Various Types Of Surfactants Research Articles

Electrodeposition and Characterization of Cr-MoS2 Composite Coatings

In this study, Cr-MoS2 composite coatings were electrodeposited from conventional Cr+6 baths containing different amounts of MoS2 particles and various types of surfactant (cationic and anionic). The effect of bath chemical composition on the coatings properties like their microstructure, morphology, chemical composition, corrosion behavior, surface roughness and microhardness was investigated using x-ray diffraction, scanning electron microscopy (SEM), energy-dispersive x-ray analysis, potentiodynamic polarization, electrochemical impedance spectroscopy, surface profilometry and Vickers microhardness measurement techniques, respectively. The results showed that incorporation of MoS2 particles into the composite coatings is very limited and Cr matrix with very low crystallinity will be electrodeposited at various experimental conditions. The presence of MoS2 particles in the bath (up to an optimum value) leads to the formation of the composite coatings with lower surface roughness values than that of conventional chromium coating. Although more MoS2 particles will be incorporated into the electrodeposits when the solid content of the bath increases, chromium cannot be electrodeposited from baths containing high amounts of MoS2 particles. Application of cationic surfactant promotes incorporation of particles into the Cr metallic matrix. Moreover, the presence of surfactant in the bath results in the formation of coatings with less microcracks. All the composite coatings have more hardness values than that of conventional chromium coating; maximum hardness is attributed to the coatings that were electrodeposited from baths containing no surfactant. The corrosion test results revealed that the smooth coatings containing more MoS2 particles and less microcracks exhibit more corrosion resistance than the other ones.

EFFECT OF SURFACTANT ADDITION ON THE NANOFLUIDS PROPERTIES: A REVIEW

The applications and usage of surfactants in the field of nanofluids heat transfer and its stability were performed the present literature review. The usage of surfactants has been employed for the following areas of nanofluids study: nanofluid heat transfer, nanofluid agglomeration and nanofluid enhancement stability. Generally, a few interesting has been achieved to study the effects of using the surfactants on the nanofluids properties such as pH, thermal conductivity, specific heat, electrical conductivity, viscosity and stability mechanism of nanofluid. The using nanofluid in real applications is taken into consideration by two key issues emerge: erosion and settlement but there aare possible difficulties related to these issues that need to be studied and solved prior to the using of nanofluid in commercial applications. In addition, this paper summarizes the theoretical and experimental studies on the effects of applied various types of surfactants in nanofluids. This work can serve as a ready reference for application of surfactants in nanofluids.

Variation of linear alcohols’ activity coefficients, referred to aqueous solutions of methanol, ethanol and 1-propanol, in the presence of various types of surfactants, studied by reversed – Flow Gas Chromatography

The Reversed – Flow Gas Chromatography (R.F.G.C.) technique, a version of Inverse Gas Chromatography, was used to study the influence of the number of carbon atoms on the activity coefficients of the three linear alcohols methanol, ethanol and 1–propanol in their mixtures with water, in the presence of the surfactants CTAB (cationic), SDS (anionic) and TRITON X – 100 (non – ionic). The found activity coefficients, increase with increasing the alcohols' number of carbon atoms at constant temperature and pressure, as well as at constant alcohol's and surfactant's concentration and decrease with increasing the alcohol's molar fraction (at constant surfactant's concentration), as well as with increasing the number of the surfactant's films (at constant alcohol's concentration). The values of activity coefficients found for the three used alcohols, in the absence of surfactants, are in good agreement with those calculated theoretically or found in the literature. The precision of the Reversed – Flow Gas Chromatography for measuring activity coefficients of alcohols is approximately high (94.12% for methanol, 99.26% for ethanol and 94.35% for 1–propanol), showing that R.F.G.C. is a precise method not only for measuring activity coefficients of alcohols, but also for studying the influence of various parameters (molecular formula of linear alcohol, type of surfactant, as well as alcohol's and surfactant's concentration) on the measured activity coefficients.

