A. Mohammed Siddiq

Influence of the Additives on Clouding of Non-Ionic Surfactant Triton X-114 Solutions: Evaluation of Thermodynamics at the CP

In the present work, we report the influence of the additives (e.g., electrolytes, sugars, amino acids, vitamin, etc.) on the cloud point (CP) of non-ionic surfactant Triton X-114 in aqueous solutions. In the absence of any added additives, the CP of Triton X-114 showed a concentration dependent variation (i.e., the CP of pure Triton X-114 is concentration dependent). A decrease/increase in the CP values was observed with the addition of the additives. The results are discussed by taking into consideration the nature of the additives and their micellar growth. The clouding components release their solvated water and separate out from the solution. Therefore, the CP of an amphiphile can be considered as the limit of its solubility. We have evaluated the various thermodynamic parameters of the surfactant (Triton X-114) molecule at the CP in the absence and presence of the additives. Furthermore, for a better understanding of the mechanism of clouding of the surfactant + additive systems in water, dye solubilization studies also performed. GRAPHICAL ABSTRACT

Effect of Dextrose and Temperature on the Micellization of Cationic Gemini Surfactant (16-6-16)

In the present study, we report the micellization behavior of a cationic gemini surfactant, hexanediyl-1,6-bis(dimethylcetylammonium bromide) (16-6-16) at different fixed temperatures and fixed concentration of dextrose in aqueous solutions. The critical micelle concentration (cmc) of 16-6-16, measured by the conductivity and dye solubilization methods. An increasing trend of the cmc values were found with additive (dextrose) concentrations. A similar cmc values increasing trend were found with the temperatures (i.e., increases with increasing temperature). The thermodynamic parameters, viz., standard Gibbs energy (), standard enthalpy (), and standard entropy () of micellization of 16-6-16, are evaluated. The values indicate less stability of the 16-6-16 solution in the presence of dextrose. GRAPHICAL ABSTRACT

Micellization Behavior of a Cationic Gemini Surfactant, Pentanediyl-1,5-Bis(Dimethylcetylammonium Bromide): Effect of Asparagine and Temperature

Herein, we report the effect of amino acid and temperature on the micellization of a cationic gemini surfactant, pentanediyl-1,5-bis(dimethylcetylammonium bromide), 16-5-16. In aqueous solution, the critical micelle concentration (CMC) of 16-5-16 was measured by the conductivity method at different fixed temperatures and a fixed concentration of asparagine. An increasing trend of CMC values was found with both higher (asparagine) concentrations (i.e., increases with increasing asparagine concentration) and higher temperatures (i.e., increases with increasing temperature). The thermodynamics (viz. standard Gibbs energy (#x00029;, standard enthalpy (), and standard entropy ()) of micellization of the gemini surfactant (16-5-16) were evaluated, which indicated less stability of the 16-5-16 solution in the presence of amino acid (asparagine). GRAPHICAL ABSTRACT

The Micellization and Clouding Phenomena of a Nonionic Surfactant, Poly(ethylene glycol) t-octylphenyl ether (Triton X-100): Effect of (Chloride Salt) Electrolytes

Herein, we report the micellization and the clouding of a nonionic surfactant, poly(ethylene glycol) t-octylphenyl ether (Triton X-100), in aqueous solutions in the absence and presence of (chloride salt) electrolytes. In the absence and presence of electrolytes, the critical micelle concentration (CMC) of Triton X-100 was measured by surface tension measurements. Upon increasing the temperature as well as the concentration of electrolytes, the CMCs decreased. The surface properties and the thermodynamic parameters of the micellar systems were evaluated. From these evaluated thermodynamic parameters, it was found that in the presence of an electrolyte, the stability of the micellar system is high. The cloud points (CPs) of Triton X-100 were also measured in the absence and presence of metallic ions of electrolytes. Upon the addition of metallic ions of chloride salts (electrolytes), the decrease in CP values was observed and the order was found to be: K+ > Na+ > Li+ > NH+4. GRAPHICAL ABSTRACT

The Micellization and Clouding of Nonionic Surfactant, Poly(Ethylene Glycol) t-Octylphenyl Ether (Triton X-100): Effect of Halide Ions of (Sodium Salt) Electrolytes

In this investigation, the micellization and the clouding phenomena of a nonionic surfactant, poly(ethylene glycol) t-octylphenyl ether (Triton X-100) in the absence and presence of halide ions (sodium salt) electrolytes has been reported. The critical micelle concentration (CMC) of Triton X-100 (in the absence and presence of electrolytes) was measured by surface tension measurements. A decreasing trend of CMC was found with increasing the temperature as well as the concentration of electrolyte. The effectiveness of the halide ions was found in the order: F− > Cl− > Br− > I−. The surface properties of Triton X-100 were evaluated. The thermodynamic parameters of the micellar systems of Triton X-100 were evaluated and from these thermodynamics data, it was found that in the presence of electrolyte the stability of the micellar system is more. The cloud points (CPs) of Triton X-100 were also measured in the absence and presence of halide ions of electrolytes. With the addition of halide ions of sodium salt (electrolyte), a decrease in CP values was observed and the order was found to be: F− > Cl− > Br− > I−. GRAPHICAL ABSTRACT

Effect of gemini surfactant (16-6-16) on the synthesis of silver nanoparticles: A facile approach for antibacterial application

