Carbon Chain Length Of Surfactants Research Articles

Enhanced Dissolution of Amphotericin B through Development of Amorphous Solid Dispersions Containing Polymer and Surfactants

Amphotericin B (AmB) is the gold standard for antifungal therapy; however, its poor solubility limits its administration via intravenous infusion. A promising formulation strategy to achieve an oral formulation is the development of amorphous solid dispersions (ASDs) via spray-drying. Inclusion of surfactants into ASDs is a newer concept, yet it offers increased dissolution opportunities when combined with a polymer (HPMCAS 912). We developed both binary ASDs (AmB:HPMCAS 912 or AmB:surfactant) and ternary ASDs (AmB:HPMCAS 912:surfactant) using a variety of surfactants to determine the optimal surfactant carbon chain length and functional group for achieving maximal AmB concentration during in vitro dissolution. The ternary ASDs containing surfactants with a carbon chain length of 14 ± 2 carbons and a sulfate functional group increased the dissolution of AmB by 90-fold compared to crystalline AmB. These same surfactants, when added to a binary ASD, however, were only able to achieve up to a 40-fold increase, alluding to a potential interaction occurring between excipients or excipient and drug. This potential interaction was supported by dynamic light scattering data, in which the ternary formulation produced a single peak at 895.2 dnm. The absence of more than one peak insinuates that all three components are interacting in some way to form a single structure, which may be preventing AmB self-aggregation, thus improving the dissolution concentration of AmB.

Experimental investigation of zwitterionic surfactant-based silica nanofluid spontaneous imbibition at high salinity and elevated temperature conditions

High-efficiency development of low permeability reservoirs is significant to maintaining a balance between energy supply and social needs. Surfactant-based nanofluids with an excellent interfacial activity that can penetrate the small throats and narrow pores are considered promising EOR agents. However, the applications of nanofluids in harsh reservoir conditions remain to be challenging due to high stability requirements. In this work, a highly stable active nanofluid that could withstand high salinity (API brine) and elevated temperatures was prepared by mixing zwitterionic hydroxypropyl sulfobetaine surfactant with low-molecular-weight ligand modified silica nanoparticles. At a surfactant/nanoparticle concentration ratio of 0.5, the spontaneous imbibition recovery factor of dodecyl hydroxypropyl sulfobetaine-based nanofluid was 2.61 times higher than API brine, 1.29 times higher than API brine-based nanofluid and 0.37 times higher than surfactant alone. Meanwhile, the impacts of surfactant carbon chain length, permeability as well as hydrochloric acid were included. Experimental results indicated that surfactants with longer carbon chain length would destabilize the nanofluids due to increasing hydrophobic interactions, and nanoparticle aggregation/precipitation would impose adverse impacts on spontaneous imbibition because of pore/throat plugging. Though increasing permeability could partially ease the negative plugging effects, the potential risks should never be overlooked. Properly using hydrochloric acid could greatly enhance the stability of nanoparticles by forming an “H+” protection layer and extend their applications to over 80 °C, but the presence of acid also disturbed the adsorption behaviors of surfactants, therefore, different phenomena were noticed when the nanofluid formula changed. A good spontaneous imbibition system should possess both IFT reduction and wettability alteration capabilities, and nanoparticles’ ability to adsorb and disperse polar compounds such as asphaltene should be fully fulfilled. This study provides new guidance for nanofluid formulation to support the effective development of low-permeability oil reservoirs.

Optimization of Piezoresistive Strain Sensors Based on Gold Nanoparticle Deposits on PDMS Substrates for Highly Sensitive Human Pulse Sensing

In this study, highly-sensitive piezoresistive strain sensors based on gold nanoparticle thin films deposited on a stretchable PDMS substrate by centrifugation were developed to measure arterial pulse waveform. By controlling carbon chain length of surfactants, pH value and particle density of the colloidal solutions, the gauge factors of nanoparticle thin film sensors can be optimized up to 677 in tensile mode and 338 in compressive mode, and the pressure sensitivity up to 350. Low pH and thin nanoparticle films produce positive influences to superior gauge factors. It has been demonstrated that nanoparticle thin film sensors on PDMS substrates were successfully applied to sense arterial pulses in different body positions, including wrist, elbow crease, neck, and chest.