Influence of sonication and in vitro evaluation of nifedipine self-nanoemulsifying drug delivery system

In order to develop a self-nanoemulsifying system, three components, olive oil, Tween 80, and Capmul, were used to construct a ternary phase diagram that helped to find the optimum formulation, which was loaded with nifedipine. The effect of sonication on drug loading was also evaluated. After that, measurement of the droplet size, size distribution, zeta potential, and scanning electron microscopy were conducted for evaluation and characterisation of the formulations. The phase diagram of four formulations showed nanosizes below 200 nm; however, only one was selected to be loaded with nifedipine. The selected formulation had the lowest droplet size of 98 nm and size distribution 0.192, and was composed of 48% Tween 80, 32% Capmul, and 20% olive oil. The nifedipine self-nanoemulsifying drug delivery system (SNEDDS) showed a significant change in the particle size (97 nm) and size distribution (0.257) after sonication. Its zeta potential was -32.3 mV indicating good stability. The SEM photographs of nifedipine showed particles with spherical shape and smooth surface. Finally, a self-nanoemulsifying formulation containing nifedipine, loaded in olive oil, was successfully prepared by mixing the oil with various types of surfactants and co-surfactants. A significant nifedipine self-nanoemulsifying system was developed and significantly improved accordingly.

Comparison on Promotion Effect of Various Types of Surfactants on HCFC-141b Hydrate Induction Time

Cold storage in air conditioning based on refrigerant hydrate is a new-type energy saving technology to reduce initial investment and running cost of air conditioning equipments and improve system stability. Refrigerant hydrate is generated under critical temperature and pressure condition, while surfactant is an effective medium to promote its phase equilibrium. In this paper, in order to research such promotion effect, different type of surfactants with unique mechanism, SDS, Tween80 and Span80, n-BA were selected to compare the respective impact on HCFC141b hydrate induction time based on temperature curve. Experimental results showed that no obvious change had been discovered when no surfactant was added into pure water system, which coincided with phase equilibrium diagram of HCFC141b. All the four kinds of surfactants had realized promotion effect to various degrees. For each hydration system, a large gap existed between the longest and the shortest induction time in 6 groups of parallel experiments, meaning relatively poor system stability. Under the combined effect of Tween80 (2wt%), Span80 (0.1wt%) and n-BA (0.1wt%), average and the shortest induction time was 20.9min and 17.5min respectively, corresponding to the best promotion effect.

Amino acids: Building blocks for the synthesis of greener amphiphiles

ABSTRACTAmino acid-based amphiphiles have attracted much attention as environmentally friendly surfactants because of their biodegradability, low toxicity and the use of renewable sources of raw materials for their syntheses. With respect to molecular design, the amino acid-based architecture allows the possibilities of multiple structures of amphiphiles with varying head groups and chain lengths. This review focuses on the synthetic strategies for the development of various types of surfactants derived from amino acids. Their properties in terms of surface, biological and catalytic activities are illustrated.

ВПЛИВ ПОВЕРХНЕВО-АКТИВНИХ РЕЧОВИН НА ФЛЮОРЕСЦЕНТНІ ВЛАСТИВОСТІ ФЛУОРЕСЦЕЇНУ

The use of fluorescence as an analytical signal makes it possible to reduce the limits of detection of analytes. The study of spectral properties of luminophores is important for the development of new methods for analyzing various objects. The use of micellar systems enables to increase quantum yields by 2–10 times and fluorescence intensity by 3–80 times and reduce the limits of detecting analytes by 1–2 orders of magnitude. Organized media based on surfactants influence on the fluorescence of luminescent indicators and their complex compounds due to changes in their microspheric solution of their photophysical characteristics, aggregate state and microprobe nature. Cationic surfactants occupy a special place among cytotoxicants. Low levels of maximum permissible concentrations of cationic surfactants require the use of sensitive analytical methods that combine simplicity and availability with reliability and expressiveness. Known chemical and microbiological methods for the determination of cationic surface-active antiseptics, disinfectants and preservatives characterize by complexity and labor intensity and are not suitable for the operational control of their concentration in places of local use. Therefore, the purpose of the work was to study the influence of various types of surfactants on the fluorescence properties of fluorescein to develop a method for determining the content of ethonium. The influence of surface-active substances of different types on the fluorescence properties of fluorescein was investigate. The anionic surfactant almost does not effect on the intensity of the dye signal. Nonionic surfactant leads to a gradual decrease in the fluorescence intensity of fluorescein. The most visible influence was observe with adding into the solution cationic surface-active substances. There is harsh intensity decrease of the dye fluorescence with subsequent exit to the «plateau» in the system of fluorescein-cetylpyridinium chloride. The cationic surfactant ethonium works the same. Received results will laid in the basis of the method development of ethonium determination in the medical drugs.

