An investigation of halogen induced improvement of ß12 borophene for Na/Li storage by density functional theory.

Pristine and halogen doped ß12 borophene, as anode of lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs), was considered by first-principles study based on density functional theory. Li and Na were adsorbed on ß12 borophene with adsorption energies of -3.18 eV and -2.33 eV, respectively. The effect of halogen addition, X = F, Cl, Br, and I, to borophene sheet on adsorption and also diffusion pathways of Li and Na was studied. The adsorption energy calculations show that the halogen atoms improve Li/Na adsorption on borophene sheet. Also, the results indicate that Li/Na adsorption energies on Brominated borophene sheet are higher compared to other halogen types. Diffusion calculations show that Br addition induces an electron deficiency on BoBr surface which lowers the energy barrier of migration of Li and Na ions compared to the pristine borophene. According to density of states analysis, electron charge is transferred from Li and Na atoms toward halogenated borophene sheet. Also, it can be concluded that electron transfer from Li/Na to borophene host in BoX is higher compared to pristine borophene which is in agreement with adsorption energies. The fully lithiated/sodiated complexes of BoBr are Li0.71BoBr and Na0.50BoBr which is equivalent to theoretical specific capacities of 1401 and 981 mAh/g which are about 3.5 and 2.6 times higher than graphite for Li and Na adsorption, respectively. Higher specific capacity of Li compared to Na is mainly attributed to steric hindrance of Na regarding its greater size. Open circuit voltage values of 1.6 V and 1.4 V were obtained for Li and Na intercalation processes, respectively, into halogen added ß12 borophene indicating that this structure can be applied as anode for both LIB and SIB systems.

Defective phosphorene as an anode material for high-performance Li-, Na-, and K-ion batteries: a first-principles study.

Single-layer phosphorene is a unique material with distinctive properties resulting in its high potential to be used as an anode in alkali metal ion batteries (AIBs). In this study, the improvement of the adsorption energy, the diffusion, and the storage capacity of alkali metals (Li, Na, and K) in a pristine and defective monolayer phosphorene was systematically studied using first-principles calculations. All possible defects on phosphorene were studied by electronic structure analysis. The pristine phosphorene strongly adsorbed Li, Na, and K with adsorption energies of -2.08 eV, -1.33 eV, and -2.16 eV, respectively. Interestingly, the presence of point defects significantly enhanced the binding of the alkali metals with adsorption energies in the range of 2.04-2.88 eV for Li, 1.05-2.72 eV for Na, and 2.16-3.05 eV for K. The diffusion of these alkali metals over pristine phosphorene was anisotropic, with an energy barrier of 0.1 eV for Li, 0.03 eV for Na, and 0.02 eV for K. More importantly, alkali metals could diffuse between two adjacent grooves in defective phosphorenes with a low energy barrier, which opens a novel channel for alkali metal diffusion. The lowest barrier energy (0.022 eV) was found for K atom in a single-vacancy defective structure, indicating faster migration and fast charge/discharge capability in KIBs. The theoretical Li and Na capacities on pristine phosphorene were calculated as 865 mA h g-1, which reached 882.5 mA h g-1 upon creating defects. An acceptable capacity (435 mA h g-1) was also obtained for K. Furthermore, phosphorenes have relatively low average open-circuit voltages when used as anode materials. These interesting properties indicate that the defective phosphorene has a great potential to be used as electrode material in AIBs, especially for KIBs.

Turning an environmental problem into an opportunity: potential use of biochar derived from a harmful marine biomass named Cladophora glomerata as anode electrode for Li-ion batteries.

The electrochemical performance of lithium ion battery was enhanced by using biochar derived from Cladophora glomerata (C. glomerata) as widespread green macroalgae in most areas of the Iran's Caspian sea coast. By the utilization of the structure of the biochar, micro-/macro-ordered porous carbon with olive-shaped structure was successfully achieved through pyrolysis at 500 °C, which is the optimal temperature for biofuel production, and was activated with HCl. The biochar and HCl treatment biochar (HTB) were applied as anode electrode in lithium ion batteries. Then, electrochemical measurements were conducted on the electrodes via galvanostatic charge-discharge, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) analyses. The electrochemical results indicated a higher specific discharge capacity (700 mAh g-1) and good cycling stability for HTB at the current density of 0.1 A g-1 as compared to the biochar. The reason that HTB electrode works better than the biochar could be due to the higher surface area, formation functional groups, removal impurities, and formation some micropores after HCl treatment. The biochar derived from marine biomass and treatment process developed here could provide a promising path for the low-cost, renewable, and environmentally friendly electrode materials. Graphical abstract Algal-biochar into Li-ion Battery.

Caseoperoxidase, mixed ß-casein-SDS-hemin-imidazole complex: a nano artificial enzyme.

