples was estimated. Cure Index unravelled the effect of nanoparticle morphology and porosity on epoxy crosslinking. Good cure was unconditionally the case for systems containing 0.3 wt.% of mesoporous spherical nanoparticles due to appropriate dispersion of porous nanoparticles, as captured by SEM. By contrast, dependency of curing on heating rate and nanoparticle loading in the case of non-porous spherical and curved-rod particles was evidenced by partially agglomerated domains. The state of nanoparticle-polymer interaction was also inferred in view of network formation in the presence of nanosilica particles of various morphology and porosity, which was nicely monitored by the use of Cure Index.

Experimental Investigation of Amine-Surfactant CO2 Foam Stability Enhanced by Silica Nanoparticles

The CO2 foam generated by the conventional surfactants usually does not show long-term stability due to the substantial solubility and diffusivity of CO2 in water. Silica nanoparticles with different wettability and high adsorption energy on the gas–water interface can be used as a stabilizer to enhance the stability of the CO2 foam. In this study, nine kinds of nonionic amine surfactants were employed to generate the CO2 foam, while three kinds of silica nanoparticles were selected and added to improve the CO2 foam stability. The influences of various factors, including pressure, temperature, pH, surfactant, and nanoparticle, on the CO2 foam stability have been investigated. The experimental results show that without nanoparticles, the CO2 foam stability decreases with the increase of the number of EO groups in the ethoxylated amine surfactant, especially under high-temperature and high-pressure (HTHP) conditions. In general, the nanoparticles with a low concentration (<0.5 wt %) have little influence on the CO2 foam stability, but when the concentration of nanoparticle is enhanced high enough (1.0 wt %), the CO2 foam stability can be improved significantly. In particular, by adding 1.0 wt % nanoparticle of QS-150 to 0.5 wt % surfactant of C18N(EO)2/10, the CO2 foam stability has been increased 5–6 times, while the volume of generated CO2 foam has been increased by 17–31%. Therefore, in this study, the synergetic mechanisms between the amine surfactants and the silica nanoparticles to generate and stabilize CO2 foam have been identified.

Dispersion, crystallization behavior, and mechanical properties of poly(3-hydroxybutyrate) nanocomposites with various silica nanoparticles: effect of surface modifiers

Silica nanoparticles (NPs) with various surface properties were introduced in poly(3-hydroxybutyrate) (PHB) matrix and the their effect on the dispersion, crystallization behavior, and reinforcement in the nanocomposites was discussed in this article. Two kinds of commercial fumed silica NPs and two kinds of self-prepared sol-gel silica (bare and PEGylated) NPs were used. The cross-sectional SEM (scanning electron microscopy) images, provided the micrometer scale view (observation area: 12.6×8.2 μm2), showed that commercial fumed silica and PEG–silica NPs were aggregated and well-dispersed in PHB matrix, respectively. Similarly, Morisita’s analysis of TEM (transmission electron microscopy) images (observation area: 2.4×1.6 μm2) indicated that PEG-silica NPs were Poisson dispersed and commercial fumed silica NPs were serious aggregated in PHB matrix. However, SEM-EDX (energy dispersive X-ray analysis) Si-mapping micrographs, provided the millimeter scale view (observation area: 0.79×0.61 mm2), showed that four kinds of silica NPs were well-dispersed in PHB matrix. PLM (polarized light microscopy) images indicated that spherulite growth rate and morphology of PHB did not change obviously upon the addition of various silica NPs, except the PHB/PEG–silica system. PHB/PEG–silica showed a decreased spherulite growth rate, which was consistent with the DSC (differential scanning calorimetry) results, because the good miscibility between PHB and the grafted PEG chains on PEG–silica could decrease the polymer chain mobility during crystallization. The Young’s modulus and tensile strength of the PHB were enhanced by up to 34% and 63% by adding a small amount of PEG–silica. Fully well-dispersed PEG–silica NPs functioned as physical cross-linking centers for enhancing the mechanical properties of PHB but as retarding agents for reducing the crystallization rate.

Hierarchical self-assembly of squaraine and silica nanoparticle functionalized with cationic coordination sites for near infrared detection of ATP

Optical activity of hierarchical supramolecular assemblies based on organic dyes would create multiple functional architectures. In this work, three kinds of silica nanoparticles with or without functional groups were synthesized. For the first time, silica nanoparticles can induce positively charged squaraine (SQ) to aggregate to form supramolecular assemblies. Adenosine-5′-triphosphate (ATP) as building blocks was absorbed on the surface of silica nanoparticles through metal-anion coordination and electrostatic interactions, in which the aggregates of SQ was transferred to monomer. The thickness being composed of ATP and SQ on the outside of nanoparticles is about 5 nm. These supramolecular assemblies showed selective turn-on fluorescence response to ATP in near infrared (NIR) region over other ions through metal-anion coordination and electrostatic interactions. These functional silica nanoparticles possessing many advantages provide proof-of-principle “seed crystals” for construction of supramolecular assemblies and platforms for sensing with facile performance.

