The Experts below are selected from a list of 2475 Experts worldwide ranked by ideXlab platform
D Grischkowsky - One of the best experts on this subject based on the ideXlab platform.
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Terahertz Time-Domain Spectroscopy Study of Silica Aerogels and Adsorbed Molecular Vapors
Journal of Physical Chemistry B, 2004Co-Authors: Jiangquan Zhang, D GrischkowskyAbstract:We report the terahertz time-domain spectroscopy (THz-TDS) study of hydrophobic and Hydrophilic Silica aerogels, and the adsorption of several molecular vapors in the Hydrophilic Silica aerogel. The hydrophobic and Hydrophilic samples have similar but discernible indices of refraction in the frequency range of 0.2−3.0 THz. Below 1.0 THz, the two samples have the same absorption, but starting from 1.0 THz, the absorption of the Hydrophilic sample increases more rapidly with frequency. For the Hydrophilic aerogel, a strong effect on adsorption is observed by THz-TDS for the vapors of water, heavy water, ammonia, methyl chloride, and methyl fluoride. The surface −OH groups can be replaced by −OD groups by dosing with heavy water, causing the change in the index of refraction and absorption. This replacement can be reversed by dosing the Hydrophilic aerogel with water vapor. The volumetric method is used to determine the adsorption amount, which shows that the adsorbed molecules are in the submonolayer form. ...
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terahertz time domain spectroscopy of submonolayer water adsorption in Hydrophilic Silica aerogel
Optics Letters, 2004Co-Authors: Jiangquan Zhang, D GrischkowskyAbstract:We report a terahertz time-domain spectroscopy study of the adsorption of water in Hydrophilic Silica aerogel. The adsorbed water is in submonolayer form and shows properties of index of refraction similar to those of bulk water but different absorption properties.
Zhifeng Jiang - One of the best experts on this subject based on the ideXlab platform.
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characterization and comparison of uniform Hydrophilic hydrophobic transparent Silica aerogel beads skeleton strength and surface modification
RSC Advances, 2015Co-Authors: Sekai Zong, Zhifeng JiangAbstract:Silica aerogel is a good adsorbent due to the large surface area and chemical stability. However, its inherent poor mechanical properties and hydrophobicity limit applications in water treatment. To improve the adsorption performance of Silica aerogel, uniform transparent Hydrophilic mesoporous Silica aerogel beads with highly degree of sphericity were synthesized through a facile aging immersion and ambient pressure drying route. The designed Hydrophilic Silica aerogel beads possessed the mesopores, mean diameter of approximately with the average pore size of 12.51 nm, the specific surface area of 582.52 m2 g−1, and the pore volume of 1.46 cm3 g−1. For comparison, Hydrophilic Silica aerogel beads without skeleton improvement and hydrophobic Silica aerogel beads were also obtained, respectively. The synthesized novel Hydrophilic Silica aerogel beads displayed a significantly improved adsorption performance with a favorable dye absorption capacity, superior to that of previously synthesised Silica-based aerogel beads materials. This study demonstrates a facile and low-cost route toward transparent Silica aerogel beads with macroscopic beads structures, which can be used as adsorbents, catalytic supports or the template to synthesize novel functional materials requiring high transmittance, high surface area and effective mass transport.
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Characterization and comparison of uniform Hydrophilic/hydrophobic transparent Silica aerogel beads: skeleton strength and surface modification
RSC Advances, 2015Co-Authors: Sekai Zong, Zhifeng JiangAbstract:Silica aerogel is a good adsorbent due to the large surface area and chemical stability. However, its inherent poor mechanical properties and hydrophobicity limit applications in water treatment. To improve the adsorption performance of Silica aerogel, uniform transparent Hydrophilic mesoporous Silica aerogel beads with highly degree of sphericity were synthesized through a facile aging immersion and ambient pressure drying route. The designed Hydrophilic Silica aerogel beads possessed the mesopores, mean diameter of approximately with the average pore size of 12.51 nm, the specific surface area of 582.52 m2 g−1, and the pore volume of 1.46 cm3 g−1. For comparison, Hydrophilic Silica aerogel beads without skeleton improvement and hydrophobic Silica aerogel beads were also obtained, respectively. The synthesized novel Hydrophilic Silica aerogel beads displayed a significantly improved adsorption performance with a favorable dye absorption capacity, superior to that of previously synthesised Silica-based aerogel beads materials. This study demonstrates a facile and low-cost route toward transparent Silica aerogel beads with macroscopic beads structures, which can be used as adsorbents, catalytic supports or the template to synthesize novel functional materials requiring high transmittance, high surface area and effective mass transport.