Molecular Insight into Dye-Surfactant Interaction at Premicellar Concentrations: A Combined Two-Photon Absorption and Molecular Dynamics Simulation Study.

Both electrostatic and hydrophobic interactions play pivotal roles in ligand-surfactant binding interaction, especially for ionic surfactants. While much studies have been reported in the micellar region, less attention has been paid on such interactions at a low (premicellar) surfactant concentration. We here study the interaction between the cationic dye rhodamine 6G (R6G) with surfactants of different charge types: anionic SDS, cationic CTAB, and nonionic Tx 100 using absorption and emission spectroscopy. We identify that R6G forms dimeric aggregates at a premicellar concentration of SDS. Formation of aggregates is also confirmed from classical simulation measurements. CTAB and Tx 100 do not form any such aggregate, presumably owing to unfavorable electrostatic interactions. For a molecular-level understanding, we perform two-photon absorption (TPA) spectroscopy for the same systems. TPA allows us to calculate the two-photon absorption cross section and subsequently the change in the dipole moment (Δμ) between ground and excited states of the dye. We calculate the Δμ and observe that it passes through a maximum at a surfactant concentration half of the critical micelle concentration of SDS. This observation imparts support to earlier quantum mechanical calculation, which infers deviation from the parallel orientation of the dye during surfactant-induced aggregation. We extended our measurements and varied the carbon chain length of the anionic surfactant, and we found that all of them exhibit a maximum in Δμ, while their relative magnitude is dependent on the surfactant carbon chain length.

Synthesis of borohydride nanoparticles at room temperature by precipitation

Borohydride (LiBH4, NaBH4 and KBH4) nanoparticles were successfully synthesized by a modified ternary anti-precipitation method. A co-solvent was introduced to facilitate the formation of a microemulsion and modify the metastable zone to favour the precipitation of borohydride particles. In this process, the stabilising surfactant's carbon chain length was found to provide an additional mean to further tune particle size due to the resulting steric hindrance. The method reported here finally provides an effective and simple mean to prepare nanosized borohydride particles for hydrogen storage purposes, while minimising the amount of stabilising surfactant that can contaminate the hydrogen release.

Preparation of Physical-modified Mesoporous Silica

Based on the concept of molecular design, mesoporous silica materials with different physical structure and morphology were prepared by adjusting the molecular chain length of surfactants and the mass ratio of anion-cationic surfactants. The composition and morphology of the prepared silica materials were characterized by FTIR, SEM, N2 adsorption and desorption. By adjusting the carbon chain length of surfactants and the mass ratio of anion-cationic surfactants, the preparation of mesoporous silica was carried out, and the effects of mesoporous silica on the internal structure of mesoporous silica were analyzed.

Effects of surfactant and particle size on the microstructure and strength of Si3N4 foams with high porosity

AbstractThe highly porous Si3N4 ceramic foams were prepared by direct foaming with mixed surfactants. The surface tension and viscosity of slurries were tailored by different carbon chain length of surfactants and different mean Si3N4 particle size to achieve the pore size controlling. The nearly linear relationship between the pore size and the ratio of surface tension to viscosity was observed, which indicates that the pore size could be precisely tailored by the slurry properties. Si3N4 ceramic foams with porosity of nearly 94%, mean pore size of 110–230 µm, and compressive strength of 1.24–3.51 MPa were obtained.

Removal of BTEX and hexane by organo-zeolites: The influence of surfactant carbon chain length on the sorption process

Removal of BTEX and hexane by organo-zeolites: The influence of surfactant carbon chain length on the sorption process

New insights into alkylammonium-functionalized clinoptilolite and Na-P1 zeolite: Structural and textural features

The area of zeolites’ application could be expanded by utilizing their surfaces. Zeolites are frequently modified to increase their hydrophobicity and to generate the negative charge of the surface. The main objective of the study was to investigate and compare the features of natural clinoptilolite and synthetic zeolite Na-P1 modified by selected surfactants involving quaternary ammonium salts. The FTIR study indicates that with increasing carbon chain length in the surfactant attached to the zeolites surface the molecules adopt a more disordered structure. FTIR was also used to determine the efficiency of surface modification. Thermal analysis revealed that the presence of surfactant results in additional exothermic effects associated with the breaking of electrostatic bonds between zeolites and surfactants. The mass losses are in line with ECEC and CHN data. The textural study indicates that the synthetic zeolite Na-P1 has better sorption properties than natural clinoptilolite. The modification process always reduces the SBET and porosity of the material. With an increasing carbon chain length of surfactants all the texture parameters decrease.