Electroosmotic flow measurements in a freely suspended liquid film: Experimhents and numerical simulations.

Fluid flow profiles in free liquid films stabilised by anionic and cationic surfactants under an external electric field were investigated. Depthwise velocity fields were measured at the mid region of the free liquid film by confocal micron-resolution particle image velocimetry and corresponding numerical simulations were performed using Finite Element Method to model the system. Depthwise change in velocity profiles was observed with electroosmotic flow dominating in the vicinity of the gas-liquid and solid-liquid interfaces while backpressure drives fluid in the opposite direction at the core of the film. It was also found that the direction of the flow at various sections of the films depends on the type of surfactant used, but flow features remained the same. Numerical simulations predicted the flow profiles with reasonable accuracy; however, asymmetry of the actual film geometry caused deviations at the top half of the computational domain. Overall, electroosmotic flow profiles within a free liquid film are similar to that of the closed-end solid microchannel. However, the flow direction and features of the velocity profiles can be changed by selecting various types of surfactants. The free liquid films thickness was selected to match dimensions of foam Plateau border. Hence, these findings will be useful in developing a separation system based on foam electrokinetics.

Application of nanofiltration membranes for removal of surfactants from water solutions

The objective of the study was to compare effectiveness of nanofiltration (NF) process for treatment aqueous solutions containing various types of surfactants (anionic, cationic and non-ionic). The experiments were conducted with the use of Microdyn-Nadir® nanofiltration membranes (NP010 and NP030). The effect of surfactant type, its concentration and membrane cut-off on the process parameters (retention coefficient and permeate flux) was assessed. The experiments showed that separation of anionic and cationic surfactants depended on their concentration in the feed solutions. The retention coefficient of anionic surfactant ranged from 54 to 81% (NP010) and from 64 to 80% (NP030), while rejection of cationic surfactant varied from 48 to 85% (NP010) and from 51 to 88% (NP030). The values of retention coefficient of non-ionic surfactant were in the range of 69-77% and 79-88% for NP010 and NP030, respectively; and to a much lesser extent were depended on its concentration in the feed solutions in comparison with anionic and cationic compounds. Membrane characterized by smaller value of cut-off (NP030) allowed to obtain higher retention coefficients of surfactants. The membrane permeability deterioration was observed with the increase of surfactants concentration in the treated solutions. In all experiments, a sharp decline of the permeate flux was noticed for concentration below the CMC values.

Improving uniformity and nanostructure of solution-processed thin films using ultrasonic substrate vibration post treatment (SVPT)