A novel peroxidase-like artificial enzyme, named "caseoperoxidase", was biomimetically designed using a nano artificial amino acid apo-protein hydrophobic pocket. This four-component nano artificial enzyme containing heme-imidazole-ß-casein-SDS exhibited high activity growth and k(cat) performance toward the native horseradish peroxidase demonstrated by the steady state kinetics using UV-vis spectrophotometry. The hydrophobicity and secondary structure of the caseoperoxidase were studied by ANS fluorescence and circular dichroism spectroscopy. Camel ß-casein (Cß-casein) was selected as an appropriate apo-protein for the heme active site because of its innate flexibility and exalted hydrophobicity. This selection was confirmed by homology modeling method. Heme docking into the newly obtained Cß-casein structure indicated one heme was mainly incorporated with Cß-casein. The presence of a main electrostatic site for the active site in the Cß-casein was also confirmed by experimental methods through Wyman binding potential and isothermal titration calorimetry. The existence of Cß-casein protein in this biocatalyst lowered the suicide inactivation and provided a suitable protective role for the heme active-site. Additional experiments confirmed the retention of caseoperoxidase structure and function as an artificial enzyme.

Mixed micellization of gemini and conventional surfactant in aqueous solution: a lattice Monte Carlo simulation.

In the current study, we have investigated the micellization of pure gemini surfactants and a mixture of gemini and conventional surfactants using a 3D lattice Monte Carlo simulation method. For the pure gemini surfactant system, the effects of tail length on CMC and aggregation number were studied, and the simulation results were found to be in excellent agreement with the experimental results. For a mixture of gemini and conventional surfactants, variations in the mixed CMC, interaction parameter ß, and excess Gibbs free energy G(E) with composition revealed synergism in micelle formation. Simulation results were compared to estimations made using regular solution theory to determine the applicability of this theory for non-ideal mixed surfactant systems. A large discrepancy was observed between the behavior of parameters such as the activity coefficients fi and the excess Gibbs free energy G(E) and the expected behavior of these parameters as predicted by regular solution theory. Therefore, we have used the modified version of regular solution theory. This three parameter model contains two parameters in addition to the interaction parameters: the size parameter, ρ, which reflects differences in the size of components, and the packing parameter, P*, which reflects nonrandom mixing in mixed micelles. The proposed model provides a good description of the behavior of gemini and conventional surfactant mixtures. The results indicated that as the chain length of gemini surfactants in mixture is increased, the size parameter remains constant while the interaction and packing parameters increase.

Spontaneous formation of nanocubic particles and spherical vesicles in catanionic mixtures of ester-containing gemini surfactants and sodium dodecyl sulfate in the presence of electrolyte.

Self-assembly of pure ester-containing cationic gemini surfactants, dodecyl esterquat, and dodecyl betainate geminis, and cation-rich catanionic mixtures of them with sodium dodecyl sulfate (SDS) were investigated using surface tension, electrical conductivity, dynamic light scattering (DLS), transmission electron microscopy (TEM) and cyclic voltammetry (CV) measurements in the absence and presence of KCl. Different physicochemical properties such as the critical micelle concentration (CMC), degree of counterion dissociation (αdiss), interfacial properties, morphology of aggregates, and interparticle interaction parameters were determined. Both geminis formed micelles in the absence of KCl, and mixing with SDS did not change the morphology; just a growth in micelle size was observed. However, the aggregation behavior of these geminis with respect to the position of the ester bond in the alkyl chain appeared completely different in the presence of KCl. Esterquat gemini formed cubic nanoparticles (or cobosomes) in the presence of [KCl] = 0.05 M and transformed into spherical micelles upon increasing the surfactant concentration. By contrast, betainate gemini formed vesicles in the presence of [KCl] = 0.05 M and subsequently converted to micelles as the surfactant concentration increased. The morphology of esterquat gemini (in the presence of 0.05 M KCl) after mixing with SDS changed from cubic nanoparticles (or cobosomes) to cylindrical nanoparticles coexistent with cobosomes. Betainate gemini remained vesicular upon mixing with SDS, and no dramatic structural change of aggregates took place. The morphology changes of aggregates upon mixing with SDS were explained from calculating the interactions between two gemini surfactants and SDS on the basis of regular solution theory.

Monte Carlo simulation of binary surfactant/contaminant/water systems.

Surfactant-enhanced remediation (SER) is an effective approach for the removal of absorbed hydrophobic organic compounds (HOCs) from contaminated soils. The solubilization of contaminants by mixed surfactants with attractive and repulsive head-head interactions was studied by measuring the micelle-water partition coefficient (K(C)) and molar solubilization ratio (MSR) using the lattice Monte Carlo method. The effect of surfactant mixing on the MSR and K(C) of contaminants displayed the following trend: C4 > C3 > C2. Synergistic binary surfactant mixtures showed greater solubilization capacities for contaminants than the corresponding individual surfactants. Mixed micellization parameters, including the interaction parameter ß, and activity coefficient f(i), were evaluated with Rubingh's approach. Synergistic mixed-surfactant systems can improve the performance of surfactant-enhanced remediation of soils and groundwater by decreasing the amount of applied surfactant and the cost of remediation.