Role of the charge, carbon chain length, and content of surfactant on the skin penetration of meloxicam-loaded liposomes.

The objective of this study was to investigate the influence of surfactant charge, surfactant carbon chain length, and surfactant content on the physicochemical characteristics (ie, vesicle size, zeta potential, elasticity, and entrapment efficiency), morphology, stability, and in vitro skin permeability of meloxicam (MX)-loaded liposome. Moreover, the mechanism for the liposome-enhanced skin permeation of MX was determined by Fourier transform infrared spectroscopy and differential scanning calorimetry. The model formulation used in this study was obtained using a response surface method incorporating multivariate spline interpolation (RSM-S). Liposome formulations with varying surfactant charge (anionic, neutral, and cationic), surfactant carbon chain length (C4, C12, and C16), and surfactant content (10%, 20%, and 29%) were prepared. The formulation comprising 29% cationic surfactant with a C16 chain length was found to be the optimal liposome for the transdermal delivery of MX. The skin permeation flux of the optimal formulation was 2.69-fold higher than that of a conventional liposome formulation. Our study revealed that surfactants affected the physicochemical characteristics, stability, and skin permeability of MX-loaded liposomes. These findings provide important fundamental information for the development of liposomes as transdermal drug delivery systems.

Controlled synthesis of ZnO nanostructures with different morphologies in microemulsions

AbstractZnO nanostructures with different morphologies were prepared in microemulsions with ZnSO4 and ammonia as raw materials. The effects of microemulsion types, concentration of reactants, W values, co‐surfactants, surfactants, oil phases and calcination temperatures were systematically studied. The products were characterized by X‐ray diffraction (XRD), differential scanning calorimetry and thermogravimetry (DSC‐TG), transmission electron microscopy (TEM), high‐resolution TEM (HRTEM), and photoluminescence (PL) spectrum. Results show that ZnO nanoparticles were obtained in water‐in‐oil microemulsions while ZnO nanorods are gained in bicontinuous microemulsions. Water‐in‐oil microemulsions and long carbon chains of surfactants can prevent the preferential growth of ZnO. The particle size of the products increased with the increase of W values, calcination temperatures and the concentration of reactants but decreased with the increase of the carbon chain length of surfactants, co‐surfactants and oil phases. PL spectrums show that the UV emission peak weakened and visible emission peak increased with the decrease of particle size. Meanwhile, the PL spectrums have a little red‐shifted.

Influences of Carbon-Chain Length of Surfactants on Mesoporous Manganese Oxides

Three kinds of mesoporous manganese oxides were prepared successfully via a simple hydrothermal method, using dodecyltrimethylammonium bromide (DTAB), cetyltrimethyl- ammonium bromide(CTAB) and octadecyltrimethyl ammonium bromide(OTAB) as structure directing agents, respectively. The as-synthesized samples were characterized by X-ray diffraction(XRD) and Brunauer -Emmett-Teller(BET)．The experimental results show that the carbon-chain length of surfactants have influences on not only crystal structure and metal valence, but also specific surface area and pore size of the as-prepared materials. The specific surface areas are 60 m2•g-1, 25 m2•g-1, 7 m2•g-1，and the pore sizes are 4 nm，7 nm, 13 nm for the three kinds of mesoporous materials prepared using structure directing agents DTAB, CTAB, and OTAB, respectively.

