Incorporation of poorly soluble drug Cefixime inside the micellar core of conventional and gemini surfactants

This work reports the physicochemical behavior of antibiotic drug, cefixime (CEF) in presence of cetyl trimethyl ammonium bromide (CTAB), dodecyl trimethyl ammonium bromide (DTAB), dodecyl ethyl dimethyl ammonium bromide, (DDAB),...

Gemini-Mediated Self-Disinfecting Surfaces to Address Contact Transmission of Infectious Diseases

According to both the Center for Disease Control (CDC) and the World Health Organization (WHO), contact-transmission (contact between host tissues and a contaminated surface) is the primary transmission route of infectious diseases worldwide. Usually this is mitigated by adherence to a schedule of repeated regular sanitization, yet this approach is inherently limited by sanitization frequency; conventional disinfectants/methods are only germicidal during the period of application, and surfaces are easily re-contaminated in the interim between cleanings. One solution to this problem is to use agents/coatings that impart self-disinfecting properties onto the existing surfaces such that they display sustained virucidal/antimicrobial properties against pathogens that settle upon them. Quaternary-ammonium organosilicon compounds are ideal candidates to achieve this; cationic surfactants are safe and well-established surface disinfectants while organosilanes are used broadly to form durable coatings with altered surface properties on many different materials. Despite their potential to circumvent disadvantages of traditional disinfection methods, extant commercially available quaternary-ammonium silanes do not display comparable efficacy to standard surface disinfectants, nor have their respective coatings been demonstrated to meet the Environmental Protection Agency’s guidelines for residual/extended efficacy. Inspired by powerful surface activity of double-headed “gemini” surfactants, here we present gemini-diquaternary (GQ) silanes with robust residual germicidal efficacy on various surfaces by incorporating a second cationic “head” to the structure of an conventional mono-quaternary-ammonium silane. Aqueous solutions of GQs were tested in suspension- and surface-antimicrobial assays against an array of pathogens, including Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). GQ performance was benchmarked against the common disinfectants, ethanol, hydrogen peroxide and hypochlorite, as well as against a common antimicrobial mono-quaternary (MQ) silane. Solutions of GQ silanes were efficacious when used for immediate disinfection, showing comparable activity to common disinfectants (>106 fold reduction in 15 seconds). Additionally GQ solutions were demonstrated to impart durable self-disinfecting properties to a variety of porous and nonporous surfaces, efficacious after repeated cycles of abrasion and repeated contaminations, and with superior coating ability and activity (>108 higher activity) than that of the popular MQ silane. GQ solutions as surface treatments show great promise to overcome the limitations of traditional disinfectants in preventing the spread of infectious diseases.

Study on Adsorption Characteristics of Sulfonate Gemini Surfactant on Lignite Surface

In order to explore the adsorption characteristics of sulfonate gemini surfactants on the surface of lignite, the molecular dynamics simulation method was used, and A kind of sulfonic acid bis sodium salt (S2) and the sodium dodecyl sulfate (SDS) were selected. A binary model of surfactant/lignite adsorption system and a ternary model of water/surfactant/lignite system were constructed, and a series of properties such as adsorption configuration, interaction energy, order parameters, relative concentration distribution, number of hydrogen bonds, etc., were analyzed. The results showed that the adsorption strength of S2 on the surface of lignite was higher than that of SDS. The results indicated that the large-angle molecular chain in S2 tended to become smaller, the small-angle molecular chain tended to become larger, and the angle between the molecular chains and the Z axis tended to be concentrated, making the formed network structure denser during the adsorption process. The number of hydrogen bonds in the water-coal system was 42, and the number of hydrogen bonds in the system after S2 adsorption was 15, which was much lower than the 23 hydrogen bonds in the system after SDS adsorption, and S2 could better adsorb and wrap the oxygen-containing groups on the surface of the lignite. The comparative study of the adsorption characteristics of the two surfactants on the surface of lignite can help us better understand the influence of the surfactant structure on the adsorption strength. The research results have important theoretical and practical significance for developing new surfactants, and enriching and developing the basic theory of coal wettability.