The main goal of this paper is to introduce a novel mechanical method herein terms as substrate vibration post treatment (SVPT) technique, powered by ultrasonic vibration imposed on the substrate to enhance the characteristics and functionality of spun-on thin films or thin films made by similar casting techniques, such as drop and dip coating. In this technique, the as-casted wet films are placed on a substrate vibrated by an ultrasonic transducer with controlled power and duration to improve the film characteristics, such as uniformity and nanostructure. The performance of this technique is examined on spun-on PEDOT: PSS thin films used in polymer and perovskite solar cells and unprecedented results are presented. We first explore the influence of the vibration duration time on the characteristics of the films made by pristine PEDOT: PSS solution, where it is found that the optimized vibration duration for the pristine PEDOT: PSS film is about 10s, resulting in significant increase in the film electrical conductivity and lowered thickness and roughness. In order to further test the generality and merit of the method, thin films made using PEDOT: PSS solution modified with various types of surfactants and cured by the SVPT are studied. The results show that the application of the SVPT method combined with surfactant modification leads to an impressive twelve-fold increase in the conductivity of the PEDOT: PSS thin films compared with that of the pristine non-vibrated PEDOT: PSS thin films. The sole effect of the SVPT is a four-fold increase in the conductivity of pristine PEDOT: PSS film compared with that of the non-vibrated film. This remarkable enhancement in conductivity is further explained by the AFM phase images of PEDOT: PSS films, showing that the ultrasonic energy could loosen the Coulomb forces between PEDOT and PSS chains, resulting in phase separation and localized reordering of the conducting PEDOT chains leading to an increase in the electrical conductivity of the film. Highly conductive PEDOT: PSS thin film is a viable candidate as electrodes in emerging solution-processed solar cells.

Surfactant-assisted hydrothermal synthesis of Fluoridated Hydroxyapatite nanorods

Fluoridated Hydroxyapatite (FHA) nanorods were synthesized using Apricot Tree Gum (ATG) as a novel surfactant and then compared with Ethylenediaminetetraacetic acid disodium salt dihydrate (EDTA) and Sodium Dodecyl Sulfate (SDS) as conventional surfactant agents under hydrothermal condition (70°C and 1atm). The effects of pH values and various types of surfactants on the formation of the FHA nanorods, crystalline phase, and chemical compositions were investigated using Field Emission Scanning Electron Microscopy (FESEM) equipped by Energy Dispersive X-ray (EDX), X-Ray Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR). The findings indicated application of the presented ATG as surfactant is able to produce the hexagonal nanorods of FHA along their c-axis direction. Moreover, it is illustrated that diameter and length of nanorods which is obtained by ATG surfactant are bigger than EDTA and SDS. In addition, it is demonstrated that pH values can play a major role on formation of hexagonal FHA nanorods. The increase of pH transformed the shape of synthesized FHA from particles to rods. Ultimately, based on the similarity of synthesized FHA nanorods to the shape, structure, and composition of enamel; it is suggested for its potential to be used for dental applications.

Determination of critical micelle concentrations of ionic and nonionic surfactants based on relative viscosity measurements by capillary electrophoresis

The critical micelle concentration (CMC) can be obtained by measuring the distinct physical properties of surfactant molecules in the monomeric and micellar states. In this study, two linear increments of relative viscosity with distinct slopes were obtained when increasing surfactant concentrations from dilute solution to above the CMC, which was then determined by the intersection of the two linear extrapolations. Using a capillary electrophoresis (CE) instrument and Poiseuille’s law, the viscosities of surfactants at a series of concentrations covering the monomeric and micellar regions could be obtained by measuring the hydrodynamic flow rates of the corresponding surfactant solutions. We applied this method to determine the CMC values of various types of surfactants including anionic, cationic, zwitterionic, and nonionic surfactants. The resulting CMC values were all in good agreement with those reported in literature. Using this method, the multiple-stage micellization process of a short-chain surfactant was revealed. We have also demonstrated that the CE-based viscometer was applicable to the study of CMC variation caused by organic or electrolyte additives.

Preparation of hemispherical polystyrene particles utilizing the solvent evaporation method in aqueous dispersed systems

Various nonspherical polystyrene (PS) particles were prepared by slow evaporation of toluene (used common good solvent) from homogeneous PS/hexadecane (HD)/toluene droplets dispersed in surfactant aqueous solutions at room temperature, followed by the rapid removal of HD from PS/HD particles with various phase-separated morphologies. The morphology of PS/HD particles was controlled by tuning the interfacial tension with various types of surfactants. Hemispherical PS particles with flat surfaces were obtained from phase-separated PS/HD/toluene droplets having a Janus structure, when polyoxyethylene nonylphenyl ether with an average ethylene oxide chain length of 30.8 was used as the surfactant.

