Effect Of Surface Active Agents Research Articles

Synergistic effect of surface active agent in defect passivation by for ambient air-synthesized halide perovskite solar cells

The unavoidable defect states located on the surface or grain boundaries (GBs) of the perovskite film can seriously deteriorate the performance and stability of perovskite solar cells (PSCs). In this work, an efficient and low-cost surface-active agent, sodium laurylsulfonate (SLS) has been incorporated into perovskite precursors in order to achieve effective defect passivation of humid air-fabricated PSCs. The zwitterionic SLS agent can not only improve crystallinity of perovskite film but also play the role of defect passivation originated from both negative- and positive-charged defect states. Density Functional Theory (DFT) calculation proves that the sulfonic acid group S=O and Na+ cations in SLS passivator can bond with the uncoordinated lead and halogen ions, leading to the suppression of carrier non-radiative recombination. As a result, the performance of champion device with SLS additives improves from 16.68 to 19.93%. Moreover, SLS passivation agent can also enhance the long-term stability of unencapsulated devices under ambient condition, which maintains 91% of its initial efficiency after 21 days. This study probes into the zwitterionic surface active agent with π-conjugated system for long term defect passivation of perovskite optoelectronic devices.

RETRACTED ARTICLE: Enhanced dissolution and oral bioavailability of poorly water-soluble herb (Kaempferia parviflora) extract using solid dispersions: effect of surfactants and concentrations

Kaempferia parviflora (KP) is a Thai traditional herb. The primary pharmacologically active substances are methoxyflavones, namely, 5,7-dimethoxyflavone, 5,7,4′-trimethoxyflavone, and 3,5,7,3′,4′-pentamethoxyflavone. These methoxyflavones are poorly soluble in water and thus have low oral absorption. In previous research, dichloromethane-extracted KP (KPD) and Kollicoat® IR (PVA-co-PEG) at a 1:1 ratio were dissolved in dichloromethane and used to produce a solid dispersion (KPD/PVA-co-PEG). In this study, the effects of surface-active agents in the solid dispersion system on dissolution and bioavailability were investigated, employing a series of concentrations (1%, 3%, and 6% w/w) of various surfactants (polysorbate 20, polysorbate 60, polysorbate 65, sorbitan ester 20, sorbitan ester 40, and sorbitan ester 80). The highest dissolution profiles were found (approximately 100% dissolution) when using polysorbate 20 at a concentration of 6% w/w (PS20-6) and these corroborated with the results from the surface free energy determination. The bioavailability of methoxyflavones was studied in Wistar rats: compared to KPD, AUC of KPD/PVA-co-PEG and PS20-6, they were 3.71- and 4.88-times higher, respectively. These results suggest that the solid dispersion-based KPD/PVA-co-PEG may be able to modify the dissolution profiles and oral absorption, and the surfactant-in-solid-dispersion system PS20-6 can be particularly effective.

A pressure-decay method to determine influence of a surface-active agent on interface and internal resistances to gas–liquid mass transfer

When gas dissolves into a liquid, interface resistance can limit the mass flux. Increasing or decreasing interface resistance by means of surface-active agents is of interest in applications ranging from biomedicine to petroleum recovery. This paper describes a pressure-decay methodthat allows systematic investigation of both interface resistance and internal (diffusive) resistance during gas-to-liquid mass transfer; introduces a mathematical modeling approach that determines both resistances simultaneously; and provides experiments in which only the interface resistance varies. In the pressure decay method, the system pressure is recorded as gas transfers across the gas/liquid interface and diffuses within the liquid. It allows initiating the experiment at a prescribed pressure with high reproducibility, facilitating the interpretation of a series of experiments. The exact solution of the 1D resistance-in-series model is derived. An accurate approximation is further reported to analyze experiments conveniently. The interface resistance is systematically varied in a static nitrogen/water system by adding small concentrations of oleic acid. As the concentration of oleic acid increases, the mass transfer coefficient decreases or the interface resistance increases. The effect is significant: at a concentration of 2 ppm, at which concentration the interface resistance is almost four times greater than that for pure water. The oleic acid has little effect on the diffusion coefficient of nitrogen in water due to its low concentration. The model comparison indicates the range of Biot number when the interface resistance or internal resistance must be accounted for. The characteristic chart can effectively contribute to a qualitative analysis of the gas–liquid mass transfer process when the effect of surface-active agents is considered.