Comprehensive study of tartrazine/cationic surfactant interaction.

Interaction of a food dye, tartrazine, with some cationic conventional and gemini surfactants, tetradecyltrimethylammonium bromide (TTAB), N,N'-ditetradecyl-N,N,N',N'-tetramethyl-N,N'-butanediyl-diammonium dibromide (14,4,14), and N,N'-didodecyl-N,N,N',N'-tetramethyl-N,N'-butanediyl-diammonium dibromide (12,4,12), were first investigated comprehensively employing conductometry, tensiometry, and UV-visible spectroscopy. Tartrazine was found to behave in the same manner as aromatic counterions. The formation of ion pairs reflected as a considerable increase of the surfactant efficiency in tensiometry plots and their stoichiometry were determined by Job's method of continuous variations. For the tartrazine/TTAB system, nonionic DS(3), ionic DS(2-), and/or DS(2)(-) ion pairs, their small premicelles, and tartrazine-rich micelles were constituted as well as dye-containing TTAB-rich micelles. Insoluble J-aggregates of DS(-) ion pairs and cylindrical surfactant-rich micelles were also formed in tartrazine/gemini surfactant systems and recognized by transmission electron microscopy. The zeta potential and the size of the aggregates were determined using dynamic light scattering and confirmed the suggested models for the processes happening in each system. Cyclic voltammetry was applied successfully to track all of these species using tartrazine's own reduction peak current for the first time.

Cosolvent effects on the spontaneous formation of nanorod vesicles in catanionic mixtures in the rich cationic region.

The aggregation behavior of cation-rich catanionic mixtures of cetyltrimethyl ammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) was investigated in water-ethylene glycol (EG) solutions by performing surface tension, electrical conductivity, pulsed field gradient nuclear magnetic resonance, transmission electron microscopy, and cyclic voltammetry measurements. Different physicochemical properties such as the critical micelle concentration, degree of counterion dissociation (α), interfacial properties, aggregation numbers, morphology of aggregates, and interparticle interaction parameters were determined. Cosolvent effects on the interactions between the two surfactants CTAB and SDS were analyzed on the basis of regular solution theory, both for mixed monolayers at the air/liquid interface (ß(δ)) and for mixed micelles. It was shown that an excess of cationic surfactant resulted in the formation of nonspherical vesicles. These were predominantly nanorod vesicles in water-EG mixed solvents. The interparticle interactions were assessed in terms of cosolvent effects on the micellar surface charge density, the sphere-to-rod morphology change, and the phase transition from vesicles to mixed micelles. Moreover, the variation of the repulsive electrostatic potential energy between two pairs of aggregates was investigated for two modes of nanostructural transition, namely the transition between spherical and rod-like micelles and the transition between rod-like micelles and nanorod vesicles.

Vesicular mixed gemini-SDS-hemin-imidazole complex as a peroxidase-like nano artificial enzyme.

A biomimetic was designed for the construction of a new efficient peroxidase-like nano artificial enzyme with a heme-imidazole component complexed with gemini 12-2-12/SDS supramolecules. The presence of a simple surfactant mixture (SDS/gemini 12-2-12 at a particular concentration) provided an apoprotein-like hydrophobic pocket for the heme-imidazole moiety, which produced a peroxidase active site containing positive and negative charges distributed on the colloidal surface. Vesicular structures that stabilized the heme-imidazole complexes formed multienzyme advanced colloids. The enzymatic activation parameters indicated that the catalytic efficiency of the novel nano artificial enzyme was 27% as efficient as the native horseradish peroxidase (HRP). The imidazole moiety, which functionally corresponded to the histidine ligand in the native HRP, increased the reactivity and catalytic efficiency of the artificial enzyme. The nano biocatalyst did not exhibit suicide inactivation until high concentrations of hydrogen peroxide, indicating that the vesicle hydrophobic pocket effectively shielded the active site, thereby controlling the concentration of hydrogen peroxide at the heme moiety and enabling high rates of enzymatic turnover.

Molecular interactions of cationic and anionic surfactants in mixed monolayers and aggregates.