Electroless deposition of Ni–P–nano-ZrO2 composite coatings in the presence of various types of surfactants

Ni–P–nano-ZrO2 coatings were produced using the electroless deposition technique. To prevent agglomeration of zirconia nanoparticles in the plating bath, various surfactant additives (anionic, cationic, and nonionic) were used. The most stable bath was obtained with the addition of dodecyltrimethylammonium bromide (DTAB). The impact of this surfactant on the deposition rate, coating composition, and topography, as well as ζ potential of particles, was examined. Surface morphology and composition of the Ni–P–nano-ZrO2 composite coatings was analyzed by various techniques including scanning electron microscopy (SEM) equipped with in situ energy-dispersive X-ray (EDX) spectroscopy. Coatings with a clearly greater amount of zirconia (21.88–22.10wt.%) were obtained from baths containing DTAB in concentrations equal to or above its critical micelle concentration (cmc). For these surfactant concentrations, the reduction of Ni and P content was observed.

THE EFFECT OF CHARGE AND CHEMICAL STRUCTURE OF CATIONIC SURFACTANTS ON LASER TONER AGGLOMERATION UNDER ALKALINE PULPING CONDITIONS

Laboratory-scale agglomeration experiments followed by image analysis were used to evaluate the effectiveness of different cationic surfactants on the 1-octadecanol agglomeration of a negatively charged laser toner. Various types of surfactants with different geometric structures were investigated. It was found that this toner became agglomerated under neutral pulping conditions, but it did not agglomerate under alkaline conditions at all. A small amount of the cationic surfactant compensated for the agglomeration disruption caused by the negative surface charge of the toner and made this toner agglomerate very well. These cationic surfactants consist of a chemical structure of C12 to C18 saturated alkyl hydrophobic chains. The positive charge of these surfactants played the major role in alleviating agglomeration disruption. Additionally, an extra phenol group on these surfactants contributed only minor advantages for toner agglomeration in the presence of 1-octadecanol. The best co-agglomeration performance occurred within a very narrow range of similar total positive charge densities based on the total toner weight. It was also found that this positive charge effect could not be applied to the chemical compounds of high molecular weight polymeric materials.

Innovative elastic and flexible conductive PEDOT:PSS composite films prepared by introducing soft latexes

Innovative elastic and flexible conductive composite materials PEDOT:PSS/P(BA–St) and PEDOT:PSS–PBA were prepared by two approaches based on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). In the first part, PEDOT:PSS/P(BA–St) was prepared by blending various soft poly(n-butyl acrylate–styrene) (P(BA–St)) latexes into a PEDOT:PSS conductive dispersion. The PEDOT:PSS conductive dispersion was prepared via oxidative polymerization of EDOT, and the soft P(BA–St) latexes were synthesized by emulsion polymerization using various types of surfactants. In the second part, poly(styrenesulfonate) (PSS) served as a surfactant to synthesize poly(styrenesulfonate)–poly(butyl acrylate) (PSS–PBA) soft latex viaemulsion polymerization. Then, the PEDOT:PSS–PBA dispersion was prepared by using the PSS–PBA soft latex as a polymeric template to polymerize EDOT. The glass transition temperature (Tg) and particle size of P(BA–St) and PSS–PBA were measured. The optoelectronic properties of the conductive PEDOT:PSS/P(BA–St) and PEDOT:PSS–PBA films such as transmittance, surface resistance, and UV-vis absorbance were investigated. According to the elongation measurement, the fabricated PEDOT:PSS/P(BA–St) elastic film containing a P(BA–St) content as high as 83 wt% showed a high value of 97% elongation, while possessing good film conductivity (63 S cm−1) and superior transmittance (93%). On the other hand, the fabricated PEDOT:PSS–PBA flexible film containing 13 wt% PBA showed a low surface resistance increment (R/R0 80%).