Effect of Surface Active Agent (SAA) on 50/70 Bitumen Foaming Characteristics.

To ensure the standard properties of half-warm asphalt (HWA) mixes produced with foamed bitumen, the binder needs to have the best possible characteristics. One way to attain this is to modify the bitumen before it is foamed. The 50/70 penetration bitumen used in this study, was modified with a surface active agent (SAA) at different rates (0.2%, 0.4%, and 0.6% by wt.). The effect of the modifier on the bitumen properties (penetration, softening point, the Fraass breaking point, dynamic viscosity at 60 °C, 90 °C, and 135 °C) and on the binder foaming parameters (expansion ratio - ER, half-life - HL, foam index - FI) was investigated and the optimum quantity of foaming water was determined. Statistical analysis of the results showed that the addition of 0.6% SAA had the most beneficial effect on the set of 50/70 bitumen standard properties and foaming characteristics.

Effect of surface active agent on bubble-electrospun polyacrylonitrile nanofibers

Sodium dodecyl benzene sulfonates were used as a surfactant to obtain polyacrylonitrile nanofibers by a modified bubble-electrospinning using a copper cone-shaped air nozzle. The properties of the electrospun solutions were investigated using viscosity meter, conductivity meter and rheometer, and the effects of sodium dodecyl benzene sulfonates concentration on the morphology, mechanical property and production of polyacrylonitrile nanofibers were studied. The results showed the addition of sodium dodecyl benzene sulfonates could effectively decrease the viscosity of the solution, increase the electric conductivity of the solution, and promote the generation of bubbles, which resulted in enhancing tensile strength and decreasing the production of nanofibers.

Interfacial and Colloidal Forces Governing Oil Droplet Displacement: Implications for Enhanced Oil Recovery

Growing oil demand and the gradual depletion of conventional oil reserves by primary extraction has highlighted the need for enhanced oil recovery techniques to increase the potential of existing reservoirs and facilitate the recovery of more complex unconventional oils. This paper describes the interfacial and colloidal forces governing oil film displacement from solid surfaces. Direct contact of oil with the reservoir rock transforms the solid surface from a water-wet to neutrally-wet and oil-wet as a result of the deposition of polar components of the crude oil, with lower oil recovery from oil-wet reservoirs. To enhance oil recovery, chemicals can be added to the injection water to modify the oil-water interfacial tension and solid-oil-water three-phase contact angle. In the presence of certain surfactants and nanoparticles, a ruptured oil film will dewet to a new equilibrium contact angle, reducing the work of adhesion to detach an oil droplet from the solid surface. Dynamics of contact-line displacement are considered and the effect of surface active agents on enhancing oil displacement discussed. The paper is intended to provide an overview of the interfacial and colloidal forces controlling the process of oil film displacement and droplet detachment for enhanced oil recovery. A comprehensive summary of chemicals tested is provided.

Synergic effect of SDBS and GA to prepare stable dispersion of CNT in water for industrial heat transfer applications

Dispersion of hydrophobic carbon nanotubes in water is challenging. Herein, efforts have been made to study the dispersive effect of surface active agents on multi-walled carbon nanotubes (MWCNT). A method was developed to prepare a stable dispersion of MWCNT using sodium dodecyl benzene sulfonate (SDBS) and gum arabic (GA). Effect of ultrasonication time and surfactant concentration was also investigated. Compared to pure SDBS and GA based dispersion, their mixture was found to be effective to obtain a better dispersion of MWCNT, reflecting a synergistic effect of this mixture due to electrostatic and steric hindrance mechanism of surfactants. Rheology of CNT nanofluids showed the Newtonian behavior as viscosity was independent of shear rate. The viscosity of CNT nanofluids was higher than that of water. The thermal conductivity of dispersion was much higher than that of base fluid. This study provides the bases for using mixed surfactant system to disperse MWCNT in the polar base fluid to prepare nanofluids having enhanced thermal conductivity which can be used for heat transfer applications.