Interaction between crystal violet and anionic surfactants at silica/water interface using evanescent wave-cavity ring-down absorption spectroscopy

Evanescent wave-cavity ring-down spectroscopy (EW-CRDS) is employed to characterize micellization of anionic surfactants and the related capability of removing cationic substance off the silica surface. Crystal violet (CV+) cationic dye is used as a molecular probe to effectively determine critical hemimicelle concentration (HMC) of surfactants on the surface. The HMC results are 1×10−2, 4×10−3, 8×10−4, and 2.5×10−4mol/L for sodium sulfate salts with a carbon-chain length of C-10, C-12, C-14, and C-16, respectively. A stronger hydrophobic interaction results in a less concentration required to undergo micellization. The HMC values on the surface are about half of those in solution. When NaCl solution is added, the electrolyte helps reduce the electrostatic repulsion between the anionic sulfate heads to facilitate the surfactant aggregation, and thus, the subsequent HMC is reduced. Furthermore, the probable phase change for dye-surfactant interactions on the surface at the concentration below HMC is observed, and the desorption rates of CV+ are measured as a function of concentration and carbon-chain length of surfactants above HMC. Given each surfactant concentration at its respective HMC, the corresponding desorption rates are along the order of C-12<C-14<C-16<-C-10. The trend may be realized by two competing factors of hemimicelle size and number density. The consequences help with understanding how to apply surfactant in the chromatographic separation.

Effects of Surfactant Carbon-Chain Length on the Phase Behaviors of ATPS

The phase behaviors and properties of alkyl trimethyl ammonium bromide with different carbon-chain length/sodium dodecyl sulfate (SDS)/NaBr/H2O systems at the total surfactant concentration of 0.1 mol · L−1 at 333 K were investigated. The experimental results indicate that the phase behaviors of different systems have similar distributing rules. The carbon-chain length of cationic surfactant can influence the position of aqueous two-phase system region, especially for aqueous two-phase system with cationic surfactant in excess, but only have slight effect on aqueous two-phase system with anionic surfactant in excess. The ATPSc region narrows as the length of carbon-chain increases, while the trend for ATPSa is opposite. Increasing the carbon-chain length to some extent will be favorable to shortening the formation time of ATPS greatly. The investigations illustrate that the above rules result from a hydrophobic interaction relationship between surfactant molecules.

Impact of Pre-equilibration on the Assessment Methodology of Interfacial Tension Measured between Aqueous and Heavy Oil Phases

Equilibrium interfacial tension (IFT) between toluene-diluted bitumen and a series of alkyltrimethylammonium bromide surfactant solutions was measured at various temperatures as a function of the carbon chain length of surfactants. A mixing and separating protocol to pre-equilibrate the aqueous and organic phases was introduced prior to the measurements. The influence of the equilibrated phase densities on the IFT values obtained by the pendant drop method is discussed. A possible systematic error in the assessment of the IFT values with the pendant drop and spinning drop methodologies was pointed out. In general, bitumen–aqueous phase IFTs increase with an increase in the temperature and decrease with an increase in the carbon chain length of the surfactants. During the equilibration process of the bitumen and aqueous phases, the phase densities change significantly, which has implications on the gravity drainage process.

The effect of surface chemistry and nanoclay loading on the microcellular structure of porous poly( d, l lactic acid) nanocomposites

Three series of polymer nanocomposites, based on poly( d, l lactic acid) (PDLLA) and organically modified montmorillonite, were prepared by the melt and the solution intercalation technique. The first series was prepared by extrusion using different clay loadings. The second series of nanohybrids was obtained using montmorillonite modified with different types of alkylammonium surfactants in terms of carbon-chain lengths (i.e., 4, 8, 12, 16 and 18). In the third series of nanocomposites, the organic cation concentration of the surfactant was varying. Microcellular porous materials were, afterwards, fabricated from these three series of nanocomposites. The porous structures of pure and nanocomposite PDLLA were prepared by isothermal pressure quench using supercritical CO 2 as foaming agent. The morphology of the produced porous materials was investigated by scanning electron microscopy (SEM). Image processing of the samples revealed that the final cellular structure is strongly related to clay loading and, both, the type and the organic cation concentration of the alkylammonium used for the modification of the clay. The results suggest that the size of the pores decreases and the cell density and bulk foam density increase with the increase of clay loading or the surfactant's carbon chain length or the cation concentration in clay. Clay dispersion seems to be enhanced by the supercritical treatment upon foaming.