Influence of the length of the spacer group on the performance of the sulfate-based Gemini surfactants

PurposeA series of sulfate-based Gemini anionic surfactants were synthesized via etherification, ring opening and sulfation reactions using epichlorohydrin, fatty alcohol, ethylene glycol and chlorosulfonic acid as the main raw materials. Orthogonal experiments for 1,8-bisalkoxymethylene-3,6-dioxin-1,8-octane disulfate were performed on the sulfation reaction to determine the optimal reaction conditions.Design/methodology/approachA series of sulfate-based Gemini anionic surfactants were synthesized via etherification, ring opening and sulfation reactions using epichlorohydrin, fatty alcohol, ethylene glycol and chlorosulfonic acid as the main raw materials. Orthogonal experiments for 1,8-bisalkoxymethylene-3,6-dioxin-1,8-octane disulfate were performed on the sulfation reaction to determine the optimal reaction conditions. The structures of the intermediate and final products were characterized by FT-IR (Fourier transform infrared spectroscopy analysis), 1H-NMR (proton nuclear magnetic resonance spectroscopy) methods. The thermal performance of surfactants was analyzed using thermogravimetric analysis (TGA). The thermogravimetric results showed that the sulfate-based Gemini surfactants had good heat resistance (the thermal decomposition temperature of which was in the range of 140∼170?). The Krafft point, surface tension, foaming, Hydrophile–Lipophile Balance Number (HLB), emulsifying, wetting, and lime-soap dispersing performance were measured by visual observation, hanging drop method, aqueous surfactant solution method and Borghetti–Bergman method, respectively. The results have shown that all the sulfate-based Gemini surfactants had good water solubility and lime-soap dispersing ability. When spacer group was -(CH2)2-, with the increase of the carbon chain length from C12 to C14, the micellar concentration critical micelle concentration and surface tension (CMC) gradually increased from 8.25 × 10–4 mol/L to 8.75 × 10–4 mol/L and 27.5 mN/m to 30.9 mN/m, respectively. Also, the sulfate-based Gemini surfactants with the different length of the spacer group had a different effect on their performance on foaming properties and foam properties, HLB and emulsifying ability and wetting ability. FindingsIn view of the important role of the spacer group and the general use of anionic surfactants in oil fields, this article considers the preparation of a series of sulfate-based Gemini surfactants by changing the spacer group and the chain length of the hydrophobic group and evaluating their surface activity, and finally its Kraffi, on the foam properties, HLB value, emulsifying performance, lime soap dispersing ability etc.Originality/valueSulfate-based Gemini surfactants have broad application prospects in the fields of oil and gas exploitation, environmental protection, chemistry and daily chemical industry and so on.

Study on Adsorption Behavior of a New Type Gemini Surfactant Onto Quartz Surface by a Molecular Dynamics Method

The adsorption mechanism of the branched quaternary ammonium salt Gemini surfactant (Gemini C3) at the water-surfactant-quartz interfaces for both neutral and negatively charged quartz surfaces was studied by a molecular dynamics (MD) method. Initial and final configurations, distributions of the surfactant and its interaction with surfaces, the radial distribution function (RDF) of water molecules, and the mean square displacement (MSD) of the surfactant in bulk phase have been elucidated at the molecular level. The results showed that the adsorption of Gemini surfactants onto the hydrophilic quartz surface was driven by electrostatic interaction, which increased the hydrophobicity of the solid surface when the surfactant concentration was lower than critical micelle concentration (CMC). However, the contact angle only slightly increased since the surface tension decreased simultaneously with growing concentration. Monolayers were formed during the adsorption process of Gemini C3 molecules on the quartz surface rather than a double layer when the concentration reached the CMC, indicating a gradual transformation of an extended monolayer adsorption configuration into a more compact one. The solid-liquid interfacial tension increased with the surfactant concentration and led to a significant increase of the contact angle. The simulation results were consistent with the experiments, which further revealed the microscopic adsorption mechanism of the Gemini C3 surfactant onto the quartz surface, and provided theoretical guidance for controlling the wetting properties and surface modification of the rock.