Micellar aggregation for ionic surfactant in pure solvent and electrolyte solution: Nonextensive thermodynamics approach

Synergistic effects of anionic surfactants on adsorption of norfloxacin by magnetic biochar derived from furfural residue

Norfloxacin (NOR) is a persistent organic pollutant and can be effectively removed from effluent by adsorption of biochar. However, the presence of other emerging contaminants, such as surfactants, will potentially alter adsorption performance of norfloxacin by biochar and the molecular-scale mechanisms of the interaction between surfactants and biochar remain poorly understood. In this study, adsorption of norfloxacin on magnetic biochar prepared with iron-containing furfural residue (FRMB) in the presence or absence of anionic surfactants was investigated. The adsorption of NOR was significantly affected by the initial pH and anionic surfactants-sodium dodecyl sulfate (SDS) and sodium dodecyl benzene sulfonate (SDBS). In the presence of SDS and SDBS, the maximum sorption capacities of NOR were 2.33 and 1.97 times higher than that in the absence of surfactants, reached to 698.6 mg g^-1 and 589.9 mg g^-1, respectively. The optimal pH condition which was 4 indicated that electrostatic adsorption played a decisive role in the adsorption process after introduction of SDS/SDBS. The adsorption data were fitted well by the Elovich model and Freundlich model at the optimal conditions in which both SDS and SDBS were hemimicelle (0.8 mM SDS or 0.4 mM SDBS), indicating surface heterogeneity of FRMB and the adsorption mechanism was related to the assembly of surfactants on biochar. FTIR results showed that FRMB and SDS/SDBS interacted through hydrophobic action, and more complex or aggregates were formed between the NOR and biochar/SDS/SDBS. This work highlights the synergistic enhancement effects of tested surfactants on the removal of NOR by magnetic biochar from aqueous systems.

Bubble Solution Description by Non-Extensive Thermodynamics: Pressure Effect

We showed in this study that nanobubble solutions should not be considered as the simple juxtaposition of autonomous phases (a solution and bubbles) but as particular entities, that is, "supersaturated solutions" where gas is simultaneously in two forms in permanent exchange. Gibbs' extensive thermodynamics cannot claim to describe legitimately their behavior. In this work, we showed how the use of the non-extensive thermodynamics allows describing the physicochemical properties of such media, some of which are counter-intuitive. Thus, an increase in pressure can result in an increase in the bubble size, contrary to what is provided by Boyle-Mariotte's law. The theoretical relationships proposed in this work constitute another approach to bubble solutions, which considers the non-autonomous nature of the components of supersaturated gas solutions and their "non-extensive" nature.

Light responsive thin films of micelles of PS-b-PVP complexed with diazophenol chromophore

We have incorporated push-pull azobenzene units into diblock-copolymer micelles by supramolecular assembly. Specifically, we encapsulated a phenol-functionalized chromophore, DO13, within PS-b-P4VP micelles in toluene by means of H-bond interactions developed between DO13 molecules and pyridine groups of P4VP block. The solutions were spin-coated onto glass substrates resulting in multi- or mono-layered thin films of micelles with P4VP(DO13) core and PS corona. We show that the use of DO13 as a building block of micellar aggregates allowed us to manipulate the developed nanostructures. Spherical to cylindrical micellar transition was found when we increased the degree of chromophore complexation. Also, it was found that the polymer concentration in the solution plays an important role in determining the micellar nanostructures. The chain extension and change in composition of the P4VP core in the presence of the chromophore may be responsible for the structural changes observed in the micelles. The optical properties of the thin films have been investigated focusing on the effect of the micellar morphology over the photoinduced birefringence. The optical anisotropy (Δn) increased with respect to the analogous homogeneous system P4VP(DO13), indicating that the protective micelle environment can enhance the optical properties of the embedded chromophores significantly. Furthermore, we show very interesting new results in which we have related changes in optical properties to the film morphology (spheres to cylinders). This can be exploited for producing optical devices having improved optoelectronic properties and stability.

Solubility of gas in confined systems. Nonextensive thermodynamics approach

The use of the concepts of the nonextensive thermodynamics allows reconsidering the equilibrium of bubble solubilization and more commonly of gaseous aggregates in supersaturated solutions of gas. The introduced relations are general and include as particular cases the equations usually used to describe these phenomena. These equations are discussed. Especially, we specified the domain of application of Kelvin's relation which was illustrated by the solubility of gases in fogs and clouds. Various possibilities of thoughts on the behavior of the gaseous aggregates and nano-systems are proposed. Thus, the introduced relations permit to consider the presence of gaseous aggregates in equilibrium with the solution even for under-saturated solution. Nonextensive thermodynamics admits the notion of negative pressure at the inner of confined phases (solid or liquid).

Development of various PS-b-P4VP micellar morphologies: fabrication of inorganic nanostructures from micellar templates

We demonstrate a simple route for preparing various micellar nanostructures, like spheres, cylinders, and vesicles, by spin-coating or drop-casting process of polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) copolymer solutions in pure tetrahydrofuran (THF), THF/water, and THF/ethanol mixture. Upon drying, a solvent selectivity plays an important role in determining micellar nanostructures in thin films. In solution, micellar sizes and shapes of these PS-b-P4VP copolymers were investigated by dynamic and static light scattering. Immediately after spin-coating the polymer solutions, surface and internal morphologies of the films were observed by atomic force microscopy and transmission electron microscopy. As the polymer concentration in THF or the amounts of water or ethanol added in THF solutions was varied, a remarkable difference in the PS-b-P4VP micellar morphologies was observed, from which spherical or cylindrical or vesicular micelles were developed. These micellar films were used as scaffolds or templates for fabricating metal nanodots or nanowires arrays.