In this report, we describe the effect of Gemini surfactants1, 6-Bis (N, N-hexadecyldimethylammonium) adipate (16-6-16) on synthesis, stability and antibacterial activity of silver nanoparticles (AgNPs). The stabilizing effect of Gemini surfactant and aggregation behavior of AgNPs was evaluated by plasmonic property and morphology of the AgNPs were characterized by UV-vis spectroscopy, Dynamic Light Scattering (DLS), X-ray diffraction (XRD), High resolution transmission electron microscopy (HRTEM) and Energy dispersive X-ray analysis (EDX) techniques. Interestingly, the formation of quite mono-dispersed spherical particles was found. Apart from the stabilizing role, the Gemini surfactant has promoted the agglomeration of individual AgNPs in small assemblies whose Plasmon band features differed from those of the individual nanoparticles. The antibacterial activity of the synthesized AgNPs on Gram-negative and Gram-positive bacterium viz., E. coli and S. aureus was carried out by plate count, growth kinetics and cell viability assay. Furthermore, the mechanism of antibacterial activity of AgNPs was tested by Zeta potential and DLS analysis, to conclude that surface charge of AgNPs disrupts the cells causing cell death.

Role of Cloud Point of the Capping Agent (Nonionic Surfactant, Triton X-100) on the Synthesis of Silver Nanoparticles

The solution behavior of the nonionic surfactants below and above the cloud point (CP) is quite different. Below CP, a single phase of molecular or micellar solution exists, whereas above the CP, the solution separates into two phases: the first one is denser and smaller phase and contains most of the surfactant and the other one is relatively a voluminous aqueous phase and has surfactant concentration close to the critical micelle concentration (cmc). There are many reports available where nonionic surfactant is used as capping agent. But, to the best of our knowledge, there is no report on the CPs role on the synthesis of nanoparticles (NPs). Therefore, it is very important to understand the role of the CP on the synthesis of NPs. In the present work, we report the role of the clouding of the nonionic surfactant Triton X-100 (using as capping agent) on the synthesis of AgNPs below and above the CP. The morphology of AgNPs was studied by transmission electron microscopy (TEM), dynamic light scattering (DLS), UV–Vis absorption, etc., techniques. Below the CP, spherical polydisperse particles of 12 ± 5 nm mean diameter were found, whereas above the CP, the aggregated particles with higher diameter were found. GRAPHICAL ABSTRACT

Thermodynamic and micellization studies of a cationic gemini surfactant 16-6-16: Influence of ascorbic acid and temperature

Herein, we report the study of the influence of ascorbic acid and temperature on the micellization of a cationic gemini surfactant, hexanediyl-1,6-bis(dimethylcetylammonium bromide), 16-6-16. The critical micelle concentration (CMC) of 16-6-16 was measured by the conductivity method and dye solubilisation technique. A tendency of the CMC values to increase with temperature and upon the adding of ascorbic acid was found. The standard Gibbs energy, standard enthalpy, and standard entropy of micellization of 16-6-16 were evaluated. The results of calculations suggest the decrease of the stability of the 16-6-16 micellar solution in the presence of ascorbic acid.

Micellization and mixed micellization of cationic gemini (dimeric) surfactants and cationic conventional (monomeric) surfactants: Conductometric, dye solubilization, and surface tension studies

ABSTRACT In the present study, we have investigated the self-association, mixed micellization, and thermodynamic studies of a cationic gemini (dimeric) surfactant, hexanediyl-1,6-bis(dimethylcetylammonium bromide (16-6-16)) and a cationic conventional (monomeric) surfactant, cetyltrimethylammonium bromide (CTAB). The critical micelle concentration (CMC) of pure (16-6-16 and CTAB) and mixed (16-6-16+CTAB) surfactants was measured by electrical conductivity, dye solubilization, and surface tension measurements. The surface properties (viz., C20 (the surfactant concentration required to reduce the surface tension by 20 mN/m), ΠCMC (the surface pressure at the CMC), Γmax (maximum surface excess concentration at the air/water interface), Amin (the minimum area per surfactant molecule at the air/water interface), etc.) of micellar (16-6-16 or CTAB) and mixed micellar (16-6-16+CTAB) surfactant systems were evaluated. The thermodynamic parameters of the micellar (16-6-16 and CTAB) and mixed micellar (16-6-16+CTAB) surfactant systems were also evaluated. GRAPHICAL ABSTRACT

Effect of (chloride salt) electrolytes on the mixed micellization of (equimolar) a cationic gemini (dimeric) surfactant and a cationic conventional (monomeric) surfactant

ABSTRACT Herein we report the effect of (chloride salt) electrolytes on the mixed micellization of (equimolar) a cationic gemini (dimeric) surfactant, hexanediyl-1,6-bis(dimethylcetylammonium bromide) (16-6-16), and a cationic conventional (monomeric) surfactant, cetyltrimethylammonium bromide (CTAB) in aqueous solutions. In absence and presence of (chloride salt) MCl (where M˭Li, Na, and K) electrolytes, the critical micelle concentration (CMC) of mixed (16-6-16 + CTAB) surfactants was measured by surface tension measurements. With increasing the concentration of electrolyte, the CMCs were increasing. The surface properties and the thermodynamic parameters of the mixed micellar systems were also evaluated. From these evaluated thermodynamic parameters, it was found that in presence of electrolyte the stability of the mixed micellar system is more. GRAPHICAL ABSTRACT