In the present paper, we aim to investigate the dependence of surface tension on the surface properties and reveal the counter-ion effects on the adsorption of ionic surfactants on the solution surface. The surface tension, surface excess and surface concentration (defined as the amount of surfactant adsorbed in the surface phase divided by the surface area) of two anionic surfactants, namely dodecyl sulfate sodium and dodecyl sulfate caesium, dissolved in non-aqueous polar solvent formamide have been separately measured at 6 °C through independent experiments. Then, the correlation of surface tension with surface concentration and that of surface tension with surface excess is inspected in detail. It was found that there is a linear relationship between the surface tension and the surface concentration for the pure solutions of each surfactant, but their surface tension and surface excess cannot be correlated linearly. It is striking that the same surface tension-surface concentration linearity holds for two different surfactants, although they have apparently distinct counter-ions. Based on this finding, it is derived that the surface tension is decided by surface concentration of the surface active ions. After analyzing the surface structure, it is concluded that the counter-ions affect the surface tension indirectly through modifying the adsorption amount of the surface active ions in the surface layer.
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http://dx.doi.org/10.1039/c4cp03607g | DOI Listing |
AAPS J
January 2025
Institute of Drug Metabolism and Pharmaceutical Analysis, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, 310058, China.
Freeze drying is one of the common methods to extend the long-term stability of biologicals. Biological products in solid form have the advantages of convenient transportation and stable long-term storage. However, long reconstitution time and extensive visible bubbles are frequently generated during the reconstitution process for many freeze-dried protein formulations, which can potentially affect the management efficiency of staff, patient compliance, and product quality.
View Article and Find Full Text PDFSurface active ionic liquids (SAILs), offer potential advantages for pharmaceutical applications. Given the low permeability of gabapentin, an antiepileptic drug, in the gastrointestinal tract as classified by the Biopharmaceutics Classification Systems (BCS), understanding the micellization behavior of SAILs is essential for developing effective drug delivery systems to improve gabapentin bioavailability. This study explores the micellization and thermophysical behavior of SAILs (2-hydroxyethyl)ammonium laurate [2-HEA][Lau], bis(2-hydroxyethyl)ammonium laurate [BHEA][Lau], and tris(2-hydroxyethyl)ammonium laurate [THEA][Lau] in the presence of aqueous gabapentin solution at varied temperatures through COSMO analysis, electrical conductivity and surface tension measurements.
View Article and Find Full Text PDFSci Rep
January 2025
Petrochemicals Department, Egyptian Petroleum Research Institute, 1 Ahmed El Zomor St., Nasr City, Cairo, 11727, Egypt.
Recovering the remaining oil after primary and secondary extraction methods poses a significant challenge. Enhanced oil recovery (EOR) techniques, which involve injecting fluids into reservoirs, aim to increase recovery rates. Ionic liquids, known for their adaptability, are emerging as promising agents in EOR, improving oil displacement by reshaping fluid properties and interacting with reservoir rocks.
View Article and Find Full Text PDFBioinspir Biomim
January 2025
Aerospace Engineering, Chungnam National University, 99 Daehak-ro, Yuseong-gu, Daejeon, 34134, Korea (the Republic of).
This paper describes the tailless control system design of a flapping-wing micro air vehicle in a four-winged configuration, which can provide high control authority to be stable and agile in flight conditions from hovering to maneuvering flights. The tailless control system consists of variable flapping frequency and wing twist modulation. The variable flapping frequency creates rolling moments through differential vertical force from flapping mechanisms that can be independently driven on the left and right sides.
View Article and Find Full Text PDFACS Nano
January 2025
Department of Chemical Engineering, Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada.
A surfactant is an efficient and common additive used to enhance the spreading of droplets on hydrophobic surfaces. However, a high surfactant concentration is required to achieve the desired performance, resulting in environmental pollution and increased costs. Additionally, the pesticide loading capacity of surfactants at low concentrations (below their critical micelle concentrations) is a concern.
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