Effects of surface-active agents on bubble growth and detachment from submerged orifice

Present study deals with the effects of surfactants on the dynamics of bubble growth and detachment from a submerged orifice. Experiments are conducted to study the quasi-static growth of air bubble in de-ionized (DI) water mixed with nonionic surfactant Triton X-100. For comparison, bubble growth in pure DI water is also studied. While high-speed imaging is used for flow visualization, instantaneous velocity field, at different stages of bubble growth, are captured via particle image velocimetry. The study also uses bubble pressure Tensiometer technique and Goniometer for measuring the surface tensions. Present investigation shows that the bubble detachment volume decreases with the increase in the surfactant concentration. Further, for low concentration of surfactant, the surface tension gradient influences the flow field significantly and aid the bubble detachment.

Effects of surface active agents on DNAPL migration and distribution in saturated porous media

Dissolved surface active agents such as surfactant and natural organic matter can affect the distribution and fate of dense nonaqueous liquids (DNAPLs) in soil and groundwater systems. This work investigated how two common groundwater surface active agents, humic acid (HA) and Tween 80, affected tetrachloroethylene (PCE) migration and source zone architecture in saturated porous media under environmentally relevant conditions. Batch experiments were first conducted to measure the contact angles and interfacial tensions (IFT) between PCE and quartz surface in water containing different amount of surface active agents. Results showed that the contact angle increased and IFT decreased with concentration of surface active agent increasing, and Tween 80 was much more effective than HA. Five 2-D flow cell experiments were then conducted. Correspondingly, Tween 80 showed strong effects on the migration and distribution of PCE in the porous media due to its ability to change the medium wettability from water-wet into intermediate/NAPL-wet. The downward migration velocities of the PCE in three Tween 80 cells were slower than those in the other two cells. In addition, the final saturation of the PCE in the cells containing surface active agents was higher than that in the water-only cell. Results from this work indicate that the presence of surface active agents in groundwater may strongly affect the fate and distribution of DNAPL through altering porous medium wettability.

Effect of surface-active agent on morphology and properties of electrospun PVA nanofibres

After the addition of a surface-active agent, sodium dodecyl benzene sulfonate (SDBS), electrospun polyvinyl alcohol (PVA) nanofibres showed a significant enhancement in the mechanical properties, such as improved tensile strength and elongation at break. The improved crystallinity and strong intermolecular hydrogen bonds between the molecules of SDBS and PVA were the two main factors that improved the mechanical properties. In addition, a sharp decrease in surface tension of PVA solution with the addition of SDBS was observed, and the protruding droplet at the tip of needle diminished in the electrospinning process.

Effect of surface active agents on the rheological properties and solubility of layered double hydroxides-modified asphalt

Layered double hydroxides (LDHs) modified asphalt is a typical solid-liquid mixture that is concentrated suspensions of solid particles in solutions. The influence of dodecyl benzenesulfonic acid (DBSA) and polyvinyl alcohol (PVA) on the rheological properties and solubility of LDHs modified asphalt (LMA) were investigated by dynamic shear rheometer, molecular dynamic simulations and optical microscopy. Research results indicated that the addition of DBSA or PVA to LDHs modified asphalt resulted in enhancement of the cracking resistance, stress relaxation and creep behavior at lower temperature. The solubility parameters of surface active agent and LMA showed that PVA and DBSA can contribute to the solution of LDHs in asphalt. The effect of PVA was better than DBSA. The morphology of LMA implied that the distribution of LDHs was uniform when 0.5wt-% DBSA or PVA were added and increasing DBSA contents under certain levels increased the uniformity of LDHs..