Preparation of nanosize cerium oxide particles in W/O microemulsions

Cerium dioxide nanoparticles were synthesized in a toluene/CTABr/Ce(NO 3) 3/pentanol system using the microemulsion technique and ammonium hydroxide as hydrolyzing agent. Particle size was controlled by varying the molar ratio W = [water]/[surfactant], precursor concentration and surfactant carbon chain length. The molar ratio W was varied between 4 and 20, because model calculations had shown this range to be ideal for the synthesis of particles below 10 nm in size. Based on TEM measurements, particle size was in the range of 2.69–4.06 nm. Precursor ion concentration was varied in the range of 2.2–6.6 wt% (46.0–138 mM). The size of the droplets formed in the microemulsion was determined by dynamic light scattering. Structural studies on CeO 2 and particle size determination were carried out by XRD. Thermal analysis of the samples prepared in W/O microemulsions is also presented. The specific surface area of the samples was 53.53–128.65 m 2/g and their average pore size as determined by pore size distribution measurements was 1.73–4.91 nm.

Effect of surfactant carbon chain length on hydrate formation kinetics

An experimental study was conducted on the effect of the addition of surfactants on hydrate formation kinetics. A series of surfactants with sodium sulfonic acid groups in common but with different carbon chain lengths (C4, C12, and C18) were tested, and the effects of the carbon chain length and concentration were systematically investigated. Hydrate formation rates were measured by a batch-type method with a high-pressure vessel made of stainless steel, with 100 mL inner volume, and the hydrate formation rate determined by the rate of pressure decrease caused by hydrate formation. The hydrate formation rate of xenon increased with the addition of the surfactants in the lower concentration range, and the acceleration showed a maximum at a certain concentration, but decreased with further concentration increases. For a given weight concentration, the surfactant with the shortest chain length (C4, butanesulfonic acid sodium salt) showed the highest acceleration (about 2.5 times larger than for pure water). The acceleration from the C4 surfactant was greater for methane hydrate formation, where the hydrate formation rate was about 5 times greater than that without surfactant. Energy saving potential was estimated when the C4 surfactant was applied to a natural gas transportation scenario in the form of hydrates; it was estimated that power consumption can be reduced by about 40% with the use of the C4 surfactant in the hydrate formation process.

Semi-empirical quantum chemical study of the interactions between lysine, arginine and histidine with a homologue set of n-alkyl sulfates in the gas phase and aqueous solution

Semi-empirical quantum chemical calculations were used to study the interaction of positively charged amino acids (lysine, arginine or histidine) with a homologue set of n-alkyl sulfate derivatives in the gas and aqueous phase. Full geometry optimization of the amino acids and surfactants were achieved by means of AM1 and PM3 calculation methods in which the latter gave more reasonable results. Amino acids were considered as zwitterionic and coated forms. In the latter forms, the amine and carboxyl groups of amino acids were protected by the formyl and amine groups, respectively. Enthalpy differences of the reactions were calculated and compared with the experimental results obtained by other workers. Gas phase calculations showed that by increasing the number of carbon chain length of surfactants, Δ H of the reaction will be more endothermic, while the experimental data showed a reverse behavior. However, the trend of Δ H of reaction vs. number of carbon atoms in the surfactants tail, obtained by aqueous phase calculations, was in direct agreement with the experimental results.

Quinclorac Efficacy as Affected by Adjuvants and Spray Carrier Water1

Laboratory and greenhouse experiments were conducted to determine quinclorac efficacy as influenced by surfactants, methylated seed oil (MSO), basic pH compounds, and salts in the spray carrier water. Quinclorac efficacy for green foxtail control generally increased with an increase in linear alcohol ethoxylate (LAE) surfactant carbon-chain length and percentage of ethoxylation. With LAE surfactants, quinclorac phytotoxicity to green foxtail was nearly doubled (average from 44 to 81%) when triethanolamine (TEA) was included in the spray mixture. Combination of LAE surfactants with TEA also enhanced quinclorac absorption. Enhancement of quinclorac absorption and phytotoxicity by LAE surfactants and TEA was related to spray deposits that had close contact with the cuticle and without apparent quinclorac crystals. Sodium and calcium ions strongly antagonized quinclorac efficacy when applied with a block copolymer surfactant or MSO. Ammonium sulfate or ammonium nitrate adjuvants were more effective than urea–...