Ian T Norton - One of the best experts on this subject based on the ideXlab platform.
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competitive adsorption of surfactants and Hydrophilic Silica particles at the oil water interface interfacial tension and contact angle studies
Journal of Colloid and Interface Science, 2012Co-Authors: R Pichot, Fotios Spyropoulos, Ian T NortonAbstract:Abstract The effect of surfactants’ type and concentration on the interfacial tension and contact angle in the presence of Hydrophilic Silica particles was investigated. Silica particles have been shown to have an antagonistic effect on interfacial tension and contact angle in the presence of both W/O and O/W surfactants. Silica particles, combined with W/O surfactant, have no effect on interfacial tension, which is only dictated by the surfactant concentration, while they strongly affect interfacial tension when combined with O/W surfactants. At low O/W surfactant, both particles and surfactant are adsorbed at the interface, modifying the interface structure. At higher concentration, interfacial tension is only dictated by the surfactant. By increasing the surfactant concentration, the contact angle that a drop of aqueous phase assumes on a glass substrate placed in oil media decreases or increases depending on whether the surfactant is of W/O or O/W type, respectively. This is due to the modification of the wettability of the glass by the oil or water induced by the surfactants. Regardless of the surfactant’s type, the contact angle profile was dictated by both particles and surfactant at low surfactant concentration, whereas it is dictated by the surfactant only at high concentration.
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Competitive adsorption of surfactants and Hydrophilic Silica particles at the oil–water interface: Interfacial tension and contact angle studies
Journal of Colloid and Interface Science, 2012Co-Authors: R Pichot, Fotios Spyropoulos, Ian T NortonAbstract:Abstract The effect of surfactants’ type and concentration on the interfacial tension and contact angle in the presence of Hydrophilic Silica particles was investigated. Silica particles have been shown to have an antagonistic effect on interfacial tension and contact angle in the presence of both W/O and O/W surfactants. Silica particles, combined with W/O surfactant, have no effect on interfacial tension, which is only dictated by the surfactant concentration, while they strongly affect interfacial tension when combined with O/W surfactants. At low O/W surfactant, both particles and surfactant are adsorbed at the interface, modifying the interface structure. At higher concentration, interfacial tension is only dictated by the surfactant. By increasing the surfactant concentration, the contact angle that a drop of aqueous phase assumes on a glass substrate placed in oil media decreases or increases depending on whether the surfactant is of W/O or O/W type, respectively. This is due to the modification of the wettability of the glass by the oil or water induced by the surfactants. Regardless of the surfactant’s type, the contact angle profile was dictated by both particles and surfactant at low surfactant concentration, whereas it is dictated by the surfactant only at high concentration.
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mixed emulsifier stabilised emulsions investigation of the effect of monoolein and Hydrophilic Silica particle mixtures on the stability against coalescence
Journal of Colloid and Interface Science, 2009Co-Authors: R Pichot, Fotios Spyropoulos, Ian T NortonAbstract:Abstract The stability against coalescence of vegetable oil-in-water “food grade” emulsions in the presence of both surfactant (monoolein) and colloidal particles (Hydrophilic Silica) has been studied and compared to the stability of systems where only the low molecular weight surfactant or the colloidal particles act as the emulsifier. No attempt was made to stop the emulsions from creaming and the data presented for coalescence stability is for droplets in the creamed layer. These are severe conditions as the contact time between droplets in such closed packed conditions is very high or even infinite. These mixed emulsifier systems were found to induce long-term emulsion stability against coalescence via a synergistic “two-part” mechanism in which both the surfactant and colloidal particles components have specific functions. The role of the surfactant is to initially “delay” the re-coalescence phenomena and induce further droplet break-up during emulsification by rapidly covering the new (naked) interface and reducing interfacial tension in order to allow the time for the Silica particles to assemble at the oil/water interface and provide long-term stability. This dual manner by which mixed-emulsifier systems induced stability was found to depend on the concentrations of both monoolein and Silica particles.