Effect of Surface-Active Agents on Gas Holdup in an Aqueous Solution Containing Microbubbles

Effect of Surface-Active Agents on Gas Holdup in an Aqueous Solution Containing Microbubbles

NUMERICAL MODELING OF CAPILLARY–GRAVITY WAVES USING THE PHASE FIELD METHOD

In this paper, we present a numerical model based on the widely used finite element formulation to analyze in detail the effect of surface active agents on capillary–gravity wave parameters such as phase velocity and wave amplitude. Moreover, the effect of a physicochemical parameter, which is the ratio of surface concentration to surface tension is also considered. For a number of fluid samples covering a range of concentrations from 0 to 0.01 molar, the phase speed of waves propagating on the surface of the liquid is found to decrease monotonically as the concentration of the solution considered is increased up to a limit of 0.004 molar. This is attributed to the corresponding increase in capillary number. It is shown numerically that the Marangoni effects contribute to the interfacial dynamics for fluid with physicochemical parameter value greater than 0.5. Moreover, a grid refinement study shows accuracies and convergence orders of the numerical model.

Effect of Surface active agents , Chelating agents and Antibiotics on L-methionine fermentation by a multiple analogue resistant mutant Corynebacterium glutamicum X300

In this present study, it was intended to examine the effects of different surface active agents ( Tween 80 , Oleic acid, Linoleic acid , Palmatic acid , Stearic acid , Sodium Lauryl Sulfate , Lauryl methyl gluceth-10-hydroxypropyl diammonium chloride,Dimethyl dicatadecylammonium chloride,Tetramethyl ammonium hydroxide, Centimonium chloride and Bromidox ), antibiotics( Penicillin G, Erythromycin, Chloramphenicol , Streptomycin, Tetracycline-HCl and Gentamycin) and chelating agents (EDTA, NTA, DTPA, Catechol, Protocatechuate and Citrate ) on L-methionine fermentation by a multiple analogue resistant mutant Corynebacterium glutamicum X300. All these agents showed stimulatory effects on the fermentation process.

Effect of Surfactants on the Voltammetric Response and Determination of an Antihypertensive Drug Phentolamine at Boron Doped Diamond Electrode

A boron doped diamond electrode (BDDE) was used for the electroanalysis of Phentolamine by cyclic voltammetry (CV) and square wave voltammetry (SWV) in BR buffer (pH2.5). The current signal due to the oxidation process was a function of the amount of Phentolamine, pH of the medium, surfactants and scan rate. The results were compared with a glassy carbon electrode at the same condition. Phentolamine undergoes irreversible reaction at both the electrodes. However BDDE showed highly reproducible results with increased current intensity. The higher electrocatalytic behavior of BDDE was analyzed by electrochemical impedance spectroscopy which showed a decrease in the charge transfer resistance. The potential sweep rate dependence of Phentolamine oxidation (peak currents linearly proportional to ʋ1/2, with the range of 10 to 150mV S-1) indicates that the oxidation current is diffusion controlled with the negligible adsorption on the BDDE surface. Moreover the effect of surface active agents on the voltammetric behavior of Phentolamine was also studied. Three surfactants were used, an anionic type, sodium dodecyl sulfate (SDS), a cationic type cetyl trimethyl ammonium bromide (CTAB) and a non ionic type, triton X-100. Addition of SDS was found to enhance the current signal whereas CTAB and triton X-100 showed no effects. The use of SDS in the electrochemical determination of Phentolamine using SWV enhanced the detection limit from 0.71µg/ml in the absence of surfactant to 1.07 µg/ml when present.

Liquid–solid mass and heat transfer behavior of a concentric tube airlift reactor

Rates of liquid–solid mass transfer and heat transfer (by analogy) at the downcomer of concentric tube airlift reactor were studied by an electrochemical technique which involved measuring the limiting current of the cathodic reduction of ferricyanide ion in a large excess of sodium hydroxide. Variables studied were: superficial air velocity, physical properties of the solution and the effect of surface active agents. The data were correlated by the equation:j=0.096(Re·Fr)-0.14Surface active agents were found to decrease the rate of mass transfer by an amount ranging from 54% to 84% depending on surfactant concentration. The importance of the present results for the design and operation of cooling jackets used to cool airlift reactors was highlighted. Also the possibility of using airlift reactors as low cost electrochemical and catalytic reactors to conduct liquid–solid diffusion controlled reactions, especially those involving gaseous reactants, was discussed, as in electrochemical air pollution control to remove pollutants such as SO2, Cl2, H2S and nitrogen oxides, in which case the airlift reactor acts simultaneously as a gas scrubber and a reactor.

