Classical Density Functional Theory for Fluids Adsorption in MOFs

The designing of metal organic frameworks (MOFs) requires an efficient method to predict its adsorption properties. The conventional method to do this is molecular simulation, which is time consuming. In contrast, classical density functional theory (CDFT) is a much more efficient tool. Recently, CDFT has been successfully applied to MOF adsorptions. In this chapter, we will introduce the development and the different versions of CDFT and show how to apply CDFT to predict fluid adsorption in MOFs. We have reviewed the recent applications of CDFT in MOF adsorption and mainly focused on material screening. According to the recent developments, it seems CDFT is an efficient and robust tool for material screening; how to deal with more complicated fluids is the challenge of current CDFT

Classical Density Functional Theory Insights for Supercapacitors

The most urgent issue for supercapacitor is to improve their energy density so that they can better compete with batteries. To design materials and interfaces for supercapacitor with higher energy density requires a deeper understanding of the factors and contributions affecting the total capacitance. In our recent works, the classical density functional theory (CDFT) was developed and applied to study the electrode/electrolyte interface behaviors, to understand capacitive energy storage. For porous electrode materials, we studied the pore size effect, curvature effect, and the surface modification of porous materials on the capacitance. Thought CDFT, we have found that the curvature effects on convex and concave EDLs are drastically different and that materials with extensive convex surfaces will lead to maximized capacitance; CDFT also predicts oscillatory variation of capacitance with pore size, but the oscillatory behavior is magnified as the curvature increases; an increase in the ionophobicity of the nanopores leads to a higher capacity for energy storage, and a pore-like impurity can enter the pore, makes the pore ionophobic and storage more energy. We also find the mixture effect, which makes more counterions pack on and more co-ions leave from the electrode surface, leads to an increase of the counterion density within the EDL and thus a larger capacitance

Optimization of pre-concentration, entrainer recycle and pressure selection for the extractive distillation of acetonitrile-water with ethylene glycol

We optimize the extractive distillation process for separating the acetonitrile – water azeotropic mixture with ethylene glycol by using a multi-objective genetic algorithm for minimizing under purity constraints the total cost, the energy consumption and the separation efficiency. For the first time we have shown the interest of five aspects by considering them simultaneously 1) the pre-concentration column has been included and 2) there is no need to set a distillate composition constraint (like being at the azeotropic composition) in the pre-concentration column. 3) The operating pressure should be lower than 1 atm because it enhances the relative volatility for 1.0-1a class system. 4) A closed loop optimization must be run, to handle the effect of impurity in the entrainer recycle since too much impurity limits the main product recovery and purity from the extractive column. 5) All three columns process must be optimized together rather than sequentially and with multiple objectives. The studied system belongs to class 1.0-1a and the impurity of the recycled entrainer has strong effect on the purity of acetonitrile product. Overall, 17 variables are optimized; column trays, all feed locations, refluxes, entrainer flow rate and all distillate products; under purity constraints for the acetonitrile and water product and for the entrainer recycle impurity. Among nearly 400 designs satisfying the purity specifications, the design case 3 shows an energy consumption and TAC reduced by more than 20% than a literature reference case, thanks to smaller entrainer flow rate, a reduction of 32 trays and lower operating pressures. The best design is a trade-off between first a feasibility governed by thermodynamics through composition profiles and relative volatility maps and second process cost and energy demands

Étude sur les propriétés interfaciales de tensioactifs et de leurs interactions avec l'ADN