Spontaneous Imbibition Investigation of Self-Dispersing Silica Nanofluids for Enhanced Oil Recovery in Low-Permeability Cores

A new kind of self-dispersing silica nanoparticle was prepared and used to enhance oil recovery in spontaneous imbibition tests of low-permeability cores. To avoid the aggregation of silica nanoparticles, a new kind of silica nanoparticle was prepared through the surface modification with vinyltriethoxysilane and 2-mercaptobenzimidazole as modified agents. Transmission electron microscopy, Fourier transform infrared spectroscopy, dynamic light scattering, and ζ potential measurements were employed to characterize the modified silica nanoparticles. Dispersing experiments indicated that modified silica nanoparticles had superior dispersity and stability in alkaline water. To evaluate the performance of silica nanofluids for enhanced oil recovery compared to pH 10 alkaline water and 5 wt % NaCl solution, spontaneous imbibition tests in sandstone cores were conducted. The results indicated that silica nanofluids can evidently improve oil recovery. To investigate the mechanism of nanoparticles for enhanced oil...

Study on the effects of interfacial interaction on the rheological and thermal performance of silica nanoparticles reinforced epoxy nanocomposites

Abstract Three kinds of silica nanoparticles with different surface functional groups (amino groups, epoxide groups, and alkyl chain groups) were prepared and used as fillers in the amine-cured epoxy resin systems to investigate the relationship between the interfacial interaction and the rheological and thermal properties of silica nanoparticles reinforced epoxy nanocomposites. It has been found that attractive interfacial interaction significantly contributed to reduce the viscosity and dramatically enhance the viscosity stability as well as reinforce the thermal stability of epoxy nanocomposites. While repulsive interfacial interaction had considerable negative effects on both of the viscosity and viscosity stability. Glass transition temperature of epoxy nanocomposites is closely related to the effects of the interfacial interaction on the curing process of bulk epoxy. This study may also shed lights on the choice of an optimum surface functional group for other inorganic fillers to improve the rheological properties and meanwhile keep good comprehensive thermal properties for epoxy nanocomposites.

Effects of Fumed and Mesoporous Silica Nanoparticles on the Properties of Sylgard 184 Polydimethylsiloxane

The effects of silica nanoparticles on the properties of a commonly used Sylgard 184 polydimethylsiloxane (PDMS) in microfluidics were systemically studied. Two kinds of silica nanoparticles, A380 fumed silica nanoparticles and MCM-41 mesoporous silica nanoparticles, were individually doped into PDMS, and the properties of PDMS with these two different silica nanoparticles were separately tested and compared. The thermal and mechanical stabilities of PDMS were significantly enhanced, and the swelling characteristics were also improved by doping these two kinds of nanoparticles. However, the transparency of PDMS was decreased due to the light scattering by nanoparticles. By contrast, PDMS/MCM-41 nanocomposites showed a lower coefficient of thermal expansion (CTE) owing to the mesoporous structure of MCM-41 nanoparticles, while PDMS/A380 nanocomposites showed a larger elastic modulus and better transparency due to the smaller size of A380 nanoparticles. In addition, A380 and MCM-41 nanoparticles had the similar effects on the swelling characteristics of PDMS. The swelling ratio of PDMS in toluene was decreased to 0.68 when the concentration of nanoparticles was 10 wt %.

Effect of Nanoparticles on the Phase Behavior of Polystyrene/Poly(vinyl methyl ether) Blends with Different Polydispersities

Effects of two kinds of silica nanoparticles on the phase behavior of blends of poly (vinyl methyl ether) (PVME) and two kinds of polystyrene (PS), with the same number average molecular weight but different polydispersities, were studied by using optical microscopy. The addition of both the hydrophilic A200-SiO2 and hydrophobic R974-SiO2 nanoparticles made the miscibility become worse. The decrease in the phase separation temperatures of PS/PVME with polydisperse PS (pPS) was larger than that of PS/PVME with monodisperse PS (mPS) in the presence of A200-SiO2; the shifts of the phase separation temperatures of mPS/PVME and pPS/PVME were comparable for the incorporation of R974-SiO2. The addition of both kinds of silica accelerated the phase separation during the nonisothermal phase separation. The domain size changes of the phase morphology of mPS/PVME (50/50) and pPS/PVME (50/50) were almost the same during the nonisothermal phase separation in the presence of nanoparticles. During the isothermal phase separation, the introduction of silica slowed down the phase separation dynamics by hindering the phase structure transition. The morphology changes of pPS/PVME (50/50) were more evident than those of mPS/PVME (50/50) with the incorporation of SiO2.

Comparative study on the optical, surface mechanical and wear resistant properties of transparent coatings filled with pyrogenic and colloidal silica nanoparticles

We applied two kinds of silica nanoparticles, i.e. colloidal and pyrogenic ones, to improve the performance of transparent coatings on polymer substrates. The urethane–acrylate oligomer was mixed with varied concentrations of silica nanoparticles, spin-coated onto polycarbonate substrate and finally cured by ultraviolet rays. The resultant thickness of the coatings can be controlled in the range of 20–30 μm. The transmission electron microscopy revealed that both silica nanoparticles presented different dispersion states, i.e. mono-dispersion for the colloidal nanoparticles and floc-like dispersion for the pyrogenic ones. In comparison with the colloidal nanoparticles filled coatings, the pyrogenic ones exhibited much improved modulus, hardness and wear resistance, but slightly decreased optical properties such as transmittance, haze and gloss. The nanoparticle morphology, amorphous structure, dispersion state and particle–matrix interfacial bonding relating to these properties were discussed in the present study.