Effects of surface active agents on hydrodynamics and mass transfer characteristics in a split-cylinder airlift bioreactor with packed bed

The effects of three types of surface active agents (containing SDS, HCTBr and Tween 40) with various concentrations (0–5ppm) on the hydrodynamic and oxygen mass transfer characteristics in a split-cylinder airlift bioreactor with and without packing were investigated. It was observed that in the surfactant solutions, surface tension of the liquid decreased and smaller bubbles were produced in comparison with pure water. So, surfactants presence strongly enhanced mixing time and gas hold-up although oxygen mass transfer coefficient and the liquid circulation velocity reduced. Furthermore, the packing installation enhanced the overall gas–liquid volumetric mass transfer coefficient by increasing flow turbulency and Reynolds number compared to an unpacked column. The packing increased gas hold-up and decreased bubbles size and liquid circulation velocity.

Effect of Surface Active Agent on Defibering for Sepiolite Fiber Bundles

The cationic surfactant-octadecyl trimethyl ammonium chloride was added to the mixture of sepiolite powders and water with mechanical stirring. The effect of cationic surfactant on the defibering of fiber bundles was studied. The samples were characterized by X-Ray diffraction (XRD), bulk density, scanning electron microscope (SEM), FT-IR spectrum (FTIR) and thermal conductivity. The results indicated that the surface active agent could protect the structure of sepiolite fibers effectively, the bulk density and the thermal conductivity of the fibers could reach 0.06g/cm3 and 0.042W/(m.K), respectively.

On the effect of surface active agents and their structure on the temperature-induced changes of normal and waxy wheat starch in aqueous suspension. Part II: A confocal laser scanning microscopy study

The location and penetration patterns of two fluorescently labelled, surface active molecules into normal and waxy wheat starch granules prior, during and after the temperature-induced gelatinization were studied by means of confocal laser scanning microscopy (CLSM). Amphiphilic dyes were found to have a tendency to penetrate wheat starch granules in aqueous suspension. The penetration patterns were however found to be dependent on the contact time, type of starch and the chain length (C 12 vs. C 16) of the amphiphilic dye. The penetration of amphiphilic dyes through the starch granule matrix proved to be less restricted in waxy than in normal wheat starch. For a given type of starch, the penetration of the longer chain dye was more constrained than that of the shorter chain one. The extent to which the dye diffuses into the granule matrix as it gelatinizes is also affected by the chain length of the dye, diffusion of the shorter chain dye occurring more profusely and at lower temperatures than for the longer chain one. These differences are suggested to be related to the dissociation temperature of the AM-amphiphilic dye complexes.

On the effect of surface active agents and their structure on the temperature-induced changes of normal and waxy wheat starch in aqueous suspension. Part I. Pasting and calorimetric studies

Pasting and calorimetric studies of normal and waxy wheat starch were performed in the presence of a series of ionic (sulphates, trimethyl ammonium bromides) and non-ionic (monoglycerides, maltosides) short (12 carbon atoms) and long (16 carbon atoms) n-alkyl chain surfactants. With the exception of the alkyl ammonium bromides, all of the short chain surfactants lower the pasting temperature (PT) in normal wheat starch, while the long chain surfactants have the opposite effect. Contrary, regardless of their chain length, all ionic surfactants lower the PT in waxy wheat starch while the non-ionic surfactants induce small, sometimes almost negligible changes in the PT. Calorimetric studies revealed the absence of a direct connection between the effect of surfactants on the onset of the starch gelatinization transition and the PT. However, in the presence of all surfactants, except the alkyl ammonium bromides, the PT of normal wheat starch was found to lie within or very close the temperature range within which the dissociation of the amylose–surfactant complexes takes place. Waxy wheat starch, in contrast, pasted at temperatures that fell within the temperature range of the starch gelatinization transition. This is taken as evidence of the existence of a correlation between the PT and the dissociation of the amylose–surfactant complexes.