Jiangquan Zhang - One of the best experts on this subject based on the ideXlab platform.
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Terahertz Time-Domain Spectroscopy Study of Silica Aerogels and Adsorbed Molecular Vapors
Journal of Physical Chemistry B, 2004Co-Authors: Jiangquan Zhang, D GrischkowskyAbstract:We report the terahertz time-domain spectroscopy (THz-TDS) study of hydrophobic and Hydrophilic Silica aerogels, and the adsorption of several molecular vapors in the Hydrophilic Silica aerogel. The hydrophobic and Hydrophilic samples have similar but discernible indices of refraction in the frequency range of 0.2−3.0 THz. Below 1.0 THz, the two samples have the same absorption, but starting from 1.0 THz, the absorption of the Hydrophilic sample increases more rapidly with frequency. For the Hydrophilic aerogel, a strong effect on adsorption is observed by THz-TDS for the vapors of water, heavy water, ammonia, methyl chloride, and methyl fluoride. The surface −OH groups can be replaced by −OD groups by dosing with heavy water, causing the change in the index of refraction and absorption. This replacement can be reversed by dosing the Hydrophilic aerogel with water vapor. The volumetric method is used to determine the adsorption amount, which shows that the adsorbed molecules are in the submonolayer form. ...
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terahertz time domain spectroscopy of submonolayer water adsorption in Hydrophilic Silica aerogel
Optics Letters, 2004Co-Authors: Jiangquan Zhang, D GrischkowskyAbstract:We report a terahertz time-domain spectroscopy study of the adsorption of water in Hydrophilic Silica aerogel. The adsorbed water is in submonolayer form and shows properties of index of refraction similar to those of bulk water but different absorption properties.
Aliyar Javadi - One of the best experts on this subject based on the ideXlab platform.
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influence of Hydrophilic Silica nanoparticles on the adsorption layer properties of non ionic surfactants at water heptane interface
Journal of Colloid and Interface Science, 2019Co-Authors: Hamid Vatanparast, Aliyar Javadi, R Miller, Milad Eftekhari, Alireza BahramianAbstract:Abstract There is a notable paucity of studies investigating the impact of charged nanoparticles on the interfacial behavior of nonionic surfactants, assuming that the interactions are negligible in the absence of electrostatic forces. Here, we argue about our observations and the existence of a complex interfacial behavior in such systems depending on the type and chemical structure of surfactant. This study set out to investigate the effects of interactions between Hydrophilic Silica nanoparticles (NP) and non-ionic surfactants on water/heptane dynamic interfacial properties using drop profile analysis tensiometry (PAT). Three surfactants were studied, namely Triton X-100 (significantly soluble in water phase), C12DMPO (well soluble in both phases) and SPAN 80 (oil-soluble). The different chemical structures and partition coefficients of the surfactants enabled us to cover possible interactions and differentiate between bulk and interfacial interactions. We observed that Hydrophilic Silica NPs had a negligible effect on the interfacial behavior of Triton X-100, that they increased the surface activity of C12DMPO when both compounds are initially in the aqueous phase. Most interestingly is that the added NPs generated unstable interfacial NP-surfactant complexes and reduced the pseudo-equilibrium interfacial tension of oil-soluble surfactant, Span 80, even though NPs and surfactants were in different bulk phases.
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Influence of Hydrophilic Silica nanoparticles on the adsorption layer properties of non-ionic surfactants at water/heptane interface.