Molecular modeling of gel nanoparticles with cyclosporine A for oral drug delivery

Structure and behavior of amphiphilogel nanoparticles as a drug carriers for cyclosporine A (CsA) have been studied by the molecular modeling using empirical force field. Five atomistic models of a gel-based emulsions (GEM) with various gel compositions have been investigated in order to find a system most similar to a sixth atomistic model of self-microemulsifying drug delivery system (SMEDDS) taken as an exemplar of CsA delivery system. Structural parameters and energy characteristics (i.e. non-bond interaction energy between CsA and whole remaining components of a gel nanoparticle, CsA/gel nanoparticle intermolecular non-bond interaction energy, CsA–gel molecule pair interaction energy, volume fraction, concentration profiles and number of pervaded water molecules) of these six models in a waterless form and in a water containing form have been studied in dependence on the composition. The Flory–Huggins theory as implemented in the Accelrys Materials Studio 4.2 modeling environment was used to study the pair interactions of cyclosporine A with various types of surfactants. Structural parameters and energy characteristics of all systems have been compared and one composition was selected as a very promising for further experimental study.

Influence of Surfactants on the Performance of Calcium Phosphate Scale Inhibitors

Abstract The pH-stat technique was used to study the influence of various types of surfactants on the performance of polymers used as inhibitors for preventing the precipitation of calcium phosphate in industrial water systems. Four types of surfactants were evaluated: 1) anionic, 2) non-ionic, 3) amphoteric, and 4) cationic. The polymeric inhibitors studied include homo-, co-, and terpolymers containing different functional groups such as carboxylic acid, sulfonic acid, ester, and amide. It has been found that polymer dosage and polymer architecture play important roles in inhibiting calcium phosphate precipitation. The results on the evaluation of surfactants reveal that all surfactants are ineffective calcium phosphate inhibitors. Comparative inhibition data collected for various calcium phosphate inhibiting polymers in the presence surfactants containing different ionic charges are presented. Results are also discussed on the influence of cationic polymeric flocculant in preventing the precipitation of calcium phosphate by anionic polymeric inhibitors.

Formation of Metallic Nanowires via Electrochemistry in Aqueous Surfactant Media

Atomic contacts between two copper microelectrodes, with conductance close to the conductance quantum (G0), have been generated using simple electrochemical methods in aqueous media containing various types of surfactant. Neutral and cationic surfactant have only a small impact on the conductance with a preponderant value around 1 G0. Furthermore, varying the concentration of the neutral and cationic surfactants above or below the critical micellar concentration (cmc) during the growth process does not lead to any significant variation in the conductance. In contrast, atomic contacts generated in a solution containing an anionic surfactant below the cmc have unusual but reproducible properties. They have <1 G0 conductance and their conductance versus time behavior shows steps at fractional values of the quantum. I/V characterization shows ohmic behavior, supporting the formation of metallic contacts with quantized conductances. The low-conductance value (<1 G0) is attributed to the occurrence of molecular adsorption at the contact. This specific effect seems to be closely related to the cmc. Indeed, when the anionic surfactant concentration is increased above the cmc, the contacts have conductances close to those in neutral or cationic surfactant solution.

Retarding Effect of Contaminants on the Performance of a Two‐Impinging‐Jets Liquid‐Liquid Extraction Contactor

AbstractIn industrial liquid‐liquid extraction processes, the feed is not clean liquid but there are various kinds of contaminants in the feed entering the extractors. In this regard, a two‐impinging‐jets contacting device (TIJCD) was tested through the standard test system recommended by the European Federation of Chemical Engineering (EFCE), namely toluene‐acetone‐water, in the presence and absence of various types of surface‐active agents (SAAs). The influences of anionic, cationic, and nonionic SAAs such as sodium dodecyl sulfate (SDS), dodecyl trimethyl ammonium chloride (DTMAC), and octylphenol decaethylene glycol ether (Triton X‐100), respectively, on the extraction efficiency and overall volumetric mass transfer coefficient of a TIJCD were investigated. It was found that the presence of a little amount of the above named contaminants greatly decreases the performance capability of the TIJCD. On the basis of the experimental results obtained for various types of surfactants, the overall volumetric mass transfer coefficients obtained have satisfactorily been correlated in terms of Weber (We) and Eötvös (Eö) numbers.