Ayant une partie hydrophile et une partie hydrophobe, les tensioactifs peuvent s'adsorber sur des interfaces et d'abaisser la tension interfaciale (g), ce qui améliore les propriétés interfaciales. Tensioactifs chargés sont également utilisés dans des applications biologiques, par exemple dans la livraison de gènes. Dans cette thèse, nous avons étudié les propriétés d'adsorption des tensioactifs, à la fois aux interfaces air/eau et sur l'ADN pour former des complexes.La première partie de la thèse se concentre sur les études d'interface de tensioactifs. Pour comprendre comment ils fonctionnent dans ces applications, il est important de connaître les échelles de temps de l'adsorption et la désorption de surfactant. Ainsi, il est nécessaire d'étudier l'adsorption et la cinétique de désorption, qui sont déjà largement étudié. Cependant, les études traditionnelles ont tendance à faire de nombreuses hypothèses, par exemple, l'extension de l'applicabilité des relations d'équilibre à des cas de non-équilibre. Dans cette mémoire, l'adsorption des deux systèmes tensioactifs différents a été étudiée, C12E6 de tensioactif non ionique et d'agent tensio-actif ionique CTAB avec suffisamment de sel. Une mesure de la compression de la bulle unique combiné avec une tension superficielle d'équilibre connue (geq) de valeur permet de déterminer g( ), ce qui est plus précis que les résultats des méthodes traditionnelles. Les concentrations de surface en fonction du temps sont mesurés, ce qui montre que l'adsorption est contrôlée par la diffusion à temps courts.Après avoir montré que l'adsorption est contrôlée par diffusion, nous rapportons la désorption des tensioactifs à partir de l'interface air/eau pour différents systèmes. Les processus de désorption sont confirmées pas être purement limitée par diffusion, indiquant la présence d'une barrière d'énergie. La barrière d'énergie est influencée par la longueur de la chaîne alkyle, et non le type de contre-ion.Dans la deuxième partie de la thèse, nous nous concentrons sur les systèmes d'ADN/tensioactif. Bien que l'interaction entre les tensioactifs cationiques et anioniques polyélectrolyte a été largement étudiée, il reste nécessaire de mieux comprendre le système complexe, en particulier pour rationaliser le choix des tensioactifs pour atteindre une capacité de liaison de l'ADN contrôlable et une faible toxicité pour l'organisme. Dans cette thèse, nous avons lancé l'enquête systématique sur les interactions des deux tensioactifs cationiques avec l'ADN.Le premier tensioactif utilisé est un gemini tensioactifs cationiques 12-2-12 2Br. Avant de l'utiliser avec l'ADN d'une caractérisation approfondie a été effectuée. L'équilibrage du 12-2-12 2Br sur une interface air/eau en l'absence d'électrolyte est très lent. Ajout de NaBr affecte peu la cinétique d'adsorption à des temps courts, pendant lesquels l'adsorption de diffusion. Cependant, l'adsorption s'équilibre beaucoup plus rapide. La formation de micelles de tensioactif cationique gemini 12-3-12 2Br a été étudiée. La concentration micellaire critique (CMC) augmente légèrement avec la température et diminue avec la force ionique. 12-3-12 2Br interagit fortement avec l'ADN, en raison de l'attraction électrostatique entre les deux et les interactions hydrophobes entre les chaînes alkyles. Sel écrans l'attraction électrostatique, tout en augmentant la longueur d'écartement des Gémeaux tensioactif affaiblit son interaction avec l'ADN.Un autre agent a également été étudié pour sa capacité de liaison à l'ADN et nous présentons une étude systématique sur les interactions entre tensioactif cationique liquide ionique [C12mim]Br et de l'ADN par des techniques expérimentales et de dynamique moléculaire (MD) de simulation. En ajoutant [C12mim]Br, les chaînes d'ADN sont soumis à compactage, des changements conformationnels, avec le changement de charge nette portée par le complexe ADN/tensioactif. simulation de MD confirme les résultats expérimentaux.Bearing a hydrophilic part and a hydrophobic part, surfactants can adsorb onto interfaces and lower the interfacial tension (g), thereby enhancing the interfacial properties and leading to the applications in cleaning, surface functionalization, foaming and emulsification. Charged surfactants are also used in biological applications, in particular to extract and purify DNA, or for gene delivery. In this thesis we have studied the adsorption properties of surfactants, both to air/water interfaces and onto DNA to form complexes. The first part of the thesis concentrates on interfacial studies of surfactants. To understand how they work in these applications it is important to know the time-scales of the surfactant adsorption and desorption. Thus it is necessary to investigate the adsorption and desorption kinetics, which are already widely studied. However, traditional studies tend to make many assumptions, for example, extending the applicability of equilibrium relations to non-equilibrium cases. In this dissertation, the adsorption of two different surfactant systems has been investigated, non-ionic surfactant C12E6 and ionic surfactant CTAB with sufficient salt. A single bubble compression measurement combined with a known equilibrium surface tension (geq) value allows the determination of g( ) , which is more accurate than results from traditional methods. The time-dependent surface concentrations are measured, showing that the adsorption is diffusion controlled at short times.Having shown that adsorption is diffusion controlled, we report desorption of surfactants from the air/water interface for different systems. The desorption processes are confirmed not to be purely diffusion-limited, showing the presence of an energy barrier. The energy barrier is influenced by the alkyl chain length, but not the counterion type.In the second part of the thesis we concentrate on DNA/surfactant systems. Although the interaction between cationic surfactant and anionic polyelectrolyte has been extensively studied, there still remains need to further understand the complex system, especially to rationalize the choice of surfactants to reach controllable DNA binding ability and low toxicity to the organism. In this dissertation, we introduced the systematic investigation on the interactions of two cationic surfactants with DNA.The first surfactant used is a cationic gemini surfactant 12-2-12 2Br. Before using it with DNA a thorough characterization has been carried out. The equilibration of 12-2-12 2Br onto an air/water interfaces in the absence of electrolyte is very slow. Addition of NaBr hardly affects the adsorption kinetics at short times, during which the adsorption is diffusive. However, the adsorption equilibrates much faster. The micellization of cationic gemini surfactant 12-3-12·2Br has been investigated. The critical micelle concentration (CMC) increases slightly with temperature and decreases with ionic strength. 12-3-12·2Br interacts strongly with DNA, due to the electrostatic attraction between the two and the hydrophobic interactions between alkyl chains. Salt screens the electrostatic attraction, while increasing spacer length of gemini surfactant weakens its interaction with DNA.Another surfactant has also been studied for its DNA binding ability and we present a systematic study on interactions between cationic ionic liquid surfactant [C12mim]Br and DNA by experimental techniques and Molecular Dynamics (MD) simulation. By adding [C12mim]Br, DNA chains undergo compaction, conformational changes, with the change of net charges carried by the DNA/surfactant complex. MD simulation confirms the experimental results.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF

First-principles computational investigation of nitrogen-doped carbon nanotubes as anode materials for lithium-ion and potassium-ion batteries.

Significant research efforts, mostly experimental, have been devoted to finding high-performance anode materials for lithium-ion and potassium-ion batteries; both graphitic carbon-based and carbon nanotube-based materials have been generating huge interest. Here, first-principles calculations are performed to investigate the possible effects of doping defects and the varying tube diameter of carbon nanotubes (CNTs) on their potential for battery applications. Both adsorption and migration of Li and K are studied for a range of pristine and nitrogen-doped CNTs, which are further compared with 2D graphene-based counterparts. We use detailed electronic structure analyses to reveal that different doping defects are advantageous for carbon nanotube-based and graphene-based models, as well as that curved CNT walls help facilitate the penetration of potassium through the doping defect while showing a negative effect on that of lithium

First-principles investigation of aluminum intercalation and diffusion in TiO2 materials: Anatase versus rutile

Aluminum-ion batteries, emerging as a promising post-lithium battery solution, have been a subject of increasing research interest. Yet, most existing aluminum-ion research has focused on electrode materials development and synthesis. There has been a lack of fundamental understanding of the electrode processes and thus theoretical guidelines for electrode materials selection and design. In this study, by using density functional theory, we for the first time report a first-principles investigation on the thermodynamic and kinetic properties of aluminum intercalation into two common TiO 2 polymorphs, i.e., anatase and rutile. After examining the aluminum intercalation sites, intercalation voltages, storage capacities and aluminum diffusion paths in both cases, we demonstrate that the stable aluminum intercalation site locates at the center of the O 6 octahedral for TiO 2 rutile and off center for TiO 2 anatase. The maximum achievable Al/Ti ratios for rutile and anatase are 0.34375 and 0.36111, respectively. Although rutile is found to have an aluminum storage capacity slightly higher than anatase, the theoretical specific energy of rutile can reach 20.90 Wh kg −1 , nearly twice as high as anatase (9.84 Wh kg −1 ). Moreover, the diffusion coefficient of aluminum ions in rutile is 10 −9 cm 2 s −1 , significantly higher than that in anatase (10 −20 cm 2 s −1 ). In this regard, TiO 2 rutile appears to be a better candidate than anatase as an electrode material for aluminum-ion batteries