The properties of anionic-rich and cationic-rich mixtures of CTAB (cetyltrimethylammonium bromide) and SDS (sodium dodecyl sulfate) were investigated with conductometry and surface tension measurements and by determining the surfactant NMR self-diffusion coefficients. The critical aggregate concentration (CAC), surface tension reduction effectiveness(gamma(CAC)), surface excess(Gamma(max)), and mean molecular surface area (A(min)) were determined from plots of the surface tension (gamma) as a function of the total surfactant concentration. The compositions of the adsorbed films (Z) and aggregates (chi) were estimated by using regular solution theory, and then the interaction parameters in the aggregates (beta) and the adsorbed film phases (beta(sigma)) were calculated. The results showed that the synergism between the surfactants enhances the formation of mixed aggregates and reduces the surface tension. Further, the nature and strength of the interaction between the surfactants in the mixtures were obtained by calculating the values of the following parameters: the interaction parameter, beta, the size parameter, rho, and the nonrandom mixing parameter, P*. These results indicate that in ionic surfactant mixtures the optimized packing parameter has the highest value and that the size parameter can be used to account for deviations from the predictions of regular solution theory. It was concluded that, for planar air/aqueous interfaces and aggregation systems, this nonideality increases as the temperature increases. This trend is attributed to the increased dehydration of the surfactant head groups that results from increases in temperature. Further, our conductometry measurements show that the counterion binding number of mixed micelles formed in mixtures with a high CTAB content is different to those with a high SDS content. This difference is due to either their different aggregation sizes or the different interactions between the head groups and the counterions.

Electrolyte effect on mixed micelle and interfacial properties of binary mixtures of cationic and nonionic surfactants.

In the present work, the adsorption behavior at the liquid-air interface and micellization characteristics of mixtures of cetyltrimethylammonium bromide (CTAB) and p-(1,1,3,3-tetramethylbutyl) polyoxyethylene (TritonX-100) in aqueous media containing different concentrations of NaBr were investigated by surface tension and potentiometry measurements. From plots of surface tension (gamma) as a function of solution composition and total surfactant concentration, we determined the critical micelle concentration (CMC), minimum surface tension at the CMC (gamma(CMC)), surface excess (Gamma(max)), and mean molecular surface area (A(min)). On the basis of regular solution theory, the compositions of the adsorbed film (Z) and micelles (X(M)) were estimated, and then the interaction parameters in the micelles (beta(M)) and in the adsorbed film phase (beta(sigma)) were calculated. For all mole fraction ratios, the results showed synergistically enhanced ability to form mixed micelles as well as surface tension reduction. Furthermore beta was calculated by considering nonrandom mixing and head group size effects. It was observed that, for both the planar air/aqueous interface and micellar systems, the nonideality decreased as the amount of electrolyte in the aqueous medium was increased. This was attributed to a decrease of the surface charge density caused by increasing the concentration of bromide ions.

A new model to study the phase transition from microstructures to nanostructures in ionic/ionic surfactants mixture.

The phase behavior and aggregate structures of mixtures of the oppositely charged surfactants cetyltrimethyl ammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) are explored at high dilution by pulsed field gradient stimulated echo (PFG-STE) NMR. The aggregation numbers and hydrodynamic radii of vesicles and mixed micelles were determined by a combination of viscosity and self-diffusion coefficient measurements. The average size of the mixed micelles was larger than that of micelles containing uniformly charged head groups. Analysis of the variations of the self-diffusion coefficient and viscosity with changing concentration of CTAB or SDS in the cationic-rich and anionic-rich regions revealed a phase transition from vesicles to mixed micelles. Differences in the lengths of the CTAB and SDS hydrophobic chains stabilize vesicles relative to other microstructures (e.g., liquid crystalline and precipitate phase), and vesicles form spontaneously over a wide range of compositions in both cationic-rich and anionic-rich solutions. The results obtained from conductometry measurements confirmed this transition. Finally, according to the capacitor model, a new model was developed for estimating the surface potentials and electrostatic free energy (g(elec)). Then we investigated the variations of electrostatic and transfer free energy in phase transition between mixed micelle and vesicle.

Complexation between a macromolecule and an amphiphile by Monte Carlo technique.

Using a simple modified version of Larson's model, we studied the complexation between a macromolecule and an amphiphile in a dilute range of concentrations. The main characteristic of amphiphile molecules, that is, the hydrophobicity of the tails and hydrophilicity of the heads, is used to model the self-assembling process. Contrary to the molecular thermodynamics approaches, no prior shape was considered for the aggregates and the system was allowed to choose the most stable structure. For true ensemble averaging, without any synthetic results, configurational bias Monte Carlo and reptation moves are used to produce a Markov chain of configurations. From the results, it is found that the macromolecule causes the clusters of surfactants to be formed at a concentration much lower than the critical micelle concentration. Furthermore, the shape of the clusters tends to be more spherical, which is in line with theory and experiments. From the results, it is learned how a polymer can change the behavior of an amphiphilic molecule. All of the results are in good qualitative agreement with experimental and molecular thermodynamics results. Furthermore, the model predicts network formation between bound clusters at high concentrations of the surfactant.