Journal of Colloid and Interface Science, 2019Co-Authors: Hamid Vatanparast, Aliyar Javadi, Milad Eftekhari, Reinhard Miller, Alireza BahramianAbstract:Abstract There is a notable paucity of studies investigating the impact of charged nanoparticles on the interfacial behavior of nonionic surfactants, assuming that the interactions are negligible in the absence of electrostatic forces. Here, we argue about our observations and the existence of a complex interfacial behavior in such systems depending on the type and chemical structure of surfactant. This study set out to investigate the effects of interactions between Hydrophilic Silica nanoparticles (NP) and non-ionic surfactants on water/heptane dynamic interfacial properties using drop profile analysis tensiometry (PAT). Three surfactants were studied, namely Triton X-100 (significantly soluble in water phase), C12DMPO (well soluble in both phases) and SPAN 80 (oil-soluble). The different chemical structures and partition coefficients of the surfactants enabled us to cover possible interactions and differentiate between bulk and interfacial interactions. We observed that Hydrophilic Silica NPs had a negligible effect on the interfacial behavior of Triton X-100, that they increased the surface activity of C12DMPO when both compounds are initially in the aqueous phase. Most interestingly is that the added NPs generated unstable interfacial NP-surfactant complexes and reduced the pseudo-equilibrium interfacial tension of oil-soluble surfactant, Span 80, even though NPs and surfactants were in different bulk phases.
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the role of electrostatic repulsion on increasing surface activity of anionic surfactants in the presence of Hydrophilic Silica nanoparticles
Scientific Reports, 2018Co-Authors: Hamid Vatanparast, Farshid Shahabi, Alireza Bahramian, Aliyar Javadi, R MillerAbstract:Hydrophilic Silica nanoparticles alone are not surface active. They, however, develop a strong electrostatic interaction with ionic surfactants and consequently affect their surface behavior. We report the interfacial behavior of n-heptane/anionic-surfactant-solutions in the presence of Hydrophilic Silica nanoparticles. The surfactants are sodium dodecyl sulfate (SDS) and dodecyl benzene sulfonic acid (DBSA), and the diameters of the used particles are 9 and 30 nm. Using experimental tensiometry, we show that nanoparticles retain their non-surface-active nature in the presence of surfactants and the surface activity of surfactant directly increases with the concentration of nanoparticles. This fact was attributed to the electrostatic repulsive interaction between the negatively charged nanoparticles and the anionic surfactant molecules. The role of electrostatic repulsion on increasing surface activity of the surfactant has been discussed. Further investigations have been performed for screening the double layer charge of the nanoparticles in the presence of salt. Moreover, the hydrolysis of SDS molecules in the presence of Silica nanoparticles and the interaction of nanoparticles with SDS inherent impurities have been studied. According to our experimental observations, Silica nanoparticles alleviate the effects of dodecanol, formed by SDS hydrolysis, on the interfacial properties of SDS solution.
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surface behavior of Hydrophilic Silica nanoparticle sds surfactant solutions i effect of nanoparticle concentration on foamability and foam stability
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2017Co-Authors: Hamid Vatanparast, Alireza Bahramian, Aslan Samiee, Aliyar JavadiAbstract:Abstract Hydrophilic Silica nanoparticles have no tendency to adsorb at the water/air interface and they do not affect the surface behavior of pure water. In this paper, we show that this tendency remains unaltered by addition of anionic sodium dodecyl sulfate (SDS) surfactant, although the surface behavior of SDS solutions considerably changes with the addition of Silica particles. Employing dynamic tensiometry, surface rheology, foamability, and foam stability experiments in presence of variable amounts of Silica particles, we found that the surface activity of SDS molecules is significantly increased in the presence of nanoparticles and equivalently behaved as if higher concentrations of SDS are used. The so-called equivalent concentration values (EC) were separately measured using the tensiometry and foamability. The consistency of measured EC trends is discussed, and a new predictive tool for the foaming behavior of surfactant solutions is proposed based on the calculated EC trends from tensiometry and surface dilational rheology. The adsorption process and surface structuring of nanoparticles at the water/air interface were investigated by analyzing the surface pressure values as a function of drop surface area. We measured the standard deviation, STD, of drop shapes from their Laplacian profile during the drop compression process. It was found that STD-values abruptly change when particles form closely-packed surface structures. The STD trend is explained in detail and is shown it can be a very powerful tool for analyzing the surface adsorption and surface structuring of